1 COMMUNITY ECOLOGY OF CREEK DWELLING FRESHWATER TURTLES AT NOKUSE PLANTATION, FLORIDA By BENJAMIN K. ATKINSON A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENT S FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2009
2 2009 Benjamin K. Atkinson
3 for Thad Owens: a friend beyond description (1981 2009)
4 ACKNOWLEDGEMENTS I am indebted to my advisory committee: Drs. Max Nickerson (University of Florida (UF)/Florida Museum of Natural History (FLMNH)), James Perran Ross (UF Dept. of Wildlife Ecology & Conservation (WEC)), and Kelly Chinners Reiss (UF Dept. of Environmental Engineering Sciences) for overseeing my r esearch and providing invaluable supplies and mentorship. For logistical support and opportunity I am grateful to Drs. Matt Aresco and Margaret Gunzburger, and Mr. M.C. Davis (Nokuse Plantation). Dr. Katie Sieving (WEC) was instrumental in the research des ign. I thank Nokuse Plantation staff members Bob Walker, Frank Cuchens, and Don Graff for field and technical support. Dr. Peter Pritchard (Chelonian Research Institute), Herb von Kluge (Brooksville Development), George Heinrich (Heinrich Ecological Servic es), Eric Pedersen (Butler County Community College), Ralphie Scherder (Scherder Taxidermy), and Tim Walsh (Orlando Science Center) provided encouragement and/or field gear. Jason Butler (WEC) was a much appreciated comrade and field assistant. My parents donated an essential canoe. My grandmother, MaryAnn never ceases to support my academic and career endeavors. Choctawhatchee Basin Alliance and FL Dept. of Environmental Protection LAKEWATCH made water quality sampling and analyses possible. Reptile and Am phibian Conservation Corps (RACC) provided hoop nets, calipers, scales, and tags. Research was conducted under FWC scientific collecting permit #WV08218 and UF Animal Research Committee protocol #004 08WEC. Cathy Bester (FLMNH) was very helpful with image preparation during revision of the manuscript. Finally, I thank Meaghan Bernier for assistance in the field and laboratory, patience during the process, and most of all for genuinely believing in m e.
5 TABLE OF CONTENTS page ACKNOWLEDGEMENTS ..4 LIST OF TABLES LIST OF FIGURES..8 LIST OF ABBREVIATIONS......................................................................................9 ABSTRACT CHAPTER 1 INTRODUCTION................... Freshwater Turtle Diversity and Conservation Ecology.................................12 Environmental Factors and Freshwater Turtle Communities..........................17 Chelonian Life Histori es..................................................................................22 Environmental Factors and Freshwater Fish Communities.............................24 Site Overview...................................................................... .............................26 2 MATERIALS AND METHODS.....36 Freshwater Turtle Community Sampling.........................................................36 Mark R ecapture............................................................... .................................37 Morphometrics.................................................................................................39 Musk Turtle Dietary Sampling.........................................................................39 Water Quality Monitoring................................................................................41 3 RESULTS ....................................45 Species Richness and Biodiversity............................................... ....................45 Musk Turtle Dietary Analyses..........................................................................47 Water Quality Analyses....................................................................................48 4 DISCUSSION .....................................59 Community Types............................................................................................59 Blackwater Cypress Dominated Communities................................................60 Up land Moderate Flow Communities...............................................................62 Primary Productivity and Turtle Density..........................................................64 Diet........................................................ ............................................................65 LIST OF REFERENCES...........72
6 BIOGRAPHICAL SKETCH..........79
7 LIST OF TABLES Table Page 3 1 Relative abundance of ve rtebrates captured by trapping at Nokuse Plantation...51 3 2 Species richness, Shannon diversity, community evenness, and statistically different mean primary productivity and oxygen saturation values for all study creeks................................. ...................................................................................57 3 3 Water quality parameters with statistically insignificant differences between study creeks.............................................................................. ............................58
8 LIST OF FIGURES Figure Page 1 1 Florida map with Walton County highlighted.......................................... 29 1 2 Conservation lands in the Florida panhandle.............................. ..............30 1 3 Map depicting the creeks studied at Nokuse Plantation and the Choctawhatchee River, Walton Co., FL. .................................... 31 1 4 Dismal Creek, Walton Co., FL................................................................. .32 1 5 Big Cypress Creek, Walton Co., FL..........................................................33 1 6 Black Creek, Walton Co., FL....................................................................34 1 7 Seven Runs Creek, Walton Co., FL ............. .............................................. 35 2 1 The author securing a hoop net to capture turtles in Big Cypress Creek..................................................................................43 2 2 Nokuse Plantation carapace notching sche matic........................................44 3 1 Turtle species richness of trap samples.......................................................52 3 2 Sternotherus minor size class distribution..................................................53 3 3 S ternotherus odoratus size class distribution.............................................54 3 4 Sternotherus minor and Sternotherus odoratus dietary averages by creek ...........................................................................55 3 5 Tota l phosphorus, chlorophyll, and percent oxygen saturation compared means per creek.........................................................................56
9 LIST OF ABBREVIATIONS AmbAri: Ambloplites ariommus [Viosca, 1936], shadow bass AmeNat: Amei urus natalis [Lesueur, 1819], yellow bullhead AmpMea: Amphiuma means [Garden, 1821], two toed amphiuma CheSer: Chelydra serpentina [Linnaeus, 1758], snapping turtle EsoNig: Esox niger [Lesueur, 1818], chain pickerel LepGul: Lepomis gulosus [Cuvier, 182 9], warmouth bass LepMac: Lepomis macrochirus [Rafinesque, 1819], bluegill LepMic: Lepomis microlophus [Gnther, 1859], redear sunfish LepMin: Lepomis miniatus [Jordan, 1877], redspotted sunfish RanCat: Rana catesbeiana [Shaw, 1802], American bullfrog SteMin: Sternotherus minor [Agassiz, 1857], loggerhead musk turtle SteOdo: Sternotherus odoratus [Latreille, 1801], stinkpot TraScr: Trachemys scripta [Schoepff, 1792], yellow bellied slider
10 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science COMMUNITY ECOLOGY OF CREEK DWELLING FRESHWATER TURTLES AT NOKUSE PLANTATION, FLORIDA By Benjamin K. Atkinson August 2009 Chair: Max Al len Nickerson Cochair: James Perran Ross Major: Interdisciplinary Ecology Freshwater turtle communities were surveyed in four creeks at Nokuse Plantation. Nokuse Plantation is a 21,000 hectare private conservation tract in the Florida panhandle. The gre ater region, eastward to the Apalachicola River drainage and westward to Mobile Bay hosts the richest diversity of turtles in the United States. Sampling was conducted using baited hoop nets, modified crayfish traps, and hand capture in Dismal Creek, Big C ypress Creek, Black Creek, and Seven Runs Creek. Turtles were identified to species; demographic and morphometric data were recorded. Specimens were marked for recapture. Water quality parameters were measured and other trapped organisms were also identifi ed and counted. Two generalized community types were discernable from analysis of water quality and trapping data. Dismal Creek and Big Cypress Creek are slow moving floodplain swamp fed blackwater creeks with relatively high levels of detritus accumulatio n and corresponding high levels of primary productivity, as measured by total phosphorus and chlorophyll content They are also characterized by relatively low oxygen concentrations in the water column. Dismal Creek and Big Cypress Creek share high total s pecies richness and evenness. Dismal Creek has more canopy cover but
11 less basking sites than Big Cypress Creek. Black Creek and Seven Runs Creek are more upland communities than Dismal Creek and Big Cypress Creek, with lower primary productivity levels, hi gher flow, and higher water column oxygen content. Black Creek is a blackwater stream with heavy canopy cover, moderate current, a sand bottom, and is fed in part by seepage. Black Creek drains into Choctawhatchee Bay. Seven Runs Creek is a sand bottomed s eepage stream fed by numerous steepheads. Seven Runs Creek has moderate canopy cover, the lowest levels of primary productivity, the greatest flow and highest oxygen content in the water column of the creeks studied. Omnivorous turtle species richness diff ered by creek. Sternotherus minor were trapped in all four study areas. Dismal Creek contains S. minor Sternotherus odoratus Trachemys scripta, and Chelydra serpentina. Big Cypress Creek has three species: S. minor S. odoratus and T. scripta Black Cr eek trapping efforts captured S. minor and a single T. scripta Only S. minor was observed in Seven Runs Creek. S. minor and S. odoratus diets were analyzed by collecting fecal samples from trapped turtles. Diets differed between creeks, with greater diver sity of food items being consumed in creeks with higher primary productivity. Primary productivity is positively correlated with relative abundance and diversity of turtles, and total species richness of the creek communities studied.
12 CHAPTER 1 INTR ODUCTION Reptile and amphibian faunas are diminishing at an alarming rate throughout the world (Gibbons et al. 2000, Zug et al. 2001, Pough et al. 2002). Reasons for decline are varied across regions and taxa and include over harvest, habitat loss, and a lteration of habitat quality due to anthropogenic effects. Research often focuses on high profile species despite pressures affecting even common reptiles and amphibians (Dodd et al. 2007). One of the greatest problems conservationists face at this criti cal time is a lack of population and community data (Jackson 2005, Meylan 2006). Freshwater Turtle Diversity and Conservation Ecology Of approximately 300 chelonian species known globally, over 90% are freshwater or terrestrial taxa (Klemens 2000, Moll a nd Moll 2004). Taxonomists generally recognize seven species of marine turtles and the majority of research and funds are devoted to these species (Moll and Moll 2004), yet most chelonians are imperiled. Florida species are at particular risk because of a high rate of human immigration and development. The state is home to nearly half of the countrys turtle diversity: 25 of the United States 54 chelonian species naturally occur in Florida (Iverson and Etchberger 1989, Meylan 2006). Freshwater turtles a re dominant features of many aquatic ecosystems and can comprise the majority of vertebrate biomass in lakes, ponds, rivers, and streams (Iverson 1982, Congdon et al. 1986). The complexities of chelonian ecological roles are only starting to be understood : as seed dispersers and vehicles for energy and nutrient flow (Moll and Moll 2004), and in terms of food web dynamics (Aresco 2005).
13 Riverine turtles have been influenced by many anthropogenic effects most notably habitat degradation, unsustainable har vest, and subsidized predator bases (Moll and Moll 2004, Jackson 2005). Academic interest in freshwater turtles has a rich history with roots in seminal works by Louis Agassiz (1857), Clifford Pope (1939), Archie Carr (1952) and others. Yet general data r egarding conservation status and habitat needs for most species and regions are lacking (Moll and Moll 2004, Jackson 2005). Determining abiotic and biotic factors that influence freshwater turtle community structure will allow more effective management (Bo die 2001). Conner et al. (2005) offer insight regarding ecological effects of human altered habitats for turtles and the conservation implications. Their study took place in an urbanized part of Indiana where road mortality, loss of nesting sites to lawn and parking lot conversion, and direct harvest by fisherman and hobbyists were contributing to an apparent decline of the turtle species in man made canals. Their study area was created 160 years prior to the investigation but no rigorous sampling of the t urtle community had ever been conducted. No baseline data exist for the site only generalized observational reports were available for comparison to the modern assemblage condition. Another Indiana turtle assemblage study (Smith et al. 2006) took place i n a more natural setting being encroached by boat traffic and habitat alteration Smith et al. (2006) detail the situation in Dewart Lake near Syracuse, Indiana where they have monitored the lake for more than 20 years. They documented boat propellers as a significant threat to painted turtles and note that seawalls and increased boat traffic may be responsible for downward trends in turtle populations, especially of painted turtles (due to fewer nesting and basking sites, in addition to direct impacts by boats).
14 Dreslik et al. (2005) report on a diverse Illinois turtle assemblage comprised of 10 species of freshwater chelonians with members representing four families. They stressed the importance of repeated sampling and noted species richness increased as a function of trap hours, with 3000 trap hours required to capture all species. They went on to comment this suggests that intense sampling is required to effectively sample most turtle communities. However, Round Pond is a relatively large ( 30 ha) open body of water; smaller ponds, marshes, and swamps undoubtedly would require fewer trap hours. Stone et al. (1993) document temporal changes in two turtle assemblages in Alabama. They studied two turtle assemblages in adjacent man made farm ponds in east central Alabama at Auburn University. The pond was stocked with Micropterus salmoides largemouth bass, Lepomis macrochirus bluegill, and L. microlophus, redear sunfish. Their first study period was conducted from 1972 1974 and then they revisited th e site from 1988 1990. Turtles were surveyed using pitfall traps and funnel traps. Stone et al. (1993) recaptured mud turtles ( Kinosternon subrubrum ) that were marked as adults nearly 15 years later, suggesting longevity and indicating high mud turtle surv ivorship within the system. The ponds received different levels of fertilizers and underwent differential vegetational succession rates. The assemblages showed minor changes most notably an increase in S. odoratus in both ponds and a decrease in Chelydra serpentina in one of the ponds. Stone et al. (1993) linked the turtle community changes to the agricultural practices, colonization rates, and succession. Moore and Seigel (2006) stressed the need for safe basking and nesting sites along the Pascagoula R iver for federally threatened Graptemys flavimaculata yellow
15 blotched map turtles. Boat traffic in southeastern Mississippi altered G. flavimaculata nesting and basking behavior by scaring females as they approach nest sites and lowered body temperatures. Boat traffic coupled with deadwood removal, which reduces basking sites, appears to be causing a decline in the population with fewer clutches being laid. Meylan et al. (1992) described the freshwater turtle community of the Rainbow River in Marion Count y, Florida. This report was the first to document changes in a Florida riverine chelonian community occurring over the course of several decades. No similar papers have been published. Their survey results contrast with those reported fifty years earlier b y Marchand (1942), indicating significant alteration of the community composition. Meylan et al. (1992) report on the size and structure of populations of Sternotherus minor loggerhead musk turtles and S. odoratus, stinkpots in addition to documenting the general turtle assemblage structure of Rainbow River. When Marchand published his survey (1942) S. minor was not observed. Both studies were conducted by snorkeling to hand capture turtles. Fifty years later when Meylan et al. revisited the site S. minor had become the document species of chelonian, representing 66.2% of the community composition in 1990. Dramatic declines in the presence of Pseudemys spp. (cooters) occurred during the same timeframe. Heinrich et al. (in press) document continued harvest of Pseudemys particularly large adult females for human consumption. The individuals responsible for one dump pile reputedly caught cooters in Rainbow River (George Heinrich, pers. comm.). Huestis and Meylan (2004) described an increase in the relative ab undance and total number of Pseudemys spp. in Rainbow River since Meylan et al. (1992) and note
16 that this could be the result of intensified vigilance by the law enforcement officials as well as a fading interest in turtle harvesting. Moll (1990) studied a freshwater turtle population in a s low moving stream in Belize and documented relative abundance, population estimates, and dietary trends in four freshwater turtles inhabiting his study site. These species were T. scripta (a species encountered in moder ate numbers in my study), and three species that do not range into the United States but have similar morphology and ecological habits to the kinosternids and chelydrid from my study. He sampled by baited hoop nets (using canned sardines) trammel nets, sno rkeling, and muddling a term he explained means groping for turtles buried in stream bottom substrates. Moll found Kinosternon scorpioides, scorpion mud turtles, K. leucostomum white lipped mud turtles, and Staurotypus triporcatus, Mexican giant mu sk turtles in descending relative abundance. He noted species densities were relative to time of year (due in part to seasonal drying of ephemeral wetlands) and diet was correlated to seasonal relative abundance of the species presence in the stream ( Staur otypus eats Kinosternon ). Molls dietary analyses were conducted by stomach flushing according to Legler (1977). The previous section focused primarily on studies garnering demographic and community ecology data on freshwater turtles in a number of locat ions and regions. They provide a basis for inquiry regarding habitat needs, baseline community structure, dietary analyses, and for refinement of sampling methodologies (e.g. trap hours required to detect all turtle species in a study system). Several stud ies have addressed environmental factors that directly affect freshwater turtle population dynamics ; Scott and Campbell (1982) provided a review of pre 1980s reptile community reports. I review more recent
17 studies that detail environmental factors and the ir influence on freshwater turtle communities in the following section. Environmental Factors and Freshwater Turtle Communities Several important factors repeatedly emerge as important in structuring turtle communities. In studies focused on varied taxa ac ross large geographic expanses, some pertinent trends appear to consistently affect chelonian assemblages. Particularly relevant anthropogenic affects include habitat degradation (Stone et al. 1993, Reese and Welsh 1998, Lindeman 1999, Marchand and Litvait is 2004, Moore and Seigel 2006, Rizkalla and Swihart 2006, and Smith et al. 2006), harvest (Meylan et al ., 1992, Heinrich et al ., in press), predation (Congdon et al. 1993, Congdon et al. 1994, Browne and Hecnar 2007), and boat and/ or vehicular traffic (M archand and Litvaitis 2004, Smith et al. 2006, and Browne and Hecnar 2007). Environmental factors that have been demonstrated as crucial for turtle populations that may be natural in origin, as well as human influenced, and include basking site availabili ty (DonnerWright et al. 1999, Lindeman 1999, Moore and Seigel 2006), forest cover in buffer zones surrounding aquatic habitats (Marchand and Litvaitis 2004), and local hydrology (Bodie and Semlitsch 2000, Bodie et al. 2000). Emydoidea blandingii Blanding s turtles have declined and Clemmys guttata have been extirpated in Point Pelee National Park, Ontario despite protection of the habitat ( Browne and Hecnar 2007). Demographics of E. blandingii and C. serpentina have shifted toward older animals and are mo re male skewed. Procyon lotor, raccoons are believed responsible for much of the change due to predation on nests, juveniles, and nesting females. C. picta appears to be the only stable species in the turtle assemblage at
18 present. Other threats facing the turtle community in the national park include habitat fragmentation (resulting in road mortality), ecological succession of plant communities, and possibly pollution. An earlier study was conducted in 1984 and 1985 in other parts of Ontario, Canada, on th e density and biomass of Chelydra serpentina snapping turtles. Galbraith et al. (1988) found that primary productivity was the most important environmental facet involved in structuring snapping turtle populations. This positive correlation is due in part to the fact that snapping turtles eat plants, invertebrates, and vertebrate animals, which are directly affected by the level of primary productivity in their aquatic ecosystems. DonnerWright et al. (1999) studied the turtle assemblage of the St. Croix Ri ver in Minnesota and Wisconsin. This study stressed the need for large scale ecosystem research, rather than single species approaches. This fundamental change of focus appears to be gaining momentum, as ecology is increasingly interdisciplinary in nature. The authors had the rare opportunity to study a 100 km stretch of the river expanding the scope and level of inference farther yet. The river has been protected since 1968 an attribute to their study that allows an informed picture of a relatively undis turbed habitat. DonnerWright et al. (1999) found that the species responded differently to various geomorphic changes along environmental gradients (channel morphology and other physical characteristics of the river). Populations of Chrysemys picta pai nted turtles, and C. serpentina snapping turtles, were positively correlated with the presence of mucky substrate, number of basking sites, and river width. Graptemys pseudogeographica false map turtles were positively correlated to muck, stream bank slo pe and latitude. Apalone spinifera, spiny softshells, were positively related to water depth and velocity. Graptemys
19 geographica common map turtles, showed no significant relationship to any measured environmental variables. Joyal et al. (2001), studied Clemmys guttata spotted turtles and Emydoidea blandingii Blandings turtles in Maine. They used mark recapture, re sighting, and radio telemetry to follow turtles movements across wetland matrixes and quantify habitat usages. They determined that both s pecies require multiple habitat types of varying aquatic and terrestrial genres, by season, year, species, and individual (partially dependent on gender for nesting forays, etc). The management implications of their findings shed light on the need to p rotect substantial buffer zones around wetlands and also revealed the importance of small, isolated wetlands to turtles on a seasonal basis. Marchand and Litvaitis (2004) studied painted turtles along an urbanization gradient in New Hampshire. They present ed painted turtle demographics in relation to level of urbanization in 37 ponds. They baited wire funnel traps with cat food and also captured C. serpentina C. guttata and S. odoratus. O nly C. picta data were compared to environmental variables since mor e than ninety percent of captured chelonians were painted turtles a decision that limits the scope of inference. Trapping intensity was not consistent; the authors claimed complicating factors were unfavorably lowered levels in water, and the disappearan ce of bait and traps. Marchand and Litvaitis also conducted 1 hr searches by canoe with dip nets to capture turtles in their (2004) study. Aquatic vegetation was quantified using 85 cm circular hoop plots to determine percent cover. This study drew a few valuable conclusions; they determined that habitat features described at several spatial scales apparently influenced the demography of painted turtles due to female mortality on
20 nesting forays (cars, predators, and lawn mowers), and that forest cover su rrounding ponds resulted in higher numbers of males due to the mechanics of temperature dependent sex determination, or TSD (Ewert and Nelson 1991). The egg temperature determines most chelonian and crocodilian species genders while an embryo is forming (Ewert and Nelson 1991). In many turtles higher incubation temperatures produce females and lower temperatures produce males. Ewert and Nelson (1991) reported that 100% of the Pseudemys floridana eggs incubated at 25 degrees C in their study resulted in m ales, and 100% of the eggs incubated at 30 degrees C resulted in female turtles. In other turtle species females are produced at both very high and very low temperatures, with males being produced by a middle thermal range. Changes in substrate temperature s, whether natural (e.g. more sun exposure from treefall) or due to habitat alteration could cause changes in sex ratios that would ultimately change demographics. Such changes can have repercussions to population sustainability. Not all turtle species use TSD some species genders are determined genetically. Reese and Welsh (1998) showed responses of western pond turtles in the Trinity River Basin, California to damming and temperature/ basking sites associated with habitat alteration. Damming created d eeper water, but increased canopy cover and lowered water temperatures making basking more necessary (but more difficult) than the warm water un dammed areas. Bodie et al. (2000), used helicopters to survey wetlands from 1996 1998 over a 296 km section of the Missouri River floodplain. They classified wetlands according to a variety of land use and natural categories. Abiotic factors measured by Bodie et al.
21 (2000) were surface area (from aerial photographs) and turbidity (by hand collected samples). Turtl es were trapped using multiple alternating trap styles and baits. Primary productivity was measured in terms of chlorophyll concentration (micrograms per liter). Secondary productivity was measured by aquatic insect trapping. They compared environmental v ariables to turtle species richness per site and used Simpsons Index to measure evenness of species abundance. Bodie et al. (2000) found that the single most important characteristic of these wetlands for turtle diversity was a low annual duration of dry ing. Rizkalla and Swihart (2006) found that turtle species respond differently to landscape modification and that agriculture affects some species more than others. They studied 35 randomly selected 23 square km cells the upper Wabash River basin of Ind iana. They used baited hoop nets (creamed corn or canned sardines) to sample the turtle assemblages and documented a total of eight different turtle species across the wetlands surveyed. They counted woody stems and percentage cover for herbaceous species along transects at each sampling site. As seen in some of the aforementioned studies, species showed variable responses to the environmental variables measured. Lindeman (1999) documented the importance of deadwood for basking of map turtles ( G. flavimac ulata Graptemys oculifera ringed map turtles, Graptemys ouachitensis Ouachita map turtles, Graptemys gibbonsi Pascagoula map turtles, and Graptemys pseudogeographica kohnii Mississippi map turtles) in three river drainages: the Tennessee, Pearl, and P ascagoula Rivers. He used high powered spotting scopes to survey basking site availability and densities of turtles utilizing deadwood. Graptemys
22 spp. are more sensitive than many other species to basking site availability; some species are rarely observed basking aerially. The effects of coal mining have been studied as an isolating mechanism for Sternotherus depressus, flattened musk turtles populations have been investigated in the Warrior River Basin, Alabama (Dodd 1990). Strip mining for coal led to s erious habitat degradation through siltation. Impoundments and direct pollution including non point source agricultural inputs and sewage effluent have also created un desirable habitat. The siltation eliminates microhabitat refugia for the turtles and als o makes the environment inhospitable to primary food items, especially freshwater mollusks (Dodd 1990). Chelonian Life Histories Chelonian life histories have been documented for many species ( e.g. Trachemys scripta by Gibbons (1990). Most turtles are be lieved to have life spans exceeding 30 years (Gibbons 1987); some are known to live for a century (e.g. Terrapene carolina ) and some individuals ( Geochelone sp. ) have been reputed to exceed 150 years (Pritchard 1979). Longevity is necessary to conservative chelonian life history, as turtles have variable but low reproductive success (Congdon et al. 1993) and exhibit a mixture of K and R selected traits. K selected organisms (like elephants and humans) have long lives and produce few offspring, for which th ey invest a lot of energy and time in parental duties. R selected organisms usually have relatively short lifespans but produce far more offspring in which little or no parental care is involved and the survivorship of offspring is much lower. Turtles and tortoises have lifespans that are among the longest known of all
23 vertebrates, but produce many offspring over the course of their reproductive life for which they offer no parental care and for whom survivorship is poor (Klemens 2000). Studies of long li ved organisms can require long term monitoring to gain meaningful insight (Congdon and Gibbons 1996). Congdon et al. (1993) found a 37 yr generation time for Blandings turtles and noted that increased predation pressures have resulted in an even greater d emand for survivorship of juveniles. The life history table that Congdon and colleagues produced would not have been possible without a long running population study that depended on marking and recapturing turtles. Congdon et al. (1994) found similar pat terns and conservation needs in Chelydra serpentina snapping turtles. They also made clear that protection of nests and/or head starting would not be enough to adequately protect snapping turtle populations in perpetuity. Head starting is the practice of raising juveniles up to a size less vulnerable to predators prior to release back into their population. Both studies (Congdon et al. 1993, and Congdon et al. 1994) demonstrate the necessity of an all age class protection strategy to successfully maintain a viable population. Congdon et al. (1994) also showed through a detailed life history table that a continued, sustainable harvest of many snapping turtle populations is virtually impossible. Huestis and Meylan (2004) documented a major shift in the turtl e assemblage of Rainbow Run over sixty years since Louis Marchands masters thesis survey (Marchand 1942). Without baseline data such as Marchands, Huestis and Meylans (2004) survey would not have proved as insightful nor would it have revealed the im pact of harvest. My study sets the stage for future freshwater turtle research at Nokuse Plantation by initiating a mark r ecapture program. Data collected in the future will reveal individual growth and
24 population trends (Burke et al. 1995) as well as any turtle assemblage shifts that may occur in the study creeks. As Congdon et al. (1994) demonstrated, demographic data could provide an indicator of ecosystem health: a lack of juveniles despite adequate sampling suggests inadequate recruitment. If sufficien t adult females are present to maintain a population, the root cause may be subsidized predators, lack of proper nest sites, or another factor not yet explored. Coupling turtle demographic and community structure studies with more macro scale ecosystem res earch will lead to better understanding and better action plans. For instance, if adult females are few and recruitment is low an intensive restoration effort can begin that includes habitat restoration, protection of nests, and head starting. These effort s will ultimately fail though if for instance, a major roadway is a source of mortality and a solution is not found to alleviate that drain on the population. Environmental Factors and Freshwater Fish Communities Abiotic factors have also been demonstrated as relevant in structuring fish communities. Although many physiological differences affect the way fish and turtles interact with and utilize their environments, freshwater turtles are dependant upon aquatic habitat for many biological needs. When consid ering an ecosystems ability to support diversity and abundance of vertebrates the fundamentals may not be different. I have highlighted a few studies that focus on the environmental factors that influence freshwater fish species richness. The approach t aken by ichthyologists may serve well as a basis for future herpetological investigations. Gorman and Karr (1978) documented strong correlations between freshwater fish assemblages and three major environmental factors: stream depth, bottom type, and
25 curre nt. They found that fish species diversity increased in association with increased habitat complexity and warned against harmful homogenization through ditching and dredging, canopy removal/deforestation and associated siltation, and sewage effluent. Recal l that DonnerWright et al. (1999) was a similarly cautionary tale for freshwater turtles, habitat alteration deeply impacted environmentally sensitive species. Dunson and Travis (1991) conducted a rigorous examination of the effects of abiotic and biotic factors that play significant roles in the community structure of three species of fish in the genus Lucania (killifishes). The authors expressed deep concern for the frequent oversight of biologists in neglecting abiotic factors as pivotal forces that str ucture ecological systems, especially among closely related species. Differences were noted between three study organisms in response to changes in pH, temperature, oxygen concentration, and (especially) salinity. They concluded that community ecology cou ld only be grasped holistically if researchers study both biotic and abiotic factors in natural systems, and stated that the interactions are key to a true understanding. Moyle and Light (1996) found exotic fish invasions in California were controlled by f avorable abiotic factors not by biota present, etc, as is often suggested. They found this pattern to hold true with a substantial list of fish species in the Eel River drainage, California. Hydrologic regime (damming and reservoirs), in the study area s was the most important hurdle for the fishes. Biotic factors such as competition and predation were less important. Recall Reese and Welsh (1998) also documented detrimental effects of damming on turtles by interfering with thermoregulation and nesting p hysiology. Jackson et al. (2001) painted a much more complex picture of the factors that structure freshwater fish communities than Moyle and Light (1996). They detailed the biotic
26 aspects of fish ecology (i.e. predation and competition) as well as the ab iotic factors, which they broadly categorized as physical (temperature, stream morphology, flow dynamics) or chemical (oxygen and pH, etc). They developed complex matrices for the varied levels and scales associated with fish communities. This studys find ings mirror some of the ecological relationships (especially predation) detailed by Molls (1990) treatment of freshwater turtles in Belize stream. The future of freshwater turtle research may include similar matrices and interdisciplinary inquiry. A rece nt study ( Luiselli 2008) synthesized the published data on freshwater turtle assemblage resource partitioning. The major conclusion of that study was that microhabitat is the most defining feature. Luiselli (2008) did not, however focus on the driving fac tors that structure turtle communities. Site Overview I conducted the field research for my study at Nokuse Plantation, a 21,000 ha private conservation tract in the western Florida panhandle in Walton County (Figure 1 1). This was the first systematic su rvey of freshwater turtles conducted on the property, which borders the lower Choctawhatchee River along its western floodplain. Nokuse Plantation was purchased in part to enhance connectivity of expansive wilderness areas in Florida and Alabama including Eglin Air Force Base and land managed by The Nature Conservancy along the Choctawhatchee River floodplain (Figure 1 2). Nokuse Plantations mission includes the restoration of large enough tracts of land to provide habitat corridors for large carnivores su ch as Ursus americanus black bears. My study sites are situated in the middle of a herpetological hotspot (Carr 1940, Iverson 1992). The region, eastward to the Apalachicola River drainage and westward to
27 Mobile Bay, hosts the richest diversity of freshw ater turtles in the United States (Iverson and Etchberger 1989). I anticipated encountering Apalone ferox, Florida softshell turtles, Apalone spinifera, spiny softshell turtles, Deirochelys reticularia, chicken turtles, Pseudemys floridana, Florida river cooters Pseudemys concinna, Terrapene carolina, box turtles Trachemys scripta, yellow bellied sliders, Kinosternon subrubrum, eastern mud turtles, Sternotherus minor, loggerhead musk turtles, Sternotherus odoratus, stinkpots, and Chelydra serpentina, sna pping turtles in my surveys as they have been observed on the property by Matt Aresco (pers. comm.). I conducted a comparative study of lotic turtle assemblages and abiotic/ biotic factors of four water bodies (Figure 1 3) at Nokuse Plantation during June August 2008 These sites are: Dismal Creek (Figure 1 4) Big Cypress Creek (Figure 1 5) Black Creek, (Figure 1 6) and Seven Runs Creek (Figure 1 7). Dismal Swamp drains into Dismal Creek and Big Cypress Creek and buffers temporal/ seasonal and spatial fl uctuation of the Choctawhatchee River. These four streams offer varied macrohabitats. Dismal Creek and Big Cypress Creek are slow moving blackwater creeks with relatively high levels of detritus. Dismal Creek has more canopy cover and less basking sites t han Big Cypress Creek. Black Creek is a blackwater stream with moderate current, a sand bottom, and is fed in part by seepage. Black Creek has a heavy canopy and feeds directly into Choctawhatchee Bay. Seven Runs Creek is a sand bottomed seepage stream fed by numerous steepheads with moderate canopy cover and the highest flow. Since all four creeks were in relatively close proximity to one another I sought an opportunity to investigate their chelonian communities and environmental factors that structure th ose communities. Through partnership with the Choctawhatchee Basin
28 Alliance and FDEP LAKEWATCH program I sampled water quality of my study creeks during the same period I conducted turtle trapping efforts.
29 Figure 1 1. Florida map with Walton Co highlighted in red. The arrow indicates Nokuse Plantations location. Source: http://en.wikipedia.org/wiki/Walton_County,_Florida
30 Figure 1 2. Conservation lands in the FL panhand le. Nokuse Plantation is highlighted in red. Nokuse Plantation was purchased in part to enhance connectivity of wilderness areas including Eglin Air Force Base and land managed by The Nature Conservancy along the Choctawhatchee River Courtesy of Nokuse Pl antation.
31 Figure 1 3. Map depicting the creeks studied at Nokuse Plantation and the Choctawhatchee River, Walton Co., FL.
32 Figure 1 4. Dismal Creek (Walton Co., FL). Dismal Creek is a slow moving swamp fed blackwater creek. Note closed c anopy and heavy detritus load. This creek had the highest turtle diversity four species of chelonians were trapped. Photo by Ben Atkinson.
33 Figure 1 5. Big Cypress Creek (Walton Co., FL). Big Cypress Creek is a slow moving swamp fed blackwater creek with three commonly captured omnivorous turtle species Note the relatively open canopy and abundance of deadwood for basking. Photo by Jason Butler.
34 Figure 1 6. Black Creek (Walton Co., FL). Black Creek is a blackwater stream dominated by S. minor with moderate current, a sand bottom and is fed in part by seepage Photo by Ben Atkinson.
35 Figure 1 7. Seven Runs Creek (Walton Co., FL). Seven Runs Creek is a sand bottomed seepage stream fed by steepheads where o nly S. minor was observed. This adult female S. minor observed basking was hand captured Photo by Ben Atkinson.
36 CHAPTER 2 METHODS AND MATERIALS Freshwater Turtle Community Sampling Freshwater turtles were surveyed using hoop nets, mod ified crayfish traps, and hand capture. Turtles were identified to species; morphometric data were recorded and turtles were marked for recapture. Trapping was conducted in 0.5 km sections of four major streams on Nokuse property: Seven Runs Creek, Dismal Creek, Big Cypress Creek, and Black Creek using baited hoop net traps and baited modified crayfish traps. Turtles were also hand captured while snorkeling and canoeing. Hoop traps and crayfish traps were set with approximately 20 cm exposed to provide an a irspace so that turtles and other lunged vertebrates (e.g. two toed amphiuma, Amphiuma means ) could breath. Turtle trapping was conducted from 3 June 2008 through 13 August 2008. Four hoop nets, two 76.0 cm and two 91.0 cm diameter hoops, with 3.0 cm mesh measured diagonally and four modified crayfish traps, with 2.5 cm hexagonal mesh ( Johnson and Barichivich 2004) were utilized per sampling effort (eight traps per array). A randomized block design was employed: trap styles were alternated, and eight traps were set at approximately 62.5 m straight line distance intervals at each of four creeks for a total stream study section measuring 0.5 km per creek. Traps were set in alternating depths; trap area microhabitats were determined by Global Positioning System (GPS) coordinates instead of selecting trap sites based on apparent structural suitability to avoid intentional bias of species detectability. My sampling effort was replicated at each creek ten times (8 traps x 10 trap nights per trap = 80 trap nights per creek). Creeks were sampled in rotation to avoid seasonal and weather based biases. Trapping data represent a total of 320 trap nights for the
37 combined study creeks. Hoop nets were baited with locally caught fresh cut fish as suggested by Jensen (1998 ), including Cynoscion nebulosus speckled seatrout, Mugil cephalus mullet, and Pomatomus saltatrix ; bluefish; crayfish traps were baited with canned sardines packed in soybean oil. Bodie et al. (2000) also alternated trap sizes and bait types (fresh fish and canned sardines). Traps were set in areas with and without deadwood basking sites by inserting PVC pipes into the substrate for crayfish traps and commercial metal T posts (as used to erect traffic signs) for hoop nets, tying the closed above water en d to a post. The mouth of the hoop nets were anchored to the stream bottom with T posts (Figure 2 1) and terminal hoop rings were secured to the T posts using heavy duty nylon brass ratcheted cinch straps to prevent rolling by Alligator mississipiensis Am erican alligators. Crayfish traps were secured to the PVC pipes using multiple heavy duty wire ties. Trap stations were identified by GPS coordinates and stations remained consistent throughout my study. Mark Recapture All captured turtles were identified to species, sexed, and females were palpated for the presence of shelled eggs. Permanent marking techniques varied as appropriate for the species and individual size. Chelydra serpentina, snapping turtles were marked by drilling holes (approximately 0.5 cm ) through the marginal scutes with a rechargeable battery powered cordless drill at the posterior portion of the carapace according to a Nokuse Plantation numbering system (Figure 2 2). I marked Sternotherus minor, loggerhead musk turtles and Sternotherus odoratus, stinkpots by filing notches into the marginal scutes of the carapace with a triangular file.
38 Trachemys scripta, yellow bellied sliders (>75 g) were fitted with PIT (passive integrated transponder) tags, which were inserted subcutaneously into the inguinal connective tissue proximally anterior to the right rear leg. PIT tags have become standard tools for animal identification, but long term effectiveness is not yet demonstrated in freshwater turtles (Buhlmann and Tuberville 1998, Elbin and Burger 1994, Runyan and Meylan 2005). Gibbons and Andrews (2004) give a critical review of marking techniques with an emphasis on PIT tags. They conclude that PIT tags represent the best of todays animal marking technology due to (among other reasons) their com pact size, retention, and the ability to set up remote stations for scanning individuals. Gibbons and Andrews (2004) also commented on several drawbacks to PIT tags including high cost of the tags and readers, proximity required for a successful scan, and the fact that carapace notching has proven effective for freshwater turtles and tortoises. They suggested that in an ideal research program an animal would be PIT tagged and marked secondarily in the unlikely event that the PIT tag fails. I injected T. scripta with Biomark Brand PIT tags using a N125 1.25 12 gauge needle and MK7 syringe style implanter, model #TX1411SSL and used Biomark a Mini Portable Reader 2 with a Cordura weather resistant cover (Biomark products are manufactured by Destron Feari ng, Inc., of St. Paul, MN). The area was first sterilized with isopropyl alcohol, followed by a liquid Betadine solution. PIT tags were placed in shallow plastic dishes partially filled with isopropyl alcohol prior to injection and needles/syringes were al so sterilized before each use. After implanting the PIT tag, liquid bandage artificial moleskin was brushed onto the entrance site to seal out bacteria and
39 encourage retention of the PIT tag during the formation of scar tissue (Buhlmann and Tuberville 19 98). National Band and Tag Company (Newport, KY) Monel metal livestock tags model #1005 3 (approximately 0.25 cm x 1.5 cm) were fixed to the posterior carapace of T. scripta as part of a comparative tag retention component of the study. Monel tags were at tached to the sliders by drilling a small hole (approximately 2.0 mm) through the posterior carapace at the 8 th left marginal scute (Cagle 1939) and clamped shut using needle nose pliers. Morphometrics To establish baseline demographics and allow comparis on of communities between creeks, I recorded standard morphometrics for each captured turtle. Using Haglf Mantax 95 cm aluminum calipers for large turtles and SPI 150 mm plastic metric dial calipers for smaller individuals, straight carapace length (SCL), carapace width (CW), maximum shell height (H), plastron length (PL), tail length (TL) and maximum head width (HW) were measured in millimeters. Mass (g) was determined for captured turtles using an Ohaus Scout Pro 2000 g digital scale for small turtles; s pecimens too large for the digital scale were weighed with a 20 kg Pesola suspension spring scale. The digital scale was calibrated by the digital keypad and the suspension scale was calibrated using tare screws. Musk Turtle Dietary Sampling To elucidate diet of two congeneric chelonians I collected fecal samples from 40 trapped musk turtles. Loggerhead musk turtles, S. minor, and stinkpots, S. odoratus, were rinsed to remove debris and held overnight in plastic containers with fresh water at
40 approximatel y 5.0 cm depth. The following day turtles were removed from the containers and the water was filtered through a hand held fine meshed sieve. Following straining, sample materials were transferred to labeled standard 35 mm film canisters and stored in isopr opyl alcohol for analysis. All turtles were released at the point of capture. Dietary analyses were conducted in the Department of Herpetology collections area in the UF Florida Museum of Natural History (Gainesville, FL) using a Bausch & Lomb 30x magnific ation binocular dissecting microscope, fitted with a Reichert Jung dual probe electric light source. Samples were analyzed individually and items were identified to the lowest taxonomic level possible using Merrit and Cummins (1996) to identify aquatic ins ect fragments and Pennak (1989) for identification of freshwater invertebrates in general. Relative importance of food items were inferred by separating sample contents in a Petri dish under the dissecting scope and then determining volumetric displacemen t of each taxon in the fecal sample. A ttempts were made initially to count individual organisms in the samples when possible (particularly the calcified shells of gastropods and pelecypods). This ultimately proved unfeasible due to the fragmentary and frag ile nature of the samples. Volumetric displacement data were produced per sample using a glass 10 mL graduated cylinder. Each sample was started at a 4.0 mL with excess sample isopropyl. Each taxonomic group of a sample was transferred into the graduated cylinder using jewelers microforceps and the level of displacement was recorded. This step was repeated for each taxon.
41 Folkerts (1968) followed a similar methodology, but pooled samples during both the collection and analyses. This did not allow observa tion of differences between individuals (or to gather data on dietary changes by age or gender). Marion et al. (1991) utilized similar volumetric displacement methods; they were also able to also glean gravimetric data with a drying oven and balance due to availability of formalin as a fixative during sample preservation. Since neither formalin nor fume hood were available at the field station, I used non toxic isopropyl to preserve fecal samples. The desiccating nature of alcohol inhibited categorically an alyzing the mass of samples. I limited my dietary analyses to volumetric displacement by taxon per sample. Volumetric displacement has potential to bias sample interpretation by creating an impression of greater preference for a particular food item over another due to artifacts of size and relative un digestibility of hard parts (e.g. crayfish claws). The data I present (Figure 3 4) should be interpreted with those limitations in mind. Gravimetric data can also lead to biased conclusions regarding relativ e importance of food items since soft parts are often digested and soft bodied organisms may less frequently be evidenced in passively collected fecal samples. Furthermore, the amount of nutrition absorbed from one large prey item may equal or exceed seve ral individuals of a smaller taxon. Water Quality Monitoring My study documents freshwater turtle communities across a spectrum of commonly measured abiotic stream variables (Dunson and Travis 1991, Allan 1995, Angelier 2003). Abiotic factors measured incl uded water temperature (C), dissolved oxygen (mg/L and % saturated), pH, depth (meters), salinity (ppt), and turbidity (NTU). Measurements were taken at two depths, 0.5m and the bottom using a Hydrolab Quanta
42 Water Quality Monitoring System provided by th e Choctawhatchee Basin Alliance (CBA). I collected water samples (at 0.5 m depth) manually at all sampling stations in two 250 ml, acid washed, triple rinsed Nalgene bottles per station and later analyzed by the Florida LAKEWATCH Program. LAKEWATCH is aff iliated with the Florida Department of Environmental Protection and is administered through the University of Floridas Institute of Food and Agricultural Sciences Department of Fisheries. Samples were transported back to the field station at Nokuse Plan tation in an insulated plastic cooler with artificial ice packs. One set of water samples was frozen prior to being shipped to the LAKEWATCH laboratory in Gainesville, Florida and later analyzed for total phosphorus ( g/L) and total nitrogen ( g/L). The second set of surface samples were filtered in the lab using a Gelman Type A E glass fiber filter to analyze the water for chlorophyll content (Pt CO Units) Filters were then stored in Nalgene screw top containers filled partially with silica gel desiccan t before being frozen until processing at the LAKEWATCH laboratory.
43 Figure 2 1. The author securing a hoop net to capture turtles in Big Cypress Creek (Walton Co., FL). T posts were used to prevent rolling of the trap by Alligator mississippi ensis Photo by Jason Butler.
44 Figure 2 2. Nokuse Plantation carapace notching schematic. Marginal scutes were notched with a triangular file using a combination of marks. This scheme was adapted from a system created at Nokuse Plantati on for marking Gopherus polyphemus
45 CHAPTER 3 RESULTS Species Richness and Biodiversity I encountered the following eight species at Nokuse Plantation during June August 2008: Deirochelys reticularia (chicken turtle, roadkill) Pseudemys conc inna (river cooter, basking and skeletal remains) Terrapene carolina (box turtle, roadkill and alive on road) T. scripta (yellow bellied slider, trapping and basking) Kinosternon subrubrum (eastern mud turtle, hand capture) S. minor (loggerhead musk tu rtle, trapping, basking, and hand capture) S. odoratus (stinkpot, trapping) and C. serpentina (snapping turtle, trapping). For four days (30 May 2008 2 June 2008) I left eight traps set at Seven Runs Creek prior to baiting them for the first time, as s uggested by Margaret Gunzburger. She is co authoring a manuscript (in prep) that details the biasing of trap captures for Siren and Amphiuma depending on bait used. I captured no turtles prior to baiting. Captures during the non bait experimental period in cluded two Ameirus natalis yellow bullhead catfish, two Lepomis macrochirus bluegill, one Ambloplites ariommus shadow bass, and a Rana clamitans bronze frog. Fish identifications were made according to Page and Burr (1991). A single Nerodia taxispilota brown water snake was observed basking on the trap containing a catfish. I baited the traps after checking them on 2 June 2008. The following day when I returned to check the traps at Seven Runs Creek I had captured (n=4) S. minor and hand captured a b asking adult female S. minor (Figure 1 7). Jensen (1998) tested bait preference in freshwater turtles, but non baited traps were not part of his experimental
46 design. A few studies referenced in the introduction utilized creamed corn as part of their baitin g arsenal. This may increase capture of vegetarian leaning Pseudemys Trapping results differed among study creeks (Table 3 1); my data suggest differences in number of turtle species present as well as abundance disparities within turtle species between c reeks. Species richness of cumulative turtle species trapped per creek is provided (Figure 3 1). Since my surveys yielded no new turtle species for any creek after the third sampling night, despite trapping for seven additional nights per creek, I feel con fident that my data provide a solid indication of the turtle species present in the study areas. The ubiquitous chelonian in lotic Nokuse habitats appears to be the loggerhead musk turtle, Sternotherus minor S. minor was captured in all study areas, and in higher densities than any other turtle species during the course of my study. Graphical representations of S. minor size class distributions are provided for Dismal Creek (Figure 3 2a), Big Cypress Creek (Figure 3 2b), Black Creek (Figure 3 2c), and Sev en Runs Creek (Figure 3 2d). Sternotherus odoratus size class distributions are presented for Dismal Creek (Figure 3 3a) and Big Cypress Creek (Figure 3 3b). Dismal Creek trapping yielded the highest omnivorous chelonian richness with four species captured : S. minor (n = 36) S. odoratus (n = 7) C. serpentina (n = 4), and T. scripta (n = 3) Trapping suggested differences in overall species richness between creeks across varied taxa, particularly fishes (Table 3 2). Dismal Creek fish captures included Lepo mis miniatus, spotted sunfish (n = 30), Lepomis macrochirus, bluegill (n = 1), Lepomis gulosus warmouth bass (n = 2), Esox niger, chain pickerel (n = 3), and Ameiurus natalis, yellow bullhead (n = 2). Several Amphiuma means, two toed amphiuma (n = 6)
47 were captured in Dismal Creek and a single large Rana catesbeiana, bullfrog was captured in a hoop net. I trapped three chelonian species in Big Cypress Creek: S. minor (n = 38) T. scripta (n = 15) and S. odoratus (n = 7). P. concinna was observed basking on numerous occasions and in the form of skeletal remains on 15 May 2008 along a firebreak at the sampling access point. Raided nests were discovered in the vicinity of the river cooter skeleton; gross observations suggest that some turtles preferentially ne st in cleared areas. A single juvenile K. subrubrum was hand captured on 16 June 2008 just below the downstream terminus of the sampling transect in shallow water microhabitat. Non target organisms captured by trapping on Big Cypress Creek included the fol lowing fishes: L. miniatus (n = 26), L. gulosus (n = 28), E. niger (n = 8), and A. natalis (n = 2). A. means were also trapped (n = 3). Black Creek turtle trapping produced two chelonian species: S. minor (n = 23) and a single T. scripta Relatively few f ishes were captured on Black Creek. Fish species documented were: Lepomis miniatus spotted sunfish (n = 1), Ameiurus natalis yellow bullhead (n = 2), and Lepomis microlophus redear sunfish (n = 1). Seven Runs Creek trapping revealed the lowest turtle ri chness, with just one species captured: S. minor (n = 15). In addition to the loggerhead musk turtles, L. miniatus (n = 5), a single A. natalis and a single Ambloplites ariommus, shadow bass. The shadow bass represents the only individual of the species c aptured during the study. Musk Turtle Dietary Analyses Dietary analyses determined a wide variety of food items being consumed by Sternotherus spp., musk turtles at Nokuse Plantation. Musk turtle diets differed between
48 my study creeks (Figure 3 4). My die tary data also suggest an ontogenetic shift in dietary preferences. Younger animals tend to feed more heavily on odonates (dragonflies and damselflies). Adults appear to feed more opportunistically, consuming a wider range of prey including: pelecypods (bi valves), decapods (crayfishes), gastropods (snails), fishes, coleopterids (beetles), hymenopterids (ants), annelids (segmented worms), and simulids (flies) were all found in at least some of the samples. Although S. minor samples from Seven Runs Creek (n = 2) and Black Creek (n = 3) are few, plants played a major role in the diet of these omnivorous turtles as adults, comprising nearly 70% of the samples analyzed from Seven Runs Creek. Water Quality Analyses Water quality parameter data were analyzed using a Fishers LSD one way ANOVA procedure with MiniTab v.15. See Figure 3 5 for depictions of mean comparisons of water quality parameters that were statistically different between all study creeks. Table 3 2 also shows compared means of total phosphorus valu es, chlorophyll values, and saturated oxygen values. Total phosphorus and chlorophyll show positive correlations with turtle species richness, and saturated oxygen shows a negative correlation. Table 3 3 provides a summary of mean values of water quality p arameters that were not statistically different between all study creeks. Primary productivity measures (total phosphorus, total nitrogen, and chlorophyll) are reported first. Mean total phosphorus (TP) was significantly different (p < 0.001) between all four of my study creeks. The mean values for total phosphorus per creek were: Dismal Creek = 12.6 g/L ( = 0.89), Big Cypress Creek = 11.2 g/L ( # = 1.30), Black Creek = 7.2 g/L ( # = 0.84), and Seven Runs Creek = 5.6 g/L ( # = 0.55).
49 Mean total nitrogen (TN) levels showed no significant difference between Dismal Creek, Big Cypress Creek, and Black Creek; however Seven Runs Creek nitrogen level was significantly different from all of the other study creeks. The mean values for total nitrogen per creek were: Dismal Creek = 978.0 g/L ( # = 349.7), Big Cypress Creek = 1076.0 g/L ( # = 520.2), Black Creek = 618 .0 g/L ( # = 161.9), Seven Runs Creek = 506.0 g/L ( # = 20.7). Mean chlorophyll (CH) levels in Dismal Creek and Big Cypress Creek were not significantly different, and Black Creek and Seven Runs Creek chlorophyll levels were not significantly different. B lack Creek and Seven Runs Creek mean chlorophyll levels were significantly different from Dismal Creek and Big Cypress Creek. The mean values for chlorophyll per creek were: Dismal Creek = 2.0 g/L ( # = 1.26), Big Cypress Creek = 1.4 g/L ( # = 0.89), Black Creek = 0.8 g/L ( # = 0.45), and Seven Runs Creek = 0.8 g/L ( # = 0.45). Mean temperature was significantly different between Dismal Creek and Big Cypress Creek, and Big Cypress Creek and Seven Runs Creek. Dismal Creek temperature was not significantly d ifferent Black Creek or Seven Runs Creek. Big Cypress Creek and Black Creek temperatures were also not significantly different. Mean temperature levels ranged from 23.7 C at Dismal Creek t o 24.8 C at Big Cypress Creek. Mean temperature levels per creek w ere: Dism al Creek = 23.7 C ( # = 0.46), Big Cypress Creek = 24.8 C ( # = 0.50), Black Creek = 23.9 C ( # = 0.55), and Seven Runs Creek = 23.6 C ( # = 0.57). Dissolved oxygen levels and mean (%) oxygen saturation levels were parallel and significantly different bet ween all study creeks. Oxygen levels in the water reveal a
50 negative correlation with turtle species richness (i.e. the higher the mean level of dissolved oxygen per creek, the lower the corresponding turtle species richness was represented for a given cree k). Mean dissolved oxygen levels per creek were: Dismal Creek = 3.8% O 2 ( # = 1.06), Big Cypress Creek = 4.6% O 2 ( # = 0.14), Black Creek = 6.4% O 2 ( # = 0.39), and Seven Runs Creek = 7.5% O 2 ( # = 0.15). Mean percent oxygen saturation levels per creek were: Dismal Creek = 44.4% O 2 ( # = 12.90), Big Cypress Creek = 55.4% O 2 ( # = 2. 02), Black Creek = 76.7% O 2 ( # = 5.53), and Seven Runs Creek = 88.8% O 2 ( # = 2.29). Mean levels of pH were not significantly different between study creeks. Mean pH levels per creek were: Dismal Creek = 4.8 pH ( # = 1.08), Big Cypress Creek = 5.0 pH ( # = 0 .69), Black Creek = 4.1 pH ( # = 0.87), and Seven Runs Creek = 4.3 pH ( # = 0.74). Mean salinity (ppt) levels were not significantly different between Dismal Creek, Big Cypress Creek, and Black Creek. Seven Runs Creek mean salinity level, however was signif icantly different from the other study creeks. Mean salinity levels per creek were: Dismal Creek = 0.030 ppt ( # = 0.000), Big Cypress Creek = 0.030 ppt ( # = 0.000), Black Creek = 0.028 ppt ( # = 0.004), and Seven Runs Creek = 0.020 ppt ( # 0.000). Mean turb idity levels (NTU) per creek showed no significant difference. Field observations during collection suggest turbidity data should be considered suspect or irrelevant. Output on the Hydrolab was unstable during readings and any disturbance caused wide fluct uations. Mean turbidity levels per creek were: Dismal Creek = 4.6 NTU ( # = 7.08), Big Cypress Creek = 8.0 NTU ( # = 8.08), Black Creek = 6.2 NTU ( # = 3.37), and Seven Runs Creek = 4.26 NTU ( # = 2.38).
51 Table 3 1. Relative abundance of vertebrates captured b y trapping at Nokuse Plantation. Note: totals for non turtles represent number of captures, not individuals; non turtle captures were not marked. Dismal Creek Big Cypress Creek Black Creek Seven Runs Creek C. serpentina 4 0 0 0 S. minor 36 38 23 15 S. odoratus 7 7 0 0 Turtles T. scripta 3 15 1 0 A. natalis 2 2 2 1 A. ariommus 0 0 0 1 E. niger 3 8 0 0 L. gulosus 2 28 0 0 L. macrochirus 1 0 0 0 L. microlophus 0 0 1 0 Fish L. miniatus 30 26 1 5 A. means 6 3 0 0 R. catesbeiana 1 0 0 0 Amphibian s
52 Figure 3 1. Turtle species richness of trapped samples.
54 Figure 3 3. Sternotherus odoratus size class distribution for Dismal Creek (a) and Big Cypress Creek (b). Note: no juveniles were captured in Big Cypress Creek.
55 Figure 3 4. Sternotherus minor and Sternotherus odoratus dietary averages by creek. Anne: Annelida (segmented worms) Cole: Coleoptera (beetles) Deca: Decapoda (10 footed crustaceans, crayf ishes) Gast: Gastropoda (univalves, freshwater snails) Hyme: Hymenoptera (ants and bees) Odon: Odonata (dragonflies and damselflies) Pele: Pelecypoda (bivalves, freshwater clams) Simu: Simulidae (biting flies)
56 Figure 3 5. Total phosphorus (a), c hlorophyll (b), and percent oxygen saturation (c) compared means per creek.
57 Table 3 2. Species richness, Shannon diversity, community evenness, and statistically different mean primary productivity and oxygen saturation values for all study creeks. *Evenness of total spp. Disma l Creek Big Cypress Creek Black Creek Seven Runs Creek Turtle spp. richness 4 3 2 1 Total spp. richness 11 8 5 4 Shannon Diversity 1.71 1.76 0.71 0.88 Evenness* 0.71 0.85 0.44 0.63 Phosphorus ( g/L) 12.6 11.2 7.2 5.6 Chlorophyll ( g/L) 2 1 .4 0.8 0.8 Oxygen Saturation (%) 44.4 55.4 76.7 88.8
58 Table 3 3. Water quality parameters with statistically insignificant differences between study creeks. Mean values are listed followed by standard deviations. Dismal Creek Big Cypress Creek Black Creek Seven Runs Creek Nitrogen ( g/L) 978.0, 349.7 1076.0, 520.2 618.0, 161.9 506.0, 20.7 Temp. ( C) 23.7, 0.5 24.8, 0.5 23.9, 0.6 23.6, 0.6 pH 4.8, 1.0 5.0, 0.7 4.1, 0.9 4.3, 0.7 Sali nity (ppt) 3, 0 3, 0 3, 0.04 2, 0 Turbidity (NTU) 4.6, 7.08 8.0, 8.08 6.2, 3.37 4.26, 2.38
59 CHAPTER 4 DISCUSSION Other potential resident chelonians of Nokuse Plantation include Graptemys barbouri Barbours map tur tle, Macrochelys temminckii, alligator snapping turtle, and Malaclemys terrapin, diamondback terrapin. Graptemys and Macrochelys have not been observed on Nokuse property to date, but have been identified in the vicinity (Moler 1996, Enge and Wallace 2008) The Florida Freshwater Fish and Game Conservation Commission (FWC) list both species as Species of Special Concern. No museum records exist for M. terrapin west of the Apalachicola River drainage in Florida, however diamondback terrapins have been rece ntly identified in the Pensacola Bay area (Rick OConnor, pers. comm.) and Bartlett and Bartlett (2006) claim Choctawhatchee Bay hosts two M. terrapin subspecies. M. terrapin could eventually be encountered in the lower reaches of Black Creek. Community Ty pes I found two discernable community types when analyzing my quantitative trapping and water quality data. Qualitative habitat observations also define the significant differences I observed in the creeks ecology. Environmental factors that categorize my study streams include: primary productivity and water quality, current velocity (flow) and detritus loads, canopy cover, and deadwood availability for aerial basking by freshwater turtles. The primary productivity parameters I measured were total phosphor us, total nitrogen, and chlorophyll. The additional water quality parameters I measured were temperature, pH, salinity, dissolved and percent saturated oxygen, and turbidity.
60 Statistically significant differences in water quality between all creeks were f ound for total phosphorus, chlorophyll, and oxygen content. Phosphorus leaches from detritus entering the water and limits primary productivity (Cushing and Allan 2001). Detritus inputs in Dismal Creek and Big Cypress Creek, coupled with a low flow environ ment that retains these nutrients create highly productive blackwater stream systems. Although canopy cover was variable between creeks, temperature in the water column was not significantly different between study sites. Salinity, pH, and turbidity were a lso not statistically different between study creeks. Faunal differences distinguishing my study creeks included species composition, species richness and evenness (of vertebrate species captured by trapping), abundance of common species, size class distri bution of musk turtles (particularly the presence of juveniles), and diet of musk turtles. All four creeks contained S. minor but there were clear differences in abundance of the musk turtles between study creeks with greater numbers observed in Dismal Cr eek and Big Cypress Creek and lesser numbers in Black Creek and Seven Runs Creek. Blackwater Cypress Dominated Communities Dismal Creek and Big Cypress Creek shared the first community type. Both creeks shared a water source in Dismal Swamp, the cypress t upelo floodplain swamp that drains into these stream systems. Both creeks had high levels of primary productivity, species richness, and evenness (Table 3 3). They were blackwater communities with low flow, high nutrient input from detritus accumulation, a nd lower percent saturated oxygen in the water column. Phosphorus in the water column was significantly higher in these blackwater cypress dominated communities than in their upland counterparts; phosphorus
61 is the limiting nutrient in freshwater systems a nd therefore, greater primary productivity was measured in these communities. Loggerhead musk turtles were abundant in both of these streams. Detritus accumulation is a primary energy input for these low flow systems, providing the major source of alloch thonous energy (Cushing and Allan 2001) since current does not readily flush these energy inputs downstream, as it does to a greater degree in Black Creek and Seven Runs Creek. When leaves and limbs fall into the Dismal Creek and Big Cypress Creek, physica l abrasion, macroinvertebrates, and microbial action work to break down the material from coarse to fine particulate organic matter (Cushing and Allen 2001). Further disintegration leads to the organic matter dissolving into the water, freeing energy to be utilized by the microbial community. Dismal Creek and Big Cypress Creek were species rich, moderately even communities with higher levels of primary productivity, but lower levels of water column saturated oxygen (Table 3 3) when compared to Black Cree k and Seven Runs Creek. Inefficient degradation of detrital inputs can cause algal blooms and microbial growth, both of which limit the amount of oxygen available in the water column for higher organisms like turtles (Cushing and Allan 2001). Flow was suff icient in these slow moving blackwater creeks to allow for high levels of primary productivity without causing nuisance blooms (Cushing and Allan 2001). I documented total species richness in Dismal Creek and Big Cypress Creek. Eleven vertebrate species w ere trapped in Dismal and eight species of vertebrates were caught in Big Cypress Creek. I derived Shannon diversity values using PC ORD software (McCune and Grace 2002) for this data; those values were 1.71 for Dismal Creek and
62 1.76 for Big Cypress Creek. Shannon diversity values increase when additional species are added, or when the evenness of the species is higher (McPherson and DeStefano 2003). These diversity values show similar trends in species composition. Evenness refers to the relative abundanc e of the species in the dataset the more similar the abundance of the creeks inhabitants, the higher the evenness score (McPherson and DeStefano 2003). Evenness of these streams was also similar with 0.71 and 0.85 values, respectively. I trapped four s pecies of turtles in Dismal Creek ( C. serpentina S. minor S. odoratus and T. scripta ), and three species of turtles in Big Cypress Creek ( S. minor S. odoratus and T. scripta ). Trachemys scripta were captured on Dismal Creek (n=3), Big Cypress Creek (n =15), and Black Creek (n=1). Sliders tendency to bask aerially may be a reason that the highest abundance of Trachemys was found on Big Cypress Creek, which contains abundant deadwood and is the most open canopied creek of the four study areas. Pseudemys concinna were also observed aerially basking on Big Cypress Creek (but not Dismal Creek); river cooters are not included in the vertebrate richness and diversity values since they did not enter my traps. Values I have reported for captured turtles represe nt individual specimens (re captures are not counted twice for turtles in this report). Non turtle captures were not marked, and thus values given represent capture totals not individuals. It is possible that individual fish and/ or amphibians were captu red more than once. Sternotherus odoratus stinkpots are also known to inhabit slow flow and lentic habitats (Iverson and Meshaka 2006). S. odoratus were captured in equal numbers (n=7) in Dismal Creek and Big Cypress Creek, but were not captured in Black Creek or Seven Runs Creek. No juvenile
63 S. odoratus were captured in Dismal Creek which may be a result of predation pressure ( Chelydra were captured in Dismal Creek), or their absence may simply be an artifact of poor survivorship from the recent years nesting efforts. Fish species richness was similar between Dismal Creek and Big Cypress Creek with five and four species, respectively. Dismal Creek fish species were A. natalis E. niger L. gulosus L. macrochirus and L. miniatus Big Cypress Creek fis h species were A. natalis E. niger L. gulosus and L. miniatus Esox niger chain pickerel, were captured in Dismal Creek (n=3) and Big Cypress Creek (n=15), but not in Black Creek or Seven Runs Creek. Lepomis gulosus warmouth bass, were also captured i n Dismal Creek (n=2) and Big Cypress Creek (n=28) but not in Black Creek or Seven Runs Creek. Lepomis miniatus redspotted sunfish, were captured in all four study creeks in varying abundance with Dismal Creek producing the highest number of captures (n= 30); Big Cypress Creek trapping efforts also captured a high number of these fish (n=26). Redspotted sunfish were much less common in Black Creek and Seven Runs Creek with (n=1, and n=5 captures, respectively). Two toed amphiuma ( A. means ), a large aquat ic salamander with vestigial limbs and eyes were captured in both Dismal Creek and Big Cypress Creek, but not in Black Creek or Seven Runs Creek. Substrate type and current velocity are likely reasons that amphiuma were not found in Black Creek and Seven R uns Creek, as they are known to prefer mucky blackwater microhabitats (Means 2000). Upland Moderate Flow Communities Black Creek and Seven Runs Creek form a second general community type that differs greatly from the cypress tupelo dominated floodplain sw amp community type
64 illustrated in Dismal Creek and Big Cypress Creek. Black Creek was also noticeably tannic but flow was greater than in the cypress dominated communities. Periodic flushing pulses after heavy rains, coupled with increased flow appeared to inhibit substantial accumulation of detritus. Seven Runs Creek ran clear under average conditions, but siltation of the water column occurred following flash flood conditions. Black Creek and Seven Runs Creek are upland communities with steeper banks, lo wer levels of primary productivity, less species richness and evenness, moderate to high flow (depending on rainfall), less accumulation of detritus, and higher percent oxygen saturation than their cypress dominated counterparts. Black Creek and Seven Runs Creek were similar in terms of low diversity, low evenness, and moderate flow. Neither stream contained C. serpentina or S. odoratus. Both Black Creek and Seven Runs Creek were dominated by one species of chelonian: S. minor but in low abundance in compa rison to Dismal Creek and Big Cypress Creek. Black Creek and Seven Runs Creek had lower total species richness, diversity, and evenness values and less even distribution of the species within the systems. Black Creek total species richness was five specie s and Seven Runs Creek was four species. Shannon Diversity values for Black Creek and Seven Runs Creek were 0.71 and 0.88, respectively. The evenness of Black Creek was 0.44 and Seven Runs Creek was 0.63. Primary Productivity and Turtle Density My data sh ows primary productivity is positively correlated to musk turtle abundance as well as overall chelonian species richness. I trapped and marked 36 individual loggerhead musk turtles in Dismal Creek and 38 individuals in Big Cypress
65 Creek (the cypress domina ted communities). In Black Creek I marked 23 individual S. minor and in Seven Runs Creek I marked 15 individuals (the upland communities). Dismal Creek S. minor reached larger sizes than in the other study creeks. Three individuals in Dismal Creek exceed ed 100 mm straight carapace length (SCL), and no S. minor in any of the other study creeks reached this length. This may be related to stream depth as my study site on Dismal Creek contained sections that were deeper than any found on other study creeks. O nly one individual per creek exceeded 90 mm in Black Creek and Seven Runs Creek. Big Cypress Creek had no musk turtles exceeding 90 mm SCL, despite producing the highest number of S. minor in all four study creeks. Galbraith et al. (1988) found the same p ositive correlation between primary productivity and snapping turtle abundance but did not report species richness. It is not surprising that my study reflects similarities to their findings. It is surprising, however, that I have not yet encountered any o ther studies that directly correlate primary productivity with turtle species richness. Galbraith et al. (1988) emphasize that although many prior studies linked turtle population density to habitat suitability, they did not define or quantify suitability, and previous investigations did not conduct hypothesis testing to draw causal inference. Diet The musk turtles sampled in my study ( Sternotherus minor and S. odoratus ) showed different dietary trends than the ones sampled by Marion et al. (1991) with Ste rnotherus depressus, flattened musk turtles, and Folkerts (1968) with Sternotherus minor peltifer, stripe necked musk turtles. Musk turtle diets were more varied in Dismal Creek and Big Cypress Creek than in Black Creek and Seven Runs Creek. This likely
66 re flects higher levels of primary productivity resulting in greater diversity of macrophytes and macroinvertebrates on which the musk turtles prey. Galbraith et al. (1988) reported omnivory in Chelydra and used that as argumentation for the importance of pr imary productivity to snapping turtle population density. The dietary analyses I conducted on musk turtle revealed that S. minor and S. odoratus also eat a variety of plants, invertebrates, and an occasional vertebrate. Iverson (1977) described geographi c variation in S. minor and placed my study area in the region that exhibits influence of the peltifer subspecies. Modern molecular genetics sampling may render the subspecific epithet obsolete (Iverson, pers. comm.) but the external morphology of the turt les captured in my study did show, to varying degrees the characteristic stripe necks. The ability of S. minor to maintain populations in varied habitats (Zappalorti and Iverson 2006) and its demonstrated flexibility in diet make S. minor an ideal study o rganism for turtle habitat relationships. Zappalorti and Iverson (2006) note that S. minor populations reach among the highest densities known for any species of turtle. Marion et al. (1991) found gastropods and pelecypods to make up 69.5% and 16.0% of flattened musk turtle diets. Coincidentally, Folkerts (1968) reported gastropods in 69.5% of his stripe necked musk turtles specimens, but just 0.1% occurrence of pelecypods. My study reinforces the ecological assumption that habitat differences influence diet diversity. Since diet differed between creeks in the relatively restricted area of Nokuse Plantation, it is not surprising that my dietary analyses were not the same as Folkerts (1968) or Marion et al (1991)
67 Berry (1975) sacrificed musk turtles to c onduct dietary analyses and was thus able to investigate the entire digestive tract. I opted to use a passive fecal collection method (as detailed in the results section). My dietary sample sizes are much smaller, particularly in Black Creek and Seven Runs Creek. S. odoratus in my study are also few. Continued research could build upon my data set and offer opportunity for a robust comparison. My study did not include creeks with S. odoratus present in the absence of S. minor rendering replication of Berry (1975) unfeasible. I predicted that higher mean levels of dissolved oxygen in the water column would increase the species richness of turtles, due to their ability (especially Sternotherus spp.) to respire underwater. My data, however suggest the opposite trend: the higher the creeks mean oxygen saturation, the lower the turtle species diversity and abundance within a species. Gatten (1984) found that S. minor loggerhead musk turtles could survive for over 5000 hours in oxygen saturated water if the tempe rature was held constant at 22 deg C. For comparison purposes, recall that the mean temperatures of my study creeks ranged from 23.6 deg C to 24.8 deg C, with % oxygen saturation ranging from 44.4 % to 88.8% between creeks. Gatten (1984) did not report th e % oxygen saturation of his mesocosms. It may be that the high level of dissolved oxygen in Seven Runs Creek is a major factor that makes the habitat suitable for S. minor since primary productivity levels are comparatively quite low, and food availabil ity appears to be scant. Gross observations of musk turtles poor swimming proficiency in swift current of portions of Seven Runs Creek and Black Creek is also a plausible limiting factor.
68 Land use (historic and current) may play a role in changes in spec ies richness. Several studies have documented this phenomenon (Bodie et al 2000, Marchand and Litvaitis 2004 ). The land uses at Nokuse Plantation have led to visible erosion, and the Regional Utilities of Walton County have purchased the right to drill a s eries of wells to draw water for human consumption on Nokuse Plantations northern property (The Nature Conservancy and Nokuse Plantations Seven Runs Creek Florida Forever Proposal 2008 ). Extensive ground water wells and associated heavy equipment have led to near impassability of some access roads, even with four wheel drive vehicles. Water shortage may also be a constraint on the health of the creeks I studied particularly Seven Runs Creek. Past clear cutting of parts of the creeks buffer zone ass ociated with row crops (including watermelon, and soybeans), sod farming, and silviculture for pulp production have likely degraded the natural hydrology. Former property managers planted fast growing pines in place of long leaf pine, Pinus palustris (The Nature Conservancy and Nokuse Plantations Seven Runs Creek Florida Forever Proposal 2008 ). The greater watershed, including parts of nearby Alabama and Mississippi were also in the midst of a drought at the onset of this study (NOAA 2008). Several ques tions arose during the course of fieldwork and laboratory analyses for which a priori hypotheses were not developed (e.g. why do heavy rain events/flash floods result in little to no trap captures?). My data suggest a decrease in trap ability of turtles (and other creek dwellers) following episodic storms. Turtles may seek refuge in smaller tributary streams or other microhabitat, possibly on land. Radio telemetry may be a tool to determine where the turtles go during such events, but safety of the resear cher could be compromised during flash flood conditions.
69 My study creeks ability to rise dramatically during/following tremendous rainfall should not be underestimated. Species living in Black Creek and Seven Runs Creek in particular require environmenta l coping mechanisms for the sudden rush of murky water that rips through these streams during and immediately after storms. Future research at Nokuse Plantation must consider rainfall fundamentally when planning work that involves these creeks, particularl y Black Creek and Seven Runs Creek. Traps can become submerged despite efforts to maintain airspace. A few inches of rain is multiplied in terms of creek level due to runoff. This is especially true when the surrounding soil is already saturated. Feeder s treams carry the precipitation momentum and swell the creeks volume dramatically. My trapping data also suggest the sometimes ephemeral or seasonal nature of species presence. C. serpentina was captured in Dismal Creek on 7 June 2008, (n = 3) and 8 June 2 008 (n = 1). These captures occurred the first time I trapped Dismal Creek and I never captured or observed another C. serpentina the rest of the field study in Dismal Creek or any of the other study creeks. These snapping turtle captures took place during a drought and major rainfall began to return frequently shortly after these captures. Matt Aresco (pers. comm.) indicated that the seasonal/temporary ponds uphill from Dismal Swamp had again been filled with rainwater. Aresco et al. (2006) and Aresco and Gunzburger (2007) noted snapping turtles migrating under similar conditions elsewhere in Florida. By recording (Global Positioning System) GPS coordinates for each capture marking turtles for recapture, information on individual turtle home ranges and move ments may be gleaned in the future. Recent investigations on S. odoratus (Tavano
70 2008) found stinkpots movement between captures from 2004 to 2007 averaged 198 m for males and 102 m for females and that most recaptured turtles were found either within their original capture station or the adjacent station. Preliminary interpretation of my recapture data reveal similar trends in habitat use by S. minor and S. odoratus with turtles most often being recaptured in either the trap they in which they were originally captured, or in the next closest trap upstream or downstream from the original point of capture. Since my trap stations were set at consistent 62.5 m intervals, one can infer that musk turtles in my study creeks are utilizing relatively small st retches of the stream channel as well (the doubled distance between my traps was 125 m). That rough approximation is in concordance with the observations made by Tavano (2008). A single T. scripta captured in Black Creek may indicate natural rarity of the species in the creek or temporary residency, as T. scripta is a highly mobile species in terms of its ability to make overland journeys (Thomas 2006). The individual was caught near the downstream terminus of the sampling area on Black Creek, following he avy rainfall a time when many species of turtles, including C. serpentina T. carolina and T. scripta tend to make lengthy overland movements (B. Atkinson, pers. obs). Black Creek feeds directly into Choctawhatchee Bay. The brackish environment of Choct awhatchee Bay serves as a natural barrier to most freshwater turtles. Big Cypress Creek and Seven Runs Creek could be more readily colonized due to the fact that they both feed directly into the river as streams. Dismal Creek is less connected the channe l is not directly linked to the Choctawhatchee River, but the floodplain swamp fluctuates and the wetland matrix offer greater opportunity for migrating/colonization.
71 My study provides an ecological snapshot of four selected freshwater creek communities in the summer of 2008. Major restoration efforts for upland communities are underway; as land cover returns to more natural states the ecosystems species composition may reflect change. The turtles I captured were marked for recapture. A wealth of informati on regarding growth, tag retention, movements, and population estimates may be garnered in the years to come. Data recorded during the course of this study provide a reference point for Nokuse Plantation managers. Long term monitoring of the water quality and freshwater turtle populations is encouraged. Future ecological research should continue to focus on the relationship of primary productivity to freshwater turtle species richness.
72 LIST OF REFERENCES Agassiz L. 1857. Contributions to the natural history of the United States of America. Boston, MA: Little, Brown Publishing. Angelier E. 2003. Ecology of streams and rivers. Enfield, NH: Science Publishers. Allan JD. 1995. Stream ecology: structure and function of running waters. New York, NY: Chapman & Hall. Aresco MJ. 2005. Ecological relationships of turtles in northern Florida lakes: A study of omnivory and the structure of a lake food web (PhD dissertation). Tallahassee, FL: Florida State University. Aresco MJ, Ewert MA Gunzburger MS, et al. 2006. Chelydra serpentina snapping turtle. In: Meylan PA (Ed). Biology and conservation of Florida turtles. Lunenberg, MA: Chelonian Research Monographs No. 3. Aresco MJ and MS Gunzburger. 2007. Ecology and morphology of Chelydr a serpentina in northwestern Florida. Southeastern Naturalist 6 : 435 448. Bartlett RD and Bartlett PP. 2006. Guide and reference to the crocodilians, turtles, and lizards of eastern and central North America (north of Mexico). Gainesville, FL: Universi ty Press of Florida. Berry JF. 1975. The population effects of ecological sympatry on musk turtles in northern Florida. Copeia 1975 : 692 700. Bodie JR. 2001. Stream and riparian management for freshwater turtles. Journal of Environmental Management 62 : 443 455. Bodie JR and Semlitsch RD. 2000. Spatial and temporal use of floodplain habitats by lentic and lotic species of aquatic turtles Oecologia 122 : 138 146. Bodie JR, Semlitsch SD, and Renken RB. 2000. Diversity and structure of turtle assemblag es: Associations with wetland characters across a floodplain landscape. Ecography 23 : 444 456. Browne CL and Hecnar SJ. 2007. Species loss and population structure of freshwater turtles despite habitat protection. Biological Conservation 138 : 421 429. Buhlmann KA and Tuberville TD. 1998. Use of passive integrated transponder (PIT) tags for marking small freshwater turtles. Chelonian Conservation and Biology 3 : 102 104.
73 Burke VJ, Greene JL, and Gibbons JW. 1995. The effect of sample size and study duration on metapopulation estimates for slider turtles ( Trachemys scripta ). Herpetologica 51 : 451 456. Cagle FR. 1939. A system of marking turtles for future identification. Copeia 1939 : 170 173. Carr AF. 1940. A contribution to the herpetology of Flo rida. Gainesville, FL: University of Florida Publication, Biological Science Series, Vol. 3, No. 1. Carr AF. 1952. Handbook of turtles: The turtles of the United States, Canada, and Baja California. Ithaca, NY: Comstock Publishing Associates. Congdon, JD, Greene JL, and Gibbons JW. 1986. Biomass of fresh water turtles: A geographic comparison. American Midland Na turalist 115 : 165 173. Congdon JD, Dunham AE, and Sels RCVL. 1993. Delayed sexual maturity and demographics of Blandings turtles ( Emydoidea blandingii ): Implications for conservation of long lived organisms. Conservation Biology 7 : 826 833. Congdon JD, Dunham AE, and Sels RCVL. 1994. Demography of common snapping turtles ( Chelydra serpentina ): Implications for conservation and management of long lived organisms. American Zoologist 34 : 397 408. Congdon JD and JW Gibbons. 1996. Structure and dynamics of a turtle community over two decades. In: Cody, ML and JA Smallwood (Eds). Long term studies of vertebrate communities. San Diego, CA: Academic Press. Conner CA, Douthitt BA, and Ryan TJ. 2005. Descriptive ecology of a turtle assemblage in an urban landscape. American Midland Naturalist 153 : 428 435. Cushing CE and Allan JD. 2001. Streams: Their ecology and life. San Diego, CA: Academic Press. Dodd CK. 1990. Effects of habitat fragmentation on a stream dwelling species, the flattened musk turtle Sternotherus depressus Biological Conservation 54 : 33 45. Dodd CK, Barichivich WJ, Johnson SA, and Staiger JS. 2007. Changes in a northwestern Florida gulf coast herpetofaunal community over a 28 yr period. American Midland Naturalist 158 : 29 48. DonnerWright DM Bozek MA, Probst JR and Anderson EM 1999. Responses of turtle assemblage to environmental gradients in the St. Croix River in Minnesota and Wisconsin, USA. Canadian Journal of Zoology 77 : 989 1000.
74 Dreslik MJ, Kuhns AR, and Phillips CA. 2005. Structure and composition of a southern Illinois freshwater turtle assemblage. Northeastern Natural ist 12 :173 186. Dunson WA and Travis J. 1991. The role of abiotic factors in community organization. The American Naturalist 138 : 1067 1091. Elbin SB and Burger J. 1994. In my experience: Implantable microchips for individual identification in wild and captive populations. Wildlife Society Bulletin 22 : 677 683. Enge KM and Wallace GE. 2008. Basking survey of Barbours map turtle ( Graptemys barbouri ) in the Choctawhatchee and Ochlokonee Rivers, Florida and Alabama. Florida Scientist 71 : 310 322. Ewe rt MA and Nelson CE. 1991. Sex determination in turtles: Diverse patterns and some possible adaptive values. Copeia 1991 : 50 69. Folkerts GW. 1968. Food habits of the stripe necked musk turtle, Sternotherus minor peltifer [Smith and Glass]. Journal of Herpetology 2 : 171 173. Galbraith DA, Bishop CA, Brooks RJ, et al. 1988. Factors affecting the density of populations of common snapping turtles ( Chelydra serpentina serpentina ). Canadian Journal of Zoology 66 : 1233 1240. Gatten RE. 1984. Aerobic and a naerobic metabolism of freely diving loggerhead musk turtles ( Sternotherus minor ). Herpetologica 40 : 1 7. Gibbons JW. 1987. Why do turtles live so long? BioScience 37 : 262 269. Gibbons JW. 1990. Life history and ecology of the slider turtle. Washington, DC: Smithsonian Institution Press. Gibbons JW, Scott DE, Ryan TR, et al. 2000. The global decline of reptiles, dj vu amphibians. Bioscience 50 : 653 666. Gibbons JW and Andrews KM. 2004. PIT tagging: Simple technology at its best. BioScience 54 : 4 47 454. Gorman OT and Karr JR. 1978. Habitat structure and stream fish communities. Ecology 59 : 507 515. Heinrich GL, Walsh TJ, Mattheus NM, et al. (in press). Discovery of a modern day midden: Continued exploitation of the Suwannee cooter, Pseudemys c oncinna suwanniensis, and implications for conservation. Florida Scientist
75 Huestis DL and Meylan PA. 2004. The turtles of rainbow run (Marion County, Florida): Observations on the genus Pseudemys Southeastern Naturalist 3 : 595 612. Iverson JB. 1977 Geographic variation in the musk turtle, Sternotherus minor Copeia 1977 : 502 517. Iverson JB. 1982. Biomass in turtle populations: A neglected subject. Oecologia 55 : 69 76. Iverson JB. 1992. Global correlates of species richness in turtles. Herpeto logical Journal 2 : 77 81. Iverson JB and Etchberger CR. 1989. The distributions of the turtles of Florida. Florida Scientist 52 : 119 144. Iverson JB and Meshaka WE. 2006. Sternotherus odoratus common musk turtle or stinkpot. In: Meylan PA (Ed). Bio logy and conservation of Florida turtles. Lunenberg, MA: Chelonian Research Monographs No. 3. Jackson DA, Peres Neto PR, and Olden JD. 2001. What controls who is where in fish communities the roles of biotic, abiotic, and spatial factors. Canadian Jou rnal of Fisheries and Aquatic Sciences 58 : 157 170. Jackson DR. 2005. Rivers and turtles: An interdependence. In: Meshaka WE and Babbit KJ (Eds). Amphibians and reptiles: Status and conservation in Florida. Malabar, FL: Krieger Publishing Company. Jense n JB. 1998. Bait preferences of southeastern United States coastal plain riverine turtles: Fish or fowl ? Chelonian Conservation and Biology 3 :109 111. Johnson and Barichivich. 2004. A simple technique for trapping Siren lacertina Amphiuma means and ot her aquatic vertebrates. Journal of Freshwater Ecology 19 : 263 269. Joyal LA, McColloug M, and Hunter ML. 2001. Landscape ecology approaches to wetland species conservation: A case study of two turtle species in southern Maine Conservation Biology 15 : 1 755 1762. Klemens MW. 2000. Turtle conservation. Washington, DC: Smithsonian Institution Press. Legler JM. 1977. Stomach flushing: A technique for chelonian dietary studies. Herpetologica 33 : 281 284.
76 Lindeman PV. 1999. Surveys of basking map turtle s Graptemys spp in three river drainages and the importance of deadwood abundance Biological Conservation 88 : 33 42. Luiselli L. 2008. Resource partitioning in freshwater turtle communities: A null model meta analysis of available data. Acta Oecolog ica 34 : 80 88. Marchand LJ. 1942. A contribution to a knowledge of the natural history of certain freshwater turtles (MS thesis). Gainesville, FL: University of Florida. Marchand MN and Litvaitis JA. 2004. Effects of habitat features and landscape com position on the population structure of a common aquatic turtle in a region undergoing rapid development Conservation Biology 18 : 758 767. Marion KR, Cox WA, and Ernst CH. 1991. Prey of the flattened musk turtle, Sternotherus depressus Journal of Herp etology 25 : 385 387. McCune B and Grace JB. 2002. Analysis of ecological communities. Gleneden Beach, OR: MjM Software Design Press. McPherson GR and DeStefano S. 2003. Applied ecology and natural resource management. Cambridge, UK: Cambridge Univers ity Press. Means DB. 2000. Southeastern US coastal plain habitats of the plethodontidae. In: Bruce RC, Jager RG, and Houck LD (Eds). The biology of plethodontid salamanders. New York, NY: Kluwer Academic/Plenum Publishers. Merrit RW and Cummins KW. 199 6. An introduction to the aquatic insects of North America. 3 rd Ed. Dubuque, IA: Kendall Hunt Publishing Co. Meylan PA, Stevens CA, Barnwell ME, and Dohm ED. 1992. Observations on the turtle community of Rainbow Run, Marion Co., Florida. Florida Scienti st 55 : 219 228. Meylan PA. 2006. Introduction. In: Meylan PA (Ed). Biology and conservation of Florida turtles. Lunenberg, MA: Chelonian Research Monographs No. 3. Moler PE. 1996. Alligator snapping turtle distribution and relative abundance. Final Rep ort, study number 7544. Florida Game and Fresh Water Fish Commission. Tallahassee, FL. Moll D. 1990. Sizes and foraging ecology in a tropical freshwater stream turtle community. Journal of Herpetology 24 : 48 53. Moll D and Moll EO. 2004. The ecology, exploitation, and conservation of river turtles. New York, NY: Oxford University Press.
77 Moore MJC and Seigel RA. 2006. No place to nest or bask: Effects of human disturbance on the nesting and basking habits of yellow blotched map turtles ( Graptemys flavimaculata ). Biological Conservation 130 : 386 393. Moyle PB and Light T. 1996. Fish invasions in California: Do abiotic factors determine success? Ecology 77 : 1666 1670. Page LM and Burr BM. 1991. A field guide to freshwater fishes of North America north of Mexico. Boston, MA: The Peterson Field Guide Series, Houghton Mifflin Co. Pennak RW. 1989. Fresh water invertebrates of the United States: Protozoa to mollusca. 3 rd Edition. Hoboken, NJ: Wiley Interscience. Pope CH. 1939. Turtles of the Unit ed States and Canada. New York, NY: Alfred A. Knopf, Inc. Pough FH, Andrews RM, Cadle JE, et al. 2002. Herpetology. 3 rd Edition. Upper Saddle River, NJ: Prentice Hall. Pritchard PCH. 1979. Encyclopedia of Turtles. Neptune City, NJ: TFH Publishing. Reese DA and Welsh HH. 1998. Habitat use by western pond turtles in the Trinity River, California. Journal of Wildlife Management 62 : 842 853. Rizkalla CE and Swihart RK. 2006. Community structure and differential responses of aquatic turtles to agricu lturally induced habitat fragmentation. Landscape Ecology 21 : 1361 1375. Runyan AL and Meylan PA. 2005. PIT Tag Retention in Trachemys and Pseudemys Herpetological Review 36 : 45 47. Scott NJ and Campbell HW. 1982. A chronological bibliography, the hi story and status of studies of herpetological communities, and suggestions for future research. In: Norman J. Scott Jr. (Ed). Herpetological communities: a symposium of the Society for the Study of Amphibians and Reptiles and the Herpetologists' League. August 1977. Washington, DC: US Dept. of the Interior, Fish & Wildlife Service. Smith GR, Iverson JB, and Rettig JE. 2006. Changes in a turtle community from a northern Indiana lake: A long term study. Journal of Herpetology 40 : 180 185. Stone PA, Hauge JB, Scott AF, et al. 1993. Temporal changes in two turtle assemblages. Journal of Herpetology 27 : 13 23. Tavano JJ. 2008. Spatial ecology and demographics of Sternotherus odoratus (Testudines: Kinosternidae) in an Ozark stream (MS thesis). Gainesville, FL: University of Florida.
78 Thomas RB. 2006. Trachemys scripta slider or yellow bellied slider. In: Meylan PA (Ed). Biology and conservation of Florida turtles. Lunenberg, MA: Chelonian Research Monographs No. 3. Zappalorti RT and Iverson JB. 2006. S ternotherus minor loggerhead musk turtle. In: Meylan PA (Ed). Biology and conservation of Florida turtles. Lunenberg, MA: Chelonian Research Monographs No. 3. Zug GR, Vitt LJ, and Caldwell JP. 2001. Herpetology. 2 nd Edition. San Diego (CA): Academic P ress.
79 BIOGRAPHICAL SKETCH Ben Atkinson was born in Butler, Pennsylvania. His father, David is a machinist in a diesel locomotive plant and his mother, Gwen teaches fourth grade. He has one brother, Tim who is a marketing manager for a sp orting goods company. Ben graduated from Butler County Community College in 2001 and went on to earn a Bachelor of Science degree in environmental education at Slippery Rock University in 2004. He accepted internships with Heinrich Ecological Services (St. Petersburg, Florida) and the Wetlands Institute (Stone Harbor, New Jersey). Before entering graduate school at the University of Florida he was a resident at the Chelonian Research Institute in Oviedo, FL where he worked with turtle conservationist Dr. Pe ter Pritchard. He received his Master of Science degree in interdisciplinary ecology in 2009. Ben is continuing his graduate studies at the University of Florida, as a doctoral student in the Department of Wildlife Ecology and Conservation. His career goal s include securing a college teaching position and spearheading a conservation based research program for undergraduates. He lives in Keystone Heights, FL with his partner, Meaghan, and their dog, Marley.