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Relationships Between Small Bodied Fishes and Crustaceans and Submersed Aquatic Vegetation

Permanent Link: http://ufdc.ufl.edu/UFE0041392/00001

Material Information

Title: Relationships Between Small Bodied Fishes and Crustaceans and Submersed Aquatic Vegetation Implications of Habitat Change
Physical Description: 1 online resource (79 p.)
Language: english
Creator: Camp, Edward
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: coastal, fish, macroinvertebrates, throwtraps, vegetation
Forest Resources and Conservation -- Dissertations, Academic -- UF
Genre: Fisheries and Aquatic Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Alterations of aquatic habitats can have profound consequences on the abundances and distributional patterns of associated faunal organisms. Recognition of this fact has motivated multiple state and federal agency initiatives related to habitat management, and encouraged a mechanistic understanding of plant-animal relationships vital for assessing ecological change. I investigated relationships between specific aquatic habitat types (submerged aquatic vegetation, SAV) and small bodied fish and macroinvertebrates (SFI) in the Chassahowitzka and Homosassa rivers; spring-fed rivers along the west coast of peninsular Florida. A decade of research in these rivers indicates a shift in the SAV communities within each of these systems, with decreases in rooted macrophytes (e.g., Vallisneria americana and Sagittaria kurziana) and concomitant increases in the relative abundance of nuisance filamentous macroalgae. To assess how these shifts in SAV might affect the SFI community I: (1) determined if SFI assemblages differed between specific types of SAV, (2) analyzed a suite of response variables to investigate how SFI size groups and species used SAV habitat types, and (3) made comparisons of SFI abundances between similar systems characterized by dissimilar SAV habitat to infer habitat requirements. I sampled SFI associated with five SAV habitat types. My results suggest that both SFI density and species composition were significantly related to SAV habitat type. Contrary to common perception, overall SFI densities were generally highest in filamentous macroalgae. However, SFI species diversity was lower in filamentous macroalgae in comparison to rooted macrophytes. Additionally, I found the densities of specific size classes and taxa of SFI to differ significantly between SAV habitat types, with larger individuals associated with rooted macrophytes. These findings, in combination with the available longer-term monitoring data, provide insight into how continued shifts in SAV may affect the structure and function of Florida?s spring-fed rivers and other aquatic ecosystems. This information is essential for understanding how habitat-animal relationships impact the ecology of an ecosystem undergoing broad-scale habitat change, and may be useful to managers as a decision support tool.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Edward Camp.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Pine, William.
Local: Co-adviser: Frazer, Tom K.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041392:00001

Permanent Link: http://ufdc.ufl.edu/UFE0041392/00001

Material Information

Title: Relationships Between Small Bodied Fishes and Crustaceans and Submersed Aquatic Vegetation Implications of Habitat Change
Physical Description: 1 online resource (79 p.)
Language: english
Creator: Camp, Edward
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2010

Subjects

Subjects / Keywords: coastal, fish, macroinvertebrates, throwtraps, vegetation
Forest Resources and Conservation -- Dissertations, Academic -- UF
Genre: Fisheries and Aquatic Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Alterations of aquatic habitats can have profound consequences on the abundances and distributional patterns of associated faunal organisms. Recognition of this fact has motivated multiple state and federal agency initiatives related to habitat management, and encouraged a mechanistic understanding of plant-animal relationships vital for assessing ecological change. I investigated relationships between specific aquatic habitat types (submerged aquatic vegetation, SAV) and small bodied fish and macroinvertebrates (SFI) in the Chassahowitzka and Homosassa rivers; spring-fed rivers along the west coast of peninsular Florida. A decade of research in these rivers indicates a shift in the SAV communities within each of these systems, with decreases in rooted macrophytes (e.g., Vallisneria americana and Sagittaria kurziana) and concomitant increases in the relative abundance of nuisance filamentous macroalgae. To assess how these shifts in SAV might affect the SFI community I: (1) determined if SFI assemblages differed between specific types of SAV, (2) analyzed a suite of response variables to investigate how SFI size groups and species used SAV habitat types, and (3) made comparisons of SFI abundances between similar systems characterized by dissimilar SAV habitat to infer habitat requirements. I sampled SFI associated with five SAV habitat types. My results suggest that both SFI density and species composition were significantly related to SAV habitat type. Contrary to common perception, overall SFI densities were generally highest in filamentous macroalgae. However, SFI species diversity was lower in filamentous macroalgae in comparison to rooted macrophytes. Additionally, I found the densities of specific size classes and taxa of SFI to differ significantly between SAV habitat types, with larger individuals associated with rooted macrophytes. These findings, in combination with the available longer-term monitoring data, provide insight into how continued shifts in SAV may affect the structure and function of Florida?s spring-fed rivers and other aquatic ecosystems. This information is essential for understanding how habitat-animal relationships impact the ecology of an ecosystem undergoing broad-scale habitat change, and may be useful to managers as a decision support tool.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Edward Camp.
Thesis: Thesis (M.S.)--University of Florida, 2010.
Local: Adviser: Pine, William.
Local: Co-adviser: Frazer, Tom K.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2010
System ID: UFE0041392:00001


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1 RELATIONSHIPS BETWEEN SMALL BODIED FISHES AND CRUSTACEANS AND SUBMERSED AQUATIC VEGETATION: IMPLICATIONS OF HABITAT CHANGE By EDWARD VINCENT CAMP A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2010

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2 2010 Edward Vincent Camp

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3 To my parents Peter and Marcia, whose unwavering support has enabled me to enjoy pursuing my passions

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4 ACKN OWLEDGMENTS I would like to thank all the members of my supervisory committee for their support and guidance throughout this project. Dr. Bill Pine provided assistance with the study design, and Dr. Tom Frazer was tremendously influential by mentoring my development as an ecologist and a professional. Dr. Christie Staudhammer has been hugely helpful and patient in fostering my understanding of the data analysis components of this project. I would also like to thank the Florida Fish and Wildlife Conservat ion Commission State Wildlife Initiative Grant Program for funding that made this project possible. I am also grateful to my fellow students and co workers. Many people in the FAS program worked in difficult conditions to help collect and process data for this project, including Drew Dutterer, Morgan Edwards, Brandon Baker, and Jared Flowers. I am especially grateful to Jake Tetzlaff who has given me advice and assistance throughout all aspects of this project. Additionally I would like to acknowledge th e impact that Dr. Dorothy Boorse, Warren Colyer, and Jason Robinson have had on the development of my scientific understanding and research interests. Finally, I would like to thank my family and friends and especially Genevieve for understanding and supp orting me over the last several years.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 6 LIST OF FIGURES ................................ ................................ ................................ .......... 8 ABSTRACT ................................ ................................ ................................ ................... 11 CHAPTER 1 GENERAL INTRODUCTION ................................ ................................ .................. 13 Submersed Aquatic Vegetation ................................ ................................ .............. 14 Small bodied fish and Macroinvertebrates ................................ .............................. 15 Research needs and study Objectives ................................ ................................ ... 15 2 EXAMINING RELATIONSHIPS BETWEEN SMALL BODIED FISH AND MACROINVERTEBRATES AND SPECIFIC SAV HABITAT TYPE ........................ 17 Introduction ................................ ................................ ................................ ............. 17 Methods ................................ ................................ ................................ .................. 18 Study Location ................................ ................................ ................................ .. 18 Study Species and Sampling Gear ................................ ................................ ... 19 Sampling Design and Methods ................................ ................................ ......... 19 Analyses ................................ ................................ ................................ ........... 22 Comparisons of overall SFI Dens ity and Diversity among SAV Habitats ... 22 Comparisons of Densities of specific SFI size Classes and Taxa among SAV Habitats ................................ ................................ .......................... 23 Com parisons of specific SFI Taxa Densities between Systems ................. 23 Results ................................ ................................ ................................ .................... 24 Sampling and Catch Estimation ................................ ................................ ....... 24 Comparisons of overall SFI Density and Diversity among Habitats .................. 25 Comparisons of Densities of SFI size Classes and Taxa among Habitats ....... 26 Comparisons of SFI taxa Densities between Systems ................................ ..... 27 Discussion ................................ ................................ ................................ .............. 27 3 SUMMARY A ND CONCLUSIONS ................................ ................................ .......... 70 REFERENCES ................................ ................................ ................................ .............. 74 BIOGRAPHICAL SKETCH ................................ ................................ ............................ 79

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6 LIST OF TABLES Table page 2 1 Specific response variables compared either among SAV habitats, between rivers, or both. ................................ ................................ ................................ ..... 33 2 2 Proportional species compositio n of the Chassahowitzka River June 2008 May 2009 ................................ ................................ ................................ ............ 33 2 3 Proportional species composition of the Homosassa River November 2008 May 2009 ................................ ................................ ................................ ............ 34 2 4 Repeated measures analysis of variance results for overall SFI density per m in the Chassahowitzka river, from June 2008 May 2009 ............................... 34 2 5 Repeated measur es analysis of variance results for overall SFI diversity in the Chassahowitzka river, from June 2008 May 2009 ................................ ........ 34 2 6 Repeated measures analysis of variance results for ln transformed small si zed SFI densities per m in the Chassahowitzka River, from June 2008 May 2009 ................................ ................................ ................................ ............ 34 2 7 Repeated measures analysis of variance results for ln transformed medium sized SFI den sities per m in the Chassahowitzka River, from June 2008 May 2009 ................................ ................................ ................................ ............ 35 2 8 Repeated measures analysis of variance results for ln transformed large sized SFI densities per m in the Chassahowitzka River, from June 2008 May 2009 ................................ ................................ ................................ ............ 35 2 9 Repeated measures analysis of variance results for ln transformed L. parva densities per m in the Chassahowitzka River, from June 2008 May 2009 ....... 35 2 10 Repeated measures analysis of variance results for ln transformed Palaemonetes spp densities per m i n the Chassahowitzka River, from June 2008 May 2009 ................................ ................................ ................................ ... 35 2 11 Repeated measures analysis of variance results for ln transformed Gobiidae densities per m in the Chassahowit zka River, from June 2008 May 2009 ....... 36

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7 2 12 Repeated measures analysis of variance results for ln transformed L. punctatus densities per m in the Chassahowitzka River, f rom June 2008 May 2009 ................................ ................................ ................................ ............ 36 2 13 Results from comparisons between mean densities per m in the 0.05 ................................ ................................ ................................ .................... 36

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8 LIST OF FIGURES Figure page 2 1 Mapping and sample selection are illustrated. ................................ .................... 37 2 2 Recovery probabilities for small fish and macroinvertebrates in 5 specific habitat types. ................................ ................................ ................................ ...... 38 2 3 transformed overall SFI density repeated measures model for Chassahowitzka River ................................ ....................... 39 2 4 Chassahowitzka River ................................ ................................ ........................ 40 2 5 transformed L. parva repeated measures model, Chassahowitzka River ................................ ................................ ........................ 41 2 6 transformed Palaemonetes spp. repeated measures model, Chassah owitzka River ................................ ............................ 42 2 7 transformed L. punctatus model, Chassahowitzka River ................................ ................................ ............ 43 2 8 transformed Gobiidae repeated measures model Chassahowitzka River ................................ ................................ ............. 44 2 9 transformed small SFI repeated measures model Chassahowitzk a River ................................ ................................ ........................ 45 2 10 model, Chassahowitzka River. ................................ ................................ ........... 46 2 11 Pearso repeated measures) model, for the Chassahowitzka River. ............................... 47 2 12 Overall SFI density per m by habitat t ype and months at the Chassahowitzka River, June 2008 May 2009. ................................ ................. 48 2 13 Pairwise comparisons of overall SFI densities per m between SAV habitat types at the Chassahowi tzka River, June 2008 May 2009. Mean and 95% confidence intervals around data are shown. ................................ ..................... 49 2 14 Mean overall SFI diversity per m and one standard deviation are shown b y habitat type and months at the Chassahowitzka River, June 2008 May 2009. ................................ ................................ ................................ .................. 50

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9 2 15 Pairwise comparisons of overall SFI diversity per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. Mean and 95% confidence intervals around data are shown. ................................ ..................... 51 2 16 Mean small SFI density per m and one standard deviation are by habitat type and months at the Chassahowitzka River, June 2008 May 2009. ........... 52 2 17 Pairwise comparisons of small SFI density per m between SAV habitat types at the Ch assahowitzka River, June 2008 May 2009. ................................ 53 2 18 Mean medium SFI density per m and one standard deviation shown by habitat type and months in the Chassahowitzka River, Ju ne 2008 May 2009. ................................ ................................ ................................ .................. 54 2 19 Pairwise comparisons of medium SFI density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. ................................ 55 2 20 Mean large SFI density per m and one standard deviation are shown by habitat type and months in the Chassahowitzka River, June 2008 May 2009. ................................ ................................ ................................ .................. 56 2 21 Pairwise comparisons of large SFI density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. ................................ 57 2 22 Mean L. parva density per m with one standard deviation are shown by habitat type and month at the Chassahowitzk a River, June 2008 May 2009. 58 2 23 Pairwise compariso ns of L. parva density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. ................................ .......... 59 2 24 Mean Palaemonetes spp. density per m and one standard deviation are shown by habitat type and months in the Chassahowitzka River, June 2008 May 2009. ................................ ................................ ................................ ........... 60 2 25 Pairwise comparisons of Palaemonetes spp. density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. .................... 61 2 26 Mean Gobiidae density per m and one standard deviation are shown by habit at type and month in the Chassahowitzka River, June 2008 May 2009. .. 62 2 27 Pairwise comparisons of Gobiidae density per m between SAV habitat types at the Chassahowitz ka River, June 2008 May 2009. ................................ 63 2 28 Mean L. punctatus density per m with one standard deviation shown by habitat type and month in the Chassahowitzka River, June 2008 May 2009. .. 64

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10 2 29 Pairwise comparisons of L. punctatus density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. ................................ 65 2 30 Comparisons of L. parva mean density per m with one standard deviation between the Chassahowitzka and Homosassa rivers cumulative over the months November 2008 May 2009. ................................ ................................ 66 2 31 Comparisons of Palaemonetes spp. mean density per m with one standard deviation between the Chassahowitzka and Homosassa rivers cumulative over the months November 2008 M ay 2009 ................................ .................... 67 2 32 Comparisons of Gobiidae mean density per m with one standard deviation between the Chassahowitzka and Homosassa rivers cumulative over the months Novembe r 2008 May 2009 ................................ ................................ .. 68 2 33 Comparisons of L. punctatus mean density per m with one standard deviation between the Chassahowitzka and Homosassa rivers cumulative over the months November 2008 May 2009. ................................ ................... 69

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11 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 RELATI ONSHIPS BETWEEN SMALL BODIED FISHES AND CRUSTACEANS AND SUBMERSED AQUATIC VEGETATION: IMPLICATIONS OF HABITAT CHANGE By Edward Vincent Camp May 2010 Chair: William Pine Cochair: Thomas Frazer Major: Fisheries and Aquatic Sciences Alterations of aquati c habitats can have profound consequences on the abundances and distributional patterns of associated faunal organisms. Recognition of this fact has motivated multiple state and federal agency initiatives related to habitat management, and encouraged a me c hanistic understanding of plant animal relationships vital for assessing ecological change. I investigated relationships between specific aquatic habitat types (submerged aquatic vegetation, SAV) and small bodied fish and macroinvertebrates (SFI) in the Chassahowitzka and Homosassa ri vers; spring fed rivers along the west coast of peninsular Florida. A decade of research in these rivers indicates a shift in the SAV communities within each of these systems, with decreases in rooted macrophytes (e.g., Vall isneria americana and Sagittaria kurziana ) and concomitant increases in the relative abundance of nuisance filamentous macroalgae. To assess how these shifts in SAV might affect the SFI community I: (1) determined if SFI assemblages differed between speci fic types of SAV, (2) analyzed a suite of response variables to investigate how SFI size groups and species used SAV habitat types, and (3) made comparisons of SFI abundances between similar systems

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12 characterized by dissimilar SAV habitat to infer habitat requirements. I sampled SFI associated with five SAV habitat types. My results suggest that both SFI density and species composition were significantly related to SAV habitat type. Contrary to common perception, overall SFI densities were generally high est in filamentous macroalgae. However, SFI species diversity was lower in filamentous macroalgae in comparison to rooted macrophytes. Additionally, I found the densities of specific size classes and taxa of SFI to differ significantly between SAV habita t types, with larger individuals associated with rooted macrophytes. These findings, in combination with the available longer term monitoring data, provide insight into how continued shifts in SAV may affect fed rivers and other aquatic ecosystems. This information is essential for understanding how habitat animal relationships impact the ecology of an ecosystem undergoing broad scale habitat change, and may be useful to managers as a decision support tool.

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13 CHAPTER 1 GENERAL INTRODUCTION A key goal in the study and management of natural environments is to understand the ecological consequences of habitat alterations (Rosenfeld and Hatfield 2006). To understand these consequences it is useful to characteriz e the relationships between animals and their habitats, and specifically to assess which habitats are required to maintain animal populations (Rosenfeld 2003). Required habitats have been defined as those habitats that are necessary for growth and surviva l of individuals and the persistence of species (Rosenfeld 2003), but in practice required habitats have been often designated as those that animals use or occupy in greater density than other habitats (Rosenfeld and Boss 2001). While patterns of habitat use are likely to provide insufficient to reliably indicate required habitat (Van Horne 1983). Designating habitat requirements from patterns of use alone presumes that an imal species could not persist in habitats other than those they currently use. This presumption has rarely been response to a change in habitat is preferable for determining h abitat requirements, and may validate inferences drawn from habitat use (Van Horne 1983; Rosenfeld 2003). Correspondingly, there is a recognized need for studies combining patterns of habitat use with such direct assessments, such as controlled manipulati ve or natural structure may be impacted by changes in habitat (Hobbs and Hanley 1990; Rosenfeld and Hatfield 2006).

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14 Submersed Aquatic Vegetation Submersed aquatic vegetati on (SAV) is a structural habitat found in aquatic ecosystems that is considered important to many animals (Orth et al. 1984; Heck et al. 1989), and is also perceived to be undergoing widespread changes. A pattern of SAV change observed globally is the dec line in abundance of rooted macrophytes, particularly of grass like species (Hauxwell et al. 2003), and concomitant increases in abundance of filamentous macroalgae (Duarte 1995). These two SAV habitat types exhibit very dissimilar structural composition and life histories (Hughes et al. 2002). Rooted macrophytes are relatively slow growing, long lived species whose varied densities and morphological stem and leaf arrangements generally create heterogeneously structured habitat characterized by larger, di fferently sized interstitial spaces (Duffy and Baltz 1998). In contrast, many filamentous macroalgae have a short life cycle, rapid turnover, and are characterized by dense, fine, similar sized filaments that provide a more homogenously structured habitat characterized by uniformly small interstitial spaces (Dodds and Gudder 1994). Rooted macrophytes are also more resistant to infrequent disturbances, e.g., high flow events, than are filamentous macroalgae, which ma y be removed by such disturbances (Duart e 1995). In contrast, filamentous macroalgae are considered more resilient than rooted macrophytes to anthropogenic related frequent or chronic disturbance, e.g., increased nutrient delivery and decreased water levels. As such disturbances are ongoing, s hifts between rooted macrophytes and filamentous macroalgae are likely to continue. The continuation of these shifts, combined with differences in the structural composition of these two SAV a shift from rooted

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15 macrophytes to filamentous macroalgae will have profound and likely adverse consequences on associated animal communities (Pihl et al. 1995; Wyda et al. 2002). Small bodied fish and Macroinvertebrates Shifts in SAV from rooted macroph ytes to filamentous macroalgae would likely affect epibenthic small bodied fish and macroinvertebrates (hereafter SFI) (Deegan et al 2002). In most freshwater systems, the SFI community is generally composed of small (<60 mm) individuals and plays a key role in food web dynamics. While the SFI community is often abundant in many SAV habitats, it has been found to differ between species of SAV. For example, Troutman et al. (2007) found that densities of small bodied fish differed between three SAV types ( Hydrilla verticillata Sagittaria lancifolia and Eichhornia crassipes ) within the Atchafalaya basin, Louisiana. Similarly, Chick and McIvor (1997) found SFI use to differ between three SAV types ( H. verticillata Potamogeton illinoensis and Panicum hem itomon ) in Lake Okeechobee, Florida. Additionally, SFI communities may differ between differently structured SAV habitats. Numerous studies have shown SAV structural characteristics, specifically size of interstitial spaces, to impact SFI foraging succes s, predation risks, and abundance (Chick and McIvor 1994; Bartholomew et al. 2000; Warfe and Barmuta 2004). The relationships between SAV and SFI and the differences between rooted macrophytes and filamentous macroalgae imply that a shift between these ha bitats will likely impact the SFI community, an impact whic h may alter food web dynamics. Research needs and study O bjectives Despite the potential ecological implications associated with such widely observed changes in SAV, few investigations particularl y in freshwater ecosystems, have examined how the SFI communities may change following the shift from rooted

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16 macrophytes to filamentous macro algae (but see Pihl et al. 1995, Deegan et al. 2002). Such shifts in SAV have been documented over the last severa l decades in a number of (Frazer et al. 2006; Heffernan et al. in press). These river systems historically supported similar, extensive, rooted macrophyte beds (primarily V allisneria americana and Sagi t taria kurziana ) and fish communities (Odum 1957a, b). Currently, these rivers are characterized by having very dissimilar SAV habitat (Notestein et al. 2003; Frazer et al. 2006). Ongoing monitoring efforts in both rivers doc ument that the Chassahowitzka River currently contains declining rooted macrophytes, and increasing filamentous macroalgae and unvegetated substrate, whereas the Homosassa River is comprised almost exclusively of filamentous macroalgae and unvegetated subs trate (Frazer et al. 2006). My objective is to understand how this continued shift from rooted macrophytes to filamentous macroalgae may affect SFI in coastal freshwater rivers by characterizing which SAV habitats are required by the SFI community. To ac complish this, I combine inferences drawn from SFI use of specific SAV habitats in the Chassahowitzka River with inferences drawn from comparisons of habitat specific SFI use between the Chassahowitzka (intact vegetation) and Homosassa (degraded vegetation ) rivers. Specifically, I ask: 1. Does the overall density and diversity of the SFI community differ between SAV habitat types, specifically between rooted macrophytes (notably V. americana filamentous macroalgae, and bare substrate? 2. Do the densities of s pecific size classes and taxa differ between these SAV habitats? 3. Do the densities of key SFI taxa differ among similar habitat types between rivers that differ in respect to SAV?

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17 CHAPTER 2 E XAMINING RELATIONSHI PS BETWEEN SMALL BOD IED FISH AND MACROINVER TEBRATES AND SPECIFI C SAV HABITAT TYPE Introduction Submersed aquatic vegetation (SAV) is a structural habitat found in aquatic ecosystems that is considered important to many animals (e.g, SFI) (Orth et al. 1984; Heck et al. 1989), and is also perceived t o be undergoing widespread changes. A pattern of SAV change observed globally is the decline in abundance of rooted macrophytes, particularly of grass like species (Hauxwell et al. 2003), and concomitant increases in abundance of filamentous macroalgae (D uarte 1995). These two SAV habitat types exhibit very dissimilar structural composition and life histories (Hughes et al. 2002) and are perceived to be used differently by SFI (Heffernan et al. in press) Shifts in SAV from rooted macrophytes to filame ntous macroalgae would likely affect SFI (Deegan et al 2002). T he SFI community has been found to differ between species of SAV (Chick and McIvor 1997; Troutman et al 2007) Additionally, SFI communities may differ between differently structured SAV ha bitats (Chick and McIvor 1994; Bartholomew et al. 2000; Warfe and Barmuta 2004). The relationships between SAV and SFI and the differences between rooted macrophytes and filamentous macroalgae imply that a shift between these habitats will likely impact t he SFI community. Few investigations have examined how SFI communities may change following a shift from roote d macrophytes to filamentous macro algae (but see Pihl et al. 1995; Deegan et al. 2002). Such shifts in SAV have been documented in the Chassaho witzka and the Homosassa rivers (Frazer et al. 200 6; Heffernan et al. in press). T he Chassahowitzka River currently contains declining rooted macrophytes, and increasing

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18 filamentous macroalgae and bare substrate, whereas the Homosassa River is comprised a lmost exclusively of filamentous macroalgae and unvegetated substrate (Frazer et al. 2006). These shifts are discussed in more detail in Chapter 1. In Chapter 2 m y objective is to understand how this continued shift from rooted macrophytes to filamentou s macroalgae may affect SFI in coastal freshwater rivers by characterizing which SAV habitats are required by the SFI community. I examine if the overall density and diversity of the SFI community differ s between specific SAV habitat types, specifically b etween rooted macrophytes (notably V. americana ) filamentous macroalgae, and bare substrate I then determine if the densities of specific size classes and associated taxa differ between these SAV habitats Finally I assess whether the densities of key SFI taxa differ among similar habitat types between rivers that differ in respect to SAV Methods Study L ocation The Chassahowitzka and Homosassa rivers are short (8 and 12 km, respectively), low gradient spring fed rivers on the Gulf coast of peninsular Florida. I conducted my research in the freshwater portions of both rivers, which are similar with respect to their physical (temperature, depth, substrate) and chemical (nutrients, salinity) characteristics, but characterized by markedly different SAV c ommunities (Hoyer et al. 2004; Frazer et al. 2006). Designated as critical habitat areas by the state of Florida, these spring fed coastal rivers support freshwater, oligohaline and marine faunal communities and associated recreational and commercial acti vities. Natural resource management agencies and the general public are concerned that the documented shifts

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19 in SAV habitat may degrade the valuable function of these systems (Hefferenan et al. in press). Study S pecies and S ampling G ear Small fishes and c rustaceans were sampled with a 1 x 1 x 0.75 m throw trap. This gear type was selected due to its proficiency at capturing small bodied (less than 60 mm) fish and invertebrates in both densely vegetated and unvegetated shallow areas (Jordan et al 199 7 ; Ro zas and Minello 1997). To sample sites where water depth exceeded 0.75 m, I created an extension to the trap by attaching a 0.75 m tall, 3 mm mesh net with floats to the top of the throw trap. I removed SFI from the trap using a modified 3 mm mesh bar se ine with dimensions matching those of the interior of the throw trap. Because throw traps very rarely captured larger fish occupying higher trophic levels (Chick and McIvor 1997), all fish captured were included in analyses. However, my samples commonly captured much smaller macroinvertebrates (e.g. amphipods and isopods) that likely occupied lower trophic levels Such smaller macroinvertebrates were not collected or included in these analyses. Commonly captured specie s collected and analyzed as SFI in cluded rainwater killifish ( Lucania parva ), bluefin killifish ( Lucania goodei ) spotted sunfish ( Lepomis punctatus ), Gobiidae species, grass shrimp ( Palaemonetes spp ), blue crab ( Callinectes sapidus ), and crayfish ( Procambarus spp.). Sampling Design and M ethods I sampled the SFI community monthly in the Chassahowitzka River from June 2008 May 2009, and in the Homosassa River from November 2008 May 2009. During these months, SFI were sampled in five specific SAV habitat types: (1) V. americana (2) Potamo geton spp. (3) filamentous macroalgae (multiple species), (4) mix of

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20 filamentous macroalgae and V. americana and (5) unvegetated substrate. To locate and sample these SAV habitats, I mapped available habitat types within two study reaches of each river. Within each reach, I selected two transects perpendicular to river flow and subdivided each transect at 5 m intervals to create sub transects extending 5 m upstream and 5 m downstream (parallel to river flow) from the transect (generally 5 to 17 sub tran sects per transect, depending on river width). Along each sub transect, snorkeling gear was used to map and characterize 1 m m intervals ( Figure 2 1 ). To assign sampling sites within study reaches each m onth, I available to sample in each reach, each month, I searched for the remaining sample sites in an additional 5 m upstream and downstream from the mapped areas, and selected the first appropria te sample site s encountered. To sample each of the selected SAV habitat cells, I deployed the throw trap and removed and weighed to the nearest 0.1 kg all above ground SAV material from within the throw trap. Five passes wi th a bar seine were then made to remove SFI from within the trap. The SFI captured in each of the five successive bar seine pass es were removed, placed in a bag, and stored on wet ice. If the first three consecutive passes were completed without recoveri ng a single SFI, the throw trap was considered depleted (Glancy et al 2003) and no further passes were made All SFI samples were transported to a laboratory in ice slurry and frozen within 24 hours of being collected. All individuals were subsequently identified to the lowest taxonomic level possible and measured to the nearest millimeter of total length for fish taxa and carapace length for crustaceans. Thirty individuals of each taxa from each sample were randomly selected

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21 and wet weighed to the near est 0.0001 gram. Samples were then refrozen for future analysis. Because of uncertainty over whether the 5 bar seine passes captured all SFI from each throw trap sample, I compared counts of total SFI, to estimated abundances of SFI from each depletion pa ss using a multinomial depletion approach (Pollock and Gould 1997) as follows: (eq. 1) where LL = log likelihood ln = natural log N = abundance of SFI p = probability of capture, j = pass number, x = total number of passes, C i = in pass j, x ) = Gamma function which is used to scale factorials of large numbers, Q = 1 j=1 to x [p(1 p) j 1 ]. If estimated catch exceeded the observed catch, confidence intervals around the catch estimate were calculated. If the upper confidence i ntervals of the estimate exceeded observed catch by >5% (indicative of the total catch not representing all SFI, 5%), the estimated catch was used for further analysis The multinomial depletion estimates were also used to estimate and compare capture probability between specific SAV habitats.

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22 Analyses Comparisons of overall SFI D ensity and D iversity among SAV H abitats To assess if the SFI community differed between SAV habitat types within a system, I examined two SFI response m etrics -overall density and species diversity. Overall density was measured as the total number of SFI individuals per m species diversity as follows : (2) w here s = Number of species p i = Proportion of total sample belonging to i th species rare species (Peet 1974; Kwak and Peterson 2007). I analyzed dif ferences in SFI density and diversity using repeated measures analysis of variance (ANOVA) with the SAS procedure PROC GLIMMIX ( SAS, version 9.2). The ANOVA assumptions of homoscedastic variance and normally distributed residuals were assessed with plots of residual versus predicted values. When assumptions were not met, I transformed the response variable by taking the natural log (ln) of each. For each SFI response metric ANOVA, fixed effects were SAV habitat type, month, and reach, and all interaction s between these terms. To properly account for autocorrelation between monthly measures of SFI per SAV habitat type, a random effect was included to group measurements in each reach by transect combination. If the SAV habitat type effect was significant ( p 0.05) in the repeated measures ANOVA, I used Tukey HSD (honestly significant differences) tests to determine differences in the mean SFI

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23 response metric between pre planned comparisons of the SAV habitat types V. americana, filament ous macroalgae, and bare substrate. Vallisneria americana was chosen to represent the rooted macrophytes due to its availability at study reaches throughout the study period. I assessed statistical significance using p 0.05, but a lso considered statistically insignificant differences for ecological importance. Comparisons of Densities of specific SFI size Classes and Taxa among SAV H abitats To determine how SFI size and species might differ between SAV habitat types, I investigated the density of specific SFI size classes and taxa as seven additional response variables (Table 2 1). I analyzed densities of small (0 25 mm), medium (26 50 mm) and large (>50 mm) size classes of SFI, inclusive of all taxa I also analyzed the densities of L. parva Palaemonetes spp., Gobiidae, and L. punctatus regardless of size. These species were chosen to represent different guilds of the SFI community L. parva was the most ubiquitous, small fish species, Palaemonetes spp. were the most abundant cr ustacean species, L. punctatus was the most common larger SFI species, and Gobiidae species (multiple genera) were used as characteristic of benthic oriented SFI. Repeated measures ANOVAs and Tukey HSD tests were used as previously described to determine differences in response between SAV habitat types for each of these response metrics, except for density of large sized SFI. A paucity of non zero data for the density of large SFI prevented the random effect from being included in the ANOVA. Comparisons of specific SFI Taxa Densities between S ystems Historically, the Chassahowitzka and Homosassa rivers were thought to support similar SAV, and likely SFI communities (Odum 1957a, b). However, in recent years,

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24 the Homosassa River has undergone significant d eclines in SAV while the Chassahowitzka River has maintained a more intact SAV community (Frazer et al. 2006). Differences in the SAV community and in their associated faunal organisms (Table 2 1) were used to directly assess how SFI are likely to be impa cted by subsequent loss of rooted macrophytes in the Homosassa River. While such a scenario does not constitute a true manipulative experiment, strong inferences can still be drawn from comparisons of the SFI community between these dissimilarly vegetated systems (Rosenfeld 2001). I compared mean densities of L. parva Palaemonetes spp., Gobiidae, and L. punctatus associated with filamentous macroalgae and bare substrate between the Chassahowitzka and Homosassa rivers over the months November 2008 through May 2009. I also examined differences in system wide densities, by comparing the mean densities of each species from all available SAV habitat types between each river. I tested for differences in densities between river systems using a two sample t tes t. Results Sampling and C atch E stimation Vallisneria americana Potamogeton spp., mixed V. americana and filamentous macroalgae, filamentous macroalgae and unvegetated ( bare ) substrate were sampled in the Chassahowitzka River most months ( Potamogeton spp was not present in November 2008 and April 2009). In the Homosassa River, only filamentous macroalgae and unvegetated substrate were available for sampling. I collected a total of 314 throw trap samples containing 32 species (30,410 individuals) from t he aforementioned habitats within the Chassahowitzka River monthly between June 2008 May 2009 From monthly sampling of habitats in the Homosassa River, I collected 40 samples

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25 comprising 17 species (1,769 individuals) monthly November 2008 May 2009. I re port proportional abundance of the ten most abundant species of each river (Tables 2 2 and 2 3), which comprised 97% and 99% of all organisms observed for the Chassahowitzka and Homosassa rivers, respectively. For all habitat types, multinomial depletion estimates of catch were identical to observed catch in nearly every sample, and capture probability was nearly identical betwe en habitat types (Figures 2 2). Therefore I used observed catch for all analyse s. Comparisons of overall S FI Density and Diversit y among H abitats Natural log transformation of overall SFI de nsity resulted in meeting the assumptions of homoscedasticity (Figures 2 3 2 11). The repeated measures ANOVA for ln transformed overall SFI density showed the SAV*month interaction was signif icant (Table 2 4; p 0.05), indicating differences of SFI densities between SAV habitats should be investigated on a month to month basis. Similarly, the analysis for SFI species diversity indicated the SAV*month*reach interaction wa s significant for SFI diversity (Table 2 5; p 0.05). However, because the SFI mean diversity differed between reaches only by magnitude i.e. patterns between SAV habitat types were consistent across sites I focused on differences i n SFI diversity between SAV habitats by month. Both density and diversity of the SFI community differed between SAV habitats. Overall density was greater in all vegetated habitats ( V. americana and filamentous macroalgae) than in bare substrate for most m onths (Figures 2 1 2 and 2 1 3 ). Densities of SFI in filamentous macroalgae were greater than V. Americana when differences occurred between vegetated habitats, (Figures 2 12 and 2 13). Diversity of SFI was greater in vegetated habitats than bare habitat for all months (Figure s 2 14 and 2 15),

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26 with SFI diversity higher in V. americana than filamentous macroalgae for most months when vegetation types differed ( Figures 2 14 and 2 15 ) Comparisons of D ensities of S FI size Classes and Taxa among H abitats Na tural log transforming each of the specific SFI size classes and taxa response metrics (Table 2 1) met model assumptions of homoscedasticity in most cases, as assessed with plots of residuals (Figures 2 5 2 11). For each of these transformed response me trics, the SAV*month interaction term was a significant effect (Tables 2 6 2 12). While the SAV*reach*month interaction was significant for Palaemonetes spp.(Table 2 10), and the SAV*reach interaction was also significant for Gobiidae (Table 2 11), pair wise examinations revealed differences between reach were in magnitude only, and patterns in density by SAV habitat were similar between reaches Therefore, I focused on differences in the SFI size group and species mean densities between SAV habitat type s on a month to month basis. Densities of small SFI, medium SFI, large SFI, L. parva Palaemonetes spp. and L. punctatus were higher in vegetated habitats than bare substrate for most months (Figures 3 6,8 ). Only Gobiidae had consistently similar dens ities between bare and vegetated habitats (Figures 2 26 and 2 27). When densities differed between V. americana and filamentous macroalgae densities of small SFI and L. parva were greater in filamentous macroalgae, whereas densities of larger SFI and L. punctatus were greater in V. americana (Figures 2 16 2 17, 2 20 2 23, 2 28 2 29). Densities of Palaemonetes spp, Gobiidae, and medium sized SFI rarely differed between vegetated habitat types (Figures 2 18 2 19, 2 24 2 27)

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27 Comparisons of SFI t axa Densities between S ystems Differences in SFI densities between the Homosassa and Chassahowitzka rivers varied among key taxa Densities of both L. parva and Palaemonetes spp. in filamentous macroalgae, bare substrate, and pooled from all available SAV habitats were statistically similar between the two rivers (Table 13, Figures 2 30 2 31). However, densities of Palaemonetes spp. were greater in the Chassahowitzka River across all habitat types. Gobiidae densities in filamentous macroalgae were also similar between rivers, but Gobiidae densities associated with bare habitats were significantly greater in the Homosassa River (Table 2 13, Figure 2 32). Cumulative Gobiidae densities from all habitats available were also greater in the Homosassa River ( Table 2 13). Densities of L. punctatus associated with filamentous macroalgae were significantly lower in the Homosassa River compared to the Chassahowitzka River, while densities associated with bare habitat were similar between rivers (Table 2 13, Figur e 2 33). Discussion My results suggest strong associations between SFI taxa and SAV habitats in the Chassahowitzka and Homosassa rivers, and that a shift from rooted macrophytes to filamentous macroalgae will elicit changes in the SFI community. Larger SF I taxa will likely decline following the loss of rooted macrophytes, while some smaller SFI species may flourish in filamentous macroalgae. This use of filamentous macroalgae is surprising. Dominance of filamentous macroalga e however, may precipitate a subsequent shift to bare substrate and elicit additional declines in SFI. Regardless of a subsequent SAV shift, the decline of larger SFI associated with the loss of rooted macrophytes may impact higher trophic levels. Overall, inferences of SAV SFI

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28 rela tionships provided from this study may be useful for identifying broad patterns of chang es occurring in these systems. My results provide two lines of inference regarding the impacts of a shift from rooted macrophytes to filamentous macroalgae on SFI comm unities. Comparisons of SFI communities among SAV habitats in the Chassahowitzka River provided weak inference that overall SFI density, and densities of smaller SFI species, like L. parva and Palaemonetes spp. would not significantly decline following a loss of rooted macrophytes, while overall diversity and density of larger SFI, like L. punctatus would. These comparisons suggest that all SFI, with the exception of Gobiidae, would be negatively affected by a loss of all vegetated habitat (rooted macroph ytes and filamentous macroalgae). Similarly, comparisons of key species densities between the Chassahowitzka and Homosassa r iver s provided stronger inferences that following the loss of rooted macrophytes, L. parva Gobiidae, and Palaemonetes spp. could maintain their populations (with Palaemonetes spp. perhaps suffering slight declines), but that L. punctatus populations would decline to very low abundances. The consistency of the weaker and stronger inferences drawn from my results provides confidence that larger SFI may require rooted macrophytes, smaller SFI may not, but almost all SFI require some vegetated habitat. perceptions of the ecological values of this habitat type (Deeg an et al. 2002, Hughes et al. 2002) providing new insight and understanding. Concern over increasing occurrence of filamentous macroalgae in lotic ecosystems is due, in large part, to the perception that filamentous macroalgae is poor quality habitat for most fish and

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29 invertebrates compared to rooted macrophytes (Paerl 1988). My findings of higher SFI densities in filamentous macroalgae compared to the native rooted macrophyte V. americana are novel, and may be explained by the relationships between inte rstitial space size and size of the SFI in my study. The size of interstitial spaces may affect SFI predation risk (Warfe and Barmuta 2006) and foraging opportunities (Grenouillet and Pont 2001), and small fish have been shown to use habitats proportional to their body size (Bartholomew et al 2000). Accordingly, the small size of L. parva and Palaemonetes spp. may allow them to forage and take refuge in the small interstitial amentous constituting less complex physical structure. Shifts in SAV from rooted macrophytes to filamentous macroalgae may precipitate further complex habitat changes with additional impacts to the SFI community. The life history characteristics of filamentous macroalgae (self shading, short life cycle, and low resilience to stochastic environmental disturbances) predispose this type of SAV to subsequent temporary or permanent shifts to bare substrate (Dodds and Gudder 1994; Duarte 1995; Pihl et al. 1994 ; Valiela et al. 1997). A shift to bare substrate would be expected to elicit wide scale declines in abundance of the SFI community, as shown by this and previous stud ies comparing SFI abundance and vital rates between vegetated to unvegetated habitats (Killgore et al. 1989; Pihl et al. 1995; Jordan 2002 ). Such a decline in most SFI species could also affect higher trophic levels (Rozas and Odum 1987) and possibly lead to cascading responses within these ecosystems (Carpenter and Kitchell 1993)

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30 The decline in larger SFI concurrent with the observed shift from rooted macrophytes to filamentous macroalgae is a key result from this study. By providing recreational fishin g opportunities (Dequine 1950), larger SFI such as L. punctatus are important in and of themselves to these systems. Additionally, these taxa of SFI provide critical larger sized forage for predators, such as largemouth bass, Micropterus salmoides (Tetzla ff 2008). M icropterus salmoides and similar predators may require larger food items to maintain optimal growth rates (Dunlop 2005). Therefore, the decline of larger SFI associated with a loss of rooted macrophytes may negatively impact M. salmoides growt h rates. This is supported by results from Tetzlaff (2008) that showed higher adult M. salmoides growth rates in the Chassahowitzka River compared to the Homosassa River. Taken in concert with my results, these findings suggest a trophic cascade linkage (Carpenter and Kitchell 1993) between SAV habitat and M. salmoides growth, and illustrate that the shift from rooted macrophytes to filamentous macroalgae may have impacts throughout these ecosystems. The shifts in SFI and SAV observed in this study may be part of a broader pattern of declining heterogeneously structured aquatic habitat associated with a shift towards animal communities characterized by lower abundance, less diversity, and/or smaller dominant species. Such changes have been described as a progression towards biotic homogeneity (Airoldi et al. 2008). Biotic homogeneity is defined by McKinney and functional traits and the expansion of few widespread and less complex broadly tolerant species diversity have been documented in a wide variety of ecosystems such as

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31 seagrass beds (Hughes et al. 2002), live bottom communities (Thr ush and Dayton 2002; Coleman and Williams 2002), and nearshore oyster reefs (Coen et al. 1999, Eggleston 1999). The shifts in habitat and associated SFI observed in the Chassahowitzka and Homosassa rivers may represent a similar example of increasing bio tic homogeneity. Rooted macrophytes feature greater interstitial and patch scale heterogeneity than filamentous macroalgae, which provides more structural heterogeneity than bare substrate. Therefore, shifts in habitat from rooted macrophytes to filament ous macroalgae to bare substrate constitute increasing structural homogeneity. My study indicates such a shift would likely cause a decline in SFI abundance, species diversity and abundance of larger species like L. punctatus and the dominance of a few s maller species like L. parva or Gobiidae. The f indings reported here represent one of the first reports of a progression to biotic homogeneity in freshwater systems, and may be useful as a model for describing similar changes in other systems. Alternati ve interpretations of my study results and inferences are possible and should be noted. I relied on observations of the historic similarity and subsequent changes in SAV habitat in the Chassahowitzka and Homosassa rivers to make inferences about SFI habit at requirements. However, other factors unrelated to SAV habitat may have differed between these two rivers, and caused the observed differences in the SFI community. Additional studies will be useful to validate the assumptions of this study and strengt hen inferences. Manip ulative experiments to assess habitat specific SFI survival and growth would provide a mechanistic understanding of why certain SFI species change in response to SAV habitat

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32 alterations. Additionally, a mechanistic understanding woul d further strengthen inferences of how SFI and their predators may be affected by changes in SAV habitat. Finally, meta analyses assessing how other changes in habitat structure have affected associated animals communities in these and other ecosystem s ma y help determine if patterns of biotic homogeneity are occurring in freshwater lotic ecosystems.

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33 Table 2 1. Specific response variables compared either among SAV habitats, between rivers, or both. Response Variable Assessed Density of SFI size class es and taxa among Chassahowitzka SAV habitats Comparisons of certain SFI taxa densities within SAV habitats types between Chassahowitzka and Homosassa r ivers Density of rainwater killifish ( Lucania parva ) Yes Yes Density of grass shrimp ( Palaemonetes s pp.) Yes Yes Density of species of the family Gobiidae Yes Yes Density of species of spotted s unfish ( Lepomis punctatus ) Yes Yes Density of small sized SFI (individuals < 25 mm) Yes No Density of medium sized SFI (individuals 26 50 mm) Yes No Density of large sized SFI (individuals >50 mm Yes No Table 2 2 Proportional species composition of the Chassahowitzka River June 2008 May 2009 Chassahowitzka River Rank Species Proportion 1 Lucania parva 0.560 2 Pal a emonetes spp 0.196 3 Lepomis punct atus 0.054 4 Lucania goodei 0.047 5 Procambarus spp 0.035 6 Menedia b eryllina 0.031 7 Syngnathus scovelli 0.021 8 Grapsidae 0.010 9 Gobiidae 0.008 10 Notropis petersoni 0.008

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34 Table 2 3 Proportional species composition of the Homosassa River November 2008 May 2009 Homosassa River Rank Species Proportion 1 Lucania parva 0.343 2 Grapsidae family 0.178 3 Gob i ida e family 0.152 4 Anchoa mitchilli 0.115 5 P al a emonetes spp 0.101 6 Eucinostomus argenteus 0.051 7 Menedia b eryllina 0.032 8 Calinectes sapidus 0.008 9 Gambusia h olbrookii 0.006 10 Syngnathus scovelli 0.005 Table 2 4 Repeated measures analysis of variance results for overall ln transformed SFI density per m in the Chassahowitzka River from June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Reach 1 10 0.52 0.5207 SAV 4 10 50.73 <.0001 Reach*SAV 4 10 1.17 0.3919 Month 11 34 9.46 <.0001 Reach Month 11 34 1.36 0.2412 SAV Month 42 34 1.82 0.0344 SAV Reach *Month 30 34 0.97 0.4594 Table 2 5 Repeated measures analysis of variance results for overall SFI diversity in the Chassahowitzka River from June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Reach 1 10 2.95 0.1166 SAV 4 10 27.01 <.0001 Reach*SAV 4 10 0.99 0.4582 Month 11 34 1.13 0.3681 Reach Month 11 34 2.80 0.0104 SAV Month 42 34 2.21 0.0096 SAV Reach *Month 30 34 2.17 0.0152 Table 2 6 Repeated measures analysis of variance results for ln transformed small sized SFI densities per m in the C hassahowitzka River, from June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Reach 1 10 2.31 0.1597 SAV 4 10 42.01 <.0001 Reach*SAV 4 10 0.94 0.4796 Month 11 34 7.43 <.0001 Reach Month 11 34 2.14 0.0440 SAV Month 42 34 1.75 0.0483 SAV Reac h *Month 30 34 1.25 0.2609

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35 Table 2 7 Repeated measures analysis of variance results for ln transformed medium sized SFI densities per m in the Chassahowitzka River, from June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Re ach 1 10 0.60 0.4572 SAV 4 10 35.57 <.0001 Reach*SAV 4 10 0.65 0.6378 Month 11 34 15.58 <.0001 Reach Month 11 34 1.54 0.1611 SAV Month 42 34 2.08 0.0151 SAV Reach *Month 30 34 1.13 0.3676 Table 2 8 Repeated measures analysis of var iance res ults for large sized SFI densities per m in the Chassahowitzka River, from June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Reach 1 10 0.00 0.9853 SAV 4 10 0.00 1.000 Reach*SAV 4 10 0.02 0.9988 Month 11 34 0.62 0.8122 Reac h Month 11 34 0.33 0.9791 SAV Month 42 34 75.55 <.0001 SAV Reach *Month 30 34 1.07 0.2876 Table 2 9 Repeated measures analysis of variance results for ln transformed L. parva densities per m in the Chassahowitzka River, f rom June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Reach 1 10 0.20 0.6667 SAV 4 10 52.73 <.0001 Reach*SAV 4 10 1.47 0.2822 Month 11 34 11.42 <.0001 Reach Month 11 34 3.96 0.0010 SAV Month 42 34 2.56 0.0029 SAV Reach *Month 30 34 1.12 0 .3709 Table 2 10 Repeated measures analysis of variance results for ln transformed Palaemonetes spp densities per m in the Chassahowitzka River, from June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Reach 1 10 5.11 0. 0474 SAV 4 10 37.04 <.0001 Reach*SAV 4 10 2.81 0.0846 Month 11 34 15.45 <.0001 Reach Month 11 34 3.45 0.0026 SAV Month 42 34 3.25 0.0003 SAV Reach *Month 30 34 1.96 0.0295

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36 Table 2 11 Repeated measures analysis of va riance results for ln transformed Gobiidae densities per m in the Chassahowitzka River, from June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Reach 1 10 38.25 0.001 SAV 4 10 3.92 0.0363 Reach*SAV 4 10 3.18 0.0628 Month 11 3 4 7.02 <.0001 Reach Month 11 34 5.07 0.0001 SAV Month 42 34 2.61 0.0024 SAV Reach *Month 30 34 2.88 0.0017 Table 2 12 Repeated measures analysis of variance results for ln transformed L. punctatus densities per m in the Chassahowitzka River, from June 2008 May 2009 Effect Num DF Den DF F Value Pr > F Reach 1 10 3.09 0.1094 SAV 4 10 7.14 0.0055 Reach*SAV 4 10 0.19 0.9368 Month 11 34 2.97 0.0072 Reach Month 11 34 1.34 0.2435 SAV Month 42 34 2.38 0.0054 SAV Reac h *Month 30 34 1.26 0.2558 Table 2 13 Results from comparisons between mean densities per m in the 0.05 Comparison Mean CHA Mean HOM t DF p value L. parva macroalgae 46.078 42.500 0.318 21 0.753 L. parva bare substrate 0.564 3.344 1.697 33 0.099 L. parva all habitats 20.288 14.805 1.208 63 0.231 Palaemonetes spp., macroalgae 22.89 10.83 1.513 44 0 .137 Palaemonetes spp., bare substrate 0 1.690 1.067 28 0.2 95 Palaemonetes spp., all habitats 11.298 4.366 1.787 109 0.077 Gobiidae, macroalgae 1.079 8.08 1.972 11 0.074 Gobiidae, bare substrate 0.256 5.897 3.199 28 0.003 Gobiidae, all habitats 0.711 6.536 3.628 40 0.00 1 L. punctatus macroalgae 0.47 4 0.083 2.2793 48 0.027 L. punctatus bare substrate 0.026 0.000 1 38 0.324 L. punctatus all habitats 2.209 0.024 5.9972 177 1.097e 08

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37 Figure 2 1. Mapping and sample selection are illustrated. The white rectangle shows sampling universe per transect. The yellow line shows the transect, the short, red lines are sub transects, shaded polygon represents an example habitat type, such as V. americana Small squares represent actual throw trap sample s.

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38 Figure 2 2. Recov ery probabilities for small fish and macroinvertebrates in 5 specific habitat types. Recovery probabilities are given on the x axis and the probability density function is given on the y axis.

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39 Figure 2 transformed ove rall SFI density repeated measures model for Chassahowitzka River

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40 Figure 2 4. overall SFI diversity repeated measures model for Chassahowitzka River

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41 Figure 2 5. transformed L. parva repeated measur es model, Chassahowitzka River

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42 Figure 2 6. transformed Palaemonetes spp. repeated measures model, Chassahowitzka River

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43 Figure 2 7. transformed L. punctatus model, Chassaho witzka River

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44 Figure 2 8. transformed Gobiidae repeated measures model Chassahowitzka River

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45 Figure 2 9. transformed small SFI repeated measures model Chassahowitzka River

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46 Figure 2 10. Pear model, Chassahowitzka River.

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47 Figure 2 11. repeated measures) model, for the Chassahowitzka River.

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48 Figure 2 12. Overall SFI density per m by habitat type and months at the Chassahowitzka River June 2008 May 2009. Shown with one standard deviation (for clarity). Different letters indicate statistically significant differences (p 0.05), a nd asterisks (*) indicate a habitat was not available for sampling.

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49 Figure 2 13. Pairwise comparisons of overall SFI densities per m between SAV habitat types at the Chassahowitzka River June 2008 May 2009. Mean and 95% confide nce in tervals around data are shown.

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50 Figure 2 14. Mean overall SFI diversity per m and one standard deviation are shown by habitat type and months at the Chassahowitzka River, June 2008 May 2009. Different letters indicate sta tistically significant differences (p 0.05), and asterisks (*) indicate a habitat was not available for sampling.

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51 Figure 2 15. Pairwise comparisons of overall SFI diversity per m between SAV habitat types at the Chassahowitzka Ri ver June 2008 May 2009. Mean and 95% confidence in tervals around data are shown.

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52 Figure 2 16. Mean small SFI density per m and one standard deviation are by habitat type and months at the Chassahowitzka River, June 2008 May 2 009. Different letters indicate statistically significant differences (p .05), and asterisks (*) indicate a habitat was not available for sampling.

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53 Figure 2 17. Pairwise comparisons of small SFI density per m between SAV habitat types at the Chassahowitzka River June 2008 May 2009. Mean and 95% co nfidence intervals around data are shown.

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54 Figure 2 18. Mean medium SFI density per m and one standard deviation shown by habitat type and months in the Chassahowitzka River June 2008 May 2009. Different letters indicate stati stically significant differences (p 0.05), and asterisks (*) indicate a habitat was not available for sampling.

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55 Figure 2 19. Pairwise comparisons of medium SFI density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. Mean and 95% c onfidence in tervals around data are shown.

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56 Figure 2 20. Mean large SFI density per m and one standard deviation are shown by habitat type and months in the Chassahowitzka River, June 2008 May 2009. Different letters indicate statistically significant differences (p 0.05), and asterisks (*) indicate a habitat was not available for sampling.

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57 Figure 2 21. Pairwise comparisons of large SFI density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. Mean and 95% co nfidence intervals around data are show n.

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58 Figure 2 22. Mean L. parva density per m with one standard deviation are shown by habitat type and month at the Chassahowitzka River, June 2008 May 2009. Different letters indicate sta tistically significant differences (p 0.05), and asterisks (*) indicate a habitat was not available for sampling.

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59 Figure 2 23. Pairwise comparisons of L. parva density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. Mean and 95% con fidence intervals around data are shown.

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60 Figure 2 24. Mean Palaemonetes spp. density per m and one standard deviation are shown by habitat type and months in the Chassahowitzka River, June 2008 May 2009. Different letters indi cate statistically significant differences (p 0.05), and asterisks (*) indicate a habitat was not available for sampling.

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61 Figure 2 25. Pairwise comparisons of Palaemonetes spp. density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. Mean an d 95% confidence intervals around data are shown.

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62 Figure 2 26. Mean Gobiidae density per m and one standard deviation are shown by habitat t ype and month in the Chassahowitzka River, June 2008 May 2009. Different letters indic ate statistically significant differences (p 0.05), and asterisks (*) indicate a habitat was not available for sampling.

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63 Figure 2 27. Pairwise comparisons of Gobiidae density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. Mean and 95% co nfidence in tervals around data are shown.

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64 Figure 2 28. Mean L. punctatus density per m with one standard deviation shown by habitat type and month in the Chassahowitzka River, June 2008 May 2009. Different letters indicate sta tistically significant differences (p 0.05), and asterisks (*) indicate a habitat was not available for sampling.

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65 Figure 2 29. Pairwise comparisons of L. punctatus density per m between SAV habitat types at the Chassahowitzka River, June 2008 May 2009. Mean and 95% confidence intervals around data are shown

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66 Figure 2 30. Comparisons of L. parva mean density per m with one standard deviation between the Chassahowitzka and Homosassa rivers cumulative over the months November 2008 May 2009. Asterisks (*) indicate habitat types were not available for sampling. Minus signs ( ) and equal signs (=) represent densities in the Homosassa River were lower than or equal to, respectively, that of the Chassahowitzka River

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67 Figure 2 31. Compariso ns of Palaemonetes spp. mean density per m with one standard deviation between the Chassahowitzka and Homosassa rivers cumulative over the months November 2008 May 2009. Asterisks (*) indicate habitat types were not available for sampling. Minus signs ( ) and equal signs (=) represent densities in the Homosassa were lower than or equal to, respectively, that of the Chassahowitzka.

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68 Figure 2 32. Comparisons of Gobiidae mean density per m with one standard deviation between the Chassahowitzka and Homosassa rivers cumulative over the months November 2008 May 2009. Asterisks (*) indicate habitat types were not available for sampling. Minus signs ( ) and equal signs (=) represent densities in the Homosassa were lower than or equal to, respectively, that of the Chassahowitzka.

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69 Figure 2 33. Comparisons of L. punctatus mean density per m with one standard deviation between the Chassahowitzka and Homosassa rivers cumulative over the months November 2008 May 2009. Asterisks (*) indicate habitat types were not available for sampling. Minus signs ( ) and equal signs (=) represent densities in the Homosassa were lower than or equal to, respectively, that of the Chassahowitzka.

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70 CHA PTER 3 SUMMARY AND CONCLUSI ONS I found SFI taxa were strongly related to SAV habitats in the Chassahowitzka and Homosassa rivers, such that a shift from rooted macrophytes to filamentous macroalgae would likely elicit c hanges in the SFI community. Larger SFI taxa will likely decline following the loss of rooted macrophytes, while some smaller SFI species may flourish in filamentous macroalgae. Dominance of filamentous macroalgal e however, may precipitate a subsequent shift to bare substrate and elicit a dditional declines in SFI. Regardless of a subsequent SAV shift, the decline of larger SFI associated with the loss of rooted macrophytes may impact higher trophic levels in these ecosystems Overall, inferences of SFI/SAV relationships provided from thi s study may be useful for identifying broad patterns of changes occurring in these systems. Both lines of inference (described in detail in Chapter 2) showed consistent impacts of a shift from rooted macrophytes to filamentous macroalgae on SFI communit ies. First, c omparisons of SFI communities among SAV habitats in the Chassahowitzka River provided weak inference that overall SFI density, and densities of smaller SFI species, like L. parva and Palaemonetes spp. would not significantly decline following a loss of rooted macrophytes, while overall diversity and density of larger SFI, like L. punctatus would. Second, comparisons of key species densities between the Chassahowitzka and Homosassa r iver s provided stronger inferences that following the loss o f rooted macrophytes, L. parva Gobiidae, and Palaemonetes spp. could maintain their populations (with Palaemonetes spp. perhaps suffering slight declines), but that L. punctatus populations would decline to very low abundances. The consistency of the wea ker and stronger inferences drawn from my results provides

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71 confidence that larger SFI may require rooted macrophytes, smaller SFI may not, but almost all SFI require some vegetated habitat. My findings that in greater densities than rooted macrophytes are novel and contradicted the common perception that filamentous macroalgae is of little ecological value (Paerl 1988 ; Deegan et al. 2002; Hughes et al. 2002) These unexpected results may be explained by the relationships between interstitial space size of the SAV habitat types and size of the SFI in my st udy. Smaller SFI may use habitat with proportionally smaller interstitial spaces to decrease predation risk and increase foraging opportunities (Bartholomew et al 2000 ; Grenouillet and Pont 2001 ; Warfe and Barmuta 2006 ). Accordingly, the small size of L. parva and Palaemonetes spp. may allow them to forage and take refuge in the small interstitial spaces typical of filamentous macroalgae. The s hift in SAV fr om rooted macrophytes to filamentous macroalgae may precipitate further complex habitat changes with additional impacts to the SFI community. The life history characteri stics of filamentous macroalgae predispose this type of SAV to subsequent temporary or permanent shifts to bare substrate (Dodds and Gudder 1994; Pihl et al. 1994; Duarte 1995 ; Valiela et al. 1997). A shift to bare substrate would be expected to elicit wide scale declines in abundance of the SFI community, which could also affect higher tr ophic levels Such a cascading effect (Car penter and Kitchell 1993) is described in greater detail in Chapter 2 A key result from this study is that the observed shift from rooted macrophytes to filamentous macroalgae was associated with a decline in lar ger SFI. L arger SFI such as L. punctatus are important in and of themselves to these systems ( Dequine 1950)

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72 and provide critical larger sized forage for predators, such as Micropterus salmoides (Tetzlaff 2008). Because M. salmoides and similar predators may require larger food items to maintain optimal growth rates (Dunlop 2005) the decline of larger SFI may negatively impact M. salmoides growth rates. This is supported by results from Tetzlaff (2008) that showed higher adult M. salmoides growth rates in the Chassahowitzka River compared to the Homosassa River. Taken in concert with my results, these findings suggest a trophic cascade linkage (Carpenter and Kitchell 1993) between SAV habitat and M. salmoides growth, and illustrate that the shift from r ooted macrophytes to filamentous macroalgae may have impacts throughout these ecosystems. The shifts in SFI and SAV observed in this study may be part of a broader pattern of increasing biotic homogeneity. Increasing biotic homogeneity is described as t he decline of the structural complexity of habitat, associated with the decline of more specialized native taxa and functional groups and the increase of more tolerant fauna ( McKinney and Lockwood 1999) Biotic homogeneity is described in greater detail i n Chapter 2. In these systems, habitat has shifted from rooted macrophyte (more complex) to filamentous macroalgae (less complex), and may shift further to bare substrate (least complex). My study indicates these shifts will be associated a decline in SF I abundance, species diversity and abundance of larger species like L. punctatus and the dominance of a few smaller species like L. parva or Gobiidae. The se findings represent one of the first reports of a progression to biotic homogeneity in freshwater systems, and may be useful as a model for describing similar changes in other systems. Alternative interpretations of my study results and inferences are possible and should be noted. I relied on observations of the historic similarity and subsequent

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73 ch anges in SAV habitat in the Chassahowitzka and Homosassa rivers to make inferences about SFI habitat requirements. However, other factors unrelated to SAV habitat may have differed between these two rivers, and caused the observed differences in the SFI c ommunity. Additional studies will be useful to validate the assumptions of this study and strengthen inferences. Manipulative experiments to assessing habitat specific SFI survival and growth would provide a mechanistic understanding of why certain SFI s pecies change in response to SAV habitat alterations. Additionally, a mechanistic understanding would further strengthen inferences of how SFI and their predators may be affected by changes in SAV habitat. Finally, meta analyses assessing how other chang es in habitat structure have affected associated animals communities in these and other ecosystem may help determine the if patterns of biotic homogeneity are occurring in freshwater lotic ecosystems.

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74 REFERENCES Airoldi, L., D. Balata and M.W. Beck. 200 8. The gray zone: Relationships between habitat loss and marine diversity and their applications in conservations. Journal of Experimental Marine Biology and Ecology 366: 8 15. Bartholomew, A., R.J. Diaz, and G. Ciccetti. 2000. New dimensionless indic es of foraging success. Marine Ecology Progress Series 206:45 58. Carpenter, S.R., and J.F. Kitchell (eds.). 1993. The Trophic Cascade in Lakes. Cambridge Univ. Press, Cambrid ge England 385 p. Coen, L.D., M.W. Luckenbach, and D.L. Breitburg, 1999. The role of oyster reefs as essential fish habitat: a review of current knowledge and some new perspectives. Pp. 438 454, in L.R. Benaka, editor. Fish habitat: essential fish hab itat and rehabilitation. American Fisheries Society, Symposium 22, Bethesda, Maryland. Chambers, P.A. 1987. Light and nutrients in the control of aquatic plant community structure. II. In situ experiments. Journal of ecology 75: 611 620 Chick, J.H., and C.C. McIvor. 1994. Patterns in the abundance and composition of fishes among beds of different macrophytes: viewing a littoral zone as a landscape. Canadian Journal of Fish and Aquatic Science 51: 2873 2882 Chick, J. H., and C.C. McIvor. 1997. H abitat selection by three littoral zone fishes: effects of predation pressure, plant density, and macrophyte type. Ecology of Freshwater Fish 6: 27 35. Coleman, F.C. and S.L. Williams. 2002. Overexploiting marine ecosystem engineers: Potential conseq uences for biodiversity. TRENDS in Ecology and Evolution 17: 40 44. Deegan, L.A., A. Wright, S.G. Ayvazian, J.T. Finn, H. Golden, R.R Merson, and J. Harrison. Nitrogen loading alters seagrass ecosystem structure and support of higher trophic levels. Aq uatic Conservation: Marine and Freshwater Ecosystems 12: 193 212. Dequine, J.F. 1950. American Fisheries Society 78: 38 41 Dobson, A., D. Lodge, J. Alder, G.S. Cumming, J. Keymer, J. M cGlade, H. Mooney, J.A. Rusak, O. Sala, V. Wolters, D. Wall, R. Winfree, and M.A. Xenopoulos. 2006. Habitat loss, trophic collapse and the decline of ecosystem services. Ecology 87: 1915 1924.

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75 Dodds, W.K., and D.A Gudder. 1992. The ecology of C ladophor a Journal of Phycology 4: 415 427. Duarte, C.M. 1995. Submerged aquatic vegetation in relation to different nutrient regimes. Ophelia 41: 87 112 Duffy, K. C. and D.M Baltz. 1998. Comparison of fish assemblages associated with native and exotic su bmerged macrophytes in the Lake Pontchartrain estuary, USA. Journal of Experimental Marine Biology and Ecology 223: 199 221. Eggleston, D.B., W.E Elis, L.L. Etherington, C.P. Dahlgren, and M.H. Posey. 1999. Organisms response to habitat fragmentations and diversity: Habitat colonization by estuarine macrofauna. Journal of Experimental Marine Biology and Ecology 236: 107 132. Frazer, T.F., W.E. Pine, III, M.V. Lauretta. 2006. Increased nutrient loading of spring fed coastal rivers: Effects on habita t and faunal communities. Florida Fish and Wildlife Conservation Commission Quarterly Report Agreement 07002. Hauxwell, J.A., C.W. Ozenberg and T.K. Frazer. 2004. Conflicting management goals: manatees and invasive competitors inhibit restoration of a native macrophyte. Ecological Applications 14: 571 586. Hobbs, N.T, and T.A. Hanley. Habitat evaluation: Do use/availability data reflect carrying capacity? Journal of Wildlife and Management 54: 515 522. Hughes, J.E., L.A. Deegan, J.C. Wyda, M.J Weaver, and A. Wright. 2002. The effects of eelgrass habitat loss on estuarine fish communities of Southern New England. Estuaries 25: 235 249. Glancy, T.P., T.K. Frazer, C.E. Cichra and W.J. Lindberg. 2003. Comparative patterns of occupancy by dec apod crustaceans in seagrass, oyster, and marsh edge habitats in a northeast Gulf of Mexico estuary. Estuaries 26: 1291 1301. Gould W.R., and K.H. Pollock. 1997. Catch effort maximum likelihood estimation of important population parameters. Canadian Jo urnal of Fisheries and Aquatic Sciences 54: 890 897. Grenouillet, G. and D. Pont. 2001. Juvenile fishes in macrophyte beds: influence of food resources, habitat structure and body size. Journal of Fish Biology 59: 939 959 Jordan, F., S. Coyne and J.C Trexler. 1997. Sampling fishes in vegetated habitats: Effects of habitat structure on sampling characteristics of the 1 m 2 throw trap. Transactions of the American Fisheries Society 126: 1012 1020.

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76 Jordan, F. 2002. Field and laboratory evaluation of habitat use by rainwater killifish (Lucania parva) in the St. Johns River estuary, Florida. Estuaries 25: 288 295. Kemp, W.M., W.R. Boynton, R.R. Twilley, J.C. Stevenson, and J.C. Means. 1983. The decline of submerged vascular plants in Chesapeak e Bay: A summary of results concerning possible causes. Marine Technological Society Journal 17: 78 89 Killgore, K.J, R.P. Morgan II, and N.B. Rybicki. 1989. Distribution and abundance of fishes associated with submersed aquatic plants in the Potomac R iver. North American Journal of Fisheries Management 9: 10:111. Krebs, C.J. 1999. Ecological Methodology. Addison, Wesley, Longman. New York, New York. Kwak, T.J. and J.T Peterson. 2007. Community indices, parameters, and comparisons. Pages 677 763 in C.S. Guy and M.L. Brown, editors. Analysis and interpretation of freshwater fisheries data. American Fisheries Society, Bethesda, Maryland. McKinney, M.L. and J.L. Lockwood. 1999. Biotic homogenization: A few winners replacing many losers i n the next mass extinction. TRENDS in Ecology and Evolution 14: 450 453 Notestien, S.K., T.K. Frazer, M.V. Hoyer, and D.E. Canfield JR. 2003. Nutrient limitation of periphyton in a spring fed, coastal stream in Florida, USA. Journal of Aquatic Plant M anagement 41: 57 60. Odum, H.T. 1957a. Trophic structure and productivity of Silver Springs, Florida. Ecological Monographs 27: 55 112. Odum, H.T. 1957b. Primary production measurements in eleven Florida springs and a marine turtle grass community Limnology and Oceanography 2: 85 97. Orth, R.J., K.L. Heck Jr., and J. Montfrans. 1984. Faunal communities in seagrass beds: A review of the influence of plant structure and prey characteristics on predator: prey relationships. Estuaries 7: 339 35 0. Parker, J.D, J.E. Duffy, and R.J. Orth. 2001. Plant species diversity and composition: experimental effects on marine epifaunal assemblages. Marine Ecology Progress Series 224: 55 67. Peet, R.K. 1974. The measurement of species diversity. Ann ual Review of Ecology and Systematics 5: 285 307. Paerl, H. W. 1988. Nuisance phytoplankton blooms in coastal, estuarine and inland waters. Limnology and Oceanography 33: 823 847.

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77 Pihl, L., H. Wennhage, and S. Nilsson. 1994. Fish assemblage structure in relation to macrophytes and filamentous epiphytes in shallow non tidal rocky and soft bottom habitats. Environmental Biology of Fishes 39: 271 288. Pihl, L., I. Isaksson, H. Wennhage, and P. O. Moksnes. 1995. Recent increase of filamentous algae i n shallow Swedish Bays: Effects on the community structure of epibenthic fauna and fish. Aquatic Ecology 29: 349 358. Raven, J.A. and R. Taylor. 2003. Macroalgal growth in nutrient enriched estuaries: a biochemical perspective. Water, Air, and Soil Pollution 3: 7 26. Rosenfeld, J.S. and S. Boss. 2001. Fitness consequences of habitats use for juvenile cutthroat trout: energetic costs and benefits in pools and riffles. Canadian Journal of Fisheries and Aquatic Sciences 58: 585 593. Rosenfeld, J .S. 2003. Assessing the habitat requirements of stream fishes: An overview and evaluation of different approaches. Transactions of the American Fisheries Society 132: 953 968. Rosenfeld, J.S., T. Leiter, G. Lingder, and L. Rothman. 2005. Food abund ance and fish density alters habitat selection, growth, and habitat suitability curves for juvenile coho salmon (Onchorhynchus kisutch). Canadian Journal of Aquatic Sciences 62: 1691 1701. Rosenfeld J. S. and T. Hatfield. 2006. Information needs for a ssessing critical habitat of freshwater fish. Canadian Journal of Fisheries and Aquatic Sciences 63: 683 699. Rozas, L.P. and T.J. Minello. 1997. Estimating densities of small fishes and decapod crustaceans in shallow estuarine habitats: a review of sampling design and focus on gear selection. Estuaries 20: 199 213. Rozas, L. P. and W.E. Odum. 1988. Occupation of submerged aquatic vegetation by fishes: testing the roles of food and ref uge. Oecologia 77: 101 106 Savino, J.F. and R. A. Stein 1982. Predator Prey interaction between largemouth bass and bluegills as influenced by simulated, submersed vegetation. Transactions of the America Fisheries Society 111: 255 266. Tetzlaff, J.C 2008. Energetic consequences of habitat loss: Trade offs in energy acquisition and energy expenditure by Micropterus salmoides. Masters thesis University of Florida. Gainesville, Florida. Thrush, S.F. and P.K. Dayton. 2002. Disturbance to marine b enthic habitats by trawling and dredging: implications for biodiversity. Annual Reviews of Ecology and Systematics 33: 449 473

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78 Troutman, J. P., D. A. Rutherford, and W. E. Kelso. 2007. Patterns of habitat use among vegetation dwelling littoral fishes i n the Atchafalaya river basin, Louisiana. Transactions of the American Fisheries Society 136: 1063 1075. Twilley, R.R., W.M. Kemp, K.W. Stover, J.C. Stevenson, and W.R. Boynton. Nutrient enrichment of estuarine submersed plant communities. 1 985 Al gal growth and effects on production of plants and associated communities. Marine Ecology Progress Series 23: 179 191. Valiela, I., J. McClelland, J. Hauxwell, P.J. Behr, D. Hersh, and K. Foreman. 1997. Macroalgal blooms in shallow estuaries: Controls and ecophysiological and ecosystem consequences. Limnology and Oceanography 42: 1105 1118. Van Horne, B. 1983. Density as a misleading indicator of habitat quality. Journal of Wildlife Management 47: 893 901. Warfe, D.M. and L.A. Barmuta. 2004. Habitat structural complexity mediates the foraging success of multiple predator species. Oecologia 141: 171 178. Warfe, D.M. and L.A. Barmuta. 2006. Habitat structural complexity mediates food web dynamics in a freshwater macrophyte community. Oecolo gia 150:141 154. Williams, S. W. and K.L. Heck, Jr. 2001. Seagrass Communities, Pp. 317 337 In: M. Bertness, S. Gaines and M. Hay (Eds.), Marine Community Ecology. Sinauer Press, Sunderland, Mass.

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79 BIOGRAPHICAL SKETCH Edward Camp was born in 1983 in Mal den, Massachusetts. He was homeschooled by his parents throughout grade school and was encouraged to explore and study the natural world. In 2001 he graduated from Whitinsville Christian High School and entered Gordon College in Wenham Massachusetts. At Gordon College Edward pursued an interdisciplinary academic track by studying communications, ecology, economics, sociology and political sciences, and studied abroad in N ew Zealand Western Samoa as well as Washington, USA In May 2005 Edward gradu at ed with a degree in e nvironmental studies. In May 2005, Edward moved to Logan, Utah to begin work as a research assistant studying Bonneville Cutthroat trout. Over the next several years Edward worked as a research assistant in Utah, Wyoming, Colorado, New York and Florida and gained experience studying fish and fisheries. Over these years Edward hiked, ran, skied and fished some of the most amazing parts of this country. Upon the completion of his m aster s degree, Edward plans to continue his educat i on by pursuing a Doctor of Philosophy in the study of fisheries. Ultimately Edward is interested in coupling an understanding of fish ecology with social and economic realities to better sustain both the beauty and utility of aquatic ecosystems.