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Landscape Diversity: Florida Phosphate Mine Pit Lakes
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Title: Landscape Diversity: Florida Phosphate Mine Pit Lakes
Physical Description: Fact Sheet
Creator: Wilson, Matthew S.
Hanlon Edward A. (Edward Aloysius) 1946-
Publisher: University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS
Place of Publication: Gainesville, Fla.
Publication Date: 2012
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Subjects / Keywords: Phosphate mines and mining -- Environmental aspects -- Florida
Reclamation of land -- Florida
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Abstract: This document contains a synopsis of findings obtained through research funded by the Florida Institute for Phosphate Research (now the Florida Industrial and Phosphate Research Institute) contrasted with limnological studies of natural lakes in central Florida. The audience for this document includes reclamation planners, government regulators, non-governmental organizations, and managers of phosphate mine pit lakes. This document will help them quickly become informed of the published research and characteristics of the phosphate mine pit lakes in Florida."
Acquisition: Collected for University of Florida's Institutional Repository by the UFIR Self-Submittal tool. Submitted by Diana Hagan.
Publication Status: Published
General Note: "SL364."
General Note: "Original publication date May 2012."
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Source Institution: University of Florida Institutional Repository
Holding Location: University of Florida
Rights Management: All rights reserved by the submitter.
System ID: IR00000985:00001

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SL364 Landscape Diversity: Florida Phosphate Mine Pit Lakes1M. Wilson and E.A. Hanlon2 1. This document is SL364, one of a series of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date May 2012. Visit the EDIS website at http://edis.ifas.u.edu 2. M. Wilson, graduate student, Soil and Water Science Department; and E.A. Hanlon, professor, Soil and Water Science Department, Southwest Florida Research and Education Center, Immokalee, FL; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or aliations. U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A&M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Millie Ferrer-Chancy, Interim DeanIntroduction and PurposePhosphate is a critical nutrient for plant growth and an essential component of the fertilizer used in agriculture that helps to sustain the worlds growing population. During 2010, seven mines in Florida produced approximately 10% of the worlds phosphate supply and more than 65% of the phosphate in the United States (USGS 2011). Florida phosphate production depends on strip-mining, which results in the excavation of thousands of acres annually. Removal of the phosphate ore (matrix) from the ground causes a decit in the volume of materials available for land reclamation. Restoring the landscape to near pre-mining elevations necessitates the creation of lakes, and mine pit lakes constitute signicant components of post-phosphate mining landscapes. In 1975, Florida passed laws requiring mandatory reclamation of lands mined for phosphate (FDEP 2006). All lands mined aer June 30, 1975, are subject to mandatory reclamation requirements to return the landscape to a benecial use following mining. e mine reclamation rules acknowledge the necessity of creating lakes and prescribe criteria for their reclamation. Reclaimed phosphate mine pit lakes must be contoured to no steeper than 4 feet horizontal to 1 foot vertical to at least 6 feet in depth below the seasonal low water line. At least 20% of the lake area is required to be less than 6 feet in depth to provide shallow zones for sh bedding. Reclaimed lake shores are required to be constructed such that seasonal uctuations in water levels result in annual drying and wetting of at least 25% of the lake surface area (FDEP 2006). Many of the phosphate pit lakes in Florida were created before the advent of mandatory mine reclamation regulations. ese lakes typically have relatively straight shorelines with relatively steep shoreline slopes and may contain islands of uncontoured mine spoil. As signicant components of the post-mining landscape, these lakes serve multiple functions, including uses for wildlife habitat, boating, shing, water supply, and aesthetic value. A basic understanding of the limnology, water quality considerations, and ecological functions of mine pit lakes will enhance their potential for use. is document contains a synopsis of ndings obtained through research funded by the Florida Institute for Phosphate Research (now the Florida Industrial and Phosphate Research Institute) contrasted with limnological studies of natural lakes in central Florida. e audience for this document includes reclamation planners, government regulators, non-governmental organizations, and managers of phosphate mine pit lakes. is document will help them quickly become informed of the published research and characteristics of the phosphate mine pit lakes in Florida.Natural Florida Lakes SummaryMost natural Florida lakes formed from or were inuenced substantially by dissolution of limestone. Natural Florida lakes are generally shallow (<10m deep), have smooth bottoms, and are usually mixed by wind-action (Boody et al. 1985a; Shannon and Brezonik 1972). Most do not experience stable thermal stratication and development

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2of depressed oxygen concentrations in the bottom waters (anoxic hypolimnia), though many do (Caneld and Hoyer 1988; Shannon and Brezonik 1972). In terms of biological productivity, the majority of natural lakes in Florida could be classied as mesotrophic (intermediate level of biological productivity) to eutrophic (high level of biological produc tivity) (Caneld and Hoyer 1988; Shannon and Brezonik 1972). e high level of biological productivity caused by eutrophic conditions can lead to water quality problems. Severe algal blooms resulting from eutrophic conditions can impact water quality and decrease the value of lakes for shing and recreation. Because eutrophic conditions are oen problematic for water quality, management of most Florida lakes is focused on attaining a trophic state closer to the mesotrophic range. Typically, biological productivity in freshwater systems is limited by the availability of phosphorus. However, many Florida lakes are nitrogen-limited, indicating that sucient phosphorus is present in the system (Caneld and Hoyer 1988).Phosphate Mine Pit Lake MorphologyIn contrast to natural Florida lakes, the shorelines and bottoms of phosphate pit lakes are typically more irregular. Phosphate pit lakes also generally have a smaller surface area and less shallow zone than most natural Florida lakes. Most phosphate mine pit lakes are similar in mean depth to natural Florida lakes (3 m 4 m), though their maximum depth is usually substantially greater (Boody et al. 1985a; Boody et al. 1985b).Thermal Stratication and Development of Hypoxic HypolimniaMost phosphate mine pit lakes develop at least some stratication with regard to temperature and dissolved oxygen (DO) (Boody et al. 1985a; Boody et al. 1985b). Dissolved oxygen is necessary for aerobic aquatic organisms to survive. e main source of lake dissolved oxygen is from photosynthetic activity in the photic zone, though diusion from the atmosphere also contributes a substantial amount of DO (Cole 1994). e lake water is mixed primarily by wind-action, which distributes the dissolved oxygen throughout a portion of the lake. Seasonal stratication of temperature and dissolved oxygen is common for the majority of lakes and reservoirs in the southeastern United States. Stable thermal stratication and development of depressed dissolved oxygen concentrations in the bottom waters are not common in natural Florida lakes partly because of their generally shallow nature (Shannon and Brezonik 1972). Stratication in phosphate mine pit lakes is likely not a function of depth alone and is probably related to irregularities in the lake bottoms. Deeper pockets in the irregular lake bottoms remain outside of prevailing Figure 1. The future shores of a phosphate pit lake during reclamation to contemporary reclamation standards. Slopes on the lake exterior can be no steeper than 4H:1V (4 feet horizontal to 1 foot vertical) to at least 6 feet below the waters surface during seasonal lows. Credits: M. Wilson Figure 2. Phosphate mine pit lake during reclamation. Water levels in this lake are expected to increase by 5 feet following reclamation. The slopes in the foreground have been contoured to reclamation standards. The slopes in the top right have yet to be contoured to reclamation standards. Note the attened platform (middle left), which will be a sh bedding/littoral zone. The inundated areas are the mine pit bottoms and will become the deeper pockets in the lake. Credits: M. Wilson

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3lake-mixing patterns and promote development of hypoxic conditions (Boody et al. 1985b; Rampenthal and Ferraro 1987). Stratication in phosphate mine pit lakes develops in the early spring (March to April) and generally lasts through fall turnover (October) (Boody et al. 1985a; Boody et al. 1985b). Despite the stratication, the majority of water in phosphate mine pit lakes remains oxygenated throughout the year, and average DO concentrations typically remain more than 5 mg/L. DO concentrations in the surcial waters of phosphate mine pit lakes rarely decrease to less than 5.0 mg/L. However, lake-wide DO concentrations may temporarily decrease to less than 5 mg/L aer fall turnover (Boody et al. 1985a). Winter DO depression in phosphate mine pit lakes is not a serious concern as it is in northern lakes since Florida lakes typically do not freeze for any length of time.Physico-Chemical Parameterse physico-chemical characteristics of phosphate mine pit lakes generally fall within the range of variability observed in natural lakes in central Florida (Boody et al. 1985a; Boody et al. 1985b; Pratt et al. 1985; Rampenthal and Ferraro 1987). e pH (a measure of acidity or basicity) is generally lower in phosphate mine pit lakes than in natural lakes in central Florida, and the waters in phosphate mine pit lakes are generally neutral to slightly acidic. e pH of phosphate mine pit lakes appears related to DO concentration, which is consistent with what occurs in natural lakes (Rampenthal and Ferraro 1987). Alkalinity (a measure of waters buering capacity, or capacity to neutralize acidity) is generally estimated as the concentration of calcium carbonate (CaCO3) in milligrams per liter (mg/L). Lake systems with higher alkalinity typically are more resistant to changes in pH (Cole 1994). Alkalinity in phosphate mine pit lakes is typically higher than the minimum standard of 20 mg/L and is generally slightly higher than natural lakes Figure 3. Phosphate mine pit lake (R-14) under construction in 1994 (top) and after reclamation (bottom). The spoil rows in the 1994 photo typically remain following reclamation and are a common bathymetric feature of phosphate mine pit lakes. The areas without spoil rows will become deeper pockets, resulting in a highly irregular lake bottom. Credits: M. Wilson

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4in central Florida (Boody et al. 1985b; Pratt et al. 1985). is nding means that wide pH uctuations in phosphate mine pit lakes should not be a concern. Hardness (a measure of mineral content in water, gener ally calcium and magnesium) is also estimated as the concentration of CaCO3 in mg/L. While it is not harmful to human health, hard water can be problematic for industrial and residential uses. Hardness in the phosphate mine pit lakes is generally higher than in most natural lakes in peninsular Florida (Boody et al. 1985b; Pratt et al. 1985), and phosphate mine pit lakes are classied as moderately hard (75 CaCO3 mg/L equivalent), using the classication scheme employed by the U.S. EPA (US EPA 1986). Hardness of water also aects the solubility and availability of several metals in solution, such as cadmium, chromium, copper, lead, nickel, and zinc. Minerals in hard water form complexes with the metals, resulting in decreased metal bioavailability. Electrical conductivity (EC) is a measure of electrolyte concentrations (or ionic content) in water. Most of the phosphate mine pit lakes have slightly higher EC than natural lakes, and EC is higher in the bottom waters (Boody et al. 1985a; Boody et al. 1985b; Pratt et al. 1985; Rampenthal and Ferraro 1987). Higher EC in the bottom waters may reect the presence of colloidal materials at or near the phosphate mine pit lake bottoms. Concentrations of most cations, such as calcium, magnesium, and sodium, in phosphate mine pit lakes are similar to concentrations observed in natural Florida lakes. e dominant cations in the phosphate mine pit lakes are calcium and magnesium. However, potassium concentrations are lower in phosphate mine pit lakes than in most natural lakes in central Florida (Boody et al. 1985b). Potassium concentrations are also lower in the sediments of the phosphate mine pit lakes. It is not clear what process is responsible for reduced potassium concentrations observed in phosphate mine pit lake waters and sediments, as potassium is a component of many soil minerals. However, potassium can be captured within the structure of expanding clays such as montmorillonite in a process known as potassium xation. Sulfate concentrations are higher in the sediments and the water column of phosphate mine pit lakes. In some phosphate mine pit lakes, sulfate concentrations have been measured at exceptionally high levels (more than 170 mg/L) (Boody et al. 1985b). In water depleted of oxygen (such as occurs in the hypolimnia of many phosphate mine pit lakes) sulfate (SO4 2-) may be reduced to hydrogen sulde H2S, which is a toxic gas that smells like rotten eggs. Produced by the reduction of sulfate, hydrogen sulde ions are quite reactive and may complex with metal ions to form insoluble sulde precipitates. is process could be an eective mechanism for removal of metal ions from the water column. Phosphate mine pit lakes have decreased concentrations of potassium and chloride in the sediments and water column in comparison to natural lakes in central Florida (Boody et al. 1985b; Rampenthal and Ferraro 1987). Fluoride concentrations may be approximately three times higher in phosphate mine pit lakes relative to water from natural lakes in central Florida. However, uoride concentrations observed in phosphate mine pit lakes are consistently less than Floridas Class III water quality standard of 10.0 mg/L (Boody et al. 1985b; FDEP 2010). Water ChemistryFor the rst few months following reclamation, the chemistry of phosphate mine pit lakes enters a transitional stage. During this transitional stage, the waters may be turbid; pH may be low; and the lakes may be high in hardness, conductivity, selenium, aluminum, and magnesium (Pratt et al. 1985). is transitional stage has been observed to aect colonization and community composition patterns of indicator species, such as protozoans. Within two years following reclamation, turbidity and concentrations of aluminum, magnesium, and selenium decrease to levels comparable to natural lakes in central Florida. At this point, protozoan colonization rates and community composition patterns become similar to the rates and composition characteristics observed in natural lakes (Pratt et al. 1985). Based on the limited data available, phosphate mine pit lakes generally have good water quality. However, both natural and phosphate mine pit lakes in central Florida oen exceed Class III water quality standards for one or more contaminants (Boody et al. 1985b; Pratt et al. 1985; Rampenthal and Ferraro 1987). Beryllium concentrations in phosphate mine pit lake sediments were similar to the concentrations observed in natural lakes in central Florida, and phosphate mine pit lake waters did not exceed the Class III standard for beryllium. Concentrations of nickel, silver, zinc, and selenium in phosphate mine pit lake sediments are generally lower than in the natural lakes in central Florida, and phosphate mine pit lake waters typically do not exceed the Class III water quality standards for any of these four contaminants (Rampenthal and Ferraro 1987). Concentrations of manganese appear to be lower in the water column of phosphate mine pit lakes.

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5Barium in phosphate mine pit lake sediments is generally higher than in natural lakes in central Florida. However, barium in the water column of phosphate mine pit lakes is much lower than in natural lakes in the area, suggesting that barium is removed from the water column of phosphate mine pit lakes (possibly via precipitation with SO4 2into barite, which is highly insoluble and has low bioavailability) (Boody et al. 1985a; Boody et al. 1985b; Rampenthal and Ferraro 1987). Aluminum concentrations in phosphate mine pit lake sediments are highly elevated in comparison to sediments from natural lakes, and aluminum concentrations are generally higher in phosphate mine pit lake waters (Pratt et al. 1985; Rampenthal and Ferraro 1987). e concentrations of chromium and arsenic appear to be higher in the sediments of phosphate mine pit lakes relative to other natural lakes in central Florida, and the concentra tions of chromium and arsenic in the water column were observed to be slightly higher than the concentrations found in natural lakes in the region. However, the studies referenced in this paper found that no phosphate mine pit lakes exceeded the Class III water quality standards for either of these two elements (Boody et al. 1985a; Boody et al. 1985b). Some trace metal concentrations may potentially be problematic in phosphate mine pit lakes. For example, cadmium levels are signicantly elevated in phosphate mine pit lake sediments, and there are documented instances where phosphate mine pit lakes have exceeded the Class III water quality standard for cadmium (Rampenthal and Ferraro 1987; Boody et al. 1985a). Iron also appears to be elevated in the sediments of some phosphate mine pit lakes, and occasional instances have been recorded where phosphate mine pit lakes have exceeded the Class III water quality standards for iron. Mercury concentrations in excess of the Class III water quality standard were found in all lakes (natural and phosphate mine pit). Mercury concentrations may be elevated in phosphate mine pit lake sediments relative to natural lakes in central Florida; however, mercury concentrations in the water column were observed to be consistently lower in phosphate mine pit lakes relative to natural central Florida lakes (Rampenthal and Ferraro 1987). Lead concentrations are elevated in sediments from phosphate mine pit lakes. However, lead concentrations observed in the water column were lower than the concentrations observed in natural lakes in central Florida. Using a hardness value of 90 for phosphate mine pit lakes (Pratt et al. 1985), all of the natural and phosphate mine pit lakes analyzed in the studies referenced in this paper (all of which were conducted during the 1980s) exceeded the Class III water quality standard for lead. e reader should keep in mind that in the time since the studies referenced in this paper were conducted, lead concentrations have declined signicantly in waterbodies throughout the United States because of environmental regulations and the removal of lead additives from gasoline. erefore, lead concentrations measured today are likely to be substantially lower in both natural lakes and phosphate mine pit lakes. Physico-chemical interactions between the water column and the lake bottom sediments will likely change with time as organic material accumulates on the phosphate mine pit lake bottoms. Temporally, the organic material on the phosphate mine pit lake bottoms should increase in inuence with regard to exchange of material with the water column relative to the original bottom sediments.Biological Productivity and Trophic StatusBiological productivity in phosphate mine pit lakes shows a relatively strong negative correlation with maximum lake depth (Boody et al. 1985a). e overall greater maximum depths of many phosphate mine pit lakes are caused by deep pockets. ese deep pockets are likely outside of the major lake-mixing patterns and develop stable stratication and anoxic conditions. In turn, the deep pockets then accumulate detrital material and function as nutrient sinks (Boody et al. 1985a; Boody et al. 1985b). Phosphate mine pit lakes are typically mesotrophic to eutrophic, which is consistent with the trophic status of most other Florida lakes (Shannon and Brezonik 1972; Caneld and Hoyer 1988). Algal densities in phosphate mine pit lakes fall within the lower portion of the algal density range established for natural lakes. Phosphate mine pit lakes do not appear to reach their maximum algal growth potential (Boody et al. 1985b). Some of the algal taxa identied in the phosphate mine pit lakes are associated with eutrophic conditions or are responsible for water quality problems. However, these algal taxa are common in natural Florida lakes. Phosphate mine pit lake waters have signicantly higher concentrations of total phosphorus (TP), which is a measure of all phosphorus species (organic and inorganic), and of soluble reactive phosphorus (or ortho-P), which is a measure of the highly bioavailable inorganic soluble form of phosphorus (Boody et al. 1985a; Boody et al. 1985b; Pratt et al. 1985; Rampenthal and Ferraro 1987). Ortho-P is the predominant form of phosphorus in phosphate mine

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6pit lakes. Phosphate concentrations in the phosphate mine pit lakes are high enough that uctuations in phosphorus concentrations do not appear to have an impact on algal productivity. Phytoplankton densities in phosphate mine pit lakes generally correlate higher with nitrogen concentration than with phosphorus concentration (Boody et al. 1985b). Nitrate/nitrite (NO3/NO2) concentrations in the water column of phosphate mine pit lakes are similar to the concentrations found in natural lakes in central Florida (Boody et al. 1985b). Ammonia (NH3) concentrations may be elevated in the water column of phosphate mine pit lakes, and many phosphate mine pit lakes may potentially exceed the Class III water quality standard for un-ionized ammonia (Boody et al. 1985a). Algal abundance in phosphate mine pit lakes may be correlated with the concentration of nitrogen in the sediments and the water column. Nitrogen concentrations in phosphate mine pit lake sediments are very low in comparison to natural lakes in central Florida (Boody et al. 1985b). Despite the possibility of phosphate mine pit lakes being nitrogen-limited, the blue-green algae found to dominate the phosphate mine pit lakes were generally non-N-xing organisms (Boody et al. 1985b). One hypothesis put forward to explain the lack of dominance of N-xing species in the water column is the high NH3 concentrations. Because N-xation is energy-consumptive, N-xation is not metabolically ecient in the presence of high NH3. erefore, another factor, such as a nutrient (e.g., potassium or manganese) or light attenuation, may limit productivity. Interpretation of inorganic N data suggests that phosphate mine pit lake productivity depends on inorganic N that originates from within the lake watershed outside of the lake water column (allochthonous sources). Hydraulic residence time is negatively related to trophic status. Lakes with longer residence times may exhibit decreased productivity relative to phosphate mine pit lakes with shorter hydraulic residence times (Boody et al. 1985a). Most phosphate mine pit lakes likely have not yet reached a steady-state for their water chemistry, nutrient equilibrium, or trophic status (Boody et al. 1985a). Phosphate mine pit lake sediments should function as a net nutrient-sink as detrital material is buried. Nutrient levels in the water column should decrease with increasing lake age until the phosphate mine pit lake and its watershed reach steadystate equilibrium. Once such equilibrium is achieved, the organic material in the sediments should have a stronger inuence on biogeochemical processes within the phosphate mine pit lakes. Additional studies are needed to determine how these processes change as organic material accumulates on the lake bottoms and lake biogeochemistry equilibrates with the phosphate mine pit watershed.Fish and Wildlife Habitate biological communities in phosphate mine pit lakes are likely in a transitional state for several years following reclamation (Pratt et al. 1985). Regardless, an abundance of wading birds, amphibians, and reptiles use phosphate mine pit lake habitats. e studies referenced in this summary indicate that the sh communities in the majority of the phosphate mine pit lakes were similar in species composi tion to previous sheries studies conducted in Florida freshwater systems (Boody et al. 1985a; Boody et al. 1985b). Connecting phosphate mine pit lakes to natural streams may have a positive impact on sh diversity and abundance in the phosphate mine pit lakes. Florida phosphate mine pit lakes are well known for their thriving sport sh populations. Largemouth bass and/or bluegill are oen the dominant sh species in the nearshore community of phosphate mine pit lakes (Boody et al. 1985a; Boody et al. 1985b). Limited data suggest that spawning of largemouth bass is enhanced in phosphate mine pit lakes relative to natural lakes. However, neither largemouth bass nor bluegills grow at a signicantly faster rate in phosphate mine pit lakes as opposed to natural lakes.Radioactive ElementsUranium-238 is enriched in the phosphatic deposits (Hanlon et al. 1988; Guidry et al. 1990), and radium-226 content in sediments from phosphate mine pit lakes is generally higher than in sediments from natural lakes (Boody et al. 1985a). Radium-226 is likely bound to the sediments in phosphate mine pit lakes. e mean radium-226 in the water column of the phosphate mine pit lakes is usually less than concentrations found in natural central Florida lakes and was consistently less than the Class III water quality standard of 5 Picocuries per liter (Pi/L) (Boody et al. 1985a). erefore, it appears unlikely that elevated radium-226 in the sediments of reclaimed phosphate mine pit lakes is a threat to human health. e higher radium-226 concentrations in phosphate mine pit lake sediments may result in considerably higher radon-222 activities (as high as 119 pCi/L) in the water column (Boody et al. 1985b). ere is no Class III water quality standard for radon in Florida (FDEP 2010), though radon is a signicant concern for drinking water.

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7Despite elevated levels of radium-226 in the sediments, radium concentrations are not signicantly higher in above-ground plant tissue collected from phosphate mine pit lakes. However, the roots of cattail plants from phosphate mine pit lakes have signicantly higher radium-226 levels relative to cattail roots from natural lakes (Boody et al. 1985b). Analyses of Asian clam (Corbicula spp.) and multiple sh trophic levels indicate that biomagnication of Ra-226 does not occur in either natural or phosphate mine pit lakes. In fact, sh from natural lakes actually had higher tissue radium-226 concentrations than sh from phosphate mine pit lakes. One interesting nding by Pratt et al. (1985) was that Mosquito fern (Azolla caroliniana Willd.) and some Lemna spp. may hyper-accumulate radium-226. In these plants, radium-226 is taken up and incorporated into living tissues at concentrations far in excess of background concentration. Concentrations of radium-226 in Lemna and Azolla in phosphate mine pit lakes have been observed to exceed background concentrations in the water column by factors of more than 100,000 (Lemna ) and 54,000 (Azolla ). is nding should be investigated further.Morphological Controls on Phosphate Mine Pit Lake FunctionsFrom a nutrient, water quality, radiation, and sh and wildlife perspective, phosphate mine pit lakes are generally equivalent to natural Florida lakes. Most phosphate mine pit lakes appear to fall into the alkaline-clear category per the classication scheme developed by Shannon and Brezonik (1972). is classication is driven by the relatively high levels of calcium, alkalinity, and conductivity. However, the phosphate pit lakes dier from the alkalineclear lakes described by Shannon and Brezonik (1972) in that they appear to have a neutral to slightly acidic pH. SummaryWater quality should be the primary consideration for phosphate mine pit lakes. Eorts to manage these lakes should be focused on reducing productivity and maintaining trophic states closer to the mesotrophic range. Because phosphate mine lakes are in a transitional state following reclamation, phosphate mine pit lakes and their contributing watersheds do not likely reach equilibrium for their water or sediment chemistry at the time of sampling. Additional sampling should be conducted to see whether any dierences can be observed following 25 years of reclamation. In general, the amount of research that has been performed on phosphate mine pit lakes is inadequate to draw strong inferences about their limnology. e trends identied in this paper should be tested with further limnological studies to better rene our understanding of these impor tant components of the post-mining landscapes of central Florida.References and Additional InformationBachmann, R.W., B.L. Jones, D.D. Fox, M. Hoyer, L.A. Bull, and D.E. Caneld. 1996. Relations between Trophic State Indicators and Fish in Florida (U.S.A.) Lakes. Canadian Journal of Fisheries and Aquatic Sciences 53: 842-55. Boody, O.C., IV, C.D. Pollman, G.H. Tourtellotte, R.E. Dickinson, and A.N. Arcuri. 1985a. Ecological Consider ations of Reclaimed Lakes in Central Floridas Phosphate Region Volume I of II. Publ. No. 03-018-029. Bartow, Florida: Florida Institute of Phosphate Research. Boody, O.C., IV, C.D. Pollman, G.H. Tourtellotte, R.E. Dickinson, and A.N. Arcuri. 1985b. Ecological Consider ations of Reclaimed Lakes in Central Floridas Phosphate Region Volume II of II. Publ. No. 03-018-030. Bartow, Florida: Florida Institute of Phosphate Research. Caneld, D.E., Jr. 1981. Chemical and Trophic State Char acteristics of Florida Lakes in Relation to Regional Geology. Final rep. Coop. Fish Wildl. Res. Unit. Univ. Florida, Gainesville. Caneld, D.E., Jr., and M.V. Hoyer. 1988. Regional Geology and the Chemical and Trophic State Characteristics of Florida Lakes. Lake and Reservoir Management 4(1): 21-31. Carlson, R.E. 1977. A Trophic State Index for Lakes. Limnology and Oceanography 22(2): 361-69. Cole, G.A. 1994. Textbook of Limnology. Fourth Edition. Prospect Heights, Illinois: Waveland Press, Inc. Florida Department of Environmental Protection (FDEP). 2010. Surface Water Quality Standards. Florida Administrative Code (F.A.C.) Rule 62-302.

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8Florida Department of Environmental Protection (FDEP). 2006. Mandatory Phosphate Mine Reclamation. Florida Administrative Code (F.A.C.) Rule 62C-16. Gilmour, C.C., E.A. Henry, and R.A. Mitchell. 1992. Sulfate Stimulation of Mercury Methylation in Freshwater Sediments. Environmental Science and Technology 11: 2281-87. Guidry, J.J., C.E. Roessler, W.E. Bolch, J.T. McClave, C.C. Hewitt, and T.E. Abel. 1990. Radioactivity of Foods Grown on Mined Phosphate Lands. Publ. No. 05-028-088. Bartow, Florida: Florida Institute of Phosphate Research. Hanlon, E.A., G.J. Hochmuth, and R.A. Jerez. 1988. Radionuclide Studies. In e Polk County Mined Lands Agricultural Research and Demonstration Project. Publ. No. 03-088-107, edited by D. Shibles and J. Stricker, 64-68. Bartow, Florida: Florida Institute of Phosphate Research. Pratt, J.R., J. Cairns Jr., P.M. Stewart, N.B. Pratt, and B.R. Niederlehner. 1985. Measurement of Recovery in Lakes Following Phosphate Mining Publ. No. 03-045-039. Bartow, Florida: Florida Institute of Phosphate Research. Rampenthal, S.W., and B.A. Ferraro.1987. Water Quality in Central Floridas Mineralized Region. Publ. No. 03-046-052. Bartow, Florida: Florida Institute of Phosphate Research. Shannon, E.E., and P.L. Brezonik. 1972. Limnological Characteristics of North and Central Florida Lakes. Limnology and Oceanography 17(1): 97-110. United States Environmental Protection Agency (US EPA). 1986. Quality Criteria for Water. Oce of Water Regula tions and Standards. Publication No. EPA-440/5-86-001. United States Geological Survey (USGS). 2011. 2010 Minerals Yearbook. Phosphate Rock. Accessed March 20, 2012. http://minerals.usgs.gov/minerals/pubs/commodity/ phosphate_rock/myb1-2010-phosp.pdf.