Lake Apopka is located in central Florida about 11 kilometers northwest of Orlando. It covers an area of approximately 125 square kilometers, and is located in both Orange County and Lake County. Before the lake’s marshes were eradicated from the lake it spanned approximately 52,000 acres—after drainage of the marshes it was reduced to 31,000 acres. It is a shallow lake with average depths between 5 and 6 feet, and at present can be classified as a hypereutrophic system (Thomas, 1999).
Disturbance to this system ultimately began in 1880 with the construction of the Apopka-Beauclair Canal. Upon its construction, water leaving Lake Apopka was no longer naturally filtered by the swamp system prior to being introduced into Lake Beauclair. In 1922 a sewage treatment plant began pumping effluent from the town of Winter Garden directly into the lake, and it wasn’t until 1980 that this practice was halted. Coincidentally, a citrus farm began to discharge its wastes directly into Lake Apopka. A drastic change to the lake system occurred in 1941 with the formation of the Zellwood Drainage and Water Control District that was responsible for the construction of a levee built between the lake and the marshes located on the north shore. This sectioned off marshes, which were then drained, exposing the nutrient rich soils for agricultural use. “Muck farms” began establishing themselves around the lake—primarily at the northern shore—and they too discharged wastes directly into the lake.
External nutrient loading—particularly nitrogen (N) and phosphorus (P)—into the system from the surrounding farms eventually led to a massive algal bloom in 1947, which began a transformation of the lake from a macrophyte dominant to a phytoplankton dominant system (Battoe, 1999). An experiment conducted by Dillon and Rigler (1974) suggests a positive correlation between phosphorus concentrations and algal biomass; thus as concentrations of phosphorus increased in Lake Apopka algal biomass also increased.
Many of the fish species native to Lake Apopka began to be replaced by gizzard shad (Dorosoma cepedianum), a species that is more tolerant to pollution (Williams, 1999). Gizzard shad are detritivorous fish, feeding primarily on benthic organic matter—the result of which releases nutrients to the water column that otherwise would remain stored in bottom sediment. Liberated phosphorus can then stimulate the growth of phytoplankton populations, and, consequently, influence water quality giving the lake its now characteristic pea-soup color. Furthermore, releases of nutrients to the system have been found to have a negative affect on species diversity (Schaus et al, 1997).
The farms surrounding Lake Apopka are also responsible for the introduction of many types of pesticides and chemicals into the Lake Apopka system. Compounds like DDT, DDE, dicofol (mixture of the pesticides DDT and DDE), PCB’s, dioxin and diethlstibestrol (DES) contribute to the disruption of the endocrine systems of organisms (Gillis, 1995). Abnormal development of the reproductive system has been observed as a result of the introduction of various compounds (Lebanc, 1998). There have been instances where birds have been born with such severely malformed beaks that they were incapable of eating (Williams, 1999). Alligators have been examined and found to have shrunken penises, and in some instances have possessed both male and female sexual organs.
In 1985 the Lake Apopka Restoration Act was passed by Congress, which provided a source of funding for the restoration of Lake Apopka. Then in 1996 and 1997 Congress passed an act giving the St. Johns Water Management District (SJWMD) the funds and the freedom of action to purchase farm lands located on the north shore of Lake Apopka.
The SJWMD was also given the task of developing a restoration plan for Lake Apopka, and has outlined their restoration intentions with several projects that may help to improve the lake. A significant reduction in phosphorus loading, in order to destabilize algal dominance and encourage a shift towards a macrophyte-dominated community, is essential to the improvement of the lake’s water quality. The surrounding muck farms are the major contributors of phosphorus to the lake—they are responsible for more than 90 percent of the incoming nutrients—therefore the SJWMD has deemed it of the utmost importance that these sources of nutrient inputs be abated or, if possible, altogether stopped (3). Lake Apopka contains high concentrations of nutrients (particularly P) that must be removed from the system. Methods of removal of P are by filtering water through a specially designed wetland called the Marsh Flow-Way, and by the laborious removal of gizzard shad. Also planned for the lake is the recreation of the littoral zone. Jay Polinkas (1999) of the SJWMD states:
“The overall goals of this effort are to, restore the water in Lake Apopka to meet Class III water quality standards, to restore the functional capabilities of the lake's natural systems, to re-establish previous recreational and aesthetic values, and to implement a comprehensive basin management plan.”
Lake Apopka is a hypereutrophic lake with a bottom that is entirely covered by organic sediments. The organic sediments supply a basis for the high turbidity of the lake caused by suspended phytoplankton and surficial sediments (4). The remaining “highland marshes” of Lake Apopka, and other marshes located in the same region, are unstable due to the capacity for extreme variations in subsurface drainageways (Myers et al, 1990). Deevey (1988) studied hydrographs of lakes throughout Central Florida and found that water levels seem to change in unison with each other. This may be attributed to the fact that much of the lakes in Northern and Central Florida respond to variations in the Floridan Aquifer. Lake Apopka overlies both the Fort Preston Formation, and lower marine and estuarine terrace deposits (Vernon et al, 1964). Soils of lower marine and estuarine terrace deposits are alluvium, marl and peat, and sand for the Fort Preston Formation. See Picture 1 for the location of Lake Apopka.
A major disrupter to the Lake Apopka system has been the persistent loading of phosphorus as a result of discharges from muck farms located along the lake. Phosphorus loading supports populations of gizzard shad, which do particularly well in high nutrient waters such as Lake Apopka. This detritivorous fish is a major contributor for the transport of nutrients from the benthic zone to the water column. Benthic foraging by the gizzard shad dislodges nutrients that would otherwise be held in sediment. Some of the nutrients are incorporated into the fish’s body tissue and some is made available to phytoplankton, which has helped change the lake into a hypereutrophic system (Battoe, 1999). Phosphorus inputs need to be greatly reduced, and mass removal of the gizzard shad must occur to help shift the lake to a more stable environment.
Another disruptive agent to the Lake Apopka system has been the release of chemical pollutants from agricultural farms. Discharged chemicals include the organochlorine pesticides DDT, its derivative DDE, dieldrin and aldrin, polychlorinated biphenyls (PCBs), dioxin, dicofol, furans and phthalates (The Lancet, 1995). Studies have repeatedly suggested that many of these pesticide compounds alter the normal functioning of the endocrine system in organisms. This important system controls the release of hormones into the body by various organs and glands such as the pancreas, ovaries and testis, and thyroid, pituitary and adrenal glands—which all act to influence the rate of functioning of almost all the body’s cells. High pesticide levels in Lake Apopka were found in populations of large mouth bass, and tests suggest that increased levels may have a feminizing effect on males. Increased concentrations of estrogen were also found in female populations (Gross, 1995). Similar results were received in a study performed on alligators in Lake Apopka—generally, estrogen concentrations increased, while testosterone concentrations decreased (Gross, 1995). Pesticide introduction into the system must be halted or vastly reduced because it seems likely that prolonged discharges will only continue to threaten populations of organisms tied into the Lake Apopka ecosystem.
With the creation of the Lake Apopka Restoration Council by Florida Legislature in 1985 the St. Johns Water Management District was given the assignment of creating a plan for the restoration of Lake Apopka. In 1985 the Surface Water Improvement and Management Act (SWIM) was passed which instructed SJWMD to implement a plan for Lake Apopka’s restoration. Other organizations have worked, and continue to work, in conjunction with SJWMD, producing studies on various aspects of the lake, and increasing public concern and involvement in the effort. The SJWMD is conducting this restoration project on the lake and its surrounding littoral zone, as well as on the 14,000 acres of drained farmland located on the North Shore (see Picture 1 for drained farmland location). The necessity to restore Lake Apopka lies in the benefits gained from attaining better water quality. Increased water quality will improve the aesthetics of the lake, increase species diversity of both vegetation and plants, and generally create a healthier environment.
There are several stages to the restoration of Lake Apopka, a few of which have already been implemented and completed. The restoration of Lake Apopka by the reduction of pollution was made a primary goal for the SJWMD by the 1985 Lake Apopka Restoration Act and the 1987 Surface Water Improvement and Management Act. An Allowable Waste Load Rule for Lake Apopka was attempted by the SJWMD in 1994, but a ruling by the State of Florida deemed SJWMD did not have the authority to implement such a regulation. The Lake Apopka Restoration Act of 1996 was later passed effectively giving SJWMD the authority to put into practice pollution regulations, as well as allocating to its disposal $20 million towards the purchasing of lakeside farms. Another Florida Legislative program in 1997 also provided additional funding to be used for the buyout of these farms (1). In 1998 approximately 95% of the agricultural farms had been bought, and by spring of the same year construction of the Marsh Flow-Way system was underway (2).
The buyout project is the portion of the restoration plan that will reduce inputs of nutrients to Lake Apopka, but the actual removal of phosphorous from the lake will also be necessary. The Marsh Flow-Way will remove phosphorous from the water by filtering it through 13 marsh “cells”, and redistributing the cleaned water to the lake. The total volume of the lake’s water will be cycled through this system two times a year. Phosphorous and algae will be buried in the marsh sediment by the natural process of vegetation growth and decay (3).
The mass removal of gizzard shad by fishermen, paid for by the St. Johns Water Management District (SJWMD), is another method that has been utilized for the removal of phosphorous from Lake Apopka. This system of phosphorous removal has proved quite successful despite proving to be very expensive and labor intensive (1). Therefore, due to these two reasons, this method will be stopped once population numbers have decreased—making them harder to catch—or when populations of game fish have increased sufficiently.
The importance of littoral zone recreation has been recognized; therefore this aspect of the restoration project involves the planting of native species of vegetation in selected sections of the shore. The SJWMD accomplishes this task by attaching the desired plant to a sand-filled sock, which sinks the invention at the preferred location and allows the plant to take root in the sediment (1).
Through the purchasing of “muck” farms the SJWMD has decreased the discharge of phosphorous into Lake Apopka by as much as 90 percent (3). A press release by SJWMD on October 13th, 1999 stated that due to the restoration effort, involving, in particular, the reduction and removal of phosphorous from Lake Apopka, there appears to have been a 31 percent reduction in phosphorous concentrations since 1995. Also announced was that lake water clarity has also increased by 29 percent since 1995 (8). Additionally, gizzard shad harvesting has been estimated at about 4 million pounds—resulting in the extrication from the Lake Apopka system of about 28,000 pounds of phosphorous contained within the fish—since 1993 (1). The Marsh Flow-Way system removes 30 metric tons of phosphorous per year, and clears the lake’s water by removing a great deal of suspended particles. SJWMD biologists have observed the natural reestablishment of vegetation that has been absent from the lake for many years (1).
The St. Johns Water Management District accumulated about $106 million for the specific use of purchasing farmland. In addition to this amount, $4 million was necessary for the construction of the Marsh Flow-Way, as was approximately the same amount for the harvesting of gizzard shad. The total cost for the restoration of Lake Apopka has been estimated at about $120 million dollars. Some of this money has been, and continues to be used for the clean up of soil severely contaminated by pesticides. This area of the lake had been flooded, shortly after which birds began to die. To prevent further bird kills the area was drained, and tests are being conducted to determine the best way to manage the site.
Such a restoration plan as this one carried out on Lake Apopka can be conducted on other systems with similar problems. A decrease in phosphorous concentration is the result of a reduction in phosphorous loading (Battoe, 1999). Therefore, all that would remain is, basically, the removal of the excess phosphorous from the system.
Any system with exorbitant amounts of phosphorous inputs can be made to have lower concentrations of phosphorous by reducing the inputs of phosphorous into the system (Battoe, 1999). Reducing phosphorous levels can destabilize populations of algae that rely the phosphorous; thus the system can be made to shift towards macrophytic dominance. As Dillon and Rigler (1974) suggest: reduce phosphorous concentrations and algal biomass will also decrease. The removal of gizzard shad would benefit the system by minimizing the release of phosphorous from the benthic zone of the lake permitting its metabolism by algae and phytoplankton (Schaus, 1997).
Some researchers have concluded that contaminants can be held accountable for the adverse affects they have on wildlife as well as on human populations. There have been decreases in sperm count, and increases in incidences of breast and prostate cancer, including other affects on the endocrine system of humans (The Lancet, 1995).
The problems found in Lake Apopka are not limited to this system alone. Poor water quality has become a problem for those lakes and ponds that receive water from the lake via rivers, streams and channels. This alerts one to the fact that any progress toward the restoration of Lake Apopka will also improve surrounding ecosystems that are, no doubt, also of significant importance—since 15 percent of the water leaving the Marsh Flow-Way will travel to downstream systems (2).
The restoration of Lake Apopka appears to have been quite successful if one were to solely regard its improvement as a response to phosphorous reduction and removal, and the reintroduction of a littoral zone. Yet, this is not the end of the Lake Apopka restoration, for the riddance of persistent chemical compounds is the next task that must be initiated. The threat to wildlife and humans is too real, an intense plan to reduce or remove them is essential.
Battoe, L. E., Coveney, M. F., Lowe, E. F., and Stites, D. L. 1999. The Role of Phosphorus Reduction and Export in the Restoration of Lake Apopka, Florida. CRC Press LLC.
Deevey, E. S. 1988. Estimation of downward leakage from Florida lakes. Limnology and Oceanography, 3, 1308-1320.
Dillon, P. J., and F. H. Rigler. 1974. The phosphorous-chlorophyll relationship in lakes. Limnology and Oceanography, V. 19(5).
Gillis, A. M. 1995. What Cautionary Tales Can Lake Apopka Tell? ZooGoer 24(4).
Gross, D. A., T. S. Gross, B. Johnson and L. Folmar. 1995. Characterization of Endocrine-Disruption and Clinical Manifestations in Large-Mouth Bass from Florida Lakes. Society of Environmental Toxicology and Chemistry, Pensacola, FL. Pp. 185.
Gross, T. S., H. F. Percival, K. Rice, C. L. Abercrombie, P. W. Wilkinson, L. Folmar and A. Woodward. 1995. Evaluation of Reproductive Function in Adult Female Alligators from Contaminated and Control Lakes in Florida. Society of Environmental Toxicology and Chemistry, Pensacola, FL. Pp. 184.
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Leblanc, G. A. 1998. The state of the debate: while scientists agree that some synthetic chemicals can mimic hormones, consensus on a course of action remains elusive. Forum for Applied Research and Public Policy, v.13, 3, 6(5).
Luoma, J. R. 1995. Havoc in the hormones (contaminated animal populations exhibit abnormal behavior). Audubon; July-August, v97, n4, p60(8).
Male reproductive health and environmental oestrogens. 1995. The Lancet, April 15, v345, n8955, p933(3).
Myers, R. L. and J. J. Ewel. 1990. Ecosystem of Florida. University of Central Florida Press, Orlando, FL.
Rhew, K., R. M. Baca, C. A. Ochs, and S. T. Threlkeld. 1999. Freshwater Biology. 42, 99-109.
Schaus, M. H. 1997. Nitrogen and phosphorous excretion by detritivorous gizzard shad in a reservoir ecosystem. Limnology and Oceanography, 42(6), 1386-1397.
St. Johns River Water Management District, “Restoring Hope at Lake Apopka.” Florida Naturalist, 3rd Quarter 1999, 8-9.
Thomas, J. 1999. The Story of Lake Apopka—A Historic Review. Florida Naturalist, 3rd Quarter 1999, 6-7.
Toth, L. A. 1993. The Ecological Basis of the Kissimmee River Restoration Plan. Biological Sciences, Vol. 56, No. 1, 25-50.
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(1) http://sjr.state.fl.us/technical/es/ocklawaha/apopka/apopka.html#Gizzard Shad. St. Johns Water Management District, “The Lake Apopka Restoration Project.” March 21st, 2000.
(2) http://sjr.state.fl.us/info/streamln/sp98sln1.htm. St. Johns Water Management District, “Farmland is now becoming a marsh.” Bill Graf. March 20th, 2000.
(3) http://sjr.state.fl.us/info/streamln/su99sln2.htm. St. Johns Water Management District, “Flow-way Allows Nature to Cleanse Lake Apopka.” Hickenlooper, B. March 20th, 2000.
(4) http://www.fola.org/f.hist/lahist.html. Friends of Lake Apopka, “Lake Apopka History.” March 14th, 2000.
(5) http://sjr.state.fl.us/technical/es/ocklawaha/apopka/apopka.html. St. Johns Water Management District, “Lake Apopka Restoration Project.” March 12th, 2000.
(6) http://sjr.state.fl.us/news/apopka/apopupdt.html. St. Johns Water Management District, “Pesticide Analysis.” March 12th, 2000.
(7) http://www.fola.org/e.conc/frmrest.html. Friends of Lake Apopka, “The Restoration Plan.” March 14th, 2000.
(8) http://www.fola.org/e.conc/e.prob/sj101399.html. Friends of Lake Apopka, “Restoration Problems Index.” March 14th, 2000.