Studies of the Contamination of Lake Apopka

      The alligator population at Lake Apopka in central Florida declined dramatically between 1980 and 1987. Endocrine-disrupting chemicals and  DDT metabolites have been implicated in the alligators' reproductive failure. The DDT metabolite hypothesis is based largely on the observation of elevated concentrations of p,p-DDE and p,p-DDD in alligator eggs obtained from Lake Apopka in 1984 and 1985. 
      Lake Apopka is significantly contaminated with a variety of chemicals including anthropogenic nutrients, organochlorine pesticides, and multiple congeners of polychlorinated biphenyls(PCBs). 

      According to Thea M. Edwards, Gunnar Toft, and Louis J. Guillette of the Department of Biology in Florida, "Our laboratory has previously documented a number of reproductive abnormalities in alligators from Lake Apopka, compared with alligators captured from Lake Woodruff, a nearby reference lake. We conducted the present study to investigate if another native vertebrate, Gambusia holbrooki (eastern mosquitofish), is similarly affected." So for these researchers to conduct this study, first adult female mosquitofish were collected from Lake Apopka and Lake Woodruff monthly for 16 months in order to document seasonal and lake-associated variation in reproductive patterns. What was found during this study was that in contrast to fish from Lake Woodruff, females from Lake Apopka exhibited earlier and more synchronized spring ovarian recrudescence, increased body size, increased fecundity, increased adjusted hepatic weight, and more extreme fluctuations in muscle estradiol concentrations in most months. Endocrine disruption, consistent with other studies and Lake Apopka's pollution profile, is one explanation for these findings. Other environmental and physiological factors are also addressed. However, the higher fecundity among Apopka females suggests that, unlike Apopka alligators, Apopka mosquitofish are not 
impacted at the population level.


Sources:

Guillette LJ, Jr, Gross TS, Masson GR, Matter JM, Percival HF, Woodward AR. Developmental abnormalities of the gonad and abnormal sex hormone concentrations in juvenile alligators from contaminated and control lakes in Florida. Environ Health Perspect. 1994 Aug;102(8):680–688.

Edwards, Thea M., Louis J. Guillette, and Gunnar Toft. "Seasonal reproductive patterns of female Gambusia holbrooki from two Florida lakes." The Science of the Total Environment 408.7 (2010): 1569+. Health Reference Center Academic. Web. 7 Nov. 2012.

Lake Apopka and its Inhabitants

            Lake Apopka, which is located in Florida, is the third largest lake in the United States. This lake specifically has been studied for several years now because its alligator inhabitants have not been developing correctly sexually. Now researchers want to know why this is happening and how exactly the cause is changing these alligators. The cause for these defects in the alligators of Lake Apopka is the pollution and contaminants in the water from runoff, dumping and chemical spills. 
        In June 2010, the Idaho Academy of Science began an experiment that entailed them screening American alligators for physiological issues stemming from the contaminants of Lake Apopka, Florida. The lab tested these alligators' LDH(hepatic lactate dehydrogenase) levels, GST(glutathione S-transferase), and they also tested to see if there were any fluctuations in aerobic respiration or if there was any heavy metal exposure. The test results showed higher levels of LDH in Lake Apopka Alligators, which suggests that there was more anaerobic respiration. Some of the tests also suggested a possibility of some heavy metal exposure. The GST activity wasn't too different from the control group samples. 
        High levels in LDH usually indicate tissue damage. So the water of Lake Apopka is damaging the tissue of these alligators and also damaging their sexual organs. If we can't begin to control this issue of contaminants in Lake Apopka, the alligators will continue to die off and won't be able to reproduce since they aren't developing correctly.
 






Sources:
Boggs, Ashley, et al. "Screening American alligators, alligator mississippienisis, inhabiting reference and contaminated sites for alterations in normal physiological function." Journal of the Idaho Academy of Science 46.1 (2010): 25. 

Gale Science In Context. Web. 24 Oct. 2012.Rauschenberger, Heath. "The Lake Apopka agreement." Endangered Species Update 24.3 (2007): S16+. Gale Science In Context. Web. 24 Oct. 2012.
  

Reproductive Disorders in Lake Apopka Alligators

        For several years now, scientists have been studying Lake Apopka and its alligator inhabitants. There have been several reports of reproductive disorders in juvenile alligators of Lake Apopka, believed to have been caused by pesticide spills and runoff. These spills have released contaminants into the water that have seemed to disrupt the endocrine systems of these juvenile alligators. Livers from 12 different juvenile female alligators were taken and tested to further expand this study. Contaminants have been found in both the water of the lake, and in the livers of these alligators. 

     Another study was done on Lake Apopka Alligators to further expand this hypothesis. This specific study was used to figure out whether or not bone tissue is a potential target for endocrine system disruptors, such as these water contaminants. Bones from 16 different female juvenile alligators from Lake Apopka and a surrounding control lake were taken and studied, and there were found to be significant differences between the control lake and Lake Apopka. It seems as though the contaminants in Lake Apopka have caused the bones in these alligators to actually become more dense. 

Alligator Hatchling from Lake Apopka, Florida 

Sources:
Jimmy K. Avants, et al. "Persistent Organochlorine Pesticides And Their Metabolites In Alligator Livers From Lakes Apopka And Woodruff, Florida, USA." International Journal Of Environmental Analytical Chemistry 90.2 (2010): 159-170. Academic Search Complete. Web. 7 Oct. 2012.

Louis J. Guillette Jr., et al. "Abnormal Bone Composition In Female Juvenile American Alligators From A Pesticide-Polluted Lake (Lake Apopka, Florida)." Environmental Health Perspectives 112.3 (2004): 359-362. Academic Search Complete. Web. 7 Oct. 2012.