Abnormal Alligators and Organochlorine Pesticides in Lake Apopka, Florida

  • Allan R. Woodward
  • H. Franklin Percival
  • R. Heath Rauschenberger
  • Timothy S. Gross
  • Kenneth G. Rice
  • Roxanne Conrow
Part of the Emerging Topics in Ecotoxicology book series (ETEP, volume 3)


Lake Apopka is a 12,400-ha hypereutrophic lake in central Florida that was the recipient of nutrient and pesticide pollution from adjacent agricultural operations for 50 years. The abnormal American alligator (Alligator mississsippiensis) population in Lake Apopka has been the object of a number of studies including investigations of a population crash, the epidemiology of egg failure, and anomalous endocrine function. Several hypotheses of the causes of these abnormalities have been proposed and examined by multiple research organizations over the past three decades. Initially, organochlorine pesticide (OCP) contamination was considered the most likely factor causing poor reproductive success. DDE concentrations in alligator eggs sampled in 1984–1985 were approximately 4 mg/kg and toxaphene concentrations were approximately 2.5 mg/kg. These levels were known to cause reproductive failure in certain birds. However, transmissible diseases, population age and density, cyanotoxins, nutritional deficiencies, and combinations thereof, were also investigated for their contribution to poor alligator reproductive success. Investigations of an alligator mortality and reproductive failure event on Lake Griffin, a lake similar to Lake Apopka but with lower OCP levels, revealed analogous reproductive abnormalities that were associated with a dietary thiamine deficiency. Thiamine deficiency appeared to be associated with a diet of almost exclusively gizzard shad, which contain thiaminase, an enzyme that breaks down thiamine. OCP contaminants may contribute to these maladies, perhaps through endocrine disruption and increased stress. The findings of the past 30 years of work at Lake Apopka have affected local management decisions as well as policy at the national level.


Thiamine Deficiency Hatch Rate Gizzard Shad Florida Lake Thiamine Level 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We wish to thank the many students and collaborators who have participated in the last 30 years of research at Lake Apopka. Although trying to list their names would take more space than allotted here; and undoubtedly, result in leaving someone’s name unmentioned, the reader may gain an appreciation of the number of dedicated individuals by looking at the coauthors on the many publications devoted to Lake Apopka’s abnormal alligators. Similarly, we wish to recognize the many federal, state, and local agencies and other organizations that have provided support for work during the last three decades through grants and in-kind services. We thank T. O’Meara, J. Berish, B. Crowder, and J. Colvo for providing a critical review of earlier drafts of this chapter. The findings and conclusions in this article do not necessarily represent the views of the US Fish and Wildlife Service, the St. Johns River Water Management District, or the University of Florida.


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Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  • Allan R. Woodward
    • 1
  • H. Franklin Percival
    • 2
  • R. Heath Rauschenberger
    • 3
  • Timothy S. Gross
    • 4
  • Kenneth G. Rice
    • 5
  • Roxanne Conrow
    • 6
  1. 1.Florida Fish and Wildlife Conservation CommissionFish and Wildlife Research InstituteGainesvilleUSA
  2. 2.US Geological Survey, Florida Cooperative Fish and Wildlife Research UnitUniversity of FloridaGainesvilleUSA
  3. 3.US Fish and Wildlife Service, North Florida Ecological Services Field OfficeJacksonvilleUSA
  4. 4.Environmental Resource ConsultantsUniversity of FloridaGainesvilleUSA
  5. 5.US Geological Survey, Southeast Ecological Science CenterGainesvilleUSA
  6. 6.St. Johns River Water Management DistrictPalatkaUSA

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