Sandoval, Christopher Enrique (2017-08). Persistent Organic Pollutants in Neotropic Cormorants (Phalacrocorax brasilianus) Nesting along the Trinity River, Texas. Master's Thesis. Thesis uri icon


  • The Trinity River is a historically polluted river with records of various contaminants including organochlorine pesticides and their metabolites (OCPs), polychlorinated biphenyls (PCBs), and Mercury (Hg) detected in contaminant studies of the Trinity River and its watershed. Polybrominated Diphenyl Ethers (PBDEs) are a persistent contaminant group that has been shown to cause endocrinological changes, and some of its congeners have been banned in the US and in the whole EU. Fish eating birds are good indicators of contaminant accumulation in aquatic environments, as they accumulate lipophilic contaminants from eating fish and are typically top predators of their food web. Neotropic cormorants (Phalacrocorax brasilianus) are good indicators for local contamination and accumulate OCPs, PCBs, Hg, and PBDEs efficiently as the base levels of their food webs include aquatic invertebrates which regularly uptake lipophilic compounds from ambient water and sediment. The objectives of this research are to measure the persistent contaminant burden in Neotropic cormorants, a top piscivore, and to determine contaminant accumulation and potential impacts to the species, as well as if there is any correlation between sex, location of colony, or mass of Neotropic cormorant and contaminant burden. Cormorants were sampled in 2014 and 2015 from two sites on the Trinity River Watershed: Richland Creek Wildlife Management Area, and Lake Livingston. A liver section, spleen, kidneys, and gonads were sampled for histopathology, and a liver section was sampled for GC-MS analysis of OCPs, PCBs, and PBDEs, and breast feathers were sampled for Hg analysis by CVAAS. Results show total PCBs in liver sections of cormorants average 338+-12 ng/g ww, total OCPs detected in liver sections average 235+-9.5 ng/g ww with 4, 4' DDE as the most commonly detected at 184+-4.2 ng/g ww, the average total PBDE content per liver is 10+-0.8 ng/g ww and the average Hg detected in central breast feathers was 3+-0.2 ug/g dw. None of the contaminants measured were present in concentrations indicative of adverse effects; however, altered structure, composition and function, or histopathology were detected in the livers and kidneys of most samples. A novel coccidian Eimeria sp. was also detected in the kidneys of several cormorants. There was no significant difference in contaminants between sexes or location. Neotropic cormorants along the Trinity River do not display contaminant levels indicative of hazardous conditions for PCBs, PBDEs, DDE, and Hg; however, liver and kidney lesions are present in more than half of the individuals. Lesions along the glomeruli, tubules, and interstitial tissues of the kidney were the main findings observed in kidneys, while in the liver, chronic granulomatous cholangiohepatitis with intralesional trematodes were the main histopathologic finding. Our results indicate that Neotropic cormorants roosting in two colonies along the Trinity River are not at risk for adverse effects due to OCPs, PCBs, PBDEs, and Hg.

publication date

  • August 2017