HCNSO Student Theses and Dissertations

Defense Date


Document Type


Degree Name

M.S. Marine Biology


Oceanographic Center

First Advisor

Keith Ronald

Second Advisor

Richard E. Dodge

Third Advisor

Curtis Burney

Fourth Advisor

Richard H. Pierce


Tissue samples from twenty bottlenose dolphins from a stable, residential community of coastal dolphins in the western Gulf of Mexico were analyzed for toxic PCB congeners and chlorinated pesticides. The tissues analyzed (blubber and melon) were from known individuals in a long-term (27+ y) study that stranded and were recovered for necropsy. Substantial demographic data were available on these individuals and utilized in the analysis of maternal transfer of organochlorines to young.

The male dolphins in this study were shown to accumulate organochlorine contaminants with age. In female dolphins the organochlorine levels were found to decline with age. These results are in agreement with previous studies, with gestational and lactational transfer accounting for the decline seen in the females. A lengthening in interreproductive interval by increasing organochlorine levels after approximately age 30 y is noted in the females.

For the first time, this study quantified the organochlorine levels of the first calf of a female, testing the hypothesis that the first-born of a female receives a substantially greater organochlorine load than subsequent calves. The first-born calf (age 5.3 mo) had the highest blubber ΣPCB, total DDT, HCB, and total pesticide levels of all animals in this study. The organochlorine levels in this calf were 2-5 fold higher than in a similarly aged, fourth-born calf.

All animals in this study had appreciable EPCBlevels (range 0.07 - 26.9 ug/g wet weight; 2.6 - 203.2 ug/g lipid weight), and EDDT (range 0.06 - 10.3 wet weight; 0.9 - 88.1 ug/g lipid weight). These values are in a moderate range compared to other studies, but not far below levels at which western Gulf of Mexico bottlenose dolphins evidenced mortality events in 1990 and 1992. Further monitoring of this population is warranted.

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