Spatial distribution of bottlenose dolphins (Tursiops truncatus) inferred from stable isotopes and priority organic pollutants

Abstract

Differences in priority organic pollutants (POPs), analyzed by gas chromatography-mass spectrometry, and stable isotope ratios (δ(13)C, δ(34)S, and δ(15)N; analyzed by isotope ratio-mass spectrometry), divide 77 bottlenose dolphins (Tursiops truncatus) from the Florida Gulf Coast into three distinct groups. POP levels reflect human population and historical contamination along the coast. In the least disturbed site, concentrations of ΣPOP in male dolphins were 18,000 ng g(-1)±6000 (95% confidence interval here and throughout); in the intermediate bay, males had ΣPOP concentrations of 19,000 ng g(-1)±10,000. St Andrews Bay was home to dolphins with the highest ΣPOP concentrations: 44,000 ng g(-1)±10,300. δ(34)S and δ(15)N, differed significantly between St. George Sound dolphins and those frequenting each of the other two bays, but not between St. Andrews and St. Joseph Bays. ΣPOP concentrations were statistically higher in dolphins frequenting St. Andrews Bay, but were not significantly different between dolphins occupying St. Joseph Bay and St. George Sound. Thus, using either POP or isotope values alone, we would only be able to identify two dolphin groups, but when POP and isotope data are viewed cumulatively, the results clearly define three distinct communities occupying this region.