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Examining the Relationships Between Blubber Steroid Hormone and Persistent Organic Pollutant Measurements in Common Bottlenose Dolphins



Thomas M. Galligan, Brian C. Balmer, Lori Schwacke, Jennie L. Bolton, Brian M. Quigley, Patricia Rosel, Gina M. Ylitalo, Ashley S. Boggs-Russell


In this study, we use remotely collected blubber samples from common bottlenose dolphins (Tursiops truncatus) inhabiting the waters near a U.S. Environmental Protection Agency Superfund site with high local DDx concentrations, to study the impacts of DDx exposure on steroid hormone homeostasis in cetaceans. Sampled dolphins exhibited exposure to all six DDTs that were measured (p,p’- and o,p- isomers of DDT, DDE, and DDD), additional pesticides [chlordanes (CHLDs), mirex, dieldrin, and hexachlorobenzene], polychlorinated biphenyls (PCBs), and brominated diphenyl ethers (BDEs). Using principal components analysis (PCA), we determined that blubber DDTs were positively associated with one another, as exhibited by their loading together to the first principal component (PC1). The remaining POPs loaded positively to PC2. Blubber testosterone (T) was negatively correlated with PC1 scores in males, suggesting that DDx exposure had a negative impact on androgen homeostasis. Cortisol (F) was negatively correlated with PC2 scores in females. We further determined that T was negatively correlated with o,p-DDE, o,p-DDD, and p,p’-DDD in males sampled the fall but not in the summer, when T values are elevated presumably due to a spring/summer breeding season. F was negatively correlated with all six DDTs and ∑DDTs, as well as ∑CHLDs, ∑PCBs, and ∑BDEs in females. This study relied on incidental, uncontrolled, complex exposures, and, due to use of remote biopsies, involved minimal collection of demographic data, so it is difficult to assign causality to the relationship between hormones and POP concentrations. However, these results suggest that POP-mediated endocrine disruption may have occurred in this stock of dolphins, warranting further investigation. Importantly, this study demonstrates that remotely collected blubber biopsies are a useful tool for initially screening cetacean populations for contaminant-mediated disruption of steroid hormone axes.
Environmental Pollution


bottlenose dolphin, endocrine disruption, steroid hormone, blubber, DDT, marine mammal
Created March 24, 2019, Updated February 4, 2020