Anthropogenic Contaminants and Histopathological Findings in Stranded Cetaceans in the Southeastern United States, 2012–2018

Anthropogenic contaminants in the marine environment often biodegrade slowly,
bioaccumulate in organisms, and can have deleterious effects on wildlife immunity,
health, reproduction, and development. In this study, we evaluated tissue toxicant
concentrations and pathology data from 83 odontocetes that stranded in the
southeastern United States during 2012–2018. Mass spectrometry was used to
analyze blubber samples for five organic toxicants (atrazine, bisphenol-A, diethyl
phthalates, nonylphenol monoethoxylate [NPE], triclosan), and liver samples were
analyzed for five non-essential elements (arsenic, cadmium, lead, mercury, thallium),
six essential elements (cobalt, copper, manganese, iron, selenium, zinc) and one
toxicant mixture class (Aroclor1268). Resultant data considerably improve upon the
existing knowledge base regarding toxicant concentrations in stranded odontocetes.
Toxicant and element concentrations varied based on animal demographic factors
including species, sex, age, and location. Samples from bottlenose dolphins had
significantly higher average concentrations of lead, manganese, mercury, selenium,
thallium, and zinc, and lower average concentrations of NPE, arsenic, cadmium, cobalt,
and iron than samples from pygmy sperm whales. In adult female bottlenose dolphins,
average arsenic concentrations were significantly higher and iron concentrations were
significantly lower than in adult males. Adult bottlenose dolphins had significantly higher average concentrations of lead, mercury, and selenium, and significantly lower average
manganese concentrations compared to juveniles. Dolphins that stranded in Florida had
significantly higher average concentrations of lead, mercury, and selenium, and lower
concentrations of iron than dolphins that stranded in North Carolina. Histopathological
data are presented for 72 animals, including microscopic evidence of Campula spp.
and Sarcocystis spp. infections, and results of Morbillivirus and Brucella spp. molecular
diagnostic testing. Sublethal cellular changes related to toxicant exposure in free-ranging
odontocetes may lead to health declines and, in combination with other factors, may
contribute to stranding.