Abstract
Marine mammals, such as cetaceans, are exposed to a wide range of environmental pollutants, including metals, polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons (PAHs) as a result of direct or indirect anthropogenic disturbances within their environment.1 Since the 1960s, accumulation of chemicals like PCBs has been detected in the tissues of marine mammal species, and this has persisted throughout the decades.2 Cetaceans are regarded as a sentinel species, as changes in their health and population can serve as indicators of current or potential negative effects on the marine ecosystem.3
Our research primarily focused on detection of PAHs, PCBs, and metals in tissues of 146 bottlenose dolphins (Tursiops truncatus) that stranded in the Mississippi Sound between 2010 and 2021. Each individual bottlenose dolphin that stranded had four tissue types (i.e., blubber, kidney, liver, and muscle) collected either from frozen archival or fresh tissues from necropsies at the Institute for Marine Mammals Studies, MS. Analysis and quantification of 23 PAHs, 8 PCBs, and 22 metals was performed at the Mississippi State Chemical Laboratory in Starkville. The samples were divided into four time periods: 1) 2010–2018, 2) 2019, 3) 2020, and 4) 2021 and normalized to 1 g of tissue. This allowed for the possibility to observe any potential variations in environmental exposures brought on by the Bonnet Carré Spillway’s more frequent opening in 2019, which helped to avert flooding in New Orleans. It has been suggested that more frequent spillway openings could impact marine ecosystems by changing the pH or salinity of the water. Only 8/23 PAHs were detected, with naphthalene being detected most often with highest levels in blubber and liver. Most of the 8 PCBs were detected regardless of the time period and the trend of PCB-positive dolphins decreased in 2020 before increasing again in 2021. Three metals were detected in all four tissues in each individual: potassium, sodium, and zinc. In contrast, beryllium was not detected in all four tissues in each individual.
Our results show that bottlenose dolphins are susceptible to the accumulation of PAHs, PCBs, and heavy metals. Despite mitigation and regulation measures to reduce pollution, the majority of these animals still exhibit detectable levels of environmental contaminants. Understanding the impact of environmental pollution on cetaceans is important because a decline in their health and population may disrupt critical marine ecosystem functions. Long-term surveillance of bottlenose dolphins is of importance and reaffirms their role as sentinels for marine ecosystems and public health.
Acknowledgments
The authors would like to thank the Institute for Marine Mammal Studies personnel for sample collation and management. Funding for this project was generously provided by the Mississippi Marine Mammal and Turtle Conservation, Recovery, and Monitoring Program, which is funded by the National Fish and Wildlife Foundation under the Mississippi Department of Environmental Quality Agreement No. 18-00081 and the Mississippi Department of Marine Resources (Gulf of Mexico Energy Security Act project number 3000027046).
*Presenting author
+Student presenter
Literature Cited
1. Reijnders PJH, Aguilar A, Borrell A. Pollution and marine mammals. In: Encyclopedia of Marine Mammals. 2009:890–898.
2. Tanabe S. Contamination and toxic effects of persistent endocrine disrupters in marine mammals and birds. Mar Pollut Bull. 2002;45:69–77.
3. Bossard G. Marine mammals as sentinel species for oceans and human health. Oceanography. 2006;19:134–137.