That the terrestrial and especially marine ecosystems suffer from heavy pollution through humanities choices has long been declared as one of the main threats for biological diversity. Therefore, researchers are constantly scrambling to determine how the contaminants affect environment and wildlife while new types of plastics and chemicals are already developed at the same time.
One such research approach leads through assessing marine mammals as they are “ecosystem sentinels that reflect anthropogenic threats through their health — which has implications for human health as well”. Since they also largely prey on the same fish humans consume, their place at the top of the marine food chain also provides a relatively low-cost snapshot of the potential exposure risk in humans, as well as other marine animals.”
In a study published this week in Frontiers in Marine Science, researchers measured the presence of such chemicals in whales and dolphins that washed ashore in Florida and North Carolina between 2012 and 2018. The levels of the chemicals were assessed in blubber and liver samples of 83 stranded animals of 11 different species, spanning all age and both sex groups. By providing baseline information on the current contamination level as well as possible correlations to stranding causes, the researchers hope to find out more about the poorly understood impact of the contamination on the marine ecosystem.
The study reported some of the highest mercury and arsenic levels recorded to date in stranded dolphins and whales. Generally, bottlenose dolphins showed higher amounts of lead and mercury than pygmy sperm whales did. A direct correlation to stranding causes (i.e. illnesses through an impacted immune system) could not be found.
The authors deduce that “while exposure to contaminants and toxic elements may not lead directly to stranding, such exposure is thought to impact animal survival through indirect effects on behavior, reproduction, and immunity.” Additionally, the current study was limited to blubber and liver samples, and future work is needed to fully understand potential effects on other organs.
Still, these results help establish a baseline for future work by measuring levels and contaminants that have never been officially analyzed on such a scale before, thereby contributing to the search of understanding the impacts of chemicals and plastics on the ecosystem. It also highlights the importance of marine mammal stranding response efforts and exemplifies why it is necessary to conduct necropsies of these animals and collect and archive tissue samples for future research.
The study can be found here: https://www.frontiersin.org/articles/10.3389/fmars.2020.00630/full
“Anthropogenic Contaminants and Histopathological Findings in Stranded Cetaceans in the Southeastern United States, 2012–2018” by Annie Page-Karjian, Catherine F. Lo, Branson Ritchie, Craig A. Harms, David S. Rotstein, Sushan Han, Sayed M. Hassan, Andreas F. Lehner, John P. Buchweitz, Victoria G. Thayer, Jill M. Sullivan, Emily F. Christiansen and Justin R. Perrault, 5 August 2020, Frontiers in Marine Science.
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