The Incredible, Recent, Global Rise in the Stranding of Marine Mammals

By Dr Bill McGraw

During late September 2020, Australia experienced the largest mass stranding of whales in the history of that country. Two weeks later, during early October, the stranding of 7,000 cape fur seals on the coast of Namibia was identified as a major marine mammal stranding event. Disturbingly, this was followed one month later by 100 pilot whales beaching themselves on the coast of Sri Lanka. New Zealand then reported just a few weeks after that, the largest beach stranding event ever off the coast of the Chatham Islands, while during the same time, six baleen whales were found on the beach of Northern France, emaciated with lesions of the heart and lung. This prompted French marine researcher Willy Dabin to make the comment that whales are currently beaching themselves in near epidemic proportions. 

Having examined these recent marine mammal stranding events which mostly resulted in death, I was eager to have a look at trends over a longer period of time. Regrettably, my search resulted in more information that shocked and worried me. Data from two peer reviewed scientific journals, a website and one marine research meeting report, from three separate areas of the Pacific and Atlantic Oceans and the Baltic Sea, all display the same trend, sharp increases in marine mammal stranding during the past two decades. How can that be? I have at least, part of the answer, but first a closer look at these reports.

A review of 50 years of stranding of toothed whales off the coast of Chile (Figure 1), showed low to moderate stranding events up until the year 2010, then there was a sharp rise over the next decade. Approximately, 40% of all toothed whales call the 8,000 km coastline of Chile home. Although the authors of this study mention “coastal contaminants” as potentially being important, they plainly state that the phenomenon of stranding is the result of a variety of inputs. They naturally include global climatic change as one of the potentials.

Meanwhile, on the other side of South America, on the coast of the Atlantic Ocean, 32 species of toothed whales and dolphins can be found on the coast of Brazil, with 17 of them found stranded during the 32 year period of another published study. The top three species registering most frequently were dolphins. Although fishery incidents and boating accidents are suggested to be involved in up to 1/3 of the beaching of these large mammals, it is unclear why during the period of 2001 to 2014 there was a dramatic rise in standing events.

A third report from the Netherlands on the stranding of harbour porpoises reveals the most dramatic increase of stranding events by far. A graph found on the website Ecomare shows data from 1970 to 2015 which demonstrates a 10 fold increase in the stranding of harbour porpoises, comparing the period of 1970 to 2000 with the period of 2000 to 2015. Here in this report, it is stated that many of the deaths of these marine mammals resulted from drowning, being caught in nets used by fishing vessels. Yet once again, it was not stated why there is a steep linear increase during the later periods.

A fourth example comes from porpoise stranding events in the Baltic Sea (Figure 4). Here we see a similar trend from 2002 to 2017, with a dramatic increase in the stranding of porpoises compared to the previous 12 years, and so this trend is not limited to the larger oceans. This time the report relates a decrease in prey items as to the possible cause of marine mammal stranding and there is no mention of why the dramatic increase occurs during the second half of this study.

Conspicuously missing from the reports of these research studies, as well as Youtube and internet sites detailing major marine mammal stranding events is a toxicology report including mercury concentrations. Other peer-reviewed journals have included research findings (2012, 2018) that show mercury levels from 80 to 230 times higher in stranded marine mammals compared to healthy animals that had not beached themselves. So it is unclear why these other reports had not engaged in the analysis of mercury levels in liver, kidney and muscle tissue. Mercury levels have increased in the environment dramatically during the last two decades due to artisanal mining, the increase in coal combustion and the insane rapid rise of forests burning around the San Francisco Bay area.

These three factors alone have resulted in a tremendous rise in mercury into the atmosphere which settles in the ocean and gets transformed into the toxic form of methyl mercury in areas of low oxygen, both in the sediments of estuaries and deep water. A more detailed look at these sources of mercury pollution is definitely warranted. An examination of the biggest input of mercury into the atmosphere during a 600-year analysis from mercury deposition in an ice core, from a glacier in Wyoming of the United States, would reveal that the gold rush of California during the period of 1849 to 1884 would be the second biggest input of atmospheric mercury during that lengthy period (Figure 5).

Moreover, widely unknown is the mercury vapour released from the recent burning of 4 million acres of forests in northern California which is the most mercury toxic area in the world due to the gold rush of long ago, as mercury stays in the environment almost forever. Forests readily absorb atmospheric mercury and it can be a major sink for mercury in mercury toxic areas. Meanwhile more recently, there exists a gold rush on a global level due to the high price of gold.

Artisanal mining of gold contributes to the highest amount of mercury input into the atmosphere currently, according to reports from peer-reviewed scientific journals. The countries currently involved in mercury pollution from the use of elemental mercury in the amalgamation of gold for extraction are the Philippines, China, Indonesia, Columbia, Ecuador, Peru, Ghana and Sudan. In contrast, the second biggest input of mercury into the atmosphere is the burning of coal. Coal burning is at an all-time high in China due to the continual increase in the industry. China burns more coal then the rest of the world combined. 

So in conclusion we can see that, historically, mining for gold has been one of the biggest inputs of mercury into in the atmosphere and it is the biggest mercury input into the atmosphere currently, and, ironically is likely contributing to the death of marine mammals. Coal burning and industry have always been tragically the biggest inputs of mercury into the environment overall and this has likely caused increased mercury toxicity of marine mammals as well. Unfortunately, the majority of the mercury in mammals is stored in liver and kidney tissues and it is very difficult to remove from the body. This fact and the constant mercury input into the environment that will likely continue, will result in an increase in stranding events of marine mammals in the future. Those marine mammals that remain will likely be those that are genetically predisposed for mercury removal, or “fast detoxifiers”.

About the author:

Dr Bill McGraw owns and operates a biosecure, zero water exchange, aquaculture farm in Panama where he regularly produces mercury-free, organic shrimp and fish sold directly to local customers. He teaches a “Basics of Aquaculture” class on the internet as well which covers mercury toxicity in marine animals. The next course begins January 13, 2021. More info on mercury and aquaculture can be found on his website at www.newaquatechpanama.com or in the book he published on amazon: Amazon.com: Mercury: The Ultimate Truth and Chronic Disease (9781799136415): McGraw, Dr. Bill: Books

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This piece was prepared online by Panuruji Kenta, Publisher, SEVENSEAS Media