Warmer Waters Lead to Spike in Baby Fur Seal Deaths

From coral bleaching to ocean acidification, the pumping of carbon dioxide into the atmosphere and the resulting climate change is a major problem for the world’s marine life. And just last week, a study revealed that the world’s oceans have absorbed 60 percent more heat than previously thought.

Now, a new study has zeroed in on one particular victim of higher ocean temperatures: baby fur seals.

Fur seal babies, Falklands and S. Georgia

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Research published in eLife Tuesday found that warmer oceans put fur seal pups at greater risk of dying from hookworm infections. That’s because of a complex chain of events that starts with the fact that, in warmer waters, fish are harder for adult fur seals to find.

“Increasing ocean temperatures are associated with changes in the patterns of wind and ocean currents, which cause a decrease in the cycling of nutrients and, by extension, the abundance of life including fishes,” first author and postdoctoral associate in the Odum School of Ecology at the University of Georgia Mauricio Seguel said in an eLife press release.

The chain of cause-and-effect goes something like this:

1. Warmer temperatures decrease the presence of fish.

2. Mother fur seals spend more time fishing and less time with their pups.

3. The pups get less care and have weaker immune systems as a result.

4. More pups die from infections like hookworm.

Video of South American Fur Seal mother and infant relaxing and then feeding @LivingCoasts #FurSeal pic.twitter.com/CytiinHIS0

— Brian Lilly (@brglilly) May 17, 2018

Specifically, the researchers studied a fur seal colony in South America between 2004–2008 and 2012–2017. They found that, in colder years, only 30 percent of the young fur seals died from the hookworm infection. In warmer years, around 50 percent of them died, a 66.67 percent increase in mortality. Seguel said he hoped his research could help reverse this trend.

“Our work reveals how changing ocean conditions are having an indirect effect on fur seal pups’ mortality rates as a result of infection,” Seguel said. “We hope these findings help lay the groundwork for investigating ways to limit the effect of parasitic diseases among fur seals and other marine mammals in the context of a changing climate.”

Fur seals aren’t the only marine mammals at risk because of warming waters. In the Arctic, melting sea ice has allowed more parasites to spread. As early as 2014, the parasite Toxoplasma gondii was found in Western Arctic Beluga whales for the first time. The parasite Sarcocystis pinnipedi killed 406 gray seals in the North Atlantic in 2012.

“Ice is a major barrier for pathogens,” Michael Grigg of the U.S. National Institutes of Health told the American Association for the Advancement of Science at the time. “What we are seeing with the big thaw is the liberation of pathogens gaining access to vulnerable new hosts and wreaking havoc.”