Through a chain of events, more and more fur seal pups risk dying from hookworm infections as a result of rising ocean temperatures.

This is the conclusion in a study recently published in the eLife journal.

According to first author Mauricio Seguel, Postdoctoral Associate in the Odum School of Ecology at the University of Georgia, Athens, US, "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.

Subsequently, this can affect the fur seal pups, even though they still sustain on their mother’s milk.

"Reductions in marine life have also been linked with the decline of marine mammal populations, as they rely on fish as their main food supply. Fur seals and sea lions may be included here, because although their pups live on land, they depend on their mother's' milk for survival, which can only be produced if the mothers eat enough fish."

To investigate how marine mammals may be affected by changes in ocean conditions, the researchers studied a fur seal colony in South America, focusing on the years 2004 to 2008 and 2012 to 2017.

They discovered that during years with colder ocean temperatures (like in 2007), the pups received more maternal care and so had better immunity. About 70 percent of them were able to eliminate the parasite from the intestine via a specific immune response that includes producing antibodies that kill it.

Consequently, when the ocean temperatures rose, as in 2017, the mothers spent less time with their pups as they spent more time hunting for fish in the ocean. As a result, the pups grew slower, had lower blood glucose levels and could not fight off hookworm infections. Approximately half of them died from the infection.

"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," said Seguel.