Ocean's 'Potato Chips' Threatened

As oceans warm and become more acidic, ocean creatures such as Limacina helicina are undergoing severe stress and entire food webs are at risk. Limacina helicina is a pteropod — tiny marine molluscs the size of a lentil — referred to as the "potato chip" of the oceans because they are eaten widely by so many species, including salmon, mackerel, herring and cod. Pteropod translates as "winged-foot," which refers to the modification of the mollusc's foot into 2 wings or paddles used to row it through the water. After pteropods are eaten by fish, they are in turn consumed by other animals, such as penguins. They make their calcium carbonate shells from the seawater in which they live. As the water becomes more acidic to due climate change, their shells degrade, making them less able to tolerate the warmer water.

"These animals are not charismatic but they are talking to us just as much as penguins or polar bears," said NSF-funded researcher Gretchen Hofmann. "They are harbingers of change.” Hofmann, an associate professor of biology at the University of California, Santa Barbara, studies how genes go off and on in Limacina helicina and other marine invertebrates as they work to make their calcium carbonate shells. She reports that as marine invertebrates deal with increasing acidity, the larvae have to "re-tune" their metabolism in order to still make a shell; but this is done at a cost. The physiological changes that are a response to the acidity make the animals less able to withstand warmer waters, and they are smaller. These observations suggest that the "double jeopardy" situation — warming and acidifying seas — will be a complex environment for future marine organisms.

"It's possible by 2050 they may not be able to make a shell anymore" Hoffman says. "If we lose these organisms, the impact on the food chain will be catastrophic."

—Credit: Russ Hopocroft, University of Alaska Fairbanks