Climate change could turn oxygen-free seas from blessing to curse for zooplankton

Tiny marine organisms called zooplankton can use specialized adaptations that allow them to hide from predators in areas of the ocean where oxygen levels are so low that almost nothing can survive, but they may run into trouble as these areas expand due to climate change. "Oxygen minimum zones are very difficult places to survive," said University of Rhode Island doctoral student Leanne Elder. "But we have discovered that these tiny animals have adapted in two specialized ways. First, they suppress their metabolism, which is very much like hibernation in other animals. Second, while converting food into energy normally requires large amounts of oxygen, these zooplankton use a different process - anaerobic glycolysis - which allows them to use only small amounts."

The tiny animals use the oxygen minimum zones as refuges from predators, migrating vertically down into the zone during the day and returning at night to feed in the oxygen- and food-rich areas closer to the surface.

However, oxygen minimum zones are predicted to expand into shallower waters as global warming continues, which will force the zooplankton into a narrow band of water during the night and making them susceptible to their main predators -- fish. If this causes a population crash in these animals, it will have impacts all the way up the food chain.

A resident of Cranston, R.I., Elder will present the results of her research today at the annual conference of the Society for Experimental Biology in Glasgow, Scotland.

Although the oxygen minimum zone provides a refuge for zooplankton, spending time there does have a cost to the animals: anaerobic glycolysis results in a build up of acid that they can only dispose of when they return to surface waters. Elder said that future research needs to be done on how the reduction in oxygen- rich habitat will affect these animals and hence the whole ocean ecosystem.

Source: University of Rhode Island