Australasian Science: Australia's authority on science since 1938

Plankton Not Adapting

By Stephen Luntz

Cold water plankton are failing to adapt to global warming, and the results will be felt at the fish-and-chip shop counter.

Calanus finmarchicus is a North Atlantic species of plankton that is common in colder waters. Over the past 50 years, temperature patterns in the region it inhabits have moved 500 km north. This fact provides an opportunity to study how species respond to the changed conditions.

“We know that warm water species are expanding their ranges as warming occurs, and vice versa. What is not known is whether species are able to adapt to new temperatures. Will, for example, cold water species gradually adapt so they can withstand warming seas and not continually contract their ranges,” says Prof Graeme Hays of Deakin University.

C. finmarchicus should be more suited to adaptation than many species. It has a lifespan of a year or less, giving plenty of opportunity for rare warm-adapted genes to spread through the population. Unfortunately this has not occurred, Hays reports in Global Change Biology. Instead, its southern boundary has moved north at the same rate as the isotherms. Meanwhile its relative, C. helgolandicus, has moved in to colonise the same space.

Few non-biologists may care about one obscure plankton species replacing another, but the implications are substantial. Cod and hake rely on C. finmarchicus for their food supply in the northern spring, while C. helgolandicus is most abundant in summer and autumn. “By the time it blooms the fish larvae have starved,” Hays says.

Mackerel and black bream may take the cold water species’ place, as they are adapted to feed on C. helgolandicus, but Hays says: “People will have to change their preferences for what they like. Cod and chips is popular; bream and chips is not currently saleable.”