Sea ice effects on Ross Sea food webs

Benthic community at Terra Nova Bay, Ross Sea, including: encrusting coralline algae, seastars, and sea urchins camouflaged with pieces of drift red algae. (Photo: Rodd Budd, NIWA)

Scientists from NIWA and the Finnish Institute of Marine Research are using novel ways to explore the effects of sea ice on coastal food webs in Antarctica.

Sea ice is a major driver of polar marine ecosystems, partly through its effect on light levels and, hence, productivity. Understanding its influence on polar food webs will help to predict effects of climate change.

The team investigated the influence of sea ice on benthic (bottom-dwelling) organisms at depths of up to 25 m from five areas along the western Ross Sea coast. By comparing their isotope signatures, they were able to measure food web linkages. “That’s extremely time consuming via direct observation, and so difficult to do in the Antarctic,” says NIWA benthic ecologist Dr Vonda Cummings.

Nitrogen isotope signatures – used to determine level in the food chain and identify dietary shifts – showed that some bivalve shellfish and echinoderms (including sea urchins) consumed more freshly produced algae in ice-free areas of the north and east. They ate more detritus in southern areas affected by more permanent sea ice. Some species switched their level in the food chain in different areas – for instance, switching between grazers and predators.

“These results will help us predict how benthic ecosystems may respond to changes in the extent and persistence of sea ice in the Antarctic,” says Vonda.

This research was funded by the Ministry of Fisheries, NIWA, the Academy of Finland and the European Commission.

Research subject: AntarcticaBiodiversity