Large changes ahead for Antarctic marine ecosystems

A colony of emperor penguins.
Different penguin populations may respond differently to climate change due to regional differences in changes to their environments. (Photo: Frederique Olivier)

An international group of Southern Ocean experts has found that current and expected changes in Antarctic and Southern Ocean habitats will have consequences that change the structure and function of marine food webs.

The international study, published in Global Change Biology, synthesized current knowledge on the role of changing habitats in driving changes in groups of marine organisms, including microbes, krill, fish, marine mammals and seabirds.

Australian Antarctic Division program leader Dr Andrew Constable said that while the ultimate consequences of climate-related changes on Antarctic marine ecosystems are not well understood, they are expected to cause shifts in species’ ranges and may result in reduced biodiversity and novel changes in the structure and function of marine food webs.

“Microbes and zooplankton, for example, will generally move south as the ocean conditions in which they normally live move south,” he said.

“For Antarctic krill and finfish, which can move large distances, the breadth of their range will depend on how well they tolerate warming oceans and changes to productivity.”

The study also found that ocean acidification will affect krill reproduction and the ability of some marine organisms to produce shells and other hard, protective structures. While marine mammals and birds may need to find alternative locations for food, resulting in longer or more complex foraging trips for those bound to breeding colonies.

The study is an important step in addressing gaps in scientific knowledge identified by the International Panel on Climate Change and provides a model for future work.

 “A great challenge for Antarctic and Southern Ocean science is to develop methods for assessing current and future impacts of climate change on ecosystem structure and function,” Dr Constable said.

“These methods are needed to evaluate regional differences in the rate and direction of responses, and to integrate knowledge on the species-level responses and indirect effects that may be propagated through the food web.

“This review is a first step towards addressing these challenges, by synthesising current knowledge and identifying key uncertainties and vulnerabilities for Antarctic marine species and groups.”

The study involved 50 co-authors from seven countries and was a product of the international Southern Ocean Sentinel program, which aims to assess climate change impacts on marine ecosystems.