From little things, bigger things grow

Stacy DeppelerAntarctic marine life from krill to whales, seals, penguins and seabirds all ultimately depend on phytoplankton for their food, but a study published recently in the journal Frontiers has revealed these single-cell plants at the base of the food chain are being affected by a range of climate-induced stressors. Warming seas, increased ocean acidification, and reductions in salinity and sea ice are all posing a threat to the health of marine ecosystems.

The study was a collaborative project between PhD student Stacy Deppeler from Tasmania’s Institute for Marine and Antarctic Studies, and researchers from the Australian Antarctic Division, and the Antarctic Climate and Ecosystems Cooperative Research Centre, to better understand how ecosystems are adapting in response to changes in phytoplankton communities in the Southern Ocean.        

Deppeler said a fundamental part of the ecosystem is changing in ways that could have global implications although it remained uncertain exactly what the changes and impacts would be. It was also unlikely clear trends could be identified until around 2050, when big changes in phytoplankton communities could have already occurred, and the time for implementing mitigation measures may have passed.

“Phytoplankton also draw down carbon as they photosynthesise, and capture it in deep ocean when they sink to the seafloor. The level of atmospheric carbon would be around 50 per cent higher without the uptake provided by Southern Ocean phytoplankton, so changes to their communities could have significant implications for our environment and climate,” she said.

The research also found there was a trend towards smaller-celled phytoplankton, with implications for a possible reduction in their nutritional value for predators.

“Although it’s currently unknown whether the rate of environmental change will outpace the ability of Southern Ocean phytoplankton to adapt, it’s inevitable that changes in the Southern Ocean will influence the food chain there, the ocean biogeochemistry, and feedback on climate,” Deppeler said.

The full text of ‘Southern Ocean Phytoplankton in a changing climate’ is available at journal.frontiersin.org/article/10.3389/fmars.2017.00040/full

Anne Layton-Bennett