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Marine Ecosystems

Changes in climate threaten Antarctic and Southern Ocean marine ecosystems.

Southern Ocean ecosystems are an integral part of the Earth system. They perform a range of globally important ecosystem services, such as contributing to biodiversity, nutrient and biogeochemical cycling, climate regulation, fisheries, and wildlife tourism, that support human communities and economies across the globe. Together with direct human impacts (such as fishing, pollution, tourism, and shipping), climate change is already causing changes in Southern Ocean environments (e.g. changes in the wind patterns, the cryosphere, ocean acidification, ocean circulation, air and sea temperatures). Continued changes threaten the habitats of key species, which will result in shifts in species distribution and abundance, and community composition. These, in turn, will affect the structure and functioning of Southern Ocean ecosystems, including for example the survival of iconic and key-stone species (such as Antarctic krill, penguins, and whales), the future availability of living resources to international fisheries, and the ability of these ecosystems to regulate climate.

Ultimately, these threats will affect the complex life-histories and distributions of air-breathing predators (including seabirds, seals, whales), pelagic (e.g. phytoplankton, zooplankton, fish, squid) and benthic communities (e.g. crustaceans, worms, molluscs, starfish, sea urchins, corals, sponges, bryozoans) across a range of spatial and temporal scales. Antarctic and Southern Ocean ecosystem change may affect variables such as carbon and nutrient cycling, biodiversity, and availability of marine living resources to current international fisheries.

The magnitude and direction of these physical changes are likely to differ between regions across the Antarctic, and hence the responses of species, populations, and food webs may also be regionally variable.

Storylines

Climate modellers, marine ecologists, and ecological modellers within PolarRES have been working together to choose an appropriate subset of the latest Earth System Models. The purpose of these subset is to develop highly spatially and temporally resolved climate models and coupled climate-ocean-ice-biogeochemistry models (both hindcast and forecast) for the Antarctic region, using the storylines approach.

These high-resolution climate models are nearly complete and will produce a range of plausible future scenarios of Antarctic climate change out to 2100, including;

Summer:

  • High sea ice loss and earlier polar vortex breakdown delay
  • Low sea ice loss and later polar vortex breakdown delay

Winter:

  • High sea ice loss and weak polar vortex strengthening
  • Low sea ice loss and strong polar vortex strengthening

When the forecast models are ready, ecologists will couple these climate models to ecological models to generate projections of future changes in the distribution and abundance of key zooplankton species – Antarctic krill and copepods – across the Southern Ocean.

The hindcast climate models have now been completed and  marine ecologists have been using these to develop relationships between historical distributions of Antarctic krill and copepods in association with the marine environment.  Once the forecast models are ready, they will be used to generate (Ecological Niche) models to examine the future changes in Antarctic krill and copepods.

Antarctic krill and copepods are an important component of Southern Ocean food webs (Antarctic krill are a keystone species), transferring energy from the phytoplankton they consume to a range of their predators,  including other zooplankton, squid, fish, seals, penguins, and whales. They also play a vital role in transferring carbon to the deep ocean, thereby helping to regulate our climate. 

Being able to predict the future dynamics of these tiny creatures, upon which our societies and Earth System depend, can help refine the global carbon cycle, and policy makers and communities can develop sound decisions to adapt and respond to the impacts of climate change in the region.