Weddell Sea Ecosystem

The proposal for a marine protected area in the Weddell Sea concerns a special region of the Southern Ocean around Antarctica. Unlike other areas in the Southern Ocean, the Weddell Sea is so far largely untouched by human influences. It therefore offers the unique chance to protect a pristine region from future impacts.

The region is also notable because its functions and ecosystems are unlike any other. For example, the Weddell Sea plays an important role in driving global thermohaline circulation, in other words all global ocean currents. This is because the area produces a lot of "Antarctic Bottom Water" – a particularly cold and oxygen-rich water mass. This bottom water then moves north towards the equator, driving a "conveyor belt" of ocean currents that not only circulate nutrients and oxygen across the globe, but also decisively influence global climate and regional weather patterns.

Sea ice cover of the Weddell Sea is extremely seasonal – it covers more than 75% of the area during austral winter, while in summer the sea ice shrinks to about one third of its maximum winter extent. This extreme habitat is home to many species that are linked through the Antarctic food web. Ice algae and bacteria grow on the underside of the ice, providing food for zooplankton such as Antarctic krill. The zooplankton is a food source for fish, which in turn, along with krill, are prey for penguins, seals, and whales. In addition, dead zooplankton sinks to the seafloor, providing food for an astonishingly rich fauna of benthic organisms. Particularly the continental shelf in the Weddell Sea is home to large and unique metre-high "under-water forests" of sponges and filter feeders. These seafloor ecosystems are comparable in species richness and function to tropical coral reefs. 

The Weddell Sea, due to its ice cover and favourable currents, is expected to be one of the last regions of the Southern Ocean where the consequences of climate change will manifest. The adjacent map, available at the Meereisportal, shows the sea ice extent on 21 February 2022, the lowest sea ice extent around Antarctica (2.27 million km²) recorded since the beginning of satellite observations in 1979. During this record low, sea ice concentration in the Weddell Sea remained comparatively high. This shows that the Weddell Sea can serve as a refuge for ice-dependent species (like Antarctic krill, Weddell seal) or species with low heat tolerance (like many Antarctic fish species). In the future, these uniquely cold-adapted species may use the Weddell Sea as a refuge. There is reason to hope that they will gradually adapt to rising water temperatures over generations under the protection of the Weddell Sea and thus survive.

Some facts about the Weddell Sea

  • Around 14,000 faunal taxa live on the seafloor of the Weddell Sea.

  • With more than 70,000 breeding pairs, about one third of all emperor penguin chicks hatch on the sea ice of the Weddell Sea.

  • About 300,000 breeding pairs of the Antarctic petrel use the Weddell Sea as hunting area.