How is sea ice loss affecting biodiversity in the Weddell Sea?

The Weddell Sea, the largest marginal sea in the Southern Ocean, is a rich ecosystem teeming with life. Emperor penguins and seals raise their young here, while krill attract fish, whales, and seabirds. 

The seafloor hosts millions of icefish and gardens of sponges, anemones, and sea squirts, showcasing biodiversity comparable to tropical reefs.

Baseline for monitoring long-term changes 

Eleven institutes from eight countries have joined forces in the Weddell Sea Observatory of Biodiversity and Ecosystem Change (WOBEC). Over the next three years, these researchers will assess the current state of the biotic community in the Weddell Sea to establish a baseline for long-term monitoring of the transforming Southern Ocean ecosystem. 

WOBEC is part of the European Union’s BiodivMon flagship program, under the European Biodiversity Partnership, Biodiversa+. The program will commence in April with a Kick-off Meeting in Tallinn, Estonia. National partners have allocated 1.9 million euros for WOBEC, with significant contributions from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).

Unique biodiversity of the Weddell Sea 

“The Weddell Sea constitutes a largely untouched, and therefore extremely valuable, habitat. Not only does it have a high aesthetic value; it is also characterized by unique biodiversity. This biological diversity is also the source of important ecosystem services, like the storage of carbon in the deep sea through ice algae and the remains of plankton sinking to the bottom,” explained Hauke Flores, a marine biologist at AWI and coordinator of the EU project. 

“However, climate change has long-since spread to the southern polar region: In the past few years, we’ve witnessed an unexpectedly rapid decline in sea ice. We don’t know how, or if, the region’s organisms can adapt to the changed environmental conditions. In order to assess this aspect, we need to first gain a better grasp of the ecosystem’s status quo and urgently need to begin systematic data collection.”

Observations of marine biodiversity are lacking

The focus of the project is on observing potential long-term changes in biodiversity in the eastern Weddell Sea. Although countries like Germany, Norway, and South Africa have been conducting research in the region for decades, systematic studies on its massive ecosystem are lacking. 

According to Flores, there is a significant gap: for thousands of kilometers to the east and west of WOBEC’s target area, there have been no long-term observations of marine biodiversity.

Upcoming expedition in the Weddell Sea 

An expedition with the icebreaker Polarstern along the Prime Meridian and into the southern Weddell Sea, coordinated by the University of Rostock, is planned for 2026. During this journey, researchers aim to explore the Maud Rise seamount and build on previous investigations of the benthic biotic communities at Cape Norvegia, to the west of Germany’s Neumayer Station III.

In addition to collecting new data, the experts will delve into archives and make previously unreleased and hard-to-find results publicly accessible. 

“On the basis of historical and current data alike, our goal is to create a strategy for long-term environmental monitoring in the Weddell Sea with the aid of autonomous observatories, satellite-based remote sensing, and ship-based sampling,” Flores said. 

The process will involve stakeholders from political, business, and nature conservation communities, in close collaboration with the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR).

Proposal for a marine protected area

For years, the EU and other CCAMLR members have advocated for the protection of large areas of the Weddell Sea. With contributions from AWI, a protection concept was developed and initially submitted to CCAMLR in 2016. 

“The proposed Marine Protected Area currently consists of two regions in the western and eastern Weddell Sea, parts of which are within WOBEC’s target area,” explained Katharina Teschke, a marine ecologist and head of the MPA project at AWI. The planned MPA aims to preserve an untouched marine region as a refuge for cold-adapted species, allowing them to adapt to changing conditions as Earth warms.

“So far, the proposal for a new Marine Protected Area has failed to pass because the vote has to be unanimous, and the current geopolitical situation makes CCAMLR negotiations even tougher. However, the ratification of the Agreement under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biological Diversity of Areas beyond National Jurisdiction (BBNJ Treaty) last year is a promising development,” Teschke said.

“It’s a positive signal that could help stimulate the process of declaring a Marine Protected Area in the Weddell Sea under CCAMLR. WOBEC will give us the opportunity to create a science-based strategy for assessing biodiversity within the Marine Protected Area and its future changes,” she concluded.

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