Benthic Ecosystem Dynamics in the Southern Ocean

The benthic realm of the Southern Ocean, encompassing seafloor habitats from shallow rocky shores to deep continental slopes, underpins critical ecosystem functions and global biogeochemical cycles. Communities of macroalgae, sponges, bryozoans, echinoderms and myriad invertebrates process organic matter delivered from the pelagic zone, sequester carbon, and sustain higher trophic levels. Environmental drivers such as sea-ice cover, glacial retreat, iceberg scour and sediment input shape species distributions, community structure and bioturbation rates. Warming and acidification are altering primary production, ice-pack dynamics and meltwater inputs, with cascading effects on benthic biomass, diversity and trophic interactions. Research has revealed unexpected hotspots of benthic abundance beneath floating ice shelves and within glacial fjords, the deep penetration of macroalgal carbon into sediments, and shifts in competition and recruitment following regime changes. Understanding these dynamics is vital for predicting ecosystem resilience, guiding conservation measures, and quantifying the Southern Ocean’s role in carbon sequestration under rapid climate change.

Research from Nature Portfolio

New field surveys extending to depths of over 70 m have uncovered diverse and abundant macroalgal assemblages in coastal regions once deemed inhospitable, indicating that Antarctic macroalgae may contribute up to 2.8 % of global macroalgal carbon fixation. Light-modelling and in situ measurements demonstrate that deep-living seaweeds and crustose coralline algae represent a significant and previously overlooked carbon sink. Complementary experimental work has shown that pulses of lithogenic glacial meltwater, rich in suspended inorganic particles, can impair key benthic consumers such as krill by reducing feeding efficiency and absorption capacity within hours. These findings underscore the dual role of Antarctic benthos in blue-carbon processes and its vulnerability to changing glacial dynamics.

Benthic Ecosystem Dynamics in the Southern Ocean publication trend

The graph below shows the total number of articles in benthic ecosystem dynamics in the southern ocean across all publications each year (not limited to Nature Index journals).

Technical terms

Benthic: Pertaining to organisms and processes at the bottom of a marine environment.

Macroalgae: Large, photosynthetic algae (seaweeds) that form forests on hard substrates and contribute to primary production.

Bioturbation: The reworking of sediments by living organisms, influencing nutrient cycling and sediment structure.

Blue carbon sequestration: The capture and long-term storage of carbon in marine ecosystems such as seagrass meadows, mangroves and macroalgal assemblages.

Ice scour: Physical disturbance of the seafloor by drifting icebergs or sea ice, affecting benthic community structure.

References

1. Deep-living and diverse Antarctic seaweeds as potentially important contributors to global carbon fixation. Communications Earth & Environment (2024).
2. Spatial competition in a global disturbance minimum; the seabed under an Antarctic ice shelf. The Science of The Total Environment (2023).
3. Strong correlations of sea ice cover with macroalgal cover along the Antarctic Peninsula: Ramifications for present and future benthic communities. Elementa: Science of the Anthropocene (2023).
4. Megafaunal Communities in Rapidly Warming Fjords along the West Antarctic Peninsula: Hotspots of Abundance and Beta Diversity. PLOS ONE (2013).
5. Glacial melting: an overlooked threat to Antarctic krill. Scientific Reports (2016).