#muddy sediments

BOTTOM TRAWLING RELEASES HIDDEN CO₂ FROM THE SEAFLOOR

A new study reveals that bottom trawling, an industrial fishing practice that drags heavy nets across the seafloor, may significantly reduce the ocean's capacity to absorb carbon dioxide (CO₂). When sediment is resuspended by trawling, storms, or tides, it exposes previously buried compounds like pyrite (FeS₂) to oxygen. The oxidation of pyrite releases CO₂ into the water, contributing to the ocean’s carbon flux and potentially adding to atmospheric greenhouse gases.

Until now, most research had focused on how disturbing organic carbon in sediments accelerates its remineralization into CO₂. This new research, however, highlights that the oxidation of pyrite, a sulfur-based mineral, could be an even greater source of carbon dioxide from the seafloor. Since fine-grained sediments rich in pyrite are widespread on continental shelves, many of which overlap with commercial fishing zones, the implications are global.

This finding underscores an urgent need to reconsider bottom trawling practices, not only for their ecological impacts but also for their role in climate dynamics. Marine protected areas and bottom trawling bans could play a vital role in preserving the ocean's function as a carbon sink. As the climate crisis intensifies, protecting the seafloor may prove as important as conserving forests.

Main photo: Tube worms and brittle stars thriving in mud bottom. Photo Oceana