Impact of bottom trawling on long-term carbon sequestration in shelf sea
sediments
Abstract
Bottom trawling represents the most widespread anthropogenic physical
disturbance to shelf sea sediments. While trawling-induced mortality in
benthic fauna has been extensively investigated, its impacts on
ecosystem functioning and carbon cycling at regional scales remain
unclear. Using the North Sea as an example, we address these issues by
synthesizing a high-resolution dataset of bottom trawling impact on
sediments, feeding this dataset into a 3-dimensional
physical–biogeochemical model to estimate trawling-induced changes in
biomass, bioturbation and sedimentary organic carbon, and assessing
model results with field samples. Results suggest a trawling-induced net
reduction in macrobenthic biomass by 10-27%. Trawling-induced
resuspension and reduction of bioturbation jointly and accumulatively
reduce the regional sedimentary organic carbon sequestration capacity by
21-67%, equivalent to 0.58-1.84 Mt CO2 yr-1. Our study emphasizes the
need for proper management of trawling on muddy seabeds, if the natural
capacity of shelf seas for carbon sequestration should be conserved and
restored.