Assessing the Influences of Large-Scale Disturbance on Sedimentary Marine Carbon Stores

Shelf and coastal seas hold vast quantities of sedimentary carbon which contribute to atmospheric carbon dioxide removal and long-term carbon storage. However, the stability and resilience of this key component of global natural capital remains poorly quantified, particularly under anthropogenic stressors. Demersal trawling activity is the most significant cause of widespread anthropogenic disturbance to the seabed, leading to massive sediment resuspension events and wide scale impact to benthic communities. The impacts of trawling on benthic ecosystems and biodiversity are well reported and understood within the literature (e.g. Jones, 1992; Rijnsdorp et al., 2016); however, a knowledge gap remains regarding the post-trawl fate of sedimentary carbon (van de Velde et al., 2018).

In order to gain a better understanding of the post-disturbance effects of carbon cycling in marine sediments, an experimental trial to mimic fishing impacts was created. Over a 21-day period, a series of closed-tank incubation experiments investigating the impact of simulated benthic fishing gear penetration depth in soft sediments was conducted. Here, marine sediments underwent an artificial disturbance event every 24 hours, with a series of varying depth regimes used. We hypothesise that the large-scale resuspension events caused by trawling may contribute towards an enhancement in localised carbon cycling, and thus a reduction in the net carbon storage within these sediments. The aim of this experiment was to better understand the biogeochemical processes which occur in marine sediments during massive resuspension events, with a particular emphasis on the fate of resuspended organic carbon matter and its potential vulnerability. Dissolved organic carbon and various macronutrients of interest (e.g. PO₄, SiO₂, NH₄, NO₂, NO₃) were also measured.

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Rijnsdorp, A.D., Bastardie, F., Bolam, S.G., Buhl-Mortensen, L., Eigaard, O.R., Hamon, K.G., Hiddink, J.G., Hintzen, N.T., Ivanović, A., Kenny, A., Laffargue, P., Nielsen, J.R., O’Neill, F.G., Piet, G.J., Polet, H., Sala, A., Smith, C., Van Denderen, P.D., Van Kooten, T., Zengin, M., 2016. Towards a framework for the quantitative assessment of trawling impact on the seabed and benthic ecosystem. ICES J. Mar. Sci. 73, i127–i138. https://doi.org/10.1093/icesjms/fsv207

van de Velde, S., Van Lancker, V., Hidalgo-Martinez, S., Berelson, W.M., Meysman, F.J.R., 2018. Anthropogenic disturbance keeps the coastal seafloor biogeochemistry in a transient state. Sci. Rep. 8. https://doi.org/10.1038/s41598-018-23925-y