Assessing the vulnerability of marine sedimentary organic carbon : the influence of anthropogenic disturbance

Abstract

As anthropogenic carbon dioxide (CO₂) concentrations rise, there is an increasing need to re-evaluate our understanding of the complex interactions involved within the global carbon (C) cycle. C stored within marine sediments have previously been largely overlooked and unaccounted for, despite their potential role in climate regulation and mitigation. Recent research over the past decade has identified inshore and coastal sediments as being significant organic carbon (OC) accumulation and burial hotspots, leading to the long-term storage of OC in these widespread depositional environments. In comparison, little is known about the potential vulnerability of sedimentary OC to anthropogenic disturbance (e.g., bottom fishing). Bottom fishing results in the resuspension of sedimentary OC, removing it from sites of burial and long-term storage. Once disturbed, sedimentary OC may be transported, consumed, and/or remineralised into CO₂. This activity may result in net changes of sedimentary OC, further altering the dynamics of the natural C cycle.

In this study, we use a combination of experimental procedures coupled with GIS mapping to develop a new methodology to estimate the potential vulnerability of sedimentary OC stores to bottom fishing pressures. In addition, we contribute knowledge about the interactions between biogeochemical cycles within post-trawl environments and examine pre-existing knowledge across various disciplines to better understand the long-term disturbance history of bottom fishing on marine sediments within UK waters.

This study indicates that sediments within the UK Exclusive Economic Zone (EEZ) have likely undergone significant physical and biogeochemical disturbance since the 1950s, particularly within fine grained sedimentary environments which have been determined to be potentially most vulnerable to fishing disturbance. The methodology developed in this study has allowed for the first complete OC vulnerability estimate of UK EEZ marine sediments and will likely play a significant role in future research and policy planning.