Screening and assessing physical pressures affecting seafloor integrity in the Μediterranean region

Abstract

Ecosystem based management requires assessment of human activities and generated pressures that cause physical disturbance and loss of the seabed within the Mediterranean, also accounting for the strength of their interaction. To support the implementation of Descriptor 6 of the Marine Strategy Framework Directive (MSFD), the present work aimed at testing the applicability of an exposure-effect methodology and harmonizing - across countries sharing the same marine waters - the identification of the MSFD key physical pressures on benthic habitats and their relative importance at different spatial scales (national, subregional, regional) in the Mediterranean Sea. The methodology uses 24 MSFD relevant human activities, five physical pressures, and 13 Broad Habitat Types (BHT). Τhe links between human activities, physical pressures and the different MSFD Broad Habitat Types affected are identified and scored using three criteria; namely Spatial Extent, Frequency of Occurrence, and Degree of Impact. The methodology assesses the risk of pressures in a semi-quantitative way, integrating both quantitative (data) and qualitative (expert judgement) information, where quantitative data is not available, and allows the ranking of the physical pressures affecting the seafloor. The methodology was applied in the marine waters of Italy, Slovenia, Croatia and Greece. Abrasion (e.g., related to fishing or boating) and sealing (e.g., caused by structures) were ranked as top pressures; the former is widespread over different BHTs, in a persistent manner and presents intense impacts; the latter appears locally, at specific sites, and persistently, generating an acute impact. According to the results, the infralittoral and circalittoral habitats are those most affected by physical pressures. The identification of major pressures can assist considerably towards the elimination or mitigation of the impacts through actions on the human activities, as it enables the prioritisation of tailor-made measures to achieve or maintain the Good Environmental Status (GES) in the region.