Trawling activities impact the sediment transport mechanisms along the Oreto submarine canyon (SW Mediterranean)

International Conference on Seafloor Forms, Processes and Evolution, 4-6 July 2022, Valletta, Malta

There is increasing evidence that bottom trawling within and around submarine canyons can alter their natural sedimentary dynamics. This anthropogenic activity can resuspend bottom sediments and favor their transference from fishing grounds towards deeper regions, forming nepheloid layers with high concentrations of particulate matter at different water depths. However, studies addressing this topic are still scarce and mainly devoted to the NW Mediterranean. In the Gulf of Palermo (SW Mediterranean), bottom trawling occurs on the outer shelf and on the upper continental slope, but mainly concentrates within the Oreto Canyon. The temporal evolution of the sediment transport in the lower part of the Oreto Canyon was assessed by analyzing 5 months of moored turbidity and currentmeter data, from July 2016 to January 2017. This study was carried out as part of the EUFP7 Eurofleets-2 ISLAND research cruise that aimed to explore Sicilian canyon morphologies, benthic habitats, and sedimentary dynamics in relation with trawling activities. Time-series analyses, combined with hydrographic data collected along the Oreto canyon axis, revealed the presence of nepheloid layers coinciding with periods of higher fishing activity within the canyon. In contrast, very low turbidity values were recorded in the hydrographic profiles collected along the nearby Eleuterio Canyon, mainly because trawling activities are not practiced within this canyon due to its rough geomorphology. Considering the global widespread of bottom trawling, similar alterations of the contemporary sediment transport mechanisms could be expected in other trawled canyons elsewhere, alongside with the ecological consequences that may arise from this human activity.

Peer reviewed