Martina Pierdomenico, University of Rome Sapienza, Italy
Eleonora Martorelli, Italian National Research Council, Institute of Environmental Geology and Geo-Engineering, Italy
Tommaso Russo, University of Rome Tor Vergata, Italy
Stefano Ambroso, Institute of Marine Sciences, CSIC, Barcelona, Spain
Andrea Gori, University of Barcelona, Spain
Josep-Maria Gili, Institute of Marine Sciences, CSIC, Barcelona, Spain
Francesco L. Chiocci, University of Rome Sapienza, Department of Earth Science, Italy
Anthropogenic impacts on the megafauna of Vulnerable Marine Ecosystems along the Gioia Canyon (Southern Tyrrhenian Sea)
The Gioia Canyon is a submarine canyon of the Tyrrhenian Calabrian Margin (Central Mediterranean) presently characterized by active sediment transport processes. The canyon head indents the continental shelf up to very shallow depths of about 10 m and it is composed of two branches located just few hundred meters off the entrance of the Gioia Tauro harbor, one of the largest shipping terminals of the Mediterranean Sea. Furthermore, the canyon head is located close to the mouth of a gravel-bed stream known as fiumara, characterized by torrential discharges and high sediment yields.
The Gioia Canyon was selected as a pilot area in the framework of the National Project RITMARE, aiming at a comprehensive characterization of the physical and biological processes in deep sea environments, including the potential alterations of benthic habitats caused by anthropogenic activities. To assess the human impacts on the Gioia Canyon an extensive dataset was collected, including multibeam data, video surveys, sediment samples and oceanographic measurements. Vessel Monitoring Systems data were used to determine the spatial distribution of the fishing effort in the area, to constrain the effects of trawling disturbance on the benthic fauna.
Main results indicate the occurrence of sensitive habitats along the canyon margins, hosting the seapen Funiculina quadrangolaris and the octocoral Isidella elongata, species indicative of Vulnerable Marine Ecosystems. The General Fisheries Commission for the Mediterranean considers these two species relevant in terms of management priorities since they constitute essential habitats for certain crustacean species of commercial interest and are extremely vulnerable to the effects of commercial fisheries.
On the other hand, evidence of multiple anthropogenic activities along the canyon are also present, that may influence the integrity of the described benthic assemblages. Remote Operated Vehicle observations provide clear evidence of diffuse trawl marks over soft sedimentary bottoms and show remarkable quantity of litter within the thalweg area. Litter is mainly distributed at the canyon head, likely due to the very shallow setting and the proximity with the mouth of the Petrace fiumara and the Gioia Tauro harbor. Potential sites of sediment disposal from dredging operations in the harbor are also detected along the outer shelf and at the canyon margins.
Intense trawling activity may be the main factor responsible for the low abundances of megabenthic species observed locally, although the relationship between faunal abundance and intensity of fishing effort is not always univocal. Diffuse epibiosis and necrosis observed on Isidella elongata
colonies also outside the trawled area suggest a critical state of health for these communities, arising concern regarding the conservation status of the benthic ecosystems of the canyon.
Theme 4: Physical and anthropogenic disturbance in submarine canyons, conservation and marine policy
Vulnerable Marine Ecosystems, trawling impacts, littering