Functional role of biofouling linked to aquaculture facilities in Mediterranean enclosed locations

Biofouling is generally considered a serious threat for human coastal activities such as aquaculture, and the ecological role of fouling organisms associated with fish-farm cages remains one of the most debated topics in the ecological field. However, although biofouling may cause significant problems related to human health, environmental impact and financial losses, in the past decade there has been an increasing interest in developing methods to promote the growth of biofouling on artificial structures as a strategy to mitigate human impacts and reduce the organic enrichment caused by net-cage fish farming. Here we investigated the filtration activity of biofouling assemblages colonizing artificial substrata located within a harbor. The main objective of the study was to determine if and how changes in composition and functioning of biofouling may be affected by hypoxic conditions that periodically occur within the port site selected for this study. To this purpose, artificial panels were used as biofouling collectors and were brought back to the laboratory seasonally where they were divided in 3 subgroups and acclimated at 3 different oxygen levels to mimic the naturally occurring oxygenic conditions. Clearance and respiration rates of each community were measured 6 and 24 h after the beginning of each treatment. Regardless of experimental conditions, performance of the communities was affected by the seasonality and the amount of biomass recruiting on the panels, mainly composed of crustaceans, ascidians, polychaetes, seaweeds and several introduced species. Our study demonstrated that, in particular cases, fouling assemblages linked to aquaculture facilities may contribute to reducing environmental impact and at the same time may serve as input for their re-use in different disciplines.