Untitled - CNR

Meiofauna as Indicator for Assessing the Impactof Fish Farming in Coastal Marine SedimentsS. MirtoInstitute for Coastal Marine Environment, CNR, Messina, Italysimone.mirto@iamc.cnr.itAbstractThe present study aimed to detect the impact of organic loads due to the biodepositionof a fish farm in a coastal area of the Tyrrhenian Sea (Western Mediterranean).Sediment chemistry and meiofaunal assemblages were investigated from December2006 to October 2007 on seasonally basis at four stations: two were located underthe fish farm, while the others were about 1-km distance, and served as controls.Variations in the biochemical composition of the sedimentary organic matter andmeiofaunal community structure were also related to changes in reared fish biomass.The presence of the cages induced changes in the benthic compartment: the sedimentsshowed reducing conditions. A significant accumulation of biopolymeric carbonwas observed beneath the cages during the entire investigated period, resultingin a reduction of the meiofaunal density in the impacted stations, a higher proportionof meiofauna was observed in the top 2 cm of the sediment. Changes were evidentalso in terms of community structure as meiofauna under the cages, when comparedto the Controls, was characterised by increased importance of polychaetes and copepodsvs. a much lower significance of kynorhynchs and gastrotrichs that we proposedad indicator of organic enrichment. Finally, biodiversity decreased beneath the cagesdue to the disappearance of taxa more sensible to organic accumulation.1 IntroductionThe rapid expansion of marine aquacultureis a potential solution to the problem ofoverfishing and fisheries depletion worldwide,but also a major threat to marineecosystems reducing the value of the naturalcapital and benefits that humans gatherfrom the exploitation of coastal areas’ resources[1]. One of the most widely citedbut poorly quantified impacts of open netpenaquaculture is its release of nutrientsand other wastes to the surrounding environment[2].Aquaculture is a fast-growing industrywhich, through the release of organic andinorganic N and P contributes to the progressiveeutrophication of coastal areas[3, 4]. Aquaculture activities are relevantat local and regional scales, and recentestimates indicate that, in Mediterraneancoastal areas, the release of nutrients fromfish farming contributes for up to 7 and10% of N and P total discharge, respectively[5].Changes induced by aquaculture installationscan have a negative impact on the naturalenvironment, threating the quality ofcoastal zones, and generating conflicts betweenaquaculture and the conservation ofmarine habitats [6].The organic enrichment of the sediments