Fish farming impact on sediments and macrofauna associated with seagrass meadows in the Mediterranean

Reduced carbon sequestration in a Mediterranean seagrass (Posidonia oceanica) ecosystem impacted by fish farming

“…Release of effluents is usually higher during the warm season in the Mediterranean (summer−autumn) as a result of the enhancement in fish farm production during this period (Karakassis et al 1998). Similar studies in the Mediterranean basin have also reported higher sedimentation during summer, driven by loss of waste products from the fish cages, and subsequent sediment and pore water enrichment (Cancemi et al 2003, Sarà et al 2004, Apostolaki et al 2007. In the present study, however, we found that also during winter, nutrient de position and accumulation in the sediments and pore waters were higher at the cages station compared to the control station.…”

“…The site was characterized by coarse sand (0.45 to 0.90 mm mean diameter pore size), a low percentage of silt and/or clay (4.63 to 4.83%), oxic conditions (292 to 353 mV redox potential) (Apostolaki et al 2007) and 5.5 cm s −1 mean bottom current speed . At the time of the study, the fish farm had been operating for 10 yr, producing on average 400 tons yr −1 of gilthead sea bream Sparus aurata and sea bass Dicentrarchus labrax.…”

“…When extending near fish cages, P. oceanica meadows receive a significant amount of particulate organic matter discharged from these cages . Available studies show that excessive nutrient inputs are deposited beneath the cages (Sarà et al 2004, increasing the sediment (Apostolaki et al 2007) and the pore-water (Cancemi et al 2003) nutrient pools. Redox potential is usually decreased, while sulfate reduction rate is stimulated (Holmer et al 2003a), leading to an in crease of sulfide pools in both the sediment (Pérez et al 2007) and pore water (Calleja et al 2007).…”

“…Most studies have been conducted only during summer (Pergent et al 1999, Ruiz et al 2001, Cancemi et al 2003, Holmer et al 2004, Sarà et al 2004, Apostolaki et al 2007. Research effort has been focused on the warm period, as fish farm production and feed supply are in creased during the summer, causing enhancement of fish farm effluents in the same period (Karakassis et al 1998).…”

Relationship between sedimentation rates and benthic impact on Maërl beds derived from fish farming in the Mediterranean

“…In this work however, macrofaunal community parameters such as abundance and species richness did not peak at an intermediate impact level. As other studies have previously suggested, the macrofaunal community response under the influence of marine aquaculture in the Mediterranean may not always follow the pattern described by Pearson and Rosenberg ( 1978) (Karakassis et al 2000, Apostolaki et al 2007). This fact may be due to the differences in the physico-chemical parameters of the Mediterranean, such as higher temperatures and the different type of sediment (carbonate sediments), compared with areas culturing salmon where most studies have been performed (e.g.…”