Impact of fish farming facilities on Posidonia oceanica meadows: a review

Abstract

The impact of fish farming facilities on Posidonia oceanica meadows was assessed from studies of intensive facilities carried out over the last few years. The disturbances caused by these fish farms were measured by means of both abiotic (light, sediment, interstitial water) and biotic variables (meadow density, leaf biometry, lepidochronology, primary production, epiphytes, reserve carbohydrates in the rhizomes), in function of increasing distance from cages and/or inside a geographically close reference site. The results showed significant degradation of these seagrass meadows in all the sectors investigated. When fish farming cages were placed above a P. oceanica bed, the meadow was severely degraded or disappeared and the sediment showed a strong increase in organic matter that could lead to anoxia phenomena. The irreversible impact of fish farming projects on P. oceanica meadows requires the application of the precautionary principle. Several recommendations (site selection, preliminary studies and monitoring over time) are suggested in order to enable piscicultural activities to be incorporated in a global process of Integrated Coastal Zone Management.

Threats to Ultraoligotrophic Marine Ecosystems

“…In the benthos sedimentation and organic loading can cause biochemical changes affecting the composition and function of benthic communities (Karakassis et al, 2000), stimulating the growth of undesirable species that produce toxic metabolic waste that can kill species of conservation significance. Large-scale Posidonia oceanica losses adjacent to fish farm cages have been reported across the Mediterranean (Pergent-Martini et al, 2006) including the Eastern Mediterranean (Holmer et al, 2008;Apostolaki et al, 2009).…”

Decadal changes in the structure of Cymodocea nodosa seagrass meadows: Natural vs. human influences

“…Table S1). The '500 m-threshold' was somehow a 'rule of thumb', though some evidence has indicated this distance as a 'security buffer' of non-affection over seagrasses (Pergent-Martini et al, 2006;Cabaço et al, 2008).…”

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

“…Fish farm discharges, in particular, cause severe damage to P. oceanica meadows growing nearby (Delgado et al 1999, Dimech et al 2002, Marbà et al 2006, Pergent-Martini et al 2006, Ruiz et al 2010. When extending near fish cages, P. oceanica meadows receive a significant amount of particulate organic matter discharged from these cages .…”