Damage Control in the Coastal Zone: Improving Water Quality by Harvesting Aquaculture-Derived Nutrients

Abstract

There is a clear relationship between nutrient enrichment and the eventual deterioration of coastal water quality (eutrophication). Eutrophication occurs when the rate of nutrient supply exceeds its transformation or removal rate and excess nutrients stimulate excess biological production. This imbalance may be corrected to varying degrees by enhancing certain natural biological/ecological attributes (ecosystem services), such as the removal of particles by means of filter feeding animals. This topic is addressed by means of a case study - aquaculture in coastal waters. We begin by examining the impacts related to the release of nutrient-rich effluents from a commercial fish farm in the oligotrophic Gulf of Aqaba. This is followed by description of 3 approaches that have been tested as means to capture and remove aquaculture effluents, as an example of how we may enhance the sustainability or reduce the environmental impacts of commercial activities. These approaches include placement of detritus feeding grey-mullets in benthic enclosures on the organically enriched seafloor below commercial fish cages, mooring artificial reefs as benthic biofilters next to fish farms and deployment of pelagic biofilters in the water column, adjacent to fish cages.