Integrated Multitrophic Aquaculture: Filter Feeders Bivalves as Efficient Reducers of Wastes Derived from Coastal Aquaculture Assessed with Stable Isotope Analyses - Aquaculture and the Environment: A Shared Destiny - page 103

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Integrated Multitrophic Aquaculture:
Filter Feeders Bivalves as Efficient Reducers
of Wastes Derived from Coastal Aquaculture
Assessed with Stable Isotope Analyses
Salud Deudero 1 , Ariadna Tor 1 , Carme Alomar 1 ,
José Maria Valencia 2 , Piluca Sarriera 1 and Andreu Blanco 3
1 Centro Oceanográfico de Baleares, Instituto Español de Oceanografia, Palma
2 Laboratorio de Investigaciones Marinas y Acuicultura, Andratx
3 Instituto de Investigaciones Marinas de Vigo, CSIC, Vigo
Spain
1. Introduction
Aquaculture industry has rapidly increased from 20 million tons in the 1990s to 68.4 million
tons in 2008, overcoming the 67.0 million tons of extractive fisheries, with an approximated
global value of 84,791 million Euros (FAO, 2010). The Mediterranean Sea is an important
producer of intensive open water fish culture, especially important are industries from
Spain, France, Italy and Greece, which generated 2,133 million Euros in 2008 (FAO, 2008).
Parallel to aquaculture industry development, knowledge of its effects on the surrounding
environment is increasing. Several studies have been conducted to assess the environmental
impact (Holmer et al., 2008; Yokoyama et al., 2006; Vizzini & Mazzola, 2004) due to
aquaculture. Organic enrichment is recognized as the most important problem associated to
marine aquaculture (Mirto et al., 2010; Troell et al., 2003) as a direct result of the release of
dissolved and particulate nutrient loads, especially organic phosphorous and nitrogen in the
form of ammonia that might easily induce eutrophication (Karakassis et al., 2000). Uneaten
pellet and fresh food supplied at fish cages, together with the excretion products from
cultured fishes are the source of the nutrient loads released (Cheshuk et al., 2003).
Whereas the dissolved compounds are easily dispersed and diluted in the water column, the
particulate compounds sink to the sea floor, causing severe modifications of the physical
and chemical characteristics of the sediment and the community dynamics of marine
seagrass and benthic fauna (Brown et al., 1987; Karakassis et al., 2000; Mente et al., 2006).
The severity and extend of the environmental impact depends on a large number of factors,
such as local hydrodynamics, water depth and total output from fish farms. Nevertheless, it
has been detected organic enrichment in the sediment up to 1000 m from fish cages (Sarà et
al., 2004).
The effects of the organic enrichment are widely studied in the Atlantic and the Pacific
Ocean, especially in relation to the salmon industry (Brown et al., 1987; Cheshuk et al., 2003;