Environmental Implications of Intensive Marine Aquaculture in Earthen Ponds

In recent decades, the importance of marine aquaculture has grown substantially in most countries. Following a period of uncontrolled activities, the concern for the environmental implications of intensive mariculture has increased notably, and environmental impact is often taken into account when aquaculture activities are established. Among the most important pollutant effects of aquaculture are the outputs of dissolved nutrients, suspended solids and organic matter. In the present study, we have determined the loadings of dissolved nutrients (ammonium, nitrite, nitrate and phosphate), total suspended solids (TSS) and organic matter (particulate organic matter (POM) and biochemical oxygen demand (BOD5)) in the effluent of a marine fish farm devoted to the intensive culture of gilthead seabream (Sparus aurata) in earthen ponds. Samples of seawater were taken monthly during a two-year period (April 1997–March 1999) in the two inflows and the outflow of the fish farm. The environmental impact of marine aquaculture was established by estimating the total amount of each compound discharged into the receiving waters as a direct consequence of the culture activities. Thus, 9104.57 kg TSS, 843.20 kg POM, 235.40 kg BOD, 36.41 kg N–NH4+, 4.95 kg N–NO2−, 6.73 kg N–NO3− and 2.57 kg P–PO43−, dissolved in the seawater, were estimated to be discharged to the environment for each tonne of fish cultured.