Abstract
The effect of shrimp aquaculture effluents on some environmental parameters of the receiving coastal waters was assessed. Water and sediment samples were taken at different distances from the discharge point (50, 150, and 300 m) when shrimp farms had ceased operations (survey 1), had initiated operations (survey 2), and during the early harvest (survey 3). Water and sediment samples were likewise taken at the same distances from the shore in a non-impacted area. During surveys 1 and 2, the effluents had a negative effect at all three distances (50, 150, and 300 m) on the water quality variables (transparency, seston [total suspended solids, total inorganic solids, particulate organic matter], chlorophyll a, N-NO2–, N-NO3–, N-NH4+), on the sediment quality parameters (organic nitrogen), and on the TRIX index. Contrarily, no differences were observed when the impacted and non-impacted areas were compared during survey 3, probably because the effluents had diminished due to the premature harvesting. The results suggest that at the end of the farming period, the nutrient and organic matter load exceeded the assimilation capacity of the ecosystem, whereas during the recess period, the environment was capable of assimilating the excess organic matter accumulated. The levels reached by the monitored parameters did not exceed the limits established and the impact on the ecosystem is not severe, but they could represent a risk factor in the long term. Additionally, there is evidence that the temporary suspension of shrimp farming operations is beneficial for the environment.
Highlights
Coastal areas are of particular ecological and economic importance as they provide direct and indirect goods and services to society, especially those related to productive activities like fishing, tourism, aquaculture, among others
The results suggest that at the end of the farming period, the nutrient and organic matter load exceeded the assimilation capacity of the ecosystem, whereas during the recess period, the environment was capable of assimilating the excess organic matter accumulated
Total suspended solids (TSS), total inorganic solids (TIS), chlorophyll a, N-NO2, N-NO3, N-NH4+, Total Kjeldahl nitrogen (TKN), P-PO4, total phosphorus, and the trophic state index (TRIX) index varied both according to sampling date and area
Summary
Coastal areas are of particular ecological and economic importance as they provide direct and indirect goods and services to society, especially those related to productive activities like fishing, tourism, aquaculture, among others. La zona costera es de especial importancia ecológica y económica ya que proporciona bienes y servicios directos e indirectos a la sociedad, especialmente a través de actividades productivas tales como la pesca, el turismo, la Ciencias Marinas, Vol 40, No 4, 2014 important to establish the ecological values of coastal ecosystems in order to maintain the desired environmental conditions (Lundin 2000, Wulff et al 2001). Shallow coastal waters can have higher bioproductivity than the most productive areas on land (Rosenberg 1985). Many coastal areas worldwide are currently experiencing eutrophication and/or hypernutrification, with negative consequences for the health of the ecosystems
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