Abstract
Aquaculture production generates social and economic benefits, but can also cause environmental impacts. The objectives of this study were: a) to characterise the impacts caused by the maintenance of broodstock of the giant river prawn (Macrobrachium rosenbergii) on the physical and chemical characteristics of the water used in culture ponds, and b) to evaluate the relationship between the biomass of the prawns and the impact of culture on the water used in the ponds. Between January and December 2004, we determined, monthly, the biomass of M. rosenbergii by means of biometrics, and the physical and chemical variables of the supply and effluent water from a pond used to maintain breeding stock. The results showed that the effluent water had higher contents of chlorophyll-a, suspended particulate matter (SPM), pH, dissolved oxygen, total Kjeldahl nitrogen (TKN) and dissolved Kjeldahl nitrogen (DKN), inorganic nitrogen (IN), total (TP) and dissolved phosphorus (DP), and P-orthophosphate than the supply water. The highest biomass of M. rosenbergii occurred in April (127.0 g.m-2) and the lowest in August (71.5 g.m-2), and there were positive linear correlations between the biomass of the prawns and the intensity of the increases in TKN, DKN, IN, TP, and DP of the water used in the pond. The maintenance of broodstock of M. rosenbergii increased the chlorophyll-a, SPM, nitrogen, and phosphorus contents of the water in the pond. Additionally, the increase in the biomass of the prawns intensifies the export of nitrogen and phosphorus from the pond in the effluent.
Highlights
World production of the giant river prawn (Macrobrachium rosenbergii De Man, 1879) has grown considerably in recent years, mainly in Asian countries (New, 2005)
The objectives of this study were a) to characterise the impacts caused by the maintenance of Macrobrachium rosenbergii broodstock on the physical and chemical characteristics of the water used in the ponds in terms of load, and b) to evaluate the relationship between the biomass of prawns and the impact of this culture on the water used in the pond
The maintenance of broodstock of Macrobrachium rosenbergii at biomass levels between 71.5 and 127.0 g.m–2 increased the contents of suspended particulate matter (SPM) and chlorophyll a in the water used in the culture pond
Summary
World production of the giant river prawn (Macrobrachium rosenbergii De Man, 1879) has grown considerably in recent years, mainly in Asian countries (New, 2005). Different studies on culture ponds of marine shrimps have shown that the effluents from these ponds are enriched in nitrogen, phosphorus, and organic matter (Lin et al, 2005; CasillasHernández et al, 2006; Anh et al, 2010). These effluents are generally discharged untreated into aquatic environments and contribute to the process of artificial eutrophication, which causes changes in the biodiversity and the physical and chemical characteristics of the water in the environments that receive these effluents (Beardmore et al, 1997). The eutrophication increases the cost of treating the water for human consumption because of the need to use more sophisticated technologies to remove organic matter, nutrients, pathogenic organisms, and other impurities from the water (Tundisi and Tundisi, 2008)
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