Fate of copper in intensive shrimp farms: bioaccumulation and deposition in pond sediments

Ld Lacerda,Ja Santos,Dv Lopes

doi:10.1590/s1519-69842009000400012

Abstract

We present the distribution of Cu in water, sediments and biomass from intensive shrimp (Litopenaeus vannamei Boone, 1931)) farming in northeastern Brazil. The results show no difference in dissolved Cu concentrations between waters entering and leaving the ponds. However, there was a large export of particulate Cu to adjacent environments, showed by extremely high particulate (112 microg.L-1) Cu concentrations in draining waters. Copper concentrations in the bottom sediments of the pond varied with depth from 10 to 20 microg.g-1, being 5 to 7 times higher than the local background. Pond management procedures result in a peculiar vertical distribution of Cu with peak values occurring at sub-surface depths in pond bottom sediments. Bioavailable Cu reaches about 20% of the total Cu content in sediments. Notwithstanding the relatively high Cu bioavailability, concentrations in shrimp muscle (23.2 to 63.4 microg.g-1 d.w.) were similar to reported values for reared and natural L. vannamei populations, and much lower than acceptable maximum limits for human consumption. Concentrations in the exoskeleton were always higher than in muscle. Increasing Cu mass, and to a lesser extent Cu concentrations in muscle tissues, occurred simultaneously to a decrease in Cu mass and concentrations in the exoskeleton and vice versa, suggesting a dynamical exchange of Cu between the two compartments. Although Cu fate in intensive shrimp culture does not result in increasing Cu exposure to consumers, the activity is an important source of this metal to adjacent ecosystems, in particular in the pristine environments where most aquaculture activities in NE Brazil takes place.

Highlights

Intensive shrimp aquaculture is a recent development of the Brazilian agribusiness but has increased by about 20% per year during the last decade, along the semi-arid NE coast of Brazil due to the optimal climate and environmental setting
We investigated the fate of Cu in intensive shrimp farms at the Jaguaribe estuary, in particular Cu accumulation in shrimps during a typical growth cycle and accumulation and availability of Cu in pond sediments
The Cu content in the suspended solids increased from 38.4 to 58.3 μg.g–1 in the intake canal and pond waters to 66.8 μg.g–1 in draining waters, changes in concentrations are not the major factor responsible for the large particulate Cu measured in draining waters, rather these high particulate Cu concentrations result mostly from an enormous increase in total load of suspended solids to the canal waters, which increased form a range of 87-164 mg.L–1, in the intake canal and pond waters to 1,675 mg.L–1 in draining waters

Summary

Introduction

Intensive shrimp aquaculture is a recent development of the Brazilian agribusiness but has increased by about 20% per year during the last decade, along the semi-arid NE coast of Brazil due to the optimal climate and environmental setting. 11,050 ha are located along the NE coast with an average annual production of about 66,000 tons (ABCC, 2005). On the Jaguaribe River estuary, in Ceará State, shrimp pond area increased from 820 ha in 2001 to 1,260 ha in 2003 and 1,520 ha in 2004. Average productivity increased from 6.3 t.ha–1/year to 8.2 t.ha–1/year between 2001 and 2003. In 2004, there was an increase in the number of farms (98) and pond area (1,520 ha), but a decrease in the annual production (7,560 tons) and productivity (5.2 t.ha–1/year) due to the spread of typical shrimp illness and worsening environmental conditions, resulting in high (>50%) death rates (MAPA, 2001; ABCC, 2005; Rocha and Rodrigues, 2004)

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Results

Conclusion