Benthic community structure and biomarker responses of the clam Scrobicularia plana in a shallow tidal creek affected by fish farm effluents (Rio San Pedro, SW Spain)

UNITWIN/UNESCO/WiCoP, Physical Chemical Department, University of Cádiz, Campus de Excelencia Internacional del Mar-CEIMAR, Polígono Río San Pedro s/n, 11510 Puerto Real, Cádiz, Spain.
Environment international (Impact Factor: 5.56). 07/2012; 47:86-98. DOI: 10.1016/j.envint.2012.06.008
Source: PubMed


The effects of solid organic wastes from a marine fish farm on sediments were tested using benthic community as ecological indicators and biomarkers in native clam (Scrobicularia plana) as biochemical indicators. The benthic fauna and clam samples were collected in the intertidal sediment in October 2010 from five sites of the Rio San Pedro (RSP) creek, following a gradient of contamination from the aquaculture effluent to the control site. Numbers of species, abundance, richness and Shannon diversity were the biodiversity indicators measured in benthic fauna. Morphological and reproduction status of clams were assessed using the condition factor and gonado-somatic index, respectively. Phase I and Phase II detoxification enzymatic activities (ethoxyresorufin O-deethylase (EROD), glutathione S-transferase (GST)), antioxidant enzymatic activities (glutathione peroxidase (GPX), glutathione reductase (GR)) and oxidative stress parameters (Lipid Peroxidation (LPO) and DNA strand breaks) were measured in clams' digestive gland tissues. In parallel, temperature and salinity in the adjacent water, redox potential, pH and organic matter in sediment, and dissolved oxygen in the interstitial water were measured. The results suggested that RSP showed a spatial gradient characterised by hypoxia/anoxia, reduced potential, acidic conditions and high organic enrichment in sediments at the most contaminated sites. Significant (p<0.05) decrease of biodiversity indicators were observed in the areas impacted by the aquaculture discharges. Biomarkers did not show a clear pattern and of all biochemical responses tested, GPX, DNA damage and LPO were the most sensitive ones and showed significant (p<0.05) increase in the polluted sites. Benthic biodiversity indicators were significantly (p<0.05) positively correlated with pH, redox potential and dissolved oxygen and negatively correlated with organic matter. On the contrary, antioxidant enzymatic responses (GPX) and oxidative stress parameters were significantly (p<0.05) negatively correlated with those physico-chemical parameters. It has been demonstrated that effluents from fish aquaculture activities in Río San Pedro creek may produce an alteration of physico-chemical characteristics of seabed and induce oxidative stress and DNA damage in soft-sediment species which may lead to changes of the benthic population structure and health status of the exposed organisms.

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    • "In other words, SOD and GST are biomarkers of exposure but do not describe an ecologically relevant effect. There is emerging evidence, however, that suggests antioxidant biomarkers in bivalves are correlated with benthic biodiversity (Silva et al., 2012). Our data showed an increase in GST and SOD activity at the R2 site located 200 m upstream from the WWTF outfall , but downstream from the urbanized area of Lewiston/Auburn, ME, USA. "
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    • "Different works showed that stress related biomarkers are powerful tools to assess the biological effects of contamination in bivalves, both under environmental and laboratory conditions. Biomarkers such as antioxidant enzyme activity (superoxide dismutase, catalase, glutathione peroxidase , glutathione reductase) or oxidative stress parameters (lipid peroxidation, DNA strand breaks) have shown to be useful to assess organisms impacts due to stress conditions (among others, Dellali et al., 2004; Geret and Bebianno, 2004; Bebianno and Barreira, 2009; Ramos-Gómez et al., 2011; Wang et al., 2011, 2012; Freitas et al., 2012a; Silva et al., 2012). Thus, the present work aims to study the biochemical alterations resulting from impacts of salinity changes in three Veneridae clams (V. "
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    • "Increase in LPO was also observed in N. diversicolor exposed to contaminated sites in Portugal (Moreira et al., 2006). Recently, Silva et al. (2012) showed that in Scrobicularia plana LPO levels increased when the animals were under organic waste contamination from a marine fish farm. Besides LPO alterations reported for organisms under pollution stress, the increase on the activity of antioxidant enzymes (CAT, SOD, GSTs) has been described by several authors (e.g. "
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