Mobility and potential toxicity of sediment-bound metals in a tidal estuary

Abstract

Sediment toxicity in the Gironde Estuary, France, a site contaminated by such trace metals as Cd, Cu, and Zn, was examined monthly from March to October 1997, using concurrently geochemical procedures to assess the mobility of contaminants and ecotoxicity tests with invertebrate larvae (the oyster Crassostrea gigas, the sea urchin Paracentrotus lividus, and the copepod Tigriopus brevicornis). Higher mobility of Cd than of Cu and Zn was shown by desorption tests. Both the gross concentrations of Cu and Zn in the sediment and the mobility of these metals showed a temporal evolution, and changes in the toxicity of the sediment to invertebrate larvae generally were observed concomitantly. Little damage was registered in the spring, and greater damage was found in the summer and fall. Positive correlations were shown between mortality in copepods or abnormalities in oyster larvae with the quantities of metals remobilized from sediment at pH 4. On the contrary, no clear temporal trend was shown for total PAH levels in sediment. These correlations and previous toxicological data suggest that sediment-bound metals, particularly Cu and Zn, possibly play a role in biological responses.

Hepatic proteome changes in Solea senegalensis exposed to contaminated estuarine sediments: a laboratory and in situ survey

“…However, metallic and organic contaminants may be differentially released from sediments, since the latest are the most insoluble and reveal complex desorption from sediments, depending on the toxicant's class and the characteristics of the sediment's organic matter (Kukkonen et al 2003). Metals, on the other hand, tend to form complexes with other mineral substances and their release to water may be greatly affected by pH and redox status changes (Geffard et al 2005;Du Laing et al 2009). In fact, redox potential (Eh) and sediment pH are interlinked, since oxidation, for example driven by sediment disturbance and subsequent re-oxygenation of anoxic layers, leads to acidification, which on its turn favours release of metals from sediments and avoids its deposition (refer to Du Laing et al 2009, for a review).…”

Response of Copepods to Elevated pCO2 and Environmental Copper as Co-Stressors – A Multigenerational Study

“…One such example is the existence of elevated levels of xenobiotics. Metal contaminants are a particular concern for coastal ecosystems, especially soft sediment habitats where metals typically accumulate to greater concentrations than in the overlying water [20]–[21]. Differences in toxicity have been related to differences in metal binding sites between bottom waters, sediment pore water, suspended particles and sediments [22]–[23]; for example, cadmium and copper are most toxic in sediment pore waters [22]–[23].…”

“…Differences in toxicity have been related to differences in metal binding sites between bottom waters, sediment pore water, suspended particles and sediments [22]–[23]; for example, cadmium and copper are most toxic in sediment pore waters [22]–[23]. Toxicity tests involving sediment-bound copper revealed enhanced copper mobilisation at pH 4 relative to pH 7 [21]. As pH decreases, copper bioavailability increases by the increase in free copper ion concentration [24], and hence toxic effects may be encountered.…”

“…We utilised the harpacticoid copepod Tisbe battagliai as a test species. Tisbe is well suited to multigenerational studies due to its ease of culture, rapid life cycle and pedigree in ecotoxicology studies; including assessing the impacts of ocean acidification [16], [21], [38]–[42]. Harpacticoid copepods are an integral component of meiofaunal communities.…”

How to Improve Toxicity Assessment? From Single-Species Tests to Mesocosms and Field Studies

“…Then the test organisms may be exposed to (1) dilution series of the effluent as recommended in the USEPA's whole effluent toxicity testing program (http://water.epa.gov/scitech/methods/cwa/wet/), (2) different concentrations of total decanted sediment (reflecting whole-sediment toxicity), or (3) sediment elutriates (a treatment reflecting the toxicity of the contaminant fraction which can be released from sediment during resuspension, for instance on the occasion of a dredging operation) (Geffard et al, 2005). Then the test organisms may be exposed to (1) dilution series of the effluent as recommended in the USEPA's whole effluent toxicity testing program (http://water.epa.gov/scitech/methods/cwa/wet/), (2) different concentrations of total decanted sediment (reflecting whole-sediment toxicity), or (3) sediment elutriates (a treatment reflecting the toxicity of the contaminant fraction which can be released from sediment during resuspension, for instance on the occasion of a dredging operation) (Geffard et al, 2005).…”