Modelling copper bioaccumulation in Gammarus pulex and alterations of digestive metabolism

Abstract

Bioaccumulation enables to integrate the ability of aquatic organisms to regulate metals and effects of water chemistry on metal bioavailability. Linking this process to biological responses offers thus promising lines of enquiry for protecting aquatic ecosystems. This study aims at characterizing the mechanisms involved in waterborne Cu bioaccumulation and assessing metal impact on digestive metabolism in an ecosystem engineer widely distributed in Europe, Gammarus pulex. The organism was exposed to several Cu concentrations (from 0.5 to 100 μg/L) in aquatic microcosms to establish kinetic parameters for the construction and comparison of two bioaccumulation models, i.e. the biodynamic and saturation models. Cu uptake was recorded in waters exhibiting various concentrations of Na, Mg and Ca at environmental levels to assess the influence of cationic composition on bioaccumulation. Then, the effect of increasing Cu in exposure media on the digestive metabolism of G. pulex was investigated by measuring enzymatic activities (β-glucosidase, N-acetyl-β-glucosaminidase, β-galactosidase). We showed that the saturation model is more suitable than the biodynamic model to describe Cu bioaccumulation in gammarids due to a maximal capacity of animals to accumulate the metal. Cationic composition of water affected insignificantly Cu uptake. All activities of tested enzymes decreased with increasing Cu in exposure media but with different degrees. High correlations were established between the inhibition of enzymatic activities and amounts of Cu bioaccumulated by gammarids. These biological responses could thus provide early-warming of Cu impact on aquatic biota.

Seawater temperature effect on metal accumulation and toxicity in the subantarctic Macquarie Island isopod, Exosphaeroma gigas

“…Uptake rate was shown to be dependent on Cu exposure concentration (C w ). Higher uptake rates linked to elevated metal concentration in other aquatic invertebrates have been reported elsewhere (Wang, 2001;Casado-Martinez et al, 2009b;Lebrun et al, 2012). K u values vary between species depending on physiological characteristics, and physiochemical water parameters (Yu and Wang, 2002;Rainbow et al, 2003;Croteau and Luoma, 2007;Zhao et al, 2009).…”

To what extend the dam dredging can influence the background level of metals in the Rhine River: using chemical and biological long-term monitoring to answer

“…During annual hydrological cycles, the highest variations in metal contents in caged mussels were observed for Cr, Ni and Pb (RSD 40-50%; dredging period excluded). The lowest variations were for Cu and Zn (RSD < 15%), which are essential metals known to be actively regulated by aquatic organisms including bivalves and are required at levels relatively constant to meet the organisms' physiological needs (Bourgeault et al, 2010a;Lebrun et al, 2012;Verschoor et al, 2012;Lebrun et al, 2014).…”

“…In various freshwater species including zebra mussels, calcium cations are usually reported to compete with metals at the binding sites of biological membranes, decreasing subsequently bioavailability for almost all tested metals (Komjarova and Blust, 2009;Bourgeault et al, 2010a;Peters et al, 2011;Urien et al, 2015). Nevertheless, effect of Ca on Cu uptake by aquatic organisms remains poorly documented and anecdotal insofar as Cu is assumed to cross biological membranes through Cu-specific or Na channels (Lebrun et al, 2012). Positive Na effect on Zn and Ni contents in caged mussels can be explained by physiological responses to counteract the effect of low salinity on ionoosmoregulation, as described in amphipods (Marsden and Rainbow, 2004;Verschoor et al, 2012).…”

“…Locally, the International Commission for the Protection of the Rhine (CIPR) have defined reference objectives not to exceed for the metallic contamination of suspended particulate matter or SPM (Report CIPR n 193, 2008). Nevertheless, these chemical analyses do not give information about the bioavailability of metals that is the fraction internalized in biological tissues and potentially toxic for biota (Bourgeault et al, 2010b;Lebrun et al, 2012). Besides, they provide only a snapshot of the occurrence of metals that is not representative of temporal fluctuations of contamination levels and metal partitioning related to environmental and hydrological conditions or/and changes in pollution discharges.…”

Copper sulphate reduces the metabolic activity of Gammarus fossarum in laboratory and field experiments

“…Contamination of leaf litter with copper can happen, for example, in vineyards where fungicides containing copper are applied. Owing to its non-degradability, copper moves up food webs and is distributed in the entire biotic compartment of freshwaters (Lebrun et al, 2012). Copper concentrations in natural unimpacted waters are mainly influenced by the geology of the watershed of the area and are typically less than 4 g/L (Schönborn and Risse-Buhl, 2013).…”