Modeling the effect of water chemistry on the bioaccumulation of waterborne cadmium in zebra mussels

Abstract

The present study aims at investigating the effects of Zn, Ca, and dissolved organic carbon (DOC) on the waterborne Cd bioaccumulation of a freshwater bivalve (Dreissena polymorpha). Mussels were exposed for 48 h at 3 µg/L of Cd in different media. Their physiological activities were assessed by separately measuring the filtration rate in the same exposure water. Increased Zn (from 3 to 89 µg/L) and Ca (from 37 to 131 mg/L) concentrations in water led to a threefold and sevenfold reduction of Cd bioaccumulation, whereas the effect of DOC varied greatly depending on its concentration. At low DOC concentrations (from 0.2 to 1.1 mg/L), the uptake of Cd increased, whereas at higher concentrations (from 1.1 to 17.1 mg/L), the uptake decreased. The filtration activity was not strongly influenced by either Zn or Ca concentration, whereas it was modified in enriched DOC media in the same manner as Cd uptake. A competitive model was built to predict the waterborne uptake rate constant of Cd (k (u)) as a function of Zn and Ca concentrations in the water. Over the range of DOC concentrations we tested, organic matter was shown to influence Cd bioaccumulation in two ways: by modifying Cd speciation and thus its bioavailability and its interaction with the biological membrane, and by affecting the mussel's physiology and therefore its sensitivity to metal. The present study provides a useful means of adjusting the toxicokinetic constant to the water's physicochemical characteristics and proposes a unifying model that takes into account the different geochemical and biological influences on bioaccumulation.

Modelling copper bioaccumulation in Gammarus pulex and alterations of digestive metabolism

“…The major forms of bioaccumulated metal are represented by the free ions, which can directly interact with transport sites and across the biological membranes of aquatic organisms (Niyogi and Wood 2004). Nevertheless, competitions for the same transport sites may occur between free metals and major ions found in freshwaters, leading to a decrease in metal uptake (Bourgeault et al 2010;Komjarova and Blust 2009). In G. pulex, increasing concentrations of Ca in water inhibits the uptake of Ni and Cd (Lebrun et al 2011;Pellet 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

“…By contrast, the dissolved fraction was the preponderant of exposure route for Cd and Mn. Such significant uptake of Cd from the dissolved fraction has been reported in zebra mussels in laboratory conditions (Bourgeault et al, 2010a). The low effect of exposure levels on bioaccumulation of Mn in caged mussels can be due both to variations in total concentrations in the Rhine water that are too low to induce significant changes in bioaccumulation (Fig.…”

“…5), which are thus mobile and available for aquatic organisms, as showed for gammarids with Cd and Cu (Pellet et al, 2009;Ferreira et al, 2013). For Cr and Pb, the increase in bioaccumulation could be explained by the enrichment of the effluent of pumping/dilution in organic matter and changes in SPM properties, hence enhancing their particulate bioavailability and subsequently their assimilation by mussels (Roditi et al, 2000;Bourgeault et al, 2010a;Bourgeault et al, 2011). By contrast, Cu and Zn concentrations in exposed mussels were lower than unexposed mussels.…”

“…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).…”

“…Cd, Co, Cr, Cu, Mn and Ni, whereas Na concentration essentially increased Ni and Zn bioaccumulation in caged mussels. 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).…”