Interactions of Cd and Cu in anaerobic estuarine sediments. II. Bioavailability, body burdens and respiration effects as related to geochemical partitioning

Abstract

Abstract-The relationship between Cd and Cu distribution in sediment geochemical fractions and their bioavailability was studied. A fine-sandy textured estuarine sediment was treated with all combinations of 0, 2.5, and 5 mg/kg Cd and 0, 12, and 25 mg/kg Cu using the chloride salts of each metal. Grass shrimp (Palaemonetes pugio), blue mussel (Mytilus edulis), and hard clam (Mercenaria mercenaria) were exposed to the treated sediments in aquaria with 20 ppt artificial seawater for 14 d. Sediments were sequentially extracted before and after organism exposure to determine the exchangeable, easily reducible, organic-sulfide, moderately reducible, and acid extractable phases. Low mortalities were observed for all organism types and none were attributable to any of the treatments. The Cd and Cu concentrations in the easily reducible and organic-sulfide phases were found to be significantly related to the bioavailability of these metals. The most highly significant relationship was established between Cd in the easily reducible phase and body burden of Cd in the blue mussel. Notable interactions were found between Cd and Cu in some of the geochemical phases, body burdens, and respiration rates. Metal uptake, respiration, and interactions were highly dependent on the test species. A significant correlation was found between increased body burden and depressed respiration for Cd but not for Cu. Multiple regression models are used to describe these relationships. It appears that the interactive responses in the organisms are driven primarily by the sediment geochemical effects and mediated by individual organism processes. These results underscore the necessity of multicomponent (multielement) studies in assessing the fate and effects of toxic elements in the environment.

Interactions of Cd and Cu in anaerobic estuarine sediments. I. Partitioning in geochemical fractions of sediments

“…This study demonstrated that in sediments having excess sulfide, added Cu resulted in the liberation of Cd into more biologically available geochemical phases and increased the extractability of the Cd in the OSP, the largest reservoir for Cd. As shown in part II of this paper [25], biological uptake of the metals, especially Cd, is increased by this shift in geochemical phase distribution.…”

“…The time component of the interactions signified that the majority of both metals precipitated or were sorbed rapidly into the OSP upon their addition to the sediments and over the next few days, geochemical reactions occurred that caused the phase shifts. These reactions must have occurred in a relatively short time because biological responses to interactions also took place (see part II; reference [25]). Other facts indicate that metal distribution stability was reached within a short (hours or few days) time: (1) the sediments were thoroughly mixed after metal addition and equilibrated before the bioassay was started and (2) there was no change in phase distribution of the 0 treatment from before the spiking process until the end of the bioassay.…”

Copper Toxicity to Larval Mercenaria Mercenaria (Hard Clam)

“…Although extensive literature exists for metal toxicity to embryonic, larval [8][9][10][11], and adult bivalves [12][13][14], there is little recent literature relevant to larval M. mercenaria and copper toxicity [15][16][17]. One of the most frequently cited references, Calabrese et al [16], reported values of the lowest concentration at which 5% of the organisms died (LC5), at which 50% died (LC50), and at which 95% died (LC95) of 4.9, 16, and 28 g/L, respectively, for 2-d-old larval clams exposed to varying copper concentrations in a static renewal dosing scheme [16,17].…”

Copper toxicity to larval Mercenaria mercenaria (hard clam)

“…Although extensive literature exists for metal toxicity to embryonic, larval [8–11], and adult bivalves [12–14], there is little recent literature relevant to larval M. mercenaria and copper toxicity [15–17]. One of the most frequently cited references, Calabrese et al [16], reported values of the lowest concentration at which 5% of the organisms died (LC5), at which 50% died (LC50), and at which 95% died (LC95) of 4.9, 16, and 28 μg/L, respectively, for 2‐d‐old larval clams exposed to varying copper concentrations in a static renewal dosing scheme [16,17].…”