Allometry of cadmium and zinc concentrations and bioaccumulation in the scallop Chlamys nobilis

Abstract

Scallops (Bivalvia: Pectinidae) contain very high concentrations of cadmium (Cd) and zinc (Zn) in their body tissues. We investigated the allometry of Cd and Zn concentrations in the scallop Chlamys nobilis and the underlying biokinetic mechanisms. The metal influx rate from the dissolved phase and the weight-specific clearance rate decreased with body size, whereas the dietary assimilation efficiency (AE) increased with increasing body size. The dietary AEs of metals in the scallops were comparable when measured by the mass balance and the dual radiotracer techniques. The efflux rate of Cd in the scallops was lower than those in other bivalves, whereas the efflux of Zn was comparable to those in other bivalves. Growth dilution appeared to be important in the overall metal accumulation in the scallops. The allometric dependencies of the biokinetic parameters were then combined with the measurements of metal concentrations in the water to predict the likely metal concentrations in scallops of different sizes using the biokinetic model. The modeling suggested that the very high AE and low efflux rate for Cd explained the high Cd concentrations in the scallops. Dietary uptake dominated the overall metal accumulation in the scallops. Both the predicted metal concentrations and the allometric coefficients of metals were comparable to the measured values. This study shows, for the first time, that the biokinetic model can be used to predict the effects of body size on the bioaccumulation of metals in marine invertebrates. The allometry of ingestion rate, compared to other biokinetic parameters, is mainly responsible for the allometry of metal bioaccumulation in the scallops. KEY WORDS: Cadmium · Zinc · Scallops · Biokinetic model · Allometry Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 365: [115][116][117][118][119][120][121][122][123][124][125][126] 2008 Neff (2002) concluded that the arithmetic mean concentrations of Cd in scallops were the highest among different species of bivalves (clams, mussels, oysters, and scallops).The concentrations of zinc (Zn) in scallops are also high, especially in the kidney. Bustamante & Miramand (2005) reported a range of 313 to 1062 μg g -1 dry weight Zn in the soft tissues of Chlamys varia, whereas the concentrations of Zn in their kidneys were as high as 38 000 μg g -1. Such concentrations of Zn are probably among the highest recorded among any marine organisms thus far. Although it is safe to consume adductor muscle, which is low in trace metals (Metian et al. 2007a), the increasing inputs of industrial, agricultural, and domestic wastes in coastal waters can accelerate the bioaccumulation of metals in scallops, which may subsequently pose health risks to humans due to the consumption of scallops. Furthermore, scallops have been used as sentinel organisms in environmental monitoring (Cranford et al. 2006). Interpretation of the biomonitoring data often requires a clear understanding of the mechanisms of pollutant ac...

Derivation of allometric relationships for radionuclides in marine phyla

“…The observed scaling of the CF to M −0.25 is compatible with this metabolic explanation, as the CF is the activity concentration in the organism (activity × M −1 ) relative to the medium. In other words, metabolically driven allometry of the ingestion rate could be responsible for the scaling behaviour in the organisms and radionuclides considered, as previously suggested in studies of the uptake of Cd and Zn by marine invertebrates [22]. However, for some elements, the process could also be surface-area driven (e.g.…”

Cadmium accumulation and loss in the Pacific oyster Crassostrea gigas along the west coast of the USA

“…However, the intra-specific difference in clearance rate cannot completely account for the difference in metal uptake rate constants among the bivalves (Chong & Wang 2001). Smaller oysters had higher Cd uptake rate than the larger oysters in the July populations, similar to that observed for Cd and zinc (Zn) uptake in mussels, clams, and scallops , Wang & Dei 1999, Pan & Wang 2008b. In these bivalves, the influx rate decreased in a power function with increasing body size, which may be caused by size-specific metabolic rates (Boyden 1974, Ringwood 1989, Newman & Heagler 1991 or changes in gill surface area.…”

“…The October populations also had higher uptake constants and clearance rates than the July populations. In general, the oysters had 3 to 10 times higher Cd uptake rate constant from the dissolved phase than the other bivalves of similar sizes such as mussels, clams, and scallops (Pan & Wang 2008b). Simultaneously, they had higher clearance rate (10 to 80 l g -1 h -1 ) than the other bivalves (typical clearance rate for clams and mussels: 1 to 10 l g -1 h ).…”

“…Assimilation of metals from phytoplankton by oysters is generally higher than in mussels and clams (Reinfelder et al 1997, Wang 2003. However, assimilation of Cd in oysters is not as high as that by the scallop Chlamys nobilis (> 86%) (Pan & Wang 2008b). Cd uptake from the diet may be the main exposure pathway for the oysters, given the high Cd dietary AE.…”

“…For clams and scallops, trophic transfer is more important than uptake from the dissolved phase in the overall Cd and Zn accumulation because they have relatively high Cd and Zn AE and low uptake rate constant from the dissolved phase (Chong & Wang 2001, Pan & Wang 2008b. Assimilation of metals from phytoplankton by oysters is generally higher than in mussels and clams (Reinfelder et al 1997, Wang 2003.…”