Influence of temperature on dietary metal uptake in Arctic and temperate mussels

Abstract

Assessments of the potential for metal and radionuclide contamination of arctic organisms have been based in part on experiments on organisms collected from temperate zones, even though adaptation to Arctic environments may enhance bioaccumulation of contaminants. Here, we compare the potential for blue mussels Mytilus edulis originating from the Arctic and from temperate zones to accumulate trace metals from filtered algal food at 2 temperatures. Geographic origin had little effect on either the percentage of metal assimilated from food (the assimilation efficiency, AE) or the rate at which ingested metal was excreted (measured by the efflux constant, k e ). By comparison, experimental temperature had much larger effects, causing AE for Ag, Am and Zn to be 122 to 945% higher, and k e for Cd and Co to be 50 to 80% lower at 2°C than at 12°C. The effect of temperature on the trophic accumulation factor (TAF = AE/k e ) was even more pronounced and systematic, with all metals characterized by larger TAFs at 2°C than at 12°C. The effects on the TAF were largest for the non-essential metals Ag and Am (6 to 7-fold), smallest for the required elements Co, Se and Zn (2 to 3-fold) and intermediate for Cd (4-fold). Geographic origin affected the TAF for Cd only, with temperate mussels displaying slightly higher potential for biomagnification. Our study suggests that, with the exception of Cd, mussels from temperate and Arctic zones accumulate metals from food similarly, and that temperature has a much larger impact on accumulation than population origin.

Effects of temperature on uptake of aqueous metals by blue mussels Mytilus edulis from Arctic and temperate waters

“…We compared the bioaccumulation of these metals from the aqueous phase by mussels obtained from Arctic and temperate waters at 2 temperatures that are near the extremes experienced in Arctic environments. The data we obtained on bioaccumulation of metal from solution complement similar data on the bioavailability of dietary metal to Arctic and temperate M. edulis (Baines et al 2005).…”

“…Molecular studies have shown that M. edulis is the only member of the genus from this area (Riginos et al 2002). Precautions were taken to ensure little stress to the mussels in transit (Baines et al 2005). Total transit time from northern Norway to New York was < 2 d and no mussel mortality occurred during transit.…”

“…Mussels were maintained for up to 3 wk in these chambers and their retention of the various radioisotopes monitored. The depuration chambers followed the design of Baines et al (2005), that was in turn a modification of a design used by Wang et al (1995). Basically, the system consisted of a series of chambers that contained the mussels and kept them separated from their feces to minimize recycling of dissolved label via the particulate pathway.…”

“…Prior to exposure of mussels to dissolved metals, the filtration rates of each individual were measured according the methods of Baines et al (2005). Basically, the maximal rate at which mussels removed the diatom Thalassiosira pseudonana from 200 ml volumes of water was measured by tracking changes in either in vivo fluorescence (measured using a Turner designs Model 10AU fluorometer, Turner Designs), or cell number (measured with a Multisizer II Coulter Counter system).…”

“…It is analogous to the trophic accumulation factor, TAF, (equivalent to the CF f of Fisher & Reinfelder 1995) used by Baines et al (2005) to estimate efficiency of metal accumulation from food. The relative standard errors of the CF w s were calculated by adding the relative variances of the estimated parameters used in the calculation and taking the square root.…”