Heavy metal accumulation by barnacles and its implications for their use as biological monitors

Abstract

As part of an investigation into the suitability of barnacles as biological monitors, the effect of metal exposure and a number of intrinsic and extrinsic factors on Cd, Cu, Pb and Zn levels in Semibalanus balanoides bodies was examined, with limited comparative studies on Balanus crenatus. No regulation was apparent over exposure periods of up to 100 days at added concentrations of 5–60, 20–90, 50–200 and 20–80 μg litre −1 of Cd, Cu, Zn and Pb respectively. Accumulation rates of metals in bodies and egg masses were proportional to added metal concentrations although rates in egg masses increased with brood time. A single collection at 50 days post-exposure gave a similar indication of ambient metal levels and would be preferable for a routine monitoring programme. Metal levels were negatively correlated with body weight, necessitating weight-normalization of data. Decreases in body metal levels following transfer to an uncontaminated environment were due to dilution by body weight increase rather than excretion. Cadmium accumulation was most influenced by salinity and some other metals (Cu increased uptake although Zn had no effect). These experiments suggest that barnacles may be suitable monitors of Cu, Zn and possibly Pb. Intermetallic effects argue against their use to assess Cd contamination.