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Description
The bioaccumulation of the heavy metals copper (Cu) and zinc (Zn) by the giant kelp, Macrocystis pyrifera, and the purple urchin, Strongylocentrotus purpuratus, were assessed in the laboratory by exposing them to elevated metal concentrations in seawater. Experiments were designed to contrast the uptake of Cu and Zn in isolation (when only one metal concentration was elevated) and in combination (when both metal concentrations were elevated) after three days of exposure in the meristematic tissue of M. pyrifera and for both the gonad and digestive tissues of S. purpuratus. Experimental concentrations for Cu ranged from 15ppb (parts per billion) to 480ppb and Zn ranged from 100ppb to 600ppb. Following metal exposure, samples were acid digested and analyzed on an inductively coupled plasma atomic emissions spectroscopy (ICP-AES). Results indicated that M. pyrifera accumulated Cu when it was elevated in seawater regardless of Zn concentrations. In contrast, M. pyrifera only accumulated Zn from elevated concentrations in seawater when Cu concentrations were not elevated. This pattern, although not always statically significant, was observed in all experiments, suggesting that Cu inhibits the uptake of Zn, but not vice versa. Results also showed that S. purpuratus was unable to accumulate these metals directly from elevated seawater. Only one treatment showed Zn accumulation in the digestive tissues directly from seawater when both metals were elevated (30ppb Cu + 100ppb Zn). In addition, S. purpuratus did not accumulate either Cu or Zn through the consumption of Cu and Zn contaminated M. pyrifera tissues. This study suggests that M. pyrifera may be useful as a bio-indicator species for monitoring heavy metal pollution in coastal environments. Whereas the adult stages of S. purpuratus do not accumulate metals when exposed to concentrations that would be expected following rain events over a period of a few days.
