Inhibition of embryo development of the commercial bivalves Ruditapes decussatus and Mytilus galloprovincialis by trace metals; implications for the implementation of seawater quality criteria

R. Beiras, M. Albentosa-2004
Aquaculture, 230(1-4): 205-213

Abstract:

This study evaluates the risk posed by trace metals on the culture of bivalves in the Galician coast (NW Iberian Peninsula), which depends on collection of natural seed and larval rearing with natural seawater in hatcheries. With this aim, toxicity tests were carried out with embryos of the commercial bivalves Ruditapes decussatus and Mytilus galloprovincialis, and the toxicity of Hg, Cu, Zn, Cd and Pb was quantified in terms of median effective concentration (EC₅₀) and toxicity threshold, using embryogenesis success as endpoint. The EC₅₀ values ranged from 4 to 10 µg/l for Hg and Cu, from 100 to 300 µg/l for Zn and Pb, and from 400 to 2000 µg/l for Cd. The toxicity of copper and zinc combinations could be predicted using a strictly additive model. Effective concentrations found were compared to measured metal concentrations in the Galician Rias, and to local and international seawater quality criteria, in an attempt to evaluate the risk posed by metals to these commercial species. Zinc and especially copper pollution were found to represent a serious threat in certain areas. Furthermore, local seawater quality criteria recently implemented are, in the case of copper and zinc, two orders of magnitude too high to offer any protection for these sensitive early life stages of bivalves.

(Instituto Español de Oceanografía, Centro Oceanográfico de A Coruña, Muelle de Ánimas s/n, E-15001 A, Coruña, Galicia, Spain, e-mail of M. Albentosa: marina.albentosa@co.ieo.es)

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