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(334) The sea-urchin embryogenesis bioassay for monitoring marine pollution; conclusions of four years pilot trials in the Galician coast. Beiras, Ricardo1, Bellas, Juan1, Fernández, Nuria1, Mariño-Balsa, José Carlos1, Vázquez, Elsa1, 1 ABSTRACT- During the past four years the embryogenesis of the Paracentrotus lividus sea-urchin has been used at experimental scale as a rapid and sensitive biological response for the assessment of both sediment and seawater quality in the Galician coast (NW Spain). For sediment quality evaluation, bioassays were conducted with elutriates obtained by agitation of 200 g sediment in 1 l control seawater. Elutriate dilution or agitation of equivalent weights of sediment in control water provided similar results. Magnetic stirring, orbital shaking and centrifugation were all acceptable, provided the water phase was aerated to avoid false positives caused by H2S. Annual sampling consistently identified the same toxic sites the four years. For seawater quality evaluation two methods were developed. The first one involves in situ rearing of the fertilised eggs within cages installed by divers. This methodology was used two years on sites at outer and inner part of a Galician Bay and in both cases identified pollution in the inner station (details in Beiras et al. Estuarine Coast. Shelf Sci., 2000). The second method consists of laboratory assaying of the seawater samples. In a preliminary trial samples were taken both near the surface and the bottom from two sites in the inner part of the same Bay once per week from 23/5 to 28/6/2000. The main methodological problem was the salinity of the surface samples. A minimum of 30 ppt is required for the development of the sea-urchin larvae. The results showed, as expected, high spatial and temporal variability, but an overall trend towards higher toxicity on one of the sites. In conclusion, sediment toxicity assessment provide more consistent results, but we have proved that the sea-urchin embryogenesis bioassay has enough sensitivity to reveal pollution events straight in the seawater, requiring a minimum of manipulation of the samples. Key words: seawater quality, monitoring, embryotoxicity, sea-urchin |
