Oyster embryo-larval bioassay (revised)

The description of the oyster (Crassostrea gigas) embryo bioassay was initially published in the ICES TIMES series in 1991 (No.11). At the time, the bioassay was used in the United Kingdom for measuring water quality in relation to coastal waters which received anthropogenic discharges. Subsequently it was applied to measure general water quality and was taken up by the OSPAR Joint Assessment Monitoring Plan (JAMP) as a technique for measuring general biological effects in water, sediment elutriates, and pore water, and is used in several countries across the OSPAR Maritime Area.

The organism response used in the bioassay is the ability of early stage embryos to develop normally and reach the “D-shaped” larval stage (at which the paired hinged shells can be seen) within 24 hours. Although the exposure time is short, it encompasses a period of intense cellular activity during which the impairment of a number of critical physiological and biochemical processes may result in poor and abnormal growth and development.

The method described here is a complete revision of the original text, and includes a more comprehensive description of the methodology, how it can be applied for testing water quality for monitoring purposes, and for direct toxicity assessment or where a dilution series may need testing (e.g. extracts from passive samplers / sediment elutriates etc). Furthermore, there is additional information on the treatment and work up of results and analytical quality control.