(PW295) Modifications to the sediment bivalve larval development test to reduce testing artifacts associated with suspended particulates.
Elphick, J1, Bailey, H2, Bergmann, K1, Liebl, M1, 1 AMEC Earth and Environmental, Fife, WA, USA2 AMEC Earth and Environmental, San Diego, CA, USA
ABSTRACT- Previous studies have demonstrated that sediment toxicity tests conducted with larvae of oysters and mussels can exhibit adverse effects caused by settling suspended particulate material. This testing artifact can result in incorrect conclusions regarding the toxicological risks associated with sediment samples. Changes to the test method designed to reduce this effect, such as extending the settling time from 4 to 24 hours prior to addition of larvae, and enclosing the larvae within Nitex-screened containers, have been used in the past to limit the effect of suspended particulates, with some success. This study evaluated methods analogous to those typically employed in tests with amphipods and polychaetes as an alternative to the study design currently used for sediment tests that evaluate bivalve larval development. Modifications to the method included: an increase in the amount of sediment added to the test containers from 20 to 200 g/L, an increase in the settling time from 4 to 24 hours prior to addition of the larvae, and aeration of the test chambers during the settling period. These modifications reduce the particulates present in the water column at test initiation and, therefore, reduce the potential for adverse effects associated with suspended particulates. Moreover, the proposed modifications to the method also provide a more appropriate and consistent evaluation of sediment toxicity by using methods which are analogous to those used for other species, as well as provide sufficient sediment in the test container such that a redox gradient can be established in the sediment during exposure.
Key words: bivalve larval development, suspended sediment, Mytilus galloprovincialis