Indirect effects act on organisms that do not reside permanently within sediments, but are exposed to sediment contaminants through the food chain. Key receptor organisms are marine birds, fish, and humans.
The goal of this research program is to develop measurement tools and an assessment framework to evaluate the indirect effects of sediment contaminants on humans and wildlife.
Development of the conceptual basis for the assessment framework and data compilation is in progress.
The assessment of indirect effects due to sediment contamination is more complex and requires a different conceptual approach than that used to assess direct effects. The potential for indirect effects on an organism is influenced by several factors, including: the portion of the sediment contaminants that is biologically available to prey species, the complexity of the food web, movements of the receptor organisms, food comsumption rate, and species specific variations in chemical sensitivy.
SCCWRP researchers are developing a multiple lines of evidence (MLOE) approach (similar to that shown here) to evaluate the potential for indirect effects from contaminated sediments. The lines of evidence are expected to include: sediment contaminant concentration, bioavailability of sediment contaminants, and prey tissue contaminant concentration. Separate assessment frameworks will need to be developed for each receptor group (e.g., birds and humans) because of differences in feeding rate, time spent in the waterbody of interest, and the type of prey species eaten.
The initial focus of this research is to develop an assessment framework for PCBs and chlorinated pesticides, chemicals that are widespread in California bays and estuaries, and are bioconcentrated many fold in species at the top of the food web. Fish tissue and sediment chemistry data have been compiled for several water bodies and will be used to investigate the performance of the assessment approach.
For more information on this topic, please contact Steve Bay at steveb@sccwrp.org
