Assessment of Toxic Hotspots in San Francisco Bay

Overview

Sediment Quality Objectives (SQOs) are based on a triad evaluation of sediment chemistry, benthos, and sediment toxicity. A fundamental challenge in SQO implementation has been the interpretation of the results of these assessments. This project will evaluate two previously identified hotspots within San Francisco Bay: Mission Creek (Central Basin) and San Leandro Bay. These regions are all located in areas with polyhaline benthic assemblages which allows for application of the current SQO guidance. The specific sites within these areas were selected based on consultation with the Water Board, RMP stakeholders, and the Benthic Workgroup. Three samples were collected along a gradient at each site.Results from these evaluations will be compared to the similar evaluations of the 27 RMP sites for which there are similar data.

Applicable RMP Management Questions

This study will aid in understanding the following EEWG benthic effects management questions:

• What are the spatial and temporal patterns of impacts of sediment contamination on benthic biota?

The proposed study will employ the SQO methods for Enclosed Bays and Estuaries to assess ecological condition, and if there is a potential concern of degraded conditions due to pollution. SQO assessment scores will be compared to the results of previous studies that examined the similar sites (to investigate temporal patterns) as well as the RMP Status and Trends scores from the ambient survey design.

• Are the toxicity tests, benthic community assessment approaches, and the overall SQO assessment framework we are using reliable indicators of impacts on benthic biota?

The SQO methods for Enclosed Bays and Estuaries will be implemented to investigate sediment conditions at sites that are the most impaired in the Estuary which will help to inform us on how sensitive these tools are and if they can detect changes in sediment conditions over time or after remediation efforts have been completed.

Surface sediment will be analyzed for the full suite of RMP Status and Trend measures:

• Sediment and water quality - grain-size, TOC, TN, and a CTD cast will be taken to record water quality conditions near the bottom.
• Trace metals
• Trace organics
• Toxicity to two test species (Eohaustorius estuarius and Mytilus galloprovincialis)
• Benthic macrofauna

Please contact. Ellen Willis-Norton with questions.