Marina del Rey stressor identification rules out possible causes of degraded sediment quality

SCCWRP and its partners have ruled out some potential causes of degraded sediment quality in Marina del Rey Harbor, part of an ongoing stressor identification study aimed at understanding why bottom-dwelling marine communities are being adversely impacted by the sediment.

During two rounds of tests on sediment that was sampled in January and July, researchers examined whether a number of toxic chemicals – including trace metals, PAHs and chlorinated hydrocarbons – could be responsible for degraded sediment quality in Marina del Rey Harbor. The Los Angeles County boat harbor has a TMDL (total maximum daily load) for these toxics.

In October, researchers completed sediment Toxicity Identification and Evaluation (TIE) testing; none of the toxics listed in the TMDL were associated with the sediment toxicity that was detected during the lab tests. In other words, researchers were able to rule out a number of chemicals that are not responsible for degraded sediment quality, but still don’t know which factors are responsible.

Researchers theorize that other types of toxic chemicals could be responsible for the degraded sediment quality, or that high concentrations of fine-grained sediment in the harbor may be interfering with the lab testing method.

SCCWRP and its partners are conducting additional stressor identification analyses to understand the magnitude and cause of the sediment impacts to resident bottom-dwelling organisms in Marina del Rey Harbor. A full study report is expected to be released by the end of this year.