Benthic Sediments

The Sanitation Districts benthic sediments monitoring consists of sediment chemistry and biological community (infaunal) assessments. The resulting biological, physical, and chemical data are used for assessment of trends in sediment contamination and to draw inferences regarding the relationship between effluent-derived alteration of the benthic habitat and patterns in infaunal community structure. The results of these monitoring efforts can be found in the Sediment Condition and Benthic Infauna chapters, respectively, of the JWPCP Biennial Receiving Water Monitoring Report.

1. Sediment Chemistry:

Samples for sediment chemistry analyses are collected from a 44-station fixed sampling grid which extends from Point Fermin to the Redondo Submarine Canyon, and targets four depths (30, 61, 152, and 305 m) along 11 transects. Analysis of sediment grain size, sediment pore-water sulfide concentration, total organic carbon, and organic nitrogen levels are conducted at all sites annually. Sediments are further analyzed for nine metals, DDTs, and PCBs at a subset of 24 stations annually and at all 44 stations every five years as required in the permit.

Benthic Sediment Monitoring Stations

2. Biological Community (Infauna):

Infauna samples are collected annually from the same 44-station fixed sampling grid used for sediment chemistry sampling. Infauna sampling consists of screening the sediments through a 1 mm mesh screen to collect these organisms, as well as debris and large grained sediments. These materials are preserved in the field for later analyses in the lab. Lab analysis begins by separating the infauna from the debris and sediments. The infauna are then identified, counted, and used to assess the health of the biological community living within these sediments.

Benthic Infauna Sampling Station Map