Technical foundation established for protecting sediment-dwellers in estuaries from organic matter

SCCWRP has developed a technical foundation for protecting sediment-dwelling organisms in California estuaries from the harmful effects of exposure to excess organic matter.

The technical work product, described in an article published in September by the journal Ecological Indicators, consists of a set of nitrogen thresholds for estuary sediments that is intended to clarify for managers when the estuary’s sediment-dwelling invertebrate communities are likely to be adversely affected by excessive levels of organic matter. Sediment organic matter accumulation, a consequence of eutrophication, occurs primarily as a result of overproduction of algae, which eventually degrades and settles on the seafloor.

Measuring nitrogen levels is a way to estimate the amount of degraded organic matter in sediment. Excess levels of this organic matter can be toxic to aquatic life.

Already, California’s coastal Regional Water Quality Control Boards have begun using the sediment nitrogen thresholds to guide development of TMDLs (total maximum daily loads) for nitrogen.

Managers also have used the thresholds to identify locations where high levels of degraded organic matter already exist, so that these areas can be targeted for cleanup.