Benthic invertebrates, or benthos, are the worms, clams, snails, crabs, and other animals that live in and on the sediment at the bottom of Puget Sound. These animals are ecologically, economically, and culturally important. They play a vital role in the Puget Sound food web, being eaten by larger predatory animals in the sediment, by fish including salmon, and people in the case of many mollusks, crabs, and more.

The benthic community is influenced by many factors including depth, physical characteristics of the sediment (e.g., how much sand or silt), predation, the presence of harmful chemicals, and more. We collect benthos samples to help us better understand what is happening to this crucial part of the food web and what it can tell us about the health of that habitat.

Benthos samples provide us with information on what species and how many of them are present in a standard-sized area. This information, paired with sediment chemistry samples and information about the physical environment these animals are exposed to, can help us understand what factors influence these communities.

This SAP focuses on the benthos monitoring component of the Routine Marine Sediment Monitoring Program. Subtidal and intertidal sediment chemistry sampling will be addressed in separate SAPs.