Clearer water allows more sunlight to penetrate, which aids in the growth of crucial seagrasses. Shellfish benefit seagrasses in another way; as shellfish digest the nutrients they filter from the water, a portion of those nutrients, including nitrogen, is expelled directly into the sediment, making it immediately available to seagrasses — essentially fertilizing it.
Besides promoting seagrass, including eelgrass, shellfish farming also helps support a diverse population of other marine species — both flora and fauna. For example, ground-cultured oysters and shell placed in the intertidal portion of West Coast estuaries has been shown to provide equal or better habitat than eelgrass for juvenile Dungeness crab (Eggleston and Armstrong 1995; Feldman et al. 2000). Shellfish themselves create three-dimensional structures that other marine species — including juvenile salmon — can use for forage and protection from predators.
In addition to the shellfish themselves, many components of the gear used in shellfish farming provide additional habitat. For example, a 2004 study led by Dr. Joseph DeAlteris found higher populations and a richer diversity of tideland species in and around shellfish beds than in seabed habitat with seagrass or bare seabed.
The lines used in culturing mussels support a rich variety of over 100 invertebrate species, as well as shiner perch and juvenile Pacific herring which are seasonally concentrated in this habitat.
Shellfish farms also provide critical foraging habitat for a large variety of waterbirds. For example, in a 2005 study of Humboldt Bay, Drs. Connolly and Colwell found more species of shorebirds and wading birds concentrated in tidelands with shellfish farms than those without.
Watch below to see how oysters and other shellfish can benefit tidal habitat: