Estuarine Intertidal Mud: Partly Enclosed and Enclosed

This substratum type differs from the mixed-fines in lacking gravel or a significant amount of sand and consequently is softer and oozier. It is found in the heads of bays and inlets. Eelgrass and its associated invertebrate, fish, and bird fauna are less common in these habitats, as are hard shelled clams.

Diagnostic Species

Macoma nasuta, Macoma balthica.

Common Associates

The clams Mya arenaria and Cryptomya californica; the crustaceans Upogebia and Callianassa, the amphipod Corophium salmonis, the polychaetes Polydora kempi japonica, Pygospio elegans, Capitella capitata (especially in polluted areas), Hobsonia florida, Manayunkia aestuarina, and Glycinde picta; the sea slug Melanochlamys diomedea.  Zostera marina and Z. japonica occur in some areas.

Sites Surveyed

Dockton (Vashon Island), Fidalgo Bay, Fraser River Estuary, Anderson Cove (Hood Canal), portions of Grays Harbor.


Thom et al., 1984; Nyblade, 1979a; Smith and Webber, 1978; Levings et al., 1983; Chew, 1970; Thom, 1981; Albright and Borithilette, 1982.