Anthopleura elegantissima/sola
Chthamalus spp./Balanus glandula
Mytilus californianus Conrad, 1837
California sea mussel
General Description (from Morris et al. 1980):
Black and bluish color, often eroded white valves, darker at margins; radial ribbing but also concentric growth lines present; shell to about 130 mm long
Habitat and Range (from Morris et al. 1980):
Abundant, on surf-exposed rocks and pier pilings; mainly in upper-middle intertidal zone on outer coast; subtidal and offshore to 24 m (depth); Aleutian Is., Alaska to southern Baja California
Biology:
The California sea mussel forms extensive beds, which may be multi-layered (usually in the north). These beds create habitat for many species of invertebrates and algae (Paine 1966; MacGinitie & MacGinitie 1968; Suchanek 1979; Kanter 1980). Mussels are attached to hard substrate by secreting byssal threads at the base of the foot (Morris et al. 1980). Mussel beds are damaged by large swells, and are more susceptible to damage after heavy predation by sea stars (Morris et al. 1980). Beds that are already patchy or thinned by human disturbance (fishers who use mussels as bait) can also be susceptible to wave damage. An area completely cleared of mussels may take from 1 to 10 years to reestablish the diverse community (Morris et al. 1980; Vesco and Gillard 1980). Mussels have been found to be adversely affected by oil spills (Chan 1973; Foster et al. 1971). Mytilus galloprovincialis/trosullus, the bay mussel, can be interspersed with M. californianus, but generally occurs in calmer waters because of its weaker byssal threads (Morris et al. 1980). In California, sea mussels are quarantined from late spring to early autumn because the toxin from a dinoflagellate accumulates in the mussel tissue (Kozloff 1983). This toxin can cause paralysis and death.
Southern CA Mytilus beds
Can be confused with:
M. galloprovincialis/trosullus, which are more common in sheltered habitats; have smooth valves, lacking radiating ridges, with strong elbow-curve at umbo; less eroded than M. californianus
Mytilus galloprovincialis/trosullus (top) and Mytilus californianus (bottom)
References:
Chan GL (1973) A study of the effects of the San Francisco oil spill on marine organisms. In Proceedings of joint conference on prevention and control of oil spills. American Petroleum Institute, Washington, D.C., pp 741-782
Foster MM, Neushul M, Zingmark R (1971) The Santa Barbara oil spill. Part 2. Initial effects on intertidal and kelp bed organisms. Environ Pollut 2:115-134
Morris RH, Abbott DL, Haderlie EC (1980). Intertidal invertebrates of California. Stanford University Press, Stanford
Kanter RG (1980) Biogeographic patterns in mussel community distribution from the southern California Bight. In D.M. Power (ed) The California Islands: proceedings of a multidisciplinary symposium. Santa Barbara Museum of Natural History, Santa Barbara, California, pp 341-355
Kendall A, Kusic K, Maloney E, Williams M (2002) List of species to be discussed at the 2002 MMS Taxonomic Workshop
Kozloff EN (1983) Seashore life of the northern Pacific coast. University of Washington Press, Seattle
MacGinitie GE and MacGinitie N (1968) Natural history of marine animals. McGraw Hill, New York
Paine RT (1966) Food web complexity and species diversity. Amer Nat 100:65-75
Suchanek TH (1979) The Mytilus californianus community: studies on composition, structure, organization, and dynamics of a mussel bed. Ph.D. Thesis, University of Washington, Seattle, Washington
Vesco LL and Gillard R (1980) Recovery of benthic marine populations along the Pacific Coast of the United States following man-made and natural disturbances including pertinent life history information. U.S. Department of the Interior, Bureau of Land Management Service, POCS Reference Paper No. 53-4.