Marine Intertidal Rock: Exposed (Eulittoral)

Bedrock habitats exposed to the full range of wave energies are found on the outer coast and in the western Strait of Juan de Fuca.  Rock types range from soft sandstones to conglomerates to hard metamorphic and igneous types. Little is known of how community type varies with rock type.  Communities of ex- posed rocky coasts are dominated by toughly constructed sessile plants and animals, and are usually distinctly zoned from the upper rocks reached by spray to the lowest levels.  Low zones are usually algal- dominated and thus portions of this habitat could be mapped as “Aquatic Bed” under the NWI system. Productivity and biomass are high in these habitats.  The three-dimensional aspect provided by the large algae and invertebrates contribute to the great spatial complexity and species diversity.

Diagnostic Species

The California mussel Mytilus californianus, the sea palm Postelsia palmaeformis (most exposed areas only, and with patchy distribution), the gooseneck barnacle Pollicipes polymerus (= Mitella polymerus), and (in low zones) kelps in the genera Laminaria and Lessoniopsis.

Common Associates

Several hundred species of macroscopic plants and animals may inhabit this diverse and productive community.  Common plants seen most often on exposed coasts include (from high to low zones): the brown rockweed Pelvetiopsis limitata, diverse red algae including Iridaea cornucopiae (very high), Iridaea splendens, Dilsea californica, Ptilota and Neoptilota spp., encrusting and articulated coralline algae; the kelps Hedophyllum sessile and Egregia menziesii, and the surfgrass Phyllospadix scouleri. Common animals include the urchin Strongylocentrotus purpuratus (low), the limpets Lottia pelta, L. strigatella, Acmaea mitra and Tectura scutum, the chitons Katharina tunicata and Mopalia spp., four species of barnacles including the very large Balanus nubilus (very low), the ochre star Pisaster ochraceus and the six-rayed star Leptasterias hexactis, the nestling crab Oedignathus inermis, various compound ascidians and hydroids, the violet sponge Haliclona permollis and the crumb-of-bread sponge Halichondria panicea.  Characteristic tidepool species include the green anemone Anthopleura xanthogrammica, and many fish.

Sites undisturbed by humans are used as feeding territories by black oystercatchers, and haulout and pupping sites by harbor seals and northern sea lions.  Sea otters, mink, weasels, raccoon, and deer all forage occasionally in the rocky intertidal zone, as do gulls, crows, bald eagles, surfbirds, ruddy and black turnstones, rock sandpipers, and other shorebirds.  At high tide, various subtidal fishes may forage in these habitats, including sea perch, sculpins, various rockfish, and cod, although there has been little investigation of this topic.  Pools are occupied by various small fish:  high cockscomb, sculpins (tidepool, calico, mosshead), northern clingfish, and black prickleback.  Areas offshore of rocky sites are used by cormorants, scoters, harlequin ducks, and buffleheads.

Surveyed Sites

Pillar Point, Waadah Island, Tatoosh Island, Portage Head, five sites in Olympic National Park.


Dethier, 1984, 1988; Paine, 1980; Dayton, 1971 and 1975; Cross et al., 1978; Nyblade, 1979b; Rigg and Miller, 1949.