Marine, intertidal, boulder, partially exposed, eulittoral

Sites not directly exposed to oceanic swell but with substantial wave action are found throughout the Strait of Juan de Fuca, and on the west and south sides of the San Juan Islands and Whidbey Island. Wave energies are less but there is a consequent increase in desiccation stress (and perhaps other stresses) leading to somewhat lower diversities than at the most exposed sites. In Washington, low tides on the more inland waters also fall at highly stressful hours (nearer midday in the summer and midnight in the winter), contributing to lower diversities. Communities on tops and sides of boulders are similar to those on bedrock, but the spaces on the lower edges and beneath boulders provide additional spatial complexity; these microhabitats tend to be shadier (and thus cooler) and less exposed to wave disturbance. Boulder habitats thus often have very high species diversity.