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.

Habitat attributes

Class ID: 
Class name: 
Marine, intertidal, boulder, partially exposed, eulittoral
3.0 km (in WA)
Primary substrate: 
Secondary substrate: 
Tertiary substrate: 
Substrate stability: 
Substrate key details: 
No sediment except sand scour at some sites
Wave exposure: 
Blue book classes: 
Marine intertidal rock: Partially exposed
Map/survey site examples: 
Tongue Point; West side San Juan and Lopez Islands
Fish sampling sites: 
Tidepool/Boulder: Twin Rivers
Diagnostic species: 
  • Mytilus californianus
  • Saccharina sessile
  • Phyllospadix
  • Katharina tunicata
  • Pisaster ochraceus
  • Anthopleura elegantissima
  • Balanidae
  • Lottia
  • Oligocottus maculosus
  • Anoplarchus purpurescens
  • Gobiesox maeandricus
VEC common associates: 
Species notes: