Marine, intertidal, boulder, protected, eulittoral

Many areas in the northern Puget Trough receive neither oceanic swell nor extensive wind fetch, but retain their rocky character due to steepness of the shore or currents that sweep away most sediment. Examples are the inside waters of the San Juan Islands, where there is not enough freshwater input for sites to be categorized as Estuarine. Siltation, desiccation, and temperature stresses all take their toll on rocky-shore organisms in these areas. 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, protected, eulittoral
8.0 km (in WA)
Primary substrate: 
Secondary substrate: 
Tertiary substrate: 
Substrate stability: 
Substrate key details: 
No sediment except surface siltation
Wave exposure: 
Protected, Very protected
Blue book classes: 
Marine intertidal rock: Semi-protected and protected
Map/survey site examples: 
Sites in inner San Juan Islands
Fish sampling sites: 

Diagnostic species: 
  • Fucus distichus
  • Mastocarpus papillatus
  • Nucella lamellosa
  • Littorina
  • Balanidae
  • Anoplarchus purpurescens
  • Gobiesox maeandricus
  • Oligocottus maculosus
  • Xiphister atropurpureus
Species notes: