The intertidal and shallow subtidal benthos of the Strait of Juan de Fuca: spring 1976-winter 1977

With the potential existing for large scale oil shipment through the Strait of Juan de Fuca? a baseline study was initiated to document the distribution, abundance and seasonal variation of the intertidal and shallow subtidal benthos along the Washington coast of the Strait of Juan de Fuca. Ten study sites, representative of the range of habitats present, were selected and sampled quarterly at high, mid, and low intertidal strata. Once a year sampling was conducted at intermediate intertidal tidal heights and at -5m and -10m relative to MLLW. Over 900 different plants and animal species were collected during the study year. Dominant groups were algae, molluscs, polychaete annelids, and crustaceans. In the intertidal, rock habitats were the richest in terms of number of species, density, and biomass, followed by cobble, fine sediment, sand, and gravel habitats. Strong vertical zonation was found at all but the most exposed gravel and sand sites. Subtidal study sites were consistently rich. Community comparisons of the areas and levels sampled during this study validated the type habitat approach and the selection of strata to be sampled. Patchiness of organisms in the communities sampled generally obscured seasonal patterns in populations of component species. However, summed over all levels and areas, summer is most often the peak for species richness, abundance, and biomass and winter most often the low.