DISTRIBUTION OF BENTHIC FORAMINIFERA IN THE SOUTHERN SALISH SEA, WASHINGTON STATE AND BRITISH COLUMBIA

This investigation is the first comprehensive study of benthic foraminifera in the Salish Sea, a small sea bordered to the east by British Columbia and Washington state and to the west by Vancouver Island and the Olympic Peninsula. The study was conducted in the southern Salish Sea, which includes Puget Sound and the area north to the Canadian border. Samples were collected by the Washington Department of Ecology as part of the Puget Sound Assessment and Monitoring Program, and span the time period from 1997 to the present. Ten sites, termed Temporal sites, were sampled annually and cover all parts of Puget Sound and north to Drayton Harbor near the Canadian border. Other sites were sampled on a rotating basis concentrating on one area (north, central, south) each year. For this study, 64 samples were investigated, including multiple years of temporal samples from Bellingham Bay (north Sound), Possession Sound (central Sound), and Commencement Bay (south Sound). Forty-nine species of benthic foraminifers were present, however, the assemblage was dominated by four species, Elphidium hannai, E. excavatum, Bucella frigidum, and Eggerella advena. Species richness was variable, ranging from one to 12 species per sample; foraminiferal density was likewise variable, ranging from one to over 6000 individuals per gram of dry sediment. Samples with the highest density occurred in the northern bays and in Possession Sound. No geographic or temporal trends were noted in species richness. Agglutinated species were most abundant in the northern part of the study area, virtually absent in the central part, and present in small numbers in southern Puget Sound. Multi-dimensional scaling and canonical correspondence analysis were carried out using the environmental parameters depth, sediment type, salinity and temperature. These indicate sediment type and depth are the most important factors controlling foraminiferal distribution. This does not, however, explain the strong dominance of agglutinate foraminifera and high densities in the north, and this requires further investigation.