Foraminiferal Trends within Inner Sublittoral Zone off Coast of Washington: ABSTRACT

Abstract

Foraminiferal and diatom distributional trends within the inner sublittoral zone have been studied along 170 km of the coast of Washington from Grays Harbor to Cape Flattery. The samples are from water depths of 7-59 m. Trends in the concentration of foraminiferal tests and diatom frustules in bottom sediments appear to be closely related to wave-induced turbulence at the sediment surface. Concentrations of tests markedly increase seaward at 20-m water depth, apparently the deepest limit of intense turbulence. Frustules, because of their very slow settling velocity, are prevented from settling at depths less than about 50 m except in certain microenvironments. These trends are not correlated with trends in sediment grain size, a fact which suggests that little modern sediment is accumulating in this area. One trend is related to increasing depth and distance from shore; Elphidium spp. decrease markedly seaward of 30 m as Eggerella advena increases. Comparison with other studies in nearby areas indicates that this trend is heterobathyal. Off Oregon it occurs at about 100 m and off Washington south of Grays Harbor, if the Elphidium fauna is present at all, it occurs at depths less than 20 m. Other foraminiferal trends are related primarily to substrate. Rocky substrates near the coastline have a characteristic Cibicides lobatulus-Glabratella ornatissima fauna. Relict coarse sand substrates offshore have faunas with abundant Trochammina charlottensis, Cribrostomoides jeffreysii, and Elphidiella hannai. End_of_Article - Last_Page 716------------