DISTRIBUTION OF FORAMINIFERA IN PUGET SOUND, WESTERN WASHINGTON, U.S.A.

Abstract

Puget Sound, the southern portion of the Salish Sea, has been intensely studied for its macrofauna, but lacks a comprehensive study of its benthic foraminifera. The Sound is a fjord-like lowland consisting of numerous smaller estuaries. Much of it has been heavily impacted by anthropogenic activities, and two locations have been designated as federal Superfund sites. The purpose of this investigation was to survey the benthic foraminifera present in Puget Sound and relate their distribution to environmental parameters. The 64 grab samples used were provided by the Washington Department of Ecology through their annual Puget Sound Ambient Monitoring Program and span the years 1997–2010. The investigation recorded 46 species of benthic foraminifera, with four species dominating the assemblages: Eggerella advena (Cushman), Elphidiella hannai (Cushman and Grant), Elphidium excavatum (Terquem), and Bucella frigida (Cushman). Agglutinated taxa were dominant in the northern Sound and parts of the southern Sound, but nearly absent in samples from the central Sound. Density and diversity indices were extremely variable throughout the Sound, even in samples taken from the same site over a number of years. Canonical correspondence analysis indicated that no single environmental parameter analyzed was responsible for the distribution of foraminifera. Cluster analysis yielded four main groups dominated by the four taxa listed above. These clusters were heterogeneous in their distribution, with samples from the same sample site grouped in different clusters in different years. The extreme heterogeneity of the results indicates the need for a series of smaller-scale investigations focusing on individual embayments to better understand the foraminiferal distributions and to develop a foraminiferal monitoring tool unique to Puget Sound.