Presentation Title

Benthic foraminifera as indicators of environmental change at the sediment/water interface of Commencement Bay, Washington, U.S.A.

Session Title

Changes in Ecosystem Function and Climate Revealed by Long-term Monitoring in the Salish Sea

Conference Track

Climate Change and Ocean Acidification

Conference Name

Salish Sea Ecosystem Conference (2016 : Vancouver, B.C.)

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type of Presentation

Poster

Abstract

Commencement Bay, in the southern Salish Sea, is home to the city of Tacoma, Washington, and has been subjected to extensive anthropogenic impacts since the 1880s. This study used benthic foraminifera as biotic indicators to evaluate the effect of changes in environmental conditions at the sediment/water interface in the Bay. Sixty-nine grab samples collected in 1978, 1999, 2009 and 2014 were used, allowing assessment from before the start of environmental mitigation efforts to the present. Forty-six species of foraminifera were counted, 29 calcareous and 17 agglutinate. In all years of the study, three calcareous species, Buccella frigida, Cribroelphidium excavatum, and Elphidiella hannai dominated the assemblages, though in different proportions. Species richness differed significantly among years studied, dropping between 1978 and 2008, but rising again between 2008 and 2014. A similar trend was seen in the Shannon diversity index, though this was not statistically significant. Density and Equitability remained about the same in all study years. All indices reached their lowest points in 2008, which is consistent with water quality trends seen over the period 1999 to 2008. Throughout the study, only four barren samples were encountered: one in 1999 and three in 2008, contrasting dramatically with studies of Bellingham Bay and Sinclair and Dyes Inlets, where barren samples were common some years. The percent of partially dissolved calcareous specimens varied inversely with the indices, starting at 5% in 1978, reaching a high of 20% in 2008, then falling to 13% in 2014. These data suggest improving conditions in Commencement Bay.

Rights

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Language

English

Format

application/pdf

Type

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Benthic foraminifera as indicators of environmental change at the sediment/water interface of Commencement Bay, Washington, U.S.A.

Commencement Bay, in the southern Salish Sea, is home to the city of Tacoma, Washington, and has been subjected to extensive anthropogenic impacts since the 1880s. This study used benthic foraminifera as biotic indicators to evaluate the effect of changes in environmental conditions at the sediment/water interface in the Bay. Sixty-nine grab samples collected in 1978, 1999, 2009 and 2014 were used, allowing assessment from before the start of environmental mitigation efforts to the present. Forty-six species of foraminifera were counted, 29 calcareous and 17 agglutinate. In all years of the study, three calcareous species, Buccella frigida, Cribroelphidium excavatum, and Elphidiella hannai dominated the assemblages, though in different proportions. Species richness differed significantly among years studied, dropping between 1978 and 2008, but rising again between 2008 and 2014. A similar trend was seen in the Shannon diversity index, though this was not statistically significant. Density and Equitability remained about the same in all study years. All indices reached their lowest points in 2008, which is consistent with water quality trends seen over the period 1999 to 2008. Throughout the study, only four barren samples were encountered: one in 1999 and three in 2008, contrasting dramatically with studies of Bellingham Bay and Sinclair and Dyes Inlets, where barren samples were common some years. The percent of partially dissolved calcareous specimens varied inversely with the indices, starting at 5% in 1978, reaching a high of 20% in 2008, then falling to 13% in 2014. These data suggest improving conditions in Commencement Bay.