DISSOLUTION OF BENTHIC FORAMINIFERA TESTS TRACKS ACIDIFICATION IN ANTHROPOGENICALLY IMPACTED EMBAYMENTS OF PUGET SOUND, WA (SOUTHERN SALISH SEA)

Here we report initial results using benthic foraminifera as a proxy for low pH in Puget Sound sediments over a temporal range from 1974 to the present. Puget Sound is the southern extent of the 100 km long fjordal system called the Salish Sea (Washington State and British Columbia).

The study utilized over 200 samples collected by the State Department of Ecology from four industrialized embayments containing numerous Superfund sites: Bellingham Bay, Sinclair/Dyes Inlets, Commencement Bay, and Elliott Bay. An extensive database of physical sediment parameters accompanied the samples, but did not include pH or bottom water DO levels. Investigations into foraminiferal assemblages in these embayments demonstrated that partial dissolution of foraminiferal tests is widespread and pervasive. For this investigation, foraminifera showing dissolution were categorized into three bins based on the degree of dissolution: 1 = mild/moderate, 2 = acute, 3 = severe. Results indicate that all embayments show partial dissolution of foraminiferal tests, but it is most pronounced in Bellingham Bay and Sinclair/Dyes inlets. Some samples in these bays have 100% of calcareous individuals showing dissolution. In other samples, calcareous taxa disappeared and were replaced in the assemblages by agglutinate species. Dissolution effects have been observed in eight taxa, however, Elphidiella hannai is most heavily impacted, suggesting that species is more susceptible to dissolution than others. Results to date lead us to conclude that pH in Puget Sound sediments is in many places too low for foraminifera to mineralize successfully, or is dissolving empty tests within the sediments; thus these organisms are tracking acidification in the area. Whether the cause is general ocean acidification or due to local conditions is yet to be determined.