Foraminiferal evidence of sediment toxicity in anthropogenically influenced embayments of Puget Sound, Washington, U.S.A.

• Foraminiferal assemblages from anthropogenically impacted inlets showed deterioriation from 1974 to 2008, despite remediation efforts.
• No single pollutant stands out as a “culprit”.
• Partial dissolution of calcareous tests and impoverished foraminiferal assemblages in 2008 suggest low pH was a major factor in the sediments.

Environmental monitoring in estuarine settings depends on sediment quality guidelines and standards (SQG and SQSs) developed using scientific investigation and analysis. The purpose of this study was to utilize benthic foraminifera as a proxy for assessing the health of two severely impacted embayments within the complex fjordal system of Puget Sound (Washington, United States of America) and testing the efficacy of the standards used in monitoring the Sound. The embayments, Sinclair and Dyes inlets, have been subjected to contamination by military, industrial, residential and agricultural effluents for over 100 years, resulting in some of the most toxic marine sediments in Puget Sound. Although the results of chemical tests were within acceptable limits of the State monitored SQSs, toxicity and biotic assessments were not. The present study found that benthic foraminiferal assemblages were notably of low species diversity and strongly dominated by species tolerant of various contaminants and dysoxia. Foraminiferal density and diversity deteriorated between 1974 and 2008, with Sinclair Inlet showing a near collapse of foraminiferal assemblages by 2008. A similar trend was seen in the benthic macroinvertebrates studied by the Washington State Department of Ecology. In addition, large numbers of calcareous foraminiferal tests showed signs of dissolution, particularly in Sinclair Inlet; these numbers increased in later sampling years, as did the number of samples that were barren of foraminifera. This suggests a need for re-examination of the metrics used to set environmental standards and the need for better understanding of the compounding effects of contaminants on the biota.