2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 52-1
Presentation Time: 9:00 AM


MARTIN, Ruth A., Burke Museum, University of Washington, Box 353010, Seattle, WA 98195-3010, NESBITT, Elizabeth A., Burke Museum, University of Washington, Box 353010, Seattle, WA 89195-3010, COBERLY, Jerilyn, Department of Earth and Space Sciences, University of Washington, P.O. Box 351310, Seattle, WA 98195 and ZHANG, Bijia, Department of Earth and Space Sciences, University of Washington, P.O. Box 353010, Seattle, WA 98195

Sinclair and Dyes Inlets surround the city of Bremerton, Washington, and contain some of the most contaminated sediments in Puget Sound. The city is home to the Puget Sound Naval Shipyard, a designated U.S. federal Superfund site; sediments there are contaminated with PCBs, PAHs and toxic metals. Ostrich Bay, an embayment off Dyes Inlet, was the site of a Naval Ordnance facility where munitions were manufactured and destroyed, with by-products washed and dumped into the bay. In addition to industrial pollutants, agricultural and recreational uses of the surrounding land introduce their own contaminants, particularly fecal coliform, phosphorus and metals. This study utilized foraminifera to assess the condition of the benthic ecosystem. Foraminiferal assemblages from forty-two sediment samples were analyzed and correlated with data on sediment quality and chemistry. Of those samples, 20% were barren of foraminifera, and in the rest, species richness was low, averaging fewer than four species per sample in both inlets. The Shannon diversity index averaged 0.98 in Dyes Inlet and 1.07 in Sinclair Inlet. Many samples contained large percentages of calcareous foraminifera that showed signs of dissolution. Samples that were barren of foraminifera and those that showed pronounced dissolution displayed high levels of Total Organic Carbon (TOC); the decomposition of organic material may have resulted in anoxic conditions and low pH. The former may explain the lack of foraminifera in samples, and the latter may be responsible for the dissolution of foraminiferal tests. Comparison of foraminiferal diversity and toxic metal concentrations demonstrated a negative correlation between the two. Several samples in both inlets contain numerous euhedral crystals of gypsum. These samples displayed high TOC and were either barren of foraminifera or showed very low diversity. Analysis of sulfur isotopes indicate the gypsum is the result of sulfate reduction, either from decomposition of organic matter or from industrial processes. Thus, foraminiferal assemblages in marine waters surrounding Bremerton are responding markedly to conditions in the sediments, establishing the efficacy of using foraminifera as a tool for monitoring benthic ecosystems in Puget Sound.