ENVIRONMENTAL FACTORS INFLUENCING FORAMINIFERAL DISTRIBUTION IN BELLINGHAM BAY, NORTHERN PUGET SOUND

The purpose of this study was to monitor foraminiferal assemblages in Bellingham Bay, northern Puget Sound, Washington, over time and correlate any changes with known environmental factors. Bellingham Bay is located northeast of the Straits of Juan de Fuca and is separated from the Straits of Georgia by the Lummi Peninsula, Portage and Lummi islands, and is bordered to the east by the city of Bellingham. Freshwater input comes primarily from the Nooksack River that originates on the volcanic peak of Mt. Baker. Sediment size is dominantly silt and clay.

Benthic infaunal indices in Bellingham Bay are low, though they increase southward, and degraded sediment conditions have been recorded. Ten foraminiferal samples from a single (temporal) site, collected by the Washington Department of Ecology between 1997 and 2012, were utilized. In addition, several samples from other parts of Bellingham Bay were examined for comparison. Results from the single temporal site show extremely high foraminiferal density (as high as 6120 individuals/gram dry sediment) in many sites. Conversely, some of the additional samples produced no foraminifera at all, and consisted of only comminuted plant debris. Species richness varied between 1 and 12, with the highest in the inner harbor sample and lowest in the temporal sample collected in 2006. The temporal samples showed a striking trend of decreasing foraminiferal density over the time studied. Eggerella advena, a highly tolerant species known to be an opportunistic colonizer of polluted areas particularly those impacted by sewage, was the dominant species in the temporal samples; this site lies offshore the sewage treatment plant for the City of Bellingham. The proportion of E. advena in these samples decreased over time, possibly due to implementation of a comprehensive storm-water management plan beginning in 1997. The plan was updated in 2007. In 2004, the proportion of E. advena rose suddenly and then fell again in subsequent years. The fluctuations could be attributed to major storms and flooding that occurred at the end of 2003 and which overwhelmed the storm-water system and may have released sewage into the Bay.