A Tropical Tale: Influence of the Warm Blob on the Planktic Foraminifera Community off the Oregon Coast

In 2013, a warm water anomaly formed in the Gulf of Alaska and traveled along the west coast of North America, persisting in the eastern North Pacific for nearly 34 months. The ‘Warm Blob,’ as it was coined, had major impacts on the pelagic communities in the northern California Current as presented by studies of copepods, krill, gelatinous organisms, and phytoplankton (Peterson et al, 2017.) Foraminifera have not been studied in association with the Warm Blob event, yet these single-shelled marine protists provide a unique insight into the event as different species of planktic foraminifera are sensitive to sea surface temperature and thus their community assemblage reflects changes in oceanographic conditions.

This study describes the planktic foraminifera community found in a cross-shelf transect off the Oregon coast (44.6°N) during the Warm Blob years (2014-2016.) Samples were collected from plankton tows along the Newport Hydrographic Line, an ongoing 20+ year time series of hydrographic and biological sampling. Foraminifera assemblages naturally shift with warm and cold water events that occur on various temporal scales, driven by the El Niño Southern Oscillation, the Pacific Decadal Oscillation, and seasonal upwelling. However, during the Warm Blob years, tropical species were found in high abundance and closer nearshore compared to a historical foraminiferal assemblage record from this region. We also compared the Warm Blob species assemblages to more recently collected plankton tows (2018 and 2019) which represented a more typical cold-water assemblage following the Warm Blob. The Warm Blob represents a unique anomaly off the coast of Oregon that is well-recorded in the foraminiferal record. Foraminifera could provide insight in to the paleorecord of warm water events along the Oregon Coast.