A NEW RECORD OF PLANKTIC FORAMINIFERA COMMUNITY RESPONSE TO MARINE HEATWAVES IN THE NORTHEAST PACIFIC

Planktic foraminifera community assemblages and abundances are poorly studied in the Northeast Pacific (NEP) along the Oregon coast, aside from data collected nearly three decades ago during the Multitracers project (Ortiz et al., 1995; Ortiz and Mix, 1992; Ortiz et al., 1996). This research explores the planktic foraminifera community along the Newport Hydrographic Line, a long-term monitoring transect off the Oregon Coast (44.6ºN) where oceanographic samples have been collected periodically since the 1960s. Planktic foraminifera in samples from fall (Aug-Oct) research cruises between 2010-present were identified, counted, and investigated to assess interannual shifts in foraminifera abundance and community composition. During this timeframe, two marine heatwaves (MHWs) have impacted the region, most notably the 2014-2015 MHW colloquially termed ‘The Warm Blob’ (Bond et al., 2015). Foraminifera community assemblages are known to correlate with sea surface temperature and other hydrographic conditions (Kucera et al., 2007). Planktic foraminifera have not previously been studied in the NEP in the context of MHWs.

Results demonstrate that the foraminifera community assemblage shifts from colder water polar, subpolar and transitional species during colder years to warmer water subtropical and tropical species during the 2014-2015 MHW. During a second MHW of similar magnitude but shorter duration in 2019, the planktic foraminifera community shifted again to a warm water foraminifera assemblage but did not include tropical species. During periods of strong upwelling inferred from the BEUTI index (Jacox et al., 2018), the polar species Neogloboquadrina pachyderma (Ehrenberg, 1861) was abundant. A permutational multivariate analysis of variance (PERMANOVA) shows that the Bray-Curtis distances between samples is significantly correlated with sea surface temperature and inferred upwelling.

These results suggest that the planktic foraminifera community can be correlated to changes in surface hydrography as rapid as a MHW and might be useful as indicator species of transient environmental events in the northern California Current. Foraminifera community assemblage could also provide insight into the paleorecord of warm water events from sediments in the NEP.