The pelagic ecosystem in the Northern California Current off Oregon during the 2014–2016 warm anomalies within the context of the past 20 years

Abstract

A warm anomaly in the upper ocean, colloquially named “the Blob,” appeared in the Gulf of Alaska during the calm winter of 2013–2014, spread across the northern North Pacific (NP) Ocean, and shifted eastward and onto the Oregon shelf. At least 14 species of copepods occurred which had never been observed in shelf/slope waters off Oregon, some of which are known to have NP Gyre affinities, indicating that the source waters of the coastal “Blob” were likely of both offshore (from the west) and subtropical/tropical origin. The anomalously warm conditions were reduced during strong upwelling in spring 2015 but returned when upwelling weakened in July 2015 and transitioned to downwelling in fall 2015. The extended period of warm conditions resulted in prolonged effects on the ecosystem off central Oregon, lasting at least through 2016. Impacts to the lower trophic levels were unprecedented and include a novel plankton community composition resulting from increased copepod, diatom, and dinoflagellate species richness and increased abundance of dinoflagellates. Additionally, the multiyear warm anomalies were associated with reduced biomass of copepods and euphausiids, high abundance of larvaceans and doliolids (indictors of oligotrophic ocean conditions), and a toxic diatom bloom (Pseudo‐nitzschia) throughout the California Current in 2015, thereby changing the composition of the food web that is relied upon by many commercially and ecologically important species.

Marine heat waves, climate change, and failed spawning by coastal invertebrates

“…). These results are consistent with observations made at other locations on the Oregon coast (Peterson et al ). In 2015, surface wave heights were significantly lower than those observed historically and in 2014 and 2016 (Fig.…”

“…This MHW was christened the “warm blob” (Bond et al ). Water from the “warm blob” moved onto the continental shelf in September 2014 (Peterson and Robert ), well after our winter 2014 sampling, and bathed the shore during our winter 2015 sampling (Bond et al ; Peterson et al ; Oliver et al ). Our sampling in winter 2016 occurred during the strong 2015/2016 El Niño (Newman et al ), another MHW.…”

“…The warmer seawater during the MHWs may have prevented or slowed normal gametogenesis such that, come winter, ripe gametes were not available for spawning. Falling temperatures in the fall initiates gametogenesis in a variety of temperate chiton and worm taxa (Himmelman ; Lawrence and Soame ); sea surface temperatures did not drop in the fall of 2015 during the warm blob or in 2016 during the El Niño (Peterson et al ). In some abalone species, sperm production stops at higher temperatures (Rogers‐Bennett et al ).…”

Biogeochemical Anomalies at Two Southern California Current System Moorings During the 2014–2016 Warm Anomaly‐El Niño Sequence

“…The sequence of the 2014–2015 Warm Anomaly followed immediately by the 2015 – 2016 El Niño produced more than 2 years of anomalous physical oceanographic conditions in the CCS, notably extremely warm temperatures and increased water column stratification (Jacox et al, ; Zaba & Rudnick, ). Despite known differences in physical forcing mechanisms, the Warm Anomaly had coastwide impacts on CCS ecosystems similar to those observed during El Niño events, including anomalously deep chlorophyll maxima (Zaba & Rudnick, ), subtropical zooplankton species appearances and community composition rearrangements (Fisher et al, ; Lilly & Ohman, ; Peterson et al, ), coastwide harmful algal blooms and associated marine mammal toxicity (McCabe et al, ; Ryan et al, ), and large‐scale seabird mortality events (Peterson et al, ).…”

Range extension for the region of sympatry between the nudibranchsHermissenda opalescensandHermissenda crassicornisin the northeastern Pacific

“…This suggests that the presence of H. opalescens in British Columbia is a novel phenomenon. Northward range shifts in the northeast Pacific have also been documented over recent years for several other nudibranchs (Goddard et al 2016), mole crabs (Wonham and Hart 2018), copepods (Peterson et al 2017), several species of fish (Auth et al 2018;Halpin et al 2018a), and cetaceans (Halpin et al 2018b). In the summer of 2016, we also recorded anecdotal observations of other southern species in the waters near the Bamfield Marine Sciences Centre on Vancouver Island, including the nudibranch, Dirona picta MacFarland, 1905(C. Tamis, R. Wyeth, personal observation, 2016, striped shore crabs, Pachygrapsus crassipes Randall, 1840(C. Neufeld, T. Eastham, personal observation, 2016, and brown pelicans Pelecanus occidentalis Linnaeus, 1766(S. Gray, personal communication, 2016.…”