Biological impacts of the 2013-2015 warm-water anomaly in the Northeast Pacific

TitleBiological impacts of the 2013-2015 warm-water anomaly in the Northeast Pacific
Publication TypeJournal Article
Year of Publication2016
AuthorsCavole L.M, Demko A.M, Diner R.E, Giddings A., Koester I., Pagniello C, Paulsen M.L, Ramirez-Valdez A., Schwenck S.M, Yen N.K, Zill M.E, Franks PJS
Date Published2016/06
Type of ArticleArticle
ISBN Number1042-8275
Accession NumberWOS:000380572500030
Keywordscalifornia current; climate regime; current system; distributions; el-nino; fish; ne pacific; ocean; sea lion; southern-california

A large patch of anomalously warm water (nicknamed "the Blob") appeared off the coast of Alaska in the winter of 2013-2014 and subsequently stretched south to Baja California. This northeastern Pacific warm-water anomaly persisted through the end of 2015. Scientists and the public alike noted widespread changes in the biological structure and composition of both open ocean and coastal ecosystems. Changes included geographical shifts of species such as tropical copepods, pelagic red crabs, and tuna; closures of commercially important fisheries; and mass strandings of marine mammals and seabirds. The ecological responses to these physical changes have been sparsely quantified and are largely unknown. Here, we provide a bottom-up summary of some of the biological changes observed in and around the areas affected by the Blob.

Short TitleOceanography

The warm-water anomaly of 2013–2015 resulted in many changes in northeastern Pacific ecosystems. Increased vertical stratification due to the WWA along with decreased nutrient flux to the surface appeared to be responsible for the observed reduction in total phytoplankton biomass. This decrease in phytoplankton availability, along with elevated sea surface temperatures, caused significant changes in zooplankton and marine invertebrate populations, with many species shifting their distributions toward cooler, more northern waters. Sightings suggest that tropical invertebrates such as tuna crabs were followed northward by their predators, tuna, which were in turn followed by their predators, sharks. Increased proportions of less nutritious warm-water copepod species and decreased abundance of krill were observed in the WWA regions. This loss of high-quality food caused population declines of many fish and seabird species and contributed to record marine mammal strandings. Concomitantly, the record-breaking concentration of DA during the persistent HAB was implicated in mass mortalities of several species and resulted in the closure of many fisheries. Economically, the effects of geographical shifts and the HAB have led to millions of dollars in losses among fishing industries. This is worrisome because the WWA may be a harbinger of things to come. As SSTs continue to rise with increasing global temperatures, many of the same scenarios observed during the WWA may be repeated, with dramatic ecological and economic consequences.

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