Biogeochemical anomalies at two Southern California Current system moorings during the 2014-2016 Warm Anomaly-El Nino Sequence

TitleBiogeochemical anomalies at two Southern California Current system moorings during the 2014-2016 Warm Anomaly-El Nino Sequence
Publication TypeJournal Article
Year of Publication2019
AuthorsLilly L.E, Send U, Lankhorst M., Martz T.R, Feely R.A, Sutton A.J, Ohman MD
Date Published2019/10
Type of ArticleArticle; Early Access
ISBN Number2169-9275
Accession NumberWOS:000490470000001
KeywordsAragonite; Aragonite saturation state; california current system; El Nino; impacts; monterey bay; moorings; northern california; ocean acidification; oceanography; Pelagic ecosystem; pteropods; saturation; spatiotemporal variability; united-states; Warm anomaly; west-coast; Zooplankton
Abstract

We analyzed impacts of the 2014-2015 Pacific Warm Anomaly and 2015-2016 El Nino on physical and biogeochemical variables at two southern California Current System moorings (CCE2, nearshore upwelling off Point Conception; CCE1, offshore California Current). Nitrate and Chl-a fluorescence were <1 mu M and <1 Standardized Fluorescence Unit, respectively, at CCE2 for the entire durations of the Warm Anomaly and El Nino, the two longest periods of such low values in our time series. Negative nitrate and Chl-a anomalies at CCE2 were interrupted briefly by upwelling conditions in spring 2015. Near-surface temperature anomalies appeared simultaneously at both moorings in spring 2014, indicating region-wide onset of Warm Anomaly temperatures, although sustained negative nitrate and Chl-a anomalies only occurred offshore at CCE1 during El Nino (summer 2015 to spring 2016). Warm Anomaly temperature changes were expressed more strongly in near-surface (<40 m) than subsurface (75 m) waters at both moorings, while El Nino produced comparable temperature anomalies at near-surface and subsurface depths. Nearshore omega(aragonite) at 76 m showed notably fewer undersaturation events during both warm periods, suggesting an environment more conducive to calcifying organisms. Planktonic calcifying molluscs (pteropods and heteropods) increased markedly in springs 2014 and 2016 and remained modestly elevated in spring 2015. Moorings provide high-frequency measurements essential for resolving the onset timing of anomalous conditions and frequency and duration of short-term (days-to-weeks) perturbations (reduced nitrate and aragonite undersaturation events) that can affect marine organisms.

DOI10.1029/2019jc015255
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