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- Causality of an extreme harmful algal bloom in Monterey Bay, California, during the 2014-2016 northeast Pacific warm anomaly
- Export Date: 26 June 2017, Article in Press, An ecologically and economically disruptive harmful algal bloom (HAB) affected much of the northeast Pacific margin in 2015, during a prolonged oceanic warm anomaly. Caused by diatoms of the genus Pseudo-nitzschia, this HAB produced the highest particulate concentrations of the biotoxin domoic acid (DA) ever recorded in Monterey Bay, California. Bloom inception followed strong upwelling during the spring transition, which introduced nutrients and eliminated the warm anomaly locally. Subsequently, moderate and intermittent upwelling created favorable conditions for growth and accumulation of HAB biomass, which was dominated by a highly toxigenic species, P. australis. High cellular DA concentrations were associated with available nitrogen for DA synthesis coincident with silicate exhaustion. This nutrient influence resulted from two factors: (1) disproportionate depletion of silicate in upwelling source waters during the warm anomaly, the most severe depletion observed in 24 years, and (2) silicate uptake by the dense diatom bloom
- Ryan, Kudela, Birch, Blum, Bowers, Chavez, Doucette, Hayashi, Marin, Mikulski, Pennington, Scholin, Smith, Woods, Zhang
- Pseudo-nitzschia species composition varies concurrently with domoic acid concentrations during two different bloom events in the Southern California Bight
- The San Pedro Shelf (SPS) region of the Southern California Bight has witnessed an increase of Pseudo-nitzschia spp. blooms during the past decade, although the domoic acid (DA) concentrations observed during these events have varied considerably. This study compared the extent, timing and environmental controls of Pseudo-nitzschia blooms that were observed in two consecutive years on the SPS. Environmental conditions were characterized during shipboard surveys during spring 2013 and 2014 along an onshore–offshore transect at surface and subsurface depths. A Pseudo-nitzschia bloom of similar cell abundances was observed during each year, yet maximal DA concentrations differed by nearly two orders of magnitude. Environmental parameters were favorable for Pseudo-nitzschia spp. growth in both years, but few factors could be identified that specifically pertained to DA, with the exception that toxicity correlated negatively with dissolved silicic acid concentrations. Automated ribosomal intergenic spacer analysis for Pseudo-nitzschia species indicated that the relative abundance of toxin-producing species had a strong influence on DA concentrations between years, with high-DA concentrations corresponding to Pseudo-nitzschia communities dominated by P. australis/P. seriata. Factors explaining the preferential growth of particular Pseudo-nitzschia species remain enigmatic but are important for predicting toxic events attributable to these taxa.
- Smith, Gellene, Hubbard, Bowers, Kudela, Hayashi, Caron