Causality of an extreme harmful algal bloom in Monterey Bay, California, during the 2014–2016 northeast Pacific warm anomaly

Abstract

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.

Habitat compression and ecosystem shifts as potential links between marine heatwave and record whale entanglements

“…To complicate things, anchovy are known vectors for concentrating and transferring domoic acid toxin to their predators. Therefore, domoic acid poisoning may have influenced behavior and health of whales feeding on anchovy 26,28 .…”

“…During 2014-2016, a MHW occurred in the North Pacific that resulted in an unprecedented multi-year warming event 5 . The impacts of the MHW were wide ranging 9,10 , but notably caused a sustained bloom of toxic Pseudo-nitzschia diatoms that led to the persistence of domoic acid (a neurotoxin impacting marine wildlife; e.g., shellfish poisoning 10,[26][27][28] , record changes in biodiversity of pelagic species 29 , and an unprecedented delay in the opening of the commercial Dungeness crab (Metacarcinus magister) fishery in California (a fixed-gear trap fishery with vertical lines 6 ). The crab fishery, which in recent decades has been among the largest by both volume and value in California [30][31][32] , normally opens in November and continues through mid-July, with catches peaking shortly after the initial opening and tapering to low levels throughout spring and early summer.…”

“…We hypothesize that onshore compression of the coastal upwelling ecosystem was at the root of the unusually high concentrations of whales occurring within the primary area of the crab fishery. Our hypothesis is summarized as the following sequence: (a) the MHW contributed to upwelling habitat compression, coinciding with the prevalence of domoic acid 10,28 , increases in epipelagic biodiversity due to the combined high abundance of warm-and cool-water species, and altered forage species availability (krill and anchovy abundance) 29,42 ; (b) humpback whales exhibited prey-switching behavior and distribution shift in response to upwelling habitat compressionrelated changes in forage availability 43,44 , resulting in (c) an amplified spatial overlap of whales and crab fishing gear during 2014-2016. This overlap was intensified in spring 2016 when the opening of the crab fishery was delayed in response to domoic acid contamination in crabs such that it coincided with the migratory peak arrival of whales in the CCLME.…”

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, 2016;. 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 , subtropical zooplankton species appearances and community composition rearrangements (Fisher et al, 2015;Lilly & Ohman, 2018;Peterson et al, 2017), coastwide harmful algal blooms and associated marine mammal toxicity (McCabe et al, 2016;Ryan et al, 2017), and large-scale seabird mortality events .…”

Application of Landsat 8 for Monitoring Impacts of Wastewater Discharge on Coastal Water Quality

“…During normal operations, treated wastewater is discharged from the 5-mile outfall pipe at the head of a submarine canyon that quickly drops off to over 100 m depth (Figure 1), allowing for dilution and mixing and limiting the impact on the near-surface phytoplankton community. During the diversion, there was major concern not only in regards to the magnitude of nitrogen being released into surface waters, but also in regards to the species of the nitrogen being released (Howarth and Marino, 2006) as it may cause shifts in phytoplankton community structure due to different nutrient preferences among algal taxa (Howard et al, 2007;Ryan et al, 2017). Ammonium is the most biologically available form of nitrogen and is usually present in the euphotic zone in limited concentrations because it is assimilated so quickly.…”