Massive Mortality of a Planktivorous Seabird in Response to a Marine Heatwave

Abstract

Climate change has exacerbated the occurrence of large‐scale sea surface temperature anomalies, or marine heatwaves (MHWs)—extreme phenomena often associated with mass mortality events of marine organisms. Using a combination of citizen science and federal data sets, we investigated the causal mechanisms of the 2014/2015 die‐off of Cassin's Auklets (Ptychoramphus aleuticus), a small zooplanktivorous seabird, during the NE Pacific MHW of 2013–2015. Carcass deposition followed an effective reduction in the energy content of mesozooplankton, coincident with the loss of cold‐water foraging habitat caused by the intrusion of the NE Pacific MHW into the nearshore environment. Models examining interannual variability in effort‐controlled carcass abundance (2001–2014) identified the biomass of lipid‐poor zooplankton as the dominant predictor of increased carcass abundance. In 2014, Cassin's Auklets dispersing from colonies in British Columbia likely congregated into a nearshore band of cooler upwelled water and ultimately died from starvation following the shift in zooplankton composition associated with onshore transport of the NE Pacific MHW. For Cassin's Auklets, already in decline due to ocean warming, large‐scale and persistent MHWs might represent a global population precipice.

Predator‐mediated effects of severe drought associated with poor reproductive success of a seabird in a cross‐ecosystem cascade

“…Higher marine PC1 scores and specifically colder ocean temperatures (SST) and a positive NPGO index (>1.1) were associated with higher than average breeding success (Figures b, ). These favorable conditions likely mean better foraging conditions and increased prey availability for murrelets similar to how it benefits other seabirds in the California Current ecosystem (Ainley, ; Jones et al, ). Only when the NPGO was positive, in the absence of drought conditions, was murrelet nest success high enough to produce a stable or increasing population growth rate (Figure ).…”

Oceanographic drivers of winter habitat use in Cassin’s Auklets

“…For Cassin's Auklets, the marine heat wave in the Eastern North Pacific during 2014–2015 led to one of the largest die‐offs ever recorded for this species on the U.S. west coast (Jones et al. ). Along with an increased risk of mortality, poor conditions and lack of adequate prey during the winter may force birds to skip reproduction the following year (Genovart et al.…”

“…Similar advection and subsequent decline in primary production led up to the winter of 2015-2016 (Whitney 2015), likely resulting in a destabilization of a predictable supply of prey, including E. pacifica; forcing Auklets to travel longer distances and over deeper, more offshore waters to find profitable zooplankton abundances. For Cassin's Auklets, the marine heat wave in the Eastern North Pacific during 2014-2015 led to one of the largest die-offs ever recorded for this species on the U.S. west coast (Jones et al 2018). Along with an increased risk of mortality, poor conditions and lack of adequate prey during the winter may force birds to skip reproduction the following year (Genovart et al 2013).…”

The Role of Clouds and Surface Heat Fluxes in the Maintenance of the 2013–2016 Northeast Pacific Marine Heatwave

“…MHWs often have devastating ecological and economic impacts, which can increase in severity with the length and intensity of the MHW. Anomalously warm SSTs can cause coral bleaching (Hughes et al, 2017;Le Nohaïc et al, 2017), movement of marine species to cooler water (Cavole et al, 2016;Oliver, Benthuysen, et al, 2018;Wernberg et al, 2016), mass species die offs (Jones et al, 2018;Oliver, Benthuysen, et al, 2018;Garrabou et al, 2009), and harmful algal blooms (McCabe et al, 2016). For the NE Pacific MHW in particular, the harmful algal bloom associated with the event was the largest ever recorded and caused closures of many lucrative fisheries in the U.S. Pacific Northwest (Cavole et al, 2016;McCabe et al, 2016).…”