El Niño-Related Thermal Stress Coupled With Upwelling-Related Ocean Acidification Negatively Impacts Cellular to Population-Level Responses in Pteropods Along the California Current System With Implications for Increased Bioenergetic Costs

Abstract

El Niño Negatively Impacts Pelagic Gastropods of a single parameter in the statistical analyses. High quantities of polyunsaturated fatty acids are susceptible to oxidative stress because of LPX, resulting in the loss of lipid reserves and structural damage to cell membranes, a potential mechanism explaining extreme pteropod sensitivity to low ar . Accumulation of oxidative damage requires metabolic compensation, implying energetic trade-offs under combined thermal and low ar and pH stress. Oxidative stress biomarkers can be used as early-warning signal of multiple stressors on the cellular level, thereby providing important new insights into factors that set limits to species' tolerance to in situ multiple drivers.

Biogeochemical Anomalies at Two Southern California Current System Moorings During the 2014–2016 Warm Anomaly‐El Niño Sequence

“…Bednaršek et al () showed negative pteropod responses in the northern CCS to the 2013–2016 combined marine heat wave, El Niño, and enhanced upwelling. Aguilera et al () similarly observed reductions in growth and egg production in the resident copepod Acartia tonsa in the Humboldt Current System under warm, acidic conditions in 2015.…”

“…The longest periods of consecutive aragonite undersaturation in our records during the Warm Anomaly and El Niño were significantly shorter than in 2011–2013 (see Table for values). Bednaršek et al () note that altered carbonate conditions have a dominant effect on pelagic mollusc health at the cellular level. The favorable carbonate conditions we observed likely provided some offset to thermal stress in 2014 and 2016, while moderate upwelling in spring 2015 produced less favorable carbonate conditions and may have negatively impacted organisms despite cooler temperatures and increased food availability.…”

“…El Niño is the dominant mode of interannual variability in the CCS and can produce anomalous circulation including advection of water masses into the southern CCS from Baja California or southern offshore waters (Chavez, 1996;Chavez et al, 2002;Jacox et al, 2016;Lynn & Bograd, 2002;Simpson, 1984). El Niño impacts on CCS ecosystems vary substantially, but past major El Niños reduced phytoplankton biomass (Chavez, 1996;Fiedler, 1984;Kahru & Mitchell, 2000), produced anomalous subtropical zooplankton influxes (Bednaršek et al, 2018;Lavaniegos et al, 2002;Lavaniegos & Ohman, 2007;Lilly & Ohman, 2018;Rebstock, 2001), and altered survival and spatial distributions of seabirds and marine mammals (Keiper et al, 2005; D. E. Lee et al, 2007;Thayer & Sydeman, 2007).…”

“…Ocean acidification threatens calcifying marine organisms because it lowers the saturation states (Ω) of aragonite and calcite, carbonate minerals essential for shell production, requiring organisms to expend more energy on shell formation and growth (Bednaršek et al, ; Bednaršek et al, ; Bednaršek et al, ; Hauri, Gruber, McDonnell, & Vogt, ). Bednaršek et al () found that the pteropod species Limacina helicina in the northern CCS (southern British Columbia to Monterey Bay, CA) experienced synergistic negative impacts from an enhanced upwelling season (low oxygen, pH, and Ω arag ) in spring 2016 combined with increased temperatures during the 2013–2015 marine heat wave (here referred to as the Warm Anomaly) and 2015–2016 El Niño. Analysis of anomalous perturbations to CCS ecosystems and predictions of future impacts must therefore consider not just the event at hand but also its potential combination with background conditions and other perturbations.…”

Locating gaps in the California Current System ocean acidification monitoring network

“…6 While these calcifying organisms tend to be small in size and receive less conservation attention than larger fauna, they underpin many food webs in the region; a decline in marine calcifying organisms could have ripple effects on entire communities and ecosystems. 6,9,10 Beyond the ecological impacts of OA on calcifying organisms and their interrelated food webs, OA may wield significant economic impacts by placing additional pressures on fished species. OA impacts have been estimated for several important fishery species.…”