Limacina helicinashell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem

Abstract

Few studies to date have demonstrated widespread biological impacts of ocean acidification (OA) under conditions currently found in the natural environment. From a combined survey of physical and chemical water properties and biological sampling along the Washington-Oregon-California coast in August 2011, we show that large portions of the shelf waters are corrosive to pteropods in the natural environment. We show a strong positive correlation between the proportion of pteropod individuals with severe shell dissolution damage and the percentage of undersaturated water in the top 100 m with respect to aragonite. We found 53% of onshore individuals and 24% of offshore individuals on average to have severe dissolution damage. Relative to preindustrial CO 2 concentrations, the extent of undersaturated waters in the top 100 m of the water column has increased over sixfold along the California Current Ecosystem (CCE). We estimate that the incidence of severe pteropod shell dissolution owing to anthropogenic OA has doubled in near shore habitats since pre-industrial conditions across this region and is on track to triple by 2050. These results demonstrate that habitat suitability for pteropods in the coastal CCE is declining. The observed impacts represent a baseline for future observations towards understanding broader scale OA effects.

Response of O<sub>2</sub> and pH to ENSO in the California Current System in a high-resolution global climate model

“…If the pH drops below 7.75, which corresponds to arag < 1, waters become unfavorable for calcifying organisms to build and maintain their shell structure (e.g., Feely et al, 2008;Bednaršek et al, 2014;Bednaršek and Ohman, 2015). Our results suggest that during La Niña, the surface waters are more corrosive but also more oxygenated than during El Niño, while the waters below 100 m are both more corrosive and more deoxygenated.…”

“…The upwelled waters fuel biological production in the CalCS but are also characterized by lower O 2 and lower pH than the surrounding surface waters (e.g., Bograd et al, 2008;Nam et al, 2011). Although the CalCS is accustomed to seasonal fluctuations in O 2 and pH, several observational studies sug-gest that both have decreased in the last decades, particularly within 100 km of the coast (e.g., Bograd et al, 2008;Feely et al, 2008;Nam et al, 2011;Bednaršek et al, 2014;Bednaršek and Ohman, 2015). Specifically, Bograd et al (2008) found a shoaling of the hypoxic threshold, which is typically considered to be ∼ 60 µmol kg −1 (Gray et al, 2002;Diaz and Rosenberg, 2008;Vaquer-Sunyer and Duarte, 2008), of up to 90 m in the southern CalCS between 1984and 2006.…”

Species-specific responses to ocean acidification should account for local adaptation and adaptive plasticity

“…Evaluating experimentally how marine organisms with multi-year generation times will respond to changes in physical-chemical conditions over long timescales can be extremely difficult. Comparative studies using species with geographic ranges spanning large environmental gradients in pH/p CO2 may help us to understand how long-term adaptation to different environments can modulate individual sensitivity to additional stressors 27,28 . However, there are few studies that have assessed how responses to changing pH/p CO2 conditions vary among individuals (that is, within the same species) from geographically distant populations [29][30][31] .…”

The effect of elevated carbon dioxide on the sinking and swimming of the shelled pteropod Limacina retroversa

“…saturation state have also shown signs of dissolution under scanning electron microscopy 56 (Bednaršek, et al 2012, Bednaršek, et al 2014, Bednaršek, and Ohman. 2015.…”