Pelagic calcifiers face increased mortality and habitat loss with warming and ocean acidification

Abstract

Global change is impacting the oceans in an unprecedented way, and multiple lines of evidence suggest that species distributions are changing in space and time. There is increasing evidence that multiple environmental stressors act together to constrain species habitat more than expected from warming alone. Here, we conducted a comprehensive study of how temperature and aragonite saturation state act together to limit Limacina helicina, globally distributed pteropods that are ecologically important pelagic calcifiers and an indicator species for ocean change. We co-validated three different approaches to evaluate the impact of ocean warming and acidification (OWA) on the survival and distribution of this species in the California Current Ecosystem. First, we used colocated physical, chemical, and biological data from three large-scale west coast cruises and regional time series; second, we conducted multifactorial experimental incubations to evaluate how OWA impacts pteropod survival; and third, we validated the relationships we found against global distributions of pteropods and carbonate chemistry. OWA experimental work revealed mortality increases under OWA, while regional habitat suitability indices and global distributions of L. helicina suggest that a multi-stressor framework is essential for understanding pteropod distributions. In California Current Ecosystem habitats, where pteropods are living close to their thermal maximum already, additional warming and acidification through unabated fossil fuel emissions (RCP 8.5) are expected to dramatically reduce habitat suitability.

The Impact of Zooplankton Calcifiers on the Marine Carbon Cycle

“…The present global dependencies of biomass on temperature can differ from the results of local studies (e.g., a negative dependency of pteropod biomass on temperature as found in Bednaršek et al. (2022) and species‐specific responses of foraminifers to a range of environmental parameters as found by Weinkauf et al. (2016)), as our models capture large‐scale climatological effects contrary to local models which reflect physiological responses to environmental gradients on a much smaller scale.…”

“…Previous work identified carbonate chemistry as an important predictor for net calcification on a local scale (Bednaršek & Ohman, 2015; Bednaršek et al., 2022; Lischka et al., 2011; Manno et al., 2017; Mekkes, Renema, et al., 2021). CO 2 ‐rich waters characterized by low pH, low calcite, and low aragonite saturation states may negatively affect certain calcifying organisms by increasing their dissolution and lowering their calcification rate (Bednaršek, Feely, et al., 2017; Bednaršek et al., 2022; Mekkes, Renema, et al., 2021; Mekkes, Sepúlveda‐Rodríguez, et al., 2021).…”

“…CO 2 ‐rich waters characterized by low pH, low calcite, and low aragonite saturation states may negatively affect certain calcifying organisms by increasing their dissolution and lowering their calcification rate (Bednaršek, Feely, et al., 2017; Bednaršek et al., 2022; Mekkes, Renema, et al., 2021; Mekkes, Sepúlveda‐Rodríguez, et al., 2021). For pteropods, these changes in water chemistry can reduce their metabolic activity, increase shell dissolution, and decrease their growth and survival (Bednaršek et al., 2016; Bednaršek et al., 2022; Bednaršek, Feely, et al., 2017; Bednaršek, Klinger, et al., 2017; Gardner et al., 2017; Lischka et al., 2011; Lischka & Riebesell, 2012; Maas et al., 2015; Manno et al., 2007). Foraminifers are less sensitive to changes in saturation states as their shells are made of calcite (Orr et al., 2005; Weinkauf et al., 2016), but laboratory and field studies point to reduced calcification rates and metabolic depression for them as pH decreases (C. V. Davis et al., 2017; Iwasaki et al., 2019; Moy et al., 2009; Osborne et al., 2020), even though calcite saturation states are higher than aragonite saturation states.…”

“…Therefore, we likely underestimated the global latitudinal variability in our biomass predictions. Additionally, we could not include the effects of combined temperature stress and ocean acidification on the physiological and population level (Bednaršek et al., 2022). This might have caused an overestimation of calcification rates and populations in specific regions such as upwelling systems that are affected by multiple stressors.…”

“…They are generally omnivorous and can capture prey actively, but feeding preferences differ between species (Anderson et al., 1979; Caron & Bé, 1984; Rhumbler, 1911; Spindler et al., 1984) with some species also harboring facultative photosymbionts (Hemleben et al., 1989). The global abundances and habitat suitability of pteropods and foraminifers are known to be controlled by a range of environmental parameters, including temperature (Beaugrand et al., 2010; Bednaršek et al., 2022; Helaouët & Beaugrand, 2009; Jonkers et al., 2019), chlorophyll‐a as a proxy for food availability (Pinkerton et al., 2020; Thibodeau et al., 2019; Vereshchaka et al., 2022), and parameters related to physical mixing that influence phytoplankton growth through light availability and particle sinking rates (Bednaršek et al., 2022; Boyce et al., 2010; Govoni et al., 2010; Longhurst, 2007; Mackas et al., 2005; Rothschild & Osborn, 1988; Seuront et al., 2001).…”