How ocean acidification can benefit calcifiers

Abstract

Reduction in seawater pH due to rising levels of anthropogenic carbon dioxide (CO) in the world's oceans is a major force set to shape the future of marine ecosystems and the ecological services they provide [1,2]. In particular, ocean acidification is predicted to have a detrimental effect on the physiology of calcifying organisms [3]. Yet, the indirect effects of ocean acidification on calcifying organisms, which may counter or exacerbate direct effects, is uncertain. Using volcanic CO vents, we tested the indirect effects of ocean acidification on a calcifying herbivore (gastropod) within the natural complexity of an ecological system. Contrary to predictions, the abundance of this calcifier was greater at vent sites (with near-future CO levels). Furthermore, translocation experiments demonstrated that ocean acidification did not drive increases in gastropod abundance directly, but indirectly as a function of increased habitat and food (algal biomass). We conclude that the effect of ocean acidification on algae (primary producers) can have a strong, indirect positive influence on the abundance of some calcifying herbivores, which can overwhelm any direct negative effects. This finding points to the need to understand ecological processes that buffer the negative effects of environmental change.

Boosted food web productivity through ocean acidification collapses under warming

“…The overall performance of both herbivores and predators was likely to have been positively affected as we focused on taxa more tolerant to ocean acidification stress (Kroeker et al., ; Wittmann & Portner, ). Likewise, at CO 2 vents generalist herbivores and meso‐predators that are exposed to elevated CO 2 over long term showed increases in their population sizes (Connell et al., ; Nagelkerken, Russell, Gillanders, & Connell, ). Thus, the propagation of enhanced bottom‐up forcing to higher food web levels as shown in our study provides a mechanistic understanding of why generalist consumers can experience increases, rather than decreases, in their population sizes in nature.…”

The duality of ocean acidification as a resource and a stressor

“…, Connell et al. ) that have been replicated in controlled macrocosms manipulating CO 2 (and thus pH) alone (Goldenberg et al. ).…”

Elevated trace elements in Posidonia oceanica and Cymodocea nodosa at six Mediterranean volcanic seeps

“…Shallow water CO 2 seeps have been used as natural analogues for future coastal ecosystems as they can have areas of seabed where entire communities of marine organisms are exposed to the shifts in carbonate chemistry that are expected due to continued anthropogenic CO 2 emissions (Hall-Spencer et al, 2008;Enochs et al, 2015;Connell et al, 2017). At such seeps, there are often elevated levels of H 2 S and trace elements (Vizzini et al, 2010;Kadar et al, 2012;Boatta et al, 2013) so care is needed when using them to assess the effects of low pH due to confounding factors that may be harmful to marine biota (Bary et al, 2010).…”

“…Shallow water CO 2 seeps represent natural analogues for future coastal ecosystems, providing entire seabed of marine communities exposed to the shifts in carbonate chemistry (low pH) expected for 21 st century (Hall-Spencer et al, 2008;Enochs et al, 2015;Connell et al, 2017). At such seeps, there are often elevated levels of trace elements and hydrogen sulphide (H 2 S) (Kadar et al, 2012;Boatta et al, 2013;Vizzini et al, 2013) combined with low pH that may be harmful to marine biota (Barry et al, 2010;Lauritano et al, 2015;Olivé et al, 2017).…”