Energetic context determines species and community responses to ocean acidification

Abstract

Physiological responses to ocean acidification are thought to be related to energetic trade-offs. Although a number of studies have proposed that negative responses to low pH could be minimized in situations where food resources are more readily available, evidence for such effects on individuals remain mixed, and the consequences of such effects at the community level remain untested. We explored the potential for food availability and diet quality to modify the effects of acidification on developing marine fouling communities in field-deployed mesocosms by supplementing natural food supply with one of two species of phytoplankton, differing in concentration of fatty acids. After 12 weeks, no species demonstrated the interactive effects generally predicted in the literature, where a positive overall effect of diet mitigated the negative overall effects of acidification. Rather, for some species, additional food supply appeared to bring out or exacerbate the negative effects of low pH. Community richness and structure were only altered by acidification, while space occupation and evenness reflected patterns of the most dominant species. Importantly, we find that acidification stress can increase the relative abundance of invasive species, even under resource conditions that otherwise prevented invasive species establishment. Overall, the proposed hypothesis regarding the ability for food addition to mitigate the negative effects of acidification is thus far not widely supported at species or community levels. It is clear that acidification is a strong driving force in these communities but understanding underlying energetic and competitive context is essential to developing mechanistic predictions for climate change responses.

Comparative Sensitivities of Zooplankton to Ocean Acidification Conditions in Experimental and Natural Settings

“…This strong positive relationship is consistent with evidence that food availability can mediate organismal response to OA (Thomsen et al, 2013;Pansch et al, 2014;Ramajo et al, 2016). We note, however, that this is not always the case: for example, Brown et al (2018Brown et al ( , 2020 found that food sufficiency exacerbated the negative effects of low pH on organismal performance. Given our limited dataset, the relationship between food availability and zooplankton abundance in our study should be interpreted with caution with respect to zooplankton response to OA.…”

Parental whole life cycle exposure modulates progeny responses to ocean acidification in slipper limpets

“…Similar calcification damage has been reported in bivalves exposed to long‐term OA (see the review by Zhao et al, 2020). One hypothesis to account for the size difference between pH treatments could be an energetic trade‐off between somatic growth, shell growth and repair, and reproduction (Brown et al, 2020). Alternatively, the observed size difference could be an artifact of maintaining a fixed concentration of the algal diet used.…”

Windows of vulnerability: Seasonal mismatches in exposure and resource identity determine ocean acidification’s effect on a primary consumer at high latitude

“…Brown et al, 2014; Poore et al, 2013; Russell et al, 2013). Several observational and manipulative experiments have also demonstrated that increased biomass of primary producers in high CO 2 conditions can buffer primary consumers from direct negative effects of acidification (Goldenberg et al, 2018; Kroeker et al, 2016; Thomsen et al, 2010), while other studies have suggested that increased food availability or quality does not mediate the effects of ocean acidification (Brown et al, 2020). No studies have captured how this dynamic plays out in winter conditions, when exposure to low pH/saturation states is likely to be most pronounced and resources most scarce.…”