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Physiological Buffering by a Marine Macroalgae Ameliorates Ocean Acidification and Warming Effects on a Large Foraminifer

Paper Reviewed
Doo, S.S., Leplastrier, A., Graba-Landry, A., Harianto, J., Coleman, R.A. and Byrne, M. 2020. Amelioration of ocean acidification and warming effects through physiological buffering of a macroalgae. Ecology and Evolution, DOI: 10.1002/ece3.6552.

The overwhelming majority of ocean acidification studies conducted to date involve assessing potential impacts on a given species in isolation. In the words of Doo et al. (2000), this is unfortunate and problematic because such experiments "do not capture ecologically relevant scenarios where the potential for multi-organism physiological interactions is assessed." Such relevant scenarios include the operation of compensatory mechanisms whereby interactions between multiple organisms allow for physiological modification to buffer against stress and maintain ecological equilibria. For example, Doo et al. note certain algal species have the potential to ameliorate the negative effects of ocean acidification (defined by a CO2-induced reduction in seawater pH) on calcifying marine organisms by increasing the pH of surrounding seawater via the process of photosynthesis.

In the present study, this team of six researchers purposed to examine the physiological buffering potential of a marine macroalgae (Laurencia intricata) on the growth and calcification response of a large benthic foraminifer (Marginopora vertebralis) exposed to different scenarios of ocean warming and acidification. The experiment was conducted at the Lizard Island Research Station in Australia where specimens of M. vertebralis were exposed to a full-factorial design of two temperature (ambient = 26°C and elevated = 29°C) and two pH (ambient = 8.0 and low = 7.7) treatments in isolation from, or in combination with, L. intricata. The duration of the treatments was 15 days.

Reporting on their findings, Doo et al. say that when incubated in isolation, M. vertebralis exhibited "reduced growth in end-of-century projections of ocean acidification conditions, while calcification rates were lowest in the high-temperature, low-pH treatment." However, they note "association with L. intricata ameliorated these stress effects with the growth and calcification rates of M. vertebralis being similar to those observed in ambient conditions."

In commenting on these important findings the authors write they "indicate that the association with L. intricata increases the resilience of M. vertebralis to climate change stress, providing one of the first examples of physiological buffering by a marine alga that can ameliorate the negative effects of changing ocean conditions." Consequently, given that the entire future outlook of this foraminifer changed from bad to good when allowing for its interaction with an ecologically-relevant algal species, Doo et al. call for further investigations into "species interactions, particularly multispecies symbioses that provide biological buffering services" as scientists attempt to discern the true fate of marine organisms in response to projected changes in ocean warming and acidification.

Posted 17 February 2021