Regulation of calcification site pH is a polyphyletic but not always governing response to ocean acidification.

Liu, Yi-Wei; Sutton, Jill N; Ries, Justin B; Eagle, Robert A · Sci Adv · 2020

basic_science · Level V

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Abstract

The response of marine-calcifying organisms to ocean acidification (OA) is highly variable, although the mechanisms behind this variability are not well understood. Here, we use the boron isotopic composition (δ<sup>11</sup>B) of biogenic calcium carbonate to investigate the extent to which organisms' ability to regulate pH at their site of calcification (pH<sub>CF</sub>) determines their calcification responses to OA. We report comparative δ<sup>11</sup>B analyses of 10 species with divergent calcification responses (positive, parabolic, threshold, and negative) to OA. Although the pH<sub>CF</sub> is closely coupled to calcification responses only in 3 of the 10 species, all 10 species elevate pH<sub>CF</sub> above pH<sub>sw</sub> under elevated pCO<sub>2</sub>. This result suggests that these species may expend additional energy regulating pH<sub>CF</sub> under future OA. This strategy of elevating pH<sub>CF</sub> above pH<sub>sw</sub> appears to be a polyphyletic, if not universal, response to OA among marine calcifiers-although not always the principal factor governing a species' response to OA.