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Diurnal fluctuations in seawater pH influence the response of a calcifying macroalga to ocean acidification
journal contribution
posted on 2023-05-17, 22:26 authored by Cornwall, CE, Hepburn, CD, McGraw, CM, Currie, KI, Pilditch, CA, Hunter, KA, Philip BoydPhilip Boyd, Catriona HurdCatriona HurdCoastal ecosystems that are characterized by kelp forests encounter daily pH fluctuations, driven by photosynthesis and respiration, which are larger than pH changes owing to ocean acidification (OA) projected for surface ocean waters by 2100. We investigated whether mimicry of biologically mediated diurnal shifts in pH—based for the first time on pH time-series measurements within a kelp forest—would offset or amplify the negative effects of OA on calcifiers. In a 40-day laboratory experiment, the calcifying coralline macro- alga, Arthrocardia corymbosa, was exposed to two mean pH treatments (8.05 or 7.65). For each mean, two experimental pH manipulations were applied. In one treatment, pH was held constant. In the second treatment, pH was manipulated around the mean (as a step-function), 0.4 pH units higher during daylight and 0.4 units lower during darkness to approximate diurnal fluctuations in a kelp forest. In all cases, growth rates were lower at a reduced mean pH, and fluctuations in pH acted additively to further reduce growth. Photosynthesis, recruitment and elemental composition did not change with pH, but d13C increased at lower mean pH. Including environmental hetero- geneity in experimental design will assist with a more accurate assessment of the responses of calcifiers to OA.
History
Publication title
Proceedings of the Royal Society BVolume
280Article number
20132201Number
20132201Pagination
1-8ISSN
1471-2954Department/School
Institute for Marine and Antarctic StudiesPublisher
The Royal Society PublishingPlace of publication
UKRights statement
Copyright 2013 The Author(s) Published by the Royal Society. All rights reservedRepository Status
- Restricted