Contrasting responses of photosynthesis and photochemical efficiency to ocean acidification under different light environments in a calcifying alga

摘要: Ocean acidification (OA) is predicted to enhance photosynthesis in many marine taxa. However, photophysiology has multiple components that OA may affect differently, especially under different light environments, with potentially contrasting consequences for photosynthetic performance. Furthermore, because affects energetic budgets and internal acid-base dynamics, changes it due or could mediate the sensitivity of other biological processes (e.g. respiration calcification). To better understand these effects, we conducted experiments on Porolithon onkodes, a common crustose coralline alga Pacific coral reefs, crossing pCO2 treatments. Results indicate inhibited some aspects (maximum photochemical efficiency), facilitated others (α, responsiveness sub-saturating light), had no effect gross photosynthesis), first two effects depending treatment level. Light also exacerbated increase dark-adapted OA, but did not alter decline calcification. Light-adapted respond indirect photosynthesis. Combined, results will interact resource allocation among P. likely shifting its tolerance, constraining narrower range environments.