Seawater carbonate chemistry and photosynthesis and photochemical efficiency of Porolithon onkodes

• Main Authors: Briggs, Amy A, Carpenter, Robert C
• Format: Dataset
• Language: English
• Published: PANGAEA 2019
• Subjects: Alkalinity; total; standard error; Aragonite saturation state; Benthos; Bicarbonate ion; Calcification/Dissolution; Calcification rate of calcium carbonate; Calcite saturation state; Calculated using seacarb; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Coast and continental shelf; Containers and aquaria (20-1000 L or < 1 m**2); Cooks_Bay_Moorea; EXP; Experiment; Fluorescence; maximum; minimum; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross photosynthesis rate; oxygen; Identification; Initial slope of the photosynthesis-irradiance curve; Irradiance; Laboratory experiment; Light; Light saturation; Macroalgae; Maximum gross photosynthesis rate; Maximum photochemical quantum yield of photosystem II; Net photosynthesis rate; Pacific; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.920025; https://doi.org/10.1594/PANGAEA.920025

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