Microenvironmental changes support evidence of photosynthesis and calcification inhibition in Halimeda under ocean acidification and warming, supplement to: Sinutok, Sutinee; Hill, R; Doblin, Martina A; Kühl, Michael; Ralph, Peter J (2012): Microenvironmental changes support evidence of photosynthesis and calcification inhibition in Halimeda under ocean acidification and warming. Coral Reefs, 31(4), 1201-1213

• Main Authors: Sinutok, Sutinee, Hill, R, Doblin, Martina A, Kühl, Michael, Ralph, Peter J
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2012
• Subjects: Benthos; Chlorophyta; Coast and continental shelf; Containers and aquaria 20-1000 L or < 1 m**2; Halimeda cylindracea; Halimeda macroloba; Laboratory experiment; Macroalgae; Plantae; Primary production/Photosynthesis; Single species; South Pacific; Temperate; Temperature; Figure; Species; Incubation duration; Treatment; Maximum photochemical quantum yield of photosystem II; Maximum photochemical quantum yield of photosystem II, standard error; Effective quantum yield; Effective quantum yield, standard error; Excitation pressure; Excitation pressure, standard error; Distance; Irradiance; Oxygen; Oxygen, standard error; Gross photosynthesis rate, oxygen; Gross photosynthesis rate, oxygen, standard error; Oxygen, flux, diffusive; Oxygen, flux, diffusive, standard error; Temperature, water; Salinity; pH; Alkalinity, total; Alkalinity, total, standard error; Partial pressure of carbon dioxide water at sea surface temperature wet air; Partial pressure of carbon dioxide water at sea surface temperature wet air, standard error; Carbon dioxide; Carbon dioxide, standard error; Carbonate ion; Carbonate ion, standard error; Bicarbonate ion; Bicarbonate ion, standard error; Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard error; Aragonite saturation state; Aragonite saturation state, standard error; Carbonate system computation flag; Fugacity of carbon dioxide water at sea surface temperature wet air; Calcite saturation state; Potentiometric; Potentiometric titration; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. 2010; Ocean Acidification International Coordination Centre OA-ICC; Austral; Martina; Pacific; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.831527; https://doi.pangaea.de/10.1594/PANGAEA.831527

The effects of elevated CO2 and temperature on photosynthesis and calcification of two important calcifying reef algae (Halimeda macroloba and Halimeda cylindracea) were investigated with O2 microsensors and chlorophyll a fluorometry through a combination of two pCO2 (400 and 1,200 µatm) and two temperature treatments (28 and 32 °C) equivalent to the present and predicted conditions during the 2100 austral summer. Combined exposure to pCO2 and elevated temperature impaired calcification and photosynthesis in the two Halimeda species due to changes in the microenvironment around the algal segments and a reduction in physiological performance. There were no significant changes in controls over the 5-week experiment, but there was a 50-70 % decrease in photochemical efficiency (maximum quantum yield), a 70-80 % decrease in O2 production and a threefold reduction in calcification rate in the elevated CO2 and high temperature treatment. Calcification in these species is closely coupled with photosynthesis, such that a decrease in photosynthetic efficiency leads to a decrease in calcification. Although pH seems to be the main factor affecting Halimeda species, heat stress also has an impact on their photosystem II photochemical efficiency. There was a strong combined effect of elevated CO2 and temperature in both species, where exposure to elevated CO2 or temperature alone decreased photosynthesis and calcification, but exposure to both elevated CO2 and temperature caused a greater decline in photosynthesis and calcification than in each stress individually. Our study shows that ocean acidification and ocean warming are drivers of calcification and photosynthesis inhibition in Halimeda. Predicted climate change scenarios for 2100 would therefore severely affect the fitness of Halimeda, which can result in a strongly reduced production of carbonate sediments on coral reefs under such changed climate conditions. : In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne et al, 2011) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation is 2014-05-06.