The O2, pH and Ca2+ Microenvironment of Benthic Foraminifera in a High CO2 World

• Main Authors: Glas, Martin S, Fabricius, Katharina Elisabeth, de Beer, Dirk, Uthicke, Sven, Gilbert, Jack Anthony
• Format: Dataset
• Language: English
• Published: PANGAEA 2012
• Subjects: Alkalinity; total; standard deviation; Amphistegina radiata; Aragonite saturation state; Benthos; Bicarbonate ion; BIOACID; Biological Impacts of Ocean Acidification; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calcium ion; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; Coast and continental shelf; Coulometric titration; Date; Figure; Foraminifera; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Group; Heterostegina depressa; Heterotrophic prokaryotes; Hydrogen ion concentration; Identification; Individual code; Irradiance; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.833612; https://doi.org/10.1594/PANGAEA.833612

Ocean acidification (OA) can have adverse effects on marine calcifiers. Yet, phototrophic marine calcifiers elevate their external oxygen and pH microenvironment in daylight, through the uptake of dissolved inorganic carbon (DIC) by photosynthesis. We studied to which extent pH elevation within their microenvironments in daylight can counteract ambient seawater pH reductions, i.e. OA conditions. We measured the O2 and pH microenvironment of four photosymbiotic and two symbiont-free benthic tropical foraminiferal species at three different OA treatments (~432, 1141 and 2151 µatm pCO2). The O2 concentration difference between the seawater and the test surface (delta O2) was taken as a measure for the photosynthetic rate. Our results showed that O2 and pH levels were significantly higher on photosymbiotic foraminiferal surfaces in light than in dark conditions, and than on surfaces of symbiont-free foraminifera. Rates of photosynthesis at saturated light conditions did not change significantly between OA treatments (except in individuals that exhibited symbiont loss, i.e. bleaching, at elevated pCO2). The pH at the cell surface decreased during incubations at elevated pCO2, also during light incubations. Photosynthesis increased the surface pH but this increase was insufficient to compensate for ambient seawater pH decreases. We thus conclude that photosynthesis does only partly protect symbiont bearing foraminifera against OA.