Experiment: Competition between calcifying and noncalcifying temperate marine macroalgae under elevated CO2 levels

• Main Author: Hofmann, Laurie C
• Format: Dataset
• Language: English
• Published: PANGAEA 2012
• Subjects: Alkalinity; total; Aragonite saturation state; Benthos; Bicarbonate ion; BIOACID; Biological Impacts of Ocean Acidification; Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbohydrates; insolube; in tissue; insolube/Carbohydrates; solube ratio; solube; Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a; Chlorophyll b; Chondrus crispus; Coast and continental shelf; Community composition and diversity; Containers and aquaria (20-1000 L or < 1 m**2); Corallina officinalis; Coverage; Derbesia marina; Dumontia incrassata; Electron transport rate; relative; Electron transport rate efficiency; Entire community; Fucus vesiculosus; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross oxygen evolution; per chlorophyll a; Group; Growth/Morphology; Northeast Atlantic; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.830074; https://doi.org/10.1594/PANGAEA.830074

Since pre-industrial times, uptake of anthropogenic CO2 by surface ocean waters has caused a documented change of 0.1 pH units. Calcifying organisms are sensitive to elevated CO2 concentrations due to their calcium carbonate skeletons. In temperate rocky intertidal environments, calcifying and noncalcifying macroalgae make up diverse benthic photoautotrophic communities. These communities may change as calcifiers and noncalcifiers respond differently to rising CO2 concentrations. In order to test this hypothesis, we conducted an 86 d mesocosm experiment to investigate the physiological and competitive responses of calcifying and noncalcifying temperate marine macroalgae to 385, 665, and 1486 µatm CO2. We focused on comparing 2 abundant red algae in the Northeast Atlantic: Corallina officinalis (calcifying) and Chondrus crispus (noncalcifying). We found an interactive effect of CO2 concentration and exposure time on growth rates of C. officinalis, and total protein and carbohydrate concentrations in both species. Photosynthetic rates did not show a strong response. Calcification in C. officinalis showed a parabolic response, while skeletal inorganic carbon decreased with increasing CO2. Community structure changed, as Chondrus crispus cover increased in all treatments, while C. officinalis cover decreased in both elevated-CO2 treatments. Photochemical parameters of other species are also presented. Our results suggest that CO2 will alter the competitive strengths of calcifying and noncalcifying temperate benthic macroalgae, resulting in different community structures, unless these species are able to adapt at a rate similar to or faster than the current rate of increasing sea-surface CO2 concentrations.