Nutrient availability affects the response of the calcifying chlorophyte Halimeda opuntia (L.) J.V. Lamouroux to low pH

• Main Authors: Hofmann, Laurie C, Heiden, Jasmin, Bischof, Kai, Teichberg, Mirta
• Format: Dataset
• Language: English
• Published: PANGAEA 2014
• Subjects: Alkalinity; total; Aragonite saturation state; Benthos; Bicarbonate ion; BIOACID; Biological Impacts of Ocean Acidification; Biomass/Abundance/Elemental composition; Calcification/Dissolution; Calcification rate of calcium carbonate; Calcite saturation state; Calcium carbonate; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; organic; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbonic anhydrase; activity; Carbon organic/inorganic ratio; Chlorophyta; Coast and continental shelf; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Halimeda opuntia; Initial slope of rapid light curve; Laboratory experiment; Light saturation point; Macroalgae; Macro-nutrients; Maximal electron transport rate; relative; Mesocosm or benthocosm; Nitrate reductase activity; Nitrogen; Nitrogen/Phosphorus ratio; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.839344; https://doi.org/10.1594/PANGAEA.839344

Atmospheric carbon dioxide emissions cause a decrease in the pH and aragonite saturation state of surface ocean water. As a result, calcifying organisms are expected to suffer under future ocean conditions, but their physiological responses may depend on their nutrient status. Because many coral reefs experience high inorganic nutrient loads or seasonal changes in nutrient availability, reef organisms in localized areas will have to cope with elevated carbon dioxide and changes in inorganic nutrients. Halimeda opuntia is a dominant calcifying primary producer on coral reefs that contributes to coral reef accretion. Therefore, we investigated the carbon and nutrient balance of H. opuntia exposed to elevated carbon dioxide and inorganic nutrients. We measured tissue nitrogen, phosphorus and carbon content as well as the activity of enzymes involved in inorganic carbon uptake and nitrogen assimilation (external carbonic anhydrase and nitrate reductase, respectively). Inorganic carbon content was lower in algae exposed to high CO2, but calcification rates were not significantly affected by CO2 or inorganic nutrients. Organic carbon was positively correlated to external carbonic anhydrase activity, while inorganic carbon showed the opposite correlation. Carbon dioxide had a significant effect on tissue nitrogen and organic carbon content, while inorganic nutrients affected tissue phosphorus and N:P ratios. Nitrate reductase activity was highest in algae grown under elevated CO2 and inorganic nutrient conditions and lowest when phosphate was limiting. In general, we found that enzymatic responses were strongly influenced by nutrient availability, indicating its important role in dictating the local responses of the calcifying primary producer H. opuntia to ocean acidification.