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

• Published in: Planta Vol. 239; no. 1; pp. 231 - 242
• Main Authors: Hofmann, Laurie C., Heiden, Jasmin, Bischof, Kai, Teichberg, Mirta
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-01-2014; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Accretion; Acidification; Agriculture; Algae; Biological Availability; Biomedical and Life Sciences; Carbon; Carbon - pharmacokinetics; Carbon Dioxide; Carbon dioxide emissions; Carbonic Anhydrases - metabolism; Chlorophyta - growth & development; Chlorophyta - physiology; Coral Reefs; Ecology; Forestry; Halimeda opuntia; Hydrogen-Ion Concentration; Inorganic carbon; Life Sciences; Nitrate Reductase - metabolism; Nitrates; Nitrogen; Nitrogen - pharmacokinetics; Nutrient availability; Nutrient balance; Nutrient loading; Nutrient status; Nutrients; Ocean acidification; Opuntia; Organic carbon; Organic phosphorus; Original Article; Phosphates; Phosphorus; Phosphorus - pharmacokinetics; Physiological responses; Plant Sciences; Sea water; Seawater - chemistry; Calcification; Carbonic anhydrase; Ocean acidification; Photosynthesis; Nitrate reductase; Eutrophication
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-013-1982-1

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 reducíase, 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 reducíase 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.