Is the response of coral calcification to seawater acidification related to nutrient loading?
- 779 Downloads
The effect of decreasing aragonite saturation state (ΩArag) of seawater (elevated pCO2) on calcification rates of Acropora muricata was studied using nubbins prepared from parent colonies located at two sites of La Saline reef (La Réunion Island, western Indian Ocean): a back-reef site (BR) affected by nutrient-enriched groundwater discharge (mainly nitrate), and a reef flat site (RF) with low terrigenous inputs. Protein and chlorophyll a content of the nubbins, as well as zooxanthellae abundance, were lower at RF than BR. Nubbins were incubated at ~27°C over 2 h under sunlight, in filtered seawater manipulated to get differing initial pCO2 (1,440–340 μatm), ΩArag (1.4–4.0), and dissolved inorganic carbon (DIC) concentrations (2,100–1,850 μmol kg−1). Increasing DIC concentrations at constant total alkalinity (AT) resulted in a decrease in ΩArag and an increase in pCO2. AT at the beginning of the incubations was kept at a natural level of 2,193 ± 6 μmol kg−1 (mean ± SD). Net photosynthesis (NP) and calcification were calculated from changes in pH and AT during the incubations. Calcification decrease in response to doubling pCO2 relative to preindustrial level was 22% for RF nubbins. When normalized to surface area of the nubbins, (1) NP and calcification were higher at BR than RF, (2) NP increased in high pCO2 treatments at BR compared to low pCO2 treatments, and (3) calcification was not related to ΩArag at BR. When normalized to NP, calcification was linearly related to ΩArag at both sites, and the slopes of the relationships were not significantly different. The increase in NP at BR in the high pCO2 treatments may have increased calcification and thus masked the negative effect of low ΩArag on calcification. Removing the effect of NP variations at BR showed that calcification declined in a similar manner with decreased ΩArag (increased pCO2) whatever the nutrient loading.
KeywordsCalcification Coral Aragonite saturation state Acidification Nutrient enrichment Acropora muricata
The authors would like to thank Amandine Pierre and Marjorie Sawadogo for laboratory assistance, Kévin Coustaut for help with iconography and Karyne Rogers for English corrections. This research was made possible through the financial support of the Conseil Régional de La Réunion (ITUE program) and performed under collecting permit number 94/DRAM/09. The manuscript was greatly improved with help from the topic editor Mark Warner and two anonymous reviewers.
- Atkinson MJ, Carlson B, Crow GL (1995) Coral growth in high-nutrient, low-pH seawater: a case study of corals cultured at the Waikiki Aquarium, Honolulu, Hawaii. Coral Reefs 14:215–223Google Scholar
- Cordier E (2007) Dynamique hydrosédimentaire du récif frangeant de l’Hermitage/La Saline (La Réunion): processus physiques et flux sédimentaires. Ph.D. thesis, Université de La Réunion, p 193Google Scholar
- Cuet P, Naim O, Faure G, Conan JY (1988) Nutrient-rich groundwater impact on benthic communities of La Saline fringing reef (Reunion Island, Indian Ocean): preliminary results. Proc 6th Int Coral Reef Symp 2:207–212Google Scholar
- Eakin CM, Kleypas J, Hoegh-Guldberg O (2008) Global climate change and coral reefs: rising temperatures, acidification and the need for resilient reefs. In: Wilkinson C (ed) Status of coral reefs of the world: 2008. Global Coral Reef Monitoring Network and Reef and Rainforest Research Centre, Townsville, Australia, pp 29–34Google Scholar
- Edmunds P, Gates R (2002) Normalizing physiological data for scleractinian corals. Coral Reefs 21:193–197Google Scholar
- Gattuso J, Allemand D, Frankignoulle M (1999) Photosynthesis and calcification at cellular, organismal and community levels in coral reefs: a review on interactions and control by carbonate chemistry. Am Zool 39:160–183Google Scholar
- Hoegh-Guldberg O, Mumby PJ, Hooten AJ, Steneck RS, Greenfield P, Gomez E, Harvell CD, Sale PF, Edwards AJ, Caldeira K, Knowlton N, Eakin CM, Iglesias-Prieto R, Muthiga N, Bradbury RH, Dubi A, Hatziolos ME (2007) Coral reefs under rapid climate change and ocean acidification. Science 318:1737–1742PubMedCrossRefGoogle Scholar
- Jeffrey SW, Humphrey GF (1975) New spectrophotometric equations for determining chlorophylls a, b, c 1 and c 2 in algae, phytoplankton and higher plants. Biochem Physiol Pflanz 167:191–194Google Scholar
- Kleypas JA, Langdon C (2006) Coral reefs and changing seawater carbonate chemistry. In: Phinney JT, Hoegh-Guldberg O, Kleypas JA, Skirving W, Strong A (eds) Coral reefs and climate change: science and management. Coast Estuar Sci 61:73–110Google Scholar
- Langdon C, Atkinson MJ (2005) Effect of elevated pCO2 on photosynthesis and calcification of corals and interactions with seasonal change in temperature/irradiance and nutrient enrichment. J Geophys Res 110, C09S07. doi: 10.1029/2004JC002576
- Lewis E, Wallace DWR (1998) Program developed for CO2 system calculations, ORNL/CDIAC-105. Carbon Dioxide Information and Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennesee. Available at: http://cdiac.esd.ornl.gov/oceans/co2rprt.html
- Naim O, Cuet P, Mangar V (2000) The Mascarene Islands. In: McClanahan TR, Sheppard CRC, Obura DO (eds) Coral reefs of the Indian Ocean: their ecology and conservation. University Press, Oxford, pp 353–381Google Scholar
- Orr JC, Fabry VJ, Aumont O, Bopp L, Doney SC, Feely RA, Gnanadesikan A, Gruber N, Ishida A, Joos F, Key RM, Lindsay K, Maier-Reimer E, Matear R, Monfray P, Mouchet A, Najjar RG, Plattner G, Rodgers KB, Sabine CL, Sarmiento JL, Schlitzer R, Slater RD, Totterdell IJ, Weirig M, Yamanaka Y, Yool A (2005) Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms. Nature 437:681–686PubMedCrossRefGoogle Scholar
- Stambler N, Popper N, Dubinsky Z, Stimson J (1991) Effects of nutrient enrichment and water motion on the coral Pocillopora damicornis. Pac Sci 45:299–307Google Scholar
- Wallace CC (1999) Staghorn corals of the world. A revision of the coral genus Acropora (Scleractinia; Astrocoeniina; Acroporidae) worldwide, with emphasis on morphology, phylogeny and biogeography. CSIRO Publishing, Collingwood, AustraliaGoogle Scholar