Long-term effects of nutrient and CO2 enrichment on the temperate coral Astrangia poculata (Ellis and Solander, 1786)
Long-term effects of nutrient and CO2 enrichment on the temperate coral Astrangia poculata (Ellis and Solander, 1786)
Date
2010-01-15
Authors
Holcomb, Michael
McCorkle, Daniel C.
Cohen, Anne L.
McCorkle, Daniel C.
Cohen, Anne L.
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Abstract
Zooxanthellate colonies of the scleractinian coral Astrangia poculata were grown
under combinations of ambient and elevated nutrients (5 μM NO3 -, 0.3 μM PO4
-3, and 2 nM Fe+2) and CO2 (~780 ppmv) treatments for a period of 6 months. Coral calcification
rates, estimated from buoyant weights, were not significantly affected by moderately
elevated nutrients at ambient CO2 and were negatively affected by elevated CO2 at
ambient nutrient levels. However, calcification by corals reared under elevated
nutrients combined with elevated CO2 was not significantly different from that of corals
reared under ambient conditions, suggesting that CO2 enrichment can lead to nutrient
limitation in zooxanthellate corals. A conceptual model is proposed to explain how
nutrients and CO2 interact to control zooxanthellate coral calcification. Nutrient limited
corals are unable to utilize an increase in dissolved inorganic carbon (DIC) as nutrients
are already limiting growth, thus the effect of elevated CO2 on saturation state drives the
calcification response. Under nutrient replete conditions, corals may have the ability to
utilize more DIC, thus the calcification response to CO2 becomes the product of a
negative effect on saturation state and a positive effect on gross carbon fixation,
depending upon which dominates, the calcification response can be either positive or
negative. This may help explain how the range of coral responses found in different
studies of ocean acidification can be obtained.
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Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Experimental Marine Biology and Ecology 386 (2010): 27-33, doi:10.1016/j.jembe.2010.02.007.