Calcification and Photophysiology Responses to Elevated pCO2 in Six Halimeda Species from Contrasting Irradiance Environments on Little Cayman Island Reefs

Authors

Katherine E. Peach, Florida Atlantic University
Marguerite S. Koch, Florida Atlantic University
Patricia Blackwelder, University of MiamiFollow
Carrie Manfrino, Central Caribbean Marine Institute; Little Cayman Research Centre

Document Type

Article

Publication Title

Journal of Experimental Marine Biology and Ecology

ISSN

0022-0981

Publication Date

1-2017

Keywords

Aragonite, Calcification, Halimeda, Irradiance, Ocean acidification, Photosynthesis

Abstract

While elevated pCO₂ associated with ocean acidification has been shown to lower calcification rates in some marine calcifiers, the modulating potential of irradiance is not well studied. Therefore, we examined the interactive effects of irradiance (high and low) and elevated pCO₂ on six species of the macroalgal genus, Halimeda, an ecologically important tropical calcifier. Calcification, growth, and aragonite crystal formation were studied in a 42 d aquaria experiment. Species-specific photophysiology and inorganic C saturation levels were ascertained by establishing photosynthesis to irradiance and inorganic C (C_i) relationships potentially linking photophysiology to growth and calcification responses to elevated pCO₂. Because of Halimeda's role as a sediment producer on tropical reefs, the effect of elevated pCO₂ on dissolution of non-living segments was also examined. Net calcification rates varied among species, with no significant pCO₂ or irradiance effects. However, low irradiance enhanced new apical segment growth in all six species. Crystals formed in new apical segments under elevated pCO₂. Non-living segment mineral:organic content and internal calcium carbonate (CaCO₃) crystal microstructure remained stable over 21 d at elevated pCO₂. Species-specific photosynthetic responses corresponded to irradiance conditions at collection sites. For example, high irradiance-adapted species photosynthetic rates were enhanced under increased availability of C_i. In contrast, low irradiance-adapted species photosynthetic rates were saturated under current C_i levels. While species-specific photosynthetic responses to elevated pCO₂ occurred, these photophysiology shifts did not result in reduced calcification or microstructural alteration of carbonate crystals at pCO₂ levels predicted for the year 2100 in any of the six Halimeda species examined.

DOI

10.1016/j.jembe.2016.09.008

Volume

486

First Page

114

Last Page

126

Comments

©2016 Elsevier B.V. All rights reserved.

Additional Comments

Darwin Plus Initiative grant #: DPLUS010; NSF-FSML grant #: 1227093

NSUWorks Citation

Katherine E. Peach, Marguerite S. Koch, Patricia Blackwelder, and Carrie Manfrino. 2017. Calcification and Photophysiology Responses to Elevated pCO2 in Six Halimeda Species from Contrasting Irradiance Environments on Little Cayman Island Reefs .Journal of Experimental Marine Biology and Ecology : 114 -126. https://nsuworks.nova.edu/occ_facarticles/843.