Impact details: decline in calcifying organisms

impact chain for tropical coastal areas / acidification (click nodes to view details):
selected case study results:
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Case study recommendations
Koch, M., Bowes, G., Ross, C., & Zhang, X. (2013). Climate change and ocean acidification effects on seagrasses and marine macroalgae. Global change biology, 19(1), 103-132. Global Calcareous macroalgae and crustose coralline algae deposit calcium carbonate during growth and can thus contribute to reef structural strength. Relevant to calcifiers, elevated C02 lowers net calcification and this effect is amplified by high temperature. It influences fluxes that control the micro-environments promoting calcification over dissolution. Calcareous macroalgae are highly vulnerable to OA, and it is likely that fleshy macroalgae will dominate in a higher C02 ocean. A better understanding of the stress-response mechanisms is needed. Furthermore, the bio-geographical surveys of important species should be ongoing to document range shifts of economically and ecologically critical macro-autotroph species.

Price, N. N., Hamilton, S. L., Tootell, J. S., & Smith, J. E. (2011). Species-specific consequences of ocean acidification for the calcareous tropical green algae Halimeda. Marine Ecology Progress Series, 440, 67-78. Global The common coral reef macroalgal genera Halimeda is highly susceptible to reduced pH and aragonite saturation state. Species of Halimeda produce a large proportion of the sand in the tropics and are a major contributor to framework development on reefs because of their rapid calcium carbonate production and high turnover rates.
H. opuntia suffered net dissolution and 15% reduction in photosynthetic capacity, while H. taenicola did not calcify but did not alter photophysiology in experimental treatments. The disparate responses of these species to elevated CO2 partial pressure (pCO2) may be due to anatomical and physiological differences and could represent a shift in their relative dominance in the face of ocean acidification. The ability for a species to exert biological control over calcification and the species specific role of the carbonate skeleton may have important implications for the potential effects of acidification on ecological functions in the future.
Little evidence exists to date regarding the potential biological consequences of ocean acidification for different species of Halimeda. There is an urgent need to conduct field experiments that harness the naturally varying carbonate chemistry across coral reefs to study the long-term response of coral reef organisms to change in the dissolved inorganic carbon.

Guinotte, J. M., & Fabry, V. J. (2008). Ocean acidification and its potential effects on marine ecosystems. Annals of the New York Academy of Sciences, 1134(1), 320-342. Global Experiments exposing Crustose coralline algae (CCA) to elevated pCO2 (2 x present day) indicate up to a 40% reduction in growth rates, 78% decrease in recruitment, 92% reduction in total area covered by CCA, and a 52% increase in non-calcifying algae. Future ocean acidification research needs include increased resources and efforts devoted to lab, mesocosm, and in situ experiments, all of which will aid in determining the biological responses of marine taxa to increased pCO2.

Hikami, M., Ushie, H., Irie, T., Fujita, K., Kuroyanagi, A., Sakai, K., Nojiri, Y., Suzuki, A., Kawahata, H. (2011). Contrasting calcification responses to ocean acidification between two reef foraminifers harboring different algal symbionts. Geophysical Research Letters, 38(19), L19601 Global In a culture experiment with two algal symbiont-bearing, reef-dwelling foraminifers, Amphisorus kudakajimensis and Calcarina gaudichaudii, in seawater under five different pCO2 conditions, 245, 375, 588, 763 and 907 atm, maintained with a precise pCO2-controlling technique, net calcification of A. kudakajimensis was reduced under higher pCO2, whereas calcification of C. gaudichaudii generally increased with increased pCO2. In another culture experiment conducted in seawater in which bicarbonate ion concentrations were varied under a constant carbonate ion concentration, calcification was not significantly different between treatments in Amphisorus hemprichii, a species closely related to A. kudakajimensis, or in C. gaudichaudii. The opposite responses of these two foraminifer genera probably reflect different sensitivities to these carbonate species, which may be due to their different symbiotic algae. -

Jokiel, P., Rodgers, K., Kuffner, I., Andersson, A., Cox, E., & Mackenzie, F. (2008). Ocean acidification and calcifying reef organisms: a mesocosm investigation. Coral Reefs, 27(3), 473-483. Pacific / Pacific Islands: Hawaii Acidification had a profound impact on the development and growth of crustose coralline algae (CCA) populations. During experiments of this study, CCA developed 25% cover in the control mesocosms and only 4% in the acidified mesocosms, representing an 86% relative reduction. Free-living associations of CCA known as rhodoliths living in the control mesocosms grew at a rate of 0.6 g buoyant weight year(-1) while those in the acidified experimental treatment decreased in weight at a rate of 0.9 g buoyant weight year(-1), representing a 250% difference. -

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