Cornwall Christopher E, Hepburn Christopher D, Pritchard Daniel, Currie Kim I, McGraw Christina M, Hunter Keith A, Hurd Catriona L
Department of Botany, University of Otago, PO Box 56, Dunedin 9054, New ZealandDepartment of Marine Sciences, University of Otago, PO Box 56, Dunedin 9054, New ZealandDepartment of Botany, University of Otago, PO Box 56, Dunedin 9054, New ZealandNational Institute for Water and Atmospheric Research Ltd., Centre of Excellence for Chemical and Physical Oceanography, Department of Chemistry, University of Otago, PO Box 56, Dunedin 9054, New ZealandDepartment of Chemistry, University of Otago, PO Box 56, Dunedin 9054, New ZealandDepartment of Botany, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
J Phycol. 2012 Feb;48(1):137-44. doi: 10.1111/j.1529-8817.2011.01085.x. Epub 2011 Dec 2.
Ocean acidification (OA) is a reduction in oceanic pH due to increased absorption of anthropogenically produced CO2 . This change alters the seawater concentrations of inorganic carbon species that are utilized by macroalgae for photosynthesis and calcification: CO2 and HCO3 (-) increase; CO3 (2-) decreases. Two common methods of experimentally reducing seawater pH differentially alter other aspects of carbonate chemistry: the addition of CO2 gas mimics changes predicted due to OA, while the addition of HCl results in a comparatively lower [HCO3 (-) ]. We measured the short-term photosynthetic responses of five macroalgal species with various carbon-use strategies in one of three seawater pH treatments: pH 7.5 lowered by bubbling CO2 gas, pH 7.5 lowered by HCl, and ambient pH 7.9. There was no difference in photosynthetic rates between the CO2 , HCl, or pH 7.9 treatments for any of the species examined. However, the ability of macroalgae to raise the pH of the surrounding seawater through carbon uptake was greatest in the pH 7.5 treatments. Modeling of pH change due to carbon assimilation indicated that macroalgal species that could utilize HCO3 (-) increased their use of CO2 in the pH 7.5 treatments compared to pH 7.9 treatments. Species only capable of using CO2 did so exclusively in all treatments. Although CO2 is not likely to be limiting for photosynthesis for the macroalgal species examined, the diffusive uptake of CO2 is less energetically expensive than active HCO3 (-) uptake, and so HCO3 (-) -using macroalgae may benefit in future seawater with elevated CO2 .
海洋酸化（OA）是指由于人为产生的二氧化碳吸收增加导致海洋pH值降低。这种变化改变了大型藻类用于光合作用和钙化的无机碳物种的海水浓度：二氧化碳和碳酸氢根离子（HCO₃⁻）增加；碳酸根离子（CO₃²⁻）减少。实验性降低海水pH值的两种常见方法会不同程度地改变碳酸盐化学的其他方面：添加二氧化碳气体模拟了由于海洋酸化预测的变化，而添加盐酸会导致相对较低的[HCO₃⁻]。我们在三种海水pH处理之一中测量了具有不同碳利用策略的五种大型藻类物种的短期光合响应：通过鼓泡二氧化碳气体将pH值降至7.5，通过盐酸将pH值降至7.5，以及环境pH值7.9。在所研究的任何物种中，二氧化碳、盐酸或pH 7.9处理之间的光合速率没有差异。然而，在pH 7.5处理中，大型藻类通过碳吸收提高周围海水pH值的能力最强。对由于碳同化导致的pH变化进行建模表明，与pH 7.9处理相比，在pH 7.5处理中能够利用HCO₃⁻的大型藻类物种增加了对二氧化碳的利用。仅能利用二氧化碳的物种在所有处理中都只使用二氧化碳。尽管对于所研究的大型藻类物种来说，二氧化碳不太可能限制光合作用，但二氧化碳的扩散吸收在能量上比主动吸收HCO₃⁻成本更低，因此在未来二氧化碳浓度升高的海水中，利用HCO₃⁻的大型藻类可能会受益。
