Boron isotope sensitivity to seawater pH change in a species of Neogoniolithon coralline red alga
Boron isotope sensitivity to seawater pH change in a species of Neogoniolithon coralline red alga
复制标题
DOI：
10.1016/j.gca.2017.08.021
复制
发表时间：
2017-11-15
影响因子：
5
通讯作者：
Foster, Gavin L.
中科院分区：
文献类型：
--
作者：
Donald, Hannah K.;Ries, Justin B.;Foster, Gavin L.
自工业革命以来观察到的大气二氧化碳（CO2）的增加使海洋表面的pH值降低了约0.1个pH值单位，预计未来几十年海洋系统将进一步变化。由于海洋碳酸盐系统的相关变化，钙质生物可能受到海水pH值（pH（sw））极端变化的负面影响。生物碳酸盐的硼同位素组成（δ（11）B）以前已被用于监测pH值在钙化网站（pH值（cf））在石珊瑚，珊瑚生物矿化和可变pH值（SW）对这一过程的影响提供了机械的见解。受这些调查的启发，本研究探讨了三角洲（11）B的高镁方解石骨架的珊瑚红珊瑚Neogoniolithon sp.限制pH值（cf），并调查如何此分类群的pH值（cf）是由海洋酸化的影响。在四种不同pCO（2）浓度下培养的多个藻类重复（n = 4-5）中测量δ B-11-平均值（+/- 1 sigma）409（+/- 6）、606（+/- 7）、903（+/- 12）和2856（+/- 54）mu atm，对应于平均pH值（sw）（+/-1 σ）分别为8.19（+/-0.03）、8.05（+/-0.06）、7.91（+/-0.03）和7.49（+/-0.02）。结果表明，在所有pH（sw）处理下，骨骼δ（11）B相对于海水硼酸盐的δ（11）B升高高达18%。尽管在给定pH（sw）下培养的重复样品之间存在Δ（11）B的显著变异性，（最小范围= 2.32%，pH（sw）8.19，最大范围= 6.08%，pH（sw）7.91），δ（11）B和pH（sw）之间存在强相关性（R-2 = 0.72，p < 0.0001，n = 16）和δ（11）B和B/Ca之间（R-2 = 0.72，p < 0.0001，n = 16）。假设骨骼δ（11）B反映了先前在石珊瑚中观察到的pH值（cf），所有实验的平均pH值（cf）比pH值（sw）高1.20个pH单位（0.79至1.56），这种偏移的幅度随着pH值（sw）的降低而呈抛物线变化，pH值（sw）和pH值（cf）之间的最大差异为7.91。观察到的pH值（SW）和钙化率之间的关系，pH值（SW）和pH值（CF），表明珊瑚藻表现出一定的弹性适度的海洋酸化通过增加pH值（CF）相对于pH值（SW）以类似的方式，以石珊瑚。然而，这些结果也表明，pH值（cf）不能通过藻类暴露于pH值（sw）的较大降低而充分增加，从而对珊瑚红藻的钙化率产生不利影响。(C)2017爱思唯尔有限公司版权所有
The increase in atmospheric carbon dioxide (CO2) observed since the industrial revolution has reduced surface ocean pH by similar to 0.1 pH units, with further change in the oceanic system predicted in the coming decades. Calcareous organisms can be negatively affected by extreme changes in seawater pH (pH(sw)) such as this due to the associated changes in the oceanic carbonate system. The boron isotopic composition (delta(11) B) of biogenic carbonates has been previously used to monitor pH at the calcification site (pH(cf)) in scleractinian corals, providing mechanistic insights into coral biomineralisation and the impact of variable pH(sw) on this process. Motivated by these investigations, this study examines the delta(11) B of the high-Mg calcite skeleton of the coralline red alga Neogoniolithon sp. to constrain pH(cf), and investigates how this taxon's pH(cf) is impacted by ocean acidification. delta B-11 was measured in multiple algal replicates (n = 4-5) cultured at four different pCO(2) scenarios-averaging (+/- 1 sigma) 409 (+/- 6), 606 (+/- 7), 903 (+/- 12) and 2856 (+/- 54) mu atm, corresponding to average pH(sw) (+/- 1 sigma) of 8.19 (+/- 0.03), 8.05 (+/- 0.06), 7.91 (+/- 0.03) and 7.49 (+/- 0.02) respectively. Results show that skeletal delta(11) B is elevated relative to the delta(11) B of seawater borate at all pH(sw) treatments by up to 18%. Although substantial variability in delta(11) B exists between replicate samples cultured at a given pH(sw) (smallest range = 2.32% at pHsw 8.19, largest range = 6.08% at pH(sw) 7.91), strong correlations are identified between delta(11) B and pH(sw) (R-2 = 0.72, p < 0.0001, n = 16) and between delta(11) B and B/Ca (R-2 = 0.72, p < 0.0001, n = 16). Assuming that skeletal delta(11) B reflects pH(cf) as previously observed for scleractinian corals, the average pH(cf) across all experiments was 1.20 pH units (0.79 to 1.56) higher than pH(sw), with the magnitude of this offset varying parabolically with decreasing pH(sw), with a maximum difference between pH(sw) and pH(cf) at a pH(sw) of 7.91. Observed relationships between pH(sw) and calcification rate, and between pH(sw) and pH(cf), suggest that coralline algae exhibit some resilience to moderate ocean acidification via increase of pH(cf) relative to pH(sw) in a similar manner to scleractinian corals. However, these results also indicate that pH(cf) cannot be sufficiently increased by algae exposed to a larger reduction in pH(sw), adversely impacting calcification rates of coralline red algae. (C) 2017 Elsevier Ltd. All rights reserved.