造礁珊瑚碳、氮、硼同位素的海洋酸化指示意义

Isotopes of Carbon, Nitrogen, Boron in Reef Coral as Proxies of Ocean Acidification

大气CO_2体积分数升高导致的海洋酸化不仅会降低海水p H,还会改变其碳酸盐平衡体系,使得海水中文石饱和度(Ω)降低,相应地会降低珊瑚钙化的速率。已有研究表明:珊瑚骨骼δ^(11)3C、δ^(11)B和δ^(15)N具有记录Suess Effect、生物生产力、海水p H值以及营养源的能力;主要表现为:δ^(11)B记录的p H值、δ^(11)3C记录的海水无机碳库(DIC)δ^(11)3C和生物生产力,以及δ^(15)N记录的陆源物质输送量相结合,可用来指示受季风影响的南海"大陆架碳泵"和近海污染与海洋酸化的联系。目前关于珊瑚对海洋酸化的记录研究仍相对较少,珊瑚碳-氮-硼同位素组合的应用将会加深对于海洋酸化与气候变率和全球碳、氮循环的关系的认识,可能成为揭示海水p H值变化规律性的重要手段。

Ocean acidification, caused by the increasing atmospheric CO_2 levels, has not only decreased seawater p H, but also changed the carbonate equilibrium so that the aragonite saturation state has decreased, which has lead to the decrease of calcification rates. Researches show that δ^（13）C, δ^（11）B and^（δ15）N of the coral skeleton have the capacity of recording Suess Effect, productivity, seawater p H and nutrient source. The main characteristics are： its δ^（11）B records seawater p H, δ^（13）C records sea water dissolved inorganic carbon（DIC） δ^（13）C and productivity, and δ^（15）N records terrestrial input. The combination of those proxies can indicate ＂the shelf carbon pumping＂ of the South China Sea and the coastal pollution effects on ocean acidification. However, researches on records of ocean acidification in coral reefs are insufficient, our understanding of ocean acidification, climate variability and global carbon, nitrogen cycle can be deepened by the application of such combination, which may be an important tool of revealing sea water p H change regularity.