Fish Carbonates - Their dissolution potential under elevated hydrostatic pressure

海洋-大气碳循环的一个主要组成部分是碳酸钙在海水中的沉淀和溶解。碳酸钙是构成石灰岩和白垩等岩石的矿物。对这一成分的详细了解对我们理解全球碳循环和整个地球系统都很重要。本提案旨在探索最近的发现，这些发现代表了我们对海洋无机碳收支的理解的根本和以前意想不到的变化。在全球海洋中，大量的碳酸钙是由海洋浮游生物产生的，特别是由微生物，如颗石藻和有孔虫产生的。然而，PI最近的研究强调了海洋硬骨鱼对海洋碳酸盐生产的重要额外贡献。这些动物摄取海水，现在已知它们也会在肠道内沉淀碳酸钙，并以很高的速度排出这些碳酸钙，这是它们在海水中的正常功能的一部分。这种以前未被认识到的海洋碳酸盐来源本身是重要的，但是，当结合对全球鱼类生物量的新估计时，很明显，它对全球范围内的碳酸盐生产作出了重大贡献。此外，由于它们的镁含量异常高，预计这些鱼类碳酸盐比其他海洋钙化生物产生的碳酸钙更容易溶解（即更容易在下沉时溶解）。溶解度问题对海洋化学很重要，因为碳酸盐在下沉时迅速溶解在海洋500-1000米的上层，将恢复表层水的碱度和缓冲能力，从而增强海洋从大气中吸收更多二氧化碳的能力。从理论上讲，我们对鱼类碳酸盐的化学知识所知甚少，这表明它们将是这种矿物溶解最快的形式之一。这一提议将是有史以来第一次尝试实际测量下沉（即静水压力）对来自鱼类的碳酸盐溶解潜力的影响。这将有助于解释一个困扰海洋学家几十年的海洋化学之谜，即大西洋和太平洋前1000米深处碱度的意外增加。此外，实验室设置允许将流体流动对骨料的影响纳入其中，确保更真实地模拟下沉，从而获得更准确的模拟结果。

A major component of the marine-atmospheric carbon cycle is the precipitation and dissolution of calcium carbonate in seawater. Calcium carbonate is the mineral that makes up rocks such as limestone and chalk. Detailed knowledge of this component is important to our understanding of the global carbon cycle, and to the Earth system as a whole. This proposal aims to explore recent findings that represent a fundamental and previously unexpected change to our understanding of the marine inorganic carbon budget. Large amounts of calcium carbonate are produced in the global oceans by marine plankton and, specifically, by microscopic organisms such as coccolithophores and foraminifera. However, recent research by the PI has highlighted the significant additional contribution to oceanic carbonate production by marine bony fish. These animals ingest sea water and are now known to also precipitate calcium carbonate within their guts and excrete these at very high rates as part of their normal functioning in seawater. This previously unrecognised source of marine carbonate is significant in its own right but, when combined with new estimates of global fish biomass, it is clear that it makes a major contribution to carbonate production on a global scale. Furthermore, due to their rather unusually high content of magnesium, these fish carbonates are predicted to be more soluble (i.e. more likely to dissolve whilst sinking) than the better know forms of calcium carbonate produced by other marine calcifying organisms. The issue of solubility is important to ocean chemistry, as carbonates that dissolve rapidly upon sinking, in the upper 500-1000 m of the ocean, will restore the alkalinity and buffer capacity of surface waters, which in turn enhances the ocean's capacity to absorb further CO2 from the atmosphere. Theoretically, the little we know about the chemistry of fish carbonates suggests they will be one of the fastest dissolving forms of this mineral. This proposal will be the first ever attempt to actually measure the influence of sinking (i.e. hydrostatic pressure) on the dissolving potential of carbonates derived from fish. This would help explain a mystery of ocean chemistry that has puzzled oceanographers for decades, i.e. the unexpectedly increase in alkalinity in the first 1000 m of depth in the Atlantic and Pacific oceans. In addition, the laboratory setting allows for the incorporation of the effect of fluid flow on the aggregates, ensuring a more realistic simulation of sinking, and consequently more accurate simulation results.