The production and fate of fish-derived carbonate crystals in tropical shallow marine environments

热带浅海环境中鱼源碳酸盐晶体的产生和归宿

• 批准号: NE/G010617/1
• 负责人: Christopher Perry
• 金额: $ 9.23万
• 依托单位: Manchester Metropolitan University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG010617%2F1
• 关键词: production; fate; fish; derived; carbonate

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 part of the research team here has highlighted the significant additional contribution to oceanic carbonate production by marine bony fish. These all ingest seawater and are now known to also produce calcium carbonate within their guts and excrete these precipitates 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 in particular regions of the ocean, and a smaller but significant contribution globally. Following excretion, these carbonate precipitates sink in the open oceans (along with other pelagic carbonates) and, once they reach the chemical lysoclines for carbonate (the depth at which ocean waters become undersaturated with respect to calcium carbonate), much of this material will dissolve. Thus the likely fate of these crystals in the open oceans is to dissolve at depth. In contrast, the fate of fish-derived precipitates in shallow tropical marine waters, whilst unknown, may be very different. Because fish production of calcium carbonate is positively correlated with seawater temperature, higher marine temperatures in the tropics will result in highest rates of precipitate production by fish. In addition, the shallow warm waters of tropical platform and shelf environments are typically saturated with respect to calcium carbonate, thus allowing substantial carbonate preservation and sediment accumulation to occur. Thus in these settings, with both high production rates and less potential for crystal dissolution, we hypothesise that fish-derived carbonates are making an important, but previously unrecognised, contribution to shallow water tropical carbonate sediment budgets and, especially, to the fine-grained (carbonate mud) fractions that are often volumetrically important in tropical carbonate depositional environments. It is significant to note that where attempts have been made to quantify fine-grained carbonate sediment fraction sources a significant proportion of the mud fraction remains of unknown origin (e.g. between 10 and 40% in Bahamian sediments) but is morphologically distinct from that attributable to any previously considered biogenic or inorganic source. This project will test the hypothesis that fish carbonates make up a substantial portion of this unknown fraction of carbonate mud. We will undertake an assessment of the ultrastructural and elemental characteristics of crystals that are produced by four representative shallow water tropical fish species and determine whether such crystals are contributing to carbonate sediment accumulation in these environments. If this material is indeed accumulating in these environments this would represent a previously unrecognised (and potentially volumetrically important) source for tropical shallow water carbonate sediments.

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。碳酸钙是构成石灰石和白垩等岩石的矿物质。详细了解这一组成部分对于我们理解全球碳循环以及整个地球系统都很重要。该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预算的理解的根本性和以前意想不到的变化。在全球海洋中，海洋浮游生物，特别是颗石藻和有孔虫等微生物产生大量碳酸钙。然而，这里的部分研究小组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。它们都摄取海水，现在已知它们的肠道内也会产生碳酸钙，并以非常高的速度排出这些沉淀物，这是它们在海水中正常运作的一部分。这种以前未被认识到的海洋碳酸盐来源本身就很重要，但是，当与全球鱼类生物量的新估计相结合时，很明显，它对海洋特定区域的碳酸盐生产做出了重大贡献，并且在全球范围内做出了较小但重要的贡献。排泄后，这些碳酸盐沉淀物（与其他远洋碳酸盐一起沿着）沉入开阔海洋，一旦它们到达碳酸盐的化学溶素（海洋沃茨中碳酸钙不饱和的深度），大部分物质将溶解。因此，这些晶体在开阔海洋中的可能命运是在深海溶解。相比之下，热带浅海沃茨中鱼类产生的沉淀物的命运虽然未知，但可能非常不同。由于鱼类产生碳酸钙与海水温度呈正相关，热带海洋温度较高将导致鱼类产生最高的沉淀物。此外，热带台地和大陆架环境的温暖的浅沃茨通常碳酸钙饱和，因此允许大量的碳酸盐保存和沉积物积累。因此，在这些设置中，与高生产率和晶体溶解的可能性较小，我们假设，鱼衍生的碳酸盐是一个重要的，但以前未被认识到，贡献浅水热带碳酸盐沉积物预算，特别是细粒（碳酸盐泥）馏分，往往是体积上重要的热带碳酸盐沉积环境。值得注意的是，在试图量化细粒碳酸盐沉积物组分来源的地方，仍有很大比例的泥组分来源不明（例如，巴哈马沉积物中的10%至40%），但在形态上与任何先前认为的生物或无机来源不同。这个项目将测试的假设，鱼类碳酸盐构成了碳酸盐泥的这一未知部分的相当大的一部分。我们将对四种代表性浅水热带鱼种产生的晶体的超微结构和元素特征进行评估，并确定这些晶体是否有助于这些环境中的碳酸盐沉积物积累。如果这种物质确实在这些环境中积累，这将代表热带浅水碳酸盐沉积物的一个以前未被认识到的（和潜在的体积重要）来源。

项目成果

Phase heterogeneity in carbonate production by marine fish influences their roles in sediment generation and the inorganic carbon cycle.

• DOI: 10.1038/s41598-017-00787-4
• 发表时间: 2017-04-10
• 期刊: Scientific reports
• 影响因子: 4.6
• 作者: Salter MA;Harborne AR;Perry CT;Wilson RW
• 通讯作者: Wilson RW

Production of mud-grade carbonates by marine fish: Crystalline products and their sedimentary significance

海鱼生产泥级碳酸盐：结晶产物及其沉积意义

• DOI: 10.1111/j.1365-3091.2012.01339.x
• 发表时间: 2012
• 期刊: Sedimentology
• 影响因子: 3.5
• 作者: SALTER M

Size fraction analysis of fish-derived carbonates in shallow sub-tropical marine environments and a potentially unrecognised origin for peloidal carbonates

浅亚热带海洋环境中鱼类来源的碳酸盐的尺寸分数分析以及可能未被识别的球状碳酸盐的来源

• DOI: 10.1016/j.sedgeo.2014.10.005
• 发表时间: 2014
• 期刊: Sedimentary Geology
• 影响因子: 2.8
• 作者: Salter M