Changes in the terrestrial environment and their effect on marine carbonates

与沿海开发相关的陆地径流增加导致浅海水中悬浮的细颗粒堵塞了珊瑚骨骼的毛孔，减少了到达珊瑚礁的阳光量。与径流相关的过量营养物质对珊瑚礁也是有害的，因为它们对珊瑚宿主与其光合共生体之间的关系产生负面影响。淤积和营养物质增加对珊瑚礁的直接影响是相当清楚的；然而，很少有研究检查增强风化的长期影响或非珊瑚礁环境中产生碳酸盐的生物群如何受到这些压力源的影响。这项研究计划的总体目标是通过一系列的时间尺度来评估陆地径流和相关营养物质在各种海洋环境中的影响。本研究计划主要关注两个主要目标：1)地球上第一批森林和土壤对泥盆纪（弗拉斯纪- 380 Ma）珊瑚礁的影响；2)径流对现代非珊瑚礁环境的影响。弗拉斯尼亚森林的扩张和根系网络的发展，被称为点状树事件（pE），产生了世界上第一批土壤。据推测，这一事件对世界海洋中产生碳酸盐的生物群产生了影响，因为现代珊瑚礁受到土壤径流增加的影响；然而，这一事件对弗拉斯尼亚珊瑚礁的影响尚未被探索。拟议的研究考察了pE对加拿大西部沉积盆地保存完好的古代珊瑚礁的影响。该研究还将涉及海洋页岩中生物来源的二氧化硅的相关性，这可能代表了古代浮游植物的大量繁殖，与pE同时期，并负责当时在全球范围内观察到的底层水缺氧加剧。本研究计划的第二个方面调查了两个现代环境中陆地径流、相关营养物质和重金属对产生碳酸盐的生物群的影响：大开曼群岛的一个泻湖和阿布扎比的一个内部碳酸盐斜坡。最近的沉积记录（<1000年）将被询问有孔虫和沉积物地球化学。有孔虫对营养水平的变化很敏感，与珊瑚类似，较大的共生有孔虫被一般的分类群所取代。这些多面手分类群也与沉积物中的金属正相关。这项研究的最终目标是确定沿发达海岸线增加的径流如何影响非珊瑚礁环境中产生碳酸盐的海洋生物群，并制定可能帮助我们认识古代环境中营养作用的标准。

Increased terrestrial runoff associated with coastal development results in fine particles suspended in shallow marine waters, which clogs pores in coral skeletons and reduces the amount of sunlight reaching the reefs. Excess nutrients associated with runoff are also harmful to reefs because they have negative impacts on the relationship between coral hosts and their photosynthetic symbionts. The immediate impacts of siltation and enhanced nutrients on reefs are fairly well understood; however, there are few studies examining the long-term effects of enhanced weathering or how carbonate producing biota in non-reef environments may be affected by these stressors. The overall objective of this research program is to evaluate the effects of terrestrial runoff and associated nutrients in various marine environments and through a range of timescales. This research proposal focuses on two main objectives that examine: 1) the effect the Earth's first forests and soils had on Devonian (Frasnian - 380 Ma) reefs; and 2) the effects of runoff in modern non-reef environments. The Frasnian expansion of forests and development of root networks, known as the punctata Event (pE), resulted in the world's first soils. It is assumed that this event had an effect on carbonate producing biota in the world's oceans since modern reefs suffer from increased soil runoff; however, the effects of this event on Frasnian reefs has not been explored. The proposed research examines the impact of the pE on ancient reefs that are well-preserved in the Western Canadian Sedimentary Basin. The research will also entail correlation of biogenically-sourced silicas in marine shales, which may represent ancient phytoplankton blooms, coeval with the pE, and responsible for enhanced bottom water anoxia observed worldwide at this time. The second aspect of this research proposal investigates the impact of terrestrial runoff, associated nutrients, and heavy metals on carbonate-producing biota in two modern settings: a lagoon in Grand Cayman and across an inner carbonate ramp in Abu Dhabi. The recent sedimentary record (<1000 years) will be interrogated for foraminifera and sediment geochemistry. Foraminifera are sensitive to changes in nutrient levels where, comparable to corals, larger symbiont-bearing foraminifera are replaced by generalist taxa. These generalist taxa also positively correlate with metals in sediments. The ultimate goal of this research is to determine how increased runoff along developed coastlines has impacted carbonate-producing marine biota in non-reef environments and develop criteria that may help us to recognize the effects of nutrification in ancient environments.