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Degradation of dissolved complex polysaccharides in estuarine littoral zones

河口沿岸地区溶解的复合多糖的降解

基本信息

批准号：
NE/D003598/1
负责人：
Graham Underwood
金额：
$ 34.04万
依托单位：
University of Essex
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FD003598%2F1
关键词：
Degradation dissolved complex polysaccharides estuarine

项目摘要

Degradation of complex dissolved organic matter (DOM) in estuaries plays an important role in coastal and oceanic carbon cycling. DOM is chemically and structurally diverse and a large fraction consists of polysaccharides that are both produced within the estuary (e.g. exudates of estuarine diatoms) and imported from other systems (deposition from the river or sea). Little is known about the precise nature of these dissolved carbohydrate components and in particular the role and fate of this matter in estuarine carbon cycling. High molecular weight carbohydrate polymers can be exported from the estuary or broken down by microbial extracellular enzymes before being assimilated by bacteria. Carbohydrates may also undergo photodegradation during exposure to ultraviolet radiation. Environmental conditions across the intertidal zone are highly variable with increasing environmental stress (temperature, salinity, desiccation, ultraviolet radiation) towards to the upper saltmarsh area. We have only limited knowledge about the changes in microbial communities, organic matter degradation, carbohydrate dynamics and enzymatic activities across this environmental gradient. This proposal sets out to investigate shifts in microbial community composition across the intertidal zone, in both water and sediments, in relation to organic matter degradation under increasing environmental stresses. We propose a combined approach of field survey work at a typical mid estuary intertidal site in the first year of the project, and laboratory experiments using both intact sediment cores in tidal mesocosms and sediment slurry enrichment-degradation experiments in the first and second year. The findings from survey work and laboratory experiments will form the basis for the design of a series of final year field experiments. We will employ a range of techniques from biochemical to molecular, with the aim of identifying the key members of the microbial community responsible for organic matter degradation along the intertidal gradient. We will investigate how these bacteria are affected by the main environmental stresses in the system (temperature, salinity, desiccation and ultraviolet light) and how physiological adaptations allow their survival in extreme conditions (e.g. 'special' extracellular enzymes). This project will elucidate changes in carbohydrate fractions in both structure and monosaccharide composition during sequential organic matter breakdown. In this context the role of photolysis will be assessed with reference to biodegradation and biavailability of organic matter. The results of this research project will benefit scientists investigating benthic-pelagic coupling and carbon fluxes in both temperate and tropical coastal systems. Responses of ecosystems to environmental stresses are increasingly important, with increasing perturbations to coastal marine systems likely over the next 50 years, with demographic changes in society, pressure of coastal resources and climate change.

河口复杂溶解有机物(DOM)的降解在海岸和海洋碳循环中起着重要作用。DOM在化学和结构上是多样化的，其中很大一部分是由河口产生的多糖(例如河口硅藻的渗出物)和从其他系统进口的(来自河流或海洋的沉积)的多糖组成。关于这些溶解碳水化合物成分的确切性质，特别是这种物质在河口碳循环中的作用和命运，人们知之甚少。高分子碳水化合物聚合物可从河口输出，或在被细菌同化之前被微生物胞外酶分解。在紫外线照射下，碳水化合物也可能发生光降解。潮间带的环境条件随着环境压力(温度、盐度、干燥、紫外线辐射)的增加而变化很大，向上盐沼地区发展。我们对微生物群落、有机物降解、碳水化合物动态和酶活性在这种环境梯度上的变化知之甚少。这项建议旨在调查水和沉积物中跨潮间带微生物群落组成的变化与日益增加的环境压力下有机物降解的关系。我们提出了一种在项目第一年在典型的河口中潮间带站点进行现场调查工作，并在第一年和第二年利用潮汐中层完整沉积物岩心进行实验室实验和沉积物泥浆浓缩-降解实验相结合的方法。调查工作和实验室实验的结果将成为设计一系列最后一年现场实验的基础。我们将采用从生化到分子的一系列技术，目的是确定沿潮间带有机物降解的微生物群落的关键成员。我们将研究这些细菌如何受到系统中主要环境应激(温度、盐度、干燥和紫外线)的影响，以及生理适应如何允许它们在极端条件下生存(例如“特殊的”胞外酶)。这个项目将阐明在有机质顺序分解过程中碳水化合物组分的结构和单糖组成的变化。在这方面，将参照有机物的生物降解和双效性来评估光解的作用。这一研究项目的结果将有助于科学家研究温带和热带沿海系统的底-上层耦合和碳通量。生态系统对环境压力的反应越来越重要，未来50年，随着社会人口结构的变化、沿海资源的压力和气候变化，沿海海洋系统可能受到越来越多的扰动。