Degradation of dissolved complex polysaccharides in estuarine littoral zones

河口复杂溶解性有机物（DOM）的降解在海岸带和海洋碳循环中起着重要作用。DOM是化学和结构多样性和大部分由多糖，都是在河口（如河口硅藻的分泌物）和进口从其他系统（从河流或海洋沉积）。鲜为人知的是，这些溶解的碳水化合物成分的确切性质，特别是在河口碳循环的作用和命运，这件事。高分子量的碳水化合物聚合物可以从河口输出，或者在被细菌同化之前被微生物胞外酶分解。碳水化合物在暴露于紫外线辐射期间也可经历光降解。整个潮间带的环境条件变化很大，随着环境压力（温度、盐度、干燥、紫外线辐射）向盐沼上部地区的增加。我们只有有限的知识，在微生物群落的变化，有机物降解，碳水化合物动力学和酶活性在这个环境梯度。该提案旨在调查在不断增加的环境压力下，潮间带水和沉积物中微生物群落组成与有机物降解的关系。我们提出了一个组合的方法，在一个典型的河口中部潮间带站点的实地调查工作在该项目的第一年，和实验室实验中使用完整的沉积物芯在潮汐围隔和沉积物泥浆的富集-降解实验在第一和第二年。调查工作和实验室实验的结果将构成最后一年一系列实地实验设计的基础。我们将采用从生物化学到分子生物学的一系列技术，目的是确定负责有机物降解的微生物群落的关键成员沿着潮间带梯度。我们将研究这些细菌如何受到系统中主要环境压力（温度，盐度，干燥和紫外线）的影响，以及生理适应如何使它们在极端条件下生存（例如“特殊”胞外酶）。本计画将阐明有机质连续分解过程中碳水化合物组分在结构和单糖组成上的变化。在这方面，将参照有机物质的生物降解和生物利用率评估光解作用。这一研究项目的结果将使研究温带和热带沿海系统底栖-中上层耦合和碳通量的科学家受益。生态系统对环境压力的反应越来越重要，在今后50年内，沿海海洋系统可能会受到越来越多的干扰，社会人口结构发生变化，沿海资源和气候变化的压力。

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.