Exopolymer Production by Benthic Diatoms: Rhythms, Responses and Acclimation to Environmental Stress

迈克尔·格雷茨和格雷厄姆·安德伍德硅藻是全球环境中最重要的初级生产者之一。这些单细胞藻类极其丰富，是数量最多的水生生物之一。硅藻是海洋食物链基础的主要贡献者，经济上重要的海洋渔业和生态上重要的海洋哺乳动物和鸟类种群依赖于硅藻。海洋约占地球的70%，海洋微藻对当今的大气化学(它们是地球上主要的氧气生产者)以及碳和其他元素的生物地球化学循环产生了强大的影响，其中硅藻是主要成分。过去数亿年的藻类生长为我们的现代社会所依赖的重要石油矿藏做出了贡献。硅藻，无论是就生物体本身而言，还是就其分泌的物质而言，对整个水生生态来说都是至关重要的。硅藻固定的大部分碳是以胞外聚合物的形式分泌的。这些胞外聚合物(EPS)强烈影响生态系统中的生物地球化学循环，因为它们是沉积物碳库的贡献者，在食物链和沉积物的生物稳定中非常重要。本研究将对底栖硅藻在不同环境条件(营养限制、有害光照水平、盐度胁迫)下产生的硅藻EPS的产量、组成和特征进行表征。不同EPS的组成和结构将影响这些分子在环境中发挥的作用。EPS特性将与河口硅藻生物膜内微环境的变化以及生物对重要环境胁迫的反应相关。需要这些信息来确定硅藻如何适应潮间带生物膜内不断变化的条件，并确定产生的不同EPS的性质，这将导致进一步研究EPS在潮间带生物膜中的作用。这项工作将极大地提高我们对EPS和自然界中触发不同类型生产的生理条件的了解，并可能导致在稳定沉积物或识别具有商业价值的新聚合物方面取得进展。此外，该项目将通过让学生参与一项涉及美国和英国实验室之间综合国际合作的多学科努力，为学生培训做出宝贵贡献。

0110875Michael Gretz & Graham UnderwoodThe diatoms are among the most important primary producers in the global environment. These single-cell algae are exceedingly abundant and among the most numerous aquatic organisms. The diatoms are major contributors to the base of the marine food chain, upon which economically important marine fisheries and ecologically significant marine mammal and bird populations are dependent. Oceans occupy approximately 70% of our planet and marine microalgae, of which diatoms are a predominant component, exert a powerful influence on today's atmospheric chemistry (they are the primary oxygen producers on earth) and the biogeochemical cycling of carbon and other elements. Hundreds of millions of years of past algal growth has contributed to the important petroleum deposits upon which our modern society depends. Diatoms, both in terms of the organisms themselves and the material they secrete, are of fundamental importance to overall aquatic ecology. Much of the carbon that diatoms fix is secreted in the form of extracellular polymers. These exopolymeric substances (EPS) strongly influence biogeochemical cycling in ecosystems, as they are contributors to the sediment carbon pool, important in food chains and the biostabilization of sediments. This research will characterize the production rates, composition and characteristics of diatom EPS produced by benthic diatoms under various environmental conditions (nutrient limitation, damaging irradiance levels, salinity stress). The composition and structure of different EPS will influence the role such molecules play in the environment. EPS characteristics will be correlated with the changing microenvironment within estuarine diatom biofilms, and with the response of the organisms to important environmental stresses. This information is required to define how diatoms acclimate to the changing conditions within intertidal biofilms and to determine the nature of the different EPS produced, which will lead to further studies of the role of EPS within intertidal biofilms. This work will greatly advance our knowledge of EPS and the physiological conditions in nature that trigger production of different types and may lead to advances in stabilizing sediments or identifying new polymers of commercial interest. In addition, this project will provide a valuable contribution to student training by engaging students in a multidisciplinary effort that involves integrated international cooperation between laboratories in the U.S. and the U.K.