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

0110875Michael Gretz Graham Underwood硅藻是全球环境中最重要的初级生产者之一。这些单细胞藻类非常丰富，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，而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都依赖于海洋食物链。海洋占据了我们星球的大约70%，海洋微藻，其中硅藻是主要成分，对今天的大气化学（它们是地球上主要的氧气生产者）以及碳和其他元素的地球化学循环产生了强大的影响。过去数亿年的藻类生长为我们现代社会所依赖的重要石油矿床做出了贡献。硅藻，无论是在有机体本身和它们分泌的物质方面，对整个水生生态都具有根本的重要性。硅藻固定的大部分碳以胞外聚合物的形式分泌。这些外聚合物（EPS）强烈影响生态系统中的地球化学循环，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很重要。这项研究将描述底栖硅藻在各种环境条件下（营养限制、有害辐照水平、盐度胁迫）产生的硅藻EPS的生产率、组成和特征。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特征将与河口硅藻生物膜内微环境的变化，以及生物体对重要环境胁迫的响应相关。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潮间带生物膜内EPS的作用。这项工作将大大推进我们的知识EPS和生理条件的性质，触发生产不同类型的，并可能导致在稳定沉积物或确定新的聚合物的商业利益的进步。此外，该项目将通过让学生参与多学科的努力，包括美国和英国实验室之间的综合国际合作，为学生培训做出宝贵的贡献。

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.