OPUS: CRS Synthesis to add dissolved organic matter to the trophic paradigm: the importance of water transparency in structuring pelagic ecosystems

高透明度的水为湖泊生态系统及其提供的服务增加了经济、娱乐和其他价值。然而，全世界的湖泊都面临着清澈度下降的威胁，这不仅是因为营养物投入增加和随后的藻类生长，而且还因为溶解有机物投入增加。 在有机物分解过程中产生的一些化合物，主要是死亡的植物材料，溶解在水中，使湖水变成棕色。 这个过程类似于浸泡茶包如何使一杯清澈的热水变色。 降雨量的增加在一些地区尤为明显，这增加了溶解有机物从周围土地流入湖泊的流量，大大降低了水的透明度和质量。 溶解的有机物强烈地并有选择地吸收紫外线辐射，否则紫外线辐射将通过杀死有害的人类和野生动物病原体来消毒表面沃茨。 溶解的有机物也会吸收光合作用所需的光波，而光合作用是湖泊深层沃茨中氧气的唯一来源。因此，水的透明度降低会导致水质下降，导致病原体在地表沃茨中生存的风险增加，以及更深沃茨中氧气的耗尽，从而导致像伊利湖和墨西哥湾那样的“死区”。通过对几十年来监测的400多个湖泊的数据进行综合分析，该项目将为溶解有机物如何影响水透明度的长期变化以及对湖泊生态系统的影响提供新的见解。 溶解有机物的影响将被纳入传统的水清澈度范例，以便模型能够更准确地预测溶解有机物投入对湖泊生态系统及其提供的服务的未来后果。这项研究的成果将是：（1）一个独特的，全面的，充分注释的，公开的湖泊数据库，（2）一套综合论文，将溶解有机物（DOM）和紫外线整合到湖泊生态系统模型中，（3）一个更广泛的概念模型，用于研究和教育目的，（4）教育和公共宣传，面向不同的受众，包括大学生，湖泊协会成员、湖泊管理者和决策者。几十年来，营养物质和叶绿素之间的密切关系以及湖泊生产力沿着单一轴的湖泊分类一直是湖泊生态学中最核心的范式。然而，近几十年来湖泊的主要变化之一是DOM增加了一倍或更多，导致北美、欧洲和其他地区许多内陆沃茨的布朗宁。最近极端降水（干旱到洪水）的增加，以及相关的湖泊布朗宁，需要扩展传统的范例，包括DOM和湖泊的光学特性。该项目将综合现有的关于紫外线辐射、光学特性和全世界数百个湖泊的相关湖沼学调查和实验数据以及一组三个核心研究湖泊的地理范围最广、地点最密集的数据库。 综合将增加一个新的层面，目前的湖泊营养范式。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Water of higher clarity adds economic, recreational, and other value to lake ecosystems and the services they provide. Yet, lakes worldwide are threatened with decreasing clarity due not only to increased nutrient inputs and subsequent algal growth, but also due to increased dissolved organic matter inputs. Some of the compounds produced during the decomposition of organic matter, which is primarily dead plant material, dissolve in water and turn lake water brown. This process is similar to how a steeping tea bag discolors a clear cup of hot water. Increases in rainfall, which are pronounced in some areas, are increasing the flow of dissolved organic matter into lakes from surrounding land, significantly decreasing water clarity and quality. Dissolved organic matter strongly and selectively absorbs ultraviolet radiation, which would otherwise disinfect surface waters by killing harmful human and wildlife pathogens. Dissolved organic matter also absorbs wavelengths of light that are used by photosynthesis, which is the only source of oxygen in the deep waters of lakes. Decreasing water clarity thus results in the degradation of water quality, a greater risk of pathogen survival in surface waters, and depletion of the oxygen in deeper waters, leading to “dead zones” like those in Lake Erie and the Gulf of Mexico. Through a synthesis of data from over 400 lakes that have been monitored over multiple decades, this project will provide new insights into how dissolved organic matter influences long-term changes in water clarity, and the resulting consequences for lake ecosystems. The effects of dissolved organic matter will be integrated into the conventional paradigm for water clarity, so that models can more accurately predict future consequences of dissolved organic matter inputs for lake ecosystems and the services they provide. The products of this research will be: (1) a unique, comprehensive, fully annotated, and publicly available lake database, (2) a suite of synthesis papers that integrate dissolved organic matter (DOM) and UV into a lake ecosystem model, (3) a broader conceptual model for research and educational purposes, and (4) educational and public outreach for diverse audiences, including undergraduates, lake association members, lake managers, and policymakers.The strong relationship between nutrients and chlorophyll and the classification of lakes along a single axis of lake productivity has been the most central paradigm in lake ecology for decades. However, one of the major changes in lakes in recent decades is up to a doubling or more of DOM, leading to browning of many inland waters in North America, Europe, and beyond. Recent increases in precipitation extremes (drought to flood), and associated browning of lakes, require extension of the traditional paradigm to include DOM and the optical properties of lakes. This project will synthesize the most geographically extensive and site intensive database in existence on ultraviolet radiation (UV), optical properties, and associated limnological survey and experimental data on hundreds of lakes worldwide, and a set of three core study lakes. The synthesis will add a new dimension to the current trophic paradigm for lakes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.