Collaborative research: Regulation of lake productivity by terrestrial dissolved organic matter

湖泊在经济和文化上都是景观的重要组成部分。微型藻类和水生植物强烈影响人类从湖泊中获得的利益，因为它们影响水质，是支持对商业、娱乐和自给性渔业重要的物种的食物网的基础。藻类的丰度和生长速度有助于湖泊生产力，而湖泊生产力受到自然和人类来源的营养物质(主要是磷和氮)的输入的影响。湖泊生产力也受到来自分水岭的有机分子输入的影响，有机分子与藻类竞争光线，在高浓度时，可能会产生茶色的水。来自分水岭的营养物质和有机分子的输入在不同的湖泊之间有很大的不同，而且随着时间的推移也会发生变化。研究人员将研究流域输入对湖泊水质、食物网和人类从湖泊中获得的其他好处的影响。他们的研究将在实验上测试和改进湖泊生产力的数学模型，并最终预测湖泊对分水岭输入的营养物质和有机分子的反应，这些输入在不同的地形和时间内都会发生变化。该项目将支持培训6名本科生，其中包括来自波多黎各的学生和美洲原住民。这些学生将进行独立研究项目，作为为期十周的田野生态项目的一部分。研究人员将使用重复的中游实验、跨广泛自然坡度的比较研究和全湖操作来测试从他们的湖泊生产力数学模型中得出的假设。首先，将使用重复的中微体来评估陆源有机碳和营养物质的预测抵消效果，这些元素以不同的比例供应。其次，该项目将使用湖泊食物网生产力的比较调查来测试湖泊大小如何改变陆地有机碳和营养物质的影响的预测。第三，研究人员将在全湖操纵陆地有机碳和养分输入的过程中拥抱自然生态系统的全部复杂性。最后，在根据实验结果改进湖泊生产力的数学模型后，研究人员将使用全球荟萃分析来测试数学模型的一般适用性。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Lakes are economically and culturally important components of the landscape. Microscopic algae and aquatic plants strongly influence the benefits that humans derive from lakes, because they influence water quality and are the foundation of the food web supporting species important to commercial, recreational, and subsistence fisheries. The abundance and growth rate of algae contribute to lake productivity, and lake productivity is affected by inputs of natural and human-derived nutrients, primarily phosphorus and nitrogen. Lake productivity is also influenced by inputs of organic molecules from the watershed which compete with algae for light and, at high concentrations, can result in tea-colored water. Inputs of nutrients and organic molecules from the watershed vary substantially from lake to lake and change through time as well. The researchers will study the implications of watershed inputs for lake water quality, food webs, and other benefits humans derive from lakes. Their research will experimentally test and refine a mathematical model of lake productivity and ultimately predict the response of lakes to watershed inputs of nutrients and organic molecules that vary across the landscape and through time. The project will support the training of six undergraduate students, including students from Puerto Rico and Native American populations. These students will conduct independent research projects as part of a ten-week field ecology program. The researchers will use replicated mesocosm experiments, a comparative study across broad natural gradients, and a whole-lake manipulation to test hypotheses drawn from their mathematical model of lake productivity. First, predicted counteracting effects of terrestrially-derived organic carbon and nutrients will be evaluated using replicated mesocosms subjected to supplies of these elements in varied ratios. Second, the project will use a comparative survey of lake food web productivity to test predictions for how lake size alters the effect of terrestrial organic carbon and nutrients. Third, the researchers will embrace the full complexity of natural ecosystems in a whole-lake manipulation of terrestrial organic carbon and nutrient inputs. Finally, following refinement of the mathematical model of lake productivity based on experimental results, the researchers will use a global meta-analysis to test the general applicability of the mathematical model.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.