Collaborative research: Defining ecosystem heterotrophic response to nutrient concentrations and ratios

合作研究：定义生态系统对养分浓度和比率的异养响应

• 批准号: 0918904
• 负责人: Jonathan Benstead
• 金额: $ 23.15万
• 依托单位: University of Alabama Tuscaloosa
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0918904&HistoricalAwards=false
• 关键词: Collaborative; research; Defining; ecosystem; heterotrophic

Streams and rivers are important sites of global carbon processing. Carbon in the form of dead leaves and wood (detritus) from the land enters streams and is colonized by bacteria and fungi (heterotrophic microorganisms). This complex of microorganisms and detrital carbon fuels food webs that support fish, amphibians and other consumers. Detrital carbon is consumed by organisms but is also converted to carbon dioxide by bacteria and fungi. Problematic to this important detritus-fuelled pathway is that human-derived nutrient inputs (nitrogen and phosphorus) stimulate microbially-driven release of carbon dioxide and decomposition of detritus, resulting in less available carbon for important ecosystem functions. In this study, laboratory incubations, streamside channels and whole-stream nutrient additions will be used to determine the concentrations and ratios of nitrogen and phosphorus that elicit such ecosystem changes. Knowledge of these threshold concentrations and ratios can guide management of aquatic ecosystems to maintain water quality for wildlife conservation and human utilization. Study findings can aid predictions of how excess nutrients affect the fate of detrital carbon in streams, which is relevant to global carbon budgets. Excess nutrient loading is the primary source of impairment to more than half of the freshwater and coastal ecosystems in the U.S. While hundreds of scientific studies have assessed autotrophic (e.g. algal) response to nutrient loading, few have tested nutrient effects on detritus, heterotrophic microorganisms and the larger aquatic organisms they support. The proposed research will advance our understanding of how aquatic ecosystems are affected by nutrients via detritus-fuelled pathways that potentially lead to carbon loss, a perspective that is currently lacking in management decisions related to nutrient enrichment. This project will provide critical research support to four early-career investigators, as well as experience and training for undergraduate and graduate students at three institutions in the southeastern U.S. The project will include public and K-12 educational components that will focus on how excess nutrients affect aquatic food webs and water quality.

溪流和河流是全球碳处理的重要场所。陆地上的枯叶和木材（碎屑）形式的碳进入溪流，并被细菌和真菌（异养微生物）定殖。这种微生物和碎屑碳的复合体为食物网提供了燃料，为鱼类、两栖动物和其他消费者提供了食物。碎屑碳被生物体消耗，但也被细菌和真菌转化为二氧化碳。这一重要的碎屑燃料途径的问题在于，人类来源的营养输入（氮和磷）会刺激微生物驱动的二氧化碳释放和碎屑分解，导致重要生态系统功能可用的碳减少。在这项研究中，实验室孵化、河边渠道和全溪流营养物添加将用于确定引起此类生态系统变化的氮和磷的浓度和比率。了解这些阈值浓度和比率可以指导水生生态系统的管理，以维持野生动物保护和人类利用的水质。研究结果可以帮助预测过量的营养物如何影响溪流中碎屑碳的命运，这与全球碳预算相关。过量的养分负荷是损害美国一半以上淡水和沿海生态系统的主要原因。虽然数百项科学研究评估了自养（例如藻类）对养分负荷的反应，但很少测试养分对碎屑、异养微生物和微生物的影响。它们支持的较大的水生生物。拟议的研究将增进我们对水生生态系统如何通过碎屑燃料途径受到养分影响的理解，这些途径可能导致碳损失，而目前与养分富集相关的管理决策缺乏这一观点。该项目将为四名早期职业研究人员提供关键的研究支持，并为美国东南部三所机构的本科生和研究生提供经验和培训。该项目将包括公共和 K-12 教育部分，重点关注如何消除营养过剩。影响水生食物网和水质。