Carbon cycling and food web energy transfer in salinized headwater streams

由于与农业、道路除冰、废水排放和采矿有关的活动，全球淡水生态系统正在变得盐化（或“咸”）。在阿巴拉契亚中部，水源生态系统特别容易受到露天煤矿开采造成的盐碱化的影响，露天煤矿开采是该地区广泛的经济活动。盐浓度的增加对水生生物造成压力，并可能使一些微生物和动物无法在源头生存。这是令人担忧的，因为阿巴拉契亚山脉的源头是一些独特生物的家园，总的来说，这里有一些世界上最多样化的水生昆虫群落。溪流昆虫特别适合循环养分，并将周围森林的食物能量分配到水生食物网中。迫切需要了解盐碱化如何影响淡水昆虫群落、溪流生产力和食物网能量转移。盐碱化对上游淡水动物的影响将与当地K-12教师、学员、科学家和地区决策者分享。还将开发和共享用于河流生物评估的新指标。本研究将通过测量食物网碳的产生和转移来评估盐度对水源中碳(C)加工的影响。采矿暴露矿物的风化作用增强，可提高水源中主要离子和盐度，对微生物和大型无脊椎动物的生长和群落组成产生影响。这种生物应激反应可能会对河流食物网和生态系统过程（如分解和初级生产）产生级联效应。预计盐渍化将缓解初级生产者的盐限，提高初级总产量。相反，在异养生产中预测了补贴-胁迫响应。因此，随着盐度梯度的增加，营养转移效率的类似补贴-胁迫反应最终可能降低最高盐度下食物网碳转移。为了验证这些假设，将在代表盐度梯度的9条研究流中同时测量C池、转移和转换。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Freshwater ecosystems are becoming salinized (or “salty”) across the globe from activities associated with agriculture, road de-icing, wastewater discharge, and mining. In central Appalachia, headwater stream ecosystems are particularly vulnerable to the impacts of salinization from surface coal mining, a widespread economic activity in the region. Increased salt concentrations stress aquatic organisms and can make headwaters unlivable for some microbes and animals. This is concerning because Appalachian headwaters are home to some unique organisms and collectively, have some of the most diverse aquatic insect communities in the world. Stream insects are especially adapted to cycling nutrients and distributing food energy from the surrounding forests into aquatic food webs. There is an urgent need to understand how salinization affects the freshwater insect community, stream productivity, and food web energy transfer. The consequences of salinization on freshwater animals in headwater streams will be shared with local K-12 teachers and trainees, scientists, and regional policy makers. New metrics for stream bioassessments will also be developed and shared. This research will assess salinity effects on carbon (C) processing in headwater streams through measurements of food web C production and transfer. Enhanced weathering of mining-exposed minerals can elevate major ions and salinity in headwater streams, with documented impacts to microbial and macroinvertebrate growth and community composition. Such organismal stress responses likely have cascading effects on stream food webs and ecosystem processes like decomposition and primary production. Salinization is predicted to alleviate salt limitation in primary producers and increase gross primary production (GPP). In contrast, subsidy-stress responses are predicted in heterotrophic production. Thus, along an increasing salinity gradient, similar subsidy-stress responses in trophic transfer efficiency could ultimately decrease food web C transfer at the highest salinities. To test these hypotheses, simultaneous measurements of C pools, transfers, and transformations will be taken in nine study streams that represent a salinity gradient.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.