Macroinvertebrate Ecosystem Engineers Mediate Whole-Stream Metabolism and Nutrient Uptake

许多溪流昆虫对水质的变化高度敏感，以至于科学家使用某些溪流昆虫物种的存在或不存在作为河流和溪流水质的指标。然而，有证据表明，相反的情况可能也是正确的：溪床中的溪流昆虫的活动可能有助于以令人惊讶的方式调节溪流的水质。这一奖项将记录溪流昆虫如何改变溪流渠道和河床下面的砾石之间的水交换。这种交换可以将污染物从河道输送到河床。在河床中，微生物分解污染物，提供了一种从溪流中去除污染物的自然机制。因此，这些溪流昆虫可能会改变这些重要的水交换率，同时也为微生物提供了新的栖息地。研究人员将调查溪流昆虫在控制自然净化河流污染物的过程中可能发挥的作用，从而促进溪流中高水质的维持。将对从小学到研究生的学生进行培训，并制作视频，强调溪流昆虫在溪流水质中的重要性。具体地说，研究人员将调查溪床中的蝉活动如何通过以下方式改变河流和溪流的生物地球化学循环：(I)调节河床的水力传导性、水文交换和由此产生的营养处理；以及(Ii)通过改变溪床微生物生物膜的栖息地条件和生态位机会来影响微生物新陈代谢和相关的营养处理。该项目将使用一套实验室水槽实验和实地围栏实验，以量化僵蝇丝网和退却对水力传导性和河床停留时间分布的影响，并记录丝网和退却如何改变河床微生物栖息地和代谢途径的相关表达。然后，研究人员将把实验结果整合到河流生态系统模型中，以了解在河段尺度上，在调节全流呼吸和营养处理方面，由蜻蜓驱动的变化对水文的相对贡献与对微生物群落的变化的相对贡献。这项研究将首次：(I)量化大型无脊椎动物(在这种情况下是身体)如何改变砾石床河流和小溪的河床水文；(Ii)量化大型无脊椎动物生态系统工程师如何影响微生物群落及其代谢途径；以及(Iii)开发一种新的建模方法，以预测动物改变的水文和微生物活动情景下的养分吸收。这些研究的结果将确定新的生物学考虑因素，通过连接生态系统生态学、水生昆虫学和水文学的学科，将其纳入河流水流动力学和生态系统功能的理论和经验模型。通过视频和教育将从小学到研究生的公众宣传将突出大型无脊椎动物在改变水文学、生物地球化学和河流新陈代谢方面的重要性。该奖项反映了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。

Many stream insects are highly sensitive to changes in water quality -- so much so that scientists use the presence or absence of certain stream insect species as indicators of water quality in rivers and streams. Yet evidence suggests that the reverse may also be true: the activity of stream insects in stream beds may help regulate water quality in streams in surprising ways. This award will document how stream insects alter the exchange of water between stream channels and underlying gravels of the streambed. This exchange can transport pollutants from the stream channel into the streambed. In the streambed, microbes break down the pollutants, providing a natural mechanism to remove pollutants from streams. Thus, these stream insects may alter these important water exchange rates while also providing new habitat for microbes. Researchers will investigate the ways in which stream insects may play in controlling processes that naturally cleanse rivers of pollutants and thereby facilitate the maintenance of high water quality in streams. Students from elementary through postgraduate will be trained and a video produced to highlight the importance of stream insects in the water quality of streams.Specifically, researchers will investigate how caddisfly activity in the streambed alters river and stream biogeochemical cycling by: (i) regulating streambed hydraulic conductivity, hydrologic exchange, and resultant nutrient processing, and (ii) influencing microbial metabolism and associated nutrient processing by altering habitat conditions and niche opportunities for streambed microbial biofilms. The project will use a suite of laboratory flume experiments and field enclosure experiments to quantify the impacts of caddisfly silk nets and retreats on hydraulic conductivity and streambed residence time distribution for water, as well as documenting how silk nets and retreats alter streambed microbial habitats and associated expression of metabolic pathways. Researchers will then integrate experimental results into a stream ecosystem model to understand the relative contribution of caddisfly-driven changes to hydrology versus changes to microbial communities in regulating whole-stream respiration and nutrient processing at the river reach scale. This study will be the first to: (i) quantify how macroinvertebrates (in this case, caddisflies) alter streambed hydrology in gravel-bedded rivers and streams, (ii) quantify how macroinvertebrate ecosystem engineers can influence microbial communities and their metabolic pathways, and (iii) develop a novel modeling approach to predict nutrient uptake under scenarios for animal-altered hydrology and microbial activity. The results from these studies will identify new biological considerations to be incorporated into theoretical and empirical models of river water flow dynamics and ecosystem functioning by bridging the disciplines of ecosystem ecology, aquatic entomology, and hydrology. Public outreach via a video and education will spanning elementary to postgraduate will highlight the importance of macroinvertebrates in altering hydrology, biogeochemistry, and metabolism of streams.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.