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.
