RAPID: Effects of Drying Disturbance on Energy Flux Across the Aquatic-Terrestrial Boundary: Dam Malfunction Influences Aquatic Insect Emergence Quantity and Phenology

Montana State University, Bozeman MT

Investigators

Abstract

Aquatic insects emerging from rivers during the hatch provide a major source of energy and nutrients to many predators. The nutrients, such as carbon and nitrogen, that are contained in aquatic insects are an important food subsidy to terrestrial ecosystems. However, insects are sensitive to and declining globally because of altered water availability, pollution, and temperature warming. Despite these widespread declines, little is known about how emergence may affect neighboring terrestrial ecosystems because the critical adult aquatic insect life-stage that allows energy and nutrients to be transferred from the aquatic environment to terrestrial consumers is sorely understudied in monitoring programs. This project investigates the role of a severe drying disturbance in regulating emerging aquatic insect hatches, in particular that of the salmonfly, which is a species of large aquatic insect in the stonefly order that is sensitive to global change. The researchers are evaluating how drastically reduced water flow from a dam gate failure influences salmonfly density, biomass, and emergence timing. A postdoctoral scholar and several undergraduate research assistants are being trained, a public survey on the topic of drought will be completed, and the research will be presented at a local festival in southwestern Montana. Public outreach will highlight the tight connections between water and land and the importance of emerging aquatic insects as a source of nutrients and energy to fish, birds, and mammals. This project will make transformative contributions to our understanding of the shifting role and resiliency of aquatic-terrestrial linkages under anthropogenic change by contributing novel information about the influence of a pulse drying disturbance on the adult life-stage of aquatic insects. The research project investigates how a dam malfunction on the Madison River in southwestern Montana that resulted in a short but extensive drying event could change aquatic insect emergence compared to prior years. The focal organism for the research is the giant salmonfly, which is an ecologically and culturally important aquatic insect in rivers in the Rocky Mountain West. The project will quantify salmonfly density and timing during emergence using field observations, laboratory flume experiments that manipulate drought conditions to assess salmonfly survival and movement, and simulations of different drying extents to quantify the influence of drought on export of nutrients from aquatic to terrestrial habitats. This project is one of the first to evaluate how global change alters nutrient cycles by changing aquatic insect hatches and severing ties between aquatic and terrestrial ecosystems. 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.