Year Established: 2019 Start Date: 2019-05-31 End Date: 2020-05-30
Total Federal Funds: $2,000 Total Non-Federal Funds: $880
Principal Investigators: Benjamin B. Tumolo
Abstract: Ecosystem engineering is a ubiquitous ecogeomorphic process by which organisms modify physical habitat characteristics, thereby influencing patterns of biological organization1. Often, modification of physical environments by ecosystem engineers creates beneficial habitats and/or ameliorates harsh conditions for a diversity of species that would otherwise be absent2. Here I propose to investigate how aquatic insect ecosystem engineering may have positive effects on stream ecosystem function by creating hot-spots of insect production. I predict that silk structures produced by stream insects alter near bed hydraulics and food resource availability in ways that increase benthic community density and diversity. Findings from this project will be relevant for identifying how negative effects of altered hydrological regimes may be offset by positive interactions between ecosystem engineers and their communities in the face of global change. Net-spinning caddisflies (Tricoptera:Hydropsychidae) are aquatic insect larvae that have been shown to act as important ecosystem engineers within streams throughout the U.S.3-5. Net-spinning caddisflies build silk catch-nets with retreats of organic/inorganic material within streambed to passively feed on items flowing through the water. The silk structures transform local geophysical processes by markedly increasing substrate stability thereby changing patterns of sediment erosion3,5 and by creating hydraulic refugia for other aquatic insects6,7. Despite the recognized and substantial geomorphic impacts of caddisfly engineers, few investigations have quantified consequences for ecosystem function. For example, the effects of caddisfly engineering on stream insect production and distribution is poorly understood. Patterns of aquatic insect production have critical implications for food web linkages between basal resources and higher trophic levels within (e.g. trout) and across (e.g. sparrows) ecosystem boundaries8,9. Preliminary analyses from high elevation headwater streams suggest that caddisfly engineering can concentrate local densities of insects by as much as 90% compared to aggregate background densities10, thereby creating resource hotspots. I propose to investigate the mechanism underlying the spatial dynamics of the relationship between caddisfly engineering and insect density within Montana streams. Previous investigations have demonstrated caddisfly silk structures alter hydraulics by decreasing local current velocity thus improving habitat for certain insects11, however additional mechanisms such as resource augmentation have yet to be tested.