Spatial and temporal variability of aquatic insect emergence in Pool 8 of the Upper Mississippi River.

Abstract

Aquatic insect emergence provides an important nutrient subsidy to the terrestrial ecosystem. However, little is known about the spatial and temporal variability in aquatic insect emergence. This study examined the spatial and temporal variability of aquatic insect emergence and tested the effect of historic inundation duration (2012 – 2019) and flow-path distance from the main channel has on aquatic insect emergence. Emergence traps were placed at 27 sites on Pool 8 of the Upper Mississippi River during June – August 2020. Aquatic insect richness was significantly different across the months, and biomass varied based on site location. However, there was no effect of different distance classes and inundation durations on richness or biomass. This study shows insect emergence is continuous during the summer months providing nutrients and energy to the terrestrial ecosystem. Flow-path distance from the main channel did not appear to influence richness and biomass, suggesting invertebrate drift from the main channel is not an important dispersal mechanism for aquatic insects in floodplain habitats on the Upper Mississippi River. Although historic inundation duration did not affect richness or biomass, future studies could explore insect emergence patterns across more floodplain sites that experience drying to better estimate these effects.