Macroinvertebrate communities in a Northern Great Plains river are strongly shaped by naturally occurring suspended sediments: implications for ecosystem health assessment

Abstract

AbstractRivers are typified by considerable seasonal flow variability. In rivers that flow through alluvial deposits, fine sediment (<63 μm) is readily suspended, especially during periods of high discharge. Therefore, assessment of the effects on biota of anthropogenic stressors must occur within the context of dynamic turbidity and background flow conditions. We used the Qu’Appelle River in southern Saskatchewan as a study system for which we developed a model in which discharge is a principal determinant of in-stream suspended sediment. We explored this relationship with a case study showing that macroinvertebrate community structure was strongly correlated with suspended sediment gradients and, ultimately, predicted by discharge. Factors affecting sediment loads and ecosystem responses in managed systems should be considered so that in-stream water quantity and quality needs are met. This new understanding should enable development of improved ecosystem-based flow-management objectives.