Data from: Macroinvertebrate community responses to disturbance in a fragmented river with contrasting legacies of alteration

Flow is a critical factor determining riverine ecosystem structure and
function. Widespread hydrologic alteration, however, has impacted the
ecological integrity of rivers in ways that are not well understood,
including responses of biological communities to increasingly frequent and
severe climatic disturbances. Our study compared responses of invertebrate
communities on woody debris to large flooding and extreme drought in two
highly contrasting segments of an impaired low-gradient river. The
upstream segment, which according to previous research has higher
α-diversity and production of large-bodied and sensitive invertebrates,
maintained higher flows and longitudinal connectivity throughout the
four-year study. Communities in this upper segment resembled one another
among sites (lower spatial turnover), but experienced greater temporal
shifts in composition associated with hydrological disturbances.
Conversely, invertebrate communities in the highly altered downstream
segment, which is impaired by reduced flow, sedimentation, and hypoxia,
were comprised of smaller-bodied and pollution-tolerant taxa with lower
α-diversity. Unlike the upper segment, communities were patchily
distributed among sites (higher spatial turnover), which made it more
difficult to detect system-wide temporal variation in composition
throughout the study. Our study underscores the benefit of including
measures of connectivity and spatial heterogeneity when assessing the
ecological integrity of lotic systems. Understanding system-wide response
to disturbances across longer time frames can help better predict and
mitigate the impacts of climate change on ecosystem integrity in degraded
rivers.