Responses of macroinvertebrate communities to small dam removals: Implications for bioassessment and restoration

Abstract

Small dam removals are increasing on a global scale; yet, general predictions of organism response to dam removal are constrained by heterogeneity of study designs, implementation strategies, geographies, and characteristics of dams and their removals. Macroinvertebrate data extracted from 29 studies including 34 small dam removals over a broad geographical range were re‐analysed utilizing dam removal effect sizes (a quantified change from before to after removal). Effect sizes of 10 metrics of community structure were calculated to investigate the spatiotemporal extent of small dam removal effects and if responses differ with characteristics of the dam and environmental settings. We found that dam removal had initial negative effects on total macroinvertebrate density and Ephemeroptera, Plecoptera and Trichoptera (EPT) density, both downstream and upstream; however, recovery to pre‐removal values was reached and exceeded after c. 15–20 months. Mean annual discharge, land use in the catchment and distance from the dam affected the magnitude and direction of responses of four community metrics: total density, EPT density, %EPT density and family biotic index. Synthesis and applications. Our study provides evidence that macroinvertebrate community recovery from dam removal is mediated by catchment characteristics and system size, which may correlate with sediment flushing efficiency. Negative impacts were observed in smaller systems or those with a high percentage of undisturbed catchment areas, conditions that may benefit from sediment management prior to dam removal. Significant responses in reaches upstream of the impoundment clearly indicate that caution be applied to interpretations of response in sampling designs that utilize upstream sites for reference condition.

DNA metabarcoding adds valuable information for management of biodiversity in roadside stormwater ponds

“…(c) Results obtained from db-RDA for the morphological dataset based on abundance. The purple arrows represent different species; the red arrows represent environmental variables, in which WaterPol and Sediment represent pollution levels in the water column and sediments, respectively reasons (e.g., Carlson, Donadi, & Sandin, 2018;Pandey et al, 2017).…”

Conceptualizing Ecological Responses to Dam Removal: If You Remove It, What's to Come?

“…Studies of aquatic invertebrate and fish responses to dam removal generally support this trajectory (Bushaw-Newton et al 2002, Stanley et al 2002, Dorobek et al 2015). In a meta-analysis of numerous dam removals, Carlson and colleagues (2018) found that lentic invertebrates first declined in density after dam removal but subsequently recovered within 15–20 months. During the recovery phase, lotic invertebrate taxa, such as EPT, tended to become more prevalent (Bushaw‐Newton et al 2002), attaining community assemblages similar to upstream free-flowing reference sites (e.g., Stanley et al 2002).…”

Shifting food web structure during dam removal—Disturbance and recovery during a major restoration action

“…Our study focused on the short-term sediment impacts to aquatic food webs during the three years of active dam removal (WYs 2012-2014). Many studies have investigated the effects of dam removal on benthic invertebrates (reviewed by [20]), and other predominantly laboratory-based investigations have examined the effects of increased turbidity and bed disturbance on salmonid foraging [21][22][23]. However, we are not aware of any published studies that have investigated the coupled effects of dam removal on prey availability and prey consumption.…”