1. Worldwide, the addition of treated wastewater (i.e. effluent) to streams is becoming more common as urban populations grow and developing countries increase their use of wastewater treatment plants. Release of treated effluent can impair water quality and ecological communities, but also could help restore flow and maintain aquatic habitat in water-stressed regions. To assess this range of potential outcomes, we conducted a global review of studies from effluent-fed streams to examine the impacts of effluent on water quality and aquatic and riparian biota. 2. We identified 147 quantitative studies of effluent-fed streams, most of which were from the U.S.A. and Europe. Over 85% of the studies identified water quality as a primary study focus, including basic physical and chemical parameters, as well as trace organic contaminants. Nearly 60% of the studies had at least some focus on aquatic or riparian biota, primarily fish, aquatic invertebrates, and basal resources (e.g. algae). 3. Effluent inputs generally impaired water quality near discharge points, mainly through increased water temperature, nutrients, and concentrations of trace organic contaminants, but also via decreased dissolved oxygen levels. The majority of ecological studies found that basal resources, aquatic invertebrates, and fish were negatively affected in a variety of ways (e.g. biodiversity losses, replacement of sensitive with tolerant species). However, several studies showed the im

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Treated wastewater, also known as effluent, is discharged into streambeds where it can augment or create aquatic habitat in arid regions. However, discharge fluctuations can result in daily stream drying and rewetting. In this study, we documented flow intermittence and resulting fish stranding and mortality over a 12-week period on an effluent-dependent reach of the lower Santa Cruz River in Tucson, Arizona, USA. We hypothesized that fish stranding would be positively related to the duration of flow prior to drying (increased recolonization potential) and flow recession rates (increased stranding likelihood). Using trail cameras, we monitored drying duration and extent along a 2.1-km reach of river known to experience flow intermittence and counted stranded fish once a week. Drying extent varied widely (range: 0-1.88 km) and averaged 0.79 km ± 0.14 SE. We observed a total of 323 fish strandings across the 12 weeks (range: 0-74 individuals per day; mean: 26.9 ± 8.3 SE). Ninety-nine percent of observed fish were Poeciliidae (63% of which were fry), including nonnative western mosquitofish (Gambusia affinis). The recession rate was a positive predictor for the daily stranding count of poeciliids (p = .008). Flow duration was not significant (p = .100) but was included in the top model (R 2 = 0.782). As urban development continues, the discharge of effluent into rivers and streams will become more common throughout the world. Continued research is needed to understand the benefits and challenges presented by these effluent-driven flow regimes, including their impacts on aquatic taxa.

Variability in abiotic and biotic factors during larval stages has profound impacts on fish recruitment. In Lake Michigan, where the composition of lower trophic levels has undergone considerable changes in the past decade, managers are concerned that fish recruitment could be negatively affected. We hypothesized that spatial variation in Lake Michigan larval fish density and growth can be explained by various environmental predictor variables. In July 2015, we sampled larval fish and zooplankton at 24 sites (distributed among eight transects) around Lake Michigan. We measured larval fish densities and estimated growth rates and diets of the two most abundant species: the Alewife Alosa pseudoharengus and Bloater Coregonus hoyi (prey fish that represented 89% and 4% of the total catch, respectively). Larval Alewife densities at a given site ranged from 0 to 42.57 larvae/100 m3, but no explanatory variables explained the variation. Alewife mean growth rate equaled 0.50 mm/d, and fish age and zooplankton density best explained growth variation across sites. Larval Bloater densities ranged from 0 to 1.16 larvae/100 m3, and mean growth rate was 0.21 mm/d. Across all sites, 67% of larval Alewife stomachs were empty, whereas only 16% of Bloater stomachs were empty. Larval fish growth rates observed in our study were at least 40% slower than those reported in previous decades for both Alewife and Bloater. Worsening prey environment for pelagic larvae, such as Alewife and Bloater, during the era of abundant dreissenid mussels could reduce the probability of strong year‐classes, which in turn may affect growth and survival of recreationally important salmonine predators.