Impacts of wastewater treatment plants on benthic macroinvertebrate communities in summer and winter.

Treated effluent from municipal wastewater treatment plants (WWTPs) is a major source of contamination that can impact population size, community structure, and biodiversity of aquatic organisms. However, because the majority of field research occurs during warmer periods of the year, the impacts of wastewater effluent on aquatic communities during winter has largely been neglected. In this study, we assessed the impacts of wastewater effluent on aquatic benthic macroinvertebrate (benthos) communities along the effluent gradients of two WWTPs discharging into Hamilton Harbour, Canada, during summer and winter using artificial substrates incubated for 8 weeks. At the larger of the two plants, benthic macroinvertebrate abundance was higher and diversity was lower at sites downstream of the outfall compared to upstream sites in both seasons. Whereas at the smaller plant, the opposite was observed, abundance increased and diversity decreased with distance from the outfall in both seasons. While the impacts of wastewater on benthic communities were largely similar between seasons, we did detect several general seasonal trends - family diversity of macroinvertebrates was lower during winter at both WWTPs and total abundance was also lower during winter, but only significantly so at the smaller WWTP. Further, benthic macroinvertebrate community composition differed significantly along the effluent gradients, with sites closest and farthest from the outfall being the most dissimilar. Our contrasting results between the WWTPs demonstrate that plants, with different treatment capabilities and effluent-receiving environments (industrial/urban versus wetland), can dictate how wastewater effluent impacts benthic macroinvertebrate communities.

The Lake Erie HABs Grab: A binational collaboration to characterize the western basin cyanobacterial harmful algal blooms at an unprecedented high-resolution spatial scale.

Monitoring of cyanobacterial bloom biomass in large lakes at high resolution is made possible by remote sensing. However, monitoring cyanobacterial toxins is only feasible with grab samples, which, with only sporadic sampling, results in uncertainties in the spatial distribution of toxins. To address this issue, we conducted two intensive "HABs Grabs" of microcystin (MC)-producing Microcystis blooms in the western basin of Lake Erie. These were one-day sampling events during August of 2018 and 2019 in which 100 and 172 grab samples were collected, respectively, within a six-hour window covering up to 2,270 km2 and analyzed using consistent methods to estimate the total mass of MC. The samples were analyzed for 57 parameters, including toxins, nutrients, chlorophyll, and genomics. There were an estimated 11,513 kg and 30,691 kg of MCs in the western basin during the 2018 and 2019 HABs Grabs, respectively. The bloom boundary poses substantial issues for spatial assessments because MC concentration varied by nearly two orders of magnitude over very short distances. The MC to chlorophyll ratio (MC:chl) varied by a factor up to 5.3 throughout the basin, which creates challenges for using MC:chl to predict MC concentrations. Many of the biomass metrics strongly correlated (r > 0.70) with each other except chlorophyll fluorescence and phycocyanin concentration. While MC and chlorophyll correlated well with total phosphorus and nitrogen concentrations, MC:chl correlated with dissolved inorganic nitrogen. More frequent MC data collection can overcome these issues, and models need to account for the MC:chl spatial heterogeneity when forecasting MCs.

Shoaling preferences and the effects of sex ratio on spawning and aggression in small laboratory populations of zebrafish (Danio rerio).

Owing to a lack of basic information on the biology of zebrafish (Danio rerio), lab managers must often base decisions regarding the care and use of this species on anecdotal information. In an effort to provide researchers with context-specific behavioral information, the authors evaluated shoaling and spawning behaviors in small groups of zebrafish. In each shoaling assay, a fish was given a choice to shoal with either a single fish or a group of three fish. Females preferred to shoal with a group of three individuals rather than with a single individual, regardless of the sex of the other fish. Males preferred groups of three males over single males but preferred single females to groups of three females. In spawning assays, zebrafish were placed in breeding tanks in one of three sex ratios (1 male:1 female; 3 males:1 female; 1 male:3 females). Reproductive efficiency did not differ among groups, but aggression (evaluated according to presence of shed scales) was more frequently observed in the male-dominated treatment group.