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Nitellopsis obtusa was first reported in North America in 1974. The overall ecological threat that N. obtusa poses towards freshwater ecosystems in its non‐native range is thought to be similar to other invasive macrophyte species. However, few studies have evaluated the impacts to aquatic communities upon successful establishment of this species in North America. Despite N. obtusa being a non‐native invasive species in North America, it is considered a beneficial macrophyte within its native range in EurasiaWe evaluated the impacts associated with the non‐native invasive charophyte N. obtusa on the lower aquatic food web (LAFW) communities (phytoplankton, macroinvertebrates, and macrophytes) in a large, shallow lake in Ontario, Canada. To tease apart abiotic and biotic factors that influence LAFW species assemblages, a generalised linear latent variable model (GLLVM) was used.Over the course of the 4‐year study period, N. obtusa abundance significantly increased throughout the lake (pairwise comparison, p < 0.001) and notable shifts in community composition occurred across years (PERMANOVA, p < 0.001), especially for the phytoplankton and macrophyte communities.Nitellopsis obtusa was also found to be associated with a decline in diversity, where Simpson's diversity indices across all LAFW communities decreased as a function of increasing N. obtusa biomass. The GLLVM analysis revealed significant negative associations between N. obtusa and the majority of LAFW taxa. Most notably, there was a significant (p < 0.001) negative relationship between Myriophyllum spicatum, a previously established non‐native invasive macrophyte, and N. obtusa. The GLLVM model also demonstrated that N. obtusa had positive co‐occurrence relationships with other members of the macrophyte community including Utricularia vulgaris, Najas flexilis, Potamogeton crispus, and Stuckenia pectinata.These results show for the first‐time significant impacts to the LAFW in an invaded ecosystem, which raises major concerns for fish communities that depend on the LAFW for food and habitat. Further studies are necessary to confirm the extent of these impacts in other invaded lakes. [ABSTRACT FROM AUTHOR]

This study was conducted in Lake Scugog, a large, shallow reservoir in Ontario, Canada. Historically, Lake Scugog has been a macrophyte-dominated ecosystem with a productive fishery. In recent years, periodic Microcystis blooms have erupted coinciding with the discovery of the non-native macroalga Nitellopsis obtusa in the lake. From 2016 to 2018, we conducted field surveys to assess the physical, chemical, and biological conditions across 12 sites spanning the lake. All study species (N. obtusa, Dreissena polymorpha, and Microcystis spp.) increased from 2016 to 2018. To determine potential biotic and abiotic drivers of Microcystis blooms, we used a structural equation modelling (SEM) approach. The SEM (r2 = 0.27, p < 0.05) revealed several positive (precipitation, chloride, depth, and N. obtusa) and negative (total nitrogen) explanatory variables for Microcystis biomass. The only statistically significant biotic driver was N. obtusa, which was a positive explanatory variable for both D. polymorpha and Microcystis. Future work will test the efficacy of the SEM model across Ontario lakes to confirm the facilitative role of N. obtusa on D. polymorpha and Microcystis populations. [ABSTRACT FROM AUTHOR]

Nitellopsis obtusa (Desv.) J. Groves (starry stonewort) is a macroalga in the Characeae family first documented in North America c. 1974. Since initial introduction, N. obtusa clonal populations quickly established in inland lakes as early as 2005. Despite increased N. obtusa monitoring over the last decade, only sterile or male specimens were documented in North America; however, during routine monitoring in Lake Simcoe and Lake Scugog in 2022, we discovered the presence of female gametangia on N. obtusa. In addition, two other Characeae genera had prevalent antheridia and oogonia, co-occurring with oogonia-presenting N. obtusa, which had not been observed previously despite intensive monitoring since 2008. Further studies in North America are required to confirm the proportion of female populations present within invaded regions, as well as to identify plausible causes shifting gametangia development across non-native and native Characeae, especially within the context of climate change. The presence of oogonia on N. obtusa represents a major change to our understanding of this species and its reproductive ecology in North America. [ABSTRACT FROM AUTHOR]

1. The diatom Didymosphenia geminata has emerged in recent years as a globally invasive species. Although considered native to North America, reports of nuisance blooms have increased over the last decade. 2. Previously, we determined that D. geminata was ubiquitous in two major headwaters of the South Saskatchewan River Basin (SSRB), Alberta, Canada, but found it only bloomed at certain sites, including those immediately downstream from dam outfalls. To evaluate the role of dams in the abundance and blooming of D. geminata, we compared sites just below dams to unregulated upstream reference sites in six dammed rivers of the SSRB. 3. There was a high degree of seasonal variability in D. geminata abundance among sites, but statistical analyses showed a significant propensity for the diatom to have higher cell densities and an increased frequency of blooms at dam sites. 4. Important predictor variables of D. geminata abundance included dam presence, water clarity and total phosphorus concentration. When data from dam sites were analysed, a multiple regression model using mean discharge and pH as independent predictors explained 73% of the variation in D. geminata cell density. 5. Analysis of 3 years of data from one study river (Red Deer River) revealed consistently higher D. geminata cell densities at the dam site compared to the upstream reference. This analysis also showed that average cell density fluctuated by orders of magnitude from year-to-year. 6. Due to the ecological and aesthetic concerns regarding the global spread and blooming of D. geminata, we recommend that dams be viewed as key candidates for mitigating blooms in flow regulated systems. [ABSTRACT FROM AUTHOR]

The Great Salt Plains (GSP) in north-central Oklahoma, USA is an expansive salt flat (∼65 km2) that is part of the federally protected Salt Plains National Wildlife Refuge. The GSP serves as an ideal environment to study the microbial diversity of a terrestrial, hypersaline system that experiences wide fluctuations in freshwater influx and diel temperature. Our study assessed cyanobacterial diversity at the GSP by focusing on the taxonomic and physiological diversity of GSP isolates, and the 16S rRNA phylogenetic diversity of isolates and environmental clones from three sites (north, central, and south). Taxonomic diversity of isolates was limited to a few genera (mostly Phormidium and Geitlerinema), but physiological diversity based on halotolerance ranges was strikingly more diverse, even between strains of the same phylotype. The phylogenetic tree revealed diversity that spanned a number of cyanobacterial lineages, although diversity at each site was dominated by only a few phylotypes. Unlike other hypersaline systems, a number of environmental clones from the GSP were members of the heterocystous lineage. Although a number of cyanobacterial isolates were close matches with prevalent environmental clones, it is not certain if these clones reflect the same halotolerance ranges of their matching isolates. This caveat is based on the notable disparities we found between strains of the same phylotype and their inherent halotolerance. Our findings support the hypothesis that variable or poikilotrophic environments promote diversification, and in particular, select for variation in ecotype more than phylotype. [ABSTRACT FROM AUTHOR]

We studied the algal community of the Great Salt Plains (GSP), an expansive (65 km2) salt flat situated in north-central Oklahoma, USA that has been designated as the Salt Plains Microbial Observatory (SPMO) by the National Science Foundation. The GSP offered a unique opportunity to study a terrestrial, hypersaline algal community that experiences wide-ranging environmental conditions. We were able to show that ammonium-N, rather than salinity, was the most important predictor of total algal biomass. However, salinity was found to be a significant controlling variable in diatom distribution at the GSP, where diatom abundance was negatively correlated with porewater salinity concentrations. Overall, chlorophytes (likely dominated by Dunaliella spp.) were the most abundant algal group at the consistently hypersaline (>300 ppt) south site. Diatom and cyanobacterial biomass were on average highest at the central site, which experienced greater fluctuations in salinity. While taxonomic diversity was limited to three algal groups (chlorophytes, diatoms, and cyanobacteria), the salinity preferences and halotolerance ranges of isolated strains were quite variable. Although porewater salinities at the GSP are commonly near saturation (>300 ppt), the large majority of isolates had halotolerance ranges below 150 ppt. This suggests that algae at the GSP rarely achieve maximum growth rates, and could only do so when intermittent rain events reduce salinity to optimal levels. Because the vast majority of our strains were isolated from salt-saturated soil samples, maintaining viability (rather than growth efficiency) appears to be the most successful adaptation to the extreme conditions at the GSP. [ABSTRACT FROM AUTHOR]

This is the first in a series of experiments designed to characterize the Salt Plains National Wildlife Refuge (SPNWR) ecosystem in northwestern Oklahoma and to catalogue its microbial inhabitants. The SPNWR is the remnant of an ancient ocean, encompassing ~65 km² of variably hypersaline flat land, fed by tributaries of the Arkansas River. Relative algal biomass (i.e., chlorophyll concentrations attributed to Chlorophyll-a-containing oxygenic phototrophs) and physical and chemical parameters were monitored at three permanent stations for a one-year period (July 2000 to July 2001) using a nested block design. Salient features of the flats include annual air temperatures that ranged from -10 to 40°C, and similar to other arid/semi-arid environments, 15-20-degree daily swings were common. Shade is absent from the flats system; intense irradiance and high temperatures (air and sediment surface) resulted in low water availability across the SPNWR, with levels of only ca. 15 % at the sediment surface. Moreover, moderate daily winds were constant (ca. 8-12 km h-1), sometimes achieving maximum speeds of up to 137 km h-1. Typical of freshwater systems, orthophosphate (PO43-) concentrations were low, ranging from 0.04 to <1 µM; dissolved inorganic nitrogen levels were high, but spatially variable, ranging from ca. 250-600 µM (NO3- + NO2-) and 4-166 µM (NH4+). Phototroph abundance was likely tied to nutrient availability, with high-nutrient sites exhibiting high Chl-a levels (ca. 1.46 mg m-2). Despite these harsh conditions, the phototrophic microbial community was unexpectedly diverse. Preliminary attempts to isolate and identify oxygenic phototrophs from SPNWR water and soil samples yielded 47 species from 20 taxa and 3 divisions. Our data indicate that highly variable, extreme environments might support phototrophic microbial communities characterized by higher species diversity than previously assumed. [ABSTRACT FROM AUTHOR]

Pulp and paper secondary waste-treatment systems in Brazil, Canada, New Zealand, and the U.S.A. contained dynamic cyanobacterial communities, some of which exceeded heterotrophic bacterial biomass. No other viable photoautotrophic populations were detected in the ponds. Regardless of geographical location, Oscillatoriales including Phormidium, Geitlerinema, and Pseudanabaena were the dominant taxa. As well, Chroococcus (Chroococcales) was an important genus in Brazil and New Zealand. The possible impact of cyanobacteria on waste-treatment efficiency deserves further study given their large biomass and diverse metabolic characteristics.Key words: cyanobacteria, blue-green algae, heterotrophic bacteria, community structure, pulp and paper secondary waste treatment.On a observé au Brésil, au Canada, en Nouvelle-Zélande et aux États-Unis que les systèmes de traitement secondaire des rejets d'usines de pâtes et papiers contenaient des populations dynamiques de cyanobactéries dont certaines dépassent même les valeurs de la biomasse bactérienne hétérotrophe. Aucune autre population de photoautotrophes n'a été détectée dans les bassins. Indépendamment de la localisation géographique, les taxons dominants appartenaient aux Oscillatoriales incluant Phormidium, Geitlerinema et Pseudanabaena. Au Brésil et en Nouvelle-Zélande Chroococcus (Chroococcales) était aussi un genre important. L'impact potentiel des cyanobactéries sur l'efficacité du traitement des rejets mérite d'être étudié plus à fond, compte tenu de la biomasse élevée et des caractéristiques métaboliques variées de ces bactéries.Mots clés : cyanobactéries, algues bleues-vertes, bactéries hétérotrophes, organisation de la population, traitement secondaire des rejets d'usines de pâtes et papiers.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

• Nitellopsis obtusa was documented at 19 of the 60 lakes surveyed. • Shallow sites, that were closer to boat launches had higher densities of N. obtusa. • Cations other than calcium have a strong influence on N. obtusa distribution. Nitellopsis obtusa (also known as Starry Stonewort) is a Eurasian charophyte first introduced into the Laurentian Great Lakes in the 1970s. Over the last decade, there have been increasing reports of N. obtusa invasion of inland lakes in the Great Lakes basin. To improve our understanding of N. obtusa 's habitat preferences, we sampled 60 lakes across a geological transition zone in Ontario, Canada. Targeting this geological transition zone allowed us to study an array of lakes representing broad nutrient and water-hardness gradients within the same geographic and climatic region. Calcium is an important macronutrient for N. obtusa , thus it was anticipated that the presence of N. obtusa would respond strongly to calcium availability. Nitellopsis obtusa was documented at 37 sites in 19 of the 60 lakes surveyed. Lakes with N. obtusa had significantly higher cation (calcium, potassium, sodium, and magnesium) concentrations than lakes without N. obtusa (general linear mixed model with binomial error, p < 0.05). An ecological niche model based on a boosted regression tree (BRT) identified habitat features most associated with N. obtusa occurrence. Interestingly, the BRT model demonstrated that depth and the cations potassium, magnesium, and sodium were better predictors of N. obtusa presence than calcium. Although N. obtusa was found within a constrained range of calcium (15 – 57.9 mg L−1 Ca), it appears that other environmental parameters have a stronger influence on N. obtusa distribution in Ontario lakes. [ABSTRACT FROM AUTHOR]

Though microbial transformations are the primary mechanism of contaminant attenuation in wetlands, much remains to be known about microbial communities in urban wetlands. In this study, the microbial communities from urban wetlands with different runoff regimes (i.e., a contaminated remnant wetland, a constructed wetland, and a remnant wetland) were assessed for their capacity to attenuate and tolerate typical urban runoff pollutants. Results from denaturing gradient gel electrophoresis of 16S rRNA genes showed relatively high similarity in community composition among the wetlands. Community-level physiological profiles had similar results but exhibited within-site variation in both the contaminated remnant and remnant wetlands. All wetland communities were less tolerant to copper than 2,4-dichlorophenoxyacetic acid; however, the contaminated remnant wetland had the highest tolerance. All study wetlands had a limited capacity to biodegrade model chlorinated aromatic compounds (e.g., 2,4-dichlorophenoxyacetic acid and 3-chlorobenzoate). Though having different input regimes and contaminant exposure histories, the study wetlands were generally similar with respect to microbial community diversity and function. Additionally, the generally low capacity for these wetlands to biodegrade mobile chlorinated organic contaminants offers preliminary insight into the limited ecosystem services these wetlands may provide in urban environments. [ABSTRACT FROM AUTHOR]

Metformin is currently thought to be the highest drug by weight released into the aquatic environment, as a direct result of its widespread use in the treatment of a number of human health disorders. The removal of metformin from wastewaters is directly related to the formation of guanylurea (metformin's only known persistent degradation product), which is generally present at higher concentrations in surface waters than the parent compound. With metformin use rising steadily, it is important to characterize the effects of guanylurea on nontarget aquatic organisms. We recently demonstrated the effects of developmental exposure to environmentally relevant concentrations of metformin on the growth of early life stage (ELS) medaka as well as effects on the body weight of adult male fish following full‐life cycle exposures. In the present study, we describe similar effects of guanylurea exposure on these endpoints and life stages. Guanylurea led to effects on growth in a 28‐d ELS assessment that were similar to those of metformin; however, these effects occurred at concentrations in the ng/L range compared with the μg/L range for metformin. A possible sex‐dependent association with body weight changes was also observed in adults following a 165‐d full‐life cycle exposure to guanylurea alone or in a mixture with metformin. To our knowledge, the present is the first study to report the toxicity of guanylurea to nontarget aquatic organisms. Environ Toxicol Chem 2019;00:1–6. © 2019 SETAC [ABSTRACT FROM AUTHOR]

Highlights Early life stage (ELS) fish can uptake/depurate waterborne metformin. Metformin alters metabolomes, gene expression, and growth of ELS medaka. Lifelong metformin exposure affects steroid hormones in adult fish. Environmentally relevant concentrations of metformin may affect fish development. Abstract Metformin is one of the most prevalent pharmaceuticals in both surface and waste waters, yet little is known about the bioavailability and/or effects of developmental exposure on early life stage (ELS) fish. Here, we demonstrate that embryo-larval stages of medaka are capable of taking up metformin from the aquatic environment, provided exposure occurs prior to chorion hardening (∼6-hpf). Once transferred to clean water, ELS medaka are able to completely depurate metformin in <24-hours. Furthermore, ELS medaka exposed to a range of relevant concentrations of waterborne metformin (from 6 hpf through 28-days post hatch) had significantly reduced growth metrics, altered metabolomes, and changes in the expression of genes associated with cell growth. The range of concentrations investigated were 1.0, 3.2, 10, 32, and 100 μg·L−1. To examine effects of chronic, low level metformin exposure across the full medaka life-cycle, we exposed newly fertilized embryos to 3.2 μg L−1 waterborne metformin for 165-days. The weight and length of adult fish were examined, as were effects on the production of some steroid hormones, specifically a significant increase (control females: 0.161 ± 0.023 pg/mg; metformin treated females: 3.42 ± 0.543) in the production of 11-ketotestosterone was observed in adult female medaka. Collectively, these results suggest that current environmental exposure scenarios may be sufficient to cause effects on developing fish. [ABSTRACT FROM AUTHOR]

The alga Cladophora glomerata can erupt in nuisance blooms throughout the lower Great Lakes. Since bacterial abundance increases with the emergence and decay of Cladophora, we investigated the prevalence of antibiotic resistance (ABR) in Cladophora-associated bacterial communities up-gradient and down-gradient from a large sewage treatment plant (STP) on Lake Ontario. Although STPs are well-known sources of ABR, we also expected detectable ABR from up-gradient wetland communities, since they receive surface run-off from urban and agricultural sources. Statistically significant differences in aquatic bacterial abundance and ABR were found between down-gradient beach samples and up-gradient coastal wetland samples (ANOVA, Holm-Sidak test, p < 0.05). Decaying and free-floating Cladophora sampled near the STP had the highest bacterial densities overall, including on ampicillin- and vancomycintreated plates. However, quantitative polymerase chain reaction analysis of the ABR genes ampC, tetA, tetB, and vanA from environmental communities showed a different pattern. Some of the highest ABR gene levels occurred at the 2 coastal wetland sites (vanA). Overall, bacterial ABR profiles from environmental samples were distinguishable between living and decaying Cladophora, inferring that Cladophora may control bacterial ABR depending on its life-cycle stage. Our results also show how spatially and temporally dynamic ABR is in nearshore aquatic bacteria, which warrants further research. [ABSTRACT FROM AUTHOR]

The diatom Didymosphenia geminata (Bacillariophyceae) has garnered increased attention as a nuisance and invasive species in freshwater systems. Historically described as rare yet cosmopolitan, a suspected new variant of D. geminata has the capacity to inundate kilometres of river bottom during a bloom. Unlike most other bloom-forming algae, D. geminata proliferates under high water quality (i.e., low turbidity and low nutrient) conditions. To inform management strategies, the environmental factors and conditions that promote bloom events must be ascertained. Our study of the Bow and Red Deer rivers in southern Alberta, Canada, provides supporting evidence that the mean flow regime is associated with bloom development, based on a significant negative relationship detected between D. geminata biomass and mean discharge (r2 = 0.30). While flow regulation by dams can create the stable flow environment preferred by D. geminata, our results indicate that flow regime (rather than just proximity to dam outflows) is the likely mechanism, in addition to other environmental factors, such as water clarity, temperature, pH, conductivity, and total phosphorus. We discuss the formidable challenges to D. geminata management, particularly along unregulated river reaches, yet also recognize the unique research opportunities that this organism poses for the growing field of invasion biology. [ABSTRACT FROM AUTHOR]