Quantifying Effects and Ingestion of Several Pristine Microplastics in Two Early Life Stages of Freshwater Mussels.

Microplastics have been found in freshwater systems, and in turn have been detected in freshwater bivalves. However, there is limited research that defines the toxicity of bicroplastics to native freshwater bivalves that have long been imperiled in North America. Our objective was to determine whether a suite of pristine microplastics has an adverse effect on two early life stages of unionid freshwater mussels.

Response of stream habitat and microbiomes to spruce budworm defoliation: New considerations for outbreak management.

Defoliation by eastern spruce budworm is one of the most important natural disturbances in Canadian boreal and hemi-boreal forests with annual area affected surpassing that of fire and harvest combined, and its impacts are projected to increase in frequency, severity, and range under future climate scenarios. Deciding on an active management strategy to control outbreaks and minimize broader economic, ecological, and social impacts is becoming increasingly important. These strategies differ in the degree to which defoliation is suppressed, but little is known about the downstream consequences of defoliation and, thus, the implications of management.

Reduction in reproductive activity from degeneration of testicular follicles in Megapitaria squalida (Mollusca: Bivalvia) exposed to metal pollution in the Gulf of California.

Over a reproductive cycle, the prevalence and intensity of degeneration of testicular follicles in Megapitaria squalida collected from the mining port of Santa Rosalia (a highly metal-polluted area), and San Lucas (a less polluted site), Gulf of California, Mexico, were evaluated. At San Lucas, most individuals had a typical testicular structure, and degeneration of testicular follicles was present in 9.5 % of spawning organisms.

Microparticles in Wild and Caged Biota, Sediments, and Water Relative to Large Municipal Wastewater Treatment Plant Discharges.

Anthropogenically modified microparticles including microplastics are present in municipal wastewater treatment plant (WWTP) effluents; however, it is unclear whether biotic exposures are elevated downstream of these outfalls. In the fall of 2019, the present study examined whether microparticle levels in resident fish, environmental samples, and caged organisms were elevated near the Waterloo and Kitchener WWTP outfalls along the Grand River, Ontario, Canada. Wild rainbow darters (Etheostoma caeruleum) were collected from a total of 10 sites upstream and downstream of both WWTPs, along with surface water and sediment samples to assess spatial patterns over an approximately 70-km river stretch.

Spatial patterns of sediment contamination and their influence on benthic infaunal communities in a highly tidal and industrial estuary in Atlantic Canada.

Sediment contamination can be elevated in ports, harbours, and estuaries with legacies of exploitation, negatively impacting infaunal invertebrate communities. Saint John Harbour (45.25° N, 66.

Elements and omega-3 fatty acids in fishes along a large, dammed river.

Damming of a river can trap and elevate levels of sediment-bound elements and alter food web dynamics in created reservoirs. It follows that dams may alter how elements and other nutrients, like the beneficial omega-3 fatty acids (n-3 FAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are accumulated in fish and thus the chemical composition of species above and below this barrier to migration. This study examined the spatial and species differences in contaminants and nutrients in fish from the Wolastoq | Saint John River (New Brunswick, Canada) in association with a large hydroelectric dam (Mactaquac Generating Station; MQGS), a river which supports both recreational fisheries and subsistence fishing by Indigenous communities.

Environmental Risks of Pharmaceutical Mixtures in Aquatic Ecosystems: Reflections on a Decade of Research.

Pharmaceuticals and personal care products (PPCPs) occur as variable mixtures in surface waters receiving discharges of human and animal wastes. A key question identified a decade ago is how to assess the effects of long-term exposures of these PPCP mixtures on nontarget organisms. We review the recent progress made on assessing the aquatic ecotoxicity of PPCP mixtures-with a focus on active pharmaceutical ingredients-and the challenges and research needs that remain.

Temporal and Spatial Trends in Benthic Infauna and Potential Drivers, in a Highly Tidal Estuary in Atlantic Canada.

Unlabelled: Infaunal invertebrate communities of coastal marine sediments are often impacted by human activities, particularly in harbours and estuaries. However, while many studies have attempted to identify the key factors affecting benthic infauna, few have done so for highly energetic tidal estuaries. Samples were collected over a decade (2011-2020) from a series of reference sites in Saint John Harbour (45.

Human health risk assessment of metals and arsenic via consumption of commercial bivalves in the Gulf of California, Mexico.

Although various studies have reported the bioaccumulation of metals in bivalves of commercial interest from the Gulf of California (GC), the risk associated with their consumption remains poorly understood. In this study, our own and bibliographic concentrations of 14 elements in 16 species of bivalves from 23 locations were used to investigate (1) the species-specific and regional accumulation of metals and arsenic in bivalves, (2) the human health risks by age and sex, and (3) the maximum allowable consumption rates (CRlim). The assessments were done according to the US Environmental Protection Agency guidelines.

Elevated Allochthony in Stream Food Webs as a Result of Longitudinal Cumulative Effects of Forest Management.

Unlabelled: The river continuum concept (RCC) predicts a downstream shift in the reliance of aquatic consumers from terrestrial to aquatic carbon sources, but this concept has rarely been assessed with longitudinal studies. Similarly, there are no studies addressing how forestry related disturbances to the structure of headwater food webs manifest (accumulate/dissipate) downstream and/or whether forest management alters natural longitudinal trends predicted by the RCC. Using stable isotopes of carbon, nitrogen and hydrogen, we investigated how: 1) autochthony in macroinvertebrates and fish change from small streams to larger downstream sites within a basin with minimal forest management (New Brunswick, Canada); 2) longitudinal trends in autochthony and food web length compare among three basins with different forest management intensity [intensive (harvest and replanting), extensive (harvest only), minimal] to detect potential cumulative/dissipative effects; and 3) forest management intensity and other catchment variables are influencing food web dynamics.

Using tissue cysteine to predict the trophic transfer of methylmercury and selenium in lake food webs.

The biomagnification of toxic methylmercury (MeHg) and selenium (Se) through aquatic food webs using nitrogen stable isotopes (δN) varies among ecosystems but underlying mechanisms are yet unexplained. Given the strong links between MeHg and thiol-containing amino acids and proteins containing selenocysteine, our hypothesis was that cysteine content is a better predictor of MeHg and Se transfer through lake food webs than δN. Food web samples were collected from six lakes in Kejimkujik National Park, Nova Scotia, Canada, and the regression slopes of log MeHg or Se versus protein-bound cysteine or bulk δN were compared.

Effects of forest management on mercury bioaccumulation and biomagnification along the river continuum.

Forest management can alter the mobilization of mercury (Hg) into headwater streams and its conversion to methylmercury (MeHg), the form that bioaccumulates in aquatic biota and biomagnifies through food webs. As headwater streams are important sources of organic materials and nutrients to larger systems, this connectivity may also increase MeHg in downstream biota through direct or indirect effects of forestry on water quality or food web structure. In this study, we collected water, seston, food sources (biofilm, leaves, organic matter), five macroinvertebrate taxa and fish (slimy sculpin; Cottus cognata) at 6 sites representing different stream orders (1-5) within three river basins with different total disturbances from forestry (both harvesting and silviculture).

Effects of municipal wastewater effluents on the digestive gland microbiome of wild freshwater mussels (Lasmigona costata).

Gut microbial communities are vital for maintaining host health, and are sensitive to diet, environment, and chemical exposures. Wastewater treatment plants (WWTPs) release effluents containing antimicrobials, pharmaceuticals, and other contaminants that may negatively affect the gut microbiome of downstream organisms. This study investigated changes in the diversity and composition of the digestive gland microbiome of flutedshell mussels (Lasmigona costata) from upstream and downstream of two large (service >100,000) WWTPs.

Age, body size, growth and dietary habits: What are the key factors driving individual variability in mercury of lacustrine fishes in northern temperate lakes?

Fish total mercury concentration ([THg]) has been linked to various fish attributes, but the relative importance of these attributes in accounting for among-individual variation in [THg] has not been thoroughly assessed. We compared the contributions of ontogeny (age, length), growth (growth rate, body condition), and food web position (δC, δN) to among-individual variability in [THg] within populations of seven common fishes from 141 north temperate lakes. Ontogenetic factors accounted for most variation in [THg]; age was a stronger and less variable predictor than length for most species.

Comparative Effects of Embryonic Metformin Exposure on Wild and Laboratory-Spawned Fathead Minnow () Populations.

Metformin is routinely detected in aquatic ecosystems because of its widespread use as a treatment for Type 2 diabetes. Laboratory studies have shown that exposure to environmentally relevant concentrations of metformin can alter metabolic pathways and impact the growth of early life stage (ELS) fish; however, it is unknown whether these effects occur in wild populations. Herein, we evaluate whether findings from laboratory studies are representative and describe the relative sensitivities of both populations.

PCB exposure is associated with reduction of endosymbionts in riparian spider microbiomes.

Microbial communities, including endosymbionts, play diverse and critical roles in host biology and reproduction, but contaminant exposure may cause an imbalance in the microbiome composition with subsequent impacts on host health. Here, we examined whether there was a significant alteration of the microbiome community within two taxa of riparian spiders (Tetragnathidae and Araneidae) from a site with historical polychlorinated biphenyl (PCB) contamination in southern Ontario, Canada. Riparian spiders specialize in the predation of adult aquatic insects and, as such, their contaminant levels closely track those of nearby aquatic ecosystems.

Are There Longitudinal Effects of Forest Harvesting on Carbon Quality and Flow and Methylmercury Bioaccumulation in Primary Consumers of Temperate Stream Networks?

Forest harvesting affects dissolved organic matter (DOM) and aqueous mercury inputs as well as the food web structure in small-headwater streams, but how these upstream changes manifest downstream is unclear. To address this uncertainty, we examined DOM quality, autochthony in the caddisfly Hydropsychidae (using δ H), and methylmercury (MeHg) concentrations in stream water and the caddisfly along a longitudinal gradient (first- to fourth-order streams, subcatchments of 50-1900 ha) in paired partially harvested and reference catchments in central Ontario, Canada. Although measures of DOM quality (specific ultraviolet absorbance at 254 nm 2.

Mercury concentrations and stable isotopes (δN and δC) in fish muscle indicate human impacts in tropical coastal lagoons.

Coastal lagoons are essential nursery habitats of many marine fishes, but they are often sites of intense human activities that impact water quality and potentially the fish using these habitats. We compared the variability in nutrient uptake (using δN and δC) and total mercury (THg) levels in juveniles and adults of three common species in two lagoons on the central Mexican coast of the Pacific Ocean during the wet and dry seasons. One of three species, Achirus mazatlanus had higher THg, δN, and δC levels in the lagoon with the greatest wastewater inputs (Barra de Navidad).

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.

Trophodynamics of trace elements in marine organisms from cold and remote regions of southern hemisphere.

Trace metals bioaccumulate in aquatic organisms and some of them biomagnify through food webs, posing a threat to the organisms or their human consumers. Although the trophodynamics of many trace metals is well known in the northern hemisphere, much less is known about metals in aquatic food webs from cold and remote coastal zones of the southern hemisphere. To fill this gap, we investigated the trophodynamics of Al, Co, Cr, Li, Mo, Ni, Sr, and V, which were measured in marine macroinvertebrates and fishes from inshore and offshore locations in each of the Chilean Patagonia and the Antarctic Peninsula area.

Altered microbiomes of aquatic macroinvertebrates and riparian spiders downstream of municipal wastewater effluents.

Municipal wastewater treatment plants (WWTPs) contain numerous contaminants, including antimicrobials, that could affect the composition of the beneficial bacterial communities associated with host aquatic organisms. There is also potential for these effects to transfer to terrestrial predators. Riparian spiders and five families of aquatic macroinvertebrates were collected from sites upstream and downstream of two WWTPs, Waterloo and Kitchener, discharging to the Grand River, Ontario, Canada.

Behavioral and hypothalamic transcriptome analyses reveal sex-specific responses to phenanthrene exposure in the fathead minnow (Pimephales promelas).

Environmental concentrations of the polycyclic aromatic hydrocarbon phenanthrene can become elevated with petroleum processing, industrial activities, and urban run-off into waterbodies. However, mechanisms related to its neurotoxicity in fish are not fully described. Here, we exposed adult fathead minnows (FHM) to an average measured concentration of 202 μg phenanthrene/L over a 47-d period.