Lake Ontario Research Articles

A comprehensive investigation of industrial plastic pellets on beaches across the Laurentian Great Lakes and the factors governing their distribution

Industrial, pre-consumer pellets are a major type of plastics pollution found on shorelines worldwide. This study investigates the distribution and characteristics of plastic pellets accumulated on beaches of the Laurentian Great Lakes of North America and provides a “snapshot” of pellet distribution in a lake system that accounts for 21% of the world's freshwater reserves. We sampled pellets simultaneously from 10m2 quadrats on 66 beaches and characterized the 12,595 pellets collected (average of 19.1 pellets/m2). Forty-two beaches contained pellets and 86% of the pellets were found on three beaches: Rossport (Lake Superior), Baxter (Lake Huron), and Bronte (Lake Ontario). The number of pellets on each beach was compared with factors hypothesized to control their accumulation. In general, positive correlations were found between pellet abundance and watershed population, number of plastic-related industries, and proximity to a river mouth, although for Lake Superior, abundance was related to a train spill that took place over 10 years ago. Beach grain size appears to be related to pellet abundance, with very fine sand, fine sand and medium sand containing the greatest number of pellets. All pellets were visually characterized based on size, color, shape, weathering, and distinguishing traits. The predominant color was white, oblate shapes were most common, and the main distinguishing trait was a dimple. Most pellets showed little evidence of weathering, with the weathered samples mainly from Lakes Erie and Ontario. Lake Ontario pellets were the most varied, with 6/7 shapes, 35/40 colors, and 21/25 distinguishing traits, indicating a wider range of pellet sources compared to the other lakes. Polymer compositions were mainly polyethylene (PE) and polypropylene (PP). Our results will lead to increased recognition of regional pellet pollution in the Great Lakes watershed, thereby motivating change during their production, transport and use.

Shifting trophic control of fishery-ecosystem dynamics following biological invasions.

Increasing human population size and mobility have accelerated the translocation of nonnative species globally, which has become a major threat to conservation of biodiversity and ecosystem services. Introduced species can disrupt species interactions of the recipient ecosystem, triggering system-wide events, and amplify or dampen effects of existing pressures. We show how two pervasive intercontinental invasive consumers in North American lakes, dreissenids (filter-feeding mussels) and Bythotrephes (carnivorous zooplankton), nonlinearly modify consumer-resource dynamics and undermine management interventions to rebuild cold-water predatory fish biomass. Synthesizing 30yr (1986-2015) of lake-wide monitoring data with a dynamic mass-balance food-web model (consisting of 61 species and trophic groups), we reconstructed historical food-web dynamics of Lake Simcoe, a large, temperate lake in Ontario, Canada that has shifted from a turbid to clear-water state. We then analyzed patterns of biomass fluctuations of three recreationally harvested, ecologically connected populations; lake trout (Salvelinus namaycush, a piscivore), lake whitefish (Coregonus clupeaformis, a benthivore), and cisco (C.artedi, a planktivore) before and after the invasions by testing hypotheses on their delayed recoveries under management interventions-predator manipulations (fishery removal and stocking) and nutrient (phosphorus)load reduction. Analyses suggest that fishery harvest primarily regulated early recovery trajectories of the piscivore and planktivore, weakening top-down control prior to the establishment of the invasive consumers. By contrast, the benthivore biomass patterns were shaped, in part, by the invasive mussels (via diet shift), independently of management actions. Although improved water quality (with reduced hypoxia in deeper water) and, in turn, higher macrophyte production are projected to expand the predation refuge for young fish, intensified planktivory (by Bythotrephes) and herbivory (by dreissenids) have triggered shifts in community composition (from pelagic to demersal dominance). These system-wide shifts, in turn, have substantially diminished ecosystem productivity, thereby shrinking fishery yields. Novel consumers can rewire food webs, disrupt energy flows, and suppress predator recoveries, underscoring the need to account for altered ecological reality when sustainably managing fishery resources in invaded ecosystems.

Variable niche breadth in benthic diatoms: Implications of ecological specialization and generalization for community structure

The mechanisms that regulate the composition and structure of biological communities remain poorly understood. Diatom communities have traditionally been assumed to be a collection of r-selected, ecologically redundant generalist taxa with distributions constrained largely by dispersal limitation. Here, we challenge this notion by presenting a novel model that uses distributional data to estimate ecological specialization for groups of diatom taxa. We further develop this model to evaluate relationships among ecological specialization, taxonomic richness, and species’ abundance using field data collected from ancient Lake Matano and the broader Malili Lakes system (Sulawesi, Indonesia), as well as Mazinaw Lake (Ontario, Canada). We demonstrated that diatom niche breadth is highly variable both at the assemblage scale and among genera within assemblages. Ecologically-specialized genera exhibited higher taxonomic richness than their generalist counterparts, suggesting that ecological specialization serves to support the sympatric coexistence of multiple species by limiting competitive interactions among congeneric taxa. This assertion is further supported by species’ abundance patterns, which suggested that resources are evenly partitioned among taxa within specialist genera, while less-specialized genera are composed of taxa with either exceptionally high or exceptionally low abundances reflective of their relative success in competitive interactions with one another. Our findings indicate that the often-overlooked complement of rare taxa within diatom assemblages are in fact the entities that respond most sensitively to environmental conditions and are worthy of far greater consideration in environmental assessment and paleolimnological studies.

Temporal trends in snowfall contribution induced by lake-effect synoptic types

ABSTRACT Using a synoptic classification technique and gridded snow dataset, snowfall was evaluated in the eastern Great Lakes region from 1950-2009 during atmospheric conditions suitable for the development of lake-effect snow. Specific emphases were placed on detailing the long-term changes to snowfall magnitude and frequency, and quantifying changes in the contribution of total snowfall from lake-effect synoptic types. For Lakes Erie and Ontario, snowfall from lake-effect synoptic types represented approximately 48% of total snowfall, and 42% of snowfall days are synoptically lake-effect in nature. Over time, the percentage of total early-season snowfall from lake-effect synoptic types significantly increased downwind of the Lakes, by approximately 0.4% yr-1, corresponding to an increase from approximately 40% lake-effect in the 1950s, to over 60% in the 2000s. This was due, in part, to changes in the frequency of snowfall-producing synoptic types, decreases in the percentage of precipitation falling as snow during non-lake-effect events, and increases in the magnitude of snowfall per lake-effect event. Changes in the proportion of total snowfall from lake-effect processes carries implications to water resources due to differences in snow-water-equivalent between lake-effect snow and snowfall from other mechanisms, such as mid-latitude cyclones.

Spatial segregation of cisco (Coregonus artedi) and lake whitefish (C. clupeaformis) larvae in Chaumont Bay, Lake Ontario

Two of the remaining coregonine species in Lake Ontario, cisco (Coregonus artedi) and lake whitefish (C. clupeaformis), spawn in Chaumont Bay, New York. Larvae co-occur in the spring but are difficult to distinguish morphologically. We applied genetic species identification using microsatellite DNA loci of 268 larvae from known locations in nearshore and offshore habitats in Chaumont Bay to determine the extent of mixing of these species in each habitat. Cisco dominated the larvae (95%) in offshore habitats and lake whitefish dominated (84%) in nearshore habitats, where seven of eight putative hybrids occurred. Habitat segregation between these two species at the larval stage has implications for productivity estimates, as changing environmental conditions may differentially affect shallow and deep waters, larval survival, and possibly subsequent recruitment. Discrimination between cisco and lake whitefish larvae will help to characterize habitat and basic life history needs and to focus research collections. Genetic species identification should be applied to larger samples of larvae to evaluate changes in larval distributions and associations with environmental conditions.

Using visible near-infrared reflectance spectroscopy (VNIRS) of lake sediments to estimate historical changes in cyanobacterial production: potential and challenges

Cyanobacterial blooms are increasing worldwide and have negative impacts on aquatic ecosystems and the services they provide to human societies. A lack of long-term environmental monitoring data, however, has prevented the development of a baseline perspective against which drivers of the increasing frequency and severity of cyanobacterial blooms can be identified. In this study, we evaluate application of spectroscopy-based models to infer historical trends in cyanobacterial abundance from lake sediment cores. Using an amendment series (n = 15) of a sediment matrix spiked with increasing amounts of mixed cyanobacterial culture from 0 to 50 parts per thousand (‰), taxonomically diagnostic carotenoids were measured using visible near-infrared reflectance spectroscopy (VNIRS) and conventional but more costly and time-consuming high-performance liquid chromatography (HPLC). A partial least squares regression model was developed to correlate amendment series VNIR spectra to ‰ of added cyanobacteria. Despite challenges in differentiating carotenoid pigments because of overlapping absorption peaks, applications of the resulting 2-component model (r2 = 0.93, RMSEP = 0.23‰) to sediment cores from four Ontario lakes yielded temporal trends that were significantly correlated with downcore HPLC measures of cyanobacterial pigments in three out of four cases. Although our method is simplistic and may be improved in the future with more complex algorithms employing derivative analysis, we present our results as a possible stepping-stone towards spectral reconstruction of cyanobacterial production. Our study provides proof-of-concept that refinement of a method applying VNIRS to detect cyanobacterial carotenoids in lake sediments has the potential to be an important, rapid and non-destructive assessment tool for research and management of cyanobacterial blooms.

The Guthrie Boulder: A Forgotten Monument to Anesthesia in Chicago.

The Guthrie Boulder: A Forgotten Monument to Anesthesia in Chicago.

Road Salt Impacts Freshwater Zooplankton at Concentrations below Current Water Quality Guidelines.

Widespread use of NaCl for road deicing has caused increased chloride concentrations in lakes near urban centers and areas of high road density. Chloride can be toxic, and water quality guidelines have been created to regulate it and protect aquatic life. However, these guidelines may not adequately protect organisms in low-nutrient, soft water lakes such as those underlain by the Precambrian Shield. We tested this hypothesis by conducting laboratory experiments on six Daphnia species using a soft water culture medium. We also examined temporal changes in cladoceran assemblages in the sediments of two small lakes on the Canadian Shield: one near a highway and the other >3 km from roads where salt is applied in the winter. Our results showed that Daphnia were sensitive to low chloride concentrations with decreased reproduction and increased mortality occurring between 5 and 40 mg Cl-/L. Analysis of cladoceran remains in lake sediments revealed changes in assemblage composition that coincided with the initial application of road salt in this region. In contrast, there were no changes detected in the remote lake. We found that 22.7% of recreational lakes in Ontario have chloride concentrations between 5 and 40 mg/L suggesting that cladoceran zooplankton in these lakes may already be experiencing negative effects of chloride.

How much boreal lake shoreline is burned by wildfire? Implications for emulating natural disturbance in riparian forest management

Understanding of post-fire residual vegetation patterns is important when shoreline vegetation management aims to emulate natural disturbance (END) patterns. To assess the impacts of fire, lake and lakeshed sizes on the burning pattern of shorelines and lakesheds, we quantified the burned shorelines and post-fire residual vegetation patterns in the lakesheds of 123 lakes of Ontario affected by 26 wildfires between 2005 and 2007. We used ArcGIS and Ontario’s Enhanced Forest Resources Inventory (eFRI) GIS data to digitize burn patterns. The lake catchments for all lakes were delineated using ArcGIS via lake, river, and elevation data from the Integrated Hydrology geodatabase (MNRF, 2016). The shorelines of fire impacted lakes were generated from the eFRI polygon feature classes, and the polylines were then split according to the digitized burn pattern polygons by running a geometric intersection with these data. The results of this study show that the percentages of burned shorelines and lakesheds are positively correlated with the size of fire and negatively correlated with the sizes of lake and lakeshed. However, irrespective of the size of fire, lake or lakeshed, shorelines are not left completely unburned, which is contrary to existing practice of retaining fixed-width shoreline buffers. It may imply that under END based management, forest harvesting can be possible up to the shorelines in some areas of the landscapes that are left unharvested under a fixed-width riparian buffer management system. However, areas of strong hydrological connectivity between land and water serve as biogeochemical control points and require protection from disturbance during forest management planning and operations. We suggest that GIS-based models developed based on the hydrological and topographical features associated with the unburned shorelines and lakesheds might be useful to predict shoreline residual forest pattern and facilitate END based shoreline forest management.

Chemical Analysis of Surface-Level Ozone Exceedances during the 2015 Pan American Games

Surface-level ozone (O3) continues to be a significant health risk in the Greater Toronto Hamilton Area (GTHA) of Canada even though precursor emissions in the area have decreased significantly over the past two decades. In July 2015, Environment and Climate Change Canada (ECCC) led an intensive field study coincident with Toronto hosting the 2015 Pan American Games. During the field study, the daily 1-h maximum O3 standard (80 ppbv) was exceeded twice at a measurement site in North Toronto, once on July 12 and again on July 28. In this study, ECCC’s 2.5-km configuration of the Global Environmental Multi-scale (GEM) meteorological model was combined with the Modelling Air-quality and CHemistry (MACH) on-line atmospheric chemistry model and the Town Energy Balance (TEB) urban surface parameterization to create a new urban air quality modelling system. In general, the model results showed that the nested 2.5-km grid-spaced urban air quality model performed better in statistical scores compared to the piloting 10-km grid-spaced GEM-MACH model without TEB. Model analyses were performed with GEM-MACH-TEB for the two exceedance periods. The local meteorology for both cases consisted of light winds with the highest O3 predictions situated along lake-breeze fronts. For the July 28 case, O3 production sensitivity analysis along the trajectory of the lake-breeze circulation showed that the region of most efficient O3 production occurred in the updraft region of the lake-breeze front, as the precursors to O3 formation underwent vertical mixing. In this updraft region, the ozone production switches from volatile organic compound (VOC)-sensitive to NOx-sensitive, and the local net O3 production rate reaches a maximum. This transition in the chemical regime is a previously unidentified factor for why O3 surface-level mixing ratios maximize along the lake-breeze front. For the July 12 case, differences between the model and observed Lake Ontario water temperature and the strength of lake-breeze opposing wind flow play a role in differences in the timing of the lake-breeze, which impacts the predicted location of the O3 maximum north of Toronto.

Modeling the ice-attenuated waves in the Great Lakes

A partly coupled wave-ice model with the ability to resolve ice-induced attenuation on waves was developed using the Finite-Volume Community Ocean Model (FVCOM) framework and applied to the Great Lakes. Seven simple, flexible, and efficient parameterization schemes originating from the WAVEWATCH III® IC4 were used to quantify the wave energy loss during wave propagation under ice. The reductions of wind energy input and wave energy dissipation via whitecapping and breaking due to presence of ice were also implemented (i.e., blocking effect). The model showed satisfactory performance when validated by buoy-observed significant wave height in ice-free season at eight stations and satellite-retrieved ice concentration. The simulation ran over the basin-scale, five-lake computational grid provided a whole map of ice-induced wave attenuation in the heavy-ice year 2014, suggesting that except Lake Ontario and central Lake Michigan, lake ice almost completely inhibited waves in the Great Lakes under heavy-ice condition. A practical application of the model in February 2011 revealed that the model could accurately reproduce the ice-attenuated waves when validated by wave observations from bottom-moored acoustic wave and current profiler (AWAC); moreover, the AWAC wave data showed quick responses between waves and ice, suggesting a sensitive relationship between waves and ice and arguing that accurate ice modeling was necessary for quantifying wave-ice interaction.

Evidence for freshwater residency among Lake Ontario Atlantic salmon (Salmo salar) spawning in New York

Prior to their extirpation around 1900 CE, Lake Ontario hosted the world’s largest freshwater Atlantic salmon (Salmo salar) fishery. Due to their early disappearance, questions remained about fundamental aspects of the species’ biology, such as whether they belonged to sea-run (anadromous) or freshwater resident (potamodromous) ecotypes. Recent isotopic analyses have demonstrated that the complex of Atlantic salmon populations spawning in tributaries emptying along Lake Ontario’s northern shores were potamodromous. However, no evidence has yet been gathered for Atlantic salmon migratory behaviour from Lake Ontario’s southeastern region, where historical observations suggest both anadromous and potamodromous populations may have spawned. Here, we provide the first results for isotopic analyses of bone collagen from seven fish bones from archaeological sites (c. 1427 to 1600 CE) identified as Atlantic salmon through ancient DNA and zooarchaeological analyses. The results of the isotopic analyses confirm that at least some of the salmon spawning in tributaries emptying into Lake Ontario’s southeastern shores were also potamodromous. Although further analyses are needed, this suggests anadromy may have been completely absent in Lake Ontario’s complex of Atlantic salmon populations in recent centuries.

Tracking ∼200 years of water quality in Muskrat Lake, a eutrophic lake trout lake in Ontario (Canada) with cyanobacterial blooms

Simmatis B, Nelligan C, Rühland KM, Jeziorski A, Castro V, Paterson AM, Smol JP. 2020. Tracking ∼200 years of water quality in Muskrat Lake, a eutrophic lake trout lake in Ontario (Canada) with cyanobacterial blooms. Lake Reserv Manage. 36:260–277. Muskrat Lake is a deep (64 m), eutrophic lake in southeastern Ontario, Canada, that supports a natural lake trout population. Frequent algal blooms and low deep-water dissolved oxygen concentrations have generated management concerns. Based on anecdotal reports, algal blooms first occurred in the 1920s. Concern regarding recreational activities has escalated since the early 1980s. Monitoring records for total phosphorus (TP) and dissolved oxygen concentrations are sparse, requiring paleolimnological methods to extend our knowledge of past lake conditions. We inferred trends in past whole-lake primary production using visual-range spectroscopy-inferred chlorophyll a, nutrients using diatom assemblage changes, and end-of-summer volume-weighted hypolimnetic oxygen concentrations (VWHO) using chironomids to assess environmental conditions in Muskrat Lake over the past ∼200 years. Diatom taxa indicative of mesotrophic conditions were present throughout the sedimentary record, which suggests that Muskrat Lake was moderately productive before European settlement, with conditions worsening somewhat after ca. 1920, following land clearance and agricultural development. Chironomid-inferred VWHO trends suggest that the hypolimnion was not naturally well oxygenated, but deep-water oxygen levels declined further after ca. 1900 following European settlement. After ca. 1990, changes in diatom assemblage composition were consistent with climate-mediated increases in thermal lake properties, which might have contributed to cyanobacterial dominance. Whole-lake primary production increased after ca. 1900 and peaked ca. 1960, remaining stable until ca. 2006, after which it declined. Overall, Muskrat Lake has been productive over the past ∼200 years, but the cumulative effects of changes in nutrient loading and mixing patterns should be considered in future management decisions.

An investigation of 129I from regional nuclear fuel reprocessing in the terrestrial sediments of Lake Ontario

129I (T1/2 = 15.7 Ma) concentrations were measured in sediments from Lake Ontario, whose drainage basin contains a former nuclear fuel reprocessing facility. Three archived sediment cores had 129I concentrations from approximately 1 × 105 atoms/g in deeper sections to 1 × 109 atoms/g at the surface, elevated above the nuclear weapons testing signal for North America. 129I concentrations and 129I/127I ratios increase upwards and indicate a significant anthropogenic influence, with the vast majority of the 129I in each core being found near the surface. There is also some penetration into deeper sediment layers, with pre-nuclear 129I/127I ratios only reached at depths of 10–13 cm. The data show that Lake Ontario sediments are a repository for anthropogenic 129I from regional nuclear fuel reprocessing. The results point to the mobilization of iodine from anoxic, deeper sediment layers, shedding light on the geochemical behavior of iodine isotopes in Lake Ontario’s sediments.

Selection of a metal ligand modified DNAzyme for detecting Ni2+

Nickel is a highly important metal, and the detection of Ni2+ using biosensors is a long-stand analytical challenge. DNA has been widely used for metal detection, although no DNA-based sensors were reported for Ni2+. DNAzymes are DNA-based catalysts, and they recruit metal ions for catalysis. In this work, in vitro selection of RNA-cleaving DNAzymes was carried out using a library containing a region of 50 random nucleotides in the presence of Ni2+. To increase Ni2+ binding, a glycyl–histidine-functionalized tertiary amine moiety was inserted at the cleavage junction. A representative DNAzyme named Ni03 showed a high cleavage yield with Ni2+ and it was further studied. After truncation, the optimal sequence of Ni03l could bind one Ni2+ or two Co2+ for catalysis, while other metal ions were inactive. Its cleavage rates for 100 μM Ni2+ reached 0.63 h−1 at pH 8.0. A catalytic beacon biosensor was designed by labeling a fluorophore and a quencher on the Ni03l DNAzyme. Fluorescence enhancement was observed in the presence of Ni2+ with a detection limit of 12.9 μM. The sensor was also tested in spiked Lake Ontario water achieving a similar sensitivity. This is another example of using single-site modified DNAzyme for sensing transition metal ions.

Use of environmental DNA to detect Eastern Sand Darter ( Ammocrypta pellucida Putnam, 1863) in large Laurentian Great Lakes embayments

A single-species environmental DNA (eDNA) method was developed to sample for a small, benthic rare species, Eastern Sand Darter (Ammocrypta pellucida Putnam, 1863) in two large Lake Ontario embayments. Summer water sampling allowed for: (a) surveys of habitats (Wellers Bay) where traditional fish sampling gear could not be used; and, (b) a comparison between eDNA and seining-based detection probabilities at known occupied habitats (West Lake). In 2018, replicate (n = 3) 1 L water samples were collected from 90 Wellers Bay sites and 71 West Lake sites. A site-occupancy model, a hierarchical logistic regression model, was fitted to determine site occupancy, sample occupancy (presence of Eastern Sand Darter DNA in a water sample) and probability of detection (p) based on replicate quantitative polymerase chain reaction (qPCR) results for each water sample. Eastern Sand Darter was detected at 10 West Lake sites, but not from Wellers Bay. Mean site occupancy was 0.31 (0.12–0.70; 95% CLs), mean sample occupancy was 0.28 (0.09–0.58; 95% CLs), and mean detection probability in a subsample (i.e., successful qPCR amplification) given it was present was 0.40 (0.25–0.55; 95% CLs). While the eDNA method successfully detected Eastern Sand Darter from known occupied areas in West Lake, it was not more effective for assessing local site occupancy than traditional sampling methods, such as the seine.

Anthropocene geochemistry of metals in sediment cores from the Laurentian Great Lakes.

Geochemical analyses applied to lake sedimentary records can reveal the history of pollution by metals and the effects of remedial efforts. Lakes provide ideal environments for geochemical studies because they have steady deposition of fine grained material suitable for fixation of pollutants. The Laurentian Great Lakes are the most studied system in this field, and they have well-preserved chronological profiles. To date, this important system has been considered in parts for inorganic geochemistry, hampering basin-wide conclusions regarding metal contamination. We filled spatial and temporal gaps in a comprehensive geochemical analysis of 11 sediment cores collected from all five Great Lakes. Hierarchical cluster analysis of all Great Lakes samples divided the metal analytes into five functional groups: (1) carbonate elements; (2) metals and oxides with diverse natural sources, including a subgroup of analytes known to be anthropogenically enriched (Cd, Pb, Sn, Zn, and Sb); (3) common crustal elements; (4) metals related to coal and nuclear power generation; and (5) all of the co-occurring rare earth elements. Two contamination indices (Igeo and EF) applied to sedimentary metals indicated that Na, Co, Mn, Cd, Pb, Ta, and Cu were each, at some point during the Anthropocene, the most enriched metal pollutants in Great Lakes sediments. Land uses correlated with the metal analytes, such as increases in contaminant metals with the rise in catchment population and increases in carbonate elements (e.g. Ca) with agriculture. Certain contamination trends were observed basin-wide, such as for the atmospheric pollutant Pb, which followed a rise associated with fossil fuel combustion and a decline following the ban of leaded gasoline. Other trends were lake-specific, such as recent high concentrations of Na in Lake Superior, likely due to road salt applications, and a late-20th-century peak in Ca associated with algal whiting events in Lake Ontario. Some metals exceeded guidelines for sediment quality, in some cases prior to European settlement of the basin, indicating that a paleolimnological context is important for appropriate management of sediment contamination. The Great Lakes are sensitive to environmental changes such as pollution by metals, and it is clear that while there has been remedial success, results from the uppermost intervals of cores indicate ongoing problems.

Halogenated organic contaminants of concern in urban-influenced waters of Lake Ontario, Canada: Passive sampling with targeted and non-targeted screening

Passive samplers are useful tools for monitoring hydrophobic, persistent, and potentially bioaccumulative contaminants in the environment. In this study, low density polyethylene passive samplers were deployed in urban-influenced and background nearshore freshwaters of northwestern Lake Ontario and analyzed for a broad range of both legacy halogenated organic contaminants (HOCs) and halogenated flame retardants (HFRs). Non-targeted analysis was conducted for screening additional halogenated substances. For most compounds, concentrations were greatest in the industrialized Hamilton Harbour and more generally at sites that have stronger influences of wastewater effluent discharges and stormwater run-off through rivers and creeks. Polychlorinated biphenyls (PCBs) remain the dominant class of HOCs in water, with dissolved-phase concentrations ranging from 10 to 4100 pg/L (ΣPCBs), followed by polybrominated diphenylethers (ΣPBDEs; 14–960 pg/L) and the organochlorine pesticides (OCPs; 22–290 pg/L). Several non-PBDE brominated flame retardants (nBFRs) and chlorinated Dechlorane-related compounds were detected, with hexabromocyclododecanes (ΣHBCDD; sum of 3 diastereoisomers) the most abundant (1.0–21 pg/L). Non-targeted screening of samples by high resolution mass spectrometry using Kendrick mass defect plots for data analysis indicated that several other halogenated compounds were present in waters at relatively high abundances compared to the flame retardants, based on semi-quantitative estimates. These included methyl-triclosan, four halogenated anisoles (2,4,6-tribromoanisole, dimethyl-trichloroanisole, pentachloroanisole, and pentachlorothioanisole), and pentachloro-aniline. Dissolved-phase methyl-triclosan was estimated to contribute up to approximately 40% of the summed target HOC concentrations. Polyethylene passive samplers provided an excellent medium for both non-targeted screening of HOCs not currently included in monitoring programs and tracking brominated and chlorinated chemicals slated for reductions in uses and emissions through international (Stockholm Convention) and binational (Great Lakes) agreements.

Concentrations and Long-Term Temporal Trends of Hexabromocyclododecanes (HBCDD) in Lake Trout and Walleye from the Great Lakes.

Hexabromocyclododecane (HBCDD) is a hazardous, persistent, bioaccumlative brominated flame retardant. To investigate how its use has affected the Great Lakes, total HBCDD (∑HBCDD) concentrations and temporal trends in homogenized whole fish samples from the Great Lakes region (1978 to 2016) were determined. ∑HBCDD concentrations (ng/g ww) for each lake are Erie (0.49-2.60), Ontario (3.12-8.90), Michigan (3.91-9.01), Superior (5.69-13.1), and Huron (5.57-13.7). Early years (1978 to 1992) showed no significant trend. However, recent trends (2004 to 2016) suggest concentrations are increasing in Lakes Erie and Ontario, decreasing in Lakes Superior and Michigan, and not changing in Lake Huron. Decreasing trends for Lakes Superior and Michigan are likely the result of decreased usage of the compound globally, regionally, and locally. For the other lakes, increasing or zero trends are consistent with food web changes due to invasive species and climate change, which has caused more intense storms and less ice cover leading to increased sediment resuspension.

Investigating the sex-selectivity of a middle Ontario Iroquoian Atlantic salmon (Salmo salar) and lake trout (Salvelinus namaycush) fishery through ancient DNA analysis

Prior to European settlement, Indigenous peoples sustainably harvested Atlantic salmon (Salmo salar) and lake trout (Salvelinus namaycush) from Lake Ontario for centuries. Previous studies have suggested Indigenous peoples were able to maintain the productivity of Atlantic salmon and lake trout fisheries in the Great Lakes region through the use of resource management strategies. Since males tend to be the surplus sex among salmonids, one way in which Indigenous peoples could have managed Atlantic salmon and lake trout stocks was through the preferential harvesting of males. Here, we sought to investigate whether Indigenous peoples traditionally used sex-selective fishing to manage Lake Ontario Atlantic salmon and lake trout stocks. To address this question, we modified a DNA-based sex identification method developed for ancient Pacific salmonid (Oncorhynchus spp.) remains to make it applicable to archaeological Atlantic salmonid (Salmo spp.) and char (Salvelinus spp.) remains. This method assigns sex identities to samples through two PCR assays that co-amplify a fragment of the Y-specific salmonid master sex-determining gene (sexually dimorphic on the Y-chromosome gene) and an internal positive control, consisting of a fragment of the mitochondrial D-loop or nuclear clock1b gene. We applied this method to 61 Atlantic salmon and lake trout remains from the Antrex site (AjGv-38), a Middle Ontario Iroquoian (ca. CE 1250 to 1300) village located in the Lake Ontario watershed. Using this method, we successfully assigned sex identities to 51 of these remains (83.61% success rate), highlighting our method’s sensitivity and efficacy. Statistical analyses indicate neither the aggregate sex ratio nor the sex ratios obtained for the individual species were male-biased. This suggests Antrex’s Middle Ontario Iroquoian inhabitants probably did not practice male-selective fishing for Atlantic salmon or lake trout.