Sensitivity of Lake Hypoxia to Atmospheric Physical Forcing: Exploring the First- and Second-order Effects of Air Temperature (AT) and Wind Speed (WS) Changes in Lake Erie (Canada, USA).
First Author: Serghei Bocaniov, Department of Earth and Environmental Sciences and Ecohydrology Group, University of Waterloo, Waterloo, Ontario
Additional Author(s): (Kevin G. Lamb, Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario); (Yerubandi R. Rao, Water Science & Technology, Environment and Climate Change Canada, Burlington, Ontario); (Ralph E. H. Smith, Department of Biology, University of Waterloo, Waterloo, Ontario); (Philippe Van Cappellen, Department of Earth and Environmental Sciences and Ecohydrology Group, Water Institute, University of Waterloo, Ontario).
Abstract: Earth’s climate is changing rapidly. This, in turn, modifies the atmospheric forcing on aquatic environments, including lakes. So far, most of numerical modeling studies of lake sensitivity to changing atmospheric forcing have focused on the first-order effects (i.e., the changes associated with variations in a single parameter at a time). Yet it is recognized that environmental responses, including ecosystem functioning, are dominated by second and even higher order effects (i.e., responses to the simultaneous changes in two or more parameters at a time). Current knowledge of the qualitative and quantitative differences in first- and second-order effects is still very limited. Here, we present a comparative analysis of the first-order versus second-order effects of changing atmospheric forcing by applying a three-dimensional coupled hydrodynamic-ecological model to a large temperate lake, Lake Erie (USA - Canada). Specifically, we analyze the response of hypolimnetic hypoxia, that is, very low bottom water dissolved oxygen (DO) concentrations (< 2 mg L-1), to first-order and second-order changes in air temperature and wind speed. We consider various modified atmospheric forcing scenarios with changes to air temperature from -3 to +3°C, with a 1°C step, and changes in wind speed from -15 to +15%, with a 5% step, relative to the base line conditions (year 2008). For each of the scenarios, the severity and duration of hypoxic conditions are simulated. We present the results arising from the first- and second-order changes and discuss their similarities and differences.
Flow-Through Reactor Experiments to Inform Modelling of Transport and Retention Processes for Particulate Organic Matter in Riverbeds
First Author: Riley Mills, University of Waterloo
Additional Author(s): Riley Hanson Mills (University of Waterloo); Dr. Fereidoun Rezanezhad (University of Waterloo); Ecenur Bulur (University of Wisconsin Madison); Dr. Stephanie Napieralski (University of Wisconsin Madison); Evan Arntzen (Pacific Northwest National Lab); Dr. Steven P. Loheide (University of Wisconsin Madison); Dr. Eric Roden (University of Wisconsin Madison); Dr. Matthew Ginder-Vogel (University of Wisconsin Madison); Dr. Philippe Van Cappellen (University of Waterloo)
Abstract: The infiltration of river water into riverbeds can deliver particulate organic matter (POM: the remains of plants, algae, and other life), which has an important role for transforming nutrients in watersheds. Once POM is degraded to dissolved organic matter (DOM), it can provide a source of carbon, electron donors, and nutrients for microorganisms to use in biogeochemical reactions that drive nutrient cycles. Over the length of a river, these small-scale riverbed processes can have a large cumulative impact on river biogeochemistry, so a better understanding of small-scale POM transport and retention processes in riverbeds could help improve large-scale nutrient cycling models. My research question is ‘how do the magnitude of hydrologic fluxes into riverbeds influence the vertical transport and retention of POM in riverbed sediments?’ My objective is to identify and quantify vertical transport and retention processes for POM in riverbeds under different flow rates using flow-through reactor (FTR) experiments. In FTRs (10 cm length), algae powder (Chlorella, an analog for POM) is applied as a paste on top of 8 cm of saturated quartz sand. I am repeating this experiment at downward vertical flow rates of 5, 10, 15, and 30 mL/h (specific discharge of 0.1, 0.2, 0.3, and 0.6 m/d). To plot breakthrough curves, I determine Chlorella concentrations in effluent by measuring absorbance (at 660 nm wavelength) with a Flexstation Multi-Mode Microplate Reader. To plot depth profiles, I determine the mass of Chlorella retained on sediment in 1 cm depth intervals using the loss-on-ignition method. In this poster, I present breakthrough curves from one of these experiments and outline the associated reactive transport modelling. Transport of POM is modelled by advection, hydrodynamic dispersion, and gravitational settling. Retention of POM is modelled by filtration to sediment and reversible sorption to filtered POM. The results of experiments conducted at a range of flow rates will inform further revisions to the model. It is expected that increasing the flow rate increases the mass of POM retained by filtration, which could result in higher dissolved organic matter (DOM) concentrations and more DOM oxidation in riverbeds. Thus, remobilized POM, DOM, and oxidation products may be returned to rivers during flow reversals, influencing the biogeochemistry of both rivers and riverbeds.
Lake Ice as a Predictor of Algal Biomass in North American Great Lakes
First Author: Michael Dallosch, Univeristy of Waterloo
Additional Author(s): Claude Duguay, University of Waterloo; Homa Kheyrollah Pour, Wilfrid Laurier University
Abstract: "Harmful Algal Bloom (HABs) reports have increased globally, where climate change is considered a primary driver. While the role of temperature and precipitation on bloom formation is well understood on HAB formation, lake ice remains understudied. Reduced ice duration periods may alter algal growth, extent, duration and timing due to earlier light penetration, shifts in mixing, and changes to thermal regimes. Northern lakes are at an elevated risk due to the greater rate of air temperature change at high latitudes. To determine the importance of lake ice in the prediction of HABs, an observational time series (2002-2019) was analyzed utilizing new remote sensing data products provided by the ESA CCI Lakes+ project to determine the potential link between lake ice (lake ice on-off DOY and lake ice duration), lake surface water temperature (LSWT; mean/max, peak LSWT DOY, LSWT anomaly days) and algal biomass parameters (mean and max chlorophyll-a (chl-a, a proxy of algal biomass), high chl-a extent, duration and peak DOY) for five North American Great Lakes (Lake Erie, Lake Winnipeg, Lake Athabasca, Great Slave Lake, and Great Bear Lake).
A mean reduction in lake ice duration of ~0.47-0.57 days per year for northern lakes, with an increase of ~1.05-1.12 µg L-1/yr in mean chl-a concentrations was found. Multiple Linear Regression (MLR) tests were conducted with varying combinations of inputs. Artificial Neural Networks (ANN) were implemented to determine if non-linear functions provided a better predictive performance. The MLR found that LSWT had a greater importance in the prediction of algal biomass parameters, while the ANN provided a stronger predictive performance overall. Northern lakes had relatively lower predictive error (median NRMSE = 0.72) using the ANN compared to that of the southern lakes (median NRMSE = 0.81).
A random forest (RF) model was used to classify annual/seasonal algal bloom pixels using the lake ice and LSWT parameters (accuracy = 83.84% - 95.47%). The preliminary results indicate that the LSWT parameters had the highest reduction in mean accuracy when excluded from the annual RF, however when predicting HABs during early months (March – May), lake ice parameters typically had a higher importance. Through this analysis, ice parameter thresholds can be established to better understand its impact on algal biomass. This research has found that northern lakes typically had better predictive performance when using lake ice and LSWT parameters, and that lake ice parameters show a high importance in the classification of spring HABs."
Application of in situ diffusive gradients in thin-films technique in the laboratory and the field to investigate desorption kinetics of psychoactive drugs in sandy sediment
First Author: Xiaowen Ji. School of Environment and Sustainability, University of Saskatchewan
Additional Author(s): Jonathan K. Challis: Toxicology Centre, University of Saskatchewan, Saskatoon, Canada Jenna Cantin Toxicology Centre, University of Saskatchewan, Saskatoon, Canada Ana S. Cardenas Perez: School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Canada Yufeng Gong: Toxicology Centre, University of Saskatchewan, Saskatoon, Canada Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Canada Department of Environmental Sciences, Baylor University, Waco, Texas, USA John P. Giesy: Toxicology Centre, University of Saskatchewan, Saskatoon, Canada Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Canada Department of Environmental Sciences, Baylor University, Waco, Texas, USA Markus Brinkmann: Toxicology Centre, University of Saskatchewan, Saskatoon, Canada School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Canada Global Institute for Water Security, University of Saskatchewan, Saskatoon, Canada Centre for Hydrology, University of Saskatchewan, Saskatoon, Canada
Abstract: Dynamic processes of organic contaminants in sediments can have important toxicological implications in aquatic systems. The current study used diffusive gradients in thin-films (DGT) devices deployed in sandy sediments both under laboratory conditions spiked with nine antipsychotic drugs (i.e., amitriptyline, bupropion, carbamazepine, citalopram, clozapine, duloxetine, fluoxetine, lamotrigine, and venlafaxine), and under field conditions in riverbank sediments of South Saskatchewan River. Samplers (standard DGT and DGT sediment probes) were deployed for 1 to 30 days in the laboratory and for 1 to 21 days in the field to determine the flux of these compounds to DGT devices, the exchange rates between the porewater and sediment solid phase, and flux at the watersediment interface in the field. The results showed a continuous removal of these drugs to the binding gel and induced a mobile flux from the DGT device to the adjacent sediment solution. A dynamic model, DGT induced fluxes in soils and sediments, was used to derive rate constants of resupply of antipsychotics from solid phase to aqueous phase (response time, Tc) and distribution coefficients for labile antipsychotics. The largest labile pool was found for lamotrigine and carbamazepine and in both spiked and field sediments, where the fastest resupply rates of drugs were also found for carbamazepine and lamotrigine. In the field measurement, the dissolved concentration of antipsychotic drugs declined with sediment depth and the greatest concentrations were observed in the top layer (2 cm). The positive fluxes of all psychotic drugs were found from sediment to surface water. A partial resupply of psychotic drugs from sediment particles to porewater could be seen in both field measurement and laboratory simulation. However, the desorption processes occur within 15 cm sediment depth whereas adsorption was dominant in spiked sediments. Our study implies a dynamic releasing portion of pollutants from natural sediments, which may cause a potential risk for aquatic biota. This process may not be the same under laboratory conditions using spiking compared to exposure in the field. Nevertheless, the mechanism of interaction between sediment properties and different compounds to explain DIFS-derived parameters requires further dedicated studies.
Quantifying the role of reservoirs in altering phosphorus dynamics using a combination of data analysis and process modeling
First Author: Tori Grootjen, University of Waterloo
Additional Author(s): Nandita Basu, University of Waterloo and Ruchi Bhattacharya, University of Waterloo
Abstract: Excess phosphorus (P) from agricultural watersheds promotes eutrophication in downstream aquatic systems. Reservoirs retain P generated from farm fields and protect downstream waters. Reservoirs also act as hotspots for P transformation, as anoxic conditions can facilitate the release of stored P from the lake sediments. The role of inland reservoirs in P speciation at the watershed scale is relatively unexplored. This problem is growing in importance as approximately half of the global river volume is at least moderately impacted by damming, and is projected to reach 93% with all the planned or proposed dams (Grill et al. 2015). Here we use a decade of soluble reactive P (SRP) and total P (TP) concentration data at the inlet and outlet of two reservoirs, Belwood Reservoir and Conestogo Reservoir, in the Grand River Watershed, Canada. The annual SRP and TP percent retention varied at both reservoirs, showing that the reservoirs acted as a sink in some years and as a source in other years. The percent TP retention in Belwood Reservoir varies from -29% to 38%, while percent TP retention in Conestogo Reservoir is generally lower, between -78% to 22%. The SRP retention in Belwood Reservoir varied between -32% and 37%, while SRP retention in Conestogo Reservoir varied between -60% and 27%. Interestingly, the source-sink behaviour is visible for both SRP and TP and they are similar between years. That is, in years that Belwood Reservoir acts as a source of TP, the reservoir often acts as a source of SRP too. At the seasonal scale, we found that both reservoirs increase the proportion of bioavailable P (SRP:TP ratio) from inlet to outlet between April and October. We then built a process-based model to examine the P cycling and sediment-water interactions controlling this speciation of P in the Belwood Reservoir. The model was able to capture downstream SRP export with NSESRP = 0.57-0.86 and TP export with NSETP = 0.60-0.91. The model had difficulty capturing the SRP:TP magnification from inlet to outlet and sediment P accumulation, especially for the first few years of model simulation (2007 - 2012). Model results highlight the role of internal loading during the summer months. As dam construction is on the rise globally, it is critical to understand the impact of reservoirs on the relative reactivity of P in order to mitigate nuisance and potentially harmful algal blooms.
Nitrogen Legacies in the Transboundary Lake Erie Basin
First Author: Meghan McLeod, University of Waterloo
Additional Author(s): Dr. Nandita Basu, University of Waterloo ; Dr. Kimberly Van Meter, Penn State University
Abstract: Lake Erie is a source of drinking water, recreation, and commercial opportunity in the U.S and Canada, making the protection of its water quality essential. In the past decades, Lake Erie's ecosystems have been adversely impacted by recurring toxic algal blooms. These algal blooms are attributed to nitrogen (N) and phosphorus pollution from agricultural activities. Despite recent efforts to reduce N application in the Lake Erie basin, high levels of N concentration persist in surface and groundwater systems. One of the reasons for this apparent stasis in N concentrations is legacy stores of N in landscapes that contribute to lag times in water quality response, even after inputs have ceased. Legacy N is stored in the soil and slow-moving groundwater and makes up a large portion of current N contamination. Quantifying these available legacy N stores is essential for creating nutrient reduction targets. My project aims to quantify N legacies across the entire Lake Erie basin to predict time lags in water quality improvements. To do this, we use a process-based modelling framework, ELEMeNT, to quantify legacy N stores and watershed-scale N dynamics over the past century in multiple sub-watersheds across the basin. Our model results will inform nutrient management practices across the Lake Erie basin by explicitly incorporating legacy dynamics. These proposed management strategies will, ideally, lead to improved water quality across the Lake Erie basin.
Effects of Salinization on lake stratification and nutrient cycling: a case study on Lake Wilcox, a cold temperate urban lake
First Author: Jovana Radosavljevic, Ecohydrology Research Group, University of Waterloo
Additional Author(s): Zahra Akbarzadeh, Ecohydrology Research Group, University of Waterloo; Stephanie Slowinski, Ecohydrology Research Group, University of Waterloo; Fereidoun Rezanezhad, Ecohydrology Research Group, University of Waterloo; Mahyar Shafii, Ecohydrology Research Group, University of Waterloo; William Withers, City of Richmond Hill; and Philippe Van Cappellen, Ecohydrology Research Group, University of Waterloo
Abstract: The application of deicing salts causes salinization of receiving waters, including lakes in urban catchments. Salinization of a lake’s water column increases the water density and, consequently, stabilizes the summer stratification and reduces the chemical exchanges between the epilimnion and hypolimnion. The latter translate in longer and more intense periods of hypolimnetic hypoxia that, in turn, accelerate the internal loading of the limiting nutrient phosphorus (P). These effects of salinization are clearly seen in water chemistry data covering the period 2001-2020 for Lake Wilcox, a shallow kettle lake in the greater Toronto metropolitan area that shows symptoms of eutrophication. The data show statistically significant increases with time of the major cations (potassium, sodium, calcium, and magnesium) and anions (chloride, sulfate, and dissolved inorganic carbon), as well as alkalinity. In addition to the changing major water chemistry, the lake is also experiencing an increase in the fraction of total P (TP) present as dissolved inorganic P (DIP), that is, the most bioavailable pool of P. The changing DIP:TP ratio is driven by the salinization-promoted internal P loading rather than changes in the external P inputs from the watershed. We present a simple mass balance model that reproduces the observed chloride concentration trajectory in the lake. We use the model to simulate the impact of future reductions in de-icing applications in the lake’s watershed. With the future model projections, we assess the likelihood of the lake reaching the salinity threshold that would cause the water column to become permanently stratified.
Importance of nearshore-offshore and alongshore phosphorus exchanges in large lakes: A Lake Erie modeling study
First Author: Zahra Akbarzadeh (University of Waterloo)
Additional Author(s): Sergei Bocaniov (University of Waterloo), Helen Powley (Plymouth Marine Laboratory), Philippe Van Cappellen (University of Waterloo)
Abstract: Nearshore eutrophication is an important unsolved water quality problem in the Laurentian Great Lakes. This research focuses on Lake Erie, a large lake with unique water quality issues that are in part driven by the excess availability of phosphorus (P), including: harmful cyanobacterial blooms in the western basin, nuisance nearshore Cladophora growth in the eastern basin, and hypoxia in the central basin. We developed a simple regionalized P mass balance model for Lake Erie which explicitly accounts for the exchanges of water and P between the offshore and littoral zones. Except for the very shallow western basin, Lake Erie was divided into littoral segments and offshore areas, with the latter consisting of an epilimnion and hypolimnion. The P model includes dissolved and particulate fractions of P in the water column, as well as total P (TP) in the bottom sediments. Mean annual P loadings (2003-2016 averages) from watershed flows and atmospheric deposition, along with the mean annual water exchanges between the different lake compartments estimated from 3D hydrodynamic model simulations, were imposed to the P model. Particular attention was given to quantifying the average littoral-offshore water exchange fluxes within the central and eastern basins lake. The resulting in-lake P exchanges thus comprise littoral-littoral (i.e., alongshore), littoral-offshore, and inter-basin fluxes. The calculations imply that P inputs from offshore waters make up to 20% of the annual TP budget of the littoral segments of the lake, while the remaining 80% is sourced from land runoff, atmospheric deposition, inflow from adjoining littoral segments, and, for the westernmost littoral segments of the central basin, the western basin. The model is applied to assess the long-term effectiveness of land-based P load management strategies in mitigating nearshore eutrophication. For instance, the model scenarios indicate that the 40% reduction in external riverine P loads to the western and central basins decided on by Canada and the US will not yield the desired nearshore P concentrations even after 10 years. Furthermore, based on our analysis of the available monitoring data collected in Lake Erie by different agencies, we recommend that increased efforts be devoted to obtaining more comprehensive P data sets along the littoral zone and filling the data gap on winter season lake biogeochemistry.
Nutrient monitoring and comparison of on-site community science data collection methods for Indigenous water protection
First Author: Jaclyn Porter, University of Saskatchewan
Additional Author(s): Lori Bradford, University of Saskatchewan
Abstract: The climate in the Canadian Prairies is shifting toward extreme weather events are occurring more frequently than in the past, leading to impacts on local ecosystems and communities, such as excessive nutrient loading in freshwater. Nutrient loading is of concern as it affects water quality and safety for Indigenous reserve communities, especially for communities with difficulties treating their water, resulting in harm to their overall health. Due to climate changes and a growing economy, we cannot reliably predict the quality of freshwater resources like before. Differences between normal and adverse weather conditions affect nutrient loading drivers' influential power, furthering the difficulty of predicting water quality. Therefore, nutrient monitoring needs to be a continuous effort that includes impacted residents as part of the solution. Collaboration with community members is a cost-effective and information-rich method for monitoring efforts, benefiting all involved. Unfortunately, there are still misconceptions on the validity of data gathered by citizen scientists. This study builds on the argument of citizen science as a reliable method for environmental research and community involvement, particularly in continuous monitoring projects, by testing the accuracy of two monitoring devices, identifying hotspots, and determining leading factors impacting nutrient inputs in the prairies.
Optimizing environmental DNA detection protocols to generate fish presence data in remote freshwater systems
First Author: Erika A Burton, University of Waterloo, Canada
Additional Author(s): Barbara A Katzenback, University of Waterloo, Canada. Patricija Marjan, University of Calgary, Canada. Gustavo Chiang, Universidad Andres Bello, Chile. Paulina Bahamonde, Universidad de Playa Ancha, Chile. Paul M Craig, University of Waterloo, Canada. Andrew Doxey, University of Waterloo, Canada., John Giesy, University of Saskatchewan, Canada. Mark R Servos, University of Waterloo, Canada
Abstract: To protect freshwater fish communities, basic knowledge of their numbers, distribution, and habitat is required, but this information can be particularly difficult to obtain for remote systems. Remote freshwater systems can experience human impacts but are poorly understood due to lack of access and potential hazards. Rivers draining from the stratovolcano Melimoyu in northern Chilean Patagonia, where limited access, high flows, and considerable river debris makes traditional sampling from boats or wading impractical or dangerous. New biomonitoring techniques such as environmental DNA (eDNA) detection can be used to sensitively and non-invasively obtain data of species presence or even community structure through analysis of water samples. Environmental DNA is DNA derived from organisms but shed into their environment (e.g., via feces, mucous, shed cells). Detection of eDNA may provide an avenue for obtaining data about freshwater communities in remote systems such as Melimoyu. To evaluate the feasibility of eDNA sampling in remote systems, eDNA detection methods were used for three different fish species: invasive brown trout (Salmo trutta) and Atlantic salmon (Salmo salar), and native puye (Galaxias maculatus) in the rivers draining Volcán Melimoyu. Brown trout eDNA was detected at seven sites across four rivers, Atlantic salmon eDNA was not detected at any sample sites, and puye eDNA was detected in one river with high certainty. The efficacy and feasibility of using eDNA detection methods in remote areas was assessed to make recommendations for future eDNA studies at Melimoyu and other remote areas. Establishing best practices for eDNA surveys may allow researcher to gain insight into ecosystems that are poorly characterized and imperiled.
Validation of environmental DNA barcoding assays for Southern Ontario Amphibians
First Author: Cailyn M. Zamora, Dept. of Biology, University of Waterloo, Waterloo, ON, Canada.
Additional Author(s): Nathanael B. J. Harper, Dept. of Biology, University of Waterloo, Waterloo, ON, Canada. Maxwell P. Bui-Marinos, Dept. of Biology, University of Waterloo, Waterloo, ON, Canada. Paul M. Craig, Dept. of Biology, University of Waterloo, Waterloo, ON, Canada. Mark R. Servos, Dept. of Biology, University of Waterloo, Waterloo, ON, Canada. Andrew C. Doxey, Dept. of Biology, University of Waterloo, Waterloo, ON, Canada. John P. Giesy, Dept. of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, SK, Canada. Barbara A. Katzenback, Dept. of Biology, University of Waterloo, Waterloo, ON, Canada.
Abstract: Effective monitoring of populations of amphibians is necessary for conservation and reversing declines in populations of amphibians. Due to diverse life histories, cryptic nature, and low population density of threatened species, current methods of monitoring, such as visual and auditory surveys, are fraught with challenges. Organisms constantly shed biological material resulting in the accumulation of genetic material in the environment, termed environmental DNA (eDNA), which can be collected, concentrated by filtration, and identified and quantified. Environmental DNA barcoding is an emerging, sensitive, method for detection of the presence of species by identification of unique sequences of nucleic acid, specific to a target species, which obviates the need for direct observations of taxa. While eDNA barcoding assays have been designed for 24 Ontario amphibians and validated under laboratory settings (in vitro), these assays have yet to be validated for use with eDNA collected from the field, which poses a barrier to their uptake and application for monitoring efforts by end-users. The goal of this research is to determine if eDNA barcoding is a reliable and efficient method to detect amphibians in vernal pool habitats in Southern Ontario compared to conventional surveys. Target species will include vernal pool obligate breeders, including wood frog, spotted salamander, and species that inhabit various wetland types, including spring peeper, green frog, and American toad. It is hypothesized that eDNA barcoding will provide equal or greater accuracy for detection of the presence/absence of specific amphibians, compared to conventional survey methods. From April to July 2019, conventional (visual/auditory) and eDNA surveys for amphibians in vernal pools were conducted in collaboration with the rare Charitable Research Reserve, Cambridge, ON. Audio recorders collected call data daily at dawn and dusk. Visual surveys were conducted weekly concurrently with collection of eDNA. Three 1-L samples of surface waters water were collected from sites around vernal pools and kept on ice until filtered within 12 hours of collection. Assays to detect eDNA barcodes, based on species-specific sequences were validated for effectiveness and overall efficiency at low concentrations of eDNA. Presence/absence of eDNA for selected species will be compared to results of conventional survey methods. Both methods will be used to assess status and trends in distributions of amphibians on spatial and temporal scales. Results will provide evidence needed to support the uptake of these methods for ongoing monitoring of populations of amphibians by end users in academia, government, and private industry.
Long-term monitoring of algal biomass in Western Lake Ontario using remote sensing and in situ data
First Author: Ali Reza Shahvaran, University of Waterloo
Additional Author(s): Philippe van Cappellen, University of Waterloo & Homa Kheyrollah Pour, Wilfrid Laurier University
Abstract: The shoreline of Western Lake Ontario (WLO) comprises ecologically important wetlands and habitats for aquatic life. It is also borders to the Greater Toronto Area (GTA), one of Canada's largest and most densely populated regions. The WLO receives urban stormwater runoff and effluent from treatment plants that deliver nutrients and sediments to the nearshore zone. The WLO is also threatened by invasive species, including dreissenid mussels that are modifying biogeochemical nutrient cycling in the lake. Therefore, the potential re-eutrophication of Lake Ontario remains a major binational concern. In this study, we focus on reconstructing the eutrophication trajectory in WLO to provide essential knowledge to inform mitigation climate-adaptive strategies to protect the lake. We are using chlorophyll-a (Chl-a) concentration data obtained from remote sensing measurements as an indicator of phytoplankton biomass. One particular challenge in the nearshore waters of WLO is the presence of Cladophora, a submerged nuisance algae. We are currently assembling remote sensing and in situ data time series on surface Chl-a concentrations and submerged aquatic vegetation (SAV) coverage for WLO. Several retrieval algorithms for remote sensing Chl-a in the littoral zone of WLO are being compared and modified. To determine SAV coverage, we are developing a supervised classification approach applied to the available but limited in situ data. For the calibration and validation of the algorithms, we are relying on satellite and drone images (including ETM+, OLI and MSI sensors of Landsat 7,8 and Sentinel 2 satellites) taken over a period of 22 years (from 2000 to 2022). The in-situ dataset does not show a significant trend in Chl-a concentrations in the central WLO, which remains below the oligotrophic threshold (2.6 µg L-1). However, on the nearshore, there are hotspots, such as Hamilton Harbour, that experience eutrophic (20 µg L-1 < Chl-a < 56 µg L-1) or even hypertrophic (Chl-a > 56 µg L-1) conditions. In addition, some of these hotspots exhibit slight increases in Chl-a, emphasizing the importance of long-term monitoring and risk assessments of future blooms in this region.
Mercury Bioaccessibility in Raw and Cooked Tissue from Freshwater Fish Species from the Northwest Territories, Canada
First Author: Sara Packull-McCormick, School of Public Health Sciences, University of Waterloo
Additional Author(s): Alicia Cowan, School of Public Health Sciences, University of Waterloo; Heidi Swanson, Department of Biology, University of Waterloo; Brian Laird, School of Public Health Sciences, University of Waterloo
Abstract: In northern Canada, Indigenous communities rely on locally harvested traditional foods, including fish, which provides them with nutritional, cultural, and social benefits. However, mercury exposure from fish consumption can pose a health risk for populations that consume large amounts of fish or fish with elevated mercury concentrations. The bioaccessiblity of mercury in the tissue of northern Canadian freshwater fish is not yet known. To address this knowledge gap, muscle samples from four commonly consumed freshwater fish species (Lake Trout, Northern Pike, Walleye, and Lake Whitefish) caught from lakes in the Northwest Territories, Canada, were examined. Concentrations and bioaccesibility of total mercury differed significantly among fish species and lakes. Total mercury bioaccessibility for samples run through an in vitro gastro-intestinal digestion model ranged between an average of 56% to 96% for the different fish species and waterbodies. After cooking (pan frying in water), total mercury concentrations were on average 1.5 times higher in the fish muscle tissue. This increase was likely due to moisture loss during the cooking process. However, total mercury bioaccessibility was significantly lower (on average 42% lower) in the cooked samples. Although cooking increased the total mercury concentrations in fish tissue, because the bioaccessibility of total mercury was significantly lower, overall bioaccessible concentrations of total mercury were lower in the cooked samples compared to raw samples. Results from this work provide an important dataset that addresses the gap in the literature regarding total mercury bioaccessibility in northern freshwater fish species. Results also add to the growing literature indicating that mercury bioaccessibility differs by fish species, location, and cooking/preparation method.