Souris River Research Articles

Interactive effects of nanoplastics, multi-contaminants, and environmental conditions on prairie aquatic ecosystems: A factorial composite toxicity analysis within a Canadian context

Limited data exist on the interactions between nanoplastics (NPs) and co-contaminants under diverse environmental conditions. Herein, a factorial composite toxicity analysis approach (FCTA) was developed to analyze the time-dependent composite effects of NPs (0 ∼ 60 mg/L), copper (Cu, 0.2 ∼ 6 mg/L) and phenanthrene (PHE, 0.001 ∼ 1 mg/L) on microalgae under diverse pH (6.7 ∼ 9.1), dissolved organic matter (DOM, 1.5 ∼ 25.1 mg/L), salinity (1 ∼ 417 mg/L) and temperature (23 ∼ 33 °C) within the Canadian prairie context. The toxic mechanism was revealed by multiple toxic endpoints. The combined toxicity of NPs, Cu and PHE within prairie aquatic ecosystems was assessed by the developed FCTA-multivariate regression model. Contrary to individual effects, NPs exhibited a promotional effect on microalgae growth under complex environmental conditions. Although Cu and PHE were more hazardous, NPs mitigated their single toxicity. Environmental conditions and exposure times significantly influenced the main effects and interactions of NPs, Cu and PHE. The synergistic effect of NPs*Cu and NPs*PHE on microalgae growth became antagonistic with increased pH or DOM. Microalgae in the Souris River, Saskatchewan, were projected to suffer the most toxic effects. Our findings have significant implications for the risk management of NPs.

Toxicity and mechanism of nanoplastics to phytoplankton in high-latitude aquatic ecosystems of Canadian prairie: Effects of multiple environmental factors

The potential ecological risks of nanoplastics (NPs) may be inaccurately assessed in some studies as they fail to consider the impact of environmental factors and their interactive effects. Here, the effects of six representative environmental factors (N, P, salinity, DOM (dissolved organic matter), pH and hardness) on NPs' toxicity and mechanism to microalgae are investigated based on the surface water quality data in Saskatchewan watershed, Canada. Our 10 sets of 26–1 factorial analysis reveal the significant factors and their interactive complexity towards 10 toxic endpoints from cellular and molecular levels. This is the first time to study the toxicity of NPs to microalgae under interacting environmental factors in high-latitude aquatic ecosystems of Canadian prairie. We find that microalgae become more resistant to NPs in N-rich or higher pH environments. Surprisingly, with the increase of N concentration or pH, the inhibitory effect of NPs on microalgae growth even became a promotion effect with the decreased inhibition rate from 10.5 % to −7.1 % or from 4.3 % to −0.9 %, respectively. Synchrotron-based Fourier transform infrared spectromicroscopy analysis reveals that NPs can induce alterations in the content and structure of lipids and proteins. DOM, N*P, pH, N*pH and pH*hardness have a statistically significant effect on NPs' toxicity to biomolecular. The toxicity levels of NPs across Saskatchewan watersheds are evaluated and we find that NPs could have the greatest inhibition on microalgae growth in Souris River. Our findings indicate that multiple environmental factors should be considered during the ecological risk assessment of emerging pollutants.

EELGRASS BED MAPPING WITH MULTISPECTRAL UAV IMAGERY IN ATLANTIC CANADA

Abstract. Eelgrass (Zostera marina L.) is a marine angiosperm that grows throughout coastal regions in Atlantic Canada. This study aimed to assess the capability of UAV multispectral imagery to map the presence of eelgrass beds within two estuaries in Atlantic Canada (Souris River and Richibucto River). The images were mosaicked using Agisoft and calibrated in reflectance. The corrected images were classified using a non-parametric supervised classifier (Random Forests). The input features of the classification were the UAV band reflectance and associated bathymetric ratios and vegetation indices. The resulting maps were compared with sonar data. The overall validation accuracy for presence/absence was 91.30% with the Souris image and 86.92%% with the Richibucto images. The limitations of the study are also presented.

EELGRASS MAPPING WITH SENTINEL-2 AND UAV DATA IN PRINCE EDWARD ISLAND (CANADA)

Abstract. Eelgrass (Zostera marina L.) is a marine angiosperm that grows throughout coastal regions in Atlantic Canada. Eelgrass beds provide a variety of important ecosystem services, and while it is considered an important marine species, little research has been done to understand its distribution and location within Atlantic Canada. The purpose of this study was to assess the capability of Sentinel-2 and UAV imagery to map the presence of eelgrass beds within the Souris River in Prince Edward Island. Both imageries were classified using the non-parametric Random Forests (RF) supervised classifier and the resulting classification was validated using sonar data. The Sentinel-2 classified image had a lower validation accuracy at 77.7%, while the UAV classified image had a validation accuracy of 90.9%. The limitations of the study and recommendations for future work are also presented.

A two-stage multiple-point conceptual model to predict river stage-discharge process using machine learning approaches

Abstract Due to the complex nature of river stage-discharge process, the present study tried to develop a unique strategy to predict it precisely. The proposed conceptual strategy has some advantages to cover the shortcomings. First, it uses one model instead of several models to predict multiple points instead of one point. On the one hand, the constructed model was inspired by physical-based model (to include time-space attributes of the catchment). On the other hand, ensemble empirical mode decomposition algorithm (EEMD), wavelet transform (WT), and mutual information (MI) were employed as a hybrid pre-processing approach conjugated to support vector machine. For this end, a conceptual strategy (multi-station model) was developed to forecast the Souris River discharge more accurately. The strategy used herein was capable of covering uncertainties and complexities of river discharge modeling. First, a classic model along with WT was performed to predict the 1-day-ahead river discharge for each single station. Therefore DWT-EEMD and feature selection were used for decomposed subseries using MI to be employed in conceptual models. In the proposed feature selection method, some useless subseries were deleted to achieve better performance. The results approved efficiency of the proposed WT-EEMD-MI approach to improve accuracy of different modeling strategies.

Prediction of River Stage-Discharge Process Based on a Conceptual Model Using EEMD-WT-LSSVM Approach

This study proposed a hybrid pre-processing approach along with a conceptual model to enhance the accuracy of river discharge prediction. In order to achieve this goal, Ensemble Empirical Mode Decomposition algorithm (EEMD), Wavelet transform (WT) and Mutual Information (MI) were employed as a hybrid pre-processing approach conjugated to Least Square Support Vector Machine (LSSVM). For this end, a conceptual strategy (multi-station model) was developed to forecast the Souris River discharge more accurately. The strategy used herein was capable of covering uncertainties and complexities of river discharge modeling. At first a classic model along with WT was performed to predict the one-day-ahead river discharge for the each single station. Based on the results, db4 and decomposition level equal to 5 (db(4,5)) presented a better performance among selected mother wavelets for all hydrometric station. Therefore db(4,5) and EEMD was coupled and feature selection was performed for decomposed sub-series using MI to be employed in conceptual models. In the proposed feature selection method, some useless sub-series were omitted to achieve better performance. Results approved efficiency of the proposed WT-EEMD-MI approach to improve accuracy of different modeling strategies.

A multi-proxy study of changing environmental conditions in a Younger Dryas sequence in southwestern Manitoba, Canada, and evidence for an extraterrestrial event

AbstractMulti-proxy analyses of a sequence spanning the Younger Dryas (YD) in the Glacial Lake Hind basin of Manitoba provides insight into regional paleohydrology and paleovegetation of meltwater rivers and lakes spanning >4000 yr; the sequence is controlled by 25 new accelerator mass spectrometry ages. This lake, dammed by the Laurentide Ice Sheet, overflowed into Lake Agassiz. The pre-YD interval records rapid sedimentation from meltwaters that headed in proglacial lakes in the Canadian Prairies that are known to have been catastrophically released when ice or sediment barriers were breached. Pollen in this phase is dominated by pre-Quaternary forms eroded from Paleocene bedrock. At the onset of the YD at ~12.8 cal ka, the sudden appearance of concentrations of nanodiamonds, high-temperature magnetic spherules, platinum, and iridium provide evidence of an extraterrestrial (ET) event that others have identified at more than 40 sites in North America. Major changes in oceans and climate, and the catastrophic outflow of nearby Lake Agassiz at the onset of the YD, may be related. Lower water levels and a reduction of Souris River inflow to Lake Hind followed, which are reflected by more clayey and organic-rich sediments and a decrease in pre-Quaternary palynomorphs. This may have resulted from the deepening of river valleys caused by the release of meltwater triggered by the ET event. Wetlands then began to develop, leading to peat deposition from 12.3 to 11 cal ka. This was followed by a fluvial episode depositing sand and then by increased Holocene aridity that resulted in accumulation of a thick sequence of dune sands. A dry woodland environment with a mix of conifers (especially Picea and Larix) and deciduous trees (especially Populus and Quercus) covered the uplands from ~13 to 10 cal ka.

Identification of native and non-native grass shrimps Palaemon spp. (Decapoda: Palaemonidae) by citizen science monitoring programs in Atlantic Canada

Grass shrimp collected by the Community Aquatic Monitoring Program (CAMP) in estuaries of the southern Gulf of St. Lawrence, Canada were previously assumed to be the native Palaemon vulgarisSay, 1818. Taxonomic identification of grass shrimps from CAMP estuaries revealed most individuals were P. vulgaris, but several from the Souris River and Trout River estuaries in Prince Edward Island (PEI) belong to the European species P. adspersusRathke, 1837. We provide the first documented presence of P. adspersus in PEI estuaries, extending its known range in Atlantic Canada from coastal Newfoundland and the Magdalen Islands. Boat traffic was probably responsible for the introduction of P. adspersus. The results highlight the importance of community-based monitoring in coastal ecology.

Transboundary Environmental Governance across the World's Largest Border ed. by Stephen Brooks and Andrea Olive

Reviewed by: Transboundary Environmental Governance across the World's Largest Border ed. by Stephen Brooks and Andrea Olive Paul Todhunter Transboundary Environmental Governance across the World's Largest Border. Edited by Stephen Brooks and Andrea Olive. Winnipeg: University of Manitoba Press, 2018. vii + 248 pp. Map, tables, contributors, index. C$39.95 paper. Transboundary environmental governance concerns management of resources where "manmade boundaries . . . have been inserted against nature's will." The book provides a significant contribution to a growing literature on transboundary governance along the Canada–United States border. This international border, the world's longest border, contains 20% of the available global fresh surface water, shares numerous and diverse habitats, possesses rich and varied natural resources, and is populated by peoples with close economic ties, parallel histories, and common cultural roots. Important differences also exist, however, that lead to divergence and conflict in transboundary governance. The aim of the editors is "to help us better understand the issues, processes, and challenges that characterize transboundary environmental governance between Canada and the United States." They asked volume contributors to describe the state of existing relationships, governance structures, and processes of transboundary governance, to assess the adequacy of these structures with respect to environmental impacts, and to evaluate opportunities for reform, improved outcomes, and successful accommodation of emerging environmental concerns. The editors have splendidly met these aims. I was most impressed by the coherence of the entire volume, and how each individual chapter made a significant contribution to the whole. Each contributor focused on the editors' aims, provided an entry of similar length and depth, presented interesting case histories, and addressed common themes. Contributors had access to drafts of other chapters, and often referenced points made in other parts of the book. The volume has none of the disjointedness that can characterize edited multi-author volumes. Most chapters share a common structure, with a summary introduction, a historical perspective on the development of environmental governance, a development of those initial structures to accommodate the increasing complexity of environmental and human affairs, and selected case histories. The volume is organized along a geographical gradient cross-cut by major resource types. The editors first provide a lengthy preface that summarizes each contribution. The first chapter reviews the International Joint Commission that grew out of the Boundary Waters Treaty of 1909 and formed the basis of early Canada–United States transboundary governance, but is now overshadowed by multilayered regional agreements of varied types. The next three chapters examine the Great Lakes Basin, each focusing on a different environmental issue: water quantity, water storage, and river navigation; fisheries management; and water quality and pollution. The fifth chapter, on the Prairie Region, will be of greatest interest to this journal's readers. A historical prioritization of economic development led to full allocation of water rights in a region of scarce and unreliable water resources, but now faces challenges from new voices advocating for environmental conservation and sustainability. The St. Mary, Milk, and Souris river basins are the focus of the chapter, a decision for which rational support is given. The omission of the Red River of the North Basin is disappointing, however, given its unique properties and regional importance. A chapter on the Pacific West and two chapters on energy governance follow that are also highly relevant to the Great Plains. Here, in a unique twist, Canada has been the driver for resource development, and the US has been more resistant in its approach to resource development. The final chapter summarizes lessons learned, and looks forward to new challenges posed by invasive species, climate change, and development of the Arctic. Numerous themes emerge from the individual chapters. Multilayered governance has developed with a sharing of power between national, subnational, regional, and local levels of administration. New actors now bring their voices to the governance table, including environmentalists, nongovernmental organizations, and Indigenous, First Nation, and tribal peoples. The early dominance of economic development interests has broadened to consider environmental quality, habitat conservation, and sustainability perspectives. Common-pool resources require different governance structures and approaches depending upon the symmetry or asymmetry of regional benefits and costs of resource development. Transboundary governance has grown in complexity, often leading to institutional...

Salt dissolution and permeability in the Western Canada Sedimentary Basin

Extensive dissolution of evaporites has occurred in the Williston Basin, Canada, but it is unclear what effect this has had on bulk permeability. The bulk of this dissolution has occurred from the Prairie Evaporite Formation, which is predominantly halite and potash. However, minor evaporite beds and porosity infilling have also been removed from the overlying Dawson Bay and Souris River formations, which are predominantly carbonates. This study examines whether permeability values in the Dawson Bay and Souris River formations have been affected by dissolution, by analyzing 142 drillstem tests from those formations. For both the Dawson Bay and Souris River formations, the highest permeabilities were found in areas where halite dissolution had occurred. However, the mean permeabilities were not statistically different in areas of halite dissolution compared to those containing connate water. Subsequent precipitation of anhydrite is known to have clogged pore spaces and fractures in some instances. Geochemical relationships found here support this idea but there is no statistically significant relationship between anhydrite saturation and permeability. Geomechanical effects, notably closure of fractures due to collapse, could be a mitigating factor. The results indicate that coupling dissolution and precipitation to changes in permeability in regional flow models remains a significant challenge.

Range Extension of the Giant Water BugBelostoma flumineumSay 1832 (Hemiptera: Belostomatidae) to Saskatchewan, Canada

Abstract. We collected a single specimen of the giant water bug Belostoma flumineum Say 1832 (Hemiptera: Belostomatidae) during routine macroinvertebrate biomonitoring in the Souris River, Saskatchewan. This is the first record of B. flumineum in the province of Saskatchewan and represents a more northern record than the previously documented locations in Montana, North Dakota, and southeastern Manitoba.

Fail Not The River: Flood and Aftermath in Minot, North Dakota

This article chronicles the 2011 Souris River flood in Minot, North Dakota, and the flood protection planning that has arisen in response to that flood. The essay argues that the current plans for flood protection in Minot threaten to denude the river and to cut people off from what they have identified as sacred spaces. Flood protection should take into consideration Carolyn Merchant’s ideas about partnership ethics and David Seamon’s notion of at-homeness. This essay might not influence flood protection planning in Minot (it is too late for that), but it hopes to offer a strong argument for place studies, place meanings, and place attachment.

Nutrient delivery to Lake Winnipeg from the Red—Assiniboine River Basin – A binational application of the SPARROW model

Excessive phosphorus (TP) and nitrogen (TN) inputs from the Red–Assiniboine River Basin (RARB) have been linked to eutrophication of Lake Winnipeg; therefore, it is important for the management of water resources to understand where and from what sources these nutrients originate. The RARB straddles the Canada–United States border and includes portions of two provinces and three states. This study represents the first binationally focused application of SPAtially Referenced Regressions on Watershed attributes (SPARROW) models to estimate loads and sources of TP and TN by jurisdiction and basin at multiple spatial scales. Major hurdles overcome to develop these models included: (1) harmonization of geospatial data sets, particularly construction of a contiguous stream network; and (2) use of novel calibration steps to accommodate limitations in spatial variability across the model extent and in the number of calibration sites. Using nutrient inputs for a 2002 base year, a RARB TP SPARROW model was calibrated that included inputs from agriculture, forests and wetlands, wastewater treatment plants (WWTPs) and stream channels, and a TN model was calibrated that included inputs from agriculture, WWTPs and atmospheric deposition. At the RARB outlet, downstream from Winnipeg, Manitoba, the majority of the delivered TP and TN came from the Red River Basin (90%), followed by the Upper Assiniboine River and Souris River basins. Agriculture was the single most important TP and TN source for each major basin, province and state. In general, stream channels (historically deposited nutrients and from bank erosion) were the second most important source of TP. Performance metrics for the RARB SPARROW model are similarly robust compared to other, larger US SPARROW models making it a potentially useful tool to address questions of where nutrients originate and their relative contributions to loads delivered to Lake Winnipeg.

Tree-ring-based estimates of long-term seasonal precipitation in the Souris River Region of Saskatchewan, North Dakota and Manitoba

Historically unprecedented flooding occurred in the Souris River Basin of Saskatchewan, North Dakota and Manitoba in 2011, during a longer term period of wet conditions in the basin. In order to develop a model of future flows, there is a need to evaluate effects of past multidecadal climate variability and/or possible climate change on precipitation. In this study, tree-ring chronologies and historical precipitation data in a four-degree buffer around the Souris River Basin were analyzed to develop regression models that can be used for predicting long-term variations of precipitation. To focus on longer term variability, 12-year moving average precipitation was modeled in five subregions (determined through cluster analysis of measures of precipitation) of the study area over three seasons (November–February, March–June and July–October). The models used multiresolution decomposition (an additive decomposition based on powers of two using a discrete wavelet transform) of tree-ring chronologies from Canada and the US and seasonal 12-year moving average precipitation based on Adjusted and Homogenized Canadian Climate Data and US Historical Climatology Network data. Results show that precipitation varies on long-term (multidecadal) time scales of 16, 32 and 64 years. Past extended pluvial and drought events, which can vary greatly with season and subregion, were highlighted by the models. Results suggest that the recent wet period may be a part of natural variability on a very long time scale.

Ground deformation monitoring using RADARSAT-2 DInSAR-MSBAS at the Aquistore CO2 storage site in Saskatchewan (Canada)

Abstract. The research objectives of the Aquistore CO2 storage project are to design, adapt, and test non-seismic monitoring methods for measurement, and verification of CO2 storage, and to integrate data to determine subsurface fluid distributions, pressure changes and associated surface deformation. Aquistore site is located near Estevan in Southern Saskatchewan on the South flank of the Souris River and west of the Boundary Dam Power Station and the historical part of Estevan coal mine in southeastern Saskatchewan, Canada. Several monitoring techniques were employed in the study area including advanced satellite Differential Interferometric Synthetic Aperture Radar (DInSAR) technique, GPS, tiltmeters and piezometers. The targeted CO2 injection zones are within the Winnipeg and Deadwood formations located at > 3000 m depth. An array of monitoring techniques was employed in the study area including advanced satellite Differential Interferometric Synthetic Aperture Radar (DInSAR) with established corner reflectors, GPS, tiltmeters and piezometers stations. We used airborne LIDAR data for topographic phase estimation, and DInSAR product geocoding. Ground deformation maps have been calculated using Multidimensional Small Baseline Subset (MSBAS) methodology from 134 RADARSAT-2 images, from five different beams, acquired during 20120612–20140706. We computed and interpreted nine time series for selected places. MSBAS results indicate slow ground deformation up to 1 cm/year not related to CO2 injection but caused by various natural and anthropogenic causes.

In the Great Bend of the Souris River

My father, David Whippet, moved a family of eight from Lancaster, in the western Mojave, up onto the high plains of central North Dakota in the summer of I952. He rented a two-story, six-bedroom house near Westhope. It was shaded by cottonwoods and weeping willows and I lived in it for eleven years before he moved us again, to Sedalia in central Missouri, where he retired in 1975. I never felt the country around Sedalia. I carried the treeless northern prairie close in my mind, the spine-shattering crack of June thunder-tin drums falling from heaven, Mother called it-an image of coyotes evaporating in a draw. I went east to North Carolina to college the year Father moved us to Missouri. When my parents died, within a year of each other, my brothers and sisters sold the Sedalia house. I took no part of the proceeds. I looked back always to the broad crown of land in Bottineau county that drained away into the Mouse River, a shortgrass plain of wheat, oats, and barley, where pasqueflower and blazing star and long-headed coneflower quivered in the summer wind. I came to see it in later years as the impetus behind a life I hadn't managed well. That first summer in North Dakota, 1952, the air heated up like it did in the desert around Lancaster, but the California heat was dry. This humid Dakota weather staggered us all. I got used to the heat, though the hardest work I ever did was summer haying on those plains. I'd fall asleep at the supper table still itching with chaff. I grew to crave the dark cold of winter, the January weeks at thirty below, the table of bare land still as a sheet of iron. Against that soaking heat and bone-deep cold the other two seasons were slim, as subtle and erotic as sex. Considering my aspirations at the university in Chapel Hill-I majored in history, then did graduate work in physics-the way my life took shape seemed not to follow. The summary way to state it is that I became an itinerant, a wanderer with an affinity for any kind of work to be done with wood. I moved a lot-back to California from North Carolina, then to Tucson for a while before going to the Gulf Coast, Louisiana-always renting. After that, I worked in Utah for six years, then moved to eastern Nebraska. I considered moving to North Dakota, but that country seemed better as a distant memory. I felt estranged from it. Over those twenty years of moving around I installed cabinets and counters in people's homes, made fine furniture, and built a few houses. In my notebooks, dozens of them, I wrote meticulous descriptions of more than a hundred kinds of

Modelling ice cover formation of a lake–river system with exceptionally high flows (Lake St. Martin and Dauphin River, Manitoba)

Abstract In 2011, Manitoba experienced extreme flooding on a wide extended scale that affected many large watersheds, in particular the Upper Assiniboine, Qu'Appelle and Souris River watersheds. In order to protect Winnipeg from excessive flooding, some of the flood waters were diverted via the Portage Diversion into Lake Manitoba and Lake St. Martin, causing extreme high water levels and flooding of these lakes. The outlet of this entire drainage basin is the Dauphin River flowing from Lake St. Martin to Lake Winnipeg. The river's conveyance capacity was exceeded by the flood and the lakes could not be drained fast enough to avoid damage from high flood levels and shore line erosion and property damage from accentuated wind setup (seiche) and wave uprush (runup) of the lake water. An Emergency Channel was constructed to compensate for this constriction, which now conveys additional water from Lake St. Martin towards Lake Winnipeg. Due to the extreme flooding, the Dauphin River had unprecedented record flows in the autumn of 2011. Ice cover formation during winter freeze-up of these waters could potentially exacerbate the flooding situation for communities alongside Lake St. Martin and the Dauphin River. Hence, the river ice model RIVICE was implemented to determine flood protection elevations to which existing dikes needed to be raised and extended. The modelling takes into consideration the potential frazil ice generation that can raise water levels by up to 3 m from open water levels. High discharge and water level data was available to calibrate the model both for an open-water and an ice-covered case. Three scenarios were then simulated to determine ice-covered water levels of the river for early, best-estimate and late freeze-up events to determine flood protection levels along the Dauphin River and Lake St. Martin. The model was successfully validated using data collected during a freeze-up event in December 2011.

Haemocytic leukemia in Prince Edward Island (PEI) soft shell clam (Mya arenaria): Spatial distribution in agriculturally impacted estuaries

Intensive farming of potatoes in Prince Edward Island (PEI) relies on the repeated and widespread application of fertilizers and pesticides. In PEI the main potato farming areas are in close proximity and drain directly to estuaries. Runoff from high agricultural activity watersheds could impact benthic organism health in the depositional zone of downstream estuaries. The estuarine filter feeder Mya arenaria (soft-shell clam) could be particularly vulnerable to both particle-adsorbed and water soluble contaminants. M. arenaria is susceptible to haemocytic leukemia. In May 2009, we established that heavily proliferated leukemia (HPL) prevalence was generally higher in PEI estuaries located downstream of high intensity potato farming (Dunk and Wilmot estuaries) watersheds than in estuaries downstream of lower intensity areas. Using Mab-1E10 based immunocytochemistry we observed that leukemic haemocytes from the Dunk and Wilmot estuaries were 1E10 negative whereas those from the Ox/Sheep estuary (low potato farming intensity) were 1E10 positive. The expression of genes in the p53 tumour suppressor pathway enabled us to differentiate groups of leukemic and normal M. arenaria, validating our diagnoses. In October 2009, we confirmed that HPL prevalence was elevated in the Dunk and Wilmot estuaries compared to reference (Souris River). Moreover, leukemia prevalence declined with distance from the river mouths along transects through the Dunk and Wilmot estuaries. The pesticides ß-endosulfan and α-endosulfan were detected in surface sediments from the Dunk and Wilmot estuaries, but not in sediments from either the Souris River or several other lower intensity potato farming watersheds. Our study provides evidence of an association between intensity of potato farming and prevalence of clam leukemia at downstream estuaries in PEI.

Multiple magnetizations in Ordovician–Devonian carbonates in the Williston Basin (Manitoba, Canada)

Abstract Palaeomagnetic and rock magnetic data collected from the Upper Ordovician Red River, Silurian Interlake and Devonian Winnipegosis, Souris River and Birdbear carbonates in one well from southwestern Manitoba (Canada) reveal a complex magnetization history for the north-eastern Williston Basin. Rock magnetic analysis (thermal demagnetization, anhysteretic remanent magnetization (ARM)/saturation isothermal remanent magnetization (SIRM), S-ratios, partial ARM (pARM), SIRM crossover curves and points and coercivity) show three magnetic carriers for different magnetizations seen in this well. An Early–Mid-Jurassic remagnetization observed in the lower Red River and Souris River formations is carried by single-domain to pseudo-single-domain (SD–PSD) magnetite and was probably produced by basement fluids circulating along fractures and faults created by the Hartney impact/volcanic structure and/or tectonic movements along the Superior Boundary Zone. In the Winnipegosis Formation a possible primary depositional or early depositional magnetization (Devonian age) is carried by PSD pyrrhotite. In the Birdbear Formation two different magnetizations of uncertain age are present: one carried in hematite in the upper strata, possibly originating from the younger Amaranth Formation, and magnetite dominates in the lower strata. The upper Red River and Interlake formations contain both magnetite and pyrrhotite; however, the weaker palaeomagnetic data reveal little in terms of a magnetization age.

Determination of Impact of Sediment Oxygen Demand on the Souris River Dissolved Oxygen

Determination of Impact of Sediment Oxygen Demand on the Souris River Dissolved Oxygen