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Satellite imagery can be analyzed to offer a preliminary regional assessment of mine tailings indicators, enabling identification before performing in-depth fieldwork. Nova Scotia, Canada, still retains mine tailings produced in the 1860s to the 1940s in 64 historic gold districts, which exceed soil guidelines for arsenic (As) and mercury (Hg) levels. Tailings data often relies on historical maps, which may not accurately depict the current extent due to wind and rain transportation. A classification model was designed to analyze multispectral Sentinel-2 images and indicate pixels potentially comprising tailings. This classifier had an overall F1-Score about 0.7 for most methods tested, but this accuracy was not consistent across all land cover types. In particular, wetland and coastal areas seemed to generate a high number of false positives. In this study, these potential false positives are investigated to better understand the model's confusion and improve future results. [ABSTRACT FROM AUTHOR]

We report first records of the cambarid crayfish Procambarus clarkii (Girard, 1852) in Nova Scotia, Canada. This species is native to northern Mexico and the southern United States and has been introduced to all continents except Australia and Antarctica. An established population of P. clarkii was found concentrated in one area of Three Mile Lake, a small freshwater lake in Halifax County, which builds upon existing evidence that this "warm-water" species can establish in cold temperate regions. We discuss possible introduction mechanisms and impacts, as well as potential measures to better prevent and detect future invasions of freshwater species in Nova Scotia. [ABSTRACT FROM AUTHOR]

We report the first records for the Eurasian zooplankton species Thermocyclops crassus (Fischer, 1853) (Copepoda, Cyclopoida) from two freshwater sites in eastern Canada collected between 2020 and 2022. Thermocyclops crassus were found at high densities (between 8 × 103 and 2 × 105 adults/m3) in Lake St. Pierre on the St. Lawrence River, Québec, but at very low densities (between 0.3 and 0.7 adults/m3) in Wentzell's Lake on the LaHave River system, Nova Scotia. We discuss possible introduction pathways for both sites as well as the need for enhanced biosurveillance and increased public education in eastern Canada. [ABSTRACT FROM AUTHOR]

Fish mercury (Hg) concentrations have been measured over the last 30-40 years in all regions of Canada as part of various monitoring and research programs. Despite this large amount of data, only regional assessments of fish Hg trends and patterns have previously been attempted. The objective of this study was to assemble available freshwater fish Hg concentration data from all provinces and territories and identify national patterns. The Canadian Fish Mercury Database includes over 330 000 records representing 104 species of freshwater fish collected from over 5000 locations across Canada between 1967 and 2010. Analysis of the 28 most frequently occurring species (>1000 records) showed that the majority of variation in Hg concentrations (when normalized to a standard size) was accounted for by geographic location. Median Hg concentrations increased with trophic level (r = 0.40, p < 0.05), with the highest Hg concentrations found in piscivorous species such as walleye (Sander vitreus), northern pike (Esox lucius), and lake trout (Salvelinus namaycush). The Canadian Fish Mercury Database provides the most comprehensive summary of fish Hg measurements in Canada, and the results indicate that several regionally observed trends in fish Hg concentrations (e.g., Hgbiomagnification and geographic variation) are observed at a national scale. Implications for the effective assessment of changes in fish Hg concentrations in relation to changes in Hg emission regulations are discussed. Les concentrations de mercure (Hg) dans le poisson sont mesurees depuis 30 ou 40 ans dans toutes les regions du Canada, dans le cadre de divers programmes de surveillance et de recherche. Malgre cette vaste quantite de donnees, seules des evaluations regionales des tendances et distributions du Hg dans le poisson ont ete effectuees par le passe. L'objectif de l'etude consistait a regrouper les donnees disponibles sur les concentrations de Hg dans les poissons dulcicoles pour toutes les provinces et tous les territoires et a cerner les motifs de distribution a l'echelle nationale. La base de donnees canadienne sur le mercure dans le poisson (' Canadian Fish Mercury Database ') comprend plus de 330 000 entrees representant 104 especes de poisons dulcicoles echantillonnes dans plus de 5000 localites a la grandeur du pays, de 1967 a 2010. L'analyse des 28 especes les plus frequentes (>1000 entrees) a demontre que la situation geographique expliquait la majeure partie de la variabilite des concentrations de Hg (normalisees en fonction d'une taille standard). Les concentrations medianes de Hg augmentaient parallelement au niveau trophique (r = 0,40, p < 0,05), les poissons piscivores comme le dore (Sander vitreus), le grand brochet (Esox lucius)etle touladi (Salvelinus namaycush) presentant les plus fortes concentrations. La base de donnees canadienne sur le mercure dans le poisson constitue la synthese la plus exhaustive des mesures de Hg dans le poisson au Canada, et les resultats indiquent que plusieurs tendances observees a l'echelle regionale des concentrations de Hg dans le poisson (p. ex. bioamplification et variations geographiques du Hg) sont egalement observees a l'echelle nationale. Les consequences de ces resultats en ce qui concerne l'evaluation efficace de l'evolution des concentrations de Hg dans le poisson par rapport aux modifications de la reglementation en matiere d'emissions de Hg sont abordees. [Traduit par la Redaction], Introduction Anthropogenic activities have contributed to the increase in the global atmospheric mercury (Hg) pool during the 20th century (Pacyna et al. 2010). In Canada, with the exception of known [...]