Chris N Glover’s research while affiliated with University of Alberta and other places

Environmental DNA (eDNA) assays represent a non-invasive approach for biomonitoring. To assess Arctic grayling (Thymallus arcticus) populations in the Little Nahanni watershed of Northwest Territories (NWT), Canada, an eDNA assay that has been previously validated for use in fish of the Beringia lineage was used in conjunction with traditional survey methods (i.e., electrofishing). Forty-six 100-metre reaches of streams were assessed in August 2015. The assay successfully detected Arctic grayling of the Nahanni lineage, with an eDNA signal recorded at each of the 17 sites in which Arctic grayling were observed by traditional fish surveys, but also at 3 of the 29 sites where Arctic grayling were not observed. The presence of eDNA was related to habitat metrics via Random Forest and correlation analyses. Riffles and water temperature were identified as being predictive of Arctic grayling eDNA abundance; however, no significant relationship between eDNA abundance and biomass proxies (fish abundance and fork length metrics) could be established. The high congruence between traditional approaches and eDNA surveys suggests adoption of the latter method will enhance the temporal and spatial acuity of biomonitoring, thereby improving field assessment of Arctic grayling populations and contributing towards more effective conservation management of this species.

An important goal of environmental and comparative physiology research is to identify species or populations that may be susceptible to environmental change such as heat wave events that are predicted to become more frequent and intense in the future. This study tested the hypothesis that fishes inhabiting alkaline lakes face significant physiological challenges, which results in reduced thermal tolerance. Brook stickleback (Culaea inconstans) were collected from an alkaline lake (pH 9.3) in Alberta, Canada and held under neutral conditions in the laboratory. Subsequently, fish were acutely exposed (4 d) to neutral (pH 7) or alkaline (pH 9.5) waters at 10 or 25°C. Exposure to alkaline water reduced critical thermal maximum (CTmax) in stickleback by approximately 1°C, but thermal acclimation capacity (“thermal plasticity”) was unaffected by alkaline exposure. Alkaline conditions resulted in physiological disturbances characteristic of exposure to high pH including elevated whole-body ammonia and lactate concentrations. Acute warming to CTmax in alkaline-exposed fish resulted in reductions in whole-body sodium and chloride concentrations. In addition, alkaline exposure compromised recovery from exercise at elevated temperatures. Overall, these results suggest that the physiological disturbances observed in response to alkaline exposure may render fish more susceptible to acute warming, reducing thermal tolerance.

Concentrations of selenium that exceed regulatory guidelines have been associated with coal mining activities and have been linked to detrimental effects on aquatic ecosystems and the organisms therein. Although the major route of selenium uptake in macroinvertebrates is via the diet, the uptake of waterborne selenite (HSeO3−), the prominent form at circumneutral pH, can be an important contributor to selenium body burden and thus selenium toxicity. In the current study, radiolabelled selenite (Se75) was used to characterize the mechanism of selenite uptake in the water flea, Daphnia magna. The concentration dependence (1–32 μM) of selenite uptake was determined in 1-hour uptake assays in artificial waters that independently varied in bicarbonate, chloride, sulphate, phosphate and selenate concentrations. At concentrations representative of those found in highly contaminated waters, selenite uptake was phosphate-dependent and inhibited by foscarnet, a phosphate transport inhibitor. At higher concentrations, selenite uptake was dependent on waterborne bicarbonate concentration and inhibited by the bicarbonate transporter inhibitor DIDS (4,4′-diisothiocyano-2,2′-stilbenedisulfonic acid). These findings suggest that concentrations of phosphate in coal mining-affected waters could alter selenite uptake in aquatic organisms and could ultimately affect the toxic impacts of selenium in such waters.

Dissolved organic matter is a ubiquitous component of freshwater and marine environments, and includes small nutrient molecules, such as amino acids, which may be available for uptake by aquatic biota. Epithelial transporters, including cotransporters, uniporters and antiporters, facilitate the absorption of dissolved amino acids (often against concentration gradients). Although there is a lack of mechanistic and molecular characterization of such transporters, pathways for the direct uptake of amino acids from the water appear to exist in a wide range of marine phyla, including Porifera, Cnidaria, Platyhelminthes, Brachiopoda, Mollusca, Nemertea, Annelida, Echinodermata, Arthropoda and Chordata. In these animals, absorbed amino acids have several putative roles, including osmoregulation, hypoxia tolerance, shell formation and metabolism. Therefore, amino acids dissolved in the water may play an important, but overlooked, role in aquatic animal nutrition.

The mechanisms of acute (96 h) and sub‐chronic (28‐d) toxicity of the waterborne trace metal thallium (Tl) to rainbow trout ( Oncorhynchus mykiss ) were investigated. Specifically, effects on branchial and renal ionoregulatory enzymes (sodium/potassium ATPase and proton ATPase) and hepatic oxidative stress endpoints (protein carbonylation, glutathione content and activities of catalase and glutathione peroxidase) were examined. Fish (19‐55 g) were acutely exposed to 0 (control), 0.9 (regulatory limit), 2004 (half the acute median lethal concentration) or 4200 (acute median lethal concentration) µg Tl L ‐1 or sub‐chronically exposed to 0, 0.9 or 141 (an elevated environmental concentration) µg Tl L ‐1 . The only effect following acute exposure was a stimulation of renal H ⁺ ‐ATPase activity at the highest Tl exposure concentration. Similarly, the only significant effect of sub‐chronic Tl exposure was an inhibition of branchial NKA activity at 141 µg Tl L ‐1 , an effect that may reflect the interaction of Tl with potassium ion handling. Despite significant literature evidence for effects of Tl on oxidative stress, there were no effects of Tl on any such endpoint in rainbow trout, regardless of exposure duration or exposure concentration. Elevated basal levels of antioxidant defences may explain this finding. These data suggest that ionoregulatory perturbance is a more likely mechanism of Tl toxicity than oxidative stress in rainbow trout, but is an endpoint of relevance only at elevated environmental Tl concentrations.

Arctic grayling ( Thymallus arcticus ) is a salmonid fish of significant conservation value. However, conservation efforts are hindered by a lack of fundamental information regarding details such as current population distribution, migratory patterns, and natal habitats. In the current study, we designed, optimized, and field‐ and laboratory‐validated an environmental DNA (eDNA) and environmental RNA (eRNA) assay for Arctic grayling biomonitoring. Using an in silico approach, a robust species‐specific eDNA assay was generated, and filtering and extraction protocols were optimized for maximal eDNA yield. A Preserve, Precipitate, Lyse, Precipitate, and Purify (PPLPP) extraction method generated 70‐fold higher eDNA yields than a column‐based approach. Species‐specificity relative to co‐occurring salmonid fish was validated, and no significant amplification was noted for rainbow trout, brook trout, or mountain whitefish. Shedding rates of eDNA were around eight to nine times higher than those of eRNA, although the two types of nucleic acids decayed at similar rates. Shedding and decay rates were subsequently used to build detection probability models that account for pool size and water exchange rates. These data indicate that eDNA and eRNA are detectable in pools up to 32,500 m ³ in volume and with water flow of less than 0.5 m ³ s ⁻¹ when an Arctic grayling is present. This knowledge can be implemented when designing field sampling strategies. Finally, the assay successfully amplified Arctic grayling eDNA from field‐collected samples, with signal strength indicating preferred Arctic grayling habitat or conditions that favored the concentration and retention of eDNA.

The trace element thallium (Tl) exerts its toxic effects, at least in part, through its mimicry of potassium (K+) and subsequent impairment of K+ homeostasis. However, the specific nature of this effect remains poorly understood, especially in aquatic biota that are threatened by elevated concentrations of Tl associated with mining and refining effluents. In this study experiments were conducted to mechanistically examine the relationship between Tl and K+ in terms of uptake and toxicity in the regulatory model species Daphnia magna. In one set of experiments the effects of K+, the K+ analog rubidium (Rb+), and generalized K+ channel blocker cesium (Cs+) on Tl-induced acute toxicity were examined. The presence of increasing concentrations of K+ and Rb+ in exposure water reduced waterborne Tl toxicity, indicating that the actions of Tl were mediated at least in part through interactions with K+. However, in the presence of elevated water Cs+, the toxicity of Tl paradoxically increased. Pharmaceuticals with putative blocking actions on K+ channels failed to alter whole-body K+ of control organisms, but in the case of clozapine and chlorpropamide, whole-body K+ status was significantly elevated relative to exposures with Tl alone, which tended to reduce this metric. These data identify inwardly rectifying and voltage gated K+ channels as potential loci of Tl toxicity. Experiments using rubidium (Rb+) as a tracer of K+, showed that waterborne Tl affects the uptake of K+, but the magnitude of inhibition by Tl was not sufficient to explain the effect on whole-body K+. While these data indicate interactions between Tl and K occur at K+ transporters in D magna, they also indicate that environmental levels of K+ are likely to ameliorate toxicity in most natural waters.