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Athabasca oil sands in Alberta, Canada, are large bitumen deposits and are one of the world's largest petroleum reserves. This research contributes to the growing body of knowledge on the influence of this naturally occurring bitumen on freshwaters. Using laboratory-based exposure studies, we examined the life cycle responses of the aquatic midge Chironomus riparius to both naturally formed solid bitumen incorporated in the sediment and its corresponding aqueous extracts, denominated as elutriates. The 28-day partial life cycle assay involved bitumen samples from two distinct geological origins in the Athabasca River Basin (Clearwater and McMurray formations), comprising both weathered and freshly collected bitumen from a total of 4 different rivers. Our results demonstrate a measurable impact of sediment-embedded bitumen on C. riparius life history traits, namely on their growth and emergence patterns. Furthermore, we observed that bitumen samples from the Ells River (McMurray formation), which were freshly collected from exposed river bank soil deposits, exerted the strongest effects on most studied eco-physiological endpoints. Bitumen extracts from the Steepbank River and Athabasca River in the McMurray Formation and Steepbank River in the Clearwater Formation followed, underscoring the geographical variance in bitumen-induced toxicity. Exposure to elutriates, simulating "weathered" bitumen generally did not induce adverse effects in C. riparius life-cycle endpoints compared to elutriates prepared from freshly eroded bank soils. This emphasizes the importance of considering bitumen sources, their age, and the aquatic receiving environment when assessing potential adverse exposure effects. Our study shows that exposure to freshly eroded soils/sediments can potentially affect benthic invertebrates. More research is needed to understand how hydrological changes affect bitumen sediment exposure and the associated risks to aquatic biota., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

To fully understand the ecological and cumulative effects of mining activities on the surrounding aquatic systems of the Canadian oil sands region, it is essential to understand the consequences of exposure to bitumen-containing soils/sediment from natural geomorphological processes. Both physical and chemical stress on aquatic biota can potentially result from exposure to natural bitumen, resulting from hillslope erosional processes and slumping of bankside soils into the rivers, affecting both riverbed habitat and water quality. The magnitude and duration of bitumen-containing soil's fluvial soils/erosional input into receiving watersheds depends on the interannual variability in the regional hydroclimatology and related seasonal and extreme flow events. The primary objective of this study was to evaluate the potential ecotoxicological effects associated with erosional input of riverbank bitumen soils using controlled exposures. A series of integrated, laboratory-based ecotoxicological bioassays were conducted using organisms with different ecological and functional traits (Daphnia magna (Cladocera), Physa acuta (Gastropoda), and Aliivibrio fischeri (Bacteria)). All model organisms were exposed to elutriates produced from natural bitumen from four different regional rivers: fresh bitumen from shoreline outcrops at the Steepbank River upper and lower reaches (STB-CF and STB-MF, respectively) and the lower-Ells River (EL-MF) and aged, fluvially processed/weathered bitumen from the shoreline of the Athabasca River (ATB-MF). All tested organisms responded negatively to STB-MF and EL-MF elutriates. Low toxicity was also observed in the STB-CF and ATB-MF samples. These results follow the chemical analysis of the parental material and elutriates, where higher levels of metals, polycyclic aromatic compounds and naphthenic acids were detected in the EL-MF sample. In summary, this study shows that eroded and transported bitumen-containing soils and sediments could be a natural source of contaminant exposure to aquatic biota. This fluvial pathway should be considered when assessing background toxicity and the toxicological and ecological effects of oil sands mining activities., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

In the Athabasca region, the oil sands are located at or near the surface making open-pit mining viable. In addition, the Athabasca River and its tributaries flow through these oil sands deposits, thereby receiving bitumen-associated contaminants through natural fluvial erosional and weathering processes. A key knowledge gap has been related to understanding both the magnitude and significance of the toxicological and ecological effects on aquatic organisms exposed to naturally occurring bitumen entering fluvial systems. Using the Daphnia magna model system, this study assessed the ecotoxicological effects of exposure to bitumen-elutriate treatments that simulated the early stages of fluvial/erosional exposure conditions. No significant among-site differences were observed in the survival of D. magna after 48 h exposure to elutriates produced from a 24 h extraction cycle, and chemical analysis indicated low concentration of a complex mixture of hydrocarbon and metal contaminants. In contrast, the same elutriates impaired reproduction and growth after a 21-day chronic exposure. F1 neonates from the chronic tests were tested for sensitivity to the reference substance potassium dichromate, revealing a decrease in their sensitivity. Inter-generational effects were also observed, with a significant decrease in subsequent neonate production, when daphnids were moved to a clean medium. Supplemental acute toxicity assays using 48 and 72 h bitumen extraction cycles progressively increased daphnid mortality after a 48-h exposure to the respective elutriates. This indicates that bitumen-associated contaminants are being liberated after initial input and fluvial washing (24 h), highlighting the need for future work to assess toxicity responses and associated elutriate water chemistry of a longer fluvial exposure time-series. This work contributes to our understanding of the possible effects of natural bitumen exposure on riverine aquatic ecosystems, providing new information to inform the delineation of baseline conditions to assess environmental change and the design of future regional effects-based monitoring programs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The extraction of oil sands from mining operations in the Athabasca Oil Sands Region uses an alkaline hot water extraction process. The oil sands process water (OSPW) is recycled to facilitate material transport (e.g., ore and tailings), process cooling, and is also reused in the extraction process. The industry has expanded since commercial mining began in 1967 and companies have been accumulating increasing inventories of OSPW. Short- and long-term sustainable water management practices require the ability to return treated water to the environment. The safe release of OSPW needs to be based on sound science and engineering practices to ensure downstream protection of ecological and human health. A significant body of research has contributed to the understanding of the chemistry and toxicity of OSPW. A multistakeholder science workshop was held in September 2017 to summarize the state of science on the toxicity and chemistry of OSPW. The goal of the workshop was to review completed research in the areas of toxicology, chemical analysis, and monitoring to support the release of treated oil sands water. A key outcome from the workshop was identifying research needs to inform future water management practices required to support OSPW return. Another key outcome of the workshop was the recognition that methods are sufficiently developed to characterize chemical and toxicological characteristics of OSPW to address and close knowledge gaps. Industry, government, and local indigenous stakeholders have proceeded to utilize these insights in reviewing policy and regulations. Integr Environ Assess Manag 2019;15:519-527. © 2019 SETAC., (© 2019 SETAC.)

Catchment wildfire can decimate freshwater benthos when burnt material washes through river channels. We conducted detailed seasonal surveys over the course of one-year at N = 9 sites following summer-time wildfire in 2009 and N = 3 sites following summer-time wildfire in 2010 (constituting one-year time-series of 9 ∗ 5 and 3 ∗ 5 samples, respectively). Basic one-year-on surveys were conducted at an additional 12 sites following 2009 wildfires (Sum postfire :Sum +one.yr ; N = 12 ∗ 2). Burnt sites were compared with 6 reference sites surveyed seasonally between autumn and summer, 2009-2010 (N = 6 ∗ 4), supplemented by 6 additional sites surveyed in summer 2004 (total reference samples: N = 6 ∗ 5). While benthic macroinvertebrates were largely unaffected by the fire event, richness and abundance were decimated during the winter, yet recovered to initial survey levels by the following summer. The differential response of assemblages in the exceptionally wet winter of 2009-10 versus 2010-11 highlighted the catalytic role of rainfall as a driver of benthic disturbance. Ecological disturbance was proportionally greater for less abundant taxa with community evenness peaking at the time of maximum disturbance. Seasonal dynamics in fire-impacted and reference sites followed a similar pattern, implying that despite the major reduction in macroinvertebrate standing crop the general character of benthic processes was sustained. One year after the wildfire event community structure was similar to the immediate post-fire assemblages and generally indistinguishable from reference samples. The statistical importance of habitat parameters at the landscape and local scale (catchment size, landuse, slope, bank management and benthic substrate) were indicative of mechanistic processes underlying wildfire disturbance-recovery and define the scope for mitigation management. The remarkable resilience of community structure in these Mediterranean streams marks an emphatic contrast to the response of benthic macroinvertebrates to comparable disturbance processes in temperate regions. Given the increasing geographic scale and frequency of fires accompanying global warming wildfire-risk may become a leading issue for river management., (Copyright © 2018. Published by Elsevier B.V.)

Over the last five decades, the Athabasca River Basin in Alberta, Canada, has been subjected to a wide range of environmental stressors from diverse human developments. This has resulted in an escalation of government, academic, industry and community-based monitoring and research efforts. However, despite all the attention received, a comprehensive synthesis of what has been studied is lacking, in particular, in relation to the efforts examining single versus multiple stressors. Based on a systematic literature review, we found 386 publications from 1969 to 2018 on the Athabasca River focusing on single stressors (68.4%) compared to multiple stressors (31.6%). There was a significant shift in the focus of studies between the 1990s and present from assessing threats of pulp and paper developments to those related to oil sands activities, with studies most predominantly addressing chemical stressors. Despite these efforts, there remain significant knowledge gaps regarding the cumulative effects of multiple stressors, particularly on biological and ecological endpoints. Correspondingly, a wide range of contradictory conclusions were reported regarding the ecological, regulatory and societal significance of the reported environmental impacts, highlighting both the complexity and often lack of standardization of approaches used. This emphasizes the need for improved integration of monitoring and research activities that are hypothesis driven, have clear objectives, and are better aligned with environmental management processes and decisions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The present study evaluated the impacts of predicted seawater acidification and Hg pollution, when stressors were acting alone and in combination, on the polychaete Hediste diversicolor. Polychaetes were exposed during 28days to low pH (7.5), Hg (5μg/L) and pH7.5+Hg, and physiological alterations (respiration rate), biochemical markers related to metabolic potential (glycogen and protein content, electron transport system activity) and oxidative status (activity of antioxidant and biotransformation enzymes, lipid peroxidation) were evaluated. The results obtained clearly showed that polychaetes were sensitive to low pH and Hg contamination, both acting alone or in combination. Organisms used their energy reserves under stressful conditions, which decreased by up to half of the control content, probably to fuel defence mechanisms. Our findings further demonstrated that polychaetes exposed to these stressors presented increased antioxidant defence mechanisms (3 fold compared to control). However, organisms were not able to prevent cellular damage, especially noticed at Hg exposure and pH7.5. Overall, although all the tested conditions induced oxidative stress in Hediste diversicolor, the combined effect of seawater acidification and Hg contamination did not induce higher impacts in polychaetes than single stressor exposures. These findings may indicate that predicted climate change scenarios may not increase Hediste diversicolor sensitivity towards Hg and may not significantly change the toxicity of this contaminant to this polychaete species., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The primary goals of environmental monitoring are to indicate whether unexpected changes related to development are occurring in the physical, chemical, and biological attributes of ecosystems and to inform meaningful management intervention. Although achieving these objectives is conceptually simple, varying scientific and social challenges often result in their breakdown. Conceptualizing, designing, and operating programs that better delineate monitoring, management, and risk assessment processes supported by hypothesis-driven approaches, strong inference, and adverse outcome pathways can overcome many of the challenges. Generally, a robust monitoring program is characterized by hypothesis-driven questions associated with potential adverse outcomes and feedback loops informed by data. Specifically, key and basic features are predictions of future observations (triggers) and mechanisms to respond to success or failure of those predictions (tiers). The adaptive processes accelerate or decelerate the effort to highlight and overcome ignorance while preventing the potentially unnecessary escalation of unguided monitoring and management. The deployment of the mutually reinforcing components can allow for more meaningful and actionable monitoring programs that better associate activities with consequences. Integr Environ Assess Manag 2017;13:877-891. © 2017 The Authors. Integrated Environmental Assessment and Management Published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC)., (© 2017 The Authors. Integrated Environmental Assessment and Management Published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).)

The bivalve Mytilus galloprovincialis collected in the Ria de Aveiro, was selected to evaluate the acute and chronic effects of carbamazepine (CBZ) at environmentally relevant concentrations. CBZ is an antiepileptic drug widely found in the aquatic environment with toxic effects to inhabiting organisms. However, few studies evaluated the acute and chronic toxicity of this drug. The experiment was performed by exposing mussels to 0.0, 0.3, 3.0, 6.0 and 9.0 CBZ μg/L, for 96 h and 28 days. To assess the toxicity of the drug, a battery of biomarkers related to mussels general physiological health status and oxidative stress was applied. CBZ was quantified in mussel tissues by an Enzyme-Linked Immunosorbent Assay (ELISA). The results obtained show that CBZ did not induce oxidative stress. However, our findings demonstrated that the drug was taken up by mussels even though presenting low bioconcentration factor (BCF) values (up to 2.2). Furthermore, our results demonstrated that after a chronic exposure the physiological parameters, namely the condition and gonadosomatic indices, were negatively affected which may impair organisms' reproductive capacity with consequences to population sustainability., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Recent studies have become increasingly focused on the assessment of pharmaceuticals occurrence in aquatic ecosystems, however the potential toxicity to non-target organisms is still largely unknown. The antihistamine cetirizine is a commonly used pharmaceutical, already detected in surface waters of marine aquatic systems worldwide. In the present study Mytilus galloprovincialis mussels were exposed to a range of cetirizine concentrations (0.3, 3.0, 6.0 and 12.0 μg/L), resembling moderate to highly contaminated areas, over 28 days. The responses of different biochemical markers were evaluated in mussels whole soft tissue, and included energy-related parameters (glycogen content, GLY; protein content, PROT; electron transport system activity, ETS), and oxidative stress markers (superoxide dismutase activity, SOD; catalase activity, CAT; glutathione S-transferases activity, GSTs; lipid peroxidation levels, LPO; reduced (GSH) and oxidized (GSSG) glutathione content). The results obtained demonstrated that with the increase of exposure concentrations mussels tended to increase their energy reserves and maintain their metabolic potential, which was significantly higher only at the highest concentration. Our findings clearly revealed that cetirizine inhibited the activity of GSTs and although induced the activity of antioxidant enzymes (SOD and CAT) mussels were not able to prevent cellular damages observed through the increase of LPO associated to the increase of exposure concentrations. Thus, this study confirmed that cetirizine induces toxic effects in Mytilus galloprovincialis, which, considering their trophic relevance, wide use as bioindicator and wide spatial distribution of this species, can result in ecological and economic negative impacts at a large scale., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Several environmental stressors have been identified as key and/or emerging drivers of habitat change that could significantly influence marine near-shore ecosystems. These include increasing discharges of pharmaceutical contaminants into the aquatic coastal systems. Pharmaceutical drugs are often detected in aquatic environments but still information on their toxicity impacts on inhabiting species is scarce, especially when acting in combination. Furthermore, almost no information is available on the impacts of pharmaceuticals in polychaetes, often the most abundant taxon in benthic communities and commonly used as indicator species of environmental conditions. Therefore, the present study aimed to evaluate the biochemical alterations induced in the polychaete Hediste diversicolor, from a low contaminated area at the Ria de Aveiro lagoon (Portugal), by the antiepileptic drug carbamazepine (0.0 - control, 0.3, 3.0, 6.0 and 9.0μg/L) and the stimulant caffeine (0.0 - control, 0.5, 3.0, and 18.0μg/L), acting alone and in combination (0.3 CBZ+0.5 CAF and 6.0 CBZ+3.0 CAF). Glutathione S-transferases (GSTs), superoxide dismutase (SOD) and catalase (CAT) activities was determined in Hediste diversicolor from each condition. Lipid peroxidation (LPO), glutathione reduced and oxidized (GSH and GSSG), glycogen and electron transport system (ETS) were also measured. The results obtained clearly revealed that both drugs induced oxidative stress in H. diversicolor, shown by the increase on LPO levels and decrease on total glutathione and GSH/GSSG ratio with the increase of exposure concentrations. Furthermore, the present findings demonstrated that polychaetes biotransformation capacity as well as antioxidant defense mechanisms were not sufficiently efficient to fight against the excess of reactive oxygen species (ROS) leading to LPO when organisms were exposed to both drugs. Our results also demonstrated that polychaetes tended to decrease the activity of ETS when exposed to drugs, avoiding energy expenditure which may prevent them from greater damages. The present study further revealed that the impacts induced by the combination of both drugs were similar to those obtained at the highest drugs concentrations acting alone., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Caffeine is known to be one of the most consumed psychoactive drugs. For this reason, caffeine is continuously released into the environment with potential impacts on inhabiting organisms. The current study evaluated the biochemical alterations induced in the clam species Ruditapes philippinarum after exposure for 28 days to caffeine (0.5, 3.0 and 18.0 μg/L). The results obtained showed that, with the increasing caffeine concentrations, an increase in clams defense mechanisms (such as antioxidant and biotransformation enzymes activity) was induced which was accompanied by an increase in protein content. Nevertheless, although an increase on defense mechanisms was observed, clams were not able to prevent cells from lipid peroxidation that increased with the increase of caffeine concentration. Furthermore, with the increase of exposure concentrations, clams increased their metabolic activity (measured by electron transport activity), reducing their energy reserves (glycogen content), to fight against oxidative stress. Overall, the present study demonstrated that caffeine may impact bivalves, even at environmentally relevant concentrations, inducing oxidative stress in organisms. The present study is an important contribution to address knowledge gaps regarding the impacts of long-term exposures to pharmaceuticals since most of the studies assessed the effects after acute exposures, most of them up to 96 h., (Copyright © 2016. Published by Elsevier Ltd.)

In the last decade studies have reported the presence of several pharmaceutical drugs in aquatic environments worldwide and an increasing effort has been done to understand the impacts induced on wildlife. Among the most abundant drugs in the environment is caffeine, which has been reported as an effective chemical anthropogenic marker. However, as for the majority of pharmaceuticals, scarce information is available on the adverse effects of caffeine on marine benthic organisms, namely polychaetes which are the most abundant group of organisms in several aquatic ecossystems. Thus, the present study aimed to evaluate the biochemical alterations induced by environmentally relevant concentrations of caffeine on the polychaete species Diopatra neapolitana and Arenicola marina. The results obtained demonstrated that after 28 days exposure oxidative stress was induced in both species, especially noticed in A. marina, resulting from the incapacity of antioxidant and biotransformation enzymes to prevent cells from lipid peroxidation. The present study further revealed that D. neapolitana used glycogen and proteins as energy to develop defense mechanisms while in A. marina these reserves were maintained independently on the exposure concentration, reinforcing the low capacity of this species to fight against oxidative stress., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Seawater pH is among the environmental factors controlling the performance of marine organisms, especially in calcifying marine invertebrates. However, changes in non-calcifying organisms (including polychaetes) may also occur due to pH decrease. Polychaetes are often the most abundant group of organisms in estuarine systems, representing an important ecological and economic resource. Thus, the present study aimed to evaluate the impacts of seawater acidification in the polychaete Hediste diversicolor, a species commonly used as bioindicator. For this, organisms were exposed to different pH levels (7.9, 7.6 and 7.3) during 28 days and several biochemical markers were measured. The results obtained demonstrated that pH decrease negatively affected osmotic regulation and polychaetes metabolism, with individuals under low pH (7.6 and 7.3) presenting higher carbonic anhydrase activity, lower energy reserves (protein and glycogen content) and higher metabolic rate (measured as Electron transport system activity). The increase on CA activity was associated to organisms osmoregulation capacity while the increase on ETS and decrease on energy reserves was associated to the polychaetes capacity to develop defense mechanisms (e.g. antioxidant defenses). In fact, despite having observed higher lipid peroxidation at pH 7.6, in polychaetes at the lowest tested pH (7.3) LPO levels were similar to values recorded in individuals under control pH (7.9). Such findings may result from higher antioxidant enzyme activity at the lowest tested pH, which prevented organisms from higher oxidative stress levels. Overall, our study demonstrated how polychaetes may respond to near-future ocean acidification conditions, exhibiting the capacity to develop biochemical strategies which will prevent organisms from lethal injuries. Such defense strategies will contribute for polychaetes populations maintenance and survival under predicted seawater acidification scenarios., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The current study assessed the biochemical alterations induced in the clam species Ruditapes philippinarum after exposure to salinity shifts (14, 28 and 42) and arsenic (As) contamination (0 and 2mg/L). The capacity of this species to recover (96h and 28 days) after exposure (96h) to both stressors, acting alone and in combination, was also evaluated. After exposure, regardless of the salinity tested, clams contaminated with As showed higher concentrations than non-contaminated specimens. After recovery, As concentration in clams decreased, with contaminated and non-contaminated specimens presenting similar values. The results obtained further demonstrated that exposure to As (2mg/L) at different salinities (salinities 14, 28 and 42) and salinity 42 (As 0mg/L) lead to an increase of lipid peroxidation and detoxification mechanisms in clams, compared with non-contaminated clams at salinities of 14 and 28. After recovery, at salinities 14 and 28, clams previously exposed to As were capable to decrease their oxidative stress to levels found in non-contaminated clams. Nevertheless, at salinity 42 both contaminated and non-contaminated clams did not survive. Overall results of measured energy-related parameters, indicators of oxidative stress, antioxidant and biotransformation enzymes indicated that As exposure and salinity shifts caused biochemical alterations in R. philippinarum, with stronger impacts when both stressors were acting in combination., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Marine organisms are constantly exposed to multiple stressors creating a range of associated environmental and ecotoxicological risks. Several stressors have been identified as key drivers of environmental change that may significantly influence marine near-shore systems. These include increased frequency and duration of extreme rainy events and drought periods, arising from climate change, and the constant discharge of contaminants into aquatic systems. A growing body of evidence demonstrates that climate change can have direct and indirect impacts on marine organisms although the combined effects with other stressors, namely with metals and metalloids, have received very little attention to date. The present study evaluated the biochemical alterations induced in the clam Ruditapes philippinarum, also known as Manila clam, when simultaneously exposed (96 h) to different arsenic concentrations (0, 4 and 17 mg/L) and a range of salinities (14, 21, 28, 35 and 42 g/L). Results obtained revealed that, when acting alone, both stressors induced oxidative stress in clams, with higher LPO levels and lower GSTs activity induced by As contamination, and a stronger inhibition of the antioxidant defenses induced by salinity increase. Furthermore, when exposed to the combination of both stressors, clams experienced stronger biochemical alterations, presenting higher LPO increases and greater decreases of antioxidant enzymes, especially noticed at higher salinities. The present findings may indicate that climate change, including predicted drought periods that will increase salinities in aquatic systems, will seriously affect the clam R. philippinarum, especially those inhabiting contaminated ecosystems., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Ocean acidification and increasing discharges of pharmaceutical contaminants into aquatic systems are among key and/or emerging drivers of environmental change affecting marine ecosystems. A growing body of evidence demonstrates that ocean acidification can have direct and indirect impacts on marine organisms although combined effects with other stressors, namely with pharmaceuticals, have received very little attention to date. The present study aimed to evaluate the impacts of the pharmaceutical drug Carbamazepine and pH 7.1, acting alone and in combination, on the clam Scrobicularia plana. For this, a long-term exposure (28 days)was conducted and a set of oxidative stress markers was investigated. The results obtained showed that S. plana was able to develop mechanisms to prevent oxidative damage when under low pH for a long period, presenting higher survival when exposed to this stressor compared to CBZ or the combination of CBZ with pH 7.1. Furthermore, the toxicity of CBZ on S. plana was synergistically increased under ocean acidification conditions (CBZ + pH 7.1): specimens survival was reduced and oxidative stress was enhanced when compared to single exposures. These findings add to the growing body of evidence that ocean acidification will act to increase the toxicity of CBZ to marine organisms,which has clear implications for coastal benthic ecosystems suffering chronic pollution from pharmaceutical drugs.

In the present study, the bivalve Scrobicularia plana and the polychaete Diopatra neapolitana were exposed to an increasing carbamazepine (CBZ) concentration gradient. Both species are among the most widely used bioindicators, and CBZ is one of the most commonly found drugs in the aquatic environment. After a chronic exposure (28 days), the results obtained revealed that CBZ induced biochemical alterations in both species. Our findings demonstrated that S. plana and D. neapolitana reduced the CBZ accumulation rate at higher CBZ concentrations, probably due to their capacity to decrease their feeding rates at stressful conditions. Nevertheless, this defence mechanism was not enough to prevent both species from oxidative stress. In fact, S. plana and D. neapolitana were not able to efficiently activate their antioxidant defence mechanisms which resulted in the increase of lipid peroxidation, especially at the highest CBZ concentrations. Comparing both species, it seems that S. plana was the most sensitive species since stronger biochemical alterations were observed in this species., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In the present study, the bivalve Scrobicularia plana, collected from two contrasting areas (pristine location and mercury contaminated area), was selected to assess the biochemical alterations imposed by pH decrease, carbamazepine (an antiepileptic) and the combined effect of both stressors. The effects on oxidative stress related biomarkers after 96 h exposure revealed that pH decrease and carbamazepine induced alterations on clams, with greater impacts on individuals from the contaminated area which presented higher mortality, higher lipid peroxidation and higher glutathione S-transferase activity. These results emphasize the risk of extrapolating results from one area to another, since the same species inhabiting different areas may be affected differently when exposed to the same stressors. Furthermore, the results obtained showed that, when combined, the impact of pH decrease and carbamazepine was lower than each stressor acting alone, which could be related to the defence mechanism of valves closure when bivalves are under higher stressful conditions., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Polychaetes have been identified by several authors as a group of marine invertebrates that respond rapidly to anthropogenic stressors. However, studies investigating alterations in Polychaetes affected by climate changes are scarce. Thus, the present study aimed to assess the impact of salinity changes (14, 21, 28, 35, 42g/L) on the physiological and biochemical performance of the Polychaete Diopatra neapolitana, evaluating the species regenerative ability and biochemical alterations. The results obtained demonstrated that organisms exposed to extreme salinity conditions (14, 21 and 42g/L) presented higher mortality rates, needed more days to completely regenerate the missing body region and also regenerated less chaetigers, when compared to organisms exposed to salinities 28 and 35g/L. The present study further demonstrated that D. neapolitana presented significantly lower glycogen and protein content at salinities 21 and 42g/L, which can be explained by higher energy expenditure in the physiological and biochemical processes. A marked impairment of the glutathione redox status was also recorded at salinities 21 and 42g/L. Increased antioxidant enzyme activities were observed at salinity 21g/L while LPO levels were increased at salinity 42g/L. Overall the present study demonstrated that the regenerative capacity of D. neapolitana can be used as a tool to assess environmental changes, namely salinity shifts. Moreover, stress related biomarkers revealed to be useful to evaluate the alterations in Polychaetes due to salinity changes. D. neapolitana revealed to be a good bioindicator to salinity alterations., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This article provides a review of the routine methods currently utilized for total naphthenic acid analyses. There is a growing need to develop chemical methods that can selectively distinguish compounds found within industrially derived oil sands process affected waters (OSPW) from those derived from the natural weathering of oil sands deposits. Attention is thus given to the characterization of other OSPW components such as oil sands polar organic compounds, PAHs, and heavy metals along with characterization of chemical additives such as polyacrylamide polymers and trace levels of boron species. Environmental samples discussed cover the following matrices: OSPW containments, on-lease interceptor well systems, on- and off-lease groundwater, and river and lake surface waters. There are diverse ranges of methods available for analyses of total naphthenic acids. However, there is a need for inter-laboratory studies to compare their accuracy and precision for routine analyses. Recent advances in high- and medium-resolution mass spectrometry, concomitant with comprehensive mass spectrometry techniques following multi-dimensional chromatography or ion-mobility separations, have allowed for the speciation of monocarboxylic naphthenic acids along with a wide range of other species including humics. The distributions of oil sands polar organic compounds, particularly the sulphur containing species (i.e., OxS and OxS2) may allow for distinguishing sources of OSPW. The ratios of oxygen- (i.e., Ox) and nitrogen-containing species (i.e., NOx, and N2Ox) are useful for differentiating organic components derived from OSPW from natural components found within receiving waters. Synchronous fluorescence spectroscopy also provides a powerful screening technique capable of quickly detecting the presence of aromatic organic acids contained within oil sands naphthenic acid mixtures. Synchronous fluorescence spectroscopy provides diagnostic profiles for OSPW and potentially impacted groundwater that can be compared against reference groundwater and surface water samples. Novel applications of X-ray absorption near edge spectroscopy (XANES) are emerging for speciation of sulphur-containing species (both organic and inorganic components) as well as industrially derived boron-containing species. There is strong potential for an environmental forensics application of XANES for chemical fingerprinting of weathered sulphur-containing species and industrial additives in OSPW.

Climate variability and change is projected to have significant effects on the physical, chemical, and biological components of northern Canadian marine, terrestrial, and freshwater systems. As the climate continues to change, there will be consequences for biodiversity shifts and for the ranges and distribution of many species with resulting effects on availability, accessibility, and quality of resources upon which human populations rely. This will have implications for the protection and management of wildlife, fish, and fisheries resources; protected areas; and forests. The northward migration of species and the disruption and competition from invading species are already occurring and will continue to affect marine, terrestrial, and freshwater communities. Shifting environmental conditions will likely introduce new animal-transmitted diseases and redistribute some existing diseases, affecting key economic resources and some human populations. Stress on populations of iconic wildlife species, such as the polar bear, ringed seals, and whales, will continue as a result of changes in critical sea-ice habitat interactions. Where these stresses affect economically and culturally important species, they will have significant effects on people and regional economies. Further integrated, field-based monitoring and research programs, and the development of predictive models are required to allow for more detailed and comprehensive projections of change to be made, and to inform the development and implementation of appropriate adaptation, wildlife, and habitat conservation and protection strategies.

Various types of ecosystem-based climate proxies have been used to assess past arctic change. Although lotic records are relatively poor because of the constant reworking of riverine material, high-quality lentic data have been assembled back to the end of the Pleistocene and deglaciation of the circumpolar Arctic. In general, climatic variations in the Holocene, partly due to changes in the shrinking effect of glacier coverage, produced significant temporal and spatial variations in arctic hydrology and freshwater ecosystems. Of particular note were the vast expansions of northern peatlands during major protracted periods of wetting. More recent lake biota and sedimentiological data reflect the general warming trend that has occurred over the last one to two centuries and indicate major changes to freshwater characteristics such as ice-cover duration and thermal stratification. Such data provide an excellent baseline against which future effects of climate change can be both projected and measured.

Projected shifts in climate forcing variables such as temperature and precipitation are of great relevance to arctic freshwater ecosystems and biota. These will result in many direct and indirect effects upon the ecosystems and fish present therein. Shifts projected for fish populations will range from positive to negative in overall effect, differ among species and also among populations within species depending upon their biology and tolerances, and will be integrated by the fish within their local aquascapes. This results in a wide range of future possibilities for arctic freshwater and diadromous fishes. Owing to a dearth of basic knowledge regarding fish biology and habitat interactions in the north, complicated by scaling issues and uncertainty in future climate projections, only qualitative scenarios can be developed in most cases. This limits preparedness to meet challenges of climate change in the Arctic with respect to fish and fisheries.

Fisheries for arctic freshwater and diadromous fish species contribute significantly to northern economies. Climate change, and to a lesser extent increased ultraviolet radiation, effects in freshwaters will have profound effects on fisheries from three perspectives: quantity of fish available, quality of fish available, and success of the fishers. Accordingly, substantive adaptation will very likely be required to conduct fisheries sustainably in the future as these effects take hold. A shift to flexible and rapidly responsive 'adaptive management' of commercial fisheries will be necessary; local land- and resource-use patterns for subsistence fisheries will change; and, the nature, management and place for many recreational fisheries will change. Overall, given the complexity and uncertainty associated with climate change and related effects on arctic freshwaters and their biota, a much more conservative approach to all aspects of fishery management will be required to ensure ecosystems and key fished species retain sufficient resiliency and capacity to meet future changes.

Climate change is likely to act as a multiple stressor, leading to cumulative and/or synergistic impacts on aquatic systems. Projected increases in temperature and corresponding alterations in precipitation regimes will enhance contaminant influxes to aquatic systems, and independently increase the susceptibility of aquatic organisms to contaminant exposure and effects. The consequences for the biota will in most cases be additive (cumulative) and multiplicative (synergistic). The overall result will be higher contaminant loads and biomagnification in aquatic ecosystems. Changes in stratospheric ozone and corresponding ultraviolet radiation regimes are also expected to produce cumulative and/or synergistic effects on aquatic ecosystem structure and function. Reduced ice cover is likely to have a much greater effect on underwater UV radiation exposure than the projected levels of stratospheric ozone depletion. A major increase in UV radiation levels will cause enhanced damage to organisms (biomolecular, cellular, and physiological damage, and alterations in species composition). Allocations of energy and resources by aquatic biota to UV radiation protection will increase, probably decreasing trophic-level productivity. Elemental fluxes will increase via photochemical pathways.

Large variations exist in the size, abundance and biota of the two principal categories of freshwater ecosystems, lotic (flowing water; e.g., rivers, streams, deltas and estuaries) and lentic (standing water; lakes, ponds and wetlands) found across the circumpolar Arctic. Arctic climate, many components of which exhibit strong variations along latitudinal gradients, directly affects a range of physical, chemical and biological processes in these aquatic systems. Furthermore, arctic climate creates additional indirect ecological effects through the control of terrestrial hydrologic systems and processes, particularly those associated with cryospheric components such as permafrost, freshwater ice and snow accumulation/ablation. The ecological structure and function of arctic freshwater systems are also controlled by external processes and conditions, particularly those in the headwaters of the major arctic rivers and in the adjacent marine environment. The movement of physical, chemical and biotic components through the interlinked lentic and lotic freshwater systems are major determinants of arctic freshwater ecology.

In general, the arctic freshwater-terrestrial system will warm more rapidly than the global average, particularly during the autumn and winter season. The decline or loss of many cryospheric components and a shift from a nival to an increasingly pluvial system will produce numerous physical effects on freshwater ecosystems. Of particular note will be reductions in the dominance of the spring freshet and changes in the intensity of river-ice breakup. Increased evaporation/evapotranspiration due to longer ice-free seasons, higher air/water temperatures and greater transpiring vegetation along with increase infiltration because of permafrost thaw will decrease surface water levels and coverage. Loss of ice and permafrost, increased water temperatures and vegetation shifts will alter water chemistry, the general result being an increase in lotic and lentic productivity. Changes in ice and water flow/levels will lead to regime-specific increases and decreases in habitat availability/quality across the circumpolar Arctic.

Changes in climate and ultraviolet radiation levels in the Arctic will have far-reaching impacts, affecting aquatic species at various trophic levels, the physical and chemical environment that makes up their habitat, and the processes that act on and within freshwater ecosystems. Interactions of climatic variables, such as temperature and precipitation, with freshwater ecosystems are highly complex and can propagate through the ecosystem in ways that are difficult to project. This is partly due to a poor understanding of arctic freshwater systems and their basic interrelationships with climate and other environmental variables, and partly due to a paucity of long-term freshwater monitoring sites and integrated hydro-ecological research programs in the Arctic. The papers in this special issue are an abstraction of the analyses performed by 25 international experts and their associated networks on Arctic freshwater hydrology and related aquatic ecosystems that was initially published by the Arctic Climate Impact Assessment (ACIA) in 2005 as "Chapter 8--Freshwater Ecosystems and Fisheries". The papers provide a broad overview of the general hydrological and ecological features of the various freshwater ecosystems in the Arctic, including descriptions of each ACIA region, followed by a review of historical changes in freshwater systems during the Holocene. This is followed by an assessment of the effects of climate change on broad-scale hydro-ecology; aquatic biota and ecosystem structure and function; and arctic fish and fisheries. Potential synergistic and cumulative effects are also discussed, as are the roles of ultraviolet radiation and contaminants. The nature and complexity of many of the effects are illustrated using case studies from around the circumpolar north, together with a discussion of important threshold responses (i.e., those that produce stepwise and/or nonlinear effects). The issue concludes with summary the key findings, a list of gaps in scientific understanding, and policy-related recommendations.

Arctic freshwater and diadromous fish species will respond to the various effects of climate change in many ways. For wide-ranging species, many of which are key components of northern aquatic ecosystems and fisheries, there is a large range of possible responses due to inter- and intra-specific variation, differences in the effects of climate drivers within ACIA regions, and differences in drivers among regions. All this diversity, coupled with limited understanding of fish responses to climate parameters generally, permits enumeration only of a range of possible responses which are developed here for selected important fishes. Accordingly, in-depth examination is required of possible effects within species within ACIA regions, as well as comparative studies across regions. Two particularly important species (Arctic char and Atlantic salmon) are examined as case studies to provide background for such studies.

Climate change is projected to cause significant alterations to aquatic biogeochemical processes, (including carbon dynamics), aquatic food web structure, dynamics and biodiversity, primary and secondary production; and, affect the range, distribution and habitat quality/quantity of aquatic mammals and waterfowl. Projected enhanced permafrost thawing is very likely to increase nutrient, sediment, and carbon loadings to aquatic systems, resulting in both positive and negative effects on freshwater chemistry. Nutrient and carbon enrichment will enhance nutrient cycling and productivity, and alter the generation and consumption of carbon-based trace gases. Consequently, the status of aquatic ecosystems as carbon sinks or sources is very likely to change. Climate change will also very likely affect the biodiversity of freshwater ecosystems across most of the Arctic. The magnitude, extent, and duration of the impacts and responses will be system- and location-dependent. Projected effects on aquatic mammals and waterfowl include altered migration routes and timing; a possible increase in the incidence of mortality and decreased growth and productivity from disease and/or parasites; and, probable changes in habitat suitability and timing of availability.

The Northern River Ecosystem Initiative (NREI), 1997-2004, has provided new scientific knowledge in response to specific recommendations from its predecessor, the Northern River Basins Study (NRBS), 1990-1996. The two initiatives together provide a remarkable body of science which is, and will continue to be, used by resource managers responsible for economic and environmental sustainability in the northern watersheds of Alberta. The NREI focused its investigative efforts on improving our understanding related to ecological considerations of changes in river flow, effect of climate change on flow, ecological responses to pollution and cumulative effects, vulnerability of drinking water quality, and to a lesser degree, wildlife (birds) response to large scale changes within the watersheds. Key findings are briefly presented in this paper and discussed in greater detail in the other NREI papers included in this. Commensurate with the undertakings of NREI, provincial and territorial governments, First Nation and Métis communities, and other administrative organizations such as the Mackenzie River Basin Board, undertook policy, regulatory, and watershed initiatives towards achieving sustainability and providing reliable drinking water quality.

Anthropogenic inputs of nitrogen (N), phosphorus (P) and oxygen-consuming material to aquatic ecosystems can change nutrient dynamics, deplete oxygen, and change abundance and diversity of aquatic plants and animals. The Northern Rivers Ecosystem Initiative required a research and assessment program to establish the contribution of pulp mill and sewage discharges to eutrophication and depressions in dissolved oxygen (DO) in the Athabasca and Wapiti rivers of northern Alberta, Canada and examine the adequacy of existing guidelines for protecting these systems. Analysis of long-term data showed that total N (TN) and total P (TP) concentrations in exposed river reaches exceeded concentrations in reference reaches by < or = 2 times for the Athabasca River, and by 9.6 (TP) and 2.6 (TN) times for the Wapiti River. Results from nutrient limitation experiments conducted in situ and in mesocosms showed that benthic algal production was nutrient sufficient downstream of pulp mill discharges but constrained in upper river reaches by insufficient P (Athabasca River) or N + P (Wapiti River). Dissolved oxygen (DO) concentrations in both rivers declined during winter such that median concentrations in the Athabasca River 945 km downstream of the headwaters were approximately 8 mg L(-1) in mid-February. Although water column DO rarely approached the guideline of 6.5 mg L(-1), DO studies undertaken in the Wapiti River showed that pore water DO often failed to meet this guideline and could not be predicted from water column DO. Results from this integrated program of monitoring and experimentation have improved understanding of the interactions between nutrients, DO and aquatic ecosystem productivity and resulted in recommendations for revisions to nutrient and DO guidelines for these northern rivers.

Competition theory predicts that population fluctuations can promote genetic diversity when combined with density-dependent selection. However, this stabilizing mechanism has rarely been tested, and was recently rejected as an explanation for maintaining diversity in natural populations of the freshwater herbivore Daphnia pulex. The primary limitation of competition theory is its failure to account for the alternative types of population cycles that are caused by size- or stage-dependent population vital rates--even though such structure both explains the fluctuating dynamics of many species and may alter the outcome of competition. Here we provide the first experimental test of whether alternative types of cycles affect natural selection in predator-prey systems. Using competing Daphnia genotypes, we show that internally generated, stage-structured cycles substantially reduce the magnitude of selection (thereby contributing to the maintenance of genetic diversity), whereas externally forced cycles show rapid competitive exclusion. The change in selection is ecologically significant, spanning the observed range in natural populations. We argue that structured cycles reduce selection through a combination of stalled juvenile development and stage-specific mortality. This potentially general fitness-equalizing mechanism may reduce the need for strong stabilizing mechanisms to explain the maintenance of genetic diversity in natural systems.

The current study aimed to determine the potential of two important aquatic invertebrate crustacean species, Daphnia magna and Ceriodaphnia dubia, to adsorb cadmium on to their carapaces from aqueous solution. Using the Langmuir equation to model data outputs, it was shown that cadmium readily became associated with the carapace surfaces of both species, with uptake being dependent on exposure time and concentration. Maximum carapace-adsorption potential was found to be directly related to surface area, so that at predicted carapace saturation, D. magna neonates bound approximately five times more cadmium than the smaller C. dubia neonates. However, adsorption per unit surface area was found to be similar under the same exposure conditions. Results of surface metal adsorption studies in C. dubia suggested that short term exposures to high concentrations of aqueous cadmium would lead to similar levels of adsorption as obtained with long-term exposures to low concentrations. The study illustrates that contaminants adsorbed to prey surfaces may be an important mechanism of exposure to predators, and highlights some potential problems of feeding organisms during long-term toxicity tests.

Recent work with the freshwater zooplankton Daphnia has suggested that the quality of its algal prey can have a significant effect on its demographic rates and life-history patterns. Predator-prey theory linking food quantity and food quality predicts that a single system should be able to display two distinct patterns of population dynamics. One pattern is predicted to have high herbivore and low algal biomass dynamics (high HBD), whereas the other is predicted to have low herbivore and high algal biomass dynamics (low HBD). Despite these predictions and the stoichiometric evidence that many phytoplankton communities may have poor access to food of quality, there have been few tests of whether a dynamic predator-prey system can display both of these distinct patterns. Here we report, to the authors' knowledge, the first evidence for two dynamical patterns, as predicted by theory, in a single predator-prey system. We show that the high HBD is a result of food quantity effects and that the low HBD is a result of food quality effects, which are maintained by phosphorus limitation in the predator. These results provide an important link between the known effects of nutrient limitation in herbivores and the significance of prey quality in predator-prey population dynamics in natural zooplankton communities.

Laboratory experiments were performed to identify the mechanisms by which three mayfly grazers, Baetis tricaudatus, Ephemerella aurivilli and Paraleptophlebia heteronea deplete algae from substrates. Field observations indicated these mayflies foraged predominantly (>70% of all individuals) within small (1-2 cm diameter), low biomass areas where algal biomass was significantly lower than the surrounding algal mat. We postulated four models of algal patch depletion based on the combined effects of a type II functional response consumptive model and four possible forms of nonconsumptive loss. These models were tested in laboratory feeding trials by examining the relative importance of consumptive and non-consumptive removal of the diatom, Navicula sp., by the three common mayfly grazers. The trials were conducted in plexiglass streams that contained substrates with one of five biomass levels (0.11, 0.24, 0.43, 0.65, 0.92 mg/cm 2 dry weight) of the diatom food. After each 1 h feeding trial, consumption was measured, and the remaining algae scraped from the substrates so non-consumption and total patch depletion could be determined. Consumption by all three species followed a type II functional response; mayflies were capable of grazing diatom layers of extremely low biomass (0.11 mg/cm 2 ) and reached an asymptotic feeding rate when diatom biomass ranged from 0.24-0.43 mg/cm 2 . Upper asymptotic feeding rates occurred at algal biomasses that were 20 times lower than algal biomass levels within foraging areas in the field and >50 times the overall mean algal biomass on upper stone surfaces in the Bow River. When diatom biomass was low (0.11 mg/cm 2 ), the amount of algae ingested accounted for 27%-75% of total depletion of algal patches. Above this level, nonconsumptive, foraging-related losses increased. Thus, depletion of diatom patches was non-linear and positively related with diatom biomass due to the disproportionate increase in non-consumptive losses combined with the type II functional response consumptive model (Case 4). This disproportionate increase in non-consumptive loss may results from (i) a passive process attributable to mechanical limitations of the feeding apparatus, (ii) an active selection process during foraging or (iii) instability of the diatom material resulting in disproportionately high foraging related dislodgement. Regardless of the mechanism, our experiments indicate the importance of considering algal patch depletion by mayfly grazers as a dual product of consumptive and non-consumptive foraging processes. Furthermore, the non-linear increase in nonconsumptive loss with increased algal biomass suggests this process may be a major mechanism of algal patch depletion by mayflies when algal biomass is high.

The prey utilization of Glossiphonia complanata and Helobdella stagnalis from Bruce Lake, Alberta, Canada was examined quantitatively using serological techniques. While considerable prey range overlap occurred between the species, niche overlap was low during the winter, peaked in March and declined through the summer. Temporal differences in feeding and intraspecific weight class differences in prey utilization were found in both species but more distinctly in G. complanata. It is suggested that co-existance of G. complanata and H. stagnalis is based on adjustments of weight class food resource partitioning on a temporal basis.