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No description available.

Long-term insect abundances have been studied to investigate factors structuring the insect communities of the temporary wetlands around the River Dalälven floodplain. In the wet meadows and swamps in the River Dalälven floodplains recurrent floods are the ultimate prerequisite for high production of floodwater mosquitoes. In the larval stages these make up a superabundant potential prey for aquatic predatory insects while as adults they become nuisance for people and animals. Mosquito control with Bacillus thuringiensis israelensis (Bti) has been carried out in parts of the floodplain wetlands since 2002. This study investigate potential long-term effects of Bti on non-target insects in general, and non-biting midges (Diptera: Chironomidae) and aquatic predator insects in special in 10 temporary wetlands. Diving-beetles (Coleoptera: Dytiscidae) were the most common aquatic predatory insects in temporary flooded wetlands, and we found no indications that diving-beetles were negatively affected by mosquito larvae reduction with Bti-treatments. Non-target Bti-effects on the insect community in general, measured as increase or decrease of insect abundances, in general showed no effects of Bti except for Coleoptera. The non-biting midges were studied on species level, since this taxon previously has been associated with negative Bti non-target effects in the short-term. We found no reduced production of chironomids at neither family, nor subfamily level in Bti-treated as compared to untreated wetlands. We conclude that other factors than the occasional Bti-treatments dominate in structuring the chironomids fauna. For example, hydrology measured as floods and hydroperiod had substantial impact on insect emergence Increased hydroperiod was associated with lower insect emergence for the majority of the studied taxa, indicating an insect fauna adapted more to terrestrial conditions. In the final study, we developed and applied a molecular method to study interspecific predator – prey relationships between medium-sized diving beetles and floodwater mosquito larvae. Gut content analyses showed that floodwater mosquito larvae are a regular, but limited, part of the diet of medium-sized diving beetles. This thesis is one of the first long-term studies of insects of temporary wetlands in relation to mosquito control actions. The results indicate that hydrology is one of the major factors influencing and structuring the insect communities of the temporary flooded wetlands in the River Dalälven floodplains, and that mosquito control actions with Bti only have marginal effect on insect abundances.

Throughout North America populations of white sturgeon (Acipenser transmontanus) are threatened, in part due to poor annual recruitment. Definitive causes for this are not yet known, but the effects of contaminants are suspected to contribute. White sturgeon are exposed to a range of contaminants as they tend to inhabit industrialized river systems such as the Columbia and Fraser. White sturgeon are not commonly studied in ecotoxicology and their vulnerability as a species to contaminants of environmental concern is not well defined. To date, few exposure studies have been conducted with larvae, fry, and/or juveniles of this species; life stages often considered most susceptible to pollutants. Specifically, little work has been conducted to characterize effects of metals on white sturgeon. In the Upper Columbia River (UCR) a population of white sturgeon has been experiencing poor annual recruitment for over thirty years, and the effects of metal pollution have been hypothesized as a potential contributing factor. In particular, Teck Metals Ltd. (Teck) operates a metallurgical facility in Trail, BC, Canada that currently discharges processed effluent into the river and historically released other metal containing tailings such as slag. There are concerns that concentrations of trace-elements, such as copper, lead, cadmium, and zinc, associated with the effluent and/or slag, might have detrimental impacts on the surrounding ecosystem, including the local white sturgeon population. In 2006, a remedial investigation and feasibility study (RI/FS) was initiated in the UCR, under the oversight of the US EPA, and this project is contributing to the portion dedicated to the risk assessment of the exposure of white sturgeon to metals. The goals of this project were to develop information on toxicity of water, sediments and associated slag to help characterize sensitivity of white sturgeon to metals, and assess associated risks of metals on the population of white sturgeon in the UCR. Previous work conducted as part of a MSc degree, examined the effects of liquid effluent released by Teck on early life stages of white sturgeon. In addition, baseline information of toxicity due to sub-chronic exposure of early life stage sturgeon to copper, cadmium, and zinc, were developed. The thesis presented herein builds upon this previous work and has three major components to further characterize sensitivity of white sturgeon to metals and risk of exposure in the UCR. Specifically, a series of acute dose-response experiments were conducted with various early life stages of white sturgeon and resulting threshold values compared to water quality standards to assess protectiveness. Sensitivity of white sturgeon to metals was characterized by conducting parallel experiments with standard test species, such as rainbow trout (Oncorhynchus mykiss) and fathead minnow (Pimephales promelas), as well as parallel field exposures in UCR water to develop water effect ratios (WERs) and assess relative bioavailability. A second set of experiments investigated whether exposure to water downstream of the metal smelter in Trail, BC affected survival or growth of white sturgeon. Mobile laboratories were situated riverside upstream and downstream of the smelter and the effects of potential contaminants within UCR water to early life stage white sturgeon were investigated under chronic exposure conditions. The third set of experiments involved characterizing UCR sediment toxicity and potential effects to sturgeon. Results from this research indicate that early life stage white sturgeon are relatively sensitive to copper, cadmium, lead, and zinc in comparison to other fishes. Sturgeon were particularly sensitive to copper, especially during early life stage development when larvae are transitioning to exogenous food. Thresholds for effects of copper on early life stage white sturgeon (LC50’s ranged between 9 and 22 μg/L) bracket water quality criteria for the protection of aquatic life (7.9 μg/L ± 1.5). This result indicated that white sturgeon in the UCR might not be adequately protected. Environmentally relevant concentrations of metals, such as copper, found in water, sediment, or waters associated with sediment of the UCR, including pore water and overlying water, may approach or exceed water quality criteria and lethal concentration (LC) values for sturgeon. Results from the risk assessment portion of this project, however, indicated that contaminants in the water column downstream of the metal smelter at Trail did not likely affect survival of white sturgeon. Dilution of Teck effluent in the river is such that, at the major spawning site where early life stages of sturgeon are likely to be present and where the riverside experiments from the present project were conducted, there would be no toxicity expected. Contaminants associated with sediments in the UCR and their impact on survival of sturgeon is also of concern as early life stages inhabit benthic habitats, on surface sediments, or in interstitial space between stones. Analytical results from this project did indicate that UCR sediment downstream of the smelter facility were significantly greater (p < 0.01) in concentrations of trace-elements, such as copper, lead, cadmium, and zinc, relative to reference sites. However, survival of white sturgeon was not adversely affected following exposure to UCR sediments. This project provided valuable information to help assess potential causes for poor recruitment of white sturgeon in the Columbia River. Advancements were made in characterizing the effects of metals to white sturgeon. In particular, life stage-specific sensitivities were identified that could have a significant impact on current risk assessment approaches and the derivation of protective water quality standards. There are several hypotheses as to why the number of white sturgeon have been decreasing in the UCR over the last few decades, but as of yet, no definitive cause for poor recruitment has been identified. As more research is conducted, possible causes for recruitment failure can be eliminated. Based on results from this project, metals in the UCR do not appear to be contributing directly to decreased survival of early life stage sturgeon.

PhD. (Chemistry) / This project assessed the toxicity of double-walled carbon nanotubes to three aquatic organisms belonging to different trophic levels, namely Pseudokirchneriella subcapitata (algae), Daphnia pulex (macro-invertebrate) and Poecilia reticulata (fish). Prior to the toxicity testing, the dry DWCNTs were characterised using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. Dynamic light scattering was used to characterise DWCNT suspensions. Natural water parameters such as increased ionic strength (Ca2+ and Na+) and increased humic acid affected the agglomeration potential of DWCNTs in aquatic medium. Increased ionic strength increased the agglomeration of DWCNTs while humic acid decreased agglomeration. The study explored the lethal/effective concentrations and sublethal effects of DWCNTs on the three organisms. The LC50/EC50 of DWCNTs for the three organisms differed in order of magnitude with D. pulex being the most sensitive and P. reticulata being the least sensitive. The LC50 for D. pulex was 2.81 and 4.45 mg/L for pristine and oxidised DWCNTs, respectively. Pseudokirchneriella subcapitata had an average EC50 of 10.01 mg/L and 10.93 mg/L for pristine and oxidised DWCNTs, respectively. Poecilia reticulata had an LC50 of 113.64 mg/L and 214.0 mg/L for pristine and oxidised DWCNTs, respectively. Exploring the effects of natural water parameters such as humic acid and ionic strength revealed that the acute toxicity of DWCNTs to D. pulex and P. reticulata was increased with increasing humic acid concentrations in exposure media, but increased ionic strength decreased the toxicity of both pristine and oxidised DWCNTs. However, these water parameters all decreased the toxicity of DWCNTs to P. subcapitata. The acute toxicity of DWCNTs was found to be directly linked to their agglomeration state in aquatic systems. Humic acid decreased the hydrodynamic sizes of DWCNT agglomerates making the engineered nanomatrials (ENMs) more available to the organisms while the cations increased the hydrodynamic sizes of DWCNT agglomerates, thereby reducing the probability of interactions with organisms. Time-based survival plots revealed that for P. reticulata and P. subcapitata, there were steady mortality/growth inhibitions throughout the duration of the exposures. For D. pulex, however, the plots revealed that there was a high initial die-off, whereafter mortalities proceeded at different rates. An assessment of whether DWCNTs cause oxidative stress in the three organisms revealed that DWCNTs caused significantly high oxidative stress in D. pulex and P. reticulata but not in P. subcapitata. In D. pulex and P. reticulata, DWCNTs were found to also cause DNA damage. The sublethal toxicity of DWCNTs was affected differently by the humic acid and increased cation concentration in exposure experiments. The sublethal effects were linked to the mode of interaction between DWCNTs and organisms. In P. subcapitata, the interaction was mainly physical with DWCNTs entrapping the algal cells in agglomerates and depriving the algal cells of light for normal photosynthesis to take place. For the other two organisms, the interaction was through intestinal cells as the organisms ingested DWCNTs and through accumulation of nanotubes on the exterior or organisms. The intestinal cell/DWCNT interaction resulted in the excessive generation of reactive oxygen species (ROS) and led to the death of the organism. Humic acid induced the highest antioxidant responses in both D. pulex and P. reticulata and this led to increased DNA damage in both organisms. Increased ionic strengths induced increased antioxidant responses at some DWCNT concentrations but the DNA damage was not significantly increased. These results suggested that with humic acid, the ROS production was excessive and sustained and had an effect on the DNA. The ROS production in increased ionic strengths was not excessive and was not prolonged, reducing their impact on DNA. The use of three organisms to assess the toxicity of DWCNTs provided comprehensive information on the potential effects of these ENMs in the aquatic food chain. Moreover, a multi-tier approach provided information on the potential effect of DWCNTs on populations at sublethal concentrations.

This study is designed to (a) demonstrate the highly productive nature of the littoral area as compared to the pelagic region, (b) the possible importance of phyco-periphyton in the diets of fish, (c) the effects of meteorological conditions on distribution of phytoplankton, and (d) a demonstration of the invalidity of using artificial substrates as a universal means of measuring productivity.

The purpose of this study was to demonstrate the variability of oxygen and carbon dioxide rate of change methods for measuring primary productivity and respiration in an aquatic environment.