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This problem was concerned with determining the total lipid content and individual lipid composition of the larvae of a local chironomid, Glyptotendipes barbipes (Staeger).

The toxicity of the metals: Cd, Cu, Pb, Ni, and Zn to the freshwater aquatic larvae of the midge fly Chironomus riparius was investigated using 24 h waterborne exposures. Even at the most sensitive life stage, first instar, the chironomids were extremely metal tolerant, with LC50 values for all metals being orders of magnitudes above both the CCME Canadian water quality guidelines for the protection of aquatic life, and the USEP A Water Quality Criteria. This high tolerance of C. riparius to metal toxicity, combined with an exceptional ability to accumulate and tolerate high internal metal burdens makes the chironomid an ideal organism to use in studies on factors affecting the trophic transfer of Cd. Zebrafish were fed with Cd-contaminated chironomids for 7 days, followed by 3 days of gut clearance with clean chironomids. Chironomids loaded with Cd by exposure to Cd-contaminated sediments exhibited a significantly higher trophic transfer efficiency (TTE) than did zebrafish 1 fed chironomids contaminated with Cd by waterborne exposure, although in both cases the TTE's were low (<2%). The majority ofCd transferred to zebrafish was stored in the gut and carcass, irrespective of ingestion of a natural diet (chironomids loaded with Cd), or a manufactured pellet diet of identical Cd concentrations. On a tissue concentration basis, the highest tissue accumulations in zebrafish were (in decreasing order): kidney> gut> liver> gill> carcass; this accumulation pattern w;ls also independent of concentration of Cd in the diet or of prey exposure route. Subcellular fractionation of chironomids found most of the Cd in the metal rich granule fraction followed by the organelle fraction. It also revealed that sediment exposed chironomids had significantly more Cd in the metallothionein-like protein fraction, and significantly less Cd in the cellular debris fraction than water-borne exposed chironomids, although these fractions accounted for only a small percent (~7%) of the total accumulated Cd. Despite this difference in prey subcellular fractionation, the subcellular storage of Cd in zebrafish fed on sediment-exposed chironomids and zebrafish fed on water-borne exposed chironomids was the same, with the highest accumulations in the organelles, enzymes, and metal rich granules fractions. Main areas of subcellular storage in zebrafish fed on a manufactured pellet food were identical to those ofzebrafish fed on chironomids. However, zebrafish fed on chironomids had significantly more Cd in the metallothionein-like protein fraction (5-10%) than did zebrafish fed on pellets :o%). Overall, TTE's were independent of concentration, but were dependent on route of prey exposure. Tissue-specific accumulations and tissue-specific distributions in zebrafish were independent of both concentration and route of prey exposure, and the gut consistently accounted for the highest proportion of overall body burden, and had the highest accumulation of all tissues; verifying its importance in preventing the internalization of Cd. Subcellular distributions were also independent of concentration, although zebrafish fed a biological food (chironomids) had more Cd in the metallothionein-like protein fraction than zebrafish fed a manufactured food. This has biological implications for Cd detoxification. / Thesis / Candidate in Philosophy

Exacerbated deep-water hypoxia, brought about by anthropogenic-derived dissolved organic carbon (DOC) input, has potentially detrimental impacts on organisms residing in freshwater ecosystems. Oxygenation of the water column is a potential management strategy to mitigate this impact, and used to alleviate DOC induced oxygen depletion. In this thesis, I investigated the effects of hypolimnic oxygenation on benthic macroinvertebrate and zooplankton biomass and size assemblages in an experimental dystrophic lake. The experiment, which took place between 2017-2020 in a dystrophic brown-water lake consisting of two interconnected basins, was performed according to a Before-After-Control-Impact design. One basin was continuously monitored under reference conditions while the oxygen concentrations of the other basin was experimentally increased halfway through the experimental period. Macroinvertebrates were sampled from the epi-, meta- and hypolimnion while zooplankton were sampled from throughout the water column (0-6 m) and, during 2020, also the hypolimnion (3-6 m) separately. Collected macroinvertebrate and zooplankton samples were analyzed for biomass, chironomid body lengths and zooplankton community compositions per basin and treatment. Mean benthic biomass, chironomid biomass and chironomid body length increased in response to oxygenation in the hypolimnion but no effect was found in the epi- or metalimnion habitats. Observed biomass responses were mainly driven by the increase in chironomid biomass. No differences were found in neither zooplankton community assemblages nor biomass following oxygenation. These results suggest that the lack of oxygen-rich habitats act as a major limiting factor for hypolimnic macroinvertebrates and especially for chironomids. Zooplankton, on the other hand, appear to be limited by resource availability as opposed to the abundance of suitable, oxygen-rich habitats only. The results suggest that oxygenation may have clear benefits for deep-water macroinvertebrates. However, as a management tool, it is ineffective as a means to increase zooplankton abundances.

Uranium mining and milling operations at Key Lake, Saskatchewan, Canada, have been releasing effluent since 1983, resulting in the accumulation of selenium in surface water, sediment, and biota in downstream lakes relative to pre-development and reference lake conditions. Elevated selenium can pose a risk to fish and bird populations in aquatic ecosystems as a result of the trophic transfer of selenium from the base of the aquatic food web. This research program was designed to address specific knowledge gaps related to the bioaccumulation of selenium at the benthic-detrital link of aquatic food webs. To fulfill this objective, laboratory and in situ field experiments were conducted using the benthic invertebrate Chironomus dilutus to identify the exposure pathway(s) and selenium species associated with the bioaccumulation of selenium by benthic invertebrates downstream from the Key Lake operation. Laboratory bioaccumulation tests that exposed midge larvae to 4.3 µg/L as dissolved selenate for 10 d resulted in negligible accumulation of selenium. However, larvae rapidly accumulated selenium over 10 d of exposure to 3.8 and 1.8 µg/L selenite and seleno-DL-methionine (Se-met), respectively. Furthermore, once selenium was accumulated by the larvae from the selenite and Se-met treatments, the majority of it was retained after a 10 d depuration period in clean water. When additional midge larvae were exposed to selenium until emergence, selenium accumulated during the larval stage was passed onto the adults following metamorphosis, with only a small percentage of the selenium (< 5%) transferred to the exuvia. Selenium speciation analysis using X-ray absorption spectroscopy showed that increases in total selenium concentrations corresponded to increased fraction of organic selenides, modeled as selenomethionine, in C. dilutus larvae and adults. Results from the 2008 in situ caging study confirmed that surface water is not a significant selenium exposure pathway for benthic invertebrates at Key Lake. Chironomus dilutus larvae accumulated between 20- and 90-fold more selenium from exposure to sediment compared to exposure to surface water in the high exposure lake. In response to these findings, a second in situ experiment was conducted in 2009 to investigate the importance of dietary selenium (biofilm or detritus) vs. whole-sediment as an exposure pathway. Larvae exposed to sediment detritus (top 2 â 3 mm of sediment) from the exposure site had the highest selenium concentrations after 10 d of exposure (15.6 ± 1.9 µg/g) compared to larvae exposed to whole-sediment (12.9 ± 1.7 µg/g) or biofilm (9.9 ± 1.6 µg/g). Biofilm had lower total selenium concentrations than the detritus and whole-sediment fractions, but nearly 80% of the selenium was present as organic selenides similar to selenomethionine. Biofilms appear to be an enriched source of organic selenium and are important food items for many benthic consumers. Integrating the separate lines of evidence that were generated during laboratory and in situ bioaccumulation tests helped strengthen the understanding of selenium accumulation in the benthic-detrital food web and subsequent trophic transfer of selenium to benthic invertebrates.

Uranium mining and milling operations at Key Lake, Saskatchewan, Canada, have been releasing effluent since 1983, resulting in the accumulation of selenium in surface water, sediment, and biota in downstream lakes relative to pre-development and reference lake conditions. Elevated selenium can pose a risk to fish and bird populations in aquatic ecosystems as a result of the trophic transfer of selenium from the base of the aquatic food web. This research program was designed to address specific knowledge gaps related to the bioaccumulation of selenium at the benthic-detrital link of aquatic food webs. To fulfill this objective, laboratory and in situ field experiments were conducted using the benthic invertebrate Chironomus dilutus to identify the exposure pathway(s) and selenium species associated with the bioaccumulation of selenium by benthic invertebrates downstream from the Key Lake operation. Laboratory bioaccumulation tests that exposed midge larvae to 4.3 µg/L as dissolved selenate for 10 d resulted in negligible accumulation of selenium. However, larvae rapidly accumulated selenium over 10 d of exposure to 3.8 and 1.8 µg/L selenite and seleno-DL-methionine (Se-met), respectively. Furthermore, once selenium was accumulated by the larvae from the selenite and Se-met treatments, the majority of it was retained after a 10 d depuration period in clean water. When additional midge larvae were exposed to selenium until emergence, selenium accumulated during the larval stage was passed onto the adults following metamorphosis, with only a small percentage of the selenium (< 5%) transferred to the exuvia. Selenium speciation analysis using X-ray absorption spectroscopy showed that increases in total selenium concentrations corresponded to increased fraction of organic selenides, modeled as selenomethionine, in C. dilutus larvae and adults. Results from the 2008 in situ caging study confirmed that surface water is not a significant selenium exposure pathway for benthic invertebrates at Key Lake. Chironomus dilutus larvae accumulated between 20- and 90-fold more selenium from exposure to sediment compared to exposure to surface water in the high exposure lake. In response to these findings, a second in situ experiment was conducted in 2009 to investigate the importance of dietary selenium (biofilm or detritus) vs. whole-sediment as an exposure pathway. Larvae exposed to sediment detritus (top 2 â 3 mm of sediment) from the exposure site had the highest selenium concentrations after 10 d of exposure (15.6 ± 1.9 µg/g) compared to larvae exposed to whole-sediment (12.9 ± 1.7 µg/g) or biofilm (9.9 ± 1.6 µg/g). Biofilm had lower total selenium concentrations than the detritus and whole-sediment fractions, but nearly 80% of the selenium was present as organic selenides similar to selenomethionine. Biofilms appear to be an enriched source of organic selenium and are important food items for many benthic consumers. Integrating the separate lines of evidence that were generated during laboratory and in situ bioaccumulation tests helped strengthen the understanding of selenium accumulation in the benthic-detrital food web and subsequent trophic transfer of selenium to benthic invertebrates.

O Estado do Tocantins está se tornando um dos principais polos de cultivo agrícola do Brasil e a disponibilidade de recursos hídricos têm fortalecido a produção agrícola no Estado. As áreas de monocultura estendem-se principalmente ao longo da bacia hidrográfica Araguaia e Tocantins, sendo estes os dois principais sistemas de drenagem. Para obtenção de elevadas produtividades, os cultivos agrícolas são altamente dependentes do uso de pesticidas. Adicionalmente, os pesticidas agrícolas podem chegar aos ecossistemas aquáticos através da lixiviação e deriva após a aplicação e também através da adsorção a materiais biológicos e às partículas de argila do solo que são carregados para sistemas aquáticos pelos processos de erosão. Consequentemente, o ecossistema aquático pode ser afetado, devido ao efeito tóxico destes pesticidas para espécies aquáticas de diferentes níveis tróficos. Como resultado de uma pesquisa de campo em várias áreas de cultivo no Estado do Tocantins, verificou-se que o inseticida tiametoxam (TMX), o fungicida ciproconazol (CPZ) e o herbicida Paraquat (PQ) estão entre os principais pesticidas utilizados em diversas culturas e em diferentes áreas de cultivo. O objetivo deste estudo foi avaliar a toxicidade de TMX, CPZ e PQ para invertebrados de água doce, de modo a contribuir para análise de risco ecológico de pesticidas agrícolas no ecossistema da bacia hidrográfica Araguaia-Tocantins. Como a informação sobre a toxicidade letal e sub-letal de diferentes compostos, particularmente para espécies aquáticas ecologicamente relevantes, é crucial para a avaliação dos riscos de pesticidas em ecossistemas aquáticos, foram realizados ensaios ecotoxicológicos, utilizando ensaios laboratoriais com dois invertebrados de água doce, o díptero Chironomus riparius e a planária Dugesia tigrina. Estudos preliminares revelaram que TMX não é tóxico para D. tigrina em concentrações ambientalmente relevantes, logo a toxicidade deste pesticida foi avaliada apenas sobre C. riparius (sobrevivência, crescimento, emergência e avaliação de respostas bioquímicas). Na avaliação da toxicidade de CPZ, os parâmetros avaliados em C. riparius incluem sobrevivência, crescimento e emergência, enquanto que em D. tigrina foram avaliados sobrevivência, regeneração e respostas comportamentais (locomoção e alimentação). Para avaliação da toxicidade de PQ, ensaios crônicos foram conduzidos com C. riparius (avaliação de crescimento, emergência e peso de mosquitos adultos) e D. tigrina (avaliação de regeneração, locomoção e alimentação). Os resultados evidenciaram que TMX é altamente tóxico para C. riparius, uma vez que concentrações ambientalmente relevantes afetam não só o desenvolvimento do organismo, mas também a sobrevivência. O fungicida CPZ é moderadamente tóxico para C. riparius (atraso no tempo à emergência) e D. tigrina (decréscimo da atividade locomotora, atividade alimentar e capacidade de regeneração). O herbicida PQ também provocou atraso no tempo à emergência, além de diminuição do tamanho dos adultos de C. riparius, bem como redução na atividade locomotora, atividade alimentar e capacidade de regeneração de D. tigrina. Este estudo acrescenta dados ecotoxicológicos sobre os efeitos de TMX, CPZ e PQ sobre invertebrados de água doce e sugere que, em longo prazo, estes pesticidas podem potencialmente perturbar cadeias alimentares e estrutura da comunidade nos ecossistemas de água doce. A aplicação destes pesticidas em particular na bacia hidrográfica Araguaia-Tocantins deve ser cuidadosamente monitorada nas áreas agrícolas de modo evitar impactos sobre os ecossistemas aquáticos. / The State of Tocantins is becoming one of the main agricultural centers in Brazil, and the availability of water resources have strengthened agricultural production in the state. Monoculture areas extend mainly along the Araguaia and Tocantins watersheds, which are the two main drainage systems. To achieve high productivity, agricultural crops are highly dependent of pesticide use. As such, agricultural pesticides may reach the aquatic ecosystems through leaching and drift after application, also through the adsorption to biological materials and soil clay particles that are carried to aquatic system by erosion. Consequently, the aquatic ecosystem may be affected due to the toxic effect of these pesticides to aquatic species of different trophic levels. As a result of a field survey of several areas of cultivation in the State of Tocantins, it was found that the insecticide thiamethoxam (TMX), the fungicide cyproconazole (CPZ) and the herbicide paraquat (PQ) are the main pesticides used in many crops, in different areas of cultivation. The aim of this study was to evaluate the toxicity of TMX, CPZ and PQ for freshwater invertebrates, in order to contribute to ecological risk assessment of agricultural pesticides in the ecosystem of the Araguaia-Tocantins watershed. Since information on the lethal and sub-lethal toxicity of the different compounds, particularly for ecologically relevant aquatic species, is crucial for risk assessment of pesticide in aquatic ecosystems, ecotoxicological tests were carried using laboratory tests with two freshwater invertebrates, the dipteran Chironomus riparius and the planarian Dugesia tigrina. Preliminary studies revealed that environmentally relevant concentrations of TMX is did not induced toxicity to D. tigrina and thus, effects of this insecticide were evaluated only using C. riparius (survival, growth, emergence and evaluation of biochemical responses). In the evaluation of CPZ toxicity, the endpoints evaluated in C. riparius included survival, growth and emergence, while in D. tigrina effects were evaluated in terms of survival, regeneration and behavioral responses (locomotion and feeding). For the assessment of PQ toxicity, chronic tests were conducted with C. riparius (growth, emergence and adult weight) and D. tigrina (regeneration, locomotion, and feeding). Our results showed that TMX is highly toxic to C. riparius, since environmentally relevant concentrations affects not only the development rates, but also survival. The CPZ fungicide is moderately toxic to C. riparius (delayed emergence time) and D. tigrina (decreased locomotor activity, feeding activity and delayed regeneration). The herbicide PQ also caused a delay in emergence time and decrease in body weight of C. riparius imagos, as well as reduction in locomotor activity, feeding activity and regeneration of D. tigrina. This study adds ecotoxicological data on the effects of TMX, CPZ and PQ to freshwater invertebrates and suggests that in the long term, these pesticides can potentially disrupt food chains and community structure in freshwater ecosystems. The application of these pesticides namely in the Araguaia-Tocantins watershed should thus be closely monitored in agricultural areas in order to avoid impacts on aquatic ecosystems.

Fossil midge remains from a sediment core from Lake Stowell, Saltspring Island (48°46’54”N, 123°26’38”W) were used to produce quantitative estimates of mean July air temperature over the last 14,000 years. Chironomid and Chaoborus remains were identified, and multiple models of past temperatures based on transfer functions of northern North American calibration datasets were evaluated. The selected model was used to create the first quantitative paleotemperature estimates for the Gulf Islands region. Inferred paleotemperatures at Lake Stowell varied between 12.1 °C and 18.6 °C over the last 14,000 calendar years. Several major climate phases were identified based on changes in paleotemperature. The base of the record is characterised by a cool lateglacial interval with a minimum inferred July temperature of 12.1 °C. Inferred temperatures generally increased by ~4 °C between ~14,200 and 10,300 cal yr BP but this warming was interrupted by cooling, coincident with the Younger Dryas Chronozone, when inferred temperatures drop ~2 °C from the temperatures immediately preceding this interval. A warm early Holocene extends from ~10,300 to 8100 cal yr BP with temperatures regularly exceeding 16 °C. Following the early Holocene, inferred temperatures decreased to approximately 14.9 °C in the mid-Holocene. After a brief warm peak in the late Holocene, inferred temperatures cooled towards the present. Inferred changes in paleotemperature from Lake Stowell are consistent with other paleoenvironmental studies conducted in southern British Columbia and throughout much of the Northern Hemisphere. Temperature changes at Lake Stowell are muted in comparison to continental sites, which may be due to the influence of marine conditions. This research provides context for other studies in the region, and contributes to our understanding of environmental change since the last glacial maximum. / Graduate / 2017-08-17 / 0426 / 0793 / 0353 / jillian.lemmen@gmail.com

M.Sc. (Aquatic Health) / Sediments can contain a variety of organic and inorganic contaminants. These contaminants accumulate, resulting in extremely high concentrations even once the overlying water concentrations are at or below acceptable water quality guidelines. Any changes in the physical parameters of the overlying water can cause these pollutants to be released back into solution. Accumulated contaminants can be released at even higher concentrations than previously detected. In recent years, sediment contamination has highlighted the need to monitor these previously overlooked pollutant sources that have accumulated in aquatic ecosystems. South Africa does not currently have standardised methods to assess sediment toxicity. Although international methods exist, they are largely untested in South Africa and the organisms needed to conduct these tests are not readily available. Over the years numerous culture methods have been develop globally for culturing organism to be used for water and sediment toxicity tests. In South Africa, the focus has mainly been on culturing organisms for water toxicity testing. Sediment toxicity testing with indigenous organism however, was not developed. Established international culture methods from the United States Environmental Protection Agency, the Organisation for Economic Cooperation and Development, and Environment Canada were taken into consideration when developing the laboratory culture method for two(2) of the selected organisms (Chironomus spp. & Hydra sp.) from this study. A preliminary culture method was also developed for the third selected organism, Melanoides tuberculata (gastropod). The organisms cultured in this study were selected based on their extent of contact with the substrate, ease of handling, availability, culture maintenance as well as their reproductive cycle. The Hydra, Chironomids and M. tuberculata cultures were successfully breeding under laboratory conditions and remained stable. The Chironomus sp. and M. tuberculata maintain contact with the sediment making them suitable as ecologically relevant organisms for use in whole sediment toxicity testing in South Africa.

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