<p>The analysis of geologic, hydrologic and hydrogeologic data interpreted to give the characteristics of the Cape Flats aquifer showed the quality of groundwater from the aquifer is suitable for development as a water resource. The conceptual model of the Cape Flats sand shows an unconfined sandy aquifer, grading into semi-confined conditions in some places where thick lenses of clay and peat exists. Recharge rates through the saturated zone of the Cape Flats aquifer have been determined by water table fluctuation (WTF), rainfall-recharge relationship, soil water balance and chloride mass balance methods (CMB). Recharge rates using the WTF vary considerably between wet and dry years and between locations, with a range of 17.3% to 47.5%. Values obtained from empirical rainfall-recharge equation (method 2) agree with those of the WTF. Recharge estimates from the water balance model are comparatively lower but are within the range calculated using empirical method 2 (i.e. 87 &ndash / 194 mm or 4 &ndash / 21% of MAP). These recharge rates also agree with estimates from the series of other methods applied to sites located in the north-western coast of Western Cape and are comparable to recharge rates obtained elsewhere in the world.</p>

Im Fokus der Untersuchungen steht das hydrologische Einzugsgebiet der oberen Wilzsch im Westerzgebirge. Veränderte Stoffausträge des bewaldeten und zum Teil vermoorten hydrologischen Einzugsgebietes führen zu erhöhten Stoffkonzentrationen im Hauptzufluss der Trinkwassertalsperre Weiterswiese (Carlsfeld). Seitens der Trinkwasseraufbereitung stellen insbesondere die gestiegenen Gehalte an gelösten organischen Kohlenstoffen (DOC) Mehraufwendungen dar. Im Zuge der Wiedervernässung der Moorflächen kommt es zu relevanten bodenchemischen Veränderungen, die im Abfluss messbar sind. Eine räumliche Betrachtung der Teileinzugsgebiete des hydrologischen Einzugsgebietes der oberen Wilzsch ermöglicht, das Abflussgebiet in verschiedene Herkunftsräume zu gliedern. Dieser raumbezogene Ansatz leistet einen wesentlichen Beitrag in der Herkunftsanalytik von Wässern, deren Fließwege durch Standorte unterschiedlicher Nutzung geprägt sind. Die Arbeit bedient sich hydrochemischen Analysen sowie multitraceranalytischen Verfahren. Die Analyse der stabilen Umweltisotope ²H und 18O am Wasser, 13C am DIC und DOC, 34S und 18O am Sulfat sowie 15N und 18O am Nitrat hilft bei der Identifizierung von Stoffquellen und Transformationsprozessen. Die Arbeit verfolgt das Ziel, den Beitrag der verschiedenen Stoffsysteme am gesamten Stoffaustrag des Vorfluters aufzuzeigen sowie die atmosphärische Grundlast an den Messstandorten nachzuweisen. Dazu wurden von Mai 2009 bis August 2010 fünf Beprobungskampagnen angelegt. Das Messdesign erstreckte sich auf 19 Standorte in ausgewählten Teileinzugsgebieten, die maßgeblichen Einfluss auf die Vorflut haben. Parallel dazu erfolgte die Untersuchung des Niederschlags an der Station Talsperre Weiterswiese. Erfasst wurden die Inhalte von Wässern verschiedener Moorgebiete, Moorwasserpegel unterschiedlich degradierter Moorbereiche, Gräben und Bodendrainagen im Fichtenforst, der Vorfluter Wilzsch und Kranizsch und des Grundwassers im Fichtenforst. Es kann festgehalten werden, dass je nach Lage bzw. Entfernung der Ursprungsgebiete der Anteil des DOC - Exports unterschiedlich stark ist. So sind die DOC - Austräge saisonal sehr verschieden. Im Ergebnis ist der hydrochemische Beitrag - im Besonderen DOC - der unterschiedlichen Stoffsysteme des hydrologischen Einzugsgebietes letztlich am finalen Pegel der Wilzsch messbar. Die vom Basisabfluss gesteuerten silikatischen Standorte im Fichtenforst leisten einen wesentlichen Anteil zum hydrochemischen Milieu der Vorfluter. Die im Untersuchungsgebiet eingeleiteten Renaturierungsmaßnahmen beeinflussen die Trinkwasserqualität in der Talsperre Carlsfeld nicht. Eine Abgrenzung der atmosphärischen Grundlast ist ebenfalls möglich, atmogen eingetragene Stoffe können an den Standorten ausgewiesen werden.

Increases in global temperatures resulting from climate change have raised concern over potential responses of Arctic charr, <i>Salvelinus alpinus</i>, a cold-adapted freshwater/anadromous fish species in the salmonid family. While various aspects of adult Arctic charr ecology are well established, juvenile, and in particular, young-of-the-year (YOY) ecology is less well understood. The study of early life stages is important because of implications for subsequent population dynamics as well as their particular sensitivity to climate change. In this thesis, I aimed to broaden the scope of knowledge on juvenile Arctic charr from Canadian populations with a particular emphasis on YOY, and thermal habitat use through four studies. An intensive study of juvenile Arctic charr from Lake Hazen, Nunavut, demonstrated a preference during the summer for stream environments, particularly those fed by warm upstream ponds. Charr occupying both stream and nearshore lake habitats were found to feed similarly, with chironomids occurring most frequently in diets. Some older stream-dwelling charr preyed on smaller, younger Arctic charr. Preferred stream occupancy is likely mediated by physical barriers created mainly by water velocity, and by distance from the lake, lake-ice dynamics, low water depth, and turbidity. Water velocities and possibly intercohort competition resulted in stream habitat segregation by size, with YOY mainly found in low velocity pools and back eddies adjacent to stream banks, but not in water velocities greater than 0.1m/s. Greatest charr densities in streams were found in small, shallow, slow-flowing side channels, which are highly susceptible to drought. A discriminant function analysis model based on carbon and nitrogen stable isotope values was used to identify offspring of piscivorous large-form and non-piscivorous small-form Arctic charr morphotypes from Lake Hazen, Nunavut. The adult morphotypes were estimated to contribute approximately equally to the YOY population, however, the morphotype offspring were differentially distributed among sampled nursery sites. Unequal distribution corresponds with prerequisites suggested for the evolution of trophic specialists within a single population that experiences assortative mating based on trophic specialization. An assessment of growth rates and otolith-inferred metabolic rates obtained from YOY from 23 populations over a 27˚ latitudinal gradient demonstrated latitudinal variability consistent with countergradient variation where northern populations demonstrated faster growth and higher metabolic rates compared to southern populations. Countergradient variation (CGV) is defined as genetic variation that counteracts the negative influences of the physical environment, minimizing phenotypic variability along a gradient. Otolith-inferred metabolic rates from free-living animals reflect the average daily energy expenditure of the organism, which incorporate the energetic costs of standard metabolic rate (SMR) and other processes such as feeding, locomotion, thermoregulation, reproduction and growth. As such, variations in otolith-inferred metabolic rates may reflect a combined increase in feeding, activity and SMRs in northern populations. Nevertheless, the phenotypic variation in physiological traits observed here demonstrates the significant adaptability of Arctic charr to different thermal regimes with different growing season lengths. Otolith-inferred temperatures and fork lengths at capture from YOY from two proximal fluvial and lacustrine sites in Labrador were used to compare growth and thermal habitat use between habitat types. Otolith-inferred temperatures were not significantly correlated with air temperatures, suggestive of behavioural thermoregulation by YOY at both sites. The majority of YOY from Kogluktokoluk Brook (fluvial) were found using temperatures consistent with laboratory determined preferred temperatures for juvenile Arctic charr, whereas most Tom’s Pond (lacustrine) YOY were found using temperatures ranging between preferred temperatures and optimal temperatures for growth. Otolith-inferred temperatures were only correlated to fork lengths in Tom’s Pond YOY. The lack of correlation in Kogluktokoluk Brook YOY may reflect resource partitioning occurring as a result of territoriality known to occur among stream salmonids. The limited range of temperatures used by fluvial YOY in this study, particularly the lack of cooler temperatures, suggests that fluvial YOY may face barriers to accessing thermal refugia, and as a result may be particularly vulnerable to climate change. Examining the ecology of juvenile Arctic charr from Canadian populations over a number of spatial scales (i.e. latitudinal, regional and local) highlighted the considerable phenotypic plasticity demonstrated by the species. While physiological plasticity observed over the latitudinal gradient reflected the ability for juvenile Arctic charr to utilize different thermal regimes, the regional comparison between habitat types demonstrated that the ability for juvenile Arctic charr to respond to climate change is likely to vary between habitat types. Further, on a local scale, behavioural plasticity was observed, but was found to be influenced by several regulatory factors. The study of the ecology of juvenile Arctic charr in this thesis has highlighted various factors affecting juvenile Arctic charr in Canada: temperature, water velocity, cover, maternal influences, habitat type and ration. The relative contributions of these factors as well as others which were not directly testable in this thesis (e.g. variability in standard metabolic rate, the role of genetic adaptation) are likely to vary with latitude, populations and habitat types. Deciphering the relative roles of these factors will allow better predictions of responses to climate change.

Background: The high prevalence of iron deficiency and anaemia among South African children highlights the need for iron fortification, especially with a highly bioavailable iron compound. Fortification of staple foods is an adequate strategy to provide additional iron to populations at risk. In South Africa it is mandatory to fortify maize meal and wheat flour with iron, as well as other micronutrients. Elemental iron, specifically electrolytic iron, is currently the preferred choice but other compounds that might be more effective in alleviating iron deficiency are under consideration. Objectives: The objective of this study was to provide information about the bioavailability of ferrous fumarate and NaFeEDTA from maize meal porridge in young children, which would assist in selecting a bioavailable alternative to electrolytic iron in the South African National Food Fortification Programme, Methods: A randomized parallel study design was used, with each of the 2 groups further randomised to receive either one of two test regimens in a crossover design in which each child acted as his/her own control. Iron bioavailability was measured with a stable-isotope technique based on erythrocyte incorporation 15 days after intake. Results: The mean absorption of iron from NaFeEDTA and ferrous fumarate from the maize porridge meal was 11.5% and 9.29% respectively. NaFeEDTA and ferrous fumarate are both sufficiently bioavailable from a maize based meal rich in phytates. Conclusion: Both NaFeEDTA and ferrous fumarate would provide a physiologically important amount of iron should they replace electrolytic iron as fortificant in maize flour fortification. The final choice between ferrous fumarate and NaFeEDTA as when it comes to finding the alternative iron fortificant will depend on factors such as technical compatibility, bioavailability, relative cost and organoleptic characteristics. / Thesis (Ph.D. (Nutrition))--North-West University, Potchefstroom Campus, 2007

I used natural abundances of stable isotopes (δ13C and δ15N) to examine the food web structure of lake zooplankton communities. I focused on modeling isotopic variation with respect to trophic variation (δ15N) and to variation in dietary carbon sources (δ13C). The isotopic patterns suggest that zooplankton food webs have reticulate connections between food chains, and a large diversity of interactions between consumers and their resources. Variation in the δ13C of zooplankton depended on taxonomic identity, body composition, and habitat specialization. In Sooke Lake Reservoir, seasonal variation in the δ13C of zooplankton was mainly related to variation in lipid content and the δ13C of lipids. This has significant consequences for interpreting the pathways of terrestrial carbon through plankton food webs. In Council Lake, variation in the δ13C of zooplankton among taxa was related to habitat specialization, and indicates taxon- specific exploitation of allochthonous resources. Using a cage experiment, I confirmed that δ13C can indicate habitat specialization of zooplankton. Among lakes, my data suggest that zooplankton communities can readily exploit carbon produced below the epilimnion. Large inter- and intra-lake variation in the δ15N of zooplankton suggests significant trophic variation within zooplankton communities. In a year-long study, annual averages of taxa specific δ15N matched our expectations about the feeding ecology of zooplankton. However, short-term variation in the δ15N of herbivorous zooplankton (like Daphnia) was decoupled from seasonal variation in the δ15N of invertebrate predators. This suggests there are multiple food chains within the plankton community (i.e. grazing chain, microbial chain), and that the strength of each food chain may vary among lakes or seasonally within a lake. This seasonal variation in the food web structure of zooplankton has significant consequences for how we model and consider the trophic position of individual fish.

First Nations peoples experience many benefits from eating locally-harvested wild foods, but these benefits must be considered along with the potential risks associated with exposure to environmental contaminants. Unlike store-bought foods, wild foods are an important traditional resource and a significant source of dietary protein, essential minerals and polyunsaturated fatty acids, believed to help in the prevention and treatment of obesity and obesity-related diseases such as type-2 diabetes mellitus. Wild foods continue to be an important and healthy food choice for First Nations peoples; however, they are also a primary source of dietary mercury, polychlorinated biphenyls (PCBs) and other persistent organic pollutants (POPs). To assess the effects of wild food consumption on dietary markers and contaminant accumulation, we grouped individuals from two remote Oji-Cree First Nations communities of north-western Ontario (n=71) according to their level of wild food consumption. In this study, I observed significantly higher organic contaminants in blood and higher mercury concentrations in hair for individuals consuming greater amounts of wild food. Age-adjusted contaminant concentrations were on average 3.5-times higher among high-frequency wild food consumers, with many exceeding federal and international health guidelines for mercury and PCB exposures. Contaminants in these populations approach, and in some cases exceed, threshold levels for adverse effects with potential consequences especially for prenatal development. Here, I also investigated the potential for stable isotope ratios of carbon and nitrogen (δ13C and δ15N) to serve as dietary markers and found strong positive correlations between stable isotopes and frequency of wild food and fish consumption. Frequency of fish consumption and δ15N was also shown to be positively correlated with mercury concentrations in hair and PCB concentrations in plasma. The results of this thesis demonstrate that known differences in dietary behaviour are clearly reflected in stable isotope ratios and contaminant concentrations. The data also show that contaminant exposures to those consuming wild foods in remote Boreal ecosystems is comparable to those associated with serious health effects in industrialized areas, and the problem of contaminants in wild foods is more widespread than the available literature would have led us to believe. These results affect our appreciation of contaminant exposures to First Nations peoples and will have implications for dietary choices, particularly if individuals are encouraged to consume greater amounts of wild foods for their proposed health benefits. We recommend further attention be given to the risks of contaminants in locally-harvested wild foods when promoting the benefits of their consumption to First Nations people as the problem of contaminants in remote communities practicing traditional lifestyles is often underreported and underplayed.

This thesis describes a method for calculating lake evaporation as a proportion of water inputs (E/I) for large surface water bodies, using stable isotope ratios of oxygen (18O/16O) and hydrogen (2H/1H) in water. Evaporation as a proportion of inflow (E/I) is calculated for each Laurentian Great Lake using a new dataset of 516 analyses of δ18O and δ2H in waters sampled from 75 offshore stations during spring and summer of 2007. This work builds on previous approaches by accounting for lake effects on the overlying atmosphere and assuming conservation of both mass and isotopes (18O and 2H) to better constrain evaporation outputs. Results show that E/I ratios are greatest for headwater Lakes Superior and Michigan and lowest for Lakes Erie and Ontario, controlled largely by the magnitude of hydrologic inputs from upstream chain lakes. For Lake Superior, stable isotopes incorporate evaporation over the past century, providing long-term insights to the lake’s hydrology that may be compared to potential changes under a future – expectedly warmer – climate. Uncertainties in isotopically derived E/I are comparable to conventional energy and mass balance uncertainties. Isotope-derived E/I values are lower than conventional energy and mass balance estimates for Lakes Superior and Michigan. The difference between conventional and isotope estimates may be explained by moisture recycling effects. The isotope-based estimates include only evaporated moisture that is also advected from the lake surface, thereby discounting moisture that evaporates and subsequently reprecipitates on the lake surface downwind as recycled precipitation. This shows an advantage of applying an isotope approach in conjunction with conventional evaporation estimates to quantify both moisture recycling and net losses by evaporation. Depth profiles of 18O/16O and 2H/1H in the Great Lakes show a lack of isotopic stratification in summer months despite an established thermocline. These results are indicative of very low over-lake evaporation during warm summer months, with the bulk of evaporation occurring during the fall and winter. This seasonality in evaporation losses is supported by energy balance studies. For Lakes Michigan and Huron, the isotope mass balance approach provides a new perspective into water exchange and evaporation from these lakes. This isotope investigation shows that Lake Michigan and Lake Huron waters are distinct, despite sharing a common lake level. This finding advocates for the separate consideration of Lake Michigan and Lake Huron in future hydrologic studies.

Soils of Northern Hemisphere forests contain a large part of the global terrestrial carbon (C) pool. Even small changes in this pool can have large impact on atmospheric [CO2] and the global climate. Soil respiration is the largest terrestrial C flux to the atmosphere and can be divided into autotrophic (from roots, mycorrhizal hyphae and associated microbes) and heterotrophic (from decomposers of organic material) respiration. It is therefore crucial to establish how the two components will respond to changing environmental factors. In this thesis I studied the effect of elevated atmospheric [CO2] (+340 ppm, 13C-depleted) and elevated air temperature (2.8-3.5 oC) on soil respiration in a whole-tree chamber (WTC) experiment conducted in a boreal Norway spruce forest. In another spruce forest I used multivariate modelling to establish the link between day-to-day variations in soil respiration rates and its δ13C, and above and below ground abiotic conditions. In both forests, variation in δ13C was used as a marker for autotrophic respiration. A trenching experiment was conducted in the latter forest in order to separate the two components of soil respiration. The potential problems associated with the trenching, increased root decomposition and changed soil moisture conditions were handled by empirical modelling. The WTC experiment showed that elevated [CO2] but not temperature resulted in 48 to 62% increased soil respiration rates. The CO2-induced increase was in absolute numbers relatively insensitive to seasonal changes in soil temperature and data on δ13C suggest it mostly resulted from increased autotrophic respiration. From the multivariate modelling we observed a strong link between weather (air temperature and vapour pressure deficit) and the day-to-day variation of soil respiration rate and its δ13C. However, the tightness of the link was dependent on good weather for up to a week before the respiration sampling. Changes in soil respiration rates showed a lag to weather conditions of 2-4 days, which was 1-3 days shorter than for the δ13C signal. We hypothesised to be due to pressure concentration waves moving in the phloem at higher rates than the solute itself (i.e., the δ13C–label). Results from the empirical modelling in the trenching experiment show that autotrophic respiration contributed to about 50% of total soil respiration, had a great day-to-day variation and was correlated to total soil respiration while not to soil temperature or soil moisture. Over the first five months after the trenching, an estimated 45% of respiration from the trenched plots was an artefact of the treatment. Of this, 29% was a water difference effect and 16% resulted from root decomposition. In conclusion, elevated [CO2] caused an increased C flux to the roots but this C was rapidly respired and has probably not caused changes in the C stored in root biomass or in soil organic matter in this N-limited forest. Autotrophic respiration seems to be strongly influenced by the availability of newly produced substrates and rather insensitive to changes in soil temperature. Root trenching artefacts can be compensated for by empirical modelling, an alternative to the sequential root harvesting technique.

This thesis investigates the prehistoric diet of humans and two of their key commensals on Aitutaki using stable carbon and nitrogen isotopes. This technique gives us new insight into the diet of these three groups and results are considered in the context of the development of agricultural systems on Aitutaki, as well as in light of the wider context of cultural developments and environmental change in the Cook Islands and Polynesia as a whole. Ultimately, it allows us to more fully understand the complex interactions between humans and the two largest commensals in order to evaluate the utility of these animals as proxies for humans in dietary analyses. The results indicate that the prehistoric human diet on Aitutaki can be characterised as mixed, dominated by terrestrial plants and marine protein with lesser amounts of terrestrial protein. While the amount of protein eaten by the individuals was very similar, they varied in how much marine or terrestrial protein they ate. The pigs had a slightly more terrestrial diet, with a greater emphasis on plant foods. Their protein intake was more variable and terrestrial in nature than the humans’. Dogs had a higher trophic level, more marine-oriented, diet than either humans or pigs. Like the humans, their diet contained more variation in the source of their protein. Overall, however, the diets of all three groups were very similar. While the overall nature of the human, pig and dog diets, and their relationships to one another, remained relatively constant over time, beginning in the 14th century they show a decline in the amount of fish consumed and had a more terrestrial diet overall. This confirms trends seen in the archaeofaunal assemblages, and throws light on the relationship between environmental change and human subsistence practices in East Polynesia. The similarity of the pig and dog diets to human diet, and the fact that the relationship remained constant over time, demonstrates the usefulness of the Aitutaki commensal animals as proxies for humans in stable isotope analysis. However, the specifics of that relationship vary by species and by place. While the individual dietary variability provides us with new ways of looking at dietary change within populations, it also demonstrates the importance of obtaining as large an assemblage for analysis as possible in order to ensure that samples are representative of the population as a whole.

This thesis investigates the prehistoric diet of humans and two of their key commensals on Aitutaki using stable carbon and nitrogen isotopes. This technique gives us new insight into the diet of these three groups and results are considered in the context of the development of agricultural systems on Aitutaki, as well as in light of the wider context of cultural developments and environmental change in the Cook Islands and Polynesia as a whole. Ultimately, it allows us to more fully understand the complex interactions between humans and the two largest commensals in order to evaluate the utility of these animals as proxies for humans in dietary analyses. The results indicate that the prehistoric human diet on Aitutaki can be characterised as mixed, dominated by terrestrial plants and marine protein with lesser amounts of terrestrial protein. While the amount of protein eaten by the individuals was very similar, they varied in how much marine or terrestrial protein they ate. The pigs had a slightly more terrestrial diet, with a greater emphasis on plant foods. Their protein intake was more variable and terrestrial in nature than the humans’. Dogs had a higher trophic level, more marine-oriented, diet than either humans or pigs. Like the humans, their diet contained more variation in the source of their protein. Overall, however, the diets of all three groups were very similar. While the overall nature of the human, pig and dog diets, and their relationships to one another, remained relatively constant over time, beginning in the 14th century they show a decline in the amount of fish consumed and had a more terrestrial diet overall. This confirms trends seen in the archaeofaunal assemblages, and throws light on the relationship between environmental change and human subsistence practices in East Polynesia. The similarity of the pig and dog diets to human diet, and the fact that the relationship remained constant over time, demonstrates the usefulness of the Aitutaki commensal animals as proxies for humans in stable isotope analysis. However, the specifics of that relationship vary by species and by place. While the individual dietary variability provides us with new ways of looking at dietary change within populations, it also demonstrates the importance of obtaining as large an assemblage for analysis as possible in order to ensure that samples are representative of the population as a whole.