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Thesis (M.A.(Biokinetics, Sport and Leisure Sciences))--University of Pretoria, 2002. / Summary in English and Afrikaans. Includes bibliographical references.

<p> In large, seasonally dynamic and spatially complex watersheds, the availability and relative importance of various food resources for stream fishes can be expected to vary substantially. While numerous studies have attempted to uncover the trophic linkages that support stream salmonids, much of these efforts have occurred at small scales that disregard variability of food resources inherent in lotic systems. This study aimed to determine large-scale patterns in the contributions of freshwater, terrestrial, and marine-derived food resources to juvenile Chinook and Coho salmon (<i>Oncorhynchus tshawytscha</i> and <i>O. kisutch</i>) in the large, glacially influenced Susitna River, Alaska. I quantified diet patterns both spatially, across different macrohabitat types positioned along a 169-km segment of the river corridor, and temporally, from June to October, using stable isotope and stomach content analyses. To further resolve energy pathways from basal carbon sources to juvenile salmon, I determined the relative roles of terrestrial organic matter and freshwater periphyton food sources to aquatic benthic invertebrate diets. The latter analysis showed that invertebrate consumers were more reliant on freshwater periphyton than on terrestrial organic matter. Bayesian stable isotope mixing models indicated that juvenile salmon in the middle Susitna River were, in turn, largely supported by freshwater invertebrate prey regardless of spatial and temporal context. The relative contribution of marine-derived prey (salmon eggs) to juvenile salmon diets was greatest in the fall within tributary mouth and off-channel macrohabitats during both years of the study. Terrestrial invertebrate prey contributions were generally greatest during mid-summer within all macrohabitat types sampled, however this pattern varied across years. No upstream to downstream diet pattern was apparent from the data. These results underscore the importance of freshwater energy pathways for sustaining juvenile Chinook and Coho salmon in the Susitna River and provide further spatial and temporal context for the importance of pulsed marine and terrestrial prey subsidies. As Pacific salmon stocks continue to decline, management and mitigation efforts should operate on knowledge gained from studies that encompass the large-scale spatial and temporal variability inherent in riverine landscapes.</p>

In order to study the behaviour of pathogenic viruses in groundwater, several tracer experiments were performed at chalk aquifer sites using three different bacteriophage. Laboratory experiments were performed in parallel to investigate the efficacy of the bacteriophage as models of pathogenic virus behaviour. The high titres per ml of bacteriophage available for the initial inoculum and the simplicity of the assay permitted the detection of a pattern of bacteriophage recovery from three different groundwater sites. The greatest percentage of original inoculum recovered was 1.9 percent. Bacteriophage were observed to migrate 1km over a five month period and 366m within just over 3.5 hours. The laboratory experiments explored: i) decay rates of viruses suspended within chalk groundwater; ii) adsorption of viruses to chalk in batch studies and; iii) virus behaviour in chalk columns representing natural aquifer conditions. Three human enteric viruses were used: poliovirus 1, echovirus 1 and coxsackievirus B5. In addition the simian rotavirus (SA-11), and a group of bacteriophage were tested. The laboratory experiments indicated that the bacteriophage included in this study survived longer than the animal viruses in groundwater and that all viruses adsorbed well to chalk. In the simulated aquifer conditions all viruses investigated percolated through a chalk column at a similar rate and with a similar pattern. No differences in behaviour between the viruses, whether in laboratory or field experiments, was found which could be directly attributed to their size or shape. A mathematical model was used which included coefficients for adsorption and decay observed in the laboratory experiments and certain other parameters found in one of the field sites under investigation. Those factors considered and included in the model were shown to be sufficient to produce the same behaviour pattern as that observed in the field. This confirmed that the main factors influencing viral migration in natural conditions have been considered in this investigation. Bacteriophage were found to be good tracers for determining certain properties of chalk aquifers and a potential model of the behaviour of human enteric viruses in groundwater.

<p> Gamefish populations in North America are experiencing increasingly elevated recreational fishing pressures; however, the impacts of current fishing regulations have not been evaluated for most marine species. Mandatory catch and release often results from size and bag limits with the assumption of fish survival and recovery with minimal sublethal effects. Depending on the intensity and duration of the stressor, acute stress from angling and handling can have deleterious physiological and behavioral impacts with consequences for fish health and fitness. We evaluated the short-term sublethal effects of angling-related stressors on kelp bass, <i>Paralabrax clathratus</i>, one of the most popular gamefish in southern California. Collaborating with recreational anglers to capture fish using standard hook and line practices, we evaluated biochemical responses and recovery by collecting blood samples at different time points after capture (10-120 min), after fish were released and some were recaptured (3h to 186 d). Blood cortisol, glucose, and lactate were significantly elevated and steadily increased in the hour following capture and holding (p &lt; 0.001). Fish caught, released, and recaptured after varying time at liberty were found to have returned to basal levels in &lt; 24 h (p > 0.05). Physiological stress responses were positively correlated with angling and handling duration, but negatively correlated with increasing fish size (p &lt; 0.05), suggesting that larger individuals may be more resilient to capture stress. Likewise, kelp bass exhibited no signs of cumulative or chronic stress from repetitive angling/recapture events and recovered to basal levels in &lt;24 h (p > 0.05). Kelp bass were also tagged with acoustic accelerometer transmitters and tracked to evaluate fine-scale behavioral effects of angling stress on their normal diel movement and activity. Reduced frequency of high acceleration movements (i.e. rapid feeding strikes) was observed for 33 h post-release, followed by recovery and evidence of elevated feeding behavioral activity. Rate of movement and area use size showed high individual and temporal variation; however, reduced movement immediately after release steady increased to normal levels over the first 10 h post-release. There was no discernable effect of angling on area use size, but areas of high relief substratum may be important refuge habitat for angled kelp bass during recovery. By integrating physiological and behavioral endpoints for kelp bass to standard angling induced stress we conclude that this species is able to recover in &lt;24 h; however, smaller individuals may be more susceptible to predation during this recovery period. Based on these findings, it is likely that kelp bass may still fair well under current size and bag limits.</p><p>

No description available.

Dissolved organic matter (DOM) is the largest reservoir of organic matter in the ocean containing the same amounts of carbon as atmospheric carbon dioxide. DOM consists of a mixture of compounds ultimately originating from terrestrial and aquatic plant, and microbial materials. The complex chemical composition of DOM results in varying availability to microbes, containing a pool that is readily utilized by heterotrophic bacteria and a refractory part that resists biological degradation. In this study the seasonal variation in bioavailability of DOM was quantified in two contrasting marine systems: Loch Creran (Scotland) and the Ría de Vigo (Spain). The bioavailable DOM (BDOM) varied temporally at both stations and controlled the seasonal variations in DOM. Dissolved organic phosphorus (DOP) was found to be more bioavailable than dissolved organic nitrogen (DON) and DON was more bioavailable relative to dissolved organic carbon (DOC). The variation in BDOM was, in both areas, associated with changes in chlorophyll a. The DOM rate constants were observed to vary seasonally and they demonstrated that higher BDOM concentrations would lead to faster mineralization rates. Calculations from both areas suggested that they exported BDOM, which could contribute to bacterial production in the adjacent waters. It is shown that BDOM produced in the Ría de Vigo, with a half life time of 1.9 - 3.3 days, is significantly more labile than that produced in Loch Creran, with a half life time of 6 - 13 days. A fraction of DOM is coloured containing a part that absorbs (CDOM), and a part that absorbs and reemits the energy again (Fluorescence, FDOM). The relation between the optical properties of DOM and the bioavailability of DOC was tested in the Ría de Vigo. This study demonstrated that it was possible to derive both the bioavailable DOC and its rate constants from the DOM protein-like fluorescence, whereas refractory DOC could be estimated from in situ CDOM and humic-like substances in the Ría de Vigo. Heterotrophic microbes have often been viewed as the main consumers of DOM, but it is now evident that they can also produce DOM. The heterotrophic microbial production of DOM was studied using microbial communities from Loch Creran. The experiments demonstrated that the microbes produced refractory and labile DOM with a coloured signal.

abstract: Phosphorus (P), an essential nutrient for growth of all organisms, is often in limited biological supply for herbivore consumers compared to other elements, such as carbon (C). Ecological stoichiometry studies have assessed responses of filter-feeding zooplankton from the genus Daphnia to single and multi-species food resources that are P-limited, finding decreased growth as a result to changes in metabolic processes and feeding behavior. Conversely, recent laboratory studies have shown that P-rich algal food resources also result in decreased growth rates for Daphnia, though the possible mechanisms behind this maladaptive response is understudied. Moreover, no published study tests the existence of the “stoichiometric knife edge” hypothesis for low C:P under field conditions. To address this lack of information, I measured growth rate as well as respiration and ingestion rates for D. magna, D. pulicaria, and D. pulex that were fed natural lake seston experimentally enriched with different levels of PO43-. I found heterogeneous effects of high dietary P across Daphnia species. Growth rate responses for D. magna were strong and indicated a negative effect of high-P, most likely as a result to decreased ingestion rates that were observed. The seston treatments did not elicit significant growth rate responses for D. pulex and D. pulicaria, but significant responses to respiration rates were observed for all species. Consumer body stoichiometry, differences in seston C:P for each experiment, or differential assimilation by producer types may be driving these results. My study suggests that the stoichiometric knife edge documented in laboratory studies under low C:P conditions may not operate to the same degree when natural seston is the food source; diet diversity may be driving complex nuances for consumer performance that were previously overlooked. / Dissertation/Thesis / Masters Thesis Biology 2015

Made available in DSpace on 2014-06-11T19:30:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-25Bitstream added on 2014-06-13T20:39:53Z : No. of bitstreams: 1 silva_cv_me_botib.pdf: 1186795 bytes, checksum: 33ce3363a0d8502049345a0c4ff4a50a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste estudo foi analisar a composição taxonômica e a densidade de macroinvertebrados associados à macrófita Eichhornia azurea (Swartz) Kunth em seis lagoas laterais ao Rio Paranapanema em sua zona de desembocadura na Represa de Jurumirim – SP. As amostragens foram realizadas em março e agosto de 2009, supostamente meses de estações chuvosa e seca, respectivamente. Em cada uma das seis lagoas, foram selecionados três bancos distintos de E. azurea para coleta do material biológico (macrófita e fauna associada) e medida das variáveis limnológicas: profundidade, transparência, temperatura, pH, condutividade elétrica e concentrações de oxigênio dissolvido e material em suspensão. A amostragem de E. azurea foi realizada com um retângulo de 0,1976 m2, utilizando-se uma tesoura de jardinagem para retirada do material vegetal, que foi lavado em solução de formol e água para remoção dos macroinvertebrados associados. Entre os períodos estudados diferenças significativas (p<0,05) foram encontradas tanto para as variáveis limnológicas, quanto para a densidade de alguns dos taxa de macroinvertebrados. Na comparação das lagoas entre si em março e agosto, com relação as variáveis limnológicas e densidade dos taxa de macroinvertebrados (em níveis de grandes grupos), o Teste Tukey apontou mais diferenças significativas (p<0,05) para março, embora alguns dos taxa de macroinvertebrados associados à E. azurea não tenha apresentado diferença significativa entre as lagoas em nenhum dos períodos amostrados. De acordo com a análise de componentes principais, o pH e oxigênio dissolvido são as variáveis que melhor explicam a ordenação das lagoas nos períodos de estudo. Com relação à fauna associada, em ambos os períodos a classe Insecta foi a mais abundante (com destaque a família Chironomidae), seguida pelo filo Crustacea e pela classe Clitellata... / The aim of this study was to analyze the taxonomic composition and density of macroinvertebrates associated with macrophyte Eichhornia azurea (Swartz) Kunth in six lagoons to the river side Paranapanema in its mouth zone into the Jurumirim Reservoir - SP. Samples were held in March and August 2009, supposedly months of rainy and dry seasons, respectively. In each of the six lagoons three different stands of E. azurea were selected for collecting biological material (macrophytes and associated fauna) and measurement of limnological variables: depth, transparency, temperature, pH, electric conductivity and concentrations of dissolved oxygen and suspended solids. The sampling of E. azurea was performed with a rectangle of 0,1976 m2, gardening shears was used to remove the plant material, which was washed in a solution of formaldehyde and water to remove associated macroinvertebrates. Between the two periods significant differences (p <0,05) were found for both limnological variables, and for the density of some of the taxa macroinvertebrates. In comparison with each other lagoons in March and August, related limnological variables and density of taxa of macroinvertebrates (levels in large groups), the Tukey test showed more significant differences (p <0,05) in March, although some of taxa of macroinvertebrates associated with E. azurea has not presented significant difference between the lagoons in any period sampled. According to principal components analysis, pH and dissolved oxygen are the variables that best explain the ordering of lagoons during the study periods. With respect to the associated fauna, in both periods the class Insecta was the most abundant (especially the family Chironomidae), followed by phylum Crustacea and the class Clitellata. However, comparing the richness of taxa in the months of sampling, it appears that higher values were recorded in August period... (Complete abstract click electronic access below)