M.Sc. / The Olifants- and Luvuvhu rivers both flow through the Kruger National Park (KNP). The Olifants River (OR) is a major tributary of the Limpopo River with water quality being less than desirable due to high concentrations of pollutants as a result of the activities in the upper catchment. The crocodile population of the river declined from 1000 in 2008 to 347 in 2009 due to pansteatitis. Labeobarbus marequensis in the upper catchment also showed symptoms of the disease (Templehoff, 2010). This raised concern about the health of the fish in the OR, particularly in the section flowing through the KNP. The Luvuvhu River (LR) is also a tributary of the Limpopo River with main land uses in the catchment being agriculture, mining and communal lands. Of concern is the finding of DDT residues in water, sediment, and domestic and indigenous biota upstream of the sites sampled in this study (Barnhoorn et al., 2009) which raised concerns about the health of fish in the lower reaches of the river flowing through the KNP. Therefore, the aim of this study was to assess the health status of [9] selected fish species from the OR and LR in the KNP using a histology-based health assessment protocol (HBHA). The species selected for this study included Hydrocynus vittatus, Labeobarbus marequensis, Labeo cylindricus and Labeo rosae. The OR was sampled in September 2009 and May 2010 while the LR was sampled in November 2009 and April 2010. A necropsy was done to determine if there were any internal or external macroscopic alterations with any alterations noted on a score sheet. Blood was taken for haematocrit (Hct), leukocrit (Lct) and total plasma protein (TP) determination. As part of the HBHA, a necropsy-based health assessment index (HAI) was applied using a modified protocol of Adams et al. (1993) where the necropsy and blood parameters were used to calculate the mean and sum HAI for the different species sampled on each sampling trip. Biometric indices including the condition factor, hepatosomatic index, splenosomatic index and the gonadosomatic index were calculated. Age was determined using otoliths for tigerfish and scales for the other species. Samples of selected organs (liver, kidney, gill, testes or ovaries) were taken for histological analysis. Microscope slides were assessed qualitatively to identify any histological alterations present. These results were semi-quantitatively assessed according to the protocol of Van Dyk et al. (2009a) from which an organ index and fish index were calculated. The organ index is an indication of the number and severity of histological alterations in a particular organ of a selected species. The organ indices were classed according to the classes of Van Dyk et al. (2009a) with Class 1 (<10) being tissue with slight histological alterations; Class 2 (10-25) being tissue with moderate histological alterations. The fish index is a sum of all of the organ indices for any given fish sampled.

La dégradation de la qualité de l’eau de la Seine à Paris et dans sa banlieue depuis la deuxième moitié du XIXe siècle a fait l’objet de plusieurs études. Rares sont les études qui confrontent les perceptions de médecins, d’ingénieurs, d’hygiénistes ou d’administrateurs sur la qualité des eaux des rivières et l’évolution de leur état. Cette confrontation permet d’analyser sur la longue durée l’efficacité des réponses apportées pour améliorer la qualité, ce que nous avons réalisé ici pour la ville de Versailles et ses eaux. La première partie du mémoire décrit les perceptions de la qualité des eaux des rivières par des experts entre 1854 et 1964 sur la base de l’analyse de revues d’hygiène et d’assainissement urbain, montrant l’évolution des indicateurs de qualité et de la réglementation. Versailles a pour particularité d’être, au XIXe siècle, essentiellement alimentée par de l’eau de Seine grâce à la machine de Marly, par le biais d’un Service dépendant directement de l’Etat, conséquences de son passé royal. Mais la qualité de l’eau du fleuve se dégradant à cause des rejets des égouts de Paris, les différentes administrations, locales et nationales, doivent résoudre la question d’approvisionnement en eau alimentaire et recourent à l’aide d’experts pour s’assurer de sa qualité. Les analyses chimiques et bactériologiques effectuées sur les eaux conduisent à l’abandon de l’eau de la Seine en 1894 au profit des eaux de la nappe de Marly-Croissy. En même temps, Versailles rejetait ses eaux usées dans des cours d’eau à faible débit : le ru de Marivel et le ru de Gally. Epidémies et plaintes accompagnent la dégradation de leur état. Les nombreuses expertises menées témoignent de l’intérêt pour la qualité des eaux de surface et en même temps de l’absence de la volonté politique et des limites techniques pour l’améliorer, conduisant à leur sacrifice pendant plus de 100 ans. / The Seine River pollution both in Paris and its suburbs has been already the subject of several studies. Few studies compare perceptions that physicians, engineers, hygienists or managers might have of the quality of water resources, and the evolution of their state. This confrontation makes it possible to analyze over the long term the effectiveness of the responses made to improve quality. We have achieved this here for the city of Versailles and its waters. The first part of this work describes perceptions of river water quality by experts between 1854 and 1964 based on an analysis of hygiene and urban sanitation reviews, showing the evolution of quality indicators and of regulations. In the 19th century, Versailles has the peculiarity of being essentially fed by water from the Seine thanks to the Marly machine, through a service directly dependent on the State, consequences of its royal past. But as the water quality of the Seine River deteriorates because of the discharges from the Paris sewers, the various administrations, local and national, have to solve the question of water supply and asked for the help of experts to ensure its quality. The chemical and bacteriological analyzes carried out on waters lead to stopping the use of the Seine waters in 1894 in favor of the Marly-Croissy water table. At the same time, Versailles rejected its wastewater into two low-flowing streams: Marivel and Gally. Epidemics and complaints accompany the deterioration of their state. The numerous experiments carried out show the interest in the quality of surface water and at the same time the absence of the political will and the technical limits to improve it, leading to their sacrifice for more than 100 years.

The west coast of Taiwan is densely populated with frequently activities for industrial and economic developments. The area is also the site with the existence of Chinese White Dolphin (CWD). Because the arising of ecosystem conservation, the government has attempted to promote the west coast as the marine protected areas (MPAs) for the CWD. Nevertheless, it is required to assess changes of environmental condition and marine environmental quality around the area before the establishment of marine protected areas to the site. If ineffective monitoring is implemented, then the establishment of marine protected areas will be no use. This study was initiated to assess the marine environmental condition by collecting and surveying the long term monitoring data that were published under the government reports and documents to assess the temporal and spatial trends of environmental factors. The data consists of rivers, trench, and marine water or sediments. The study areas covered Taichung County to Yunlin County. The methods for assessing the environmental quality included the use of geographic information system (GIS) for the biological distribution, regression analysis for the trend monitoring of chemical contaminants and physical environmental factors between 2001 ¡V 2010 year surveys. The overall environmental quality within the studied sites were further evaluated for the river pollution index (RPI) and the habitat suitability index (HSI). The survey results of 10 years river monitoring from Taichung to Yunlin showed that Hsin-Huu-Wei River belong to serious pollution with RPI 6.67 value. Yuanlin drainage, one of the six drainages of Chang Hua Coast Industrial Park, belongs to serious pollution with RPI 6.08 value. The RPI results of Six trenches around the Chang-Hua Coast Industrial Park showed that Tien-Wei trench 2, Lun-Wei trench 1, and Ji-An trench belong to mid level of pollution (RPI 3.7~3.975). In the marine water survey, the results showed that the pH values were found lower at southern-ward monitoring station nearby the Formosa Petrochemical Corporation No. 6 Naphtha Cracking Industry site. The nitrogen-NH3 concentrations were found high in Jhuo-Shuei River and No. 6 Naphtha Cracking industry. The concentration of Chlorophyll-a was high in Chang-Hua Coast Industrial Park. In the survey of sediment, Hsin-Huu-Wei River arsenic concentration (As) was over the EPA guidelines, but the concentrations of Cr, Cu, Pb, Zn were within the level of required limits. In the biological survey, the results showed that abundance and species were not evenly distributed with non-comprehensive trends related to the environmental condition or changes. These indicated that biological monitoring survey displayed less important than physical and chemical monitoring for the assessment of man-made pollution or environmental impact from the industrial activities. Overall the monitor sites of river, drainage and trench were differed without a consistent sampling scheme. The offshore sites were sampled greatly in distance, i.e. the farthermost point at four sea miles that had caused difficulties for the comparison of data results collected in different time. It is very uneasy to evaluate the pollution monitoring results. Thus, it is required to develop a long-term environmental quality monitoring plan for the assessment of water quality and sediment of river and marine water with appropriate / consistency sampling method, monitor time and site scheme. Finally, the relevant authorities should implement river remediation to improve the pollution and thereby to maintain the sustainability of marine environment. It is required to establish an integral monitoring program consisting of water and sediment and bio-monitoring in rivers, estuary, and marine to better predict the marine environmental quality. Also the integral and long-term monitoring program should ensure to predict the changes of west coastal and to achieve the effectiveness of marine environment.

The west coast of Taiwan is enriched with biological resources. The areas are the economic development sites with highly industrialized activities and densely population. The government attempts to promote the sites for the establishment of marine protected areas (MPA) because of the existence of Chinese White Dolphin (Sousa Chinensis) which is the most important issues against the sustainable development of economy. Thus, the present study was initiated to assess the marine environmental quality (MEQ) in the west coast of Taiwan. The research consists of the integral monitoring assessments of rivers, estuaries and the marine areas. This work collected, reviewed and analyzed the environmental monitoring data from industrial environmental impact assessment reports and governmental documents for the evaluation of spatial and temporal trends of the west coast areas over the last ten year. The assessment is required to understand the possible interactive problems between the marine protected areas and the marine environmental quality prior to the establishment of MPA acts. The present work consists of the subsection of coastal areas ranging from Hsinchu Country to Taichung Harbour. Ten annual monitoring data including the water quality or sediments of rivers, estuaries, and marine were assessed for the spatial and temporal trends of physical, chemical and biological changes over the years. The approaches for assessing the sites included the geographic information system (GIS) spatial analysis method and linear regression of monitoring data. The levels of pollution were also evaluated by using the river pollution index (RPI). The effect of habitat suitability index (HSI) was also calculated. The results of river water quality assessment showed that the Ke-ya-si, Jhong-gang river, and Nan-gan river were seriously polluted with RPI¡Ö6. The river seiment contaminants (Cu¡BNi) were significantly increased in the Ke-ya-si and Jhong-gang river. The water quality of Taichung Port drainage showed serious pollution with low dissolved oxygen (DO), high concentrations of ammonia nitrogen, and high counts of coli-forms. The Taichung Port drainage sediment contaminants (As¡BCu¡BHg¡BZn) had higher than the average of EPA guidelines. This could be resulting from the significant point source of industries pollutants discharged into the river. The significant amounts of waste water discharged into ocean could cause the impacts to the marine environment. The present study demonstrated the impacts to the river monitoring site although the ocean water quality monitoring contaminants were found without signicant changes in all time. This suggests that the ocean water quality monitoring sites were inconsistently sampled at 4 nm away from the coast which caused the dilution of contaminant concentrations and affecting the monitoring effectiveness. The sediment contaminants in Taichung Port monitoring site showed with the exception of appearing unusual change. The results also showed that there is lack of bio-monitoring program carried out in rivers, estuary, and marine that are imperatively needed to resolve the ineffective sampling protocol implemented in the current coastal environmental monitoring. This is owing to the non unified for authorization between the municipality and environmental bureau. The Canada Ocean Acts on assessing the water and sediment and bio-monitoring in rivers, estuary, and marine as a whole concept were compared with the present study. Finally, the relevant authorities should implement river remediation to improve the pollution and thereby to maintain the sustainability of marine environment. It is needed to establish an integral monitoring program consisting of water and sediment and bio-monitoring in rivers, estuary, and marine to better predict the marine environmental quality. Also the integral and long-term monitoring program should ensure to predict the changes of west coastal and to achieve the effectiveness of marine management.

A sub-bacia hidrográfica do rio Corumbataí é de grande importância sócioeconômica no estado de São Paulo, cujo rio, de mesmo nome, tornou-se alvo de preocupação ainda maior nos últimos anos, quando passou a atender 100% do abastecimento do município de Piracicaba. Sendo explorada principalmente pela cultura da cana-de-açúcar e composta de solos com características físico-químicas distintas e relevo variando de plano a montanhoso, surge grande preocupação em torno do comportamento ambiental dos agrotóxicos empregados nesta bacia, o qual é desconhecido até o momento. O presente estudo teve por objetivo avaliar a biogeodinâmica dos agrotóxicos empregados em cana-de-açúcar nesta bacia hidrográfica, vindo a servir de subsídio aos processos de avaliação da qualidade da água desta bacia e definição de metas para o Plano de Bacias, elaborado pelo Comitê das Bacias dos Rios Piracicaba, Capivari e Jundiaí. Este trabalho consistiu de caracterização temporal do uso de agrotóxicos em cana-de-açúcar, o qual serviu de suporte na definição de moléculas e períodos de amostragem para o monitoramento de resíduos em água e sedimento na calha principal do rio Corumbataí e principais afluentes. A identificação de áreas críticas na sub-bacia para o aporte de agrotóxicos foi realizada por meio do modelo matemático SWAT. O estudo apontou o uso principalmente de herbicidas, sendo os únicos produtos de uso declarado no período de avaliação, com consumo sazonal de algumas moléculas e uso indistinto de outras ao longo do ano, o que permitiu um planejamento estratégico do monitoramento de resíduos. Os herbicidas glifosato, atrazina, ametrina, 2,4-D, metribuzim, diurom e acetocloro representaram aproximadamente 85% do volume total de produtos consumidos entre 2000 e 2003. Imazapir foi identificado como o herbicida de maior freqüência de uso, sendo também vislumbrado o emprego de moléculas de alta toxicidade e mobilidade, como sulfentrazona, trifloxissulfurom-sódico, paraquate, tebutiurom e imazapique. No monitoramento de resíduos, níveis quantificáveis de ametrina, atrazina, simazina, hexazinona, glifosato e clomazona foram detectados em amostras de água, com níveis desprezíveis de ametrina e glifosato em sedimento. A área de recarga do aqüífero Guarani, no norte da bacia, apresentou os níveis mais elevados de triazinas e clomazona. As triazinas representam o grupo de moléculas detectadas em níveis mais altos, com a atrazina superando os padrões de potabilidade e de qualidade de água para a vida aquática em alguns pontos. Estas moléculas foram também apontadas pela simulação, como as de maior tendência de ocorrer nos corpos hídricos superficiais e subterrâneos, quando aplicadas em período chuvoso, sendo superadas por glifosato em corpos hídricos superficiais, quando a aplicação ocorreu em período de seca. A simulação de um cenário de expansão da cultura de cana-de-açúcar resultou em aumento da participação das áreas com Areia Quartzosa para o aporte de herbicidas aos corpos hídricos, que juntamente com o Podzólico Vermelho-Amarelo, Podzólico Vermelho-Escuro e solos Litólicos, apresentaram maior vulnerabilidade na bacia. As regiões norte da bacia e as sub-bacias do Ribeirão Claro e rio Passa Cinco evidenciaram as maiores exportações de herbicidas aos corpos hídricos e níveis de resíduos em segmentos de rio após o período de chuva intensa. / The Corumbataí river watershed is of great socioeconomic importance in the state of São Paulo, which river, of the same name, became target of higher concern in the last years, when it started to assist 100% the provisioning of the municipal district of Piracicaba. Being explored mainly by the culture of sugarcane and composed of soils with different physicochemical characteristics and relief varying from plan to mountainous, great concern appears around the environmental behavior of pesticides employed in this basin, whose dynamics is ignored until then. The present study had for objective to evaluate the biogeodynamic of pesticides employed in sugarcane in this watershed, coming to serve from subsidy to the water quality evaluation processes of this basin and definition of goals for the Plan of Basins elaborated by the Watersheds Committee of Piracicaba, Capivari, and Jundiaí Rivers. This work consisted of temporal characterization of the use of pesticides on sugarcane, which served as support in the definition of molecules and sampling periods for the residue monitoring in water and sediment in the main channel of the Corumbataí river and main affluents. The identification of critical areas in the sub-basin for the contribution of pesticides was accomplished through the mathematical model SWAT. The study pointed the use mainly of herbicides, being the only one, whose use was declared in the evaluation period, with seasonal consumption of some molecules and use of others along the whole year, what allowed a residue monitoring strategic planning. The herbicides glyphosate, atrazine, ametryne, 2,4-D, metribuzin, diuron and acetochlor represented around 85% of the total volume of products consumed between 2000 and 2003. Imazapyr was identified as the herbicide of larger use frequency, being also observed the use of high toxicity and mobility molecules, as sulfentrazone, trifloxysulfuron-sodium, paraquat, tebuthiuron and imazapic. In the residue monitoring, quantifiable levels of ametryne, atrazine, simazine, hexazinone, glyphosate and clomazone were detected in water samples, with negligible levels of ametryne and glyphosate in sediment. The recharge area of the Guarani aquifer, in the north of the basin, presented the highest levels of triazines and clomazone. The triazines represent the group of molecules detected in higher levels, with the atrazine overcoming the water potability and quality standards for the aquatic life in some points. These molecules were pointed also for the simulation, as the one of larger tendency of happening in the surface waters and groundwaters, when applied in raining periods, being overcome by glyphosate in surface water bodies, when the application happened in dry period. The simulation of a sugarcane culture expansion scenery resulted in increase of the participation of the areas with Typic Quartzipsamment (Areia Quartzosa) for the herbicides contribution to the water bodies, which added with Typic Hapludult (Podzólico Vermelho-Amarelo), Rhodic Kandiudox (Podzólico Vermelho-Escuro) and Typic Udorthent (Litólico) soils, presented larger vulnerability in the basin. The north region of the Corumbataí river watershed and the sub-basins of Ribeirão Claro and Passa Cinco river showed the largest herbicide loadings to water bodies and levels of residues in river segments after the period of intense rain.

A sub-bacia hidrográfica do rio Corumbataí é de grande importância sócioeconômica no estado de São Paulo, cujo rio, de mesmo nome, tornou-se alvo de preocupação ainda maior nos últimos anos, quando passou a atender 100% do abastecimento do município de Piracicaba. Sendo explorada principalmente pela cultura da cana-de-açúcar e composta de solos com características físico-químicas distintas e relevo variando de plano a montanhoso, surge grande preocupação em torno do comportamento ambiental dos agrotóxicos empregados nesta bacia, o qual é desconhecido até o momento. O presente estudo teve por objetivo avaliar a biogeodinâmica dos agrotóxicos empregados em cana-de-açúcar nesta bacia hidrográfica, vindo a servir de subsídio aos processos de avaliação da qualidade da água desta bacia e definição de metas para o Plano de Bacias, elaborado pelo Comitê das Bacias dos Rios Piracicaba, Capivari e Jundiaí. Este trabalho consistiu de caracterização temporal do uso de agrotóxicos em cana-de-açúcar, o qual serviu de suporte na definição de moléculas e períodos de amostragem para o monitoramento de resíduos em água e sedimento na calha principal do rio Corumbataí e principais afluentes. A identificação de áreas críticas na sub-bacia para o aporte de agrotóxicos foi realizada por meio do modelo matemático SWAT. O estudo apontou o uso principalmente de herbicidas, sendo os únicos produtos de uso declarado no período de avaliação, com consumo sazonal de algumas moléculas e uso indistinto de outras ao longo do ano, o que permitiu um planejamento estratégico do monitoramento de resíduos. Os herbicidas glifosato, atrazina, ametrina, 2,4-D, metribuzim, diurom e acetocloro representaram aproximadamente 85% do volume total de produtos consumidos entre 2000 e 2003. Imazapir foi identificado como o herbicida de maior freqüência de uso, sendo também vislumbrado o emprego de moléculas de alta toxicidade e mobilidade, como sulfentrazona, trifloxissulfurom-sódico, paraquate, tebutiurom e imazapique. No monitoramento de resíduos, níveis quantificáveis de ametrina, atrazina, simazina, hexazinona, glifosato e clomazona foram detectados em amostras de água, com níveis desprezíveis de ametrina e glifosato em sedimento. A área de recarga do aqüífero Guarani, no norte da bacia, apresentou os níveis mais elevados de triazinas e clomazona. As triazinas representam o grupo de moléculas detectadas em níveis mais altos, com a atrazina superando os padrões de potabilidade e de qualidade de água para a vida aquática em alguns pontos. Estas moléculas foram também apontadas pela simulação, como as de maior tendência de ocorrer nos corpos hídricos superficiais e subterrâneos, quando aplicadas em período chuvoso, sendo superadas por glifosato em corpos hídricos superficiais, quando a aplicação ocorreu em período de seca. A simulação de um cenário de expansão da cultura de cana-de-açúcar resultou em aumento da participação das áreas com Areia Quartzosa para o aporte de herbicidas aos corpos hídricos, que juntamente com o Podzólico Vermelho-Amarelo, Podzólico Vermelho-Escuro e solos Litólicos, apresentaram maior vulnerabilidade na bacia. As regiões norte da bacia e as sub-bacias do Ribeirão Claro e rio Passa Cinco evidenciaram as maiores exportações de herbicidas aos corpos hídricos e níveis de resíduos em segmentos de rio após o período de chuva intensa. / The Corumbataí river watershed is of great socioeconomic importance in the state of São Paulo, which river, of the same name, became target of higher concern in the last years, when it started to assist 100% the provisioning of the municipal district of Piracicaba. Being explored mainly by the culture of sugarcane and composed of soils with different physicochemical characteristics and relief varying from plan to mountainous, great concern appears around the environmental behavior of pesticides employed in this basin, whose dynamics is ignored until then. The present study had for objective to evaluate the biogeodynamic of pesticides employed in sugarcane in this watershed, coming to serve from subsidy to the water quality evaluation processes of this basin and definition of goals for the Plan of Basins elaborated by the Watersheds Committee of Piracicaba, Capivari, and Jundiaí Rivers. This work consisted of temporal characterization of the use of pesticides on sugarcane, which served as support in the definition of molecules and sampling periods for the residue monitoring in water and sediment in the main channel of the Corumbataí river and main affluents. The identification of critical areas in the sub-basin for the contribution of pesticides was accomplished through the mathematical model SWAT. The study pointed the use mainly of herbicides, being the only one, whose use was declared in the evaluation period, with seasonal consumption of some molecules and use of others along the whole year, what allowed a residue monitoring strategic planning. The herbicides glyphosate, atrazine, ametryne, 2,4-D, metribuzin, diuron and acetochlor represented around 85% of the total volume of products consumed between 2000 and 2003. Imazapyr was identified as the herbicide of larger use frequency, being also observed the use of high toxicity and mobility molecules, as sulfentrazone, trifloxysulfuron-sodium, paraquat, tebuthiuron and imazapic. In the residue monitoring, quantifiable levels of ametryne, atrazine, simazine, hexazinone, glyphosate and clomazone were detected in water samples, with negligible levels of ametryne and glyphosate in sediment. The recharge area of the Guarani aquifer, in the north of the basin, presented the highest levels of triazines and clomazone. The triazines represent the group of molecules detected in higher levels, with the atrazine overcoming the water potability and quality standards for the aquatic life in some points. These molecules were pointed also for the simulation, as the one of larger tendency of happening in the surface waters and groundwaters, when applied in raining periods, being overcome by glyphosate in surface water bodies, when the application happened in dry period. The simulation of a sugarcane culture expansion scenery resulted in increase of the participation of the areas with Typic Quartzipsamment (Areia Quartzosa) for the herbicides contribution to the water bodies, which added with Typic Hapludult (Podzólico Vermelho-Amarelo), Rhodic Kandiudox (Podzólico Vermelho-Escuro) and Typic Udorthent (Litólico) soils, presented larger vulnerability in the basin. The north region of the Corumbataí river watershed and the sub-basins of Ribeirão Claro and Passa Cinco river showed the largest herbicide loadings to water bodies and levels of residues in river segments after the period of intense rain.

Magister Educationis - MEd / The research reported in this paper involves the use of dialogical argumentation in scientific context with 7-9 year olds as part of teaching and learning in primary classrooms. To develop an understanding of scientific concepts, four suitable collaborative activities on river pollution were used as a stimulus to effectively engage learners in scientific reasoning and use evidence for decision-making through cognitive harmonization. The research, involved four groups of five children each. Data were collected through analysis of children’s Water Pollution Questionnaire (WPQ), classroom observation, documentation of field notes, conversations and focus group interviews. The study found that all groups were able to engage in the activities to some extent, but that good quality argumentation develops when children are familiar with working in this manner. This study sought to investigate the opportunities, possibilities and challenges associated with a dialogical argumentation teaching and learning approach in a primary school science class A mapping technique was used to analyze the children’s discussions and identify the quality of their different “levels” of argument. This study confirmed that an argumentation based instruction was an effective way of enhancing learners’ understanding of river pollution. The learners’ listening skills improved tremendously and they were actively involve during discussions and provided claims with valid grounds or reasons. They were also very enthusiastic and challenged each other’s claims during these argumentation lessons, but most of all was the enjoyment that was visible on their young faces. Further research needs to be carried out over a longer period to determine the effectiveness of an argumentation based instruction. / South Africa

Streams and rivers are examples of vital ecosystems that frequently undergo various environmental and anthropogenic stresses. A core question in population ecology is whether a given population will persist under changing ecological conditions. This thesis consists of three papers and is devoted to the mathematical analysis of responses of river-dwelling species to population persistence threats. The first paper presents a stochastic approach to the 'drift paradox' problem, where the classical reaction-advection-diffusion model is replaced by a birth-death-emigration process. We explore the effects of temporally varying flow on the persistence probability and highlight the importance of the benthic stage for the persistence of stream organisms. The second paper addresses the problem of river network fragmentation through disconnecting structures such as dams. We construct a population matrix model that incorporates the spatial structure of the studied river network and compare structural connectivity to an indicator of population persistence. The third paper adapts the same basic matrix model to examine fish response to disturbances travelling downstream from upstream sites. The study of these three aspects of persistence challenges for river populations contributes to the cumulative effects assessment on river networks.

No description available.