The diversity of microorganisms and the influence of their enzymatic activities in soil are critical to the maintenance of good soil health. Changes in these parameters may be the earliest predictors of soil quality changes, potentially indicating anthropogenic influences. The goal of this study was to investigate the soil microbial diversity and function of grasslands along an urbanization gradient. Soil samples were collected in the Potchefstroom municipal area, South Africa, at specific sites. Sampling sites were described as urban, suburban and rural - according to the V-I-S (Vegetation-Impervious surface-Soil) model of Ridd (1995). Soil samples were collected over a warmer, wet season (May) and a colder, dry season (August) over two years (2007 and 2008). Collected soil samples were characterised using certain physical and chemical parameters. Plant species composition and abundance were determined at each site, along with basic site data (soil compaction, percentage ground cover, percentage bare ground, percentage organic material present). The Shannon-Weaver diversity index was used to calculate biodiversity values for all the investigated sites regarding collected plant species composition. The microbial component of the soil was quantified and characterized using culture-dependent and culture-independent techniques. Culture-dependent techniques included the investigation of the aerobic heterotrophic bacteria and fungi. Organisms were plated out on different media, and the bacterial component was broadly grouped using morphology. Dominant organisms were identified by sequencing of PCR amplified 16S ribosomal DNA fragments. Shannon-Weaver index for bacterial diversity was determined for each of the sites. Denaturing gradient gel electrophoresis (DGGE) profiling of selected bacterial communities were also conducted. Microbial community function was determined using enzyme assays of five major groups of enzymes, namely (i) dehydrogenase; (ii) β-glucosidase; (iii) acid phosphatase, (iv) alkaline phosphatase and (v) urease. Plant species results were then brought into context with microbiological diversity and functionality results using multivariate statistics. Physical and chemical parameters of the collected soil samples revealed patterns present along the urbanization gradient. The pH values were mostly higher in the sub-urban and urban sites than in the rural sites. Electrical conductivity values were generally highest in the sub-urban sites. Plant species composition revealed trends along the urbanization gradient. Ordinations clearly grouped the plant species into rural, sub-urban and urban groups regarding plant species composition. Rural sites had the highest number of plant species. Shannon-Weaver values regarding the plant diversity supported the plant species composition data indicating higher plant diversity in the rural areas, followed by the sub-urban and the urban areas. Plant structural data indicated that forbs were most numerous in the rural sites, and less so in the urban sites. Higher average aerobic heterotrophic bacterial levels were present in the urban soil samples. The bacterial levels were lower in the sub-urban and rural soil samples. Subsequent identification of the dominant bacteria in the soil samples revealed organisms of the genus Bacillus dominated the aerobic heterotrophic bacterial communities in the soil samples. Bacillus species dominated the soil samples along the urbanization gradient. Shannon-Weaver indices based on culture-dependent methods indicated that urban sites had the highest biodiversity. These results could have been exaggerated, because of an overestimation of the number of bacterial morphotypes present in samples. Fungal levels were higher in the soil from samples collected at the rural samples sites. The culture-independent method (DGGE) was not optimized and inconclusive results were obtained. Enzyme assays revealed that potential dehydrogenase, β-glucosidase and urease activity followed a trend along the urbanization gradient, with urban samples registering the highest values and rural sites the lowest. Enzymes involved in carbohydrate catabolism (β-glucosidase and dehydrogenase) registered significantly higher potential activity in urban sites than the sub-urban and rural sites. The results could indicate that urban sites have the potential to lose carbon at higher rates than the rural sites. This aspect may need further investigation. Higher potential urease activity could indicate higher N-cycling in the urban soil environment. Ordination results for soil-, plant- and microbial diversity as well as microbial functionality indicated certain trends along the urbanization gradient. Plant species composition and structure data indicated that urbanization has a definite effect on the plant communities in the urban ecosystem. Results regarding aerobic heterotrophic bacteria populations and potential enzyme activity of the dehydrogenase, β-glucosidase (both active in the carbon cycle) and urease (active in the nitrogen cycle) illustrated clear trends along the urbanization gradient. In conclusion, results indicated that urbanization has an effect on plant species composition, and the population and function of aerobic heterotrophic bacteria and the fungal population. Furthermore, this study demonstrated the potential of using microbial diversity and activity as tools to investigate carbon utilization and storage along an urban-rural gradient. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2011

Increasing socio-economic growth and development of South Africa’s freshwater systems require continuous augmentation of water sources to meet the growing water requirements of communities and industries. Anthropogenic disturbances have caused the water quality of many freshwater systems to drastically deteriorate due to constant disposal of domestic, industrial, and agricultural waste into surface waters. Government agencies make use of biomonitoring programmes to effectively manage the countries’ freshwater resources. These programmes use a variety of biological indicators (e.g., macroinvertebrates, fish, diatoms and algal species) and physico-chemical variables to determine the state of the environment. However, attempts to use microbial community structures as bioindicators of anthropogenic perturbations are greatly neglected. This study used molecular techniques (PCR-DGGE and 454-pyrosequencing) and multivariate analysis to develop a robust monitoring technique to determine the impacts of environmental disturbances on bacterial community compositions in river systems in the North West Province. Significant contributions made by this project included the establishment of a bacterial diversity framework for South African freshwater systems that are impacted by a variety of anthropogenic activities (e.g., urban and informal settlements, agriculture and mining). Furthermore, case studies demonstrated the prevalence of specific taxa at polluted sites, as well as positive and negative associations between taxa and environmental variables and pollutants. Finally, biogeochemical cycles could be partially matched to bacterial community structures in river systems. The first part of the project included a pilot study that investigated bacterial structures in a segment of the Vaal River in response to environmental parameters using molecular techniques and multivariate analysis. The most important observations made during this study included the generation of a larger bacterial diversity dataset by pyrosequencing compared to PCR-DGGE. In addition, metagenomic and multivariate analyses provided clues about potential biogeochemical roles of different taxa. The second and third part of the project included two case studies that investigated bacterial communities in the Mooi River and Wonderfonteinspruit in response to environmental activities. Both these systems are impacted by a variety of external sources such as urban and informal settlements, agriculture, and mining. The results demonstrated that perturbations nearby the Mooi River and Wonderfonteinspruit caused the overall water quality to deteriorate which in turn had a profound impact on bacterial community composition. Bacterial community structures at reference/control sites (Muiskraal and Turffontein dolomitic eye) had overall high species diversity (richness and evenness), whereas polluted sites showed lower species diversity and were dominated by the Beta- and Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia. In addition, various potential pathogens (e.g. Eschirichia/Shigella, Legionella, Staphylococcus, Streptococcus etc.) were identified at impacted sites. Multivariate analysis suggested that bacterial communities and certain taxa (Malikia, Algoriphagus, Rhodobacter, Brevundimonas and Sphingopyxis) at polluted sites were mainly impacted by temperature, pH, nutrient levels, and heavy metals. Finally, the proportion of nitrogen and sulphur bacteria corresponded well with the nitrogen and sulphur levels measured in the Wonderfonteinspruit. Based on these results, it was concluded that bacterial community structures might provide a good indicator of anthropogenic disturbances in freshwater systems and may be incorporated into biomonitoring programs. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The diversity of microorganisms and the influence of their enzymatic activities in soil are critical to the maintenance of good soil health. Changes in these parameters may be the earliest predictors of soil quality changes, potentially indicating anthropogenic influences. The goal of this study was to investigate the soil microbial diversity and function of grasslands along an urbanization gradient. Soil samples were collected in the Potchefstroom municipal area, South Africa, at specific sites. Sampling sites were described as urban, suburban and rural - according to the V-I-S (Vegetation-Impervious surface-Soil) model of Ridd (1995). Soil samples were collected over a warmer, wet season (May) and a colder, dry season (August) over two years (2007 and 2008). Collected soil samples were characterised using certain physical and chemical parameters. Plant species composition and abundance were determined at each site, along with basic site data (soil compaction, percentage ground cover, percentage bare ground, percentage organic material present). The Shannon-Weaver diversity index was used to calculate biodiversity values for all the investigated sites regarding collected plant species composition. The microbial component of the soil was quantified and characterized using culture-dependent and culture-independent techniques. Culture-dependent techniques included the investigation of the aerobic heterotrophic bacteria and fungi. Organisms were plated out on different media, and the bacterial component was broadly grouped using morphology. Dominant organisms were identified by sequencing of PCR amplified 16S ribosomal DNA fragments. Shannon-Weaver index for bacterial diversity was determined for each of the sites. Denaturing gradient gel electrophoresis (DGGE) profiling of selected bacterial communities were also conducted. Microbial community function was determined using enzyme assays of five major groups of enzymes, namely (i) dehydrogenase; (ii) β-glucosidase; (iii) acid phosphatase, (iv) alkaline phosphatase and (v) urease. Plant species results were then brought into context with microbiological diversity and functionality results using multivariate statistics. Physical and chemical parameters of the collected soil samples revealed patterns present along the urbanization gradient. The pH values were mostly higher in the sub-urban and urban sites than in the rural sites. Electrical conductivity values were generally highest in the sub-urban sites. Plant species composition revealed trends along the urbanization gradient. Ordinations clearly grouped the plant species into rural, sub-urban and urban groups regarding plant species composition. Rural sites had the highest number of plant species. Shannon-Weaver values regarding the plant diversity supported the plant species composition data indicating higher plant diversity in the rural areas, followed by the sub-urban and the urban areas. Plant structural data indicated that forbs were most numerous in the rural sites, and less so in the urban sites. Higher average aerobic heterotrophic bacterial levels were present in the urban soil samples. The bacterial levels were lower in the sub-urban and rural soil samples. Subsequent identification of the dominant bacteria in the soil samples revealed organisms of the genus Bacillus dominated the aerobic heterotrophic bacterial communities in the soil samples. Bacillus species dominated the soil samples along the urbanization gradient. Shannon-Weaver indices based on culture-dependent methods indicated that urban sites had the highest biodiversity. These results could have been exaggerated, because of an overestimation of the number of bacterial morphotypes present in samples. Fungal levels were higher in the soil from samples collected at the rural samples sites. The culture-independent method (DGGE) was not optimized and inconclusive results were obtained. Enzyme assays revealed that potential dehydrogenase, β-glucosidase and urease activity followed a trend along the urbanization gradient, with urban samples registering the highest values and rural sites the lowest. Enzymes involved in carbohydrate catabolism (β-glucosidase and dehydrogenase) registered significantly higher potential activity in urban sites than the sub-urban and rural sites. The results could indicate that urban sites have the potential to lose carbon at higher rates than the rural sites. This aspect may need further investigation. Higher potential urease activity could indicate higher N-cycling in the urban soil environment. Ordination results for soil-, plant- and microbial diversity as well as microbial functionality indicated certain trends along the urbanization gradient. Plant species composition and structure data indicated that urbanization has a definite effect on the plant communities in the urban ecosystem. Results regarding aerobic heterotrophic bacteria populations and potential enzyme activity of the dehydrogenase, β-glucosidase (both active in the carbon cycle) and urease (active in the nitrogen cycle) illustrated clear trends along the urbanization gradient. In conclusion, results indicated that urbanization has an effect on plant species composition, and the population and function of aerobic heterotrophic bacteria and the fungal population. Furthermore, this study demonstrated the potential of using microbial diversity and activity as tools to investigate carbon utilization and storage along an urban-rural gradient. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2011

Increasing socio-economic growth and development of South Africa’s freshwater systems require continuous augmentation of water sources to meet the growing water requirements of communities and industries. Anthropogenic disturbances have caused the water quality of many freshwater systems to drastically deteriorate due to constant disposal of domestic, industrial, and agricultural waste into surface waters. Government agencies make use of biomonitoring programmes to effectively manage the countries’ freshwater resources. These programmes use a variety of biological indicators (e.g., macroinvertebrates, fish, diatoms and algal species) and physico-chemical variables to determine the state of the environment. However, attempts to use microbial community structures as bioindicators of anthropogenic perturbations are greatly neglected. This study used molecular techniques (PCR-DGGE and 454-pyrosequencing) and multivariate analysis to develop a robust monitoring technique to determine the impacts of environmental disturbances on bacterial community compositions in river systems in the North West Province. Significant contributions made by this project included the establishment of a bacterial diversity framework for South African freshwater systems that are impacted by a variety of anthropogenic activities (e.g., urban and informal settlements, agriculture and mining). Furthermore, case studies demonstrated the prevalence of specific taxa at polluted sites, as well as positive and negative associations between taxa and environmental variables and pollutants. Finally, biogeochemical cycles could be partially matched to bacterial community structures in river systems. The first part of the project included a pilot study that investigated bacterial structures in a segment of the Vaal River in response to environmental parameters using molecular techniques and multivariate analysis. The most important observations made during this study included the generation of a larger bacterial diversity dataset by pyrosequencing compared to PCR-DGGE. In addition, metagenomic and multivariate analyses provided clues about potential biogeochemical roles of different taxa. The second and third part of the project included two case studies that investigated bacterial communities in the Mooi River and Wonderfonteinspruit in response to environmental activities. Both these systems are impacted by a variety of external sources such as urban and informal settlements, agriculture, and mining. The results demonstrated that perturbations nearby the Mooi River and Wonderfonteinspruit caused the overall water quality to deteriorate which in turn had a profound impact on bacterial community composition. Bacterial community structures at reference/control sites (Muiskraal and Turffontein dolomitic eye) had overall high species diversity (richness and evenness), whereas polluted sites showed lower species diversity and were dominated by the Beta- and Gammaproteobacteria, Bacteroidetes, and Verrucomicrobia. In addition, various potential pathogens (e.g. Eschirichia/Shigella, Legionella, Staphylococcus, Streptococcus etc.) were identified at impacted sites. Multivariate analysis suggested that bacterial communities and certain taxa (Malikia, Algoriphagus, Rhodobacter, Brevundimonas and Sphingopyxis) at polluted sites were mainly impacted by temperature, pH, nutrient levels, and heavy metals. Finally, the proportion of nitrogen and sulphur bacteria corresponded well with the nitrogen and sulphur levels measured in the Wonderfonteinspruit. Based on these results, it was concluded that bacterial community structures might provide a good indicator of anthropogenic disturbances in freshwater systems and may be incorporated into biomonitoring programs. / PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Climate warming has the potential to alter the structure and function of Arctic ecosystems in ways that are not fully understood. Polygonal terrain is a widespread permafrost feature of Arctic landscapes that is likely to be impacted by warming ground temperatures. This is of particular relevance in the uplands in the Mackenzie Delta region, where high-centre ice wedge polygon fields comprise 10% of the terrestrial landscape, and mean annual ground temperatures have increased between 1 and 2°C over the last 40 years (Burn and Kokelj 2009). I used broad-scale airphoto analysis and fine-scale field studies to investigate the impacts and possible trajectories of ice wedge degradation in the upland tundra north of Inuvik, NWT. Field investigations were undertaken to characterize biotic and abiotic conditions and feedbacks in stable and degrading high-centre polygons. Field surveys were conducted along transects which crossed three polygon micropositions (centres, edges and troughs) and targeted a degradation sequence from stable troughs to ice wedge melt ponds. I measured surface microtopography, active layer depth, water depth, plant community composition, soil gravimetric moisture, late winter snow depth, and shallow annual ground temperatures. Field data showed that ice wedge degradation drove increases in soil moisture, standing water depth, ground surface collapse, ground temperature, and active layer thaw and snow pack compared to stable troughs. These changing abiotic conditions drove the shift from mesic upland tundra plant communities to unvegetated melt ponds. Interactions between abiotic and biotic factors in degrading troughs increase ground temperature and contribute to positive feedbacks for ice wedge degradation. Analysis of broad-scale factors affecting ice wedge degradation involved the mapping of high-centre polygon distribution across the study area and the distribution of ice wedge melt ponds using high-resolution aerial photographs from 2004. Recent changes in melt pond area were also mapped using imagery dating from 1972. Thermokarst activity in polygonal terrain adjacent to anthropogenic disturbances was also assessed. Polygon fields were more abundant and larger in the northern part of the study area, where ground temperature conditions were most favourable for ice wedge formation. Spatial variation in polygonal terrain density was also related to topography, drainage, and the distribution of lacustrine sediments. Melt pond mapping and assessment of thermokarst at anthropogenic disturbances showed that ice wedges at higher latitudes are more susceptible to degradation primarily because these areas are underlain by larger and more abundant ice wedges. Melt pond mapping confirmed that the polygonal fields north of 69.4°N have shown both large increases and decreases in area, and that polygons in the south have been relatively stable in recent decades. The increased thaw sensitivity of polygonal terrain at higher latitudes has implications for soil carbon dynamics, terrestrial ecosystems, and the planning and maintenance of infrastructure as air and ground temperatures continue to increase. / Graduate / 0329 / 0372 / 0388

abstract: Baseline community composition data provides a snapshot in time that allows changes in composition to be monitored more effectively and can inform best practices. This study examines Arizona Upland plant community composition of the Sonoran Desert through three different lenses: floristic inventory, and fire and reseeding effects. A floristic inventory was conducted at Cave Creek Regional Park (CCRP), Maricopa County, AZ. One hundred fifty-four taxa were documented within Park boundaries, including 148 species and six infraspecific taxa in 43 families. Asteraceae, Boraginaceae, and Fabaceae accounted for 40% of documented species and annuals accounted for 56% of documented diversity. Fire effects were studied at three locations within McDowell Sonoran Preserve (MSP), Scottsdale, AZ. These fires occurred throughout the 1990s and recovered naturally. Fire and reseeding effects were studied at the site of a 2005 fire within CCRP that was reseeded immediately following the fire. Two questions underlie the study regarding fire and reseeding effects: 1) How did fire and reseeding affect the cover and diversity of the plant communities? 2) Is there a difference in distribution of cover between treatments for individual species or growth habits? To address these questions, I compared burned and adjacent unburned treatments at each site, with an additional reseeded treatment added at CCRP. MSP sites revealed overall diversity and cover was similar between treatments, but succulent cover was significantly reduced, and subshrub cover was significantly greater in the burn treatment. Seventeen species showed significant difference in distribution of cover between treatments. The CCRP reseeded site revealed 11 of 28 species used in the seed mix persist 12 years post-fire. The reseeded treatment showed greater overall diversity than burned and unburned treatments. Succulent and shrub cover were significantly reduced by fire while subshrub cover was significantly greater in the reseeded treatment. Sixteen species showed significant difference in distribution of cover between treatments. Fire appears to impact plant community composition across Arizona Upland sites. Choosing species to include in seed mixes for post-fire reseeding, based on knowledge of pre-fire species composition and individual species’ fire responses, may be a useful tool to promote post-fire plant community recovery. / Dissertation/Thesis / Masters Thesis Plant Biology and Conservation 2018

Small mammals are a keystone guild in arid ecosystems; often exhibiting top-down control of the diversity and structure of plant communities. However, changing climate, shifting fire regimes, and the invasion of exotic plants are modifying the structure of arid systems. Environmental changes in these arid systems are likely altering small mammal communities, and therefore, their ecological role. We examined two aspects of the community composition of small mammals in the Great Basin: changes in community composition since large scale sampling of the region began in 1930, and the current population of a sensitive species of small mammal, the dark kangaroo mouse (Microdipodops megacephalus). In Chapter 1, we compared diversity and composition of present day small mammal communities to communities sampled between the years of 1930 and 1980. We sampled 234 historical locations across the eastern Great Basin region during the summers of 2014 and 2015. Our results indicated that diversity, richness, and evenness of small mammals in the Great Basin have declined significantly over the last century (P=0.002, P=0.03, P=0.002). The relative abundance of generalist species has increased, while specialist species have declined (P<0.001, P<0.001). Also, community composition at each site has changed significantly over the past century. Alterations in the community structure of small mammals may have cascading implications for the future of the Great Basin ecoregion. In Chapter 2, we conducted a region-wide survey for the dark kangaroo mouse in western Utah. Four teams sampled 232 locations across western Utah during the summers of 2014-2015. Of the 232 sites sampled, only 5 sites resulted in dark kangaroo mouse captures, totaling 15 individuals. These results could indicate a state-wide population decline for this species, both compared to historic population levels and to the populations surveyed less than ten years ago. The rapid decline may be a result of habitat degradation associated with invasive plant species and increasing fire frequency, the effects of which are exacerbated by the dark kangaroo mouse's life history as an ecological specialist. Unless large-scale habitat restoration and preservation is conducted for remaining populations, it is likely the dark kangaroo mouse will continue to decline within the state.

Le lien entre la macrofaune et les communautés bactériennes benthiques a été déterminé selon deux approches : (1) une approche expérimentale à l’échelle de l’individu ciblée sur les effets de l’activité et de la bioturbation du polychète déposivore de surface Melinna palmata sur la distribution des communautés bactériennes des premiers millimètres de l’interface eau-sédiment ; (2) une approche in situ à l’échelle de la communauté de mise en corrélation des patrons spatiaux de distribution des communautés de macrofaune et de bactéries.Melinna palmata appartient à un nouveau groupe fonctionnel de bioturbation décrit pour la première fois, convoyeur de surface. L’utilisation de ce nouveau modèle biologique a permis de mettre en évidence que les activités de prospection et d’égestions modifient significativement la distribution des communautés bactériennes de la couche oxique de l’interface eau-sédiment. Ce lien est à la fois influencé par l’apport de matière organique de différentes qualités, et impacte la consommation et la minéralisation de cette matière organique.Le lien entre les patrons spatiaux de distribution des communautés de macrofaune et de bactéries a été étudié in situ, dans la vasière Ouest-Gironde. Les deux compartiments ont évolué le long d’un gradient avéré de teneur en matière organique et de taille des particules dans cette vasière.La corrélation des matrices biologiques n’a cependant pas été statistiquement significative et nécessite d’être approfondi. / The link between benthic macrofauna and bacterial communities was assessed with two different approaches: (1) an experimental approach at the individual scale, focused on the effects of behaviour and bioturbation of the deposit feeder polychaete Melinna palmata on the bacteria lcommunity distribution on the very sediment-water interface; (2) an in situ approach at the scale of the community, focused on the correlation between spatial distribution patterns of the two biological compartments. Melinna palmata belongs to a new functional group of bioturbation described for the first time: surface conveyor. Its use allowed determining that prospection and egestion induced a significant change of bacterial communities on the sediment-water interface. This link was influenced by organic matter enrichment while influencing its fate. In a second part, the link between spatial distribution patterns of the communities was assessed in situ in the West-Gironde mud patch. Both macrofauna and bacteria changed along a gradient of organic matter quantity and quality and of particles size described in this system. However, the correlation between matrices was not statistically significant and needs to be more developed.

A study of the aquatic invertebrate communities from two locations (Location 1 and Location 2) within the Matapouri catchment in Northland, New Zealand, was conducted to assess community structure in differing local-scale habitats. Four data collection methods were utilised generating 33,058 adult or larval invertebrates. The sampling methods comprised benthic kick-sampling, sticky trapping, light trapping, and emergence trapping. For the sticky trapping and light trapping, sampling was carried out at three different sites (Sites 1–3) within each location. The sites were situated within three habitat types; native forest, native forest-fringe, and raupo wetland. Emergence trapping also commenced within the three sites, at both locations, but was discontinued after two months, due to the equipment being destroyed by consecutive flooding events (method described in Appendix 1). Benthic sampling was carried out within the Forest and Forest-fringe habitats. Benthic sampling, sticky trapping, and light trapping were carried out following a monthly schedule between June and November 2005. Conductivity, pH, and water temperature measurements were taken concurrently with benthic sampling on a monthly basis, while water velocity and substrate measurements were taken once to assist in habitat characterisation. Overall, 71 taxa were recorded by benthic sampling over the six month period, with a mean of approximately 30 taxa per site per month. In comparison with similar studies elsewhere in New Zealand, a figure of around 30 taxa per sample was high. The benthic macroinvertebrate fauna at all sites was dominated by Trichoptera (19 taxa), Diptera (16 taxa) and Ephemeroptera (10 taxa). This pattern of diversity is similar to that reported in other New Zealand studies. However, in contrast to previous studies, the leptophlebiid mayfly genus Deleatidium was not numerically dominant over the rest of the community, and other leptophlebiid genera (Acanthophlebia, Atalophlebioides, Mauiulus and Zephlebia) were equally represented, possibly reflecting niche partitioning between the groups. The genus Nesameletus was not recorded at any site, despite being one of the core mayfly species in New Zealand streams. The rare mayfly Isothraulus abditus was recorded at one of the forest locations. There are no published records of this species from Northland. Although acknowledged as another of the core New Zealand benthic taxa, the hydropsychid caddisfly Aoteapsyche was not recorded during the study. However, another hydropsychid, Orthopsyche, was commonly recorded, and these may be filling a similar niche to the Aoteapsyche genus. In contrast to the Trichoptera, Diptera, and Ephemeroptera, the Plecoptera fauna was relatively depauperate, probably reflecting the warmer climate of the region and lack of temperature-buffered spring-fed streams. Surprisingly, Zelandobius, a core New Zealand genus, was absent but is regularly recorded in Northland. A species of conservation interest, Spaniocercoides watti, currently recognised as a Northland endemic, was recorded in low numbers. There were no apparent trends in diversity or abundance of benthic invertebrates over time. Also, there were no significant differences in species diversity between the two locations. However, in many cases, taxa were more abundant at Location 2. This may have been due to steeper gradients at Location 2, and the consequent effects on substrate size and streambed stability, as all other physical factors appeared similar between locations. Although several significant differences of individual benthic taxa were recorded, no broad effect of habitat (sites) on species diversity was observable. However, at Location 2, abundances were significantly higher at Site 3 (Forest) compared to Site 2 (Forest-fringe). The reasons were uncertain, but may be attributed to higher retention of allochthonous organic materials, trapped by in-stream cover and larger substrates. Investigations of adult stages by sticky traps supported benthic results recording community compositions and abundances dominated by Trichoptera and Diptera. Plecoptera were poorly represented. Location 2 recorded higher abundances of taxa, particularly Ephemeroptera and Plecoptera. Investigations of adult stages by light traps however did not produce any statistically significant differences in abundances between sites, between locations, or between sites across locations, and it is believed to be due to limited sampling replication combined with some biases of light trapping. This study indicates that the aquatic invertebrate community at Matapouri is diverse but also reasonably representative. Several rare or uncommon insects inhabit the catchment. It is therefore important that Iwi and the local Landcare Group, who invited and supported this research, together with the Department of Conservation, continue their efforts in protecting these areas. The resident fauna have the capacity to restock areas downstream, which are intended to be improved and restored through sediment control and riparian management.

One of ecology’s primary goals is to comprehend biodiversity and its patterns of distribution over space and time. Since microorganisms play a pivotal role in key ecological processes, the diversity of microbial communities may have important implications for the stability and functioning of Earth’s ecosystems. Thus, it is of utmost importance to develop a theoretical foundation but also a conceptual understanding for the mechanisms that generate and maintain microbial diversity. The aim of this thesis is to investigate to what extent local freshwater bacterioplankton diversity, i.e. richness and community composition, is structured by local environmental interactions and/or regional processes. The key objective is to identify ecological linkages between lake bacterioplankton and bacterial communities in connected streams and the surrounding terrestrial landscape, thereby applying a metacommunity approach. To do so, I studied several natural lake bacterioplankton assemblies within different regions of Sweden and assessed both local environmental properties and regional parameters (e.g. dispersal, landscape position). The genetic composition of freshwater bacterioplankton diversity was determined by means of terminal-restriction fragment length polymorphism or 454 pyrosequencing. From the review on the biogeography of bacterioplankton in inland waters it became clear that microbial diversity and its spatial distribution are governed by a complex interplay of both local and regional drivers. In one case, freshwater bacterioplankton communities were structured by local environmental conditions rather than by regional dispersal processes. These local environmental conditions seemed to be equally important in controlling both the total bacterioplankton community and its active fraction. In a study of bacterioplankton communities from five different regions, locally abundant aquatic bacteria were shown to be also regionally widespread, a pattern predicted by neutral theory. Yet, this degree of similarity decreased with increasing environmental heterogeneity. In another study, bacterioplankton richness was controlled mostly by nutrient content, indicating that productivity exerted influence on bacterioplankton richness. However, landscape position and productivity covaried, suggesting that the landscape dictates environmental properties, which then directly structure local bacterioplankton richness. Finally, a review synthesising results from empirical metacommunity approaches and comparing these to theory showed that yet a gap between empirics and theory exists. To conclude, local bacterioplankton diversity appeared to be mainly structured by local environmental properties. However, signatures of neutral processes driving local bacterioplankton community assembly were also recorded.