The term hydropeaking refers to anthropogenically induced, short-duration, high-magnitude discharge pulses that are generated in lotic systems for electricity production. The practice of hydropeaking produces the largest source of renewable energy worldwide, and its use is projected to increase through the year 2040. The primary objective of this work was to evaluate the effects of hydropeaking on benthic macroinvertebrate assemblages, which are important components of lotic ecosystems. Results of this work show that, across a wide range of impacted systems worldwide, the consistently observed patterns of elevated benthic macroinvertebrate drift in response to hydropeaking pulses are primarily related to the rate at which discharge is increased (i.e., ramping rate) and secondarily to the time between pulses. In addition, it was shown that taxa inhabiting depositional habitat patches (i.e. fine substrates and slow water velocities) were most susceptible to peaking-induced drift, and that these taxa were also those most prevalent in hydropeaking-impacted systems. Collectively, these results suggest that increased pulse ramping rate and the resulting elevated macroinvertebrate drift may be positive selective forces, which benefit populations adapted for life in hydropeaking-impacted lotic ecosystems. These results provide a greater understanding of the factors that are most important for governing the effects of hydropeaking on benthic assemblages.

Com o intuito de conhecer o histórico da comunidade bentônica no reservatório do Guarapiranga para futuro estudo sobre a influência das diferentes formas de poluição na represa sobre o zoobentos, este trabalho foi desenvolvido a fim de coletar dados históricos da fauna de fundo e se houve variação na estrutura da comunidade ou não. Foram analisados quatro trabalhos realizados no período de inverno em quatro regiões médio-profundal do reservatório (Guarapiranga, Embu-Mirim, Embu-Guaçu e Parelheiros) ao longo dos anos, 1939, 1976, 1996 e 2010. A riqueza de dados presentada nos trabalhos refletiu a evolução do conhecimento em estudos limnológicos no Brasil e no mundo. A densidade de Oligochaeta apresentou aumento ao longo dos anos, assim como a de Chaoboridae. Por outro lado, Chironomidae que apresentava 30% em 1974 é pouco representativo em 2010. O ambiente mostrou forte e crescente enriquecimento orgânico em todos os pontos ao longo dos anos e isso colaborou para uma maior diversidade de grupos detritívoros (Tubificinae e Naidinae - Oligochaeta), por exemplo. Os níveis de oxigênio dissolvido no fundo diminuíram ao longo dos anos em todos as regiões. Chama-se a atenção para a necessidade de biomonitoramento nas 4 regiões da represa, utilizando inclusive os macroinvertebrados bentônicos e análises físicas e químicas do sedimento e a adoção de uma nova forma de gerenciamento deste manancial / With the purpose to know the history of the benthic community in Guarapiranga reservoir for future study about the influence of different sources of pollution in the reservoir over zoobenthos, this study was conducted to collect historical data of benthic fauna and variation in community structure. Four studies conducted during winter in four regions of the reservoir medium-profundal (Guarapiranga, Embu-Mirim, Embu-Guaçu and Parelheiros) over the years, 1939, 1976, 1996 and 2010 were analysed. The best richness of data presented in the works reflected the evolution of knowledge in limnological studies, in Brazil and worldwide. The density of Oligochaeta had an increase over the years as well as the Chaoboridae. On the other hand, Chironomidae presented 30% in the 70\' community and was not representative anymore in 2010. The environment showed strong organic enrichment for all regions along the years, and this has contributed to a greater diversity of detritivorous groups (Tubificinae and Naidinae - Oligochaeta), for example. The dissolved oxygen levels at the bottom declined over the years in all regions. Attention is called to the necessity of biomonitoring in 4 regions of the reservoir, using benthic macroinvertebrates and physical and chemical sediment analyses and the adoption of a new way of managing this system

Com o intuito de conhecer o histórico da comunidade bentônica no reservatório do Guarapiranga para futuro estudo sobre a influência das diferentes formas de poluição na represa sobre o zoobentos, este trabalho foi desenvolvido a fim de coletar dados históricos da fauna de fundo e se houve variação na estrutura da comunidade ou não. Foram analisados quatro trabalhos realizados no período de inverno em quatro regiões médio-profundal do reservatório (Guarapiranga, Embu-Mirim, Embu-Guaçu e Parelheiros) ao longo dos anos, 1939, 1976, 1996 e 2010. A riqueza de dados presentada nos trabalhos refletiu a evolução do conhecimento em estudos limnológicos no Brasil e no mundo. A densidade de Oligochaeta apresentou aumento ao longo dos anos, assim como a de Chaoboridae. Por outro lado, Chironomidae que apresentava 30% em 1974 é pouco representativo em 2010. O ambiente mostrou forte e crescente enriquecimento orgânico em todos os pontos ao longo dos anos e isso colaborou para uma maior diversidade de grupos detritívoros (Tubificinae e Naidinae - Oligochaeta), por exemplo. Os níveis de oxigênio dissolvido no fundo diminuíram ao longo dos anos em todos as regiões. Chama-se a atenção para a necessidade de biomonitoramento nas 4 regiões da represa, utilizando inclusive os macroinvertebrados bentônicos e análises físicas e químicas do sedimento e a adoção de uma nova forma de gerenciamento deste manancial / With the purpose to know the history of the benthic community in Guarapiranga reservoir for future study about the influence of different sources of pollution in the reservoir over zoobenthos, this study was conducted to collect historical data of benthic fauna and variation in community structure. Four studies conducted during winter in four regions of the reservoir medium-profundal (Guarapiranga, Embu-Mirim, Embu-Guaçu and Parelheiros) over the years, 1939, 1976, 1996 and 2010 were analysed. The best richness of data presented in the works reflected the evolution of knowledge in limnological studies, in Brazil and worldwide. The density of Oligochaeta had an increase over the years as well as the Chaoboridae. On the other hand, Chironomidae presented 30% in the 70\' community and was not representative anymore in 2010. The environment showed strong organic enrichment for all regions along the years, and this has contributed to a greater diversity of detritivorous groups (Tubificinae and Naidinae - Oligochaeta), for example. The dissolved oxygen levels at the bottom declined over the years in all regions. Attention is called to the necessity of biomonitoring in 4 regions of the reservoir, using benthic macroinvertebrates and physical and chemical sediment analyses and the adoption of a new way of managing this system

Thredbo Village is a year round alpine resort located in Kosciusko National Park, south eastern New South Wales. Treated sewage effluent from Thredbo Village is discharged to the upper Thredbo River. The river is a rocky bottomed, high mountain stream (> 1,200 m altitude in the study area) flowing predominantly through subalpine woodland, the only major impact on the river within the study area was that of the Thredbo Village alpine ski resort. Nutrient concentrations were measured in the upper Thredbo River monthly from January to September 1983 at 9 sites along the river, both upstream and downstream of the effluent discharge. In addition, invertebrates were collected at the same sites in January, April and July 1983. The near pristine section of the upper Thredbo River upstream of Thredbo Village was low in phosphorus and nitrogen (<20 mg m-3 and <100 mg m-3 respectively). The sewage effluent discharge was high in phosphorus and nitrogen (up to 5,000 mg m-3 and 28,000 mg m-3 respectively). Phosphorus generally returned to concentrations similar to those measured in the pristine sections by 3.5 kilometres downstream of the discharge. Nitrogen (mostly in the form of nitrate and nitrite) often remained elevated down to the most downstream site, 8 kilometres downstream of the effluent discharge. The elevated nutrient concentrations immediately downstream of the effluent discharge stimulated the growth of attached filamentous algae in January when conditions for growth were most favourable. It is concluded that this growth provided an additional food source for several invertebrate taxa, Cricolopus sp. 12E and 160E (Diptera, Chironomidae), Conoesucidae sp. TR6, Oxyethira columba (Trichoptera), Nais sp., Aeolosomatus niveum (Oligochaeta), and Austrocercella tillyardi (Plecoptera), which occurred in higher numbers downstream of the effluent discharge. Downstream of the effluent discharge the taxonomic composition of the invertebrate community was not altered substantially from that upstream, although there was a significant increase in the abundance of the taxa which could take advantage of the increased food resource. The changes in the invertebrate community were not evident 3.5 kilometres downstream of the effluent discharge, which corresponded to the return of phosphorus concentrations to background levels. There were increased abundances of several invertebrate taxa downstream of both Thredbo Village and the rubbish tip in January which were consistent with, but not as great as, those downstream of the sewage effluent discharge. This was likely to be a result of increased nutrient loads from urban runoff and tip leachate at these sites which possibly lead to increased algal productivity. However, nutrient concentrations at these sites were not notably higher than at the control site. The sewage effluent discharge resulted in only small changes to the invertebrate community in April or July 1983.

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

The direct effects of a Virginia trout farm on benthic macroinvertebrates were examined using multiple approaches. Static laboratory tests with the amphipod, Hyallela azteca, were conducted with exposures to water taken from a spring, effluent above a sedimentation basin, and effluent below a sedimentation basin. On-site mesocosms were constructed to expose previously colonized artificial substrates to the same treatments as the laboratory tests. Flat-headed mayflies were also collected from a nearby stream and transported to the mesocosms for a 10 day exposure. There was no significant difference between treatments in the laboratory tests after 20 days, but after 28 days the control was significantly lower than the above sedimentation basin treatment in one test. In the multispecies field tests, a clear decrease in total invertebrate abundance and EPT abundance was seen in the effluent treatments compared to the spring water treatments, with a slight improvement in survival in the treatment below the sedimentation basin. However, only total invertebrate abundance after 21 days produced statistically significant differences. A significant difference was detected between the effluent and the spring treatments in the flat-headed mayfly field test. We suggest that the effects seen in this study do not explain the lack of taxa richness in the receiving stream. The main cause of mortality from trout effluents appears to be solids accumulating upon the organisms, and sedimentation basins should be effective best management practices for protecting macroinvertebrates. / Master of Science

Competing paradigms of community assembly emphasize different mechanisms for predicting patterns in biogeography. Niche assembly emphasizes the role of environmental gradients as filters that organize a metacommunity by locally selecting colonizers with similar functional traits, whereas dispersal assembly emphasizes the importance of source pool characteristics and dispersal limitation in organizing a metacommunity. In this study, I developed a framework that uses spatially explicit patterns in taxonomic and functional measures of community composition as diagnostics for community assembly processes for benthic macroinvertebrates in headwater streams in the southern Appalachians. Distance decay in taxonomic and functional similarity was used to determine the scales at which taxonomic turnover occurred within functional niches. Trait-neutral models of community composition were used as null models to assess which functional traits were the best candidates to explain how community composition was influenced by environmental gradients: an assessment of niche-based community assembly. Regional scale patterns suggested that niche-based community assembly was the dominant mechanism organizing community composition in headwater streams at local scales (<30km). Therefore, I compared how well trait-neutral models identified functional traits as relevant to community sorting against how well observed trait distributions correlated with environmental variation at a local scale, in the Ray Branch catchment (<10km study extent). Functional traits exhibiting non-random distributions within the Ray Branch watershed were most strongly correlated with environmental variation. Lastly, I assessed how the influences of niche and dispersal assembly on benthic macroinvertebrate community composition were affected by disturbance (shelterwood logging). Environmental variables defining the habitat template, and macroinvertebrate community composition, were measured before and after the disturbance; and path analysis was used to quantify the disturbance effect. The relationship between environmental variation and functional composition increased following logging, indicating disturbance augmented the influence of environmental filters, and consequently, the importance of niche-based community assembly. My dissertation provides the framework for a novel assessment of taxonomic and functional community composition data to infer the types of ecological dynamics that organize communities in the landscape. Additionally, this work provides a theoretical basis for assessing how dominant ecological processes change, in predictable ways, in response to changes in the habitat template. / Ph. D.

Understanding sedimentation impacts to benthic macroinvertebrates in headwater, mountain streams is a top priority of watershed management programs in the Chattahoochee National Forest. Five studies involving the analysis of historical, biological survey data and current data were conducted to improve our understanding of macroinvertebrate response to sedimentation and to support the development of biological information for sediment load models to be applied in the Chattooga River watershed. An initial analysis of historical data involving a composited, macroinvertebrate reach-scale sample revealed weak relationships between assemblage metrics and sedimentation, which was similar to results of two recent macroinvertebrate studies that found biological ratings of good or excellent with reported physical impact attributed to sedimentation. Those findings and field reconnaissance in the Chattooga River watershed revealed that patchy, coarse sands may be the primary issue of concern regarding sedimentation impact to benthic macroinvertebrates. Therefore, a modified sampling approach was used to investigate relationships of macroinvertebrates and environmental conditions that included micro-habitat patches containing coarse sands, a product of erosion associated with Southern Blue Ridge, silicate parent geology. At the microhabitat, patch scale, flow velocity was the main environmental factor associated with a macroinvertebrate assemblage gradient, and was significantly correlated with percent deposited sediment across 264 samples. The high dominance of just a few macroinvertebrate genera, and the majority lack of individual macroinvertebrate associations with dominant substrate types may suggest that the dominant macroinvertebrates utilize a multi-microhabitat portion of the streambed at any given time, which may be due to the homogenization of streambeds due to sand (providing ease of movement) and its immobility (low bedload volume and sand patch shift). Because flow was the only significantly correlated environmental variable on an assemblage gradient produced by ordination (and was individually correlated with dominant substrate and percent deposited sediment), a subsequent study was conducted to determine macroinvertebrate sensitivity to deposited sediments among two flow-differentiated habitat types. Results showed that more taxa were related to a gradient of percent deposited sediment in fast water habitats, and no taxa were positively correlated with percent deposited sediment. Indicator species analysis found a number of taxa that were associated with a four-level grouping of percent deposited sediment levels. Therefore, a final study involved calculating deposited sediment tolerance values using indicator species associations and individual cumulative abundances across percent deposited sediment levels. The final index developed from cumulative abundances showed a relationship with deposited sediment within the range 0 – 30%, and that low range was due to the low deposited sediment levels at which all 50% cumulative abundances fell (1 - 10%). The sedimentation index produced from indicator species analysis produced a reach-scale index that was related to percent pool embeddedness. Key findings from these studies are: (1) sand is the primary deposited sediment type, with most streambed comprised of cobble-sand substrate, (2) few taxa are associated with deposited sand substrate, (3) there are high numbers of a relatively few dominant taxa across samples and streams, (4) macroinvertebrate response to deposited sediments is greatest in fast water habitats, and (5) the developed sedimentation biotic index is a potential, assemblage-level indicator of increasing sedimentation in these headwater systems. The functional and habit organization of the four most dominant taxa determined in recent studies suggest that they may be utilizing sand patches for crawling and collecting food, therefore structurally adapting to long-term, press disturbances due to historical and contemporary anthropogenic activities and natural erosion. In addition, macroinvertebrate assemblage composition in these streams indicates overall good "health" and suggests streambed stability in the presence of a large portion of coarse sand. However, an important question that remains involves sand movement along streambeds and the ecological consequences of continued sediment inputs to these headwater systems. / Ph. D.

Bioassessment is the concept of evaluating the ecological condition of habitats by surveying the resident assemblages of living organisms. Conducting bioassessment with benthic macroinvertebrates is still evolving and continues to be refined. There are strongly divided opinions about study design, sampling methods, laboratory analyses, and data analysis. Two issues that are currently being debated about study design for bioassessment in streams were examined here: 1) what habitats within streams should be sampled; 2) and is it necessary to identify organisms to the species level? The influence of habitat sampling design and level of taxonomic identification on the interpretation of ecological conditions of ten small streams in western Virginia was examined. Cattle watering and grazing heavily affected five of these streams (impaired sites). The other five streams, with no recent cattle activity or other impact by man, were considered to be reference sites because they were minimally impaired and represented best attainable conditions. Inferential and non-inferential statistical analyses concluded that multiple habitat sampling design was more effective than a single habitat design (riffle only) at distinguishing impaired conditions, regardless of taxonomic level. It appeared that sampling design (riffle habitat versus multiple habitats) is more important than taxonomic identification level for distinguishing reference and impaired ecological conditions in this bioassessment study. All levels of taxonomic resolution, which were studied, showed that the macroinvertebrate assemblages at the reference and impaired sites were very different and the assemblages at the impaired sites were adversely affected by perturbation. This study supported the sampling of multiple habitats and identification to the family level as a design for best determining the ecological condition of streams in bioassessment. / Master of Science

This study was carried out to characterize ponds and aquaculture systems, and also to determine both the potential and actual impacts of pond aquaculture effluents on receiving stream quality in the Ashanti and Brong Ahafo regions of Ghana. Water, fish and macroinvertebrate samples were collected from upstream, downstream and nearby reference streams of, and questionnaires administered to, 32 farms. Total settleable solids were higher in ponds than reference streams (p = 0.0166); suspended solids was higher in ponds than reference streams (p = 0.0159) and upstream (p = 0.0361); and total phosphorus was higher in ponds than reference (p = 0.0274) and upstream (p = 0.0269). Total nitrogen was most clearly higher in ponds than all other locations: p = 0.0016, 0.0086 and 0.0154 for the differences between ponds and reference, upstream, and downstream respectively. BOD5 level was also higher in ponds than all locations (p = 0.0048, 0.0009, and 0.0012 respectively). Also, non-guarding fish species were more abundant in reference streams than downstream (p = 0.0214) and upstream (p = 0.0251), and sand-detritus spawning fish were less predominant in reference streams than upstream (p = 0.0222) and marginally less in downstream locations (p = 0.0539). A possible subsidy-stress response within study streams was also observed. Hence, ponds are potential sources of these water quality variables to receiving streams. Effluent-receiving streams, generally, were not much different from reference streams in terms of most the metrics of community structure and function used in the comparisons. Hence, even though receiving streams in Central Ghana may not be severely impacted by aquaculture effluents at the moment, the management of pond effluents will determine the scale of future impact. Vegetable, cereal, and livestock farming could serve as additional sources of fecal streptococci and coliform bacteria and nutrient-enrichment within the study area, besides aquaculture, and so these industries must also be included in efforts to minimize pollution of these streams. / Master of Science