Made available in DSpace on 2015-04-22T22:12:40Z (GMT). No. of bitstreams: 1 Reysi Jhayne Pegorini.pdf: 1320238 bytes, checksum: adc3625a8f73af8fe95f5eea49051b81 (MD5) Previous issue date: 2013-08-29 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this study was to evaluate the effects and relative importance of biotic and abiotic factors on the temporal and spatial distribution of tadpoles in temporary ponds, in Reserva Biológica do Uatumã, Central Amazon. The study area is composed of terra firme forest localized in a transitional environment between the Guiana crystalline shields and the Amazonian sedimentary basin. The species composition, richness and abundance were determined in three samplings periods during the wet season: January and February, April and June, 2012. The following variables were measured: igarapé width, width of the valley, total area of the pond, conductivity, temperature, depth of the leaf litter, canopy openness, and predator abundance. In the three sampling periods, 4.925 individuals of 20 species, distributed in 7 families, were recorded. The community did not present a uniform temporal distribution, with species substitution in each sample. Across the sampling periods, different environmental variables were responsible for the variation of community composition, such as canopy openness, conductivity and depth of the leaf litter. Nevertheless, when the three sampling periods were analyzed together, effects of depth of the leaf litter, width of the valley and vertebrate prey abundance were detected. These results suggest that pond habitats fluctuate over time. The majority of studies on tadpole communities found strong correlation of community structure and predators, as in this study. Invertebrate predators that use temporary ponds generally have short life cycles and may use the same resources as the tadpoles, operating more as potential competitors than predators. In this study vertebrate predators (fish) were the main structuring force on tadpole community in temporary ponds. In tropical pond systems, they are considered the main predators of tadpoles; they can eliminate entire populations within these environments, mainly in temporary ponds. Therefore, samplings on a single wet season are not sufficient to detect patterns of community structure, mainly when the organisms have short life cycles as the tadpoles in temporary ponds. / Este trabalho teve por objetivos avaliar os efeitos e a importância relativa de fatores abióticos e biótico sobre a distribuição espacial e temporal de girinos em poças temporárias, na Reserva Biológica do Uatumã, Amazônia Central. A área de estudo é composta por floresta de terra firme e está localizada em ambiente de transição entre os escudos cristalinos da Guiana e bacia sedimentar Amazônica. A abundância, riqueza e composição de espécies foram determinadas em três eventos de amostragem durante a estação chuvosa: janeiro e fevereiro, abril e junho de 2012. As variáveis medidas foram: largura do Igarapé, área do baixio, área total da poça, condutividade, temperatura, profundidade do folhiço, abertura de dossel e abundância de predadores. Nos três períodos de amostragem, foram registrados 4.925 indivíduos pertencentes a 20 espécies, distribuídas em 7 famílias. A comunidade não apresentou distribuição uniforme ao longo do tempo, com substituição de espécies em cada amostragem. Entre os períodos de amostragem, diferentes variáveis ambientais foram responsáveis pela variação na composição da comunidade, como a abertura do dossel, condutividade e profundidade do folhiço. No entanto, quando analisados os três períodos de amostragem conjuntamente, foram detectados efeitos das variáveis: profundidade do folhiço, área do baixio e abundância de predadores vertebrados. Esses resultados sugerem que habitats de poças temporárias flutuam ao longo do tempo. A maioria dos estudos com comunidades de girinos encontram relações fortes da estrutura da comunidade com predadores, fato também encontrado no presente estudo. Predadores invertebrados que utilizam poças temporárias geralmente possuem ciclos de vida rápidos e podem estar utilizando os mesmos recursos que os girinos, agindo como potenciais competidores do que como predadores. Predadores vertebrados (peixes) foram os principais estruturadores da comunidade de girinos em poças temporárias no presente estudo. Em sistemas de poças tropicais, eles são considerados os principais predadores de girinos, podendo eliminar populações inteiras dentro destes ambientes, principalmente em poças temporárias. Portanto, amostragens pontuais dentro de uma estação chuvosa podem não ser suficientes para captar padrões de como a comunidade é estruturada, principalmente quando os organismos possuem ciclos de vida curtos como girinos em poças temporárias.

Agricultural intensification reliant on monocrops could change soil health in a way that does not support maximum crop productivity. Twenty-nine-year-old no-till field plots at the University of Kentucky Spindletop research farm showed a significant reduction in corn yields from continuous corn plots compared to those from plots in various types of rotation. The objective of this study was to determine what role soil microbes might play in yield reduction and how management and time effects microbial community structure. Samples were collected from the following treatments: continuous corn (CC), continuous soybean (SS), a 2-year corn/soybean rotation (CCSS), Corn in rotation with soybean with winter wheat cover (C/W/S), and sod controls (SOD). Soil health-related parameters were determined along with microbial community structure using phospholipid fatty acid analysis (PLFA). Results show that there is a strong seasonal dynamic in microbial communities with May, July and September showing the greatest differentiation between treatments. Nonparametric multidimensional analysis (NMDS) shows that microbial communities under SS, CC treatments were significantly different from the CS and CWS treatments across all four years of the study. My findings will prove useful for assessing the contribution of biological indicators to agroecosystem function and will aid in making recommendations of when and how to manage these parameters to improve soil health and maximize yield.

Increased groundwater usage, rainfall decline and activities such as mining have resulted in the acidification of certain wetlands in the south-west of Western Australia. This study investigated the influence of pH, the factor most commonly associated with acidification, on the invertebrate and diatom community structure of 20 wetlands in the south-west region of Western Australia. Few studies in Western Australia have investigated both biotic groups, particularly in relation to pH. Consequently, this study examined the comparative sensitivity of the two biotic groups to pH in order to identify the most effective biotic tool for assessing the ecological impacts of pH decrease. The wetlands included in this study displayed a wide range of pH from acidic (pH < 6.5) to alkaline (pH > 7.5). Other environmental parameters were also variable. Separation of the wetlands into three pH groups; Group 1 – acidic, Group 2 – circumneutral and Group 3 – alkaline, demonstrated that the acidic Group 1 wetlands generally had higher electrical conductivity than the remaining groups. This was probably due to the association of many Group 1 sites with mining and acid sulphate soils. Seasonal trends in environmental variables across the three pH groups were mostly unclear although some trends were evident within the individual pH groups. The study showed that invertebrate community structure differed in response to pH. However, the results also demonstrated that invertebrate distribution patterns were influenced by other factors. / Potential indicator species identified from the study included Macrothrix indistincta and Tanytarsus fuscithorax/semibarbitarsus which were abundant in acidic waters and Alona quadrangularis which was common in circumneutral sites. Taxa such as Calamoecia tasmanica subattenuata were common over a wider range of pH (acidic to circumneutral) but may still have potential to act as indicators of pH decline. Diatom community structure was also shown to be influenced by pH, with the variable identified as a major determinant of diatom distribution patterns. Nitzschia paleaeformis and Navicula aff. cari were generally recorded from acidic wetlands and are potentially useful as indicators of low pH conditions. Brachysira brebissonii and Frustulia magaliesmontana were also identified as species with the potential to indicate pH decline. In contrast, taxa including Gomphonema parvulum, Staurosira construens var. venter and Nitzschia palea were generally associated with moderate to high pH levels. A comparative study of the two biotic groups using multivariate analyses revealed that diatoms were more sensitive to pH than invertebrates. Further investigation with a larger number of environmental variables would be necessary to ascertain the other factors primarily influencing invertebrate community structure. Nonetheless, the findings imply that diatoms and invertebrates differ in their responsiveness to various environmental factors and may provide complementary information on the integrity of a system. Multivariate analyses on an expanded data-set of 40 sites found that pH accounted for the greatest amount of variation in the data and was conducive to the development of a diatom-based pH inference model. / The strongest model was produced using weighted averaging (WA) with classical deshrinking. While the model displayed a high correlation coefficient, the prediction error was also relatively high, probably as a result of the comparatively small and heterogeneous data-set. Incorporation of the data into a larger training set would be likely to improve the predictive ability. Applications for the model include pH reconstructions or use in monitoring programs. The current study has shown that pH is an important variable influencing both invertebrate and diatom community structure in wetlands in the south-west of Western Australia. However, the greater sensitivity of diatoms to pH suggests that they would be the most effective tool for the biological monitoring of pH in wetlands threatened or impacted by acidification. An integrated monitoring program including both diatoms and invertebrates may provide additional information on the impacts of pH decline and the overall integrity of the systems and should be investigated further.

Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2006.

Recent work has demonstrated that vast amounts of soil organic carbon (SOC) are redistributed and buried within Canadian croplands; however, the effects of redistribution on SOC dynamics and biological properties of the soil environment remain unknown. Because soil microorganisms are drivers of carbon (C) turnover in soil, the effects of such processes on microbial community dynamics are important in assessing the overall effects of redistribution and the stability of displaced C. This is particularly important in the face of future climate change scenarios and potential disturbances. The objectives of this study were to examine microbial community dynamics with depth and among landscape positions in an eroded landscape, and to assess C mineralization response between surface and subsurface soil layers in a depositional position. Microbial abundance was highly influenced by SOC redistribution. This was most evident in the buried backslope position where substantial soil and SOC deposition had occurred, creating a very thick A horizon (ca. 80 cm). Phospholipid fatty acid (PLFA) analysis revealed substantial concentrations of microbial biomass located at depth (30-60 cm), which was greater than PLFA concentration at the soil surface and correlated with SOC concentration. Community structure analysis demonstrated the strong influence of landscape position and depth in structuring microbial communities near the soil surface (0-20 cm). Communities in positions that were predominantly erosional were the most different from those in the depositional position, accounting for the largest amount of variation (60%) in the overall analysis. The existence of distinct microbial communities found in depositional material (0-25 cm) and within the buried A horizon (30-80 cm) in the buried backslope position indicate a strong influence of depth and redistribution in structuring microbial communities. The existence of significant viable biomass in the buried A horizon of the depositional position leads to question the persistence of highly concentrated, buried SOC over many decades. When soils from surface (0-5 and 20-25 cm) and subsurface (40-45 and 65-70 cm) depths were incubated in surface-like conditions, greater mineralization response in surface relative to subsurface soils, despite relatively similar SOC concentration, suggests that redistribution protects buried C from decomposition. Distinct microbial communities found at the onset and completion of the mineralization study between surface and subsurface soil layers may indicate the influence of microbial community structure on mineralization response. Depth was the largest source of variation in microbial community structure, and although a shift occurred after exposure to incubation conditions, the effect of depth remained the strongest influence. This work indicates that SOC redistribution strongly influences microbial abundance and community structure development, primarily driven by altered substrate gradients occurring with depth, and suggests that C is less susceptible to decomposition once buried in depositional positions.

This study compared traditional community analysis with stable-isotope trophic analysis to define process-based trophic elements of community structure in the eastern Gulf of Mexico, and developed a predictive capability regarding changes to fish community structure that would be expected from increasing eutrophication. Specifically, it used an existing trawl survey program (SEAMAP) to compare invertebrate herbivore (sponge and sea urchin) isotopes with groundfish isotopes, and then compared the resulting spatial patterns with spatial variation in community structure, as identified by cluster analysis. The comparison was applied to seven NMFS survey zones that extended offshore from the Caloosahatchee River, FL northwest to Mobile Bay, AL. Isotopic patterns were consistent with the presence of an oligotrophic-eutrophic spatial gradient in this region. δ15N values increased in the northwestward direction in herbivores and in each of the 17 fish species examined. In the southern NMFS survey zones, δ13C was elevated in shallow depths for individual fish species, but not in herbivores, indicating a higher proportion of benthically derived biomass contributed to the biomass of fish in the shallow parts of the southern NMFS zones. Fish community analysis using SIMPROF created a similar pattern, with distinct nearshore and offshore communities and also a northwesterly community transition. Among the 17 fish species, five appeared to have obligate dependence on either benthic or planktonic basal resources, while twelve species appeared to be have facultative relationships. Impairment of current water-quality (nutrients, turbidity, light transmission, chlorophyll a) is expected to lead to reductions in the abundance of both obligate and facultative benthic-dependent fishes.

When multiple predators foraging together have different individual consumption rates than predators foraging in isolation, they exhibit non-independent multiple predator effects on prey. I examined multiple predator effects in a system consisting of invasive green crabs (Carcinus maenas L.), native rock crabs (Cancer irroratus Say) and benthic macrofauna prey. First, I examined multiple predator effects when green crabs and rock crabs forage on soft-shell clams (Mya arenaria L.) in different habitat types (sand, sand with artificial seagrass) and assessed the behavioural mechanisms responsible for the observed predation effects. Independent multiple predator effects on prey were detected for most conspecific and heterospecific pairs in both habitat types. In general, crab foraging behaviours were not affected by the presence of another predator. Interactions between predators did not influence foraging behaviours because encounters were infrequent, short in duration and predominantly non-aggressive. A non-independent multiple predator effect on prey (marginally significant) was observed when green crabs foraged with rock crabs in artificial seagrass. This effect, however, could not be explained by the observed crab behaviours. Second, I investigated multiple predator effects when green crabs and rock crabs forage on a soft-sediment macrofauna community. Because crabs did not have significant predation effects on the community throughout the experiment, I did not evaluate multiple predator effects on prey. It is possible that crab predation was not important in regulating the macrofauna community, in which case multiple predator effects were non-existent. Predation may have been suppressed due to a combination of factors, including interactions between predators, harsh environmental conditions or a sub-optimal prey field. Alternatively, my ability to detect significant predation effects may have been hindered because of prey movement in and out of cages or low statistical power. Overall, results from this thesis demonstrate that multiple predator effects on prey may differ with habitat and highlights the importance of conducting behavioural observations to better understand interactions between predators and the resulting consequences for prey. Multiple predator effects on a soft-sediment community should be re-evaluated to assess the importance of these crab species in regulating benthic macrofauna under natural conditions.

Most coastal ecosystems are dominated by marine macrophytes that deliver a range of ecologically and economically important services such as carbon and nitrogen cycling and storage, and habitat provision to a range of associated species. The relative contribution of these services among different vegetated habitats, however, and their alteration due to anthropogenic stressors is little known. In this thesis, I first examined the within and between ecosystem structure and services of eelgrass (Zostera marina) and rockweed (Ascophyllum nodosum) beds in Atlantic Canada. Both habitats significantly enhanced the overall abundance and diversity of associated species, whereas differences in the spe-cies assemblages were attributed to differences in canopy structure within and between habitats. Changes in the canopy structure of the foundation species will affect associated food webs and ecosystem services. Next, I used large-scale field surveys to examine the effects of eutrophication on the structure and services of eelgrass beds. As eutrophication increased, plant dominance shifted from eelgrass to macroalgae and phytoplankton at a regional scale. The faunal community showed increases in filter feeders, detritivores and some herbivores, while sensitive species declined. These faunal changes can be linked to enhanced food availability and predation refuge offered by increased phytoplankton and opportunistic macroalgae. However, the loss of eelgrass and sensitive species highlight the negative consequences of eutrophication on eelgrass ecosystems and the services they provide. I also reviewed the global carbon and nitrogen storage and habitat services of mangroves, salt marshes, seagrass meadows and macroalgal beds. Despite only occupying 0.7% of the ocean area, together these ecosystems make up 12% of the oceanic carbon stock thereby playing an important role in global carbon and nitrogen storage. Moreover, these macrophyte habitats enhanced species richness and abundance of associated fauna and juvenile fishes. Overall, my findings indicate that each macrophyte habitat has its strengths yet all are essential in providing the full range of ecosystem services. Increasing human impacts along the coasts, however, are threatening macrophyte ecosystems worldwide, and their further decline will impair the provision of important services and human well-being. Lastly, I discuss the implications of my work for management and conservation.

To gain a better understanding of contaminating bacteria in bioethanol industry, we profiled the bacterial community structure in corn-based bioethanol fermentations and evaluated its correlation to environmental variables. Twenty-three batches of corn-mash sample were collected from six bioethanol facilities. The V4 region of the collective bacterial 16S rRNA genes was analyzed by Illumina Miseq sequencing to investigate the bacterial community structure. Non-metric multidimensional scaling (NMDS) ordination plots were constructed to visualize bacterial community structure groupings among different samples, as well as the effects of multiple environmental variables on community structure variation. Our results suggest that bacterial community structure is facility-specific, although there are two core bacterial phyla, Firmicutes and Proteobacteria. Feedstock, facility, and fermentation technology may explain the difference in community structure between different facilities. Lactic acid, the most important environmental variable that influences bacterial community structure grouping, could be utilized as an indicator of bacterial contamination. We also identified genes responsible for the multiple antibiotic-resistance phenotype of an Enterobacter cloacae strain isolated from a bioethanol fermentation facility. We performed PCR assays and revealed the presence of canonical genes encoding resistance to penicillin and erythromycin. However, a gene encoding resistance to virginiamycin was not detected.

Platinum mining activities contribute substantially to South Africa's economy since it exceeded gold as economical contributor in 2001. Mining activities contribute to large amounts of waste production in the form of tailings and rock waste, deposited in the surrounding environment of the mine premises. Mining companies are held responsible for damages caused to the surrounding environment. These companies are required to introduce the cost of ecological rehabilitation in their operation costs as well as compile an environmental management plan. Numerous attempts to rehabilitate mine waste have proven unsuccessful. New and improved rehabilitation techniques are required to facilitate in the rehabilitation of these mine spoils. Woodchip-vermicompost produced from platinum mining wastes (woodchips and sewage sludge) was used as an alternative amendment to inorganic fertilisers during the rehabilitation of platinum mine tailings. The effectiveness of the woodchip-vermicompost as an alternative amendment during the platinum mine tailings rehabilitation were monitored using different ecosystem components. A natural veldt in the vicinity of the mine area was randomly selected to serve as a reference site. These ecosystem components selected have previously been shown to be effective as indicators of ecosystem quality. The components selected for this study includes the use of microbial enzymatic activity, microbial community structure, nematode trophic structures, and other mesofaunal groups such as micro-arthropods. The physical and chemical properties of the platinum mine tailings and reference area as well as the vegetation cover of the platinum mine tailings were determined. Statistical and multivariate analyses were use to determine the correlation between the dependent microbial components and dominate independent chemical properties. Nematode trophic structure, Maturity Index, and Plant-Parasitic nematode Index were used to compare the two rehabilitation techniques in terms of nematodes as indicators. Microarthropods family structures were used to compare the two amendments in terms of diversity and abundance. Enzymatic activity was positively affected by the addition of woodchip-vermicompost, than in the sites treated with inorganic fertilisers. The microbial community structure showed no statistically significant (p < 0.05) differences between the two amendments. A higher abundance of nematodes especially plant-parasitic nematodes and bacterivorous nematodes were observed in the woodchip-vermicompost sites than in the inorganic fertilised sites. According to the Maturity Index, both amendments became more enriched during the study period, while the Plant-Parasitic nematode Index showed that the carrying capacity for plantparasitic nematodes on the woodchip-vermicompost sites increased while it decreased in the inorganic fertilised sites, which can be related to the decrease in vegetation cover on the inorganic fertilised sites. Both coloniser (Prostigmata) and persister (Cryptostigmata and Mesostigmata) groups of the micro-arthropods, as well as a higher diversity of micro-arthropods, were present on the woodchip-vermicompost sites whereas the inorganic fertilised sites showed only the presence of colonisers, with a decrease in diversity and abundance of micro-arthropods over the study. The colonisation of micro-arthropods may have been affected by the addition of woodchip-vermicompost and vegetation cover, which contribute to the establishment of suitable microhabitats for these soil biota. By intercorrelating the results, it may be concluded that the addition of woodchip-vermicompost may be an essential part of the rehabilitation process, by contributing to soil organic material to the ecosystem system, which may improve the recolonisation of soil biota and ecosystem processes. However further studies need to be conducted in order to determine the long-term sustainability of the woodchip-vermicompost in providing organic material and sustaining the ecosystem processes. The study also showed the necessity to integrate various ecosystem components when evaluating ecosystem development due to the unique role each component plays and the impact it may have on other components. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2006.