Seagrass productivity is largely limited by nutrient and light availability. However, increasing evidence suggests that sedimentary geochemical processes may play an essential role in seagrass productivity/health. Much of this work has been largely phenomenalistic and has not clearly identified the spatio-temporal behavior of the major geochemical parameters involved in diagenesis of seagrass sediments. In this study, a much broader range of both dissolved and solid phase chemical parameters in eelgrass vegetated sediments was investigated. Parallel measurements were made on adjacent unvegetated sediments (<10 m) to more clearly refine the specific influences of seagrass (Zostera marina) on chemical gradients in associated sediments. Previous studies have pointed strongly toward diurnal ??ventilation?? of sediments vegetated with seagrass by the exudation of photosynthetically produced oxygen. However, strong lateral variability of sediment geochemical parameters among and between seagrass vegetated and unvegetated sediments made the observation of diurnal effects sufficiently difficult. Changes resulting from temporal variability were difficult to discern within the spatial variability. A critical question that is often not dealt with in the study of the early diagenesis of sediments is what spatial and temporal sampling intervals are required to account for the dominant source of variability. The auto-covariance function (ACF) was used to determine the optimum scaling length for sample intervals (?x) of ?H2S and Fe2+. Characteristic scale lengths obtained for sediments from seagrass environments are not significantly different from those observed for unvegetated sediments and averaged 13.7?? 2.2 mm. Lateral variations in our scales analyses showed that scale length approximated our sampling interval and that lateral sampling intervals were smaller than the vertical sampling intervals. Our results indicate that macrofauna dwelling in the sediment, the seagrass root/rhizomes, and aggregations of bacteria, microalgae, and meiofauna may be responsible for the vertical and lateral variability. Model calibrations and sensitivity analyses from a sediment-seagrass diagenetic model revealed that changes in physical parameters of the sediments (irrigation, advection, and porosity, for example) had the greatest effect on organic carbon and total dissolved sulfides. This study revealed that sedimentary geochemical parameters that are both vertically and laterally heterogeneous may also affect seagrass productivity.

Fecal indicator bacteria (FIB) such as Escherichia coli and enterococci are used to assess microbiological water quality in recreational waters worldwide. FIB are used with the assumption that their presence correlates with that of fecal-associated pathogens in recreational waters. In aquatic habitats, several factors can interfere with the predictive relationship between FIB and pathogens including extended survival of FIB in secondary habitats such as sediment, vegetation and sand. Furthermore, many biotic (e.g. predation from bacterivorous protozoa and competition from indigenous bacteria) and abiotic factors (e.g. temperature, salinity, ultraviolet (UV) light irradiation, and nutrient availability) can influence the fate of FIB and pathogens associated with gastrointestinal tracts of animals (enteric pathogens) in secondary habitats. The relative importance of these factors is not well characterized, thus limiting our knowledge on the efficacy of FIB as indicators of fecal contamination and microbial pathogens in water. The studies presented in this dissertation investigated the influence of biotic (predation from bacterivorous protozoa and competition from indigenous bacteria) and abiotic factors (e.g. nutrient availability) on the survival of FIB (E. coli and Enterococcus faecalis) and pathogens (E. coli O157 and Salmonella enterica) in aquatic habitats. Water and sediment samples were collected from a fresh water river source (Hillsborough River, Tampa, FL) and used to prepare a series of outdoor mesocosm experiments. In each experiment, biota treatments were varied to include various combinations of predation and competition, both or neither. Manipulation of biota treatments involved disinfection of water and baking of sediments to remove indigenous microbiota, or addition of cycloheximide or kanamycin to diminish the effect of predation from natural protozoa or competition from indigenous bacteria respectively. Bacterial levels in all experiments were monitored over a five day period. In the mesocosms investigating the effect of predation and competition on FIB (E. coli and Ent. faecalis) and a pathogen (E. coli O157:H7), predation had a detrimental effect on the survival of the FIB and pathogen in the water column but only influenced the survival of the FIB in the sediment. Unlike predation, competition from indigenous bacteria influenced the survival of E. coli but not Ent. faecalis in both water and sediment. The second set of mesocosms investigated the effect of predation on two motile and non-motile enteric bacteria types (E. coli O157 and S. enterica), each with a motile and non-motile counterpart. An allochthonous predation source (Tetrahymena pyriformis) was added into the mesocosms to supply a consistent level of predation. Motility had a significant positive effect on the survival of S. enterica in the water and sediment but had negative significant effect for E. coli O157 in sediment only. Motility also played a more important role in the sediment compared to predation while predation played a more important role in the water column for both bacteria types. The third study compared the relative effects of predation, competition and nutrients on the survival of E. coli. Natural waters (not amended with nutrients) served as a baseline condition to which organic nutrients were added in two increments. Significant interactions among predation, nutrients and competition (all possible combinations) were observed. Interactions between predation and nutrients as well as competition and predation also accounted for the greatest effects (10% and 8% respectively). The interaction between predation and competition was particularly pronounced at the highest nutrient level. These studies reveal that predation, competition and nutrients are all important factors in the survival of FIB and enteric bacteria in water and sediment, and provide new observations on the relative magnitude of these effects. I show that survival characteristics of FIB and enteric bacteria in secondary habitats can vary depending on bacteria type (FIB or pathogen), location (water or sediment), prey characteristics (motile or non-motile) and specific environmental stressor present (predation, competition or nutrients). The findings of this dissertation provide new insights on the ecology of FIB and enteric bacteria in secondary habitats and underscore the importance of biotic and abiotic factors as determinants of the fate of FIB and enteric bacteria in secondary habitats.

Revised; Originally Published: 2006 / 2 pp.

Fossil fuels are not sustainable due to their worldwide depletion and greenhouse gas (GHG) emissions. Transportation biofuels produced from microalgae are sustainable if GHG emissions are lower than fossil fuels and the sources for materials used during production are sustainable. Four areas were evaluated to address these concerns. First, a study of peer reviewed life-cycle analyses (LCAs) was performed. The purpose of this evaluation was to determine which processing choices during cultivation have the most impacts. Data from nine authors was converted to similar units, and a new LCA was performed to evaluate the impacts. Overall GHG emissions per kg of algae cultivation ranged from 0.1 - 4.4 kg CO₂ eq. / kg algae, with the most of the emissions coming from fertilizer contributions. The second topic evaluated was the GHG emissions from experimental dewatering technologies. The five experimental technology emissions, for acoustic harvesting, membrane filtration, flocculation, electrocoagulation and flocculation plus belt filtration, were compared to a modeled dissolved air flotation technology and a fossil fuel source. For a functional unit of one MJ of renewable diesel (RD), membrane filtration had the lowest GHG emissions at 40.8 g CO₂(eq)/MJ RD. Dissolved air flotation was the highest scenario at 51.9 g CO₂(eq)/MJ RD. All technologies were lower than gasoline at 90.7 g CO₂(eq)/MJ gasoline. The third topic evaluated was the GHG emissions from the materials used for plant construction. A LCA was performed for the infrastructure materials and compared to results from the fuel-cycle. Plastic from pond liners had the largest contribution to GHG emissions for the baseline case. Increasing productivity and lipid content both decreased infrastructure emissions. The final topic evaluated was the sustainability of nitrogen, phosphorus and potassium used for microalgae growth. Results show that the surplus of world fertilizers cannot sustain large scale algae production in the United States. Technology choices that can recycle nutrients lower the overall requirement. Alternative sources of nutrients, like concentrated animal feeding operations, can provide enough nutrients for large scale production of algae.

This study is the geochemical examination of mineral weathering and its path from hinterland, through sediment deposition and pedogenesis, to its dissolution and eventual uptake into plants or precipitation as carbonate minerals. The three papers examine the rate and character of carbonate and silicate mineral weathering over a wide range of climatic and tectonic regimes, time periods, and lithologies, and focus on very different questions. Examination of the 87Sr/86Sr ratios of architectural ponderosa pine in Chaco Canyon, New Mexico confirms a societally complex style of timber procurement from the 10th to the 12th centuries. In El Malpais National Monument, New Mexico, we measured the 87Sr/86Sr ratios in local bedrock and soils and compared them to the leaf/wood cellulose of four conifers (Pinus ponderosa, Pinus edulis, Juniperus monosperma, Juniperus scopulorum), a deciduous tree (Populus tremuloides), three shrubs (Chrysothamus nauseosus, Fallugia paradoxa, Rhus trilobata), and an annual grass (Bouteloua gracilis) and a lichen (Xanthoparmelia lineola). We found that plant 87Sr/86Sr ratios covaried with variations in plant physiognomy, life history, and rooting depth. In addition, the proportion of atmospheric dust and bedrock mineral contributions to soil water 87Sr/86Sr ratios varied predictably with landscape age and bedrock lithology. On the Himalayan floodplain, soils and paleosol silicate weathering intensities were measured along a climatic transect and through time. Overall, carbonate weathering dominates floodplain weathering. But, periods of more intense silicate weathering between 9 - 2 Ma, identified in soil profile and in the 87Sr/86Sr ratios of pedogenic carbonates, appear to be driven by changes in tectonic, rather than climatic, regime. All three papers are good examples of how 87Sr/86Sr isotopic tracer studies can shed light on pedogenic formation rates and internal processes. The complexity of each system warns against generalizations based on just one locale, one species or lithology, or a few isotopic ratios.

In this work, a differential reactor was used to expose all the biofilter packing material (compost) to a uniform toluene concentration in air. The reactor was combined with water content control using the suction cell principle and traditional inlet concentration, temperature and humidity control. The matric potential was controlled using the suction cell principle between -5 to -300 cm H₂O which controlled the water content between 0.99 and 2.30 g g⁻¹ (dry weight). Two types of compost were used, with different water retention curves with no observed difference in elimination capacity. The elimination capacity varied between 2.7 g m⁻³r hr⁻¹ and 21 g m⁻³r hr⁻¹ with low potential causing low removal rates. The reduction in EC at low matric potentials was attributed to several factors: loss of water availability to the organisms, water redistribution in the medium, non-adaptable micro-organisms, and reduced mass transfer. Cultures isolated from compost were used to inoculate the reactor to create a biofilm. A maximal observed surface EC of is 0.17 g m⁻²r hr⁻¹ and a specific removal rate of 1250 g m⁻³b hr⁻¹ is measured. These values were used in modelling the biofilter performance. The EC was dependent on the residual toluene concentration. The EC increased with increasing toluene concentration until reaching a critical concentration. Above this concentration, 100 – 300 ppm (0.37- 1.11 g m⁻³) depending on biofilm thickness and area of coverage, the EC was constant. Three toluene dependency curves were fitted using a zero order and a composite model using a weighted average of a zero and first order component. From the data the critical concentration (Ccrit) and the ECcrit was found and used to determine the biofilm thickness. It was estimated to be between 68 and 134 µm. Using a qmax of 1250 g m⁻³b hr⁻¹ and optimising the model a Ks of 1.3•10⁻¹ g m⁻³g was found. This was comparable to values found in the literature. There was no significant difference in the fit between both models. The Ks was low compared to the majority of the data, which means that the zero order part of the composite model dominated. Nitrogen and other nutrients were added to investigate their influence on the elimination capacity (EC) of toluene. Also the effect of temperature on the EC was investigated between 14 and 60 °C. Maximal removal rates were found between 25 and 55 °C. The EC decreased by 90% going from 55 to 60 °C and took many weeks to recover. Without any extra nitrogen added to the media, the EC averaged around 6 ± 0.3 g m⁻³r h⁻¹. Although the average EC was lower than most reports for toluene removal, it was still in the general range reported. When NH4Cl (1 g l⁻¹) was added to the reactor, the EC increased to 41 ± 1.7 g m⁻³r hr⁻¹. Similar effects were observed with nitrate addition; the steady state EC doubled from 30.1 ± 0.9 g m⁻³r hr⁻¹ to 76.3 ± 2.5 g m⁻³r hr⁻¹. Other macronutrients tested like phosphate, sulphate, magnesium, calcium and iron did not increase the EC.

Plant-parasitic nematodes (PPN) are a serious problem in vegetable production and can cause severe damage to several crops. In rural, low-input farming nematode damage is much higher and yields can be completely destroyed. Some Commercial nematicides have been withdrawn from the market due to health and environment concerns. These need to be replaced by alternative nematode control strategies of which soil amendments is one alternative. Nine non-crop plant species used in various forms in traditional healing, viz. Cassia abbreviata, Cissus cactiformis, Euphorbia ingens, Ipomoea kituiensis, Maerua angolensis, Senna petersiana, Synadenium cupulare, Tabernaemontana elegans and Urginea sanguinea were screened under glasshouse conditions for their effect on the plant-parasitic nematode (PPN) (Meloidogyne incognita) on tomato. Subsequent assessments in microplots and in the field supported the glasshouse results in terms of suppression of root-knot nematode numbers with crudely milled soil amendments of C. cactiformis, M. angolensis and T. elegans. Tomato growth responses in these trials showed a tendency of phytotoxic effects after treatment of soil with crude leaf meal of E. ingens and S. cupulare. In the microplot study, the overall soil-amendment treatment effect was greater than that of three soil types on the performance of the tomato, although soil type might have had an effect on nematode suppression. Due to lack of correspondence between tomato leaf nutrient contents and the nutrient contents of the soil amendments it is suggested that these noncrop materials had negligible soil fertilization effects. In vitro bioassay studies confirmed that extracts of varying polarity of both plant products M. angolensis and T. elegans might be toxic to J2 stages of the root-knot nematode M. incognita. All extracts tested of M. angolensis caused immobility of J2, whereas only three extracts of T. elegans affected mobility of J2 adversely. Duration to 50 % effect, as well as extract concentration to cause immobility of the J2 varied but where movement ceased the J2 did not recover for up to 98 hours. This study has demonstrated the potential of locally available botanical materials for use as amendments in plant-parasitic nematode management and tomato growth and productivity improvement. This would particularly be true for small-scale application in subsistence agriculture. It is believed that these amendments could be used as control measures in integrated nematode control strategies. Their potential use could be adopted by small-scale farming communities, domestic gardeners and commercial farmers in the Mpumalanga, Limpopo and Kwazulu/Natal Provinces of South Africa where the relevant materials are available in useful quantities. Over-exploitation of natural resources should be avoided at all cost, however. / Thesis (PhD (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

Plant-parasitic nematodes (PPN) are a serious problem in vegetable production and can cause severe damage to several crops. In rural, low-input farming nematode damage is much higher and yields can be completely destroyed. Some Commercial nematicides have been withdrawn from the market due to health and environment concerns. These need to be replaced by alternative nematode control strategies of which soil amendments is one alternative. Nine non-crop plant species used in various forms in traditional healing, viz. Cassia abbreviata, Cissus cactiformis, Euphorbia ingens, Ipomoea kituiensis, Maerua angolensis, Senna petersiana, Synadenium cupulare, Tabernaemontana elegans and Urginea sanguinea were screened under glasshouse conditions for their effect on the plant-parasitic nematode (PPN) (Meloidogyne incognita) on tomato. Subsequent assessments in microplots and in the field supported the glasshouse results in terms of suppression of root-knot nematode numbers with crudely milled soil amendments of C. cactiformis, M. angolensis and T. elegans. Tomato growth responses in these trials showed a tendency of phytotoxic effects after treatment of soil with crude leaf meal of E. ingens and S. cupulare. In the microplot study, the overall soil-amendment treatment effect was greater than that of three soil types on the performance of the tomato, although soil type might have had an effect on nematode suppression. Due to lack of correspondence between tomato leaf nutrient contents and the nutrient contents of the soil amendments it is suggested that these noncrop materials had negligible soil fertilization effects. In vitro bioassay studies confirmed that extracts of varying polarity of both plant products M. angolensis and T. elegans might be toxic to J2 stages of the root-knot nematode M. incognita. All extracts tested of M. angolensis caused immobility of J2, whereas only three extracts of T. elegans affected mobility of J2 adversely. Duration to 50 % effect, as well as extract concentration to cause immobility of the J2 varied but where movement ceased the J2 did not recover for up to 98 hours. This study has demonstrated the potential of locally available botanical materials for use as amendments in plant-parasitic nematode management and tomato growth and productivity improvement. This would particularly be true for small-scale application in subsistence agriculture. It is believed that these amendments could be used as control measures in integrated nematode control strategies. Their potential use could be adopted by small-scale farming communities, domestic gardeners and commercial farmers in the Mpumalanga, Limpopo and Kwazulu/Natal Provinces of South Africa where the relevant materials are available in useful quantities. Over-exploitation of natural resources should be avoided at all cost, however. / Thesis (PhD (Environmental Sciences))--North-West University, Potchefstroom Campus, 2013

The structure of phytoplankton communities was examined seasonally across five rivers with a focus on small cells and their relative importance. Picophytoplankton (0.2-2 μm), previously considered insignificant in rivers, reached densities as high as those observed in lakes and oceans (~ 10e4-10e5 cells/mL). Their relative importance was not a function of trophic state with the highest contribution to algal biomass found in the most eutrophic river. Body size distributions were analyzed from both chlorophyll-a size fractions and taxonomic enumerations; no significant effect of river or season was detected, suggesting that phytoplankton size distribution is not a useful metric of change in rivers. Unlike lake ecosystems, the rivers were uniformly dominated by small cells (< 20 μm). Taxonomic analyses of the seasonal succession did not reveal a common periodicity of particular divisions (e.g. diatoms). However, strong dominance was more typical of eutrophic rivers even though taxa richness was similar.

Die Broschüre gibt einen Überblick zu Methoden, mit denen die Bodenfruchtbarkeit von Ackerflächen bewertet werden kann, sowie Hinweise zu deren Anwendung. Dazu gehören unter anderem die Spatendiagnose, Bodenuntersuchungen und Nährstoffbilanzierungen.