No description available.

No description available.

No description available.

No description available.

Three novel methods were examined to assess the effects of nutrient enrichment in three sub-tropical east Australian estuaries with differing levels of catchment disturbance. The Manning and Wallamba River catchments are 8927 and 500 km2 respectively and support intensive livestock agriculture and some residential development, whereas the smaller Wallingat River catchment is 185 km2 and is mostly forested. The Wallamba and Wallingat Rivers flow into Wallis Lake, which was the site of an environmental crisis in 1997 when the consumption of sewage-contaminated locally grown oysters caused an outbreak of Hepatitis A. This study contributes valuable and extensive water quality data to assess rehabilitative works in Wallis Lake, and in other estuaries, to reduce the input of nutrients such as sewage. The importance of various sources, loads and sinks and the dispersion and assimilation of nutrients were quantified and compared for each estuary. An ecological model coupled with a one-dimensional hydrodynamic box model revealed that nearly all of the nitrogen inputs to the modified Wallamba River entered as runoff from the intensively livestock farmed upper catchment. In contrast, in the forested Wallingat River nitrogen was generated internally from anoxic sediments and was also longitudinally dispersed upstream from the junction with the modified Coolongolook River. Bloom conditions of up to 59 mg m-3 were observed in the Wallamba River between 7 and 11 days after the storms, but in spite of high concentrations of biologically available nitrogen in the forested Wallingat River, phytoplankton biomass was low due to phosphate limitation. Longitudinal dispersion could not counter phytoplankton growth in the modified Wallamba River, in spite of large increases in river flow. Estimates of grazing pressure by the pygmy mussel, Xenostrobus securis, demonstrate that it could contribute up to half of the phytoplankton loss. The inter-tidal mangrove pneumatophore habitat of X. securis allows filtering of the upper water column from the lateral boundaries in a vertically stratified water column, exerting top-down control on phytoplankton biomass. The optical plankton counter (OPC) can provide an in situ, rapid assessment of zooplankton productivity over large temporal and spatial scales from the size distribution of zooplankton. High concentrations of sub-resolved particles, including suspended detritus, have hampered the use of the in situ OPC in estuaries. Up to 58 counts L-1 due to the coincidence of sub-resolved particles passing through 100 ??m mesh were detected by the laboratory OPC in Manning, Wallamba and Wallingat River water samples. The influence of these erroneous counts on in situ OPC measurements was assessed by comparison with measurements of simultaneously collected net zooplankton measured using the laboratory OPC. In situ OPC measurements of total zooplankton abundance could be corrected for erroneous counts of sub-resolved particles using laboratory OPC measurements of 100 ??m mesh filtered water samples from the same site, but estimates had large associated error and information on the size structure of the zooplankton community is sacrificed. In contrast to expected relationships, no meaningful or significant correlations were found between the number or biomass of sub-resolved particles and in situ light attenuance. Laboratory OPC measurements of net zooplankton in each estuary revealed that the modified Manning and Wallamba Rivers supported a greater biomass of zooplankton compared to the forested Wallingat River. The normalised biomass size spectra of net zooplankton responded to both production of small particles and predation and loss of large particles. The effect of catchment disturbance on the nitrogen and carbon stable isotope ratios (??15N and ??13C) of X. securis was investigated in the three estuaries. Manning and Wallamba River mussels were enriched in ??15N by an average of 3.2??? and 1.5??? respectively compared to mussels from the forested Wallingat River. The isotope values of particulate organic matter showed a similar pattern to mussels, indicating a direct link between them within each estuary. A multiple regression model of mussel ??15N using the fractions of land used for livestock agriculture and residential development within 5 km zones from river networks to a distance equivalent to a tidal ellipse from sites explained 67% of the variation in mussel ??15N with 95% of the differences lying within 1.6??? of observed values. Increasing fractions of land used for livestock agriculture in the regression equation depleted estimated mussel ??15N indicating the use of cow manure as a nutrient source with a value of 2.0???. Increasing fractions of land used for residential development enriched estimated mussel ??15N, indicating the use of human-derived waste with a value of 20.8???.

Phytoplankton dynamics in Auke Bay, Alaska, were studied during summer, 1969. Nitrate, chlorophyll a, particulate organic carbon, phytoplankton and zooplankton species composition and hydrographic and meteorological data were collected and analyzed. Nitrate input into Auke Bay through freshwater runoff was negligible. A bloom of Thalassiosira aestivalis formed the spring bloom in Auke Bay in 1969. No phytoplankton bloom occurred during a June period when winds were light and variable. Two major blooms of Skeletonema costatum occurred after periods when Auke Bay surface layers were mixed by wind-induced turbulence. The water column became nearly isothermal after periods of high wind mixing although a pronounced density and halal structure persisted, a consequence of input of freshwater to the bay from Auke Creek. Examination of fecal pellets collected from the bay and results of laboratory grazing experiments suggested that Skeletonema costatum was not grazed by zooplankton living in Auke Bay. Nonlinear ordinary differential equations were written to describe phytoplankton and nitrate dynamics in Auke Bay. The phytoplankton dynamics equation included formulations for time-varying insolation and for time-varying wind mixing coefficients. Formulations for effects of nitrate concentration on the photosynthetic assimilation number and for effects of phytoplankton standing crop on the extinction coefficient of light in the water column were included. The nitrate dynamics equation included a formulation for effects of wind-mixing of nitrate-rich water into the euphotic zone from deeper layers of the water column, as well as a formulation for utilization of nitrate in phytoplankton growth. Computer simulation response of the equations reproduced the bloom pattern observed in the field data with some discrepancies caused by assumptions used in model development. The phytoplankton and nitrate model response was strongly coupled to the pattern of the wind-mixing coefficient, as required by the field data. Variations in model parameters had little effect on phase relations between model response and field data but strongly affected model response magnitude. / Graduation date: 1972

This study of the immediate, localized effects of a small dredging operation on the benthic invertebrate community in the shipping channel of Coos Bay, Oregon, was designed: 1) to measure the extent of the physical removal of benthic macro- and meiofauna by hopper dredging; 2) to record the subsequent benthic effects of mid-channel spoiling; and 3) to monitor the rate and pattern of biological readjustment in the affected areas. Replicate Shipek grab samples before and after dredge operations were restricted spatially and temporally to delineate rapid and localized biological responses. Faunal abundance, taxa composition, species diversity and qualitative sediment characteristics were studied. Immediate declines in faunal abundance at the dredge and spoil sites were temporary and re-adjusted to pre-dredging abundance levels within 28 days. Temporary increases in diversity reflected changes in the relative abundance of taxa arising from siltation and burial of organisms. Following re-adjustment, populations increased in all areas except the dredge channel. Localized population declines are hypothesized to result from the unsuitability of newly exposed sediment for settlement of pelagic larvae. Although most taxa were adversely affected by dredging activity, Capitella ovincola was relatively unaffected and increased dramatically within the dredge channel within 18 days after dredging. Qualitative sediment characteristics were generally the same before and after dredge operations except for localized increases in wood debris at both dredge and spoil sites. The effects of dredging activity are thought to be dependent on: 1) the size and duration of the dredge operation, 2) pre-dredging history and frequency of dredging, 3) the type of benthic community, 4) depth of water and sediment type, 5) draft and size of the dredging vessel and 6) shipping and related harbor activities. The direct, benthic effects of this dredging operation were short term. The temporary nature of these changes was linked to the small scope of the dredging operation and the adaptability of the benthic community. It is hypothesized that periodic disruption of the sediment surface by small scale maintenance operations may have less effect on the benthic community than the daily presence of heavy shipping and industrial and domestic pollution. / Graduation date: 1974

The response of Canada milkvetch (Astragalus canadensis var. mortonii) to range and forest improvement practices was studied on a stand of mixed-coniferous forest which was clear -cut and burned in 1963 and 1964, respectively. The field studies were conducted on the Hall Ranch of the Eastern Oregon Experiment Station during the summers of 1968, 1969, and 1970. Canada milkvetch, which was virtually absent at the time of treatment, became one of the most important herbaceous species. The cover, frequency, and density of this species rapidly increased from 1965 to 1967; thereafter, these parameters have decreased, even to the levels of 1965 in some cases. The influence of forest canopy and physical site factor s, viz., soil moisture, soil temperature, and hydrogen ion concentration of the soil were studied. Phenology of seedling, root systems, shoot and flower development, seed production and germination were investigated. Studies were also made on the effects of grazing as they influence flowering, plant height, yield and number s of plants. The population parameters which were studied included cover, frequency, and density. The effects of calcium, copper, and cobalt each alone and in all combinations were studied by growing plants in the greenhouse. In addition, nitrogen fixation and the effect of nitrogen upon root nodulation were examined. The environmental parameters that influence Canada milkvetch are soil moisture and temperature for root nodulation and soil moisture for pod ripening. Soil from areas dominated by Canada milkvetch has higher pH values than soils in the forest and lower values than soils dominated by introduced grass species. In the experimental area, the amount of organic materials on the soil can be correlated with the intensity of grazing. Canada milkvetch begins growth shortly after snow melts, flowers in late June and July, and pods ripen in August. Flowering may begin in early June and continue to September, but the ovaries of the flowers produced early or late abort, because pollination occur s only when a medium sized bumble bee (Bombus sp. ) is the most active. This is the only species which trips the flowers of Canada milkvetch.The greatest amount of damage to the reproductive potential of Canada milkvetch is done by a weevil (Apion sp. ) which lives within the developing pod. At least 50 percent of the pods were destroyed by this insect during the summers of 1968 and 1969. Untreated seeds germinate and produce seedlings at the rate of approximately five percent per month. The rate of germination can be greatly increased by moist heat, but the amount of hard seeds remaining decreases and the amount decayed seed increases. The effects of grazing on this species can be evaluated by plant height, dry weight yield per plant, total yield per unit area, and the number of blossoms per flower stalk. Cattle prefer the inflorescences, but graze the leaves and stems along with the associated species at approximately the same intensity of use. On the other hand, big cattle preferentially graze this species from the time it begins growth in early spring until the animals leave the area. Canada milkvetch was always more productive under a grazing regime of cattle only than under a regime of domestic plus wild animals. Because the vegetation of the experimental area is rather low in the successional hierarchy, rapid changes in the values of cover, frequency, and density have occurred. The importance of Canada milkvetch has steadily decreased since 1967 and the relative importance of grasses has increased. Calcium seems to be required for nutrition and nodulation rather than as an amendment to alter the pH of the soil. Low levels of copper and cobalt also increase growth. Further research is required to adequately define the effects of these elements alone and in combination. Perhaps the successional role of Canada milkvetch can be prolonged by adequate fertility. This research provides an example demonstrating that range and forestry improvement must be coordinated and management intensified in order to maximize the biological potential of a given area. / Graduation date: 1971

A conceptual model of the tidal flat system, emphasizing the sulfur cycle was presented. Measurements were made of the vertical distribution within tidal flat deposits of total aerobic and sulfate reducing bacteria, total sulfides, redox potential, volatile solids, and particle size. Variations in dissolved oxygen and free sulfides in the water overlying tidal flat deposits were monitored during a tidal cycle, and profiles within this overlying water obtained. An in situ benthic respirometer was used to measure the rate of free sulfide release to the overlying water. Laboratory experiments were designed to investigate the mechanism of sulfide production in tidal flat areas. Growth media were prepared from extracts of sediment and algae collected from tidal flats. Rates of sulfide production in these growth media by mixed cultures of anaerobic bacteria from the same areas were obtained. A mathematical model, based on the common Michaelis-Menton equation, was used to simulate the experiments. A comparison of the simulated and experimental results was presented. / Graduation date: 1972

Core samples from five sites in the Yaquina and Coos Estuary were assayed for vertical distribution of total sulfides, percent volatile solids, redox potential, particle size, total aerobic and sulfate reducing bacteria. Higher total sulfide levels were found at sites having more than four percent volatile solids, redox potential below -100 millivolt, and with more than 80 percent fine particles. Free sulfides and dissolved oxygen were found simultaneously in the water one cm. above the sediment at site 5 during monitoring. One mg./l or higher levels of free sulfides were found sometimes even at supersaturated levels of dissolved oxygen. Free sulfides were found at site 3 only when the surface was disturbed and not at all at site 1. Extract experiments were run to determine organic carbon utilization and sulfide production. Aerobically 61 to 73 percent of the total carbon was utilized. Anaerobically 41 to 74 percent at 25��C and 33 to 55 percent at 15��C was utilized. There was a higher percentage of utilization when sulfides were not produced. Organic carbon levels above 350 mg./l and sulfate levels above 800 mg./l were needed to produce sulfides. Only samples where the Eh dropped below 0 were any significant amounts of sulfides produced. High levels of sulfides appear to delay, but not to reduce the rate of sulfide production. / Graduation date: 1974