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???.

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

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

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???.

Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 123-130).

No description available.

This thesis presents a combined modelling and observational study of an intermittently open and closed lake or lagoon (ICOLL) in south-eastern Australia. ICOLLs are a common, yet vulnerable type of estuary characterised by low freshwater inflow leading to a sand berm being formed across the entrance preventing oceanic flushing. The accumulation of nutrients during the closed phase, and the increased water residence time, can have detrimental effects on the estuary if the nutrient load cannot be assimilated. The general aim of this study was to develop a quantitative understanding of ecological processes in Intermittently Closed and Open Lakes or Lagoons (ICOLLs) through a combination of field work and ecological modelling. The field-based component of the studied was completed in Smiths Lake, NSW Australia. The field data shows that concentrations of NH3, NOx and Chlorophyll a in Smiths Lake gradually increases over time between the two studied opening events, before declining while the lake is open to the ocean. Phosphorus concentration is relatively low throughout both cycles. Of the 2 opening events, one was long (~ 3.5 months) and one was short (~3 weeks). Initially ammonia concentrations following this short open period were 2-4 times higher than the initial values from the previous 2 closures. The reduced open phase also resulted in more persistent stratification. The observations show that the duration of the open/closed phases will influence the physiochemical characteristics of the water column. A spatially resolved, eleven-box ecological model was developed for Smiths Lake. The process descriptions in the ecological model are based on a combination of physical and physiological limits to the processes of nutrient uptake, light capture by phytoplankton and predator/prey interactions. An inverse model is used to calculate mixing coefficients from salinity observations. When compared to field data, the ecological model obtains fits for salinity, nitrogen, phosphorus, chlorophyll a and zooplankton that are within 1.5 standard deviations of the mean of the field data. Simulations show that nutrient limitation (nitrogen and phosphorus) is the dominant factor limiting growth of the autotrophs during both the open and closed phases of the lake. The model is characterised by strong oscillations in phytoplankton and zooplankton abundance,typical of predator-prey cycles. A sensitivity analysis was completed using a simplified 1-box configuration, coupled with the existing ecological model. When small perturbations in the initial conditions of DIN, phytoplankton and zooplankton are implemented, the standard deviations of the state variables strongly attract to a declining oscillation, showing the variation between runs decreasing with time. The most sensitive parameters in the model were the feeding efficiency of small and large zooplankton, and the mortality of epiphytes and small zooplankton which all had normalised sensitivities of 1.28, 1.11, 1.01 and 1.05 respectively for a 10% change in parameter value. The non-linearity of the model is illustrated by increasing the percentage change of the parameter. For a 25% change in feeding efficiency of small and large zooplankton, the normalised sensitivity increased to 1.28 and 1.15 respectively, and for a 50% change, they increased further to 1.78 and 1.35 respectively. The ecological state variables were also sensitive to increased catchment loads and depths. The modelled system switches from seagrass dominated to algal dominated at loads over 10?? the current loads, with increased plankton biomass and suspended solids shading the seagrass. The spatially resolved ecological model is run for a variety of open/closed cycles to assess the impact of various opening regimes on the model state variables. The results indicate that Smiths Lake is capable of assimilating its current nutrient loads without persistent phytoplankton blooms or a decrease in seagrass biomass. When catchment loads are increased by 10?? or the duration of the lake open/closed cycle is increased there is a corresponding increase in seagrass biomass. In contrast, small and large phytoplankton both increase in biomass as the duration of the open phase increases. Small and large phytoplankton growth is generally limited by phosphorus, and seagrass growth is limited by nitrogen under normal catchment loads. Due to the shallow depths and low phytoplankton biomass, seagrass only becomes light limited when the nutrient and suspended solids loads are increased 10??. This switch to light limitation only decreases the biomass for short periods.

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

This thesis presents a combined modelling and observational study of an intermittently open and closed lake or lagoon (ICOLL) in south-eastern Australia. ICOLLs are a common, yet vulnerable type of estuary characterised by low freshwater inflow leading to a sand berm being formed across the entrance preventing oceanic flushing. The accumulation of nutrients during the closed phase, and the increased water residence time, can have detrimental effects on the estuary if the nutrient load cannot be assimilated. The general aim of this study was to develop a quantitative understanding of ecological processes in Intermittently Closed and Open Lakes or Lagoons (ICOLLs) through a combination of field work and ecological modelling. The field-based component of the studied was completed in Smiths Lake, NSW Australia. The field data shows that concentrations of NH3, NOx and Chlorophyll a in Smiths Lake gradually increases over time between the two studied opening events, before declining while the lake is open to the ocean. Phosphorus concentration is relatively low throughout both cycles. Of the 2 opening events, one was long (~ 3.5 months) and one was short (~3 weeks). Initially ammonia concentrations following this short open period were 2-4 times higher than the initial values from the previous 2 closures. The reduced open phase also resulted in more persistent stratification. The observations show that the duration of the open/closed phases will influence the physiochemical characteristics of the water column. A spatially resolved, eleven-box ecological model was developed for Smiths Lake. The process descriptions in the ecological model are based on a combination of physical and physiological limits to the processes of nutrient uptake, light capture by phytoplankton and predator/prey interactions. An inverse model is used to calculate mixing coefficients from salinity observations. When compared to field data, the ecological model obtains fits for salinity, nitrogen, phosphorus, chlorophyll a and zooplankton that are within 1.5 standard deviations of the mean of the field data. Simulations show that nutrient limitation (nitrogen and phosphorus) is the dominant factor limiting growth of the autotrophs during both the open and closed phases of the lake. The model is characterised by strong oscillations in phytoplankton and zooplankton abundance,typical of predator-prey cycles. A sensitivity analysis was completed using a simplified 1-box configuration, coupled with the existing ecological model. When small perturbations in the initial conditions of DIN, phytoplankton and zooplankton are implemented, the standard deviations of the state variables strongly attract to a declining oscillation, showing the variation between runs decreasing with time. The most sensitive parameters in the model were the feeding efficiency of small and large zooplankton, and the mortality of epiphytes and small zooplankton which all had normalised sensitivities of 1.28, 1.11, 1.01 and 1.05 respectively for a 10% change in parameter value. The non-linearity of the model is illustrated by increasing the percentage change of the parameter. For a 25% change in feeding efficiency of small and large zooplankton, the normalised sensitivity increased to 1.28 and 1.15 respectively, and for a 50% change, they increased further to 1.78 and 1.35 respectively. The ecological state variables were also sensitive to increased catchment loads and depths. The modelled system switches from seagrass dominated to algal dominated at loads over 10?? the current loads, with increased plankton biomass and suspended solids shading the seagrass. The spatially resolved ecological model is run for a variety of open/closed cycles to assess the impact of various opening regimes on the model state variables. The results indicate that Smiths Lake is capable of assimilating its current nutrient loads without persistent phytoplankton blooms or a decrease in seagrass biomass. When catchment loads are increased by 10?? or the duration of the lake open/closed cycle is increased there is a corresponding increase in seagrass biomass. In contrast, small and large phytoplankton both increase in biomass as the duration of the open phase increases. Small and large phytoplankton growth is generally limited by phosphorus, and seagrass growth is limited by nitrogen under normal catchment loads. Due to the shallow depths and low phytoplankton biomass, seagrass only becomes light limited when the nutrient and suspended solids loads are increased 10??. This switch to light limitation only decreases the biomass for short periods.