A general decrease in populations of waders on the Ythan estuary, Aberdeenshire, has coincided with an increased biomass of green algae on the intertidal mudflats. It was hypothesised that the reduction of bird numbers was due to the impact of macroalgal mats. The main objective of this study was to test the above hypothesis by investigating the impact of macroalgal mats on aspects of the behavioural ecology of waders, principally on their dispersion, diet and foraging behaviour. Redshank (<I>Tringa totanus</I> L.), curlew (<I>Numenius arquata</I> L.), oystercatcher (<I>Haematopus ostralegus</I> L.), bar-tailed godwit (<I>Limosa lapponica</I> L.) and dunlin (<I>Calidris alpina</I> L.; for study of dispersion only) were chosen for study. To test this hypothesis, wader counts on different estuary sections, pellet and dropping analysis, direct observations on foraging, visual and photographic estimations of weed cover, and invertebrate data were assessed in the context of the energetics of waders and their prey described in the literature. Foraging behaviour was examined on weed-covered and weed-free sediments in natural sites and in field-manipulated plots. Weed cover below 25% (biomass <1 kg fresh weight/ m<SUP>2</SUP>) did not adversely influence the foraging of redshank, curlew, oystercatcher and bar-tailed godwit. However, weed cover >50% (biomass > 3 kg fresh weight/ m<SUP>2</SUP>) negatively affected the foraging of redshank, curlew and bar-tailed godwit but did not consistently affect oystercatcher. Redshank that fed on weed-covered areas had a reduced numerical food intake rate when compared to the birds on weed-free areas. During peak weed cover on the estuary, redshank on weeded areas had a 35.8% lower gross energy intake rate than those on weed-free areas.

Graduation date: 1984

Graduation date: 1980 / The printing on pages with "Explanation of Figures" is very light. Best scan available.

Macroalgal blooms are increasing world-wide and have negative effects on benthic invertebrates and sediments. These include loss of species diversity and development of hostile sediment environments. This thesis considers ecological effects of Ulva lactuca L., and its mechanical removal on benthic invertebrates and sediments in Avon-Heathcote Estuary, New Zealand. Benthic communities comprised 34 species from 12 groups recorded from seven sites during seasonal general surveys. Dominant groups at each site were Gastropoda and Bivalvia. The most abundant species were Austrovenus stutchburyi, Micrelenchus tenebrosus and Amphibola crenata. Community composition varied significantly between sites, and there were significant site-specific differences in abundances of most species between winter and summer. U. lactuca had the greatest seasonal variation. Several species correlated with U. lactuca biomass, and the strength of correlation for different species varied between sites. There were seasonal changes in sediment physico-chemical variables between sites with greatest change in the silt/clay fraction. The sediment variables silt/clay fraction, dissolved oxygen and temperature correlated with seasonal changes of patterns in benthic community assemblages. A similar study was carried out by Bressington in 2003. In both studies, Bivalvia and Gastropoda were the most abundant groups, with Gastropoda having a higher, and Bivalvia a lower, proportion in the present study compared with 2003. Summer communities were significantly different between the two studies. Compared with 2003 there were higher percentages of sediment pore water and volatile solids present in 2005. Experimental removal of U. lactuca was conducted by mechanical broom at two sites: an open, exposed central sand flat, and McCormacks Bay, a shallow, sheltered mud flat. Removing U. lactuca had several immediate effects. These included a significant decrease in abundance of mobile epifauna (Micrelenchus tenebrosus and Zeacumantus subcarinatus) and an increase in abundance of infauna, including Arthritica bifurca and Austrovenus stutchburyi. There was no effect of U. lactuca removal on Austrovenus stutchburyi condition and 46 days following removal, invertebrate abundances approached pre-removal levels at each site. U. lactuca removal also caused short-term increases in dissolved oxygen and temperature of pore water. The greatest visual impact of removing U. lactuca was to sediments in McCormacks Bay from trampling. It was concluded that the variables having the greatest effect on seasonal species distribution and abundance at each site were temperature and sediment grain size. Differences between the present study and the study in 2003 were due to differences in sampling procedure mainly due to the two different quadrat sizes. Greater accuracy in representing long-term changes in ecosystems would be achieved by using standard sampling protocols. Removal of U. lactuca by mechanical broom was effective and had low impact on benthic invertebrates and physico-chemical variables, but it should be used only in sandy habitats because of severe disturbance to soft-sediment environments. Options for management and control of U. lactuca in Avon-Heathcote Estuary are discussed.

Master of Science / Investigations of fluvial and estuarine sediments have indicated stormwater is an important source of heavy metals to Port Jackson estuary and high concentrations of these sedimentary contaminants are a threat to the healthy functioning of the estuarine ecosystem. Stormwater remediation devices have been installed in stormwater channels entering the estuary, however these devices are mainly for removing gross pollutants and are ineffective in removing heavy metals from stormwater. A thorough characterisation of heavy metal inputs and behaviour has been undertaken by sampling, analysing and modelling heavy metals in stormwater entering Port Jackson estuary to provide a rigorous data base for future remediation efforts. A conceptual model of transport and fate of heavy metals in stormwater entering Port Jackson estuary has also been developed to identify heavy metals, subcatchments and flow regimes requiring remediation, and to assist in designing remediation devices for optimum removal of heavy metals from stormwater. Modelling of stormwater using the Model for Urban Stormwater Improvement Conceptualisation (MUSIC) indicated that the average annual discharge of stormwater from the Port Jackson catchment was 215,307 ML. Average annual loadings of arsenic, cadmium, chromium, copper, nickel, lead and zinc in stormwater discharging to Port Jackson estuary were 0.8, 0.5, 1.7, 3.2, 1.1, 3.6 and 17.7 tonnes per year, although comparison to other studies in the catchment suggests these values may be underestimations of actual loadings by 1.3 to 10 times. The proportion of heavy metals discharged under low-flow conditions (<5mm of rainfall in 24 hours), medium-flow conditions (between 5 and 50mm in 24 hours), and high-flow conditions (>50 mm of rainfall in 24 hours) was 6.5%, 62.5% and 31%, respectively. The conceptual model indicates stormwater loadings of copper, lead and zinc pose a risk to the health of riverine and estuarine ecosystems in the catchment and these metals should be targeted for remediation. Stormwater channels which should be prioritised for remediation include the channels entering southern embayments west of Darling Harbour; Duck, Parramatta and Lane Cove Rivers; and the channels and rivers entering Neutral, Long and Sugarloaf Bays. Stormwater loadings of lead are predominantly associated with suspended particulates, whereas loadings of copper and zinc are equally partitioned between dissolved and particulate phases. Stormwater remediation strategies should target both dissolved and particulate phases to ensure effective removal of copper, lead and zinc. Research suggests heavy metals in stormwater discharged to the estuary under high-flow conditions are rapidly exported seaward and bypass the estuary. Preliminary research also suggests that under medium-flow conditions, particulate heavy metals bypass the embayments of Port Jackson and are deposited in the main channel. Once deposited in the main channel, particulate heavy metals are likely to be remobilised and removed from the estuary through multiple phases of resuspension. Although further research is required in this area, this preliminary research suggests remediation should target low-flow conditions. The findings of the current research could be used to identify appropriate remediation strategies for dissolved and particulate phase heavy metals in stormwater discharging to Port Jackson estuary. However, in designing stormwater remediation devices, consideration should also be given to the range of contaminants that may be present in stormwater entering Port Jackson estuary (including suspended solids, nutrients, pesticides and organics).

Thesis (Ph. D. - Renewable Natural Resources)--University of Arizona, 1989. / Includes bibliographical references (leaves 188-193).

Thesis (Ph.D.) OGI School of Science & Engineering at OHSU, November 2007. / Includes bibliographical references.

Thesis (M.Sc.)--University of Melbourne, 1992. / Typescript (photocopy). Bibliography: leaves 110-115.

Thesis (Ph.D.) -- University of Adelaide, 1976. / Includes bibliographical references (p.166-167).

Thesis (M.S. in environmental science)--Washington State University, August 2008. / Includes bibliographical references (p. 42-45).