School of Geography - Theses
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ItemSpatial variation in benthic community structure in upland streams: the influence of fine sediment transport( 2000)Physical factors can play an important role in structuring plant and animal communities. Together with spatial variation in their magnitude, differences in species tolerances to these factors are thought to explain considerable variation in the structure of natural assemblages. This thesis examines spatial variation in fine sediment transport in upland streams, and the effects of this on the structure of benthic invertebrate assemblages in this system. I initially surveyed sediment transport rates (3 times) using box type bedload traps and the faunal assemblages (twice) on individual stones at 12 sites on 3 regulated and 3 unregulated streams in the upper reaches of the Acheron and Yarra catchments, which drain from the Great Dividing Range, southeastern Australia. This study region spans a geologic boundary, and includes areas of acid volcanics in the north, and granite and sandstone to the south. Sediment transport rates, which were measured only at low flow ranged from 5+2 to 821+115 g.day' (mean f 1 SE) at each site. Transport rates between the volcanic and granitic/sandstone catchments accounted for most of the variation between sites, and thus differences in transport rates between the two geologies approached 3 orders of magnitude. The flow diversion weirs on some of the streams were found to negate any differences in sediment transport rates between the two catchment types. Multivariate analysis of macroinvertebrate assemblages clearly distinguished between assemblages from sites in the volcanic and granitic areas. Overlaid on these differences was the effect of flow regulation, in which assemblages at regulated sites in both catchments converged toward one another in terms of overall assemblage structure. The composition of the assemblages at these regulated sites differed from unregulated sites in both catchment types. Notably, although multivariate techniques clearly established the above patterns of difference, commonly measured variables such as species richness, total abundance and the abundance of common taxa showed ambiguous patterns with respect to catchment geology. The multivariate analyses suggest that differences in community structure between granitic and volcanic streams are partly related to the effects of sediment transport. However, I was not able to demonstrate this to be the case. In a field experiment in which sediment transport was excluded across individual patches of the streambed at 6 of the unregulated study sites, no changes were observed in the fauna colonising these patches relative to controls in which sediment transport was maintained at natural levels. This was so in both the volcanic and granite catchments. Nevertheless, multivariate analyses again showed assemblages within the granite and volcanic catchments to differ in a similar fashion as observed in the original survey. In a set of artificial stream channels located adjacent to one of the study streams, changes in the benthic community were monitored in response to short-term and long-term sediment addition. These two experiments considered changes in sediment loads that might occur, in the short term as a result of small spates (a pulse disturbance), and in the long-term as a result of natural variation in sediment loads, or alternatively as a result of human impacts (a press disturbance). In both cases sediment addition caused only minor, but consistent changes in the benthic assemblage. In the case of disturbance caused by spates, it appears that changes in flow are the predominant mechanism disturbing the community during these events. Overall, these communities appear to be resistant to the effects of sediment transport. Presumably this resistance relies on the maintenance of suitable habitat, and thus sedimentation of rocky substrates would probably cause far greater changes than were detected here in response to sediment transport. It is possible that in the granite streams surveyed, the effects of sediment transport are to some degree mediated by the ability of animals to find refuge from sediment induced abrasion, perhaps by seeking shelter on the lee side of rocks, or in dead water zones where scour by sediment transport is minimised. Future research must concentrate on the physiological tolerance to sediment transport of these organisms, and whether behavioural adaptations allow stress to be minimised in heterogeneous stream reaches.
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ItemUrban road traffic noise and health( 2000)Some people say they are annoyed by traffic noise. There is rather a lot of evidence to show that where traffic noise is louder, more people say they are annoyed by it. On the basis of this sort of evidence, there is a consensus that road traffic noise causes annoyance. Traffic noise is also suspected of being dangerous to health: of making people ill; so ill they reach for painkillers or even visit a doctor to get medicine prescribed. The fundamental aim of this thesis is to find out whether this is happening in Melbourne. The available evidence contains anomalies: people seem to be healthy where noise is loudest. Even annoyance studies sometimes detect unexplained peaks of annoyance in quieter places; or a plateau of annoyance in high noise. However, the anomalies display a certain consistency. Traffic noise is orthodoxly measured by loudness. Several studies have found a peak of annoyance at around 60 decibels. The consistency of the anomalies suggests that some other physical characteristic of noise may be responsible for the anomalous responses. This thesis sets out to explore the urban soundscape in an attempt to find such a characteristic, and discovers the pattern of alternation of passby noise and background sound: passby patterns. The orthodox loudness measure is essentially a proxy for the daily average sound energy delivered to the ear by traffic. To define patterns requires taking this measure apart - splitting traffic noise into two sounds: the sound of passbys and the background sound. The definition builds up through the use of point source theory, observations in urban and rural environments, experiments with a typical sedan in isolated locations, and experimentation with techniques for the measurement of background sound generated by roads. The tools applied are ears, stopwatch and sound meter. The result is a set of techniques aimed to measure patterns of passby noise in urban environments. Application of these techniques at 102 randomly selected sites spread over 150km2 of urban environments detects passby patterns in Melbourne. By way of an example, the final stage of this investigation embeds pattern measurements within a small, orthodox study of the annoyance and health responses to traffic noise measured by decibels. The results are consistent with regular or rapidly alternating passby patterns being closely associated with annoyance and ill health. In particular, in relation to people who are sensitive to noise, it should no longer be assumed that peak distress at approximately 60dB(A) is anomalous. It may well be due to high levels of patterning of passby noise. The result requires confirmation, to be sure, but the evidence is sufficiently strong to suggest that traffic noise and patterns of passby noise, or something closely associated with them, are probably associated with health problems in Melbourne.
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ItemHolocene sea levels and related environmental changes in Anderson Inlet, Victoria, Australia( 2000)Anderson Inlet in south eastern Australia preserves marine sediments that were deposited facing the Southern Ocean during the Holocene. Data obtained from near surface sediment samples together with topographic data are used to investigate the geomorphology, stratigraphy, Holocene sea level changes and related physical environment in Anderson Inlet, Victoria, Australia. The Holocene strata in the Anderson Inlet area in Victoria can be stratigraphically divided into four units, Unit I, Unit II, Unit HI, and Unit IV. Unit I and Unit IV lack fossils and were deposited in non-marine, probably fluvial, environments. Unit E and Unit IE contain abundant foraminifers with molluscs, ostracods and bryozoans. Foraminiferal analysis suggests that Unit IE was deposited in a partially sheltered marine environment, while the high plankton content and relatively high diversity of benthic species in Unit E indicate that this unit was deposited in an open bay at water depths possibly less than 5 m. The faunal data are integrated with radiocarbon dates to arrive at the following Holocene palaeoenvironmental history in this area: 1. Low alluvial plain stage (10000-7000 yr BP); 2. Open bay environment stage (7000-5500 yr BP); 3. Partially sheltered marine environment stage (5500-4500 yr BP); 4. Alluvial plain and coastal lagoon environment stage (since about 4500 yr BP). Contrary to interpretations made elsewhere in south eastern Australia, evidence exists for multiple higher Holocene sea levels in this area. Evidence for two higher Holocene sea level events with one lower sea level event in between has been identified. The timing of these Holocene sea level fluctuations correlates with the deglaciation history of Antarctica and climatic changes inferred from the geological record of mountain glaciers and fossil plants. The evidence suggests that the Anderson Inlet area has been strongly influenced by cold water regimes from the Southern Ocean during the middle Holocene and that marked environmental changes have occurred in the area during the Holocene, associated with the sea level fluctuations. During the last interglacial when sea level was 6.55 m higher than present, the Anderson Inlet area was an open marine environment consisting of several smaller embayments. The shoreline during this time followed the coastal cliffs and bluffs. During the first higher Holocene sea level stage (ca.7000-6000 yr B.P.), sea level was 1.8 m higher than present, the area was also an open marine embayment. During the second higher Holocene sea level stage (ca.5500-4500 yr B.P.) when sea level was 0.5 m higher than present, a minor sand spit developed which partially restricted the marine * embayment. It is inferred that the higher sea levels are likely to have been eustatic events associated with the deglaciation of Antarctica during the Holocene. The modem barrier system of Anderson Inlet is made up of a complex of sand dunes built up in response to the Holocene sea level fluctuations, especially during regressive events since the middle Holocene. The sand dune system of Anderson Inlet is very similar to other coastal barrier systems in south eastern Australia that have built up during the Holocene.