Dissertations / Theses on the topic 'Moreton Bay (Queensland)'

Estuaries can be considered as vital natural resources and are unique ecosystems at the interface between terrestrial and marine environments. The increase of population density centred on these coastal features and associated anthropogenic activities such as trade, industry, agriculture and recreation can adversely affect these sensitive environments. The Pumicestone Passage, located in northern Moreton Bay, Australia, is one such estuarine environment where there are concerns about degradation of water quality resulting from rapid land use change. These changes are both immediate to the Passage and within its wider catchment. Of notable concern are the outbreaks of Lyngbya (a toxic blue-green algae) in the Passage itself and near its interface with Deception Bay to the south. Other factors of concern are increased suspended and dissolved loads, and maintenance of ecosystem integrity. In this study, numerical modelling, graphical methods and water surface elevation and current velocity parameter calculations are used to describe hydrological processes in the Pumicestone Passage. A hydrodynamic model is developed using the modelling software SMS and RMA2 as a foundation for future hydrodynamic and water quality modelling. In addition, observed data are used to interpret general hydrodynamic behaviour in the passage, and determine various parameters for use in model development and calibration. Tidal prediction is also discussed and used for model calibration. To support the modelling and for preliminary interpretation of hydrodynamic processes within the Passage, measurements were made in the field of (a) water surface elevation variation at 17 sites; (b) tidal current velocities in four of the tributary creeks and at the northern boundary; (c) volumetric flow rates at two cross-sections within the Passage; and (d) cross-sectional bathymetry at sites where tidal current velocities were measured in the creeks. In general, examination of the observational data reveals a number of important processes in the Pumicestone Passage. Almost all sites within Pumicestone Passage and its tributaries are flood dominant indicating that tidal storage and bottom friction effects are significant. Mesotidal ranges occur at sites close to the southern boundary of the passage, however, bottom friction greatly reduces the tidal response at the remaining sites which results in microtidal ranges. The influence of both the southern and northern tides can be seen in the deformation of tidal waveforms in the central passage. Extensive intertidal areas at and inside the northern inlet to the Passage markedly reduce tidal ranges in the northern estuary and its tributary creeks. Issues involved in hydrodynamic model development and performance are discussed. Overall, model results for the southern estuary have satisfactory correlation with observed data whereas model results for the northern estuary are less satisfactory. In addition, water surface elevation variation model results are generally more accurate than tidal current velocity model results. Reasons for the differences between model and observed values are considered and possible solutions given. Factors discussed relate to boundary condition locations, resolution of bathymetric and geographical data, mesh development methods and parameter assignment.

Estuaries can be considered as vital natural resources and are unique ecosystems at the interface between terrestrial and marine environments. The increase of population density centred on these coastal features and associated anthropogenic activities such as trade, industry, agriculture and recreation can adversely affect these sensitive environments. The Pumicestone Passage, located in northern Moreton Bay, Australia, is one such estuarine environment where there are concerns about degradation of water quality resulting from rapid land use change. These changes are both immediate to the Passage and within its wider catchment. Of notable concern are the outbreaks of Lyngbya (a toxic blue-green algae) in the Passage itself and near its interface with Deception Bay to the south. Other factors of concern are increased suspended and dissolved loads, and maintenance of ecosystem integrity. In this study, numerical modelling, graphical methods and water surface elevation and current velocity parameter calculations are used to describe hydrological processes in the Pumicestone Passage. A hydrodynamic model is developed using the modelling software SMS and RMA2 as a foundation for future hydrodynamic and water quality modelling. In addition, observed data are used to interpret general hydrodynamic behaviour in the passage, and determine various parameters for use in model development and calibration. Tidal prediction is also discussed and used for model calibration. To support the modelling and for preliminary interpretation of hydrodynamic processes within the Passage, measurements were made in the field of (a) water surface elevation variation at 17 sites; (b) tidal current velocities in four of the tributary creeks and at the northern boundary; (c) volumetric flow rates at two cross-sections within the Passage; and (d) cross-sectional bathymetry at sites where tidal current velocities were measured in the creeks. In general, examination of the observational data reveals a number of important processes in the Pumicestone Passage. Almost all sites within Pumicestone Passage and its tributaries are flood dominant indicating that tidal storage and bottom friction effects are significant. Mesotidal ranges occur at sites close to the southern boundary of the passage, however, bottom friction greatly reduces the tidal response at the remaining sites which results in microtidal ranges. The influence of both the southern and northern tides can be seen in the deformation of tidal waveforms in the central passage. Extensive intertidal areas at and inside the northern inlet to the Passage markedly reduce tidal ranges in the northern estuary and its tributary creeks. Issues involved in hydrodynamic model development and performance are discussed. Overall, model results for the southern estuary have satisfactory correlation with observed data whereas model results for the northern estuary are less satisfactory. In addition, water surface elevation variation model results are generally more accurate than tidal current velocity model results. Reasons for the differences between model and observed values are considered and possible solutions given. Factors discussed relate to boundary condition locations, resolution of bathymetric and geographical data, mesh development methods and parameter assignment.

This project was the first comprehensive assessment of heavy metals to be conducted in the sediments of Northern Moreton Bay since the 1970s and found that shipping and shipping related activities contributed significantly to the level of sediment contamination in the area. The study was also used to develop and test new methods of assessing heavy metal sediment quality.

In eastern Australia, the changing patterns of mangrove distribution are commonly associated with upslope encroachment into saltmarsh. This phenomenon could be related to climate change (e.g., change in precipitation, CO2 concentrations and sea-levels), as the result of human-induced changes in the wetlands and surrounding landscape or due to the interactions among these factors. This thesis investigated relationships between rainfall, land use, and landscape structure of selected wetlands in northern Moreton Bay, Queensland, Australia, from 1972 to 2004 over multiple temporal and spatial scales through the use of remote sensing, GIS and statistical analysis. To assess the relationship between rainfall patterns and the spatial distribution of mangrove forests, periods of relatively consistent rainfall patterns were identied using the non-parametric Pettitt-Mann-Whitney-Statistic and the Cumulative Sum technique. This identied change-points in rainfall distribution and these were then used to dene the temporal periods over which changes to mangrove area were assessed. Historical aerial photos acquired in 1972, 1990 (the year at which there was the most signicant change-point in rainfall pattern), and 2004 were used to estimate the rate of expansion (gross increase) and change (net increase) in mangrove spatial extent for the wetter period (pre- 1990) and the drier period (post-1990). A signicant positive relationship was demonstrated between rainfall variables and landward mangrove expansion and change. A Mangrove-Saltmarsh Interface (MSI) index, which was developed as part of this research, quantied the relative opportunity for mangrove to expand into saltmarshes, based on the shared boundary between them. There was a consistent relationship between the MSI and mangrove spatial change. The data for land use/cover at three spatial scales (catchment, sub-catchment, and land adjacent to wetlands) were derived from Landsat satellite imagery for the study area. Also, human population density has been estimated. The results indicate that the contribution of landscape variables (land use/cover and population density) to spatial changes in mangroves at each spatial scale is aected by the rainfall pattern. The research also indicates that there is a scale-dependent eect of development on mangrove spatial change during wet and dry periods. Integrating the results of investigations into the relation between the mangrovesaltmarsh interface (MSI) index, rainfall, land use/cover and population density with mangrove spatial change led to comprehensive models explaining mangrove expansion and change in the inter-tidal coastal wetland of northern Moreton Bay, south east Queensland. Findings from this study have shown that a combination of natural and anthropogenic factors was related to the distribution of mangroves at the local scale. Rainfall appeared to be the driving variable in the system and determined the scale at which anthropogenic factors aect mangroves. The contribution of environmental variables to mangrove spatial dynamics varied in accordance with rainfall patterns. With the potential effects of climate change on rainfall and sea-levels, this research has identied an approach that may assist in identifying and understanding related changes in mangrove distribution.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

The population of the of Sillago maculata in Moreton Bay is abundant and has been fished in large quantities since 1952 by trawling. It is of fundamenta1 interest to determine how this species tolerates high levels of exploitation and remains viable. This was approached in three aspects: genetic characteristics,biological status, and whiting fisheries.

Studies of the fate of discarded by-catch were carried out in the Moreton bay prawn trawl fishery between September 1983 and March 1986. These studies included the determination of the by-catch biomass composition as well as assessing the impact of trawling and various handling times on damage and mortality. The by-catch was made up of 52% Crustacea, 15% elasmobranchs, 8% bony fish, 18% chinoderms, 3% cephalopods and 4% debris by weight. Portunus elagicus represented ~5% of the crustacean biomass and the lpheids nearly 2.0% and of the bony fishes, cardinal fish represented 13%, winter whiting 7%, and the flounders 5%. Trawls in the Moreton Bay fishery are of about 60 minutes and require about 20 minutes to sort. Times recorded for trawl duration and sorting over the study averaged 65.8 min and 23.3 min respectively. Short term survival of Crustacea was high (about 85%) while survival of bony fish was variable (from 20% to 70%) between species. A study of the fate of discards that reach the seabed showed that Portunus pelagicus was the most common scavenger attracted to the bait; followed by several bony fish species (11%) (n = 881 photographs). No prawns were observed at any of the simulated discards. A comparative analysis of foregut contents of sand crabs (P. pelagicus) and two penaeid prawn species (Penaeus plebejus and P. esculentus) showed that the penaeid prawns do not feed on trawler discards but that the sand crabs had fed on discards (33% by weight of their diet). Measurement of the rate of scavenging of discards on the seabed showed that benthic scavengers were capable of consuming up to 11 g of fish per linear metre per hour. The amounts of discards that are partitioned to seabirds (terns, gulls and cormorants) and dolphins were estimated. Fish discarded into the sea separate into a floating group and a sinking group. Size was important in determining the fate of discarded fish. Fish less than 100 mm long were generally taken by terns and gulls (34% of fish biomass) while fish greater than 100 mm were eaten by dolphins (41%) and cormorants (15%) and the rest (10%) sink. Crustacea were not eaten by birds or dolphins. A model of the fate of prawn trawler discards is presented with quantified pathways. This model shows that energy, in the form of discarded fish, is removed from the Moreton Bay benthic biomass and some ecological consequences of this are discussed. This study has shown that earlier models and ideas about the fate of prawn trawler discards are misleading.

This thesis details the geomorphology and timing of the mid-Holocene fossil reef at Cleveland Point, Moreton Bay, Queensland. This research presents the first subsurface data from percussion cores through the reef. Results reveal that Cleveland Point reef initiated quickly after rising seas flooded their foundations 7300 years ago. The reef remained in a "catch-up" growth mode from 7300 to 5700 years ago before reef accretion ceased. Age data suggests that the termination of the reef occurred 5700 years ago and coincided with a hypothesized lowering of sea-level and a possible change in terrigenous sediment distribution in Moreton Bay.

Southern Moreton Bay and the adjacent continental shelf have provided a natural laboratory in which to describe the sedimentology, sequence stratigraphy and coastal evolutionary processes of a wave dominated coastline. Sequence stratigraphy has become a routine tool for Earth Scientists in the exploration of hydrocarbons and as such detailed studies in Quaternary depositional environments are required to provide analogues for ancient environments. The Quaternary has a well documented sea level curve which when used in combination with high resolution seismic, drill core and age dating provides the opportunity to derive accurate and detailed depositional scenarios for various stages of sea level. This study has established that the southeast Queensland coastal prism is an example of a relatively sediment deficient margin as a result of the low gradient of the regional topography and the low flow rate of the fluvial systems. This differs dramatically from the regions from which most of the generic sequence stratigraphic models have been derived (ie. North America and Europe) where major fluvial systems have high flow rates and generally greater topographic relief Consequently the system described herein provides an important variation on generic sequence stratigraphic models, particularly in the way a fluvial system responds to periods of low sea level. The incision of the Logan/ Albert fluvial system has been mapped across the coastal plain, through the lagoon and under the inner to mid-continental shelf The valley system is not apparent on the outer shelf. This may primarily be a function of stream gradient. The gradient of the incised valley is approximately 0.002 in the coastal prism, the outer continental however is 10 km wide with a relief of 2-3m giving a gradient of 0.00025. This essentially flat shelf area coincides with the lack of incision on the shelf. As a result of the extremely low gradient of the outer shelf area in combination with potentially hard substrate and a reduced stream power during glacial periods, it is unlikely that the Logan/ Albert Pluvial system incised to the shelf edge. The low gradient of the exposed shelf during glacial lowstands therefore resulted in the over extension and loss of stream power (reduced transport efficiency) of the Logan/ Albert flu vial system. The area that is now the outer shelf was most likely occupied by single channel thick shelf bypass channels (c.f. Posamentier & Allen, 1999) or became a low-lying fluvial shallow braid plain. The earliest deposition in the study took place on the continental shelf where three sequences are dominated by transgressive and lowstand systems tracts with highstand systems tracts not being readily recognised. On the coastal plain, three sequences have been cored and described in the Logan River incised valley. These sequences have been dated in this study at 40,000 yBP and 25,000 yBP and <18,000 yBP. This indicates that the Logan River incised valley can be classified as a compound valley fill (Zaitlin et al., 1994) characteristic of a relatively long lived fluvial system. Seismic mapping indicates the first sediment deposited in southern Moreton Bay was related to late lowstand conditions (the first onset of sea level rise and the creation of sufficient accommodation to allow for vertical aggradation), and was confined to the thalwegs of incised valleys. Seismic geometries suggest that deposition took place in fluvial point bars and therefore is most likely gravel and sand dominated. A transgressive surface separates these late lowstand fluvial sediments from an early to mid transgressive unit. The early to mid transgressive sediments are characterised by h high amplitude continuous reflectors and are generally confined within the wider valley walls, and are interpreted to have been deposited in a quiet estuarine setting. After the peak at 1OOkyBP, sea level began to fall into the next glacial maximum at 18 kyBP. This sea level fall was not smooth and was punctuated by a number of transgressive-regressive cycles. As a consequence three force regressive shelf perched early lowstand wedges are recognised on the continental shelf adjacent to the southern Moreton Bay area. These wedges have been grouped as sequence set C and represent subsequences within the overall early lowstand or falling stage systems tract associated with this punctuated falling sea level. Each of these sequences represent coastal plain deposits forming at a stage of sediment by-pass in the upper reaches of the fluvial valleys creating minor but significant sequence boundaries. The main sequence boundary GL is related to incision associated with the major sea level fall that peaked at 18 kyBP. This surface is heavily incised in places and formed at stages associated with each of the falls on the overall falling sea level limb. In the southern area incision related to the paleo-Logan Albert system is up to 60m on the coastal plain. The Logan system has re-inherited its main valley, and its position is structurally controlled. The Logan River valley was reincised as a result of the low sea level associated with the last glacial maximum. The first sediments to be deposited within this reincised valley were fluvial point-bar polymictic gravels and quartz-lithic sands these are interbedded with overbank deposits of mud and silt. These deposits are confined to the valley thalwegs. The earliest dateable material sampled by drilling in this study was 13,650 ±60 yBP (Beta-104824), indicating late·lowstand to early transgressive conditions based on the sea level curve of Chappell, et al., (1996). The transgressive surface, which overlies these deposits, is contained within the valleys and is recognised by the input of estuarine fauna! assemblages although the quartz-lithic and poorly sorted character of the sediments does not change. This in turn is overlain by high amplitude, concordant reflectors that are generally confined to the greater valley walls and shown to be laminated estuarine mud by drilling. The thickness and fine grained nature of these sediments in conjunction with a rapid sediment accumulation rate (approximately 11mm/year) indicates extensive creation of accommodation space consistent with the rapid transgression experienced on the east Australian coast at this time (up to 2.5rn/100years. A major tidal ravinement surface overlies the laminated muds of the early to mid transgressive phase of sedimentation. This surface is highly erosive and recognised as an abrupt change from laminated mud to clean well-sorted fine grained quartzose sand in conjunction with a shelly lag. The tidal ravinement surface is often coincident with the GL sequence boundary in areas. The last glacial transgression reached its peak at 6.5kyBP at approximately - 1.5 m higher than present. Age dating shells from a depth of 3m near the +2.5m contour on the coastal plain gave an Amino Acid Ratio consistent with an age of approximately 6.5kyBP. The Pimpama Coastal Plain was inundated at the peak of the transgression. Sediments form a depth of 6.lm were dated at 4780±60 yBP (WK-7663) in LR#3. Given the thickness of the overlying section it is apparent that the area was still part of an active flood tidal delta setting well beyond the peak of sea level at 6.5 kyBP. This is in keeping with a relatively rapid drop in sea level after 3000 yBP as is proposed by Flood, (1983), and explains the virtual absence of regressive bayhead delta sands on the coastal plain. The H4 seismic unit represents the current highstand since the peak of the late transgression. It is generally confined to the immediate vicinity of the Logan River bayhead delta and constrained geographically to the Redland Bay area. Where seen the unit downlaps onto the maximum flooding surface. This maximum flooding surface is coincident with the bay floor in most places of the northern area as a result of insufficient sediment supply to the area either from the Logan River or the tidal delta. When sea level fell by 1-l.5m approximately 3000 yBP, the tidal prism of the southern Moreton Bay area was dramatically decreased. As a result the efficient ancestral tidal inlet which had developed between the newly developed South Stradbroke barrier Island and North Stradbroke Island had to narrow and become shallower until it eventually closed. This period of closure allowed for the tidal circulation to decrease in the vicinity of southern Moreton Bay to virtually nil as that area became a tidal null point for tides now entering the area from South Passage (to the north) and the Nerang Inlet (to the south). Consequently the only sediment input was mud, silt and quartz-lithic sand supplied by the Logan and Pimpama Rivers. As a result, the sand shoals of the previous flood tide delta became relict and colonised by mangroves forming intra-to supra tidal · islands. This situation remained until 1898 when the sea broke through at Jumpinpin. Once this had occurred the regional tidal null point was shifted to become coincident with an area closer to the mouth of the present Logan River and the northern end of Canaipa Passage. The main effect was the scouring of previously inactive abandoned tidal channels to become the deep channels of present day. Quartzose marine sand has entered into the lagoon by a distance of nearly 9krn since 1898.

Moreton Bay, in South East Queensland, Australia, is a Ramsar wetland of international significance. A decline of the bay’s ecosystem health has been primarily attributed to sediments and nutrients from catchment sources. The Healthy Country (HC) project, a Queensland Government funded ‘proof of concept’ initiative, is dedicated to reducing rural diffuse sediments and nutrients entering waterways and ultimately Moreton Bay. Three focal catchments, Blackfellow Creek, Knapp Creek and the Upper Bremer River, were selected to trial rehabilitation techniques for the region. Sediment budgets for these focal catchments, developed using catchment scale modelling (SedNet), indicated gully erosion dominates the supply of sediment in Knapp Creek (90%) and the Upper Bremer River (80%) whereas erosion from cultivated soils is the primary sediment source in Blackfellow Creek (40%). These sediment budgets, that include predictions of both the spatial sources of sediment and the primary erosion processes, form a series of hypotheses in each focal catchment that are tested in this thesis. Fallout-radionuclide activity concentrations (137Cs and 210Pbex) of in-stream sediment sampled in each focal catchment were used in conjunction with regional source data to test hypotheses pertaining to dominant erosion processes, specifically the relative sediment contributions from surface and subsoil (gully and channel bank) sources. Distribution modelling results indicated subsoil erosion processes dominate the supply of sediment in both Knapp Creek (100%) and the Upper Bremer River (100%). In Blackfellow Creek, the similarity of cultivated (surface) and subsoil source fallout-radionuclide activity concentrations resulted in no discrimination between these sources that were modelled in combination to contribute >90% of sediments. Importantly there was no discrimination between gully and channel bank erosion sources in Knapp Creek and the Upper Bremer River.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

This thesis examines the relationship between the underlying ecological values of wetlands and the economic values they produce. The importance of the roles that wetlands play is now well recognised yet losses continue at a global level. It is argued that one cause of wetland loss is a lack of awareness of the values of these systems due to inadequate information of the nexus between ecological functions and economic values. For example, the off-site, indirect benefits provided by wetlands have largely been ignored. This has led to an undervaluation of these ecosystems. The integration of ecological and economic values requires incorporating differing types of information and systems of value derived from differing disciplines with differing paradigms. To understand the differing disciplinary perspectives the thesis explores the ecological functions of wetlands and the economic goods and services that they provide. The functions and benefits of wetlands are linked at the ecological-economic interface. A consensus on the definition of ecological value could not be discerned within the discipline of ecology. Thus, a definition and index of ecological value is developed to demonstrate the attributes of coastal and wetland systems that provide for instrumental human benefits. These attributes include productivity, the ability to provide habitats for dependent species and the diversity of species and organisation they support. However, ecological information is not presently available to operationalise the index. The ability of economic techniques to capture this ecological value is then investigated. Three approaches for assessing non-market values (direct linkage models, revealed preference and stated preference models) are reviewed with respect to their ability to capture ecological value. An alternative biophysical approach, namely energy analysis, is also considered. The review suggests that it may be possible to measure ecological value using the contingent valuation method. The role of information in preference formation and willingness to pay bids is then investigated along with a number of other issues that need to be resolved before using the contingent valuation method. The wetlands of the case study area, Moreton Bay, Australia exhibit both ecological and economic values. The wetlands contribute approximately one-third of primary productivity in the Bay, provide habitat for a wide range of dependent species (including internationally recognised migratory wader birds) and have a diverse fauna with a relatively large number of endemic species. Economic values of the wetlands include both direct and indirect use values (for example, fishing, recreation, water quality improvements and storm buffering) and non-use values. Non-use values include the value in preserving the environment for future generations (bequest value) and the existence of vulnerable animals such as turtles and dugongs, which one may never expect to see. If consumers are willing to pay to preserve these animals, this is also a valid economic value. The economic technique of contingent valuation is tested to determine if it is possible to capture ecological value by providing respondents, selected by random sample, to a survey with the relevant information. A case study is undertaken in Moreton Bay to determine respondents' willingness to pay to improve water quality and hence protect the wetlands. To test the effects of differing types information, four different versions of the survey were sent to four groups of 500 respondents. Case A provided no extra information so it could be used as a control. Case B included information about the ecological values of the wetlands of Moreton Bay. Case C provided information about the economic use values of the wetlands in the Bay including direct and indirect use. Case D provided information about the non-use values of endangered species resident in the Bay that are dependent on the wetlands. The results indicate that the provision of different types of information influences willingness to pay. However, willingness to pay when provided with ecological information is not significantly different from willingness to pay when provided with other information. As it was not possible from the research undertaken to state that the contingent valuation method can capture ecological value, an alternative approach is proposed to link ecological and economic values. It is argued that ecologists and economists need to develop common aims and scales of assessment. Further, communication between the two disciplines can be enhanced through the use of agreed indicator terms. Through an iterative approach it should then be possible to understand the linkages between changes in indicators of ecosystem values and indicators of economic value.

Three approaches for assessing non-market values (direct linkage models, revealed preference and stated preference models) are reviewed with respect to their ability to capture ecological value. An alternative biophysical approach, namely energy analysis, is also considered. The review suggests that it may be possible to measure ecological value using the contingent valuation method. The role of information in preference formation and willingness to pay bids is then investigated along with a number of other issues that need to be resolved before using the contingent valuation method. The wetlands of the case study area, Moreton Bay, Australia exhibit both ecological and economic values. The wetlands contribute approximately one-third of primary productivity in the Bay, provide habitat for a wide range of dependent species (including internationally recognised migratory wader birds) and have a diverse fauna with a relatively large number of endemic species. Economic values of the wetlands include both direct and indirect use values (for example, fishing, recreation, water quality improvements and storm buffering) and non-use values. Non-use values include the value in preserving the environment for future generations (bequest value) and the existence of vulnerable animals such as turtles and dugongs, which one may never expect to see. If consumers are willing to pay to preserve these animals, this is also a valid economic value. The economic technique of contingent valuation is tested to determine if it is possible to capture ecological value by providing respondents, selected by random sample, to a survey with the relevant information. A case study is undertaken in Moreton Bay to determine respondents' willingness to pay to improve water quality and hence protect the wetlands. To test the effects of differing types information, four different versions of the survey were sent to four groups of 500 respondents. Case A provided no extra information so it could be used as a control. Case B included information about the ecological values of the wetlands of Moreton Bay. Case C provided information about the economic use values of the wetlands in the Bay including direct and indirect use. Case D provided information about the non-use values of endangered species resident in the Bay that are dependent on the wetlands. The results indicate that the provision of different types of information influences willingness to pay. However, willingness to pay when provided with ecological information is not significantly different from willingness to pay when provided with other information. As it was not possible from the research undertaken to state that the contingent valuation method can capture ecological value, an alternative approach is proposed to link ecological and economic values. It is argued that ecologists and economists need to develop common aims and scales of assessment. Further, communication between the two disciplines can be enhanced through the use of agreed indicator terms. Through an iterative approach it should then be possible to understand the linkages between changes in indicators of ecosystem values and indicators of economic value.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Full Text

The coastal region influences many aspects of our lives, including our economy, our quality of life and our safety and security. Many large cities in Australia are located along estuaries and coasts. As a consequence of the growing human population, most coastal areas throughout Australia are now facing threats of over urbanisation, and industrialisation, resulting in significant impacts on the coastal aquatic environments. Additional challenges may also come from more frequent severe flooding resulting to climate changes, which could degrade the environment even further and more rapidly. Sediment accumulation and transport in estuaries and coastal bays is one of major issues, not only impacting on the maintenance of navigation channel but also resulting in ecological problems. For several decades, a large number of investigations of sediment transport have been conducted in Australia, which them mostly addressing conditions of the sediment delivered to the estuary within the dry season. However, a limited number of researches have been done in great detail, focusing on the hydrodynamic and sediment transport in the wet season. In recent years, with the development of computing and satellite technologies, the study on the hydrodynamic and sediment transport has allowed studies to be conducted on large spatial and temporal scales. Additionally, this has meant it is now easier to investigate the event-driven behaviour severe flooding events.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

The koala (Phascolarctos cinereus) is an iconic Australian marsupial that is under threat of extinction across two thirds of its range, with populations recently listed as ‘endangered’ in Queensland (QLD), New South Wales (NSW) and the Australian Capital Territory (ACT). Many risk factors have been implicated in the koala population decline, including habitat loss, vehicle collisions, dog attack and infectious diseases such as chlamydiosis and koala immune deficiency syndrome caused by koala retrovirus (KoRV). Trypanosomes are blood-borne protozoan parasites that can infect all classes of mammals and are known to cause serious disease in humans and domestic livestock worldwide. Recent studies have identified numerous Trypanosoma species in a range of Australian marsupials, including the koala which is known to harbour up to six species in either single or mixed infections: Trypanosoma irwini, Trypanosoma gilletti, Trypanosoma copemani, Trypanosoma vegrandis, Trypanosoma noyesi and Trypanosoma sp. AB-2017. Importantly, preliminary data from analyses of hospitalised koalas in QLD suggest that trypanosome infections (alone or with concurrent diseases) may adversely affect koala health and survival. Whilst a large number of studies have been conducted on chlamydia and KoRV, there is still a paucity of research investigating the prevalence, diversity and clinical impact of trypanosomes in koalas. In particular, there is a dearth of research comprising random, representative samples from various wild koala populations across Australia, including more stable populations from South Australia (SA). This descriptive cross-sectional study utilised nested PCR, targeting partial fragments of the nuclear 18S ribosomal RNA (18S rRNA) gene, to screen blood samples from wild-caught koalas for the presence of trypanosomes. Samples were randomly collected from koalas belonging to two distinct wild populations; Moreton Bay, Queensland (QLD) (n= 72) and Mount Lofty, South Australia (SA) (n= 89). The overall prevalence of Trypanosoma in both populations was 47.2% (76/161; 95% CI: 39.3-55.2%). The prevalence of trypanosomes in koalas from Moreton Bay was 80.6% (58/72; 95% CI: 69.5-88.9%), whereas the prevalence in koalas from Mount Lofty was significantly lower: 20.2% (18/89; 95% CI: 12.4-30.1%). Sanger sequencing of PCR positive products was performed and phylogenetic analysis conducted on the partial 18S rDNA fragments obtained. A total of 35 Trypanosoma isolates from Moreton Bay koalas were identified as Trypanosoma irwini (n= 36), with intra-specific genetic variations ranging from 0% - 2.99%. Remaining QLD isolates (n=16) were identified as Trypanosoma gilletti, with genetic distances ranging from 0% - 1.20%. These results are similar to findings from previous studies of hospitalised koalas from QLD and NSW. All Trypanosoma isolates from the Mount Lofty population (n = 18) formed a unique, highly diverse clade within the Trypanosoma cruzi clade of trypanosomes. These novel sequences displayed a high genetic variation amongst each other (genetic distances = 0% - 7.04%) and from their most closely related species (T. sp 1EA-2008) (genetic distances = 1.90% - 7.73%). To the best of the author’s knowledge, this is the first report of trypanosomes in koalas from SA. The unique phylogenetic position of the isolates identified, associated with a relatively high genetic distance from their most closely related known Trypanosoma sp., suggests that they may potentially represent novel Trypanosoma spp.. Further analyses of full-length 18S sequences and additional loci are required to confirm this finding and reliably delimit the species. Sanger sequencing of seven PCR positive isolates from Moreton Bay koalas revealed mixed chromatograms and were excluded from phylogenetic analyses. Further analyses using next-generation metabarcoding are required to identify and characterise mixed trypanosome infections in all positive samples detected in the present study, particularly those that produced mixed Sanger sequencing chromatograms. This study provides valuable novel baseline data which will contribute to the growing knowledge base of Australian trypanosomes, and future studies on the potential impact of Trypanosoma spp. (with and without concurrent infectious diseases) on the health and conservation of koalas.

This research uses a series of deep (1.5 - 5m) sediment cores collected from sub-tidal sediment of a shallow bay to explore connectivity within the catchment to coast continuum. Specifically, this thesis investigates; 1) the variation in sediment yield of a coastal catchment subject to widespread land-use changes, 2) Historical trends in metal pollution in a shallow bay and the relative impact of a high magnitude flood. 3) Relative changes in coastal primary production and algal community shifts following land use changes in the adjacent catchment, and 4) Long-term climatic features of the eastern Australian subtropics preserved in these fluvial marine sediments. Together, the research presented demonstrates value of these sedimentary archives in providing novel insights into the dynamics of the coastal zone. Coasts receive mineral and organic sediments transported from catchments through run-off. Mineral sediments provide important physical habitats for intertidal and marine organisms, while nutrients support high rates of productivity contributing to the ecological and functional diversity of coastal oceans. The modification of coastal catchments through human disturbance including; land clearing, impoundment construction, industrial, urban and agricultural activities have significantly altered the flux of this material from drainage basins to coastal environments. In many cases these changes have had negative impacts on valuable coastal ecosystems.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

The increasing world population and with it the increased pressure on food production are likely to challenge the availability of quality fresh water resources in the near future. To compound the looming water crisis, caused by an increased demand for water available for agricultural production, the quality of our fresh water resources is also likely to suffer from the consequences of increased population pressure, i.e. urbanization of land and growth of industries, and food production, i.e. agricultural use of land. Moreton Bay, South East Queensland, Australia, is listed under the United Nations Convention on Wetlands and is also a declared Marine Park. The Moreton Bay area, however, is already one of the five fastest growing urban areas in the developed world. Prognoses about future population growth and urban and industrial development in the area, have hence given rise to growing concerns about the future water quality in this international environmentally important area. Therefore the aim of the current study was to investigate the fate of nutrients in freshwater streams in the Moreton Bay area in order to gain a better understanding of nutrient pathways in aquatic systems and assist in refining the National Water Quality Management Strategy to provide better management of our waterways. To achieve this, the effects of land use on water quality were determined at 22 study sites in the Brisbane River Catchment. Within the catchment five main types of land use were identified, including urban, rural residential, cropping, grazing and mixed types of land use. Water quality was sampled during three seasons: the pre-wet (October - November), wet (December - March) and dry (April - August) season. Nitrogen and phosphorus concentrations in ambient stream water varied significantly spatially, i.e. types of land use, and temporally, i.e. seasons. At some sites, during certain times of the year, nutrient concentrations were found to exceed the range recommended by the Australian Water Quality guidelines. Nutrient concentrations were particular high in urban areas, especially during the dry season. It was also found that the 15N signatures in aquatic plants, i.e epipelic algae, correlated strongly with in-stream nitrogen concentrations. The large variability of in-stream nutrient concentrations, and the related changes in nitrogen isotopic signatures in aquatic plants, made it obvious to suggest that changes in land use may significantly impact on water quality in the catchment. Other changes in land use, for example riparian vegetation clearing, are also commonly observed in areas under urban, industry and/or agricultural growth pressure. This is of particular concern, given riparian vegetation is important not only in controlling nutrient and other organic matter input into streams, but also in regulating light levels for in-stream primary production. Previously riparian zones have been shown to be a prime source of carbon and energy for aquatic food webs in some studies, whereas other studies suggested the main driver of food webs is in-stream primary production. The current study used stable isotope analysis track carbon and nitrogen pathways through aquatic systems and determine the primary source of carbon and energy in aquatic food webs. Despite large spatial and temporal variability of 13C, aquatic consumers were closely tracking the carbon isotope signatures of plants and it was suggested that epilithic and epipelic algae are the main contributors to the carbon and energy budget of aquatic consumers.In realizing this importance of algae in aquatic systems, the next step in this study was to examine the relative importance of light and nutrient availability to periphyton and the effects of changes of these variables on plant biomass and primary production. In an in-situ experiment the levels of light and nutrients available to periphyton, were altered. Although nutrients and light may have colimited standing crop of periphyton, other variables were clearly limited by light. Parallel to this experiment on periphyton, the nutrient availability to Vallisneria spp. was experimentally altered to investigate the effects of changes in nutrient availability and nutrient limitation on other aquatic plants. The biomass of this submerged macrophyte increased three-fold in nitrogen and phosphorus sufficient areas over nutrient limited treatments. The physiological response, i.e. changes in concentrations of amino acids, of periphyton to changes in environmental conditions was also investigated on a large scale, i.e. spatial and temporal variability of amino acids, and a local scale, i.e. amino acid changes in artificially altered light and nutrient availability. This response was of particular interest in this study, as it was previously shown that physiological changes in plants impact on the quality of plants as food for consumers. The physiological changes in aquatic plants could thus provide an important link between nutrient input into streams (e.g. from terrestrial sources), impacts on aquatic plants (e.g.. nutrient uptake and physiological responses in plants) and effects on aquatic consumers (e.g. changes in food quality of plants and therefore impacts on biomass, growth and overall health of aquatic consumers).

The increasing world population and with it the increased pressure on food production are likely to challenge the availability of quality fresh water resources in the near future. To compound the looming water crisis, caused by an increased demand for water available for agricultural production, the quality of our fresh water resources is also likely to suffer from the consequences of increased population pressure, i.e. urbanization of land and growth of industries, and food production, i.e. agricultural use of land. Moreton Bay, South East Queensland, Australia, is listed under the United Nations Convention on Wetlands and is also a declared Marine Park. The Moreton Bay area, however, is already one of the five fastest growing urban areas in the developed world. Prognoses about future population growth and urban and industrial development in the area, have hence given rise to growing concerns about the future water quality in this international environmentally important area. Therefore the aim of the current study was to investigate the fate of nutrients in freshwater streams in the Moreton Bay area in order to gain a better understanding of nutrient pathways in aquatic systems and assist in refining the National Water Quality Management Strategy to provide better management of our waterways. To achieve this, the effects of land use on water quality were determined at 22 study sites in the Brisbane River Catchment. Within the catchment five main types of land use were identified, including urban, rural residential, cropping, grazing and mixed types of land use. Water quality was sampled during three seasons: the pre-wet (October - November), wet (December - March) and dry (April - August) season. Nitrogen and phosphorus concentrations in ambient stream water varied significantly spatially, i.e. types of land use, and temporally, i.e. seasons. At some sites, during certain times of the year, nutrient concentrations were found to exceed the range recommended by the Australian Water Quality guidelines. Nutrient concentrations were particular high in urban areas, especially during the dry season. It was also found that the 15N signatures in aquatic plants, i.e epipelic algae, correlated strongly with in-stream nitrogen concentrations. The large variability of in-stream nutrient concentrations, and the related changes in nitrogen isotopic signatures in aquatic plants, made it obvious to suggest that changes in land use may significantly impact on water quality in the catchment. Other changes in land use, for example riparian vegetation clearing, are also commonly observed in areas under urban, industry and/or agricultural growth pressure. This is of particular concern, given riparian vegetation is important not only in controlling nutrient and other organic matter input into streams, but also in regulating light levels for in-stream primary production. Previously riparian zones have been shown to be a prime source of carbon and energy for aquatic food webs in some studies, whereas other studies suggested the main driver of food webs is in-stream primary production. The current study used stable isotope analysis track carbon and nitrogen pathways through aquatic systems and determine the primary source of carbon and energy in aquatic food webs. Despite large spatial and temporal variability of 13C, aquatic consumers were closely tracking the carbon isotope signatures of plants and it was suggested that epilithic and epipelic algae are the main contributors to the carbon and energy budget of aquatic consumers.In realizing this importance of algae in aquatic systems, the next step in this study was to examine the relative importance of light and nutrient availability to periphyton and the effects of changes of these variables on plant biomass and primary production. In an in-situ experiment the levels of light and nutrients available to periphyton, were altered. Although nutrients and light may have colimited standing crop of periphyton, other variables were clearly limited by light. Parallel to this experiment on periphyton, the nutrient availability to Vallisneria spp. was experimentally altered to investigate the effects of changes in nutrient availability and nutrient limitation on other aquatic plants. The biomass of this submerged macrophyte increased three-fold in nitrogen and phosphorus sufficient areas over nutrient limited treatments. The physiological response, i.e. changes in concentrations of amino acids, of periphyton to changes in environmental conditions was also investigated on a large scale, i.e. spatial and temporal variability of amino acids, and a local scale, i.e. amino acid changes in artificially altered light and nutrient availability. This response was of particular interest in this study, as it was previously shown that physiological changes in plants impact on the quality of plants as food for consumers. The physiological changes in aquatic plants could thus provide an important link between nutrient input into streams (e.g. from terrestrial sources), impacts on aquatic plants (e.g.. nutrient uptake and physiological responses in plants) and effects on aquatic consumers (e.g. changes in food quality of plants and therefore impacts on biomass, growth and overall health of aquatic consumers).
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Australian School of Environmental Studies
Full Text

In response to the growing human population and our impacts on the environment, we design programs for conservation, restoration and rehabilitation to maintain and enhance productivity, biodiversity and ecosystem resilience. To ensure the greatest return on these investments, there is an implicit requirement for identifying disproportionately important species, processes and landscape elements as high-value targets for conservation and management. Connectivity is commonly favoured among these because it provides the mechanism for reserves to sustain exploited populations beyond their borders, and is critical for reversing the ecosystem impacts of trophic cascades. Few studies have, however, adopted a quantitative approach, like that provided under the framework of landscape ecology, to assess the value of connectivity in conservation. This conceptual division between the disciplines of conservation and landscape ecology must be bridged to better enable the management of healthy functioning ecosystems. This thesis used heterogeneous reef seascapes in Moreton Bay, Queensland, as a model system for examining the potential effect of connectivity in enhancing marine reserve performance. A positive effect of connectivity between mangroves and coral reefs was demonstrated on the performance of marine reserves, including effects on productivity, biodiversity and ecological resilience. This finding represents a critical first step in improving the integration of spatial ecology into conservation planning and assessment. This thesis then illustrates how neighbouring mangroves and seagrasses can exert different effects on reef fish assemblages and extends our current understanding of the role of connectivity in reef seascapes. This indicates that a reef’s position in the seascape can be of greater significance to the composition of fish assemblages than its area or complexity, and highlights the shortcoming of management approaches that focus solely on representing measures of habitat area, complexity or condition. Herbivorous fish play a key role in coral reef seascapes; by removing algae they promote coral growth and recruitment, and help to increase resilience. Habitat connectivity and reserves both influence herbivore populations and herbivory, but their potential interactive effects have not been investigated. This thesis shows that these factors can indeed exert synergistic effects on herbivore populations and grazing intensity, which facilitated a trophic cascade that reduced algal cover and enhanced coral recruitment and reef resilience on protected reefs near mangroves. The effects of reserves and connectivity for fish assemblages were then extended from a local to regional scale, by examining the potential interaction of these factors across the tropical and subtropical waters of the western Pacific Ocean. Habitat connectivity improved the performance of marine reserves across this region, and spatial variation in the magnitude of the reserve-connectivity interaction was explained by differences among reserves in the area of mangroves and reef, duration of mangrove inundation and distance to rivers. The management of heterogeneous inshore reef ecosystems as functional seascape units is considered necessary for preservation of critical interconnections among habitats. By further improving our understanding of seascape ecology and connectivity, and by incorporating this field of research into conservation ecology and decisionmaking, we should expect to have greater success in restoring exploited populations and the functioning of ecosystems.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

In estuarine and other aquatic systems, it is possible for water to transport locally produced carbon (food) across habitat boundaries, and provide nutrition for animals remote from the carbon source. In estuarine and marine systems, early work examining the movement of carbon from saltmarsh habitats in the USA suggested that carbon may move large distances from inshore to offshore environments. Upon closer examination, however, evidence did not support this paradigm of large-scale carbon movement, referred to as the outwelling hypothesis, in some estuaries. Physical characteristics of estuaries in which large-scale carbon movement did not occur, such as restricted access to the sea, were proposed as a possible explanation, and for these estuaries, movement of carbon among estuarine habitats was considered more likely. A mosaic of saltmarsh and mangrove habitats dominate the subtropical barrier estuary of southern Moreton Bay, Queensland, but there have been no studies that examine the movement of carbon among habitats within this system. Previous studies that examine the movement of carbon have mostly been done in saltmarshes in the northern hemisphere or in tropical mangrove systems. Different vegetation and tidal regimes in temperate marshes of the northern hemisphere preclude generalisations of carbon movement to tropical and subtropical systems. Our understanding of carbon movement in tropical systems may extend to subtropical waters, but the saltmarsh-mangrove mosaic in the subtropics distinguishes them from their tropical counterparts. The mosaic of saltmarsh and mangrove habitats among the barrier islands of southern Moreton Bay thus provide a unique opportunity to examine the small-scale movement of carbon among adjacent habitats in a subtropical system. Stable isotopes of carbon have been used successfully to trace the transfer of carbon from autotrophs to consumers at a range of spatial scales. This method is able to distinguish among carbon sources where autotrophs have different ratios of 13C/12C, and consumers take on the ratio of their food source. The success of stable isotopes in clarifying food web processes, however, depends on isotope ratios changing in predictable ways as elements are processed. As isotope ratios may be influenced by changes in productivity, and differences in nutrient source, they may vary across small and large spatial scales that may confound interpretation of food web processes. In this study I measured small and large-scale spatial variability of three estuarine autotrophs (the saltmarsh grass, Sporobolus virginicus, the seagrass Zostera capricorni and the algal community epiphytic on Z. capricorni) and showed the small-scale spatial variability to be negligible and insufficient to preclude the use of carbon and nitrogen isotopes in food web studies. Large-scale variability was more pronounced and may be useful for spatial correlation of food webs for more mobile species. The small-scale homogeneity and clearly distinguished isotope ratios of the dominant autotrophs in adjacent saltmarsh and mangrove habitats in southeast Queensland are therefore ideally suited to the study of small-scale carbon movement between adjacent habitats. Carbon isotopes of estuarine invertebrates were used to estimate the movement of particulate carbon between adjacent saltmarsh and mangroves at the tens-of-metre scale. Carbon isotope values of two crab species (Parasesarma erythrodactyla and Australoplax tridentata) and two snail species (Salinator solida and Ophicardelus quoyi) in saltmarsh closely match those of the saltmarsh grass, and suggest that the movement and assimilation of carbon occurs at a scale much smaller than has previously been examined. In mangroves, the results of this study indicate that microphytobenthos with some contribution of mangrove carbon is the most likely food source for P. erythrodactyla and A. tridentata, although contribution of carbon from saltmarsh is also possible. Under this latter scenario, carbon movement in mangroves would be considered to occur at a scale larger than that in saltmarsh habitat. A study that examined the movement and assimilation of carbon by crabs and an estuarine slug (Onchidina australis) at a finer resolution (i.e. metres) supported the original findings and indicated that the movement and assimilation of carbon occurs 5 - 8 m either side of the saltmarsh-mangrove interface. At this small-scale, the movement and subsequent foraging of crabs among habitats, the movement of particulate carbon among habitats, or a combination of crab and particulate carbon movement are three alternative models that provide plausible explanations for the pattern in carbon isotope values of crabs. Crab movement among these habitats was measured using an array of pitfall traps perpendicular to the saltmarsh-mangrove interface. To test for carbon movement, samples of detritus were collected at 2 m intervals across this same interface and the carbon isotopes analysed. For the majority of crabs (up to 90% for both species), movement up or down the shore was less than 1 m from the place of initial capture. Thus, crab movement cannot explain the trend in carbon isotope values of crabs. The pattern in detrital isotope values was similar to that of crabs and indicates that the movement of particulate carbon across the saltmarsh-mangrove interface is the most likely explanation for crab isotope ratios. Sources of carbon for estuarine invertebrates can also depend on the size of the saltmarsh patches. Examination of the movement and assimilation of carbon by crabs in saltmarsh patches of different sizes adjacent to mangroves indicates that saltmarshes less than 0.3 ha in area are subsidised by the import of allochthonous carbon, most likely from mangroves. These findings contribute substantially to our understanding of the food web value of estuarine habitats and provide an important link between landscape and food web ecology. They also have important implications for determining the conservation value of estuarine habitats with respect to their functional (food web) value. The scale-dependent sampling used in this thesis also provides important evidence for the fine-scale movement of estuarine carbon that has not previously been examined.

In estuarine and other aquatic systems, it is possible for water to transport locally produced carbon (food) across habitat boundaries, and provide nutrition for animals remote from the carbon source. In estuarine and marine systems, early work examining the movement of carbon from saltmarsh habitats in the USA suggested that carbon may move large distances from inshore to offshore environments. Upon closer examination, however, evidence did not support this paradigm of large-scale carbon movement, referred to as the outwelling hypothesis, in some estuaries. Physical characteristics of estuaries in which large-scale carbon movement did not occur, such as restricted access to the sea, were proposed as a possible explanation, and for these estuaries, movement of carbon among estuarine habitats was considered more likely. A mosaic of saltmarsh and mangrove habitats dominate the subtropical barrier estuary of southern Moreton Bay, Queensland, but there have been no studies that examine the movement of carbon among habitats within this system. Previous studies that examine the movement of carbon have mostly been done in saltmarshes in the northern hemisphere or in tropical mangrove systems. Different vegetation and tidal regimes in temperate marshes of the northern hemisphere preclude generalisations of carbon movement to tropical and subtropical systems. Our understanding of carbon movement in tropical systems may extend to subtropical waters, but the saltmarsh-mangrove mosaic in the subtropics distinguishes them from their tropical counterparts. The mosaic of saltmarsh and mangrove habitats among the barrier islands of southern Moreton Bay thus provide a unique opportunity to examine the small-scale movement of carbon among adjacent habitats in a subtropical system. Stable isotopes of carbon have been used successfully to trace the transfer of carbon from autotrophs to consumers at a range of spatial scales. This method is able to distinguish among carbon sources where autotrophs have different ratios of 13C/12C, and consumers take on the ratio of their food source. The success of stable isotopes in clarifying food web processes, however, depends on isotope ratios changing in predictable ways as elements are processed. As isotope ratios may be influenced by changes in productivity, and differences in nutrient source, they may vary across small and large spatial scales that may confound interpretation of food web processes. In this study I measured small and large-scale spatial variability of three estuarine autotrophs (the saltmarsh grass, Sporobolus virginicus, the seagrass Zostera capricorni and the algal community epiphytic on Z. capricorni) and showed the small-scale spatial variability to be negligible and insufficient to preclude the use of carbon and nitrogen isotopes in food web studies. Large-scale variability was more pronounced and may be useful for spatial correlation of food webs for more mobile species. The small-scale homogeneity and clearly distinguished isotope ratios of the dominant autotrophs in adjacent saltmarsh and mangrove habitats in southeast Queensland are therefore ideally suited to the study of small-scale carbon movement between adjacent habitats. Carbon isotopes of estuarine invertebrates were used to estimate the movement of particulate carbon between adjacent saltmarsh and mangroves at the tens-of-metre scale. Carbon isotope values of two crab species (Parasesarma erythrodactyla and Australoplax tridentata) and two snail species (Salinator solida and Ophicardelus quoyi) in saltmarsh closely match those of the saltmarsh grass, and suggest that the movement and assimilation of carbon occurs at a scale much smaller than has previously been examined. In mangroves, the results of this study indicate that microphytobenthos with some contribution of mangrove carbon is the most likely food source for P. erythrodactyla and A. tridentata, although contribution of carbon from saltmarsh is also possible. Under this latter scenario, carbon movement in mangroves would be considered to occur at a scale larger than that in saltmarsh habitat. A study that examined the movement and assimilation of carbon by crabs and an estuarine slug (Onchidina australis) at a finer resolution (i.e. metres) supported the original findings and indicated that the movement and assimilation of carbon occurs 5 - 8 m either side of the saltmarsh-mangrove interface. At this small-scale, the movement and subsequent foraging of crabs among habitats, the movement of particulate carbon among habitats, or a combination of crab and particulate carbon movement are three alternative models that provide plausible explanations for the pattern in carbon isotope values of crabs. Crab movement among these habitats was measured using an array of pitfall traps perpendicular to the saltmarsh-mangrove interface. To test for carbon movement, samples of detritus were collected at 2 m intervals across this same interface and the carbon isotopes analysed. For the majority of crabs (up to 90% for both species), movement up or down the shore was less than 1 m from the place of initial capture. Thus, crab movement cannot explain the trend in carbon isotope values of crabs. The pattern in detrital isotope values was similar to that of crabs and indicates that the movement of particulate carbon across the saltmarsh-mangrove interface is the most likely explanation for crab isotope ratios. Sources of carbon for estuarine invertebrates can also depend on the size of the saltmarsh patches. Examination of the movement and assimilation of carbon by crabs in saltmarsh patches of different sizes adjacent to mangroves indicates that saltmarshes less than 0.3 ha in area are subsidised by the import of allochthonous carbon, most likely from mangroves. These findings contribute substantially to our understanding of the food web value of estuarine habitats and provide an important link between landscape and food web ecology. They also have important implications for determining the conservation value of estuarine habitats with respect to their functional (food web) value. The scale-dependent sampling used in this thesis also provides important evidence for the fine-scale movement of estuarine carbon that has not previously been examined.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental and Applied Science
Full Text

Virtually all marine conservation planning and management models in place or proposed have in common the need for improved scientific rigour in identifying and characterising the marine habitats encompassed. An emerging central theme in the last few years has been the concept of representativeness, or representative systems of Marine Protected Areas (MPAs). The habitat classification and mapping needed to incorporate considerations of representativeness into MPA planning must logically be carried out at the same scale at which management occurs. Management of highly protected areas occurs almost exclusively at local scales or finer, independent of the reservation model or philosophy employed. Moreton Bay, on Australia’s east coast, was selected for studies at the local scale to map and classify macrobenthic habitats. In a site scale (1 km) trial for the major habitat classification study, remote underwater videography was used to map and characterise an unusual assemblage of epibenthic invertebrates on soft sediments. The assemblage included congregations of the comatulid crinoid Zygometra cf. Z. microdiscus (Bell) at densities up to 0.88 individuals.m-2, comparable to those found in coral reef habitats. There was no correlation between the distribution of this species and commonly used abiotic surrogates depth (6 – 18 m), sediment composition and residual current. This site scale trial is the first quantitative assessment of crinoid density and distribution in shallow water soft-sediment environments. The high densities found are significant in terms of the generally accepted picture of shallow-water crinoids as essentially reefal fauna. The findings highlight the conservation benefits of an inclusive approach to marine habitat survey and mapping. Assemblages such as the one described, although they may be of scientific and ecological significance, would have been overlooked by common approaches to marine conservation planning which emphasise highly productive or aesthetically appealing habitats. Most habitat mapping studies rely solely or in part on abiotic surrogates for patterns of biodiversity. The utility of abiotic variables in predicting biological distributions at the local scale (10 km) was tested. Habitat classifications of the same set of 41 sites based on 6 abiotic variables and abundances of 89 taxa and bioturbation indicators were compared using correlation, regression and ordination analyses. The concepts of false homogeneity and false heterogeneity were defined to describe types of errors associated with using abiotic surrogates to construct habitat maps. The best prediction by abiotic surrogates explained less than 30% of the pattern of biological similarity. Errors of false homogeneity were between 20 and 62%, depending on the methods of estimation. Predictive capability of abiotic surrogates at the taxon level was poor, with only 6% of taxon / surrogate correlations significant. These results have implications for the widespread use of abiotic surrogates in marine habitat mapping to plan for, or assess, representation in Marine Protected Areas. Abiotic factors did not discriminate sufficiently between different soft bottom communities to be a reliable basis for mapping. Habitat mapping for the design of Marine Protected Areas is critically affected by the scale of the source information. The relationship between biological similarity of macrobenthos and the distance between sites was investigated at both site and local scales, and for separate biotic groups. There was a significant negative correlation between similarity and distance, in that sites further apart were less similar than sites close together. The relationship, although significant, was quite weak at the site scale. Rank correlograms showed that similarity was high at scales of 10 km or less, and declined markedly with increasing distance. There was evidence of patchiness in the distributions of some biotic groups, especially seagrass and anthozoans, at scales less than 16 km. In other biotic groups there was an essentially monotonic decline in similarity with distance. The spatial agglomeration approach to habitat mapping was valid in the study area. Site spacing of less than 10 km was necessary to capture important components of biological similarity. Site spacing of less than 2.5 km did not appear to be warranted. Macrobenthic habitat types were classified and mapped at 78 sites spaced 5 km apart. The area mapped was about 2,400 km2 and extended from estuarine shallow subtidal waters to offshore areas to the 50 m isobath. Nine habitat types were recognised, with only one on hard substrate. The habitat mapping characterised several habitat types not previously described in the area and located deepwater algal and soft coral reefs not previously reported. Seagrass beds were encountered in several locations where their occurrence was either unknown or had not previously been quantified. The representation of the derived habitat types within an existing marine protected area was assessed. Only two habitat types were represented in highly protected zones, with less than 3% of each included The study represents the most spatially comprehensive survey of epibenthos undertaken in Moreton Bay, with over 40,000 m2 surveyed. Derived habitat maps provide a robust basis for inclusion of representative examples of all habitat types in marine protected area planning in and adjacent to Moreton Bay. The utility of video data to conduct a low-cost habitat survey over a comparatively large area was also demonstrated. The method used has potentially wide application for the survey and design of marine protected areas.

Virtually all marine conservation planning and management models in place or proposed have in common the need for improved scientific rigour in identifying and characterising the marine habitats encompassed. An emerging central theme in the last few years has been the concept of representativeness, or representative systems of Marine Protected Areas (MPAs). The habitat classification and mapping needed to incorporate considerations of representativeness into MPA planning must logically be carried out at the same scale at which management occurs. Management of highly protected areas occurs almost exclusively at local scales or finer, independent of the reservation model or philosophy employed. Moreton Bay, on Australia’s east coast, was selected for studies at the local scale to map and classify macrobenthic habitats. In a site scale (1 km) trial for the major habitat classification study, remote underwater videography was used to map and characterise an unusual assemblage of epibenthic invertebrates on soft sediments. The assemblage included congregations of the comatulid crinoid Zygometra cf. Z. microdiscus (Bell) at densities up to 0.88 individuals.m-2, comparable to those found in coral reef habitats. There was no correlation between the distribution of this species and commonly used abiotic surrogates depth (6 – 18 m), sediment composition and residual current. This site scale trial is the first quantitative assessment of crinoid density and distribution in shallow water soft-sediment environments. The high densities found are significant in terms of the generally accepted picture of shallow-water crinoids as essentially reefal fauna. The findings highlight the conservation benefits of an inclusive approach to marine habitat survey and mapping. Assemblages such as the one described, although they may be of scientific and ecological significance, would have been overlooked by common approaches to marine conservation planning which emphasise highly productive or aesthetically appealing habitats. Most habitat mapping studies rely solely or in part on abiotic surrogates for patterns of biodiversity. The utility of abiotic variables in predicting biological distributions at the local scale (10 km) was tested. Habitat classifications of the same set of 41 sites based on 6 abiotic variables and abundances of 89 taxa and bioturbation indicators were compared using correlation, regression and ordination analyses. The concepts of false homogeneity and false heterogeneity were defined to describe types of errors associated with using abiotic surrogates to construct habitat maps. The best prediction by abiotic surrogates explained less than 30% of the pattern of biological similarity. Errors of false homogeneity were between 20 and 62%, depending on the methods of estimation. Predictive capability of abiotic surrogates at the taxon level was poor, with only 6% of taxon / surrogate correlations significant. These results have implications for the widespread use of abiotic surrogates in marine habitat mapping to plan for, or assess, representation in Marine Protected Areas. Abiotic factors did not discriminate sufficiently between different soft bottom communities to be a reliable basis for mapping. Habitat mapping for the design of Marine Protected Areas is critically affected by the scale of the source information. The relationship between biological similarity of macrobenthos and the distance between sites was investigated at both site and local scales, and for separate biotic groups. There was a significant negative correlation between similarity and distance, in that sites further apart were less similar than sites close together. The relationship, although significant, was quite weak at the site scale. Rank correlograms showed that similarity was high at scales of 10 km or less, and declined markedly with increasing distance. There was evidence of patchiness in the distributions of some biotic groups, especially seagrass and anthozoans, at scales less than 16 km. In other biotic groups there was an essentially monotonic decline in similarity with distance. The spatial agglomeration approach to habitat mapping was valid in the study area. Site spacing of less than 10 km was necessary to capture important components of biological similarity. Site spacing of less than 2.5 km did not appear to be warranted. Macrobenthic habitat types were classified and mapped at 78 sites spaced 5 km apart. The area mapped was about 2,400 km2 and extended from estuarine shallow subtidal waters to offshore areas to the 50 m isobath. Nine habitat types were recognised, with only one on hard substrate. The habitat mapping characterised several habitat types not previously described in the area and located deepwater algal and soft coral reefs not previously reported. Seagrass beds were encountered in several locations where their occurrence was either unknown or had not previously been quantified. The representation of the derived habitat types within an existing marine protected area was assessed. Only two habitat types were represented in highly protected zones, with less than 3% of each included The study represents the most spatially comprehensive survey of epibenthos undertaken in Moreton Bay, with over 40,000 m2 surveyed. Derived habitat maps provide a robust basis for inclusion of representative examples of all habitat types in marine protected area planning in and adjacent to Moreton Bay. The utility of video data to conduct a low-cost habitat survey over a comparatively large area was also demonstrated. The method used has potentially wide application for the survey and design of marine protected areas.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental and Applied Science
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Several fringing coral reefs in Moreton Bay, Southeast Queensland, some 300 km south of the Great Barrier Reef (GBR), are set in a relatively high latitude, estuarine environment that is considered marginal for coral growth. Previous work indicated that these marginal reefs, as with many fringing reefs of the inner GBR, ceased accreting in the mid-Holocene. This research presents for the first time data from the subsurface profile of the mid-Holocene fossil reef at Wellington Point comprising U/Th dates of in situ and framework corals, and trace element analysis from the age constrained carbonate fragments. Based on trace element proxies the palaeo-water quality during reef accretion was reconstructed. Results demonstrate that the reef initiated more than 7,000 yr BP during the post glacial transgression, and the initiation progressed to the west as sea level rose. In situ micro-atolls indicate that sea level was at least 1 m above present mean sea level by 6,680 years ago. The reef remained in "catch-up" mode, with a seaward sloping upper surface, until it stopped aggrading abruptly at ca 6,000 yr BP; no lateral progradation occurred. Changes in sediment composition encountered in the cores suggest that after the laterite substrate was covered by the reef, most of the sediment was produced by the carbonate factory with minimal terrigenous influence. Rare earth element, Y and Ba proxies indicate that water quality during reef accretion was similar to oceanic waters, considered suitable for coral growth. A slight decline in water quality on the basis of increased Ba in the later stages of growth may be related to increased riverine input and partial closing up of the bay due to either tidal delta progradation, climatic change and/or slight sea level fall. The age data suggest that termination of reef growth coincided with a slight lowering of sea level, activation of ENSO and consequent increase in seasonality, lowering of temperatures and the constrictions to oceanic flushing. At the cessation of reef accretion the environmental conditions in the western Moreton Bay were changing from open marine to estuarine. The living coral community appears to be similar to the fossil community, but without the branching Acropora spp. that were more common in the fossil reef. In this marginal setting coral growth periods do not always correspond to periods of reef accretion due to insufficient coral abundance. Due to several environmental constraints modern coral growth is insufficient for reef growth. Based on these findings Moreton Bay may be unsuitable as a long term coral refuge for most species currently living in the GBR.

This study examines struggles over settlement exposures to environmental risk, and the ways socio-environmental legacies and commitments are problematised, challenged, transformed, or otherwise ‘unsettled’. Inquiry is directed to discursive and material processes that shape legacy exposures and risk commitments ‘in place’, yet remain relatively neglected in scholarship, policy, and planning. Drawing upon critical, constructivist, and conflict perspectives, especially within environmental sociology and the sociologies of risk and disaster, the study systematically addresses issues of power in the production and placement of risk, hazard, and exposure, and in related understanding of impacts, and response. Grounded in a qualitative methodology, a case approach and mixed methods are employed to identify and investigate three environmental risk controversies situated in the coastal, mainland Moreton Bay Region in Southeast Queensland, Australia. Methods used include the analysis of documentary and archival material, a household survey, and semi-structured interviews with self-selected residents who were survey respondents, and with purposively sampled community group representatives. The cases investigate, in turn, contentious settlement exposures related to the ‘encroachment’ of hazardous industries and a large chemical factory fire, catastrophic flooding and the manageability of flood risk, and the acceptable impacts of climate change adaptation itself. Analysis in each case was directed to the following: predominant problem and solution framing; critical attention to government roles in risk creation; issues of allocation and claims of tolerability, acceptability, and responsibility for risk acceptance; and related contestation and prospects for transformation. ‘Placing’ environmental risk controversies in this way supported consideration of the nature, significance, and limits of any related (symbolic or material) unsettling. The incidents, disasters, and disputes under study included challenges to the authority of technical and scientific knowledge, its appropriate application in local contexts, and the accessibility and acceptability of paths and processes for determining the stakes and commitments of settlement. Interpreted as cases of encroachment, fragmentation, and displacement, powerful risk commitments were argued to remain ‘out of frame’ in important ways. Enduring socio-institutional and politico-legal commitments to the accommodation, accumulation, and domestication of risk, hazard, and exposure were evident across the cases. The hazardous legacies of past land-use decisions, for instance, were identified but naturalised in ways that served to enable the advancement of certain trajectories, forms, and locations of development. It was argued that these ongoing risk commitments, and challenges to them, are best understood as inseparable from both local ‘risk landscapes’ and broader claims to the legitimate terms and bounds of governance, environment, and settlement.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
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The Pimpama estuarine plain in subtropical southeast Queensland is comprised of Quaternary sediments infilling older bedrock. These multilayered unconsolidated sediments have various depositional origins, and are highly heterogeneous. The plain is low-lying and the surface drainage is controlled by flood mitigation measures including tidal gates and channelised streams. The control of surface drainage potentially affects the shallow water table. This modification of hydrology has implications for future viability of agriculture and also the environmental health of waterways. Increased landscape modification and water management is likely in the coming years. The combination of sediment heterogeneity, low hydraulic gradients, and artificial drainage modification result in the plain being hydrogeologically complex. In order to understand hydrologic processes in this setting, a multi-disciplinary research programme was conducted which included a drilling program, overland electromagnetic induction and other geophysical surveys (downhole gamma log, electromagnetic induction and magnetic susceptibility) to initially establish the geologic framework. These surveys were followed by hydrogeochemical testing which includes for major and minor ions and also stable isotopes, and mineralogical analysis of drillhole material. Underlying basement rock occurs at up to 60 m depth. Unconsolidated gravel and sand deposits occur within incised paleo-valleys and are overlain by predominantly low-permeability fluvial sandy clays and estuarine and lagoonal muds. Fine-grained delta sands occur in the top 15 m of the sub-surface. Within the unconsolidated sediments, hydrodynamic trends clearly discriminated between upper unconfined and lower semi-confined aquifer systems. A comparison of surface water and shallow groundwater levels indicate limited interaction of groundwater and surface water. Hydrogeochemical analysis effectively distinguished between groundwater bodies, and also distinguished saline groundwater from seawater. Trends in major ion chemistry in the semi-confined system (particularly Na/Cl and Ca/Cl ratios) showed ion exchange accompanying saline intrusion. However, due to factors such as mineral dissolution, major ion chemistry does not clearly identify solute flux trends in the shallow aquifer system. Water stable isotope analysis (δ18O and δ2H) indicated the provenance of fresh and saline groundwater and also the relative importance of the principal hydrologic processes, i.e. evaporation and water uptake by plants. Groundwater exhibited a wide range in salinity, from very fresh to hypersaline. The formation of hypersaline groundwater was attributed largely to uptake of water by mangrove forests. Since mangrove forests were more extensive at the time of the Holocene maximum sea level (approximately 6,000 years ago) than at present, some of this groundwater may represent relict salinity from this earlier time. The relationship of relict salinity to low permeability sediments, particularly at intermediate depths, and their depositional history was examined. Vertical salinity gradients and hydrogeochemistry within these sediments varied according to position within the plain, suggesting deposition under various hydrological and sea level regimes. A preliminary investigation using analysis of stable sulfate isotopes (δ34S and δ18OSO4) was made. This study shows substantial potential for the application of this technique for quantification of solute flux and sulfur chemical transformations within settings such as this coastal plain. To establish shallow groundwater flow processes, a MODFLOW-based numerical model was used to inversely estimate aquifer parameters under various recharge scenarios. The model was designed to examine the relative importance of evapotranspiration and discharge to surface waters. However, largely due to the complexity of the drainage network and non-uniform surface water flows, the quantification of surface water- groundwater interaction by consideration of hydrodynamics is problematic. Therefore, the chemistry of groundwater and surface water was compared. While the estimated contribution of rainfall to groundwater level fluctuations was significant (46%), high evapotranspiration rates reduced net recharge and it was concluded that baseflow to drains and creeks during dry periods was insignificant, and groundwater velocities in the shallow aquifer are low. The study illustrates the value of both hydrodynamic and hydrogeochemical analyses in estuarine settings where relict salinity and groundwater-aquifer interactions impact significantly on water quality. Saline groundwater is chemically distinct from theoretical mixtures of seawater and freshwater. The study also demonstrates the value of particular chemical parameters, e.g. Na/Cl and SO4/Cl ratios and stable water isotopes, for identifying hydrologic processes in this setting.

The Pimpama estuarine plain in subtropical southeast Queensland is comprised of Quaternary sediments infilling older bedrock. These multilayered unconsolidated sediments have various depositional origins, and are highly heterogeneous. The plain is low-lying and the surface drainage is controlled by flood mitigation measures including tidal gates and channelised streams. The control of surface drainage potentially affects the shallow water table. This modification of hydrology has implications for future viability of agriculture and also the environmental health of waterways. Increased landscape modification and water management is likely in the coming years. The combination of sediment heterogeneity, low hydraulic gradients, and artificial drainage modification result in the plain being hydrogeologically complex. In order to understand hydrologic processes in this setting, a multi-disciplinary research programme was conducted which included a drilling program, overland electromagnetic induction and other geophysical surveys (downhole gamma log, electromagnetic induction and magnetic susceptibility) to initially establish the geologic framework. These surveys were followed by hydrogeochemical testing which includes for major and minor ions and also stable isotopes, and mineralogical analysis of drillhole material. Underlying basement rock occurs at up to 60 m depth. Unconsolidated gravel and sand deposits occur within incised paleo-valleys and are overlain by predominantly low-permeability fluvial sandy clays and estuarine and lagoonal muds. Fine-grained delta sands occur in the top 15 m of the sub-surface. Within the unconsolidated sediments, hydrodynamic trends clearly discriminated between upper unconfined and lower semi-confined aquifer systems. A comparison of surface water and shallow groundwater levels indicate limited interaction of groundwater and surface water. Hydrogeochemical analysis effectively distinguished between groundwater bodies, and also distinguished saline groundwater from seawater. Trends in major ion chemistry in the semi-confined system (particularly Na/Cl and Ca/Cl ratios) showed ion exchange accompanying saline intrusion. However, due to factors such as mineral dissolution, major ion chemistry does not clearly identify solute flux trends in the shallow aquifer system. Water stable isotope analysis (δ18O and δ2H) indicated the provenance of fresh and saline groundwater and also the relative importance of the principal hydrologic processes, i.e. evaporation and water uptake by plants. Groundwater exhibited a wide range in salinity, from very fresh to hypersaline. The formation of hypersaline groundwater was attributed largely to uptake of water by mangrove forests. Since mangrove forests were more extensive at the time of the Holocene maximum sea level (approximately 6,000 years ago) than at present, some of this groundwater may represent relict salinity from this earlier time. The relationship of relict salinity to low permeability sediments, particularly at intermediate depths, and their depositional history was examined. Vertical salinity gradients and hydrogeochemistry within these sediments varied according to position within the plain, suggesting deposition under various hydrological and sea level regimes. A preliminary investigation using analysis of stable sulfate isotopes (δ34S and δ18OSO4) was made. This study shows substantial potential for the application of this technique for quantification of solute flux and sulfur chemical transformations within settings such as this coastal plain. To establish shallow groundwater flow processes, a MODFLOW-based numerical model was used to inversely estimate aquifer parameters under various recharge scenarios. The model was designed to examine the relative importance of evapotranspiration and discharge to surface waters. However, largely due to the complexity of the drainage network and non-uniform surface water flows, the quantification of surface water- groundwater interaction by consideration of hydrodynamics is problematic. Therefore, the chemistry of groundwater and surface water was compared. While the estimated contribution of rainfall to groundwater level fluctuations was significant (46%), high evapotranspiration rates reduced net recharge and it was concluded that baseflow to drains and creeks during dry periods was insignificant, and groundwater velocities in the shallow aquifer are low. The study illustrates the value of both hydrodynamic and hydrogeochemical analyses in estuarine settings where relict salinity and groundwater-aquifer interactions impact significantly on water quality. Saline groundwater is chemically distinct from theoretical mixtures of seawater and freshwater. The study also demonstrates the value of particular chemical parameters, e.g. Na/Cl and SO4/Cl ratios and stable water isotopes, for identifying hydrologic processes in this setting.

Daniel Zeh studied dugong movements and established proof of concept that acoustic technology provides results comparable to satellite/GPS in two dimensional space use and extends to three dimensional space use. He found evidence of behavioural thermoregulation and the existence of a possible dugong movement corridor, extending current knowledge of dugong behavioural ecology.