James Udy

Healthy Waterways · Science and Innovation

Seagrass condition, resilience and ecosystem services are affected by the below-ground tissues (BGr) but these are rarely monitored. In this study we compiled historical data across northern Australia to investigate biomass allocation strategies in 13 tropical seagrass species. There was sufficient data to undertake statistical analysis for five sp...

Implementing management actions to achieve environmental outcomes requires defining and quantifying ecological targets, but this is a complex challenge, and there are few examples of how to quantitatively set them in complex dynamic marine ecosystems. Here we develop a methodology to devise ‘desired state’ for tropical seagrasses in Cleveland Bay,...

In environmental management, ‘values’ are often considered as inherent in the physical environment, rather than being recognised as human constructs: the most deeply held and stable of ways people think about environments. An understanding of how people value environments, beyond the well-recognised utilitarian and moralistic values on which most e...

In contrast to Europe, the USA and South Africa, Australia has no specific, overarching federal legislation to underpin a nationally-coordinated framework for monitoring, assessing and reporting estuarine condition. This has resulted in a complex mosaic of diverse approaches and governance structures, hindering the ability to make inter-State compa...

Freshwater ecosystems are declining under climate change and land-use change. To maximize the return on investment in freshwater conservation with limited financial resources, managers must prioritize management actions that are most cost-effective. However, little is known about what these priorities may be under the combined effects of climate an...

Methane (CH4) is a potent greenhouse gas of primarily biogenic origin. Aquatic systems are significant CH4 sources but uncertainty surrounds their estimated source strengths. There is limited understanding of CH4 concentrations variability in both space and time (dynamics) and the responsible drivers. Water column CH4 dynamics were investigated in...

Emerging literature on climate adaptation suggests the need for effective ways of engaging or activating communities and supporting community roles, coupled with whole-of-system approaches to understanding climate change and adaptation needs. We have developed and evaluated a participatory approach to elicit community and stakeholder understanding...

Surface water methane (CH4) and nitrous oxide (N2O) concentrations and fluxes were investigated in two subtropical coastal embayments (Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010-2012. Water-air fluxes were estim...

Surface water methane (CH4) and nitrous oxide (N2O) concentrations and fluxes were investigated in two subtropical coastal embayments (Bramble Bay and Deception Bay, which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010-2012. Water-air fluxes were estim...

The 95th percentile of numbers of intestinal enterococci per 100 mL, associated with estimated health risk, are used for determination of the microbial assessment category (MAC) in the National Guidelines for Managing Risks in Recreational Water published by the Australian National Health and Medical Research Council in 2008. A statistical decision...

Surface water methane (CH4) and nitrous oxide (N2O) concentrations were measured and diffusive fluxes were estimated in three subtropical freshwater reservoirs (Little Nerang Dam (LND), Lake Wivenhoe (LW) and Lake Baroon (LB)) in southeast Queensland, Australia, during four seasons in 2011 - 2012. All reservoirs were strong sources of CH4 in all se...

Background / Purpose: A spatially explicit risk assessment is being performed to identify the hotspots of risk for cumulative threats in seagrass habitat across Australia. Seven current anthropogenic risks and three risks from future climate change predictions were identified and a risk level assigned. Main conclusion: A seagrass habitat map a...

Moreton Bay and its associated estuaries are an example of a complex aquatic system that is under increasing pressure from rapid population growth and urbanisation. Although the extent of decline in ecosystem health within Moreton Bay and its associated estuaries is significant and well documented, a range of innovative management responses have be...

The livelihood of many coastal communities in the Pacific Islands is directly dependent on the health of adjacent coral reefs. Reduction in water quality and over-harvesting of herbivorous fish are known to drive reef ecosystems towards a more degraded state. Community-based resource management practices have the potential to improve damaged reefs...

Methane (CH4) and nitrous oxide (N2O) are two key greenhouse gases. Their global atmospheric budgeting is, however, flout with challenges partly due to lack of adequate field studies determining the source strengths. Knowledge and data limitations exist for subtropical and tropical regions especially in the southern latitudes. Surface water methane...

Blooms of the toxin-producing cyanobacterium Cylindrospermopsis raciborskii occur in tropical and subtropical lakes during spring-summer but the mechanisms behind bloom formation are unclear. This study tests the hypothesis that C. raciborskii accumulations in freshwater systems are facilitated by selective copepod grazing. Prey selection was exami...

Caulerpa taxifolia is a marine alga native to tropical and subtropical regions, and invasive in temperate regions worldwide. The aim of this study was to quantify the impacts of water temperature, benthic light and nutrient enrichment on horizontal expansion of C. taxifolia, in the absence of competition from other benthic flora. Field experiments...

Phosphorus (P) is often a key limiting nutrient in freshwater systems, and excessive P can result in algal blooms, with flow-on effects to aquatic food webs. P sorption is an important process in aquatic and terrestrial ecosystems whereby phosphate (PO4 3−) is exchanged between liquid and solid phases. This study shows that differences in the conce...

Methane (CH4) and nitrous oxide (N2O) are two atmospheric trace gases of great scientific interest. They are potent greenhouse gases (GHG) that together contribute nearly 30% of the global anthropogenic forcing. N2O is also a key ozone-depleting substance. Atmospheric CH4 concentrations have nearly tripled pre-industrial levels and N2O is currently...

Accurately quantifying total freshwater storage methane release to atmosphere requires the spatial temporal measurement of both diffusive and ebullitive emissions. Existing floating chamber techniques provide localised assessment of methane flux, however, significant errors can arise when weighting and extrapolation to the entire storage, particula...

This study investigated the storage of nitrogen (N) and phosphorus (P) in the biomass, bed sediments and water column of representative reaches of a sub-tropical river, the upper Brisbane River (UBR), Queensland, Australia, and contrasted instream storage with total wet season exports. In reaches which contained accumulated fine sediments, more tha...

This study examined the link between terrestrial and aquatic phosphorus (P) speciation in the soils and sediments of a subtropical catchment. Specifically, the study aimed to identify the relative importance of P speciation in source soils, erosion and transport processes upstream, and aquatic transformation processes as determinants of P speciatio...

This study investigated the storage of nitrogen (N) and phosphorus (P) in the biomass, bed sediments and water column of representative reaches of a subtropical river, the upper Brisbane River (UBR), Queensland, Australia, and contrasted instream storage with total wet season exports. In reaches which contained accumulated fine sediments, more than...

Shifts in diatom species composition may be used to infer past changes in environmental conditions in fresh, estuarine and marine systems. Establishing the primary drivers of present day diatom community composition is a vital step in their use as a proxy for past conditions. Moreton Bay, Australia, has experienced extensive modification of its cat...

The ability to predict reservoir vulnerability to summer blooms and to detect thresholds of change in phytoplankton cell densities in response to environmental factors would provide information critical for decision making, hazard prevention and management. We used a new method to detect synchronous change points in densities of phytoplankton taxa...

The aim of this study was to explore the potential of three aquatic weeds, water hyacinth, cabomba, and salvinia, as substrates for anaerobic digestion. A set of four pilot-scale, batch digestions were undertaken to assess the yield and quality (% methane) of biogas from each plant species, and the rate of degradation. A set of 56 small-scale (100...

The present study investigated whether drying and desiccation substantially increase the biologically available phosphorus (P) in riverbed sediments from a dry subtropical river. Sequential extraction and batch equilibrium experiments were undertaken on sediments with contrasting organic matter content, percentage fines and P content. The response...

Cyanobacterial blooms in drinking water reservoirs present a major ecosystem functioning and human health issue. The ability to predict reservoir vulnerability to these blooms would provide information critical for decision making, hazard prevention and management. We developed a new, comparative index of vulnerability based on simple measures of r...

A marked decline in the contribution by Marovo Lagoon to the annual total bêche-de-mer production of the Solomon Islands from 58% in 1989 to 17% in 2003 prompted investigation of their current biomass and diversity. We also assessed changes to critical ecological services and the prospects for population recovery following a fisheries closure. Day...

The marine alga Caulerpa taxifolia Vahl (C. Agardh), recognized globally as one of the most prolific non-native species introductions, has been introduced to several temperate locations from where it has since rapidly expanded. C. taxifolia is protected by a toxin (terpenoid) in its tissues that limits grazing by native herbivores. Sacoglossan moll...

The Lake Wivenhoe Integrated Wireless Sensor Network is conceptually similar to traditional SCADA monitoring and control approaches. However, it is applied in an open system using wireless devices to monitor processes that affect water quality at both a high spatial and temporal frequency. This monitoring assists scientists to better understand dri...

A decrease in seagrass cover and a commensurate increase in Caulerpa taxifolia distribution in Moreton Bay have prompted concern for the impact that habitat change may have on faunal communities. Therefore, it is important to understand the patterns of habitat use. We examined habitat selection of three common seagrass species: double-ended pipefis...

Caulerpa taxifolia, an invasive species elsewhere in the world, is native to Moreton Bay where its distribution has been increasing in recent years. In Australia, dense beds of C. taxifolia are predominantly found in areas of low light and high nutrients (low water quality). Monitoring data from Moreton Bay suggests that native C. taxifolia is not...

This paper describes a novel Autonomous Surface Vehicle capable of navigating throughout complex inland water storages and measuring a range of water quality properties and greenhouse gas emissions. The 16 ft long solar powered catamaran can collect this information throughout the water column whilst the vehicle is moving. A unique feature of this...

Nuisance blooms of macroalgae are increasingly common in response to nutrient pollution of the coastal zone. In Queensland Hincksia sordida, a filamentous brown alga, have been increasing in the Noosa area in summer over the last two decades. Because the Noosa area is relatively unpolluted compared to other locations where blooms are common our stu...

Coastal waters worldwide have experienced an increase in the occurrence of harmful algal blooms. Over the past decade, nuisance blooms of the toxic cyanobacterium Lyngbya majuscula have increased in frequency and severity in south-east Queensland, Australia, with blooms in Moreton Bay hypothesised to be linked to increased inputs of dissolved nutri...

Settlement tiles were used to characterise and quantify coral reef associated algal communities along water quality and herbivory gradients from terrestrial inXuenced near shore sites to oceanic passage sites in Marovo Lagoon, the Solomon Islands. After 6 months, settlement tile communities from inshore reefs were dominated by high biomass algal tu...

Lyngbya majuscula, a benthic filamentous cyanobacterium found throughout tropical and subtropical oceans, has been shown to contain the tumour promoting compounds lyngbyatoxin A (LA) and debromoaplysiatoxin (DAT). It grows epiphytically on seagrass and macroalgae, which also form the basis of the diet of the herbivorous green turtle (Chelonia mydas...

Each of the following sections is introduced by community concerns (see boxes), voiced at the Batuna meeting in June 2006, about the declining health of Marovo Lagoon. These are then assessed using independent data from the project team’s social and scientific research, followed by suggested actions. In effect this chapter constitutes a reply to th...

In this chapter we draw together the range of issues identified by our research and reflect on thei importance for making meaningful recommendations for Marovo Lagoon. In keeping with our interdisciplinary research design, we set our research findings and consequent recommendations in a scientific and social discourse. Many of the issues we identif...

Although many studies measure the abundance of benthic microalgae (BMA), at the meters squared scale, comparing these studies is difficult due to the variety of sampling, extraction, and analysis techniques. This difficulty is exacerbated by the fact that BMA abundance has high spatial and temporal variability, at all spatial scales. A suitable sta...

Nutrients such as bioavailable iron, phosphorus and nitrogen have been hypothesised to stimulate nuisance blooms of the toxic, marine cyanobacterium Lyngbya majuscula. The current study used two laboratory based biological assay techniques to test whether the addition of iron, phosphorus and nitrogen enhanced L. majuscula growth. A three-way analys...

Benthic cyanobacteria blooms, including those of the nitrogen-fixing species Lyngbya majuscula, appear to be becoming more numerous and widespread in marine habitats worldwide, and have negative impacts on the environment and human health. The progression of a L. majuscula bloom in south-east Queensland, Australia was mapped along with intensive bi...

With this three-year project from 2004 to 2007, The University of Queensland (UQ) team set out to provide a scientific basis to support community initiatives for the sustainable management of marine resources in Marovo Lagoon, Solomon Islands. We largely achieved this goal and provided the maximum benefit possible for local communities—albeit a wor...

This chapter focuses on socio-economic issues that impact on marine conservation aspirations. The chapter begins with an overview of the socio-economic context of the communities where we primarily worked, followed by the results of our analysis of tourism in the lagoon (paying particular attention to livelihood and resource management issues) and...

This chapter focuses on socio-economic issues that impact on marine conservation aspirations. The chapter begins with an overview of the socio-economic context of the communities where we primarily worked, followed by the results of our analysis of tourism in the lagoon (paying particular attention to livelihood and resource management issues) and...

With this three-year project from 2004 to 2007, The University of Queensland (UQ) team set out to provide a scientific basis to support community initiatives for the sustainable management of marine resources in Marovo Lagoon, Solomon Islands. We largely achieved this goal and provided the maximum benefit possible for local communities—albeit a wor...

To better understand how freshwater ecosystems respond to changes in catchment land-use, it is important to develop measures of ecological health that include aspects of both ecosystem structure and function. This study investigated measures of nutrient processes as potential indicators of stream ecosystem health across a land-use gradient from rel...

We tested direct and indirect measures of benthic metabolism as indicators of stream ecosystem health across a known agricultural land-use disturbance gradient in southeast Queensland, Australia. Gross primary production (GPP) and respiration (R24) in benthic chambers in cobble and sediment habitats, algal biomass (as chlorophylla) from cobbles and...

Harmful algal blooms (HABs) have increased in abundance and severity in recent decades. Whereas the implications for human impacts and intoxication resulting from blooms have been extensively studied, the ecological implications of these microalgae are less well understood. Many HAB species produce biologically active, secondary metabolites and the...

Lyngbya majuscula, a toxic cyanobacterium, was observed blooming during June-July (winter) 2002 in Shoalwater Bay, Queensland, Australia, an important feeding area for a large population of green turtles (Chelonia mydas). The bloom was mapped and extensive mats of L majuscula were observed overgrowing seagrass beds along at least 18 km of coast, an...

Over the past decade, toxic blooms of the cyanobacterium Lyngbya majuscula have increased in frequency and severity in south-east Queensland, Australia, with blooms in Deception Bay linked to increased inputs of dissolved nutrients and organic carbon from land-based sources. The current study investigates the potential for groundwater from ten comb...

The bioavailability of iron, in combination with essential macronutrients such as phosphorus, has been hypothesised to be linked to nuisance blooms of the toxic cyanobacterium Lyngbya majuscula. The present laboratory study used two biological assay techniques to test whether various concentrations of added iron (inorganic and organically chelated)...

During the last decade there has been a significant rise in observations of blooms of the toxic cyanobacterium Lyngbya majuscula along the east coast of Queensland, Australia. Whether the increase in cyanobacterial abundance is a biological indicator of widespread water quality degradation or also a function of other environmental change is unknown...

Nitrogen loading to aquatic ecosystems from sewage is recognised worldwide as a growing problem. The use of nitrogen stable isotopes as a means of discerning sewage nitrogen in the environment has been used annually by the Ecosystem Health Monitoring Program in Moreton Bay (Australia) since 1997 when the technique was first developed. This ("sewage...

For the managers of a region as large as the Great Barrier Reef, it is a challenge to develop a cost effective monitoring program, with appropriate temporal and spatial resolution to detect changes in water quality. The current study compares water quality data (phytoplankton abundance and water clarity) from remote sensing with field sampling (con...

Potential denitrification rates were measured using the acetylene block method, in sediments collected from streams in the sub-tropical, south-east Queensland region of Australia. Our aim was to estimate how much nitrogen could be removed from lotic systems by denitrification at the regional scale. Denitrification measured at 65 sites in August and...