Selected Current Research
Species coexistence in aquatic insects
QAEL members: Rebecca Lester, Galen Holt and Ashley Macqueen
Collaborators: Barbara Downes, Peter Chesson, Wim Bovill
Funding: Australian Research Council
We seek to connect coexistence theory to the real world in an aquatic insect community. Coexistence theory, as developed primarily by Peter Chesson and colleagues, is a robust mathematical theory describing how environmental variation can interact with competition and predation to maintain diversity. However, the application of this theory to real communities has been limited. This project will connect coexistence theory with experimental work in a community of caddisflies in upland streams, where Barbara Downes and colleagues have developed a large body of work demonstrating that the oviposition choices of caddisfly females and dispersal generate high variation in egg density and have important effects on population dynamics. By developing theory to address the particular life history characteristics of caddisflies, combined with empirical work to quantify how those life history characteristics affect density dependence, we will achieve strong tests of coexistence mechanisms in a real community, and gain a better understanding of diversity maintenance in stream insect communities.
Species diversity in a fractal world
QAEL memebers: Rebecca Lester
Funding: Australian Research Council
Complexity in physical habitat structure in many environments is positively correlated with the diversity of resources and biodiversity within those environments. Identifying a mechanism behind this pattern is difficult, in part because of the difficulty in quantifying that complexity across different ecosystem types. This makes it difficult to undertake general tests of hypotheses across ecosystems. One method of quantifying complexity that is applicable across ecosystem types is called the fractal dimension. Fractal dimensions utilise values between the ubiquitous values of 1, 2, and 3, used to represent a line, surface or volume, respectively. While the underlying geomorphological features of rivers have been shown to behave in a fractal manner (e.g. the branching structure of streams), it is unknown whether stream resources and the biota that utilise them can be described in this way. Here, we attempt to apply fractal dimensions to measure physical complexity in streams and test competing mathematical models for describing the types and diversity of species of caddisfly in stream environments in space and time.
Improved monitoring and control of aquatic weeds in southern irrigation supply networks: Murrumbidgee Irrigation network scoping study
QAEL Members: Jan Barton
Collaborators: John Hornbuckle, James Brinkhoff and Wendy Quayle
Funding: Murrumbidgee Irrigation
Increased demand for high flow rates and changing water delivery metrics have caused aquatic weed management to become a major issue in regulated irrigation supply systems within the Murrumbidgee Irrigation network. This scoping study aims to identify monitoring and management techniques that can reduce costs and achieve improved outcomes over current weed management strategies employed in irrigation delivery systems.
Forecasting trajectories of change for Ruppia tuberosa in the Coorong
QAEL Members: Ashley Macqueen and Rebecca Lester
Collaborators: Rebecca White, Sophie Taylor and Klaus Joehnk
Funding: Murray-Darling Basin Authority
Ruppia tuberosa is flowering aquatic plant and an important ecological asset in the Coorong, South Australia, where it provides an important food source for waterbirds and habitat for fish. Though hardy, Ruppia is vulnerable to extreme salinities and rapidly declining water levels in the Coorong. We are developing a tool that draws on existing hydrological and ecological mechanistic models to generate plausible forecasts under different management scenarios. Crucially, this will allow managers to make informed decisions around the allocation of environmental water.
Photo - Kane Aldridge
Functional connectivity and habitat patch use for small-bodied fish in semi-arid aquatic ecosystems.
QAEL Members: Bryce Halliday, Rebecca Lester and Jan Barton
Collaborators: Scotte Wedderburn, Brendan Zampatti and Chris Bice
Funding: Holsworth Wildlife Research Endowment, Centre for Integrative Ecology, Murry Darling Basin Authority and the Department of Environment, Water and Natural Resources
The freshwater lakes at the terminus of the River Murray, the Lower Lakes, are recognised as being ecologically important. Water level variation in these lakes changes the access that fish, especially small-bodied fish (Adult length <200mm) often referred to as bait fish, have to different habitats and their ability to move between habitats. As part of my research I am sampling these fish communities across a range of lake levels to assess its effect on these small fish. This aims to fill significant knowledge gaps in the ecology of these fish communities and the connectivity between different habitats and the two lakes. I am interested in understanding how and why fish are moving, and how they use the different habitats (aquatic vegetation, bare sediments and built structures) for food, shelter and breeding.
My overall research is looking at functional connectivity and habitat patch use for small-bodied fish, the research is broken up into four interconnected projects. The overall outcome of this research will be a comprehensive picture of the habitat association, differential use of, and functional connectivity among, a range of habitat types, including emergent vegetation, submerged vegetation, bare sediments and artificial structures for small-bodied native fish.
Developing habitat models for freshwater macroinvertebrates in Lakes Alexandrina and Albert.
QAEL Members: David Dodemaide and Rebecca Lester
Collaborators: Peter G. Fairweather, Courtney Cummings and Tracey Corbin
Funding: Holsworth Wildlife Research Endowment
Lakes Alexandrina and Albert are shallow fresh waterbodies situated at the end of the Murray-Darling Basin and, along with the Coorong, form a Ramsar Wetland of International Importance. Excessive water regulation and extraction has seen freshwater flows into the Lakes significantly reduced. Under severe drought conditions, water quality has further altered within the lakes, thus investigating the ecological response to such changes is vital for appropriate management of this wetland. Habitat models are a useful tool that can be developed for this purpose. Using environmental monitoring which includes measures of water quality, physical characteristics, macroinvertebrate and macrophyte assemblages we are investigating which environmental variables are important in influencing macroinvertebrates in the Lakes. We will develop predictive habitat models using nonparametric multiplicative regression. The results of the study provide important information to managers regarding how macroinvertebrate assemblages respond to environmental conditions which can be used to inform the allocation of environmental water.