Ben Gawne

Ecosystem science: toward a new paradigm for managing Australia's inland aquatic ecosystems.

Freshwater ecosystems are a foundation of our social, cultural, spiritual and economic well being. The degraded condition of many of Australias river ecosystems is testament to our failure to manage these resources wisely. Ecosystem science involves the holistic study of complex biophysical systems to understand the drivers that influence ecological pattern and process. Ecosystem science should underpin both water management and policy. Our understanding of aquatic ecosystems lags behind the increasing problems caused by past land and water management. Current post-graduate training programmes will not provide the aquatic ecosystem scientists needed by government and management agencies to prevent further degradation. We advocate new initiatives to capture the skills, knowledge and innovation of our research community by engaging scientists and managers in large-scale, long-term ecosystem science programmes across Australia and to integrate these programmes with community aspirations, policy, planning and management. We call on management agencies to increase their support for and uptake and use of ecosystem science. We also advocate establishment of national archives for long-term ecologically-relevant data and samples, and clear custodial arrangements to protect, update and facilitate knowledge-transfer. These initiatives need to be supported by more extensive, better-funded post-graduate and post-doctoral programmes in ecosystem science and management.

Improving ecological response monitoring of environmental flows.

AbstractEnvironmental flows are now an important restoration technique in flow-degraded rivers, and with the increasing public scrutiny of their effectiveness and value, the importance of undertaking scientifically robust monitoring is now even more critical. Many existing environmental flow monitoring programs have poorly defined objectives, nonjustified indicator choices, weak experimental designs, poor statistical strength, and often focus on outcomes from a single event. These negative attributes make them difficult to learn from. We provide practical recommendations that aim to improve the performance, scientific robustness, and defensibility of environmental flow monitoring programs. We draw on the literature and knowledge gained from working with stakeholders and managers to design, implement, and monitor a range of environmental flow types. We recommend that (1) environmental flow monitoring programs should be implemented within an adaptive management framework; (2) objectives of environmental flow programs should be well defined, attainable, and based on an agreed conceptual understanding of the system; (3) program and intervention targets should be attainable, measurable, and inform program objectives; (4) intervention monitoring programs should improve our understanding of flow-ecological responses and related conceptual models; (5) indicator selection should be based on conceptual models, objectives, and prioritization approaches; (6) appropriate monitoring designs and statistical tools should be used to measure and determine ecological response; (7) responses should be measured within timeframes that are relevant to the indicator(s); (8) watering events should be treated as replicates of a larger experiment; (9) environmental flow outcomes should be reported using a standard suite of metadata. Incorporating these attributes into future monitoring programs should ensure their outcomes are transferable and measured with high scientific credibility.

A Bayesian Belief Network Decision Support Tool for Watering Wetlands to Maximise Native Fish Outcomes.

Wetlands are productive and diverse habitats for native fish but can be highly degraded, particularly in the Murray-Darling Basin (MDB), south-eastern Australia. Wetland management requires tools and processes that facilitate the synthesis and application of knowledge for decisions concerning the allocation of environmental water to wetlands to improve environmental outcomes. This paper describes the development of a Decision Support Tool (DST), based on a Bayesian Network designed to provide the best available science and support adaptive management of environmental flows into wetlands. The DST predicts the probability of improvements in fish population health as defined by abundance, population structure and fish condition for introduced common carp and three native species of fish: carp gudgeon, Australian smelt, and golden perch. Model sensitivity and validation showed that fish response varied depending on model inputs, but that responses from the DST were an accurate reflection of fish responses in wetlands based on field data. Ultimately, the success of this DST is dependent on its adoption by wetland managers. Throughout the entire development process, adoption of the DST has been promoted through engagement with managers and subsequently, through initiatives to integrate it into current management initiatives.

Zooplankton dynamics in response to the transition from drought to flooding in four Murray–Darling Basin rivers affected by differing levels of flow regulation

Extreme low and high flow periods associated with droughts and floods regularly influence many river systems, yet little is known regarding their role in shaping riverine zooplankton communities. This study investigated zooplankton dynamics in response to the transition from drought to flooding in four southern Murray–Darling Basin rivers managed by different levels of flow regulation. Results indicated that the onset of flooding was associated with an increase in the taxon richness and total transport (abundance) of zooplankton in the unregulated Ovens and Kiewa Rivers, and an increase in the total transport of zooplankton in the mildly regulated Broken River. In comparison, no significant flood effects on zooplankton taxon richness or transport were detected in the highly regulated Murray River. This suggests that the flooding was beneficial for enhancing zooplankton abundance in the Ovens, Kiewa and Broken Rivers, whereas any potential benefits were comparatively short-term and/or reduced in the Murray River. We hypothesise that the relatively short-term and/or reduced response of the zooplankton community to the flooding in the Murray River was probably largely due to the occurrence of a hypoxic blackwater event in suppressing zooplankton emergence.

Model development of a Bayesian Belief Network for managing inundation events for wetland fish

Wetlands are essential components of floodplain-river ecosystems that often suffer degradation due to river regulation. To this end, the application of environmental water is increasingly being seen as an important amelioration strategy. However, decisions regarding the delivery of water to maximise environmental benefits, including native fish population health, are complex and difficult. This paper describes the development of a Bayesian Belief Network (BBN) model as part of a Decision Support Tool for assessing inundation strategies to benefit native wetland fish. Separate, albeit closely related, BBNs were developed for three native (golden perch Macquaria ambigua, carp gudgeon Hypseleotris spp., Australian smelt Retropinna semoni) and one alien fish species (common carp Cyprinus carpio carpio). The model structure was based on a conceptualisation of the relationships between wetland habitats, hydrology and fish responses, with emphasis on the types of inundation activities undertaken by managers. Conditional probability tables for fish responses were constructed from expert opinion and the model was validated against field data. The predictive ability and sensitivity of the model reflected the inherent high variability in relationships between wetland characteristics, hydrology and fish responses, but was nonetheless able to address satisfactorily such complexities within a holistic framework. As the model was designed in conjunction with managers and evaluated by them, its application will be enhanced by on-going engagement between managers and scientists.

Changes in organic-matter dynamics and physicochemistry, associated with riparian vegetation loss and river regulation in floodplain wetlands of the Murray River, Australia

Extensive clearing of floodplain forests potentially reduces organic matter available to floodplain wetlands. Furthermore, on rivers regulated to provide irrigation water in summer, floodplain wetlands that were previously inundated in spring, now flood in summer/autumn. In the Murray–Darling Basin, Australia, this has changed the timing of organic matter entering the aquatic phase, since leaf fall peaks in summer. Field surveys and mesocosm experiments on floodplain wetlands on the River Murray revealed faster processing rates of leaves in summer/autumn than spring, and no difference between cleared and forested wetlands. Temperature and leaf carbon : nitrogen ratio could not explain these differences, and instead, changes to leaf chemistry associated with ‘terrestrial ageing’ between peak leaf fall in summer and inundation in spring is more likely. The results indicated that the reduction of input of organic matter through riparian tree clearing and changing the timing of inundation interact to alter organic-matter standing stocks and rates of decomposition in floodplain wetlands. Restoring both natural timing of high flows and riparian vegetation might be required for recovery of these wetlands.

Can a collaborative focus on solutions improve our capacity to achieve sustainable water management

Despite the influence of freshwater ecology on investment and management worldwide, many aquatic ecosystems remain severely degraded. By using the Murray–Darling Basin, Australia, as an example, we examined the relationship between freshwater ecological research and interventions implemented to achieve management objectives. We explored four related issues about why freshwater ecologists are rarely satisfied with management solutions and why some adopted remedies have not achieved sustainable management outcomes. We argue that, as a discipline, freshwater ecology does not focus enough on the development of solutions. Many proposed solutions create problems elsewhere and implementation of these solutions can prove unduly problematic. Although there is no simple panacea, changes to the training and career structure of freshwater ecologists could increase researchers’ focus on solutions and enhance their capacity for cross-disciplinary collaboration, especially with social scientists. Such cross-disciplinary outputs are more likely to be palatable because of their system focus. Professor Peter Cullen advocated the importance of undertaking collaborative research to generate predictive capacity. We extend that call by advocating greater cross-disciplinary collaboration and the need for research to focus on the development of solutions rather than problem delineation.

River metabolism and carbon dynamics in response to flooding in a lowland river

Lowland riverine–floodplain systems often have significant but irregular inputs of allochthonous carbon. However, the importance of this carbon to riverine systems remains poorly understood. We assessed open water dissolved organic carbon (DOC) concentrations, metabolism and biofilm stable isotope (δ13C) signatures, upstream and downstream of an extensive floodplain forest on the Murray River, Australia, before and after a flood event. Prior to flooding, all sites had similar concentrations of DOC, rates of metabolism and biofilm δ13C signatures. During the flood DOC concentration increased up to three-fold downstream of the forest, gross primary production (GPP) increased at all sites, but community respiration (CR) increased only at the downstream sites, resulting in decreased in NPP downstream and a slight increase upstream. Biofilm δ13C signatures became depleted by between 4 and 7‰ downstream of the forest during the flood, reflecting a rapid incorporation of allochthonous carbon into the biofilm. These results indicate that flooding led to a substantial increase to the energy budget of the Murray River through the provisioning of large quantities of allochthonous carbon and that terrestrial carbon was processed within the river biofilms. Allochthonous carbon assimilation within biofilms during flooding provides a potential pathway for allochthonous carbon to be incorporated into the metazoan foodweb.

Carbon and nutrient subsidies to a lowland river following floodplain inundation

Despite the perceived importance of floodplain inundation to the functioning of lowland rivers, there is limited understanding of the contribution that floodplains make to the main river channel during floods. In 2010, substantial flooding occurred throughout south-eastern Australia, which provided an opportunity to quantify the export of biological material and nutrients from a floodplain back in to the main river channel. We quantified the amounts of zooplankton, phytoplankton, dissolved organic carbon and nutrients within the main river channel of the River Murray immediately upstream of the Barmah–Millewa Forest, and at two sites immediately downstream of the forest during two flood events in July and October of 2010. Results demonstrated that although a smaller flood event in July did not contribute substantially to an increase in the measured parameters, a much larger flood in October contributed 0.4 tonnes (t) of phytoplankton; 7t of zooplankton and 300t of dissolved organic carbon. This suggests that small floods will provide minimal resource subsidies back into the main channel after the cessation of flooding. In comparison, larger floods that result in large volumes of floodplain water returning to the river will provide substantial subsidies of terrestrially derived resources.

Morphological, physiological and behavioural response patterns of carp gudgeon Hypseleotris spp. to food deprivation: implications for assessing health

Morphological (growth, Fultons condition factor), physiological (per cent dry mass, total lipid content) and behavioural (activity levels) response patterns of carp gudgeon Hypseleotris spp. were examined in response to food deprivation during a 56 day experiment. Considerable variability in the nature and magnitude of these response patterns was observed, suggesting that caution should be taken when interpreting changes in the health of small-bodied fishes based on individual response variables.