Reservation of important wetlands - recent experiences in conservation planning and practical implementation in Victoria

The establishment of a comprehensive, adequate and representative (CAR) reserve system is not only an objective of all States and Territories but it is an international commitment, since Australia signed the Convention on Biological Diversity. Various reviews note that Australia lacks a representative freshwater reserve system. However, there has been surprisingly little quantitative analysis on the reservation of freshwater ecosystems from which to identify the gaps or deficiencies in the reserve system.

We compared aspects of reservation in wetlands in northern Victoria before and after a major public land use investigation by the government-appointed Victorian Environmental Assessment Council, which sought specifically to recommend a CAR reserve system. Significant improvements in the reservation status for depleted and under-reserved wetland ecosystems, and improved reserve design have been recommended by the investigation. Increases in the reservation of nationally and internationally significant wetlands were also recommended. These recommendations are now under consideration by the Victorian Government.

Some of the challenges in decision-making during this investigation and their implications on wetland conservation are highlighted. The paper concludes by outlining broader policy dilemmas, decisions and debates that that require addressing in relation to developing a system of Freshwater Protected Areas in Australia.

Can sand slugs in rivers deliver conservation benefits? The biodiversity value of tributary junction plug wetlands in the Glenelg River, Australia

Restoration works are carried out to alleviate human impacts and improve habitats within ecosystems. However, human impacts may also create new (anthropogenic) habitat for species to exploit.A dilemma arises when proposed restoration works would remove anthropogenic habitat and the assemblages it supports. Sediment input into the Glenelg River has formed tributary junction plug wetlands at confluences. Sand slug removal is proposed as part of river rehabilitation, but would also drain plug wetlands. We sampled four plug wetland, four river run and three river pool sites to determine whether plug wetlands influence water quality and add to the biodiversity of macroinvertebrates in the Glenelg River.Water quality and macroinvertebrate diversity were similar in plug wetlands, river runs and river pools.Assemblages were distinct among all sites, regardless of type, so there was no characteristic ‘plug-wetland fauna’. Therefore, although removal of plug wetlands would not cause a dramatic loss of invertebrate biodiversity, it would destroy anthropogenic habitat that supports a similar range of species to natural habitats in a river subject to multiple degrading processes. Gains from rehabilitation should be weighed against the value of anthropogenic habitat and the extent of similar habitat lost elsewhere in the ecosystem.

Broad-scale mapping of temporary wetlands in arid Australia

We describe a robust methodology to detect and estimate the size of temporary wetlands using AVHRR satellite data within large areas (106 km2) of the arid zone. The methodology uses spectral matching and exclusion of salt surfaces to discriminate between water and non-water surfaces. The status of 115 lakes was used to evaluate the methodology. A classification accuracy of 98% was achieved for wetlands >120 ha, with accuracy of area estimates varying with the size and shape of individual lakes. Spectral matching of AVHRR data has methodological and cost advantages over the use of higher spatial resolution data for understanding changes in the distribution of water at broad scales.

Nutrient contribution to hyper-eutrophic wetlands in Perth, Western Australia

This thesis investigates nutrient contribution to six hyper-eutrophic lakes located within close proximity of each other on the Swan Coastal Plain and 20 kilometres south of the Perth Central Business District, Western Australia. The lakes are located within a mixed land use setting and are under the management of a number of state and local government departments and organisations. These are a number of other lakes on the Swan Coastal Plain for which the majority are less than 3 metres in depth and considered as an expression of the groundwater as their base is below the regional groundwater table throughout most of the year. The limited amount of water quality data available for these six lakes and the surface water and groundwater flowing into them has restricted a thorough understanding of the processes influencing the water quality of the lakes. Various private and public companies and organisations have undertaken studies on some of the individual wetlands and there is a wide difference in scientific opinion as to the major source of the nutrients to those wetlands. These previous studies failed to consider regional surface water and groundwater effects on the nutrient fluxes and they predominantly only investigated single wetland systems. This study attempts for the first time to investigate the regional contribution of nutrients to this system of wetlands existing on the Swan Coastal plain. As such, it also includes new research on the nutrient contribution to some of the remaining wetlands. The research findings indicate that the lake sediments represent a considerable store of nutrients (nitrogen and phosphorus). These sediments in turn control the nutrient status of the lake's water column. Surface water is found to contribute on an event-basis load of nutrients to the lakes whilst the groundwater surprisingly appears to contribute a comparatively low input of nutrients but governs the water depth. Analysis of the regional groundwater shows efficient denitrifying abilities as a result of denitrifying bacteria and the transport is localised. Management recommendations for the remediation of the social and environmental value of the lakes include treatment of the lake’s sediments via chemical bonding or atmospheric oxidation; utilising the regional groundwater’s denitrifying abilities to ‘treat’ the surface water via infiltration basins; and investigating the merits of managed or artificial aquifer recharge (MAR).

Renovation of the Masterfoods wetlands

This thesis describes the renovation of the Masterfoods' wetlands in Ballarat, including an analysis of the behaviour of the three key components upon which a functioning constructed treatment wetland relies: water quality, wetland design and the wetland plants. Includes a description of replanting and the subsequent improvement in treatment function.

Environmental water requirements of isolated floodplain wetlands

Wetlands are threatened ecosystems, particularly due to regulation of major rivers. This thesis investigated the water requirements of floodplain wetlands. Spatial analysis was applied to evaluate how alternative management options impact on native vegetation. Due to limited water in river systems, this study has important implications for conservation of remaining wetlands.

Managing alternative stable states in constructed wetlands using artificial substrates

Algal blooms are a management concern in shallow water bodies. This project investigated the use of artificial substrates to enhance biofilm growth and shift primary production from the open water to artificial surfaces. This resulted in a shift from algal dominated wetland back to a clear water macrophyte dominated wetland.

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.

Animal–plant–microbe interactions : direct and indirect effects of swan foraging behaviour modulate methane cycling in temperate shallow wetlands

Wetlands are among the most important ecosystems on Earth both in terms of productivity and biodiversity, but also as a source of the greenhouse gas CH₄. Microbial processes catalyzing nutrient recycling and CH₄ production are controlled by sediment physico-chemistry, which is in turn affected by plant activity and the foraging behaviour of herbivores. We performed field and laboratory experiments to evaluate the direct effect of herbivores on soil microbial activity and their indirect effects as the consequence of reduced macrophyte density, using migratory Bewick’s swans (Cygnus columbianus bewickii Yarrell) feeding on fennel pondweed (Potamogeton pectinatus L.) tubers as a model system. A controlled foraging experiment using field enclosures indicated that swan bioturbation decreases CH₄ production, through a decrease in the activity of methanogenic Archaea and an increased rate of CH₄ oxidation in the bioturbated sediment. We also found a positive correlation between tuber density (a surrogate of plant density during the previous growth season) and CH₄ production activity. A laboratory experiment showed that sediment sterilization enhances pondweed growth, probably due to elimination of the negative effects of microbial activity on plant growth. In summary, the bioturbation caused by swan grazing modulates CH₄ cycling by means of both direct and indirect (i.e. plant-mediated) effects with potential consequences for CH₄ emission from wetland systems.

Evaluating the performance of horizontal subsurface flow constructed wetlands using natural zeolite (escott)

The objective of the present study was to assess the simultaneous removal of physiochemical parameters in moderate strength wastewater using a lab scale horizontal subsurface flow constructed wetland (HFCW) with natural zeolite as a substrate. In this study, high-density polyethylene tanks (0.36 m²) were planted with phragmites australis and scirpus maritimus and received 0.012 m³/d to 0.08 m³/d of synthetic wastewater corresponding to a HLR of 0.035 to 0.243 m/d and a COD loading rate of 0.0148 kg COD (m².d)^-1 to 0.026 kg COD (m².d)^-1. The HFCW was subjected to three hydraulic retention times (HRT) for 4, 3 and 2 days respectively. Averaged data reported coincided with the plant age (4 to 55 weeks) and covered the entire cold season and early part of the hot season. Based on the 55 weeks of operation, the HFCW unit with zeolite achieved significantly higher removal for COD (85 to 88%), TN (54 to 96%), NH₄-N (50 to 99%) and TSS (91 to 96%) respectively at all HRT. This system was proved to be tolerant to high organic loadings and nutrients, suggesting these substrates as viable options for biological treatment of wastewater.

Baseline measurements on the performance of four constructed wetlands in tropical Australia

Constructed wetlands provide several benefits that are not solely limited to storm water management and are becoming common in storm water management. In this research, four recently constructed wetlands underwent in situ and laboratory water sampling to determine their efficiency in removing storm water pollutants over a 5-month period. From the sampling results, it was determined that each of the wetlands was able to reduce the concentration of pollutants in the stormwater. To aid in the assessment of the wetlands against each other, a model was developed to determine the extent of removal of stormwater pollutants over the length of the wetland. The results from this model complimented the data collected from the field. Improvements, such as increased amounts of vegetation were recommended for the wetlands with the aim of increasing the effectiveness. Further investigations into the wetlands will allow for better understanding of the wetland's performance.