Jane M. Chambers

The potential use of wetlands to reduce phosphorus export from agricultural catchments

Natural and artificial wetlands have the potential to reduce phosphorus (P) loads from dispersed agricultural runoff and from point sources in the Peel-Harvey catchment, Western Australia. Small experimental systems containing wetland plants and substrate have shown significant removal of P from inflowing water, the proportion of P removed being dependent on P concentration and flow rate of water through the system. The use of artificial wetlands to treat diffuse agricultural runoff is limited by the highly seasonal runoff typical of this Mediterranean climate, while use at point sources has so far been unsuccessful because compounds from the effluent clog the wetland ‘filters’. Treatment at point sources may well be feasible after further research.Natural wetlands in the catchment absorb P received in runoff from farmland and, in the absence of any outflow channels to the drainage system, confine this P within the boundaries of the wetland. Disturbance to wetlands may reduce their efficiency in absorbing nutrients and may release P stored in the vegetation and sediment to the water. The conservation of natural wetlands is recommended to maximise nutrient retention in the catchment.

Evaluation of a bacterial algal control agent in tank-based experiments.

A bacterial-based bioremediation product, LakeRelief™ by Novozymes (Waterguru LakeRelief, 2011), was tested in a series of experiments between October 2008 and March 2009 to evaluate its suitability as a short-term intervention technique to reduce algal blooms in the Swan-Canning River system. Results from fibreglass tank experiments (1100 L) suggested that the product did not actively attack and lyse algal cells. The product decreased NH(4) and NO(x) concentrations in treated tanks, both aerated and non-aerated. Product application decreased PO(4) concentrations in non-aerated tanks but not in aerated tanks. The product appeared to suppress algal growth in non-aerated tanks over short periods (several days). Algal growth regularly diminished after product application but reappeared shortly afterwards. Aeration had a negative effect on bacterial proliferation in the tanks, possibly through alteration of environmental conditions (e.g. water mixing). As a consequence of the environmental conditions in the tanks being counterproductive to the development of a representative microbial composition, several aspects regarding the products effectiveness could not be assessed satisfactorily in the tank experiments. The importance of long-term nutrient immobilisation into a well developed food web and the subsequent nutrient removal through removal of the top order organisms is highlighted.

Potential of submerged macrophytes to support food webs in lowland agricultural streams

Submerged plants are often abundant in lowland streams in agricultural landscapes, but little is known of their role in stream ecosystems compared to riparian vegetation. We investigated the importance of submerged macrophytes as a basal resource of food webs in stream reaches with good and poor riparian vegetation condition, using mixing model analysis with stable carbon and nitrogen isotopes. Epilithic periphyton and terrestrial detritus were important basal resources in good condition reaches, although where macrophytes were present they contributed to food webs. Higher assimilation of either the macrophyte Cycnogeton huegelii or conspicuous epiphytes on C. huegelii leaves was associated with poor riparian condition. Where Potamogeton ochreatus and Ottelia ovalifolia occurred in poor condition reaches, these macrophytes contributed moderately to the food web, but were probably of greater importance as substrates for epiphytic algae. Mixing models indicated invertebrates commonly had generalist feeding strategies, feeding on the most available resource at each reach. Thus, where riparian vegetation is limited, submerged macrophytes may support opportunistic consumers both directly and as a substrate for epiphytes, thereby partially compensating for the loss of allochthonous resources in lowland agricultural streams.

A model of flow and nutrient absorption in artificial wetland systems

An analysis is presented of nutrient absorption controlled by a simple growth law in an artificial wetland system. The distribution of transit times for fluid particles to pass through the wetland is described by a function determined from experimental dye data, and the model includes a constant diffusion term, which is important at slow flow rates. The nutrient absorption efficiency is determined as a function of the flow rate and size of the system. Conditions for maximum absorption are derived from the model for a fixed rate of nutrient input to the wetland using an assumption of nonoverlapping paths. Diffusion within the wetland tends to decrease the absorption efficiency, but this effect may be negligible, provided that the optimum flow rate lies well above a certain minimum value, which is derived from the analysis.

Inland aquatic environments II - the ecology of lentic and lotic waters

In this chapter we explain how the physical parameters of aquatic systems result in different types of habitats in still or flowing waters.

Inland aquatic environments I - wetland diversity and physical and chemical processes

In this chapter we describe the main environmental factors determining the biota that inhabit different types of inland water bodies.

The Ecology of Wetlands Created in Mining-Affected Landscapes

This review deals with the establishment of wetlands on land affected by mining, but it is useful to recall that the mining industry may have an impact in a number of ways, including direct impacts on existing wetlands, for example, physical obliteration, altered groundwater contours, heavy metal contamination, and eutrophication (nutrient enrichment and its consequences). Our emphasis is not so much on these impacts, or on techniques to rehabilitate wetlands after such disturbance, but on creating wetlands as a form of rehabilitation of mined lands rather than returning them to agricultural or forest production. However, some of these impacts leave a heritage that must be taken into account when attempting to create wetlands in a landscape affected by mining.