Search

Stable isotope signatures (δ13C and δ15N) were used to compare trophic linkages between epilithic periphyton and three families of macroinvertebrates (Baetidae, Leptophlebiidae and Gripopterygidae) in riffles of two rivers with developed catchments (including agriculture, urbanization, impoundment and flow regulation) and two with undeveloped catchments (native forest with no major impoundments) in the Murrumbidgee River system, New South Wales, Australia. Periphyton had much higher average δ15N values and lower average C:N ratios in the developed rivers than in the undeveloped rivers, probably because of the combined effects of nutrient enrichment, upstream impoundment and alteration of riparian vegetation. The invertebrates were generally slightly depleted in 13C and 15N relative to expected values if they were assimilating whole periphyton alone, which suggests that they were assimilating periphyton components selectively or also consuming other foods. The match in isotope signatures between periphyton and invertebrates was only slightly weaker in the developed than in the undeveloped rivers, suggesting that development did not greatly disrupt trophic linkages between periphyton and these invertebrates. [ABSTRACT FROM AUTHOR]

A river classification framework is needed to make good management and planning decisions about river health and biodiversity. We developed a multi-attribute ecological river typology to address this need in the Australian State of New South Wales (801,428 km2). Multivariate patterns in data collected from 322 reference sites were used to define river types for each attribute: abiotic features (10 types), fish assemblages (6 types) and macroinvertebrate assemblages from river edges (8 types) and riffle zones (5 types). We used classification tree analysis to define broad regions for each attribute and then to construct identification keys for river types within each region using slope, elevation, maximum distance from source, latitude and mean annual rainfall. These keys allow the mapping of the likely spatial extent of river types and the assignment of a multi-attribute river-type identity to a river reach anywhere in the State. We used the average dissimilarity distances among the river types and the rates of misclassification of reference sites to assess the reliability of the assignments for different attributes in different regions. This approach to river classification can be applied anywhere in the world, resulting in simple to highly complex typologies depending on data availability. In data-poor areas it may result in a single attribute typology based on remotely derived variables and a coarsely defined reference condition. In data-rich areas the typology may have a large number of attributes using very large datasets with high resolution. [ABSTRACT FROM AUTHOR]

The Darling River, in New South Wales, Australia, is a large semi-arid system with a highly variable flow regime, characterised by unpredictable flooding and drought. The floodplain and riparian zone of the Darling River is dominated by River Red Gum (RRG), Eucalyptus camaldulensis. The large amount of organic matter they produce accumulates on the floodplain and on benches within the channel, and is subject to alternate periods of flooding and drying. This paper examines the effect of alternate periods of flooding and drying on the processing of E. camaldulensis organic matter. Results suggest that RRG leaves provide the most bio-available source of carbon to the system, while bark may be more important as a habitat for invertebrates and other fauna. Results of the field and lab experiments suggest that RRG leaves represent an important source of carbon to the Darling River, with inputs being influenced by the highly variable flow regime.