Site-specific water quality guidelines: 1. Derivation approaches based on physicochemical, ecotoxicological and ecological data.

Generic water quality guidelines (WQGs) are developed by countries/regions as broad scale tools to assist with the protection of aquatic ecosystems from the impacts of toxicants. However, since generic WQGs cannot adequately account for the many environmental factors that may affect toxicity at a particular site, site-specific WQGs are often needed, especially for high environmental value ecosystems. The Australian and New Zealand Guidelines for Fresh and Marine Water Quality provide comprehensive guidance on methods for refining or deriving WQGs for site-specific purposes. This paper describes three such methods for deriving site-specific WQGs, namely: (1) using local reference water quality data, (2) using biological effects data from laboratory-based toxicity testing, and (3) using biological effects data from field surveys. Two case studies related to the assessment of impacts arising from mining operations in northern Australia are used to illustrate the application of these methods. Finally, the potential of several emerging methods designed to assess thresholds of ecological change from field data for deriving site-specific WQGs is discussed. Ideally, multiple lines of evidence approaches, integrating both laboratory and field data, are recommended for deriving site-specific WQGs.

Genetic structure of Melanotaenia australis at local and regional scales in the east Kimberley, Western Australia.

The Kimberley region of Western Australia possesses a poorly studied freshwater fish fauna with high endemism in an aquatic landscape subject to monsoonal floods and dry season isolation. In the first population genetic study of freshwater fish in this region, the authors tested the effects of geographic barriers on genetic structure at multiple spatial scales in east Kimberley populations of the western rainbowfish, Melanotaenia australis, the most widespread and abundant species in the region. Based on allozyme comparisons, hierarchical analysis of F(ST) revealed increasing genetic subdivision with spatial scale. Minimal genetic structure within creeklines demonstrated that wet season dispersal, rather than dry season isolation, determines genetic structure at small scales. At the scale of sub-catchments, a pattern of isolation by distance along creeklines was evident. Genetic subdivision between adjacent river systems was greater between rivers separated by a plateau than by lowlands. This implies greater connectivity of populations in lowland areas and may explain the greater similarity of the east Kimberly freshwater fish fauna with lowlands to the east than with the more rugged regions to the west. Similarly, greater connectivity between lowland populations may account for the on-average larger distribution of lowland Melanotaeniids.

Biological monitoring of the impacts of the Ok Tedi copper mine on fish populations in the Fly River system, Papua New Guinea.

Monitoring of the impacts of the Ok Tedi copper mine on fish populations in the Fly River system in Papua New Guinea has recorded approx. 100 species of fish representing 32 families. Fish catches have shown considerable temporal and spatial variability but, since the commencement of mine operations and the input of mine-derived waste material into the headwaters of the system, long-term monitoring has revealed significant reductions in fish catches at most riverine sites in the Ok Tedi, upper and middle Fly River. However, no significant declines in fish catches have been recorded in the lower Fly or delta areas. Possible mechanisms accounting for the declines in fish catches in the river are discussed. Although catches in some floodplain habitats have also declined, these changes are thought to be associated with the effects of natural climatic phenomena, particularly El Nino droughts. Introduced species and increased commercial and artisanal fishing may also have had an effect. Levels of copper, zinc, lead and cadmium were found to be elevated in tissues from a range of fish species taken from riverine and floodplain sites sampled in the Ok Tedi and Fly Rivers. Metal levels were generally much higher in liver and kidney than from flesh. There was a general trend for metal concentrations to decrease with distance downstream from the mine, suggesting a mine-related effect. Significantly higher metal concentrations were recorded at 'impact' compared to 'control' sites. The intake of dietary copper by humans consuming fish taken from the river is well within guidelines set by the World Health Organisation and does not constitute a health risk. Ok Tedi Mining Limited has recently initiated a programme of mitigation works aimed at reducing the adverse effects of mine wastes on the river environment.