The tissues of wild mammals and birds from uncontaminated environments generally contain from ~0.1 to 5 μg nickel∙g dry weight−1, whereas in Ni-polluted environments, tissues accumulate from -0.5 to 10 (mammals) and -0.5 to 80 (birds) μg nickel∙g dry weight−1. The highest concentrations in these ranges are usually associated with tissues directly exposed to the external environment (fur, feathers, skin). Bone frequently contains higher Ni concentrations than other internal tissues. Ni concentrations in the most commonly analysed internal organs (liver, kidneys) range from nondetectable to about 3 μg∙g dry weight−1, the kidneys often containing higher concentrations than the liver. There is some evidence that birds may tend to accumulate higher Ni burdens in polluted habitats than do mammals. For mammals, reduced growth and survival occur in response to chronic exposure to 500–2500 μg Ni∙g diet−1 (10–50 mg∙kg body weight−1∙d−1). Effects on reproduction and essential trace metal (especially iron) metabolism have been reported at levels as low as 5 μg∙g−1 in food or drinking water (0.2–0.4 mg∙kg body weight−1∙d−1), but these findings have not always been corroborated. Toxicological data on birds are more limited than those pertaining to mammals. Newly hatched chickens suffered reduced growth rates when fed ≥300 μg∙g diet−1, and chicks began to die when fed diets containing ≥500 μg∙g−1. In newly hatched mallard ducklings, chronic exposure to ≥800 μg∙g diet−1 resulted in ataxia, tremors, and significant mortality, whereas adult mallards fed 800 μg∙g−1 showed no evidence of systemic or reproductive toxicity. Tissue concentrations of Ni were not reliable indicators of potential toxicity in either mammals or birds, because significant effects, including mortality, frequently occurred in the absence of elevated tissue Ni concentrations. However, when there is evidence of elevated tissue Ni concentrations (>10 μg∙g−1 in the kidneys, and (or) >3 μg∙g−1 dry weight in the liver), Ni exposure sufficient to cause significant toxic effects should be suspected. Nickel has been reported in aquatic macrophytes and lower plants (but not in invertebrates or zooplankton) in the vicinity of Ni smelters in Canada in concentrations that approach or exceed dietary levels known to cause adverse effects in young animals. Sensitive species of wildlife ingesting this vegetation for considerable periods of time could experience Ni-related toxicity. In addition, wildlife food chains involving aquatic organisms (plants, invertebrates, fish) risk alterations in community structure in Ni-contaminated environments as Ni-sensitive taxa are eliminated or their abundance is reduced.Key words: nickel, toxicology, wildlife.

Aspects of physicochemical limnology and the zooplankton, littoral invertebrates and fish of dune lakes on Fraser Island are described and compared. The comparisons highlight differences between perched, humic lakes and the non-humic Lake Wabby, a water-table window with some morphometric and biological features typical of dune barrage lakes. Lake Wabby has been partially infilled by a mobile sand dune moving mainly in a north-westerly direction across the northern end of the lake. The maximum rate of dune advance estimated from aerial photos was 5.03 m year-1, between 1948 and 1958. Sand infilling between 1975 and 1984 altered the morphometry and substrate characteristics of the lake's eastern region and reduced maximum depth from 13.0 to 11.5 m and volume by 43%. The number of benthic invertebrates was reduced from 14 taxa in 1975 to six taxa in 1984; there was also a significant decrease in abundance of benthic Chironomini during this period (ANOVA, P < 0.05). In both years, an undescribed species of Conochironomus was the most abundant benthic invertebrate in Lake Wabby (250-700 individuals m-2). A new genus of Chironomini (near Paralauter borniella) was discovered. Lake Wabby supported 11 species of fish in 1975 and 1984, but the perched lakes had only one or two species. The five most abundant species in Lake Wabby in 1975 showed evidence of partitioning of food resources, of which the main components were benthic invertebrates and filamentous algae. Allochthonous food resources were not important in fish diets. The possible long-term effects of sand infilling on food resources, fish diets and the composition of the zooplankton in Lake Wabby are discussed.

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This study examined seasonal and spatial patterns of benthic macroinvertebrate communities in four billabongs and a perennial stream riffle in the Magela Creek catchment, Northern Territory. Chironomids, coleopterans, trichopterans and hydracarina were the most diverse and abundant taxa, although the mussel Velesunio angasi contributed over 98% of total standing crop in most billabongs. Diversity and standing crop were usually higher in littoral than in profundal areas of two shallow billabongs, probably because of the presence of macrophytes. Diversity, abundance and biomass declined sharply over the dry season, from maxima in May-July to minima in December. Recovery in the early wet season was rapid, commencing after the first creek flows in December. The decline and recovery were closely associated with the availability of sediment organic matter, which reflected inputs of mainly allochthonous (terrestrial) detritus over the wet season followed by losses due to intense microbial breakdown. Microbial respiration also seemed related to declines in benthic communities in the latter half of the wet season, by producing hypolimnetic anoxia during periods of reduced creek flow.

A total of 133 benthic macroinvertebrate species was recorded in four permanent freshwater lagoons (billabongs) and a stream riffle in the Magela Creek catchment, Northern Territory, Australia. 101 species were lentic in occurrence. Each billabong supported at least as many species as larger tropical and Australian temperate lakes, and was an exception to the species-poor status of Australian lentic macrobenthic communities.> 98% of the total benthic biomass was contributed by a mussel species; the remaining species' combined standing crop was an order of magnitude lower than in other lentic systems, further highlighting the diversity of the Magela benthos. Rarefaction (removal of organisms) and predictable environmental heterogeneity, both related to monsoonal variations in flow and water quality, were probably important determinants of the high diversity of these communities.