The need for biological assessment of water quality: Australian perspective

Abstract Biological assessment of water quality in Australia is entering a stage of rapid development largely because of the inclusion of biological indicators in water quality guidelines and growing concern for ecological values. Approaches to water quality assessment include toxicity testing, use of biomarkers and several methods using community structure. For assessment diverse organisms such as fish, algae and (the most commonly used) macro-invertebrates are used. Interaction of data analysis with methods of data collection requires co-ordinated research on both fronts. Recent developments in the use of multivariate statistics to produce models for predicting water quality are likely to be useful in Australia. Much innovative work is still needed in Australia on the use of algae and fish, defining tolerance categories and establishing monitoring programmes performed in time-frames equivalent to those in use for physical and chemical methods.     

The contribution of artificial nest experiments to understanding avian reproductive success: a review of methods and conclusions

Artificial nest experiments have been used in approximately 80 recent studies to identify a wide range of factors influencing reproductive success of birds. Despite the same factors being examined in different studies, few consistent patterns have emerged from these experiments. Analysis of reproductive success at artificial and natural nests reveals that reproductive success measured with use of artificial nests is frequently underestimated. In addition, several studies suggest that different species of predators may be differentially attracted to the two types of nest. These results call the utility of artificial nests into question as a tool for elucidating factors influencing the success of natural nests. Analysis of the methodology used in artificial nest experiments reveals that in general there is poor correspondence between the appearance of experimental setups and the natural systems they attempt to model. If future experiments with artificial nests are to contribute to theory, the quality of experiments must improve and the assumptions underlying the artificial approach must be tested. Collecting this information will be relatively simple compared with the time-consuming task of experimenting with natural nests. Until these data are collected, conclusions about nesting ecology derived from the use of artificial nest experiments should be treated as preliminary.     

Induced resistance of Gossypium australe against its most abundant folivore,Bucculatrix gossypii

Induced resistance of cultivated Gossypium to its exotic, agricultural pests is well studied but little is known about whether native cottons respond to damage by endemic herbivore populations. This study examined induced responses of Gossypium australe to its most abundant folivore, Bucculatrix gossypii. Prior damage did not affect the number of new mines initiated. Survival of miners on damaged, young leaves and cotyledons was reduced compared with survival on young leaves and cotyledons of undamaged plants. However, the induced resistance was not systemic; survival of miners on older, undamaged leaves of damaged seedlings was not different from survival on older leaves of undamaged controls. This localized induced resistance did not produce an overdispersed distribution of either mines or successful mines. On the contrary, the distributions tended towards clumped, although they were not statistically distinguishable from random. Although a localized induced response affected miner survival, no effects on behaviour were observed.     

Experimentally increased soil temperature causes release of nitrogen at a boreal forest catchment in southern Norway

Boreal forest ecosystems are sensitive to global warming, caused by increasing emissions of CO₂ and other greenhouse gases. Assessment of the biological response to future climate change is based mainly on large-scale models. Whole-ecosystem experiments provide one of the few available tools by which ecosystem response can be measured and with which global models can be evaluated. Boreal ecosystem response to global change may be manifest by alterations in nitrogen (N) dynamics, as N is often the growth limiting nutrient. The CLIMEX (Climate Change Experiment) project entails catchment-scale manipulations of CO₂ (to 560 ppmv) and temperature (by + 3 to + 5 °C) to whole forest ecosystems in southern Norway. Soil temperature is increased at 400-m² EGIL catchment by means of electric cables placed on the soil surface. Soil warming at EGIL catchment caused an increase in nitrate and ammonium concentrations in runoff in the first year of treatment. We hypothesize that higher temperature increased N release by mineralization. Whether these responses are only transient will be shown by additional years' treatment.     

THE FERTILIZATION CANAL IN PLODIA INTERPUNCTELLA (HÜBNER) (PYRALIDAE: LEPIDOPTERA)

The spermathecal duct of Plodia interpunctella (Hübner) was studied with light and transmission electron microscopy. The lumen in the duct is enclosed by a thin chitinous wall that has a thicker band that spirals along the length of the duct. The thick spiral band pinches off part of the lumen and creates a smaller canal, which it encloses. Although the two canals are not separated, the duct appears to have a double lumen. The thin wall of the main canal provides a flexibility in which the lumen widens or narrows concomitantly with contractions of the spermatheca and the portion of the duct adjoining the spermatheca. Sperm is transferred from the spermatheca to the vestibulum where the egg is fertilized. The distention of the canal and contractions of the spermatheca thus account for the speed at which eggs are fertilized and deposited.