Henry's law constants (kO) and equilibrium concentrations (CO*) of dissolved oxygen (DO) at 1 atm were measured in NaCl solutions of concentration (S) up to -260%~ and at temperatures (7') between 273 and 308K. An equation of the form In Co* = a, + $ + a,ln T + a,T + a,T2 + S(a, + a,T + a7P) + asS2 was found to predict DO values to within the experimental uncertainty. An equation of the same form satisfactorily described the variation of In kO over the same temperature and concentration ranges. In order to develop these equations it was also necessary to develop ones to describe the variation of density and vapor pressure of NaCl solutions with T and S. The equations can be used to generate tables of oxygen solubility values that can be used for hypersaline waters dominated by NaCl. Theoretically, DO values based on NaCl can be corrected for the presence of other ionic salts in natural waters. At present this correction is limited by the availability of DO data for these subdominant electrolytes.It is a century since L. W. Winkler published his pioneering studies on the solubility of oxygen in water. Since then, equilibrium concentrations of dissolved oxygen (DO) in marine and estuarine waters have been measured over a range of salinity and temperature with his technique or minor modifications of it. In these saline waters, as well as in freshwaters, his basic technique has become the standard to determine the concentration of DO, and tables are available that document the relationship between salinity, temperature, and DO at equilibrium in such waters ' (Weiss 1970;Benson and Krause 1980; Mortimer 198 1). It is only relatively recently that other methods of measuring DO have been developed; they involve diffusion to a reducing electrode. They have not supplanted Winkler's method where simplicity and accuracy are important.

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Culex quinquefasciatus Say (Diptera: Culicidae) is an abundant urban mosquito that is the vector of filariasis. Breeding in septic tanks, where there are very high levels of bacterial food, it is likely to have a different reaction to crowding compared with other mosquitoes. To test for the presence and type of crowding effects, four larval densities of C. quinquefasciatus varying from 0.4 to 3.2 larvae ml−1 of water were reared in tubes. Mortality was found to greatly increase at densities above 0.8 larvae, whereas larval duration increased even above 0.4 larvae ml−1. Changing the water in the tubes daily gave a small (but significant) response in reducing mortality and larval duration. However, when larvae kept at a low density shared the same water with larvae at high density, there was no chemical influence on their growth rate and mortality. The effect of crowding was primarily due to physical disturbances between larvae. When larvae were kept at a high density in the same volume of water, but in shallow trays with a large surface area and therefore much less contact between them, mortality was the same as for the lowest density. There was still, however, a significant increase in larval duration from 8.6 days at 0.4 larvae ml−1 to 12.1 days at 3.2 larvae ml−1. It is therefore concluded that the larvae respond to physical rather than chemical factors by prolonging larval development and having some increase in mortality.

Lake Eyre South, a large and normally dry playa in central Australia, filled with water in January 1984. Water persisted until January 1985. Salinity rose between these dates from -25%o to > 270%o. Monthly observations on the fauna were made to determine if it consisted of widely dispersed species, and thus to test the assumption that episodically filled salt lakes are unimportant as evolutionary loci for the fauna of salt lakes. It was concluded that most species in the lake were indeed widely dispersed. Particularly common components of the fauna were: Craterocephalus eyresii (Steindachner) (fish), an undescribed species of Diacypris (ostracod), Moina baylyi Forr6 (cladoceran), Tanytarsus barbitarsis Freeman (chironomid), Parartemia minuta Geddes (anostracan), and Microcyclops platypus' (Kiefer) (copepod).

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