No abstract

No abstract

a b s t r a c tSalinity of inland waters is affected by a range of human activities and is regarded as a major environmental contaminant in many parts of the world. Changes in salinity are well known to be associated with changes in macroinvertebrate communities of flowing waters. However, as many environmental factors co-vary with salinity, it is not known whether, and if so how, salinity causes communities to change. Being able to measure the osmoregulatory stress that individual stream macroinvertebrates are experiencing would be useful to understand if and how salinity affects their populations and thus communities. Additionally, inferring salinity stress in individual invertebrates could provide a valuable biomonitoring tool to detect the initial effects of salinity before major ecological changes have occurred. Osmoregulation in larval Chironomidae (Diptera) takes place in the anal papillae and their size is believed to be associated with osmoregulatory stress. In two laboratory experiments and a field survey in southern Victoria, Australia, we determine if the size of the anal papillae of larva chironomids is a useful biomarker of salinity stress. Experiments with Chironomus oppositus showed that the surface area of the anal papillae was similar in larva hatched across 5 egg masses collected from 3 sites but were affected by salinity treatments. Furthermore, the (transformed) ratio of this surface area to the body length of the larva was independent of the size of C. oppositus. However, for Chironomus cloacalis, this surface area differed between larva hatched from egg masses collected from the same site. The expected trend in surface area of the anal papillae relative to the size of larva (Chironomu alternans, C. cloacalis, Dicrotendipes sp., Criptochironomus sp. and Tanypodinae) was not duplicated in the field survey. It would appear that unknown factors, other than salinity, are affecting the size of the anal papillae of chironomids in southern Victoria.

No abstract

The lack of Australian species data has pragmatically led to the use of toxicological data from the Northern Hemisphere to develop water-quality guidelines. However, it is unknown whether Australian species and ecosystems are equally as sensitive and if an uncertainty factor is warranted for Australian guideline setting. In the present study, it is hypothesized that an uncertainty factor is not required. This was tested by generating species sensitivity distributions by 2 parametric methods using marine Northern Hemisphere and Australian/New Zealand data. Sufficient acute data were found for only 3 compounds: 4-chlorophenol, phenol, and ammonia. For ammonia and 4-chlorophenol, the 95% species protection levels generated with Australian and Northern Hemisphere data were essentially the same. For phenol, protection levels derived from Australian data were approximately 10-fold higher. Therefore, the derived benchmark concentration from Northern Hemisphere data should be protective. It is tentatively concluded that there is no need for an uncertainty factor when deriving water-quality guidelines for marine Australian ecosystems using Northern Hemisphere data. It is, however, noted that this is based on only 3 compounds.