Abstract:
The effect of rising salinity levels on freshwater ecosystems is of concern in many parts of the world, including
Australia and southern Africa. Most studies on the salinity tolerance of freshwater macroinvertebrates only
consider older life-stages, which are suspected of being more tolerant than early life-stages, such as eggs and
hatchlings. The salinity tolerances of ten taxa from south-east Australia and two taxa from South Africa, to the
artificial seawater, Ocean Nature, were investigated. From the Barwon River in south-west Victoria, the following
taxa were tested Amarinus lacustris (Hymenosomatidae), Paratya australiensis (Atyidae) Physa acuta
(Physidae), Lymnaeidae, Plectrocnemia sp. (Polycentropodidae), Anisocentropus sp. (Calamoceratidae), Hydrobiosidae,
unidentified Polycentropodidae and Dinotoperla thwaitesi (Gripopterygidae). Chironomus tepperi
(Chironomidae) from a laboratory colony stocked from central New SouthWales was also investigated. The South
African limpets Burnupia stenochorias (Ancylidae) were collected in the Eastern Cape and shrimps Caridina
nilotica (Atyidae) from a colony stocked from Kwazulu-Natal were studied. The salinity tolerances of the eggs and
hatchlings ranged from 0.8 to >47 mS cm−1 with a mean of 17 mS cm−1. Where reliable estimates are available,
the eggs or hatchlings had a salinity tolerance between 5% and 100% of the 72-hour LC50 of older stages, although
for insects this was <50%. This study has thus confirmed that salinity tolerances of young stages can be less than
the acute tolerances of older stages.
