Freshwater Invertebrates' Response To Gradients Of Salinity And Turbidity: Using Preference As A Rapid Sub-Lethal Test

Australasian Society for Ecotoxicology
Publication Type:
Journal Article
Australasian Journal of Ecotoxicology, 2007, 13 (3), pp. 131 - 142
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This study investigates the use of a sub-lethal rapid toxicity testing method that allows animals to move within a concentration gradient in an attempt to measure a sub-lethal response of preference to inhabit a particular contaminant concentration. We describe a testing apparatus and trial its use in assessing the preferences of selected riverine invertebrates (collected from Victoria, Australia) for two common river contaminants, salinity and turbidity [simulated by suspended fine sediment (standardised clay, kaolin)]. For salinity preference experiments, the testing apparatus was found to be unsuitable for use with small macroinvertebrates due to the need to use vigorous aeration to mix the test solution in order to prevent horizontal stratification. However, aerated salinity preference tests were successful using the freshwater shrimp Paratya australiensis (Decapoda: Atyidae), and indicated their preference for salinity <17.6-18.8 mS/cm. This observed preference for low salinity was unchanged by acclimation to salinity of 0.1, 10 or 20 mS/cm prior to testing. A dispersion of suspended particulates was used for turbidity preference experiments, and so vigorous aeration was unnecessary. When used in this way the test apparatus was found to be suitable for testing all stream macroinvertebrates tested (nine species) and one microinvertebrate. One test species, Micronecta annae (Hemiptera: Corixidae), was observed to prefer relatively high turbidity (>200 NTU) but only when collected from one of two locations.
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