Water Quality Preferences of an Australian Freshwater Turtle

Abstract

Climate change and human activity are changing the characteristics of freshwater systems all over the world. Water quality is an important environmental variable to turtles, and many species have limited tolerances to different abiotic parameters. Despite the potential for extreme effects of water quality variables on turtle physiology and behaviour, we still do not understand the extent to which many species identify and select different water quality parameters within their habitats. The eastern long-necked turtle (Chelodina longicollis) resides in both natural and highly degraded systems throughout south-eastern Australia. However, their ability to perceive the quality of these environments and whether they select a habitat based on specific water quality attributes is unknown. Our objective was to identify the preferences of eastern long-necked turtles to different water quality parameters. We quantified the time spent in varying concentrations of five abiotic variables: dissolved oxygen, fertiliser, pH, salinity, and turbidity. Testing arenas consisted of four tubs, each with a different concentration of a selected water quality variable, and turtles were allowed to choose in which concentration they spent their time. This was replicated for each of the five variables, using a sample size of 10 turtles. Eastern long-necked turtles strongly preferred the freshwater control treatment over treatments with high salinity. They did not show strong preferences towards treatments with different dissolved oxygen, turbidity, and fertiliser or pH. We show that although C. longicollis occupies a variety of natural and man-made water bodies, they do prefer specific salt concentrations, which may influence their subsequent habitat selection within their range. Our trial model may also reveal stronger habitat preferences of more sensitive turtle species, which may be increasingly vulnerable to changes in their natural habitats.