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Paper No. 69-28
Presentation Time: 9:00 AM-5:30 PM
ASSESSMENT OF THE POTENTIAL IMPACT OF WATER QUALITY ON TURTLE HABITAT SELECTION IN AN URBAN LAKE IN PLYMOUTH, MN, USA
Freshwater systems contain ions and nutrients that have the potential to improve or diminish species habitats. In urban lakes, elevated nutrient levels are often the most prominent water quality impairment. However, excess nutrients are not always the most problematic pollutants; in particular, high levels of chloride (Cl-) can alter food web dynamics and are especially challenging to remove from lake basins. Previous studies indicate Cl- can have a negative impact on aquatic species. According to the Minnesota Pollution Control Agency, chronic (four days) and acute exposure (one day) to Cl- concentrations of 230 and 860 mg/L, respectively, is toxic to aquatic life. A major source of Cl- is road salt runoff, which warrants attention as its continued application in urban areas leads to increasing Cl- in urban lake systems. In this study, we analyzed how parameters including temperature (T), pH, dissolved oxygen (DO), oxidation-reduction potential (ORP), Cl-, nitrate (NO3-), ammonium (NH4+), and specific conductance (SC) affect the use of an urban lake by three species of turtles: Chrysemys picta bellii, Chelydra serpentina, and Apalone spinifera. We trapped and radio-located 25 individuals of each species. Eight different habitats of the lake were identified and differentiated by hydrological factors and observed turtle locations. Preliminary data suggest no adverse correlations between pH, DO, ORP, NO3-, or NH4+ and turtle locations. However, Cl- ranged from 28 to 694 mg/L and these concentrations may have negative implications for aquatic food web dynamics and utilization of lake habitats by turtles. Shallow surface water samples were collected and analyzed for acute aquatic toxicity (Delta Tox II Analyzer). Preliminary data show limited evidence of acute toxicity, but deeper waters may exhibit greater toxicity, as a positive correlation between Cl- and water depth in half of the habitats was observed. In addition, in deeper areas of the basin, the water remains stratified into two distinct layers all year with recognizable differences in pH, T, SC, and Cl-. Further analysis of the relationship between water quality parameters and aquatic species ecology (including toxicity to the aquatic organisms on which turtles feed) needs to be explored to best manage and preserve turtle populations in urban lake systems.