Abstract:

The Ephemeroptera, Plecoptera and Trichoptera taxa, or “EPT” are widely used as indicators of aquatic ecosystem health due to their sensitivity to waterborne toxicants and environmental change, but are typically excluded from standardized testing as they represent a challenge to culture in the laboratory. It is critical to develop standardized methods that are representative of the most sensitive species present in aquatic ecosystems in order to accurately quantify risk and develop protective guidelines. Recently, research has begun exploring the potential of using the triangle small minnow mayfly Neocloeon triangulifer as a candidate species for laboratory-based toxicity testing. While progress has been made to develop toxicity test protocols with N. triangulifer, toxicological endpoints such as body weight, growth and survival have relatively high intra-treatment variability, which inhibit the ability to elucidate treatment effects. A methodological gap that has been identified as a potential source of variability is culturing of their preferred food, diatoms from the genus Navicula. Nutritional composition and age of the Navicula culture may influence the sensitivity of N. triangulifer to contaminates. The objective of this study was to develop a method to characterize growth curve profiles for Navicula using live cell counts. It is hypothesized that the nutritional composition (protein, fatty acid and total caloric content) of the Navicula diatom culture changes at different growth stages (lag, exponential, stationary, and death phase). N. triangulifer will be fed a diet of Navicula from each of these different growth phases. Developmental endpoints including head capsule width, body length and weight will be assessed to determine the optimal diet for these insects. While growth stages of Navicula diatoms are currently unknown, we hypothesize that feeding N. triangulifer diatoms exclusively from the exponential growth phase will optimize mayfly health.