ADAMS, Julie A.; MOORE, Paul A.; Bowling Green State University; Bowling Green State University: Foraging in a complex chemical background: DOM from elevated CO₂ detritus and its impact on crayfish orientation to a food source

Organisms extract information from the environment to make behaviorally relevant decisions. Many organisms use chemical information to perform a variety of behaviors, including the location of food resources. Crayfish orient to food sources by almost exclusively using chemoreception. These animals must locate food in a chemically complex environment where chemicals from various sources interact. We tested whether a chemical background of leachate from detritus (DOM) produced at ambient (AMB) or elevated (ELEV) atmospheric CO₂ and present at two concentrations would affect crayfish orientation behavior. Crayfish (Orconectes virilis) orientation was observed in a recirculating flume where a fish odor source was placed downstream of a DOM odor source. Treatments were: 1) Control, no DOM present, 2) AMB-3 (AMB DOM at 3 mg/L), 3) AMB-6 (AMB DOM at 6 mg/L), 4) ELEV-3 (ELEV DOM at 3 mg/L), and 5) ELEV-6 (ELEV DOM at 6 mg/L). Parameters measured were % success, time to find source (s), walking speed (cm/s), walking speed toward source (cm/s), turning angle, heading angle relative to source, heading angle relative to upstream, and net-to-gross ratio (NGR). Crayfish in the AMB-6 treatment were most successful at locating the source. In contrast, animals in the ELEV-6 treatment had higher turning angles than all treatments other than control, and had increased heading angles relative to the source and decreased heading angles relative to upstream. No differences were found for walking speed or NGR. These results indicate that crayfish orientation is affected by the presence of DOM from detritus when present at the high end of a natural concentration spectrum, and the effects differ for detritus produced at ambient or elevated atmospheric CO₂.