Coral reef organisms are exposed to both an increasing magnitude of pCO2, and natural fluctuations on a diel scale. These fluctuations can occur from a range of biological and physical processes, including reef respiration and metabolism. For coral reef fishes, one of the most profound effects of elevated CO2 conditions is the impact on ecologically important behaviors. Previous behavioral research has primarily been conducted under static pCO2 conditions. Recent studies have provided evidence that the negative impacts on behavior may be reduced under more environmentally realistic, fluctuating conditions. I investigated the impact of both present and future day, static (500 and 1000 µatm) and diel fluctuating (500 +- 200 and 1000 +- 200 µatm) pCO2 on the lateralization and chemosensory behavior of juvenile anemonefish, Amphiprion percula. The static experimental comparisons support previous findings that under elevated pCO2, fish become non lateralized and lose the ability to discriminate olfactory cues. Diel-fluctuating pCO2 mitigated the severity of some behavioral abnormalities such as the chemosensory response, where a preference for predator cues was significantly reduced under a future diel-fluctuating pCO2 regime. This research aids in ground truthing earlier findings and contributes to the growing knowledge of the role of fluctuating conditions.
The chemosensory system of fish is used to detect chemical cues in the marine environment. Chemosensory response behavior is typically tested using a two-channel choice flume and has become a common tool to assess if specific behaviors are chemically mediated. With the number of researchers utilizing this tool increasing, it is important to determine if methodological changes impact the results generated and therefore the conclusions that can be drawn when comparing between different studies. An assessment on how methodological changes may impact the strength of chemosensory response is required to better understand the results of ocean acidification research. Using a compressed Y-maze flume and video recording all experiments, we assessed the impact of concentration, predator species, testing arena style, extended time trials, tracking method, and observer bias on the chemosensory response behavior of A. percula. Diluted chemical concentrations impacted the strength of response A. percula had to predator chemical cues, where the 10% and 25% concentrations significantly differed from the full-strength predator cue. The method of video tracking also altered the response, where tracking of the center of mass significantly differed from hand tallied recordings and tracking of the anterior extreme. This research contributes to a greater understanding of how methodological changes can alter chemosensory response behavior in a two-channel choice flume.
Vaughan M. A., 2021. Assessing the methodologies and impact of future climate conditions on the behavior of Amphiprion percula. MSc thesis, University of Delaware. 17 p. Thesis (restricted access).
