Darby Pochtar

Project Title: THE EFFECTS OF BOAT NOISE ON RESOURCE COMPETITION IN THE BLUE CRAB (Callinectes sapidus)

Mentor: Jason Krumholz

Abstract: Marine noise has been shown to negatively affect marine invertebrates.  These affects range from increased stress level, to physical injury, to communication masking, to an increase in distraction.  It has been found that marine invertebrates are able to detect frequencies of 10s to 100s of Hz, but it is suspected that they can be affected pressure waves or particle motion past this range.  There is very limited data on how exactly boat noise impacts the behaviors of invertebrates.  As part of a larger experiment on the impact of sound on invertebrate physiology and behavior, we exposed subadult blue crabs (Callinectes sapidus) to simulated boat noise (broadband, low frequency with peak level approximately 170dB re 1Pa @ 60Hz) to determine whether exposure would alter interspecific resource competition with green crabs (Carcinus maenas).  After 24 hours post exposure, control and sound-treated C. sapidus competed with unexposed C. maenas for food, as well as for shelter in an experimental arena.  Trials were videotaped for analysis with the behavioral software Ethovision and a variety of behaviors and interactions types were recorded for each trial.  The behaviors were then categorized as dominant fighting, dominant food, submissive, or neutral behaviors.  We found that there was a significant increase in dominant fighting behaviors (p < 0.05) and a significant decrease in dominant food behaviors (p < 0.05) in the exposed blue crab in comparison to the unexposed blue crab.  Particularly given the short duration of our experimental exposure, our results highlight the importance of understanding the impact of low frequency, especially boat noise, sound on marine animal behavior and competition.