Van Thiel, L.

Predator-prey interactions are a driving force for many identifying features of ecosystems. Predation pressure not only strongly influences population structure and distribution but also influences prey behavior. Predator avoidance behavior may play a large part in self-defense. In marine systems, there are many cases of organisms which are not capable of changing physical location as a predator avoidance technique (e.g.,, sponges, corals). In this study, Bispira variegata was used as an indicator for consumer impact on behavior in a benthic, sessile organism. Primarily, population structure (i.e. size, density) was assessed. Paired clipped and unclipped populations were used to quantify an increase of potential predators based on exposure and the impact that they may have on worm response. In order to determine the impact of predation pressure, worms were observed and video recorded to assess the distance from simulated predation that caused worms to react. There was a mean density of 12 worms m-2. The population was variably distributed with no bias towards the large nor the small end of the size range represented. There was significant difference in the number of potential predators which entered the clipped plots (p = 0.005). For the predator simulation, there was extreme variation on the distance from the simulated predator that triggered a reaction, specifically retraction. The results of this study can be used as a stepping stone for understanding the effect of predation pressure on benthic, sessile organisms by showing the impact of three-dimensional habitat as well as the behavioral reactions to simulated predation.

This student research was retrieved from Physis: Journal of Marine Science IV (Fall 2008)19: 35-39 from CIEE Bonaire.