Chemical mediation of linkages among species at different trophic levels is an important characteristic of ecosystems. This proposal examines a sedimentary community dominated at middle trophic levels by organisms which produce toxins that influence higher and lower trophic levels. The exudation of the toxin monobromophenol by the polychaete worm Notomastus lobatus into the sediment is hypothesized to influence the activity and composition of the microbial community, recruitment of infauna, and predation/disturbance by sediment feeding predators. Experiments are proposed which examine the dose response of functional groups and the total community of bacteria to monobromophenol, allelochemical inhibition of larval settlement and adult activity of infauna, and the relationship of predator activity to the presence of monobromophenol in the sediment.
