SETTLEMENT INHIBITION OF BRYOZOAN LARVAE BY BACTERIAL FILMS AND AQUEOUS LEACHATES

Six strains of marine bacteria were isolated from benthic algal films and subtidal rocks. Films and aqueous leachates of isolates were teste d for effects on larval attachment of Bugula neritina (Linnaeus) in th ree experiments. Confluent films of four bacterial isolates significan tly inhibited larval attachment of B. neritina. A fifth isolate inhibi ted B. neritina attachment in two of three experiments, while the sixt h isolate had no effect on attachment of B. neritina larvae. Results o f additional experiments employing Petri dishes filmed by bacteria on one half of the dish bottom suggest both soluble and surface film fact ors are involved in mediating larval settlement. Aqueous extracts of t wo bacterial strains inhibited bryozoan settlement in each of the thre e replicate assays and were toxic to larvae. A. final series of experi ments tested paired bacterial films and leachates for direct compariso ns. For certain isolates, the film inhibited settlement and the water soluble-leachate had no effect on settlement. Other isolates displayed opposite results. These results suggest both surface properties and w ater-soluble compounds released from bacterial films are responsible f or settlement inhibition.