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 tested for effects on larval attachment of Bugula neritina (Linnaeus) in three experiments. Confluent films of four bacterial isolates significantly inhibited larval attachment of B. neritina. A fifth isolate inhibited B. neritina attachment in two of three experiments, while the sixth isolate had no effect on attachment of B. neritina larvae. Results of additional experiments employing Petri dishes filmed by bacteria on one half of the dish bottom suggest both soluble and surface film factors are involved in mediating larval settlement. Aqueous extracts of two bacterial strains inhibited bryozoan settlement in each of the three replicate assays and were toxic to larvae. A final series of experiments tested paired bacterial films and leachates for direct comparisons. 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 water-soluble compounds released from bacterial films are responsible for settlement inhibition.