Optimization of settlement of larval Argopecten purpuratus using natural diatom biofilms

Larval settlement is a critical stage in the artificial production of Argopecten purpuratus. The study investigated the feasibility of improving post-larval settlement of this species using a substrate (cultch) that was pre-treated with a biofilm of native diatoms. Four species of diatoms were isolated from the surface of collectors that had high numbers of juvenile scallops (spat). These four species were able to attach themselves and grow on a polystyrene substrate. Scallop post-larval settlement was evaluated experimentally in two ways: (1) laboratory experiments in 10-L buckets: and (2) under natural condition by in situ experiments at the Marine Reserve "La Rinconada" (Antofagasta, Chile). Effects of biofilm treatments were examined using collectors that were coated with diatoms and collectors handled using normal culture methods (new netlon held in filtered seawater that did not have a biofilm). Results of the laboratory experiments showed a higher percentage of A. purpuratus post-larval settlement on collectors coated with Fragiliaropsis pseudonana compared with control collectors (P > 0.05). Results comparing biofilms of the diatoms F. pseudonana and Navicula veneta showed higher settlement on collectors pretreated with N. veneta (1,156± 172 spat per collector^-1). Statistical analysis showed that the addition of diatom biofilms enhanced spatfall and always produced larger settlement compared with untreated collectors. These results indicate that addition of cultured diatom biofilms improves scallop larval settlement.