A replica method involving the use of a polyvinylsiloxane impression material with a resin cast, particularly suitable in the study of marine biofilms, is described. The technique has advantages over other methods in that it is quick, non-toxic, non-destructive and inexpensive. Replicas of critical-point dried eggcases of the dogfish Scyliorhinus canicula (L.) (Elasmobranchii: Squaliformes) showed the replica to be true down to the size of bacteria. It was also possible to replicate larger areas such as patches of living barnacles on an intertidal rock.

The study of marine biofilms often involves the use of destructive techniques such as conventional scanning electron microscopy (SEM), histology and in vacuo spectroscopic methods (Baier & Meyer, 1986), so a single surface may not be examined repeatedly. Alternatively, the surface of interest may not be amenable to examination by standard techniques due to, for example, large size or incompatibility of the material of interest. In materials science the use of replica techniques to overcome such problems have been common (Goodhew, 1973), though techniques commonly involve the use of solvents (Loh, 1989) or silicone elastomers that may have a curing period of several hours (Gordon, 1984) and are consequently unsuitable for the study of biofilms. Scott (1982) reviewed the use of dental impression materials for field use in metallurgy and in recent years, dental impression materials have been used in the study of plant morphology (Green & Linstead, 1990). In this paper we consider the use of a hydrophilic polyvinylsiloxane impression material in the study of both microscopic and macroscopic marine biofilms.