Driftwood, fixed in the field and examined with scanning electron microscopy, shows that its initial colonization is dominated by fungi. As the fungi developed mierozonally, there was a tendency for single species domination. The removal of surface tissue exposed the vessels which were colonized by filamentous fungi, some of which were sporulating.
In~'oducfionSince Barghoorn and Linder's (i944=) monograph on fungi present on immersed wood along the New England seacoast (USA), a number of studies have appeared which report on the geographic distribution of wood-inhabiting marine species (Johnson and Sparrow, 1961; Jones, 1968; Kohlmeyer, 197t). Except for a study by Kohlmeyer (t969) describing the colonization of wood panels in the deep sea, ecological considerations of these fungi have been limited largely to field notes and extrapolations from laboratory observations. The purpose of this study was to assess the extent and nature of fungal colonization of freshly collected driftwood lodged in exposed coastal waters. Data are presented which show that fungi dominate both the exposed and interior tissues and that bacteria are virtually absent from these surfaces.
Materials and MethodsThe 8 pieces of driftwood examined in this study were primarily remnants of oak lobster pots found lodged between the rocks, in an aerobic environment which was emersed only at low tide. They were obtained on 22 October, t97i from the exposed shoreline of Point Judith, Rhode Island (USA). The freshly collected specimens were fixed in vials of 4 % glutaraldehyde and immediately taken to the laboratory for processing in order to minimize post-collection changes and to preserve the microorganisms as they occur in situ. After rinsing well with distilled water, sections prepared with a razor blade were quick frozen in isopentane with liquid nitrogen, freeze dried below -60 ~ on a Pearse tissue dryer, mounted with Dueo cement containing conductive silver paint, double plated with palladium-gold to avoid excessive charging, and examined with a Cambridge S-4 scanning electron microscope.
Results and DiscussionThe type of fungal development found on the surface of oak in various states of decay is shown in Fig. 1. The undeeayed hard surface was usually populated by more than one species of fungus. In ing of the surface, the biomass became a dense mat, usually with a single species dominating, as shown in Fig. IC. In material in which the surface was in an advanced state of decay, myeelia and eonidia were usually absent, but aseoearps of fungi such as those ofLeptoshaeria orae-maris Linder were present (Fig.lD).When the surface tissue was removed tangentially with a razor blade to expose the interior vessels, lumens of all vessels examined were found to be invaded with hyphae to some extent. Dense areas of hyphal penetration were quite common, as shown in Fig. 2. Upon examining progressively magnified mierographs, the intrusion of intraeellular hyphae into the lumen (Fig. 2B) and their ramification on the surface (Fig. 2C) where they p...