Direct Enumeration of Marine Arenicolous Fungi

Abstract

Flotation methods were devised for the qualitative and quantitative study of marine higher fungi in sandy beach communities. Standardized clay sediment samples were centrifuged in 70% sodium metaphosphate to separate spores and hyphae from masking materials, the supernatant was diluted in a sedimentation column, and the sunken propagules counted with an inverted microscope. Samples of the water column, surface layer, sea foam and sandy substrata of two beaches, and the surface of a nearby freshwater body were examined. Marine fungi were readily demonstrable in the water column and in neuston screen samples of the ocean surface, as well as in sea foam and sand extracts. New geographical limits for several species, the seasonal distribution of tropical Varicosporina ramulosa, and the vertical zonation of Corollospora spp. were revealed. Corollospora spp. deposited by sea foam were less active physiologically than geofungi and caulicolous marine species in the upper 30 cm of the strand line, but elsewhere on the beach and in the water the reverse seemed true. The geofungi on adjacent marine and freshwater surfaces were morphologically indistinguishable and probably airborne. Marine lignicolous fungi were sparse in the beach ecosystem, although easily obtainable on incubated driftwood from the study site. The described methods were considered sufficiently sensitive and precise to merit broader application in marine mycology, and with modifications, to the aquatic Hyphomycetes as well.