Filamentous Fungal Populations of Hawaiian Beaches

Abstract

Heterotrophic micro-organisms were studied on three Hawaiian beaches-two of volcanic origin and one of carbonate. The volcanic beaches consisted of coarse particles with little organic matter. The carbonate beach consisted of coarse-to-fine, light-colored particles and contained more organic material than the volcanic sands. Fungi populations of the three beaches differed noticeably in their tolerance to temperature, salinity, and pH. In vitro testing of selected fungi showed wide tolerance to salinity levels, less tolerance to the high temperature of black sand, and no adaptation to alkaline pH levels. Heterotrophic microbe populations were greatest in the supratidal zone, except for the intertidal bacterial population of the black sand beach. In the subtidal black zone of the carbonate beach, only bacteria were well established, actinomycetes were absent, and fungi were few. Fifty percent of the fungi were common to any two of the three beaches. Zonal decrease in numbers at all three beaches was attributed to differences in submergence time.