Seaweeds as a reservoir of Candida yeasts in inshore waters

The yeast populations on 9 species of seaweeds and in seawater were estimated by cultural methods over a 16-month period in Narragansett Bay, Rhode Island (USA). Maximal numbers occurred on rhodophytes and a chlorophyte, while the lower numbers on phaeophytes were attributed to the release of inhibitory polyphenolic materials. All divisions of algae showed a similar seasonal variation in yeast populations, correlated with trends in solar radiation and water temperature which would affect both the host and its microflora. The exposure of intertidal algae to unseasonable air temperatures apparently has a detectable effect on their microflora. The population changes in the water surrounding the seaweeds paralleled those on the plants. Only colorless yeasts of the genus Candida were observed, except for brief occurrences of the pink yeast Rhodotorula in late spring, when it accounted for 3 to 35% of the yeast community. Ninety five percent of the 362 representative isolates were strains of Candida. The published properties of the 84 species accepted in the genus Candida were compared with those of the marine isolates using numerical analysis. There were 7 groups: 1 solely of named species, 3 small groups with both named species and marine isolates, and 3 large groups with only one or two named species that contained 75% of the seaweed and sea-water isolates. An apparent successional sequence for three groups may be due to differences in their biochemical activity. The same three groups were preferentially enriched by 5 of the algal species. The role of this persistent yeast population as a reservoir of inshore yeasts is discussed.