Floristics, phenology, and ecology of the sublittoral marine algae in an unstable cobble habitat (Plum Cove, Cape Ann, Massachusetts, USA)

The floristics, phenology, and ecology of the sublittoral benthic marine algae in an unstable cobble habitat (Plum Cove, Cape Ann, Massachusetts, USA) were studied. Monthly collections (November 1981–October 1982) were made using SCUBA at 4–5 m MLW. Seventy-two species (three Cyanophyta, 12 Chlorophyta, 20 Phaeophyta, and 37 Rhodophyta) were identified. Crustose and turf algae dominate the cobbles. Crustose algae are reproductive throughout the year and upright species are invariably immature and nonreproductive. The ecology of crustose algae in this habitat does not conform to functional-form models as currently presented. The instability of the cobbles appears to determine the composition and life-form of the dominant algal species. These results emphasize the role of physical disturbance in structuring algal communities on unstable substrata.