Studies of marine epiphytic algae, Calvi Corsica. I. Determination of minimal sampling areas for microscopic algal epiphytes

Minimal sampling areas have been determined for marine Bangiophyceae and Cyanophyceaee epiphytic on Cladophora prolifera and Halopteris scoparia in Calvi, Corsica. This was done by observing the stabilization of species/area curves and of qualitative and quantitative similarity coefficients between samples of increasing size. For Cyanophyceae (studied only on Cladophora) the minimal sampling area is in the order of 15 - 38 mm2, depending on the method used. The sampling area is smaller when the quantitative similarity coefficient is used, apparently because of the rather homogeneous distribution of a few abundant taxa. For the same reason the quantitative similarity coefficient stabilizes at a high value (75 %). For Bangiophyceae on Cladophora, the area is of the order of 7 - 10 mm2, but a larger area is necessary for the quantitative than for the qualitative coefficient. The stabilized value of the quantitative coefficient is relatively low (66 %), despite the fact that the qualitative coefficient reaches 94 %. On Halopteris, by counting only on medium sized ramifications (about 100 um in diameter), one can use a sampling area as low as 0.1 - 0.5 mm2 and obtain a qualitative similarity coefficient of 100 % and a quantitative one of 80 %. This study demonstrates that techniques used for macrophytic vegetation can be applied with success to microscopic epiphytes.