Algal cover was measured for three years at approximately monthly inte
rvals on permanent quadrats on a semi-exposed shore in SW-Iceland (lat
. 64 degrees 11'N, long. 21 degrees 46'W). Good consistency between ye
ars was found in the seasonality of abundance for many common species.
Most species start increasing their cover in March. at the same time
that phytoplankton in the region begins blooming. The cover of many sp
ecies starts decreasing more or less simultaneously in May, while some
species, notably the fucoids, continue to increase into the autumn. T
he seasonal changes in cover correlate with changes in irradiance and
nutrients but not with temperature.