Colonization and growth dynamics of three species of Fucus

Abstract

Colonization, growth and mortality of Fucus vesiculosus L., F. vesiculosus L. var. spiralis Farl. and F. distichus L. subsp. edentatus (Pyl.) Powell were investigated from August 1973 to April 1976. Grazing by Littorina littorea L. retarded but did not prevent colonization of Fucus. Growth of Fucus spp. was characterized by high variability both within and among sites. The general growth pattern consisted of slow to moderate growth during winter and early spring and rapid growth throughout summer and autumn. Growth was inversely proportional to intertidal height. Removing Ascophyllum nodosum (L.) Le Jol., and Chondrus crispus Stackh., from protected rocky shores permitted colonization and development of F. vesjculosus throughout the intertidal region. Following colonization, the mortality of F. vesiculosus gerrnlings was high. Such losses were not reflected in area cover measurements, however, because of the continued growth of surviving thalli. Mortality of large plants occurred mainly during winter, owing to ice and storm damage. This mortality, as well as a reduced growth rate, was responsible for the slow increase in algal cover during winter.