Frequency of viral infection in a field population of Ectocarpus fasciculatus (Ectocarpales, Phaeophyceae)

Filaments of Ectocarpus fasciculatus epiphytic on Laminaria digitarn were s ampled monthly from the rocky shore at Peveril Point, Swanage, UK, for more than a year and were screened for the presence or absence of overt viral i nfection. The mean levels of overtly infected filaments recorded per month ranged from 1.1 +/- 0.1% in June 1998 to 4.7 +/- 0.2% in February 1999. Sig nificantly higher levels of overt infection occurred during the winter mont hs, and a significant negative correlation existed between this fluctuation and the surface sea temperature. In addition, a highly significant spatial difference was determined in the overt infection incidence on six reef fac es.