Pollution effects on littoral algal communities in the inner Oslofjord, with special reference to Ascophyllum nodosum

Abstract

1. Littoral algal vegetation was studied at three localities in the inner Oslofjord; one in the Drøbak area, and two in the more polluted inner basin. 2. Regrowth and succession on cleared strips were followed for 16 months. 3. The phaeophycean Ascophyllum nodosum was a common species in the inner part of the fjord at the turn of the century, but has disappeared with increase in pollution. 4. Well-grown specimens of Ascophyllum nodosum were transplanted from the Drøbak area to the inner basin. No essential differences in vegetative growth and maturation of generative structures were observed. 5. Growth and development of Fucus distichus ssp. edentatus were followed from the state of germlings to fertile plants. 6. Regrowth proceeded more slowly in the Drøbak locality than in the localities in the inner basin, where a dense carpet of Enteromorpha spp. etc. was formed. 7. It is assumed that the increased competition for substrate and the shading effect of the Enteromorpha carpet reduces the chances of Ascophyllum nodosum germlings of becoming established in the inner basin. © 1973 Biologischen Anstalt Helgoland.