|The effects of Littorina littorea L. (Gastropoda) grazing on littoral green algae in the inner Oslofjord, Norway|
Lein, T.E. (1980). The effects of Littorina littorea L. (Gastropoda) grazing on littoral green algae in the inner Oslofjord, Norway. Sarsia 65(2): 87-92
In: Sarsia. University of Bergen. Universitetsforlaget: Bergen. ISSN 0036-4827, more
Fjords; Grazing; Littoral zone; Algae; Blidingia minima (Nägeli ex Kützing) Kylin, 1947 [WoRMS]; Chlorophyta [WoRMS]; Enteromorpha compressa (Linnaeus) Nees, 1820 [WoRMS]; Gastropoda [WoRMS]; Littorina littorea (Linnaeus, 1758) [WoRMS]; Mollusca [WoRMS]; Norway, Oslo [Marine Regions]; Marine
Quantitative studies of L. Littorea and mainly Enteromorpha compressa and Blidingia minima in the polluted parts of the fjord have shown that the abundant green algal vegetation found in 1973, in 1976 and 1978 was reduced or absent from most of the localities with dense snail populations. Analysis of the density of Littorina and the occurrence of Enteromorpha (including Blidingia) indicated a negative correlation between the algae and the herbivorous snails (correlation coefficient: - 0.82). Transplantation and exclusion experiments with Littorina in the field showed that snail grazing during summer had a clear and recognizable negative effect on the occurrence and reestablishment of the algae. The snails often formed fronts which grazed the algae and generally left behind a greatly reduced algal vegetation consisting mainly of larger Fucus individuals and encrusting algae. The results indicated that snail grazing in the investigated area must have been an important factor in the reduction of littoral green algae from 1973 to 1978.