Gedamke, Michael (1995) Effects of grazing by two species of periwinkles on adults and juveniles of Fucus vesiculosus. (Diploma thesis), Christian-Albrechts-Universität, Kiel, Kiel, Germany, 47 pp.

Text Dipl. 1995 Gedamke, M.pdf - Reprinted Version Restricted to Registered users only Download (2MB) | Contact

Abstract

Littorina littorea and L. obtusata are believed to be important regulators of recruitment success of Fucus species on NW-Atlantic shores. The hypotheses that neither snail species alone, nor a mixture of both would exhibit a feeding preference for either adult or juvenile F. vesiculosus were tested. The experiments were conducted on a semi-exposed Nova Scotian shoreline near Halifax with a distinctly zoned intertidal vegetation. In an inclusion/exclusion caging experiment, I used single and multiple food choice treatments to determine feeding preference. At natural grazer densities, I found no significant preference for the two food types by either snail species alone or in combination. However, L. littorea at half their natural density significantly preferred juveniles. My results indicate that grazing rate by snails does not normally vary with size of F. vesiculosus. Competition was shown to be important within L. obtusata and among the two species of periwinkles, L. obtusata and L. littorea. Their competitive relationship was asymmetrical, in that L. obtusata was superior to L. littorea. L. obtusata possibly has kept L. littorea in check since its arrival on the North American continent.

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