Original Articles

Microalgal food resources and competitive interactions among the intertidal limpets Cellana capensis (Gmelin, 1791) and Siphonaria concinna Sowerby, 1824

Published in: South African Journal of Marine Science
Volume 13, issue 1, 1993, pages: 97–108
DOI: 10.2989/025776193784287419

Abstract

Competitive interactions between two species of intertidal limpets, Cellana capensis and Siphonaria concinna, were investigated experimentally during winter/spring and summer/autumn on a rocky shore in the Dwesa Nature Reserve, Transkei. The influence of the availability of microalgal food resources on these interactions was also examined. Intraspecific increase in density resulted in reductions in growth and tissue mass of C. capensis and increased mortality of both species. Sublethal effects of competition on S. concinna were not studied. Survivorship and growth of C. capensis were not significantly affected by the presence of S. concinna. Interspecific effects on tissue mass, however, were noted, particularly at high densities; they were attributed to interference competition. Inclusion of C. capensis in enclosures did not affect mortality of S. concinna. The intensity of interactions varied seasonally, highest mortalities and the greatest reduction in growth and tissue mass being observed during summer/autumn. Considerable variation in the level of chlorophyll a measured within enclosures reflects major differences in the feeding methodologies of the two species, differences that are undoubtedly a major factor in determining the outcome of competitive interactions between these species.

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