Avian determinants of rocky intertidal community structure in South Africa

 

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dc.contributor.author Bosman, Alison L en_ZA
dc.date.accessioned 2014-10-11T12:21:28Z
dc.date.available 2014-10-11T12:21:28Z
dc.date.issued 1987 en_ZA
dc.identifier.citation Bosman, A. 1987. Avian determinants of rocky intertidal community structure in South Africa. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/8407
dc.description Includes bibliographies. en_ZA
dc.description.abstract Rocky islands in Saldanha Bay, southwestern Cape, South Africa, support aggregations of seabirds. Guano produced by the seabirds washed off the islands into intertidal and nearshore waters,where it provides a source of inorganic and organic nutrients. The concentrations of nutrients in intertidal rockpools at island and mainland sites in the Saldanha Bay area were measured,and the biological structures of intertidal communities at these sites were compared in the light of differences in intertidal nutrient status. Monthly measurements were made of algal production and of the growth, density, reproductive condition and mortality of the dominant intertidal herbivore, Patella granularis.The rate of intertidal algal production was enhanced on shores washed by nutrient-rich waters, and the growth rates and life-history patterns of populations of P. granularis were, in turn, modified by the increased availability of algal food. On unenriched shores rates of algal production and limpet growth and reproduction were slow. Seabirds thus influence trophic relationships between intertidal organisms, without themselves being components of the community. Islands in Saldanha Bay also support dense populations of African Black Oystercatchers Haematopus moqu.ini, which forage intertidally. Predation by oystercatchers on P. granular is resulted in a modification of limpet densities and population size structures, and a reduction in the intensity of grazing. The impact of predation was, however, modified by the presence, in intertidal waters, of nutrients from seabird guano, and the consequences thereof. It is proposed that differences in the structures of communities on rocky shores, and in the roles of processes influencing structure, might •be due, in part, to differences in the nutrient status of intertidal waters. en_ZA
dc.language.iso eng
dc.subject.other Zoology en_ZA
dc.title Avian determinants of rocky intertidal community structure in South Africa en_ZA
dc.type Doctoral Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Biological Sciences en_ZA
dc.type.qualificationlevel Doctoral
dc.type.qualificationname PhD en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Bosman, A. L. (1987). <i>Avian determinants of rocky intertidal community structure in South Africa</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/8407 en_ZA
dc.identifier.chicagocitation Bosman, Alison L. <i>"Avian determinants of rocky intertidal community structure in South Africa."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 1987. http://hdl.handle.net/11427/8407 en_ZA
dc.identifier.vancouvercitation Bosman AL. Avian determinants of rocky intertidal community structure in South Africa. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 1987 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/8407 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Bosman, Alison L AB - Rocky islands in Saldanha Bay, southwestern Cape, South Africa, support aggregations of seabirds. Guano produced by the seabirds washed off the islands into intertidal and nearshore waters,where it provides a source of inorganic and organic nutrients. The concentrations of nutrients in intertidal rockpools at island and mainland sites in the Saldanha Bay area were measured,and the biological structures of intertidal communities at these sites were compared in the light of differences in intertidal nutrient status. Monthly measurements were made of algal production and of the growth, density, reproductive condition and mortality of the dominant intertidal herbivore, Patella granularis.The rate of intertidal algal production was enhanced on shores washed by nutrient-rich waters, and the growth rates and life-history patterns of populations of P. granularis were, in turn, modified by the increased availability of algal food. On unenriched shores rates of algal production and limpet growth and reproduction were slow. Seabirds thus influence trophic relationships between intertidal organisms, without themselves being components of the community. Islands in Saldanha Bay also support dense populations of African Black Oystercatchers Haematopus moqu.ini, which forage intertidally. Predation by oystercatchers on P. granular is resulted in a modification of limpet densities and population size structures, and a reduction in the intensity of grazing. The impact of predation was, however, modified by the presence, in intertidal waters, of nutrients from seabird guano, and the consequences thereof. It is proposed that differences in the structures of communities on rocky shores, and in the roles of processes influencing structure, might •be due, in part, to differences in the nutrient status of intertidal waters. DA - 1987 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1987 T1 - Avian determinants of rocky intertidal community structure in South Africa TI - Avian determinants of rocky intertidal community structure in South Africa UR - http://hdl.handle.net/11427/8407 ER - en_ZA


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