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Distribution ecology and the impact of human activities on some Gracilaria species of the Kenya coast
Oyieke, H. A. (1995). Distribution ecology and the impact of human activities on some Gracilaria species of the Kenya coast, in: Coastal systems and sustainable development in Africa. Proceedings of a UNESCO regional seminar on human impacts on coastal ecosystems, their response and management problems ROSTA, Nairobi, 5-9 April 1993. UNESCO Reports in Marine Science = Rapports de l'Unesco sur les sciences de la mer, 66: pp. 139-147
In: (1995). Coastal systems and sustainable development in Africa. Proceedings of a UNESCO regional seminar on human impacts on coastal ecosystems, their response and management problems ROSTA, Nairobi, 5-9 April 1993. UNESCO Reports in Marine Science = Rapports de l'Unesco sur les sciences de la mer, 66. UNESCO: Paris. vii, 187 + annexes pp., more
In: UNESCO Reports in Marine Science = Rapports de l'Unesco sur les sciences de la mer. UNESCO: Paris. ISSN 0253-0112, more

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Keywords
    Distribution; Ecology; Human impact; Gracilaria Greville, 1830 [WoRMS]; ISW, Kenyan Coast [Marine Regions]; Marine

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  • Oyieke, H. A.

Abstract
    The genus Gracilaria belongs to the group of seaweeds that are of commercial value and are being harvested worldwide for their active ingredient agar. A pre-requisite for the harvesting of these plants, which has often been ignored, is a study on their ecological requirements within an ecosystem which leads to better understanding of the plants and hence good management practices and conservation in cases where wild stocks are harvested. With this aim in mind a study on the distribution ecology of 8 different Gracilaria species: sp. was carried out along the Kenyan coast extending from the North-coast to the South-coast border. In the study rocky platforms with their reef edges exposed to the open sea had a wider variety of species than either rocky platforms in sheltered waters or sandy beaches (the mean number of species per site being 3.6 ± 0.8, 1.4 ± 0.5, 2.0 ± 0.7 respectively). With regard to the frequency of occurrence in all the 23 stations studied the most common species was G. salicornia followed by G. corticata and G. crassa. G. verrucosa, G. edulis and Gracilaria sp. were less common while G. millardetii and G. fergusonii were rare. The plants were observed to grow in varied types of habitat and microhabitats in the eulittoral zone which included rocky coral platforms with their associated lagoons, pools and fringing reefs, sandy beaches and mangrove swamps. G. salicornia tended to show no specific ecological niche as it was observed in all the habitats and microhabitats studied while the rest of the species were more specific in their niche requirements. The threat that human activities impose upon these plants is discussed.

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