The structure of diatom assemblages associated with Cladophora and sediments in a highland stream in Kenya

• Published in: Hydrobiologia 2005-08, Vol.544 (1), p.55-67
• Main Authors: MPAWENAYO, B, MATHOOKO, J. M
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Bacillariophyceae; Biological and medical sciences; Cladophoraceae; Creeks & streams; Domestic animals; Dry season; Fresh water ecosystems; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Gomphonema parvulum; Habitat preferences; Habitats; Hydrologic regime; Livestock; Plankton; Rivers; Species diversity; Streams; Subsistence agriculture; Synecology; Water pollution
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/s10750-004-8333-y

Epiphytic and epipelic diatoms were collected from six sites in the Njoro River, Kenya, during the dry season between January and March 1997. Diatom assemblage descriptors, such as composition, distribution, species diversity as well as diatom habitat preferences and growth-form guilds were considered. Human activities in the Njoro River watershed included small-scale livestock keeping, subsistence farming, horticultural farming, and canning activities; all these activities have polluted the river. The diatom assemblages found in the Njoro River resembled those of polluted European rivers. The diatom assemblages in the Njoro River comprised eight families and 60 species. Epiphytic diatoms were obtained from the fronds of Cladophora (Cladophoraceae) and the assemblages were richer in species than the epipelic assemblages. Nitzschia amphibiaGrun. and Gomphonema parvulum (Kütz.) Grun. were found, either epiphytically and/or epipelically, in all the six sites. Percent similarity index showed that Ng'iria and Beeston sites, and Magadi and Turkana sites, were site pairs that were more similar in diatom composition. Habitat preferences were consistently demonstrated by the diatoms, distributing themselves into epipelic, epiphytic, and/or a combination of these two. The dominant diatom growth-form guild in the Njoro River was the biraphid guild, with the adnate guild being dominant in Mary Joy site, which was frequently disturbed by domestic animals and riparian human communities for water and laundry. This work fills a significant gap in that there is virtually no available data on diatoms in Kenyan streams for comparison. It further emphasizes the importance of macroflora in diversifying habitats of organisms and also in enhancing diversity in streams. Further research on diatom composition, distribution and growth-form guilds in relation to low and high hydrologic regimes is needed to address the role of environmental variability on diatom ecology.[PUBLICATION ABSTRACT]