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

Abstract

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 amphibia Grun. and Gomphonema parvulum (Ku¨tz.) 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.

Geothermal Diatoms: Seasonal Variability in the El Tatio Geothermal Field (Altiplano, Chile)

“…However, these aspects in microbial communities are poorly know especially in extreme environments. In New Zealand, according to [7] 144 taxa in thermal and mixed thermal/non-thermal waters were dominated by the genera Nitzschia (24), Pinnularia (16), Navicula (10), and Surirella (7). In this work, we reported 102 taxa in thermal and mixed thermal/non-thermal waters dominated by the genera Nitzschia (16), Navicula (13), Gomphonema (7), Planothidium (6), and Denticula (5).…”

“…Angel [10]. Other diatom floras were described in hot-spring systems of Iceland, New Zealand, and Kenya [6].…”

Recent views on river pollution and diatoms

“…Passy et al (1999) showed that compared with epiphyton, epilithic diatoms had the lowest correlation with ionic strength and eutrophication. Tests performed on epipelic and epiphytic diatoms in Kenyan rivers (Mpawenayo & Mathooko, 2005) showed a decrease of adnate diatoms in both habitats when pollution increased. One way to homogenize the substrates effect is to use artificial substrates (Maznah & Mansor, 2002;Dela-Cruz et al, 2006;Duong et al, 2006;Ndiritu et al, 2006), although Fisher & Dunbar (2007) showed that diatom communities and biomass between natural and artificial substrates were quite different.…”

A review of the alien and expansive species of freshwater cyanobacteria and algae in the Czech Republic

“…In North America, it is a frequently detected in streams (Brian 2000;Hill et al 2003;Johansen et al 2007;Potapova and Charles 2007;Ratnasabapathy and Deason 1977;Stoermer et al 1999;Waite et al 2006;Wunsam et al 2002), and it is also found in the marine intertidal zone at the water's edge or on river estuaries (Patrick 1994). F. weinholdii was also observed in Cuba (Marvan unpublished), in inland waters of Australia (Day et al 1995), and in a highland stream in Kenya (Mpawenayo and Mathooko 2005 Non-native distribution in the world: The nonnative distribution of F. weinholdii is unknown.…”