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Epiphytic diatoms associated with a submerged macrophyte, Vallisneria aethiopica, in the shallow marginal areas of Sanyati Basin (Lake Kariba): A preliminary assessment of their use as biomonitoring tools
Phiri, C.; Day, J.; Chimbari, M.; Dhlomo, E. (2007). Epiphytic diatoms associated with a submerged macrophyte, Vallisneria aethiopica, in the shallow marginal areas of Sanyati Basin (Lake Kariba): A preliminary assessment of their use as biomonitoring tools. Aquat. Ecol. 41(2): 169-181. dx.doi.org/10.1007/s10452-006-9073-z
In: Aquatic Ecology. Springer: Dordrecht; London; Boston. ISSN 1386-2588, more
Peer reviewed article  

Available in Authors 

Keywords
    Associated species; Bioindicators; Diatoms; Ecosystem disturbance; Environmental monitoring; Zambia, Kariba L. [Marine Regions]; Zimbabwe, Kariba L. [Marine Regions]; Marine

Authors  Top 
  • Phiri, C.
  • Day, J.
  • Chimbari, M.
  • Dhlomo, E.

Abstract
    Diatom assemblages attached to the leaves of the submerged macrophyte Vallisneria aethiopica in the shallow waters of the Sanyati Basin in Lake Kariba were analysed to assess their response to human impact. Human activities occurring within approximately 500 m of the shoreline were assessed at ten sampling sites along the shores of the basin. Eleven human activity factors were assessed and scored on a scale of 0 (not occurring at the site), 1 (low), 2 (medium) and 3 (high). Based on these 11 factors, we obtained a total score for the sites, which were then categorized as either having no human disturbance (0), low human disturbance (1-11), medium human disturbance (12-22) or high levels of human disturbance (23-33). Three sites were categorized as having no human disturbance, one had low disturbance and six had medium level human disturbance. A total of 9993 diatoms belonging to 40 genera were identified. The most abundant genera were Achnanthidium and Gomphonema, which made up 23.4 and 42.9% of the total diatom count, respectively. Achnanthidium dominated in remote areas with minimal human activities, while Gomphonema was more abundant in areas adjacent to increased human activities. The relative abundances of Achnanthidium, Denticula, Pinnularia, Rhopalodia and Stauroneis were negatively and significantly correlated, while that of Gomphonema was positively and significantly correlated to the human disturbance score (Spearman correlation, P < 0.05). Although the number of genera, the Shannon Diversity Index and evenness did not differ significantly among sites (ANOVA, P > 0.05), the lowest levels of these descriptors of community assemblage occurred at sites located near areas with relatively high human activities. The abundances of Achnanthes, Cymbella, Denticula, Encyonema and Pinnularia, Bacillaria and Mastogloia, Diatoma and Navicula and Eunotia and Mastogloia significantly decreased with increasing levels of total phosphorous, nitrate-nitrogen (N), ammonium-N and water turbidity, respectively (Spearman correlation, P < 0.05). Of the16 diatom index of biotic integrity (DIBI) metrics, 11 were significantly correlated with at least one of the environmental variables, while nine metrics were significantly correlated with the composite DIBI. Among the environmental variables the disturbance score was the only one that was significantly correlated with the DIBI. We conclude that although there is need for further work, periphytic diatoms associated with V. aethiopica may potentially be useful in assessing ecological conditions or the impact of human activities within the shallow marginal waters of Lake Kariba.

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