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(ICV-Poland) Impact Value: 76.37, Impact Factor: RJIF 5.69
E-ISSN: 2347-5129, P-ISSN: 2394-0506

International Journal of Fisheries and Aquatic Studies

2018, Vol. 6, Issue 3, Part C

Phytoplankton community composition and nutrient conditions as an indicator of ecosystem productivity in Lake Tinishu Abaya, rift valley, Ethiopia


Author(s): Yirga Enawgaw and Brook Lemma

Abstract: The present study was undertaken to investigate the community composition and their seasonal variations of phytoplankton with respect to the changes in various environmental factors in Lake Tinishu Abaya (Rift valley, Ethiopia). Phytoplankton samples were carried out from two predefined sampling sites (central and offshore) using bottle sampling on monthly basis between January and December 2016. The abundance of phytoplankton was estimated in terms of biovolume, and it was calculated using the appropriate geometric shape of the major species. In the study, a total of 37 phytoplankton taxa belonging to 5 divisions: Bacillariophyceae (40.5%) (15-species), Chlorophyta (29.7%) (11-species), Cyanobacteria (18.9%) (7-species), Euglenophyta (5.4%) (2-species), Cryptophyta (2.7%) (1-species), Dianophyta (1-species) were identified for the first time. The total biovolume (fresh weight) of the dominant phytoplankton taxa was calculated, and it was ranged from a low value of 7.96mm3/L to a high value of 315.29mm3/L at the central station and 6.47 to 239.12 mm3/L at the offshore station. The largest biovolume of phytoplankton constituted by cyanobacteria at both stations (54% at the central station & 34% at offshore) followed by Chlorophyta at the offshore station (31%) and Bacillariophyta at the central station (22%). Euglenophyta and Dianophyta had comparatively low biovolume (10%). Microcystis aeruginosa is the most conspicuous phytoplankton, However, it comprised only 10% of the total biovolume of phytoplankton. The highest biovolume (about 75%) was constituted in the Pediastrum, Anabaena, Cylindrospermosis, Nitzchia, and Perdinium species. The phytoplankton showed seasonality with higher biovolume during the rainy season concurrently with high ambient inorganic nutrients from runoff the watershed via tributary rivers whilst low density reported during the dry season with high water transparency and relatively low ambient inorganic nutrients. Diversity parameter, Shannon index (H') ranged from a low value of 1.759 to high value of 2.098 at central and 1.741 to 2.161 at offshore sites. Thus the study lake was moderately polluted seeing that H' value. The various physicochemical factors responsible for the observed temporal variations in the physical, chemical and biological features of the lake are discussed and generalized that the lake water was fresh, well oxygenated, slightly warm, alkaline, contained more TSS, TDS, and EC, very turbid and low transparency. Most of the inorganic nutrients were relatively high and supports most of the aquatic life.

Pages: 173-186  |  2834 Views  52 Downloads

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How to cite this article:
Yirga Enawgaw and Brook Lemma. Phytoplankton community composition and nutrient conditions as an indicator of ecosystem productivity in Lake Tinishu Abaya, rift valley, Ethiopia. International Journal of Fisheries and Aquatic Studies. 2018; 6(3): 173-186.
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