ISSN: 2578-4994
Authors: Nega R*, Etisa D and Lule W
Spatio-temporal variations in microalgae distribution are widely affected by water physico- chemical factors such as To, salinity, pH, nitrate, nitrite, ammonia, silicate and IP. The effect of these factors on microalgae community changes species composition and their diversity in the fresh water ecosystem. Stratified random sampling design was conducted in Lake Babogaya of Ethiopia from 2017- 2018 to assess the spatial and temporal diversity of microalgae. 120 samples were collected in dry season (February to march), flowering season (September to November), wet season and (July to August) from Lake Babogaya. Water samples were collected seasonally from selected sites using sterile glass bottles starting from site one in offshore by considering depth and representativeness of the sample for the sites. Water temperature and pH and water transparency (SD) was determined. Lake Babogaya had the average water temperature 18.75°C during wet season, 26.6°C during flowering season, 23.55°C during dry season and SD of the lake ranged from 35cm (flowering season) to 194cm (dry season. High pH values were recorded in dry season (9.1) followed by flowering season (9.0) and then wet season (8.5) in Lake Babogaya. All sites in Lake Babogaya have consistency values of pH in all three season. A total of 52 microalgae genera/ species belonging to 7 phyla were identified at the eight sites during the three seasons (wet, flowering and dry) (Table 3). Chlorophyta was the most dominant phylum in all three seasons with 28 species representing 53.84 % followed by Cyanophyta (10 species, 19.23%) and Bacillariophyta (7 species, 13.46%). In the present study microalgae species number is high in wet season (n=39) this may be due to clarity of water (low turbidity) that transmit the light and the suitable temperature. Cloth washing, bathing and grazing site was the richest in terms of species diversity with 43 microalgae genera and followed by Adulala resort with 41 microalgae genera and youth center was the least diversed site with 22 microalgae genera. In the present study the most dominant species and the relative abundance of species in each seasons were Chrococcus (wet season) (Y=75.5, RA=18.4), Oocystis lacustis (flowering season) (Y= 123.48, RA=34.78) and Chlamydomonas species (dry season) (Y=74, RA=28.57). All the eight sites had almost same types of microalgae species. The Shannon equitability values were 0.7, 0.67 and 0.7 for wet, flowering and dry seasons respectively. The Shannon diversity indices were 3.26, 2.91 and 3.04 during wet, flowering and dry seasons respectively. In all three seasons high diversity index was showed during wet season and lower diversity was showed in flowering season. Significance difference were recorded between seasons and among sampling sites and correlation between seasons are significant at p <0.05.
Keywords: Microalgae; Spatial; Temporal; Bishoftu-Guda; Diversity
