Some Biotic and Abiotic Factors Affect Phytoplankton Functional Groups in Lake Hawassa, Ethiopia
| dc.contributor.advisor | Kifle, Demeke (PhD) | |
| dc.contributor.advisor | Fetahi, Tadesse (PhD) | |
| dc.contributor.author | Beyene, Getacher | |
| dc.date.accessioned | 2020-09-21T11:12:28Z | |
| dc.date.accessioned | 2023-11-04T12:22:38Z | |
| dc.date.available | 2020-09-21T11:12:28Z | |
| dc.date.available | 2023-11-04T12:22:38Z | |
| dc.date.issued | 7/7/2020 | |
| dc.description.abstract | The water quality of Lake Hawassa has been deteriorated due to high influent load from various sources, including effluents of a hospital, industries, hotels, and agricultural runoff, which can induce changes in phytoplankton functional groups (FGs). The functional association of algae can also be affected by the dominant zooplankton and macrophytes coverage. FGs are groups of phytoplankton species with similar ecological requirements. The FGs approach has greater effectiveness than the taxonomic method in detecting the changes in phytoplankton assemblages in relation to the predominant environmental stressors. No previous study has however been conducted on the FGs in the lake. It was hypothesized that the introduction of pollutants through the various influents of the lake and the composition and abundance of the major zooplankton groups, and the presence of Echichloa pyramidalis (emergent macrophyte) influence the FGs. The main objective of this study was, therefore, to document scientific information on the variations of phytoplankton FGs in relation to these ecological factors in Lake Hawassa, Ethiopia. Sample collection and insitu measurements of physico-chemical parameters were made monthly (April to August in 2019) from four sites. Data analyses were performed using SPSS version 20 and CANOCO version 4.5. A total of 130 species of phytoplankton were identified and classified into 18 trait-based functional groups (RFGs) and 6 morphology-based functional groups (MBFGs). SN, M, P, J, and LO were the most dominant FGs contributing for 91.17% of the total fresh weight biomass of the RFGs. III, IV, V, VI and VII, which accounted 99.0035% of the total fresh weight biomass, were the most conspicuous MBFGs. RDA analysis indicated that the RFGs SN, Lo, M, F, N, J, P, MP and D and the MBFGs III, V, VII, IV and VII were correlated significantly with electrical conductivity, DO, pH, TSS, turbidity, Secchi depth and total phosphorus (P ≤ 0.004) revealing the overriding importance of these parameters in influencing the variation of the phytoplankton FGs in Lake Hawassa. The potentially toxigenic FGs were dominant at the Macrophyte zone due to their preference for shading and water column stability. Rotifers and cyclopoid copepods were the dominant zooplankton taxa with no significant impact on the FGs. The results of this study supported our hypothesis that the biotic (the macrophyte Echinochloa pyramidalis) and the human-induced abiotic (the influents associated) factors have significant impact on the phytoplankton FGs. But, further research is mandatory to better understand the underlying mechanisms governing their interactions. The current study can have practical importance to efforts directed towards improving the water quality of the lake and may also serve as base-line information for further studies. | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/123456789/22410 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Influents | en_US |
| dc.subject | Lake Hawassa | en_US |
| dc.subject | Macrophyte | en_US |
| dc.subject | Phytoplankton Functional Groups | en_US |
| dc.subject | Water Quality | en_US |
| dc.subject | Zooplankton | en_US |
| dc.title | Some Biotic and Abiotic Factors Affect Phytoplankton Functional Groups in Lake Hawassa, Ethiopia | en_US |
| dc.type | Thesis | en_US |