Abstract

To assess phytoplankton species biodiversity in the Southern Gulf of Lake Tana, water samples were collected twice a month from eight sites for six months, from October 2010 to March to 2011. Data were analyzed and compared with one another using SPSS version 16. There were significant differences between months in phytoplankton species composition (p < 0.05). However, there was no significant difference among sites during the study period (p > 0.05). A total of 67 phytoplankton genera belonging to nine classes were recorded in the study area. The study showed phytoplankton species diversity is poor in the study area. Absence of significant differences among sites might be because there were similar human impacts in the gulf on a spatial base. In contrast to this, the significant differences among the six months might be due differences in nutrient inputs into the lake and also possibly due to human impact differences on temporal base. To conserve phytoplankton species composition so that it is sustainable at all times and sites, the local people in general and government in particular should avoid some activities on the gulf.

Key words: Algal seasonality, cyanobacteria, Ethiopia, Lake Tana, temporal variation of phytoplankton.