Algal bloom had been a problem on the Hollingworth Lake in years’ past to the locales and the lake’s biodiversity. In order to assess the status of the lake, the lake’s phytoplankton and water quality were examined during the study period of June to August 2004) at three lake depths. 49 species belonging to 7 different classes were identified including Dinophytes
. The most representative class in terms of species richness was Dinophyceae (2species) and dominated by Ceratium hirudinella. Cyanobacteria had 13 species and was dominated by Microcytis flos aquae
, Baccilariophytes had 10 species, Chlorophytes had 15 species, Cryptophytes (4 species), Chrysophytes (2 species) and the least of the species was Euglenophyte as it contributed with lower biovolume values. The total biovolumes of the phytoplankton species including Microcystis Flos aquae
and Oscillatoria aghardii
increased progressively following the increase in temperature over the summer months with a mean level of temperature was 17°C, pH-7.72; conductivity of 0.199ms/cm and Dissolved Oxygen, 87%. When the lake’s chemical components, phytoplankton composition and phytoplankton biomass were compared with international technical standards for measurement, including the World Health Organisations’ standard for water quality and the EC Directive for good quality water, the results indicated the lake to fall within the mesotrophic-eutrophic status. At the time of this study, the lake was not susceptible to generating algal blooms.