A study on indigenous microalgae from sluggish tidal freshwater/brackish mangrove dominated creeks(Ito-Iwolo) emptying into Lagos Lagoon was carried out for twelve months (February 2010 – January 2011).Samples were obtained using a 55 μm plankton net towed at low speed for 10 minutes. Various physico-chemical parameters were monitored; surface water temperature, PO4-P, transparency, NO3-N, SO42- and silica concentrations. All measured chemical parameters were lower in the rainy season while surface water pH ranged from slightly acidic to alkaline (6.42–8.70), chlorophyll ‘a’ showed its highest value 0.013µg/l in the dry season. There was a remarkable change in seasonal salinity values (14.90‰ and 0.10‰) while conductivity values ranged between 0.01 and 20.00 (mS/cm) in raining and dry seasons, respectively. Microalgal flora was dominated by diatoms, which comprised of 85% of the total phytoplankton population with 75 species from 32 genera. Chlorophyta, recorded 9% and was represented by 31 species from 12 genera, while Cyanobacteria (4%) comprising of 17 species from 8 genera, and Euglenophyta, represented by one genus with 4 species recorded 2% of the total phytoplankton population.
Key Words: Creeks, Microalgae, Ito-Iwolo, Lagos lagoon, Water chemistry