Journal of Asian Scientific Research, 2013, 3(10):995-1010 995 THE PHYSICO-CHEMICAL CHARACTERISTICS, CHLOROPHYLL a LEVELS AND PHYTOPLANKTON DYNAMICS OF THE EAST MOLE AREA OF THE LAGOS HARBOUR, LAGOS Onyema I. C. Department of Marine Sciences, University of Lagos Popoola R. T. Department of Marine Sciences, University of Lagos ABSTRACT The physico-chemical characteristics, phytoplankton composition and distribution at the East mole area of the Lagos harbour were investigated between January and June, 2012. The physico- chemical conditions varied between high brackish and sea water chemistry. Records were Air (26 - 33 0 C) and Water temperatures (28 - 31 0 C), Salinity (19.40 - 30.72 0 / 00 ), Nutrients (Nitrate ≥ 3.11 mg/L; Phosphate ≥ 0.65 mg/L, Sulphate ≥ 878.6mg/L), alkaline pH (7.75 – 8.48), Transparency (141.2 - 236.5cm), Alkalinity (33 - 85.2mg/L), Conductivity (32700 – 49,600 μS/cm), Dissolved Oxygen (4.8 - 5.4mg/L) and Chlorophyll a concentrations (8.5 - 10.1mg/L). Chlorophyll a concentration was positively correlated with Salinity (r = 0.81), Total Dissolved Solids (r = 0.80), Conductivity (r = 0.81), Rainfall (r = 0.13), Phosphate (r = 0.87), Sulphate (r = 0.65), Silica (r = - 0.62), Nitrate (r = 0.10), Dissolved Oxygen (r = -0.38) and Air temperature (r = -0.61). The phytoplankton diversity consisted of three main algal groups namely - Diatoms, Blue-green algae and Dinoflagellates. A total of 32 species belonging to 18 genera were observed. Diatoms formed the more abundant group making up 22 species from 13 genera. The Blue-green algae recorded five species from three genera and Dinoflagellates with five species from two genera. In terms of diversity, the dry season (Jan. – Apr. 2012) recorded a relatively higher phytoplankton diversity (S) and abundance (N) than the wet season. In terms of diversity, the Diatoms, reported 68.75% (Centric - 50% and Pennate diatoms –18.75%), while the Blue-green algae and the Dinoflagellates recorded 15.63% respectively. In terms of phytoplankton abundance, the month of February recorded the highest outcome. The biological indices reflected a similar trend of occurrence as the species composition and distribution. Notable species were Coscinodiscus centralis, Coscinodiscus radiatus, Synedra crystallina, Trichodesmium thiebatii, Ceratium bicephalum and Oscillatoria trichodes. Keywords: Lagos Habour, Diatoms, Blue-green algae, Dinoflagellates, Algae. Journal of Asian Scientific Research journal homepage: http://aessweb.com/journal-detail.php?id=5003