Distribution of phytoplankton in some parts of Lagos Lagoon, Southwest Nigeria

Abstract

Investigations were carried out on spatial and seasonal composition and distributions of phytoplankton in some parts of the Lagos Lagoon. Phytoplankton samples were collected from twelve stations during the wet(July, 2008) and dry (March, 2009) seasons. A typical freshwater condition prevailed in the study area during wet season with salinity of 0 parts per thousand (o/oo) at every station, whereas during the dry season, relativelyhigh salinity levels were recorded from all the stations with decreasing trend toward the river mouth. The two seasons had the diatoms (Bacillariophytes) of the Orders Centrales and Pennales as the dominantphytoplankton taxa. A total of 2896 phytoplankton belonging to twenty-seven species, eight orders and four classes were recorded during wet season while the dry season had a total of 1550 phytoplankton, which cut across sixteen species, three orders and two classes. Wet and dry seasons respectively had Aulacoseira granulata and Coscinodiscus sps. as the dominant phytoplankton taxa. Higher dominance (0.33) and Margalefdiversity (3.26) but lower Shanon-Wiener diversity (1.94) and evenness of distribution (0.26) indices were recorded during the wet than dry seasons. The findings show the influence of seasonality on phytoplanktoncomposition and distributions in the Lagos Lagoon and suggest relatively stress-free environmental conditions within the study area.