Studies on the species composition, relative abundance, spatial distribution and diversity of phytoplankton assemblages in the Cross River Estuary were carried out for twenty-four months, across six (6) sampling stations. A total of 105 species of 57 genera, belonging to 5 families were observed. Bacillariophyceae (Diatom) was the most abundant phytoplankton family, constituting 71.58% of total Algal density, followed by Chlorophyceae (Green algae) with 13.84%, Cyanobacteria (Blue-green algae) with 12.69%, while Euglenophyceae (Green flagellates) and Dinophyceae (Dinoflagellates) recorded 0.88% and 1.01% respectively, of total phytoplankton abundance. Bacillariophyceae showed progressive importance from stations 1 to 6 while chlorophyceae and Euglenophyceae were more abundant in stations 1, 2, and 3. Cyanobacteria however, showed no spatial bias, whereas Dinophyceae were observed only in stations 4, 5 and 6. Bacillarlophyceae was the most dominant family, while chlorophyceae and cyanobacteria were observed to be subdominant groups. Similarity of species occurrence was generally observed in stations 1 and 2, station 3 and 4 and stations 5 and 6. Analysis of variance (ANOVA) showed significant variation (P<0.05) in community structure between stations 1, 5 and 6 whereas stations 1, 2 and 3 showed no significant difference (P>0.05) in composition of phytoplankton assemblages. High abundance of certain cyanobacteria taxa indicated environmental degradation.
Journal of Applied Sciences and Environmental Management Vol. 10(1) 2006: 89-95