Phytoplankton Composition and Abundance in Sombreiro River, Niger Delta, Nigeria

The phytoplankton composition and abundance in Sombreiro River, Niger Delta, Nigeria was studied for a period of two years (August, 2007-July2009) using filtration technique. 25 μm mesh size plankton net was towed from a dugout boat at about 5 -105–1 for about a minute. The net content was washed out into a wide mouth plastic container and preserved in 10% formalin solution after proper labeling. This was stored in a cool box and taken to the Laboratory.The samples were allowed to stand for at least 24 h in the laboratory for the phytoplankton to settle before the supernatant pipetted to concentrate the samples. The concentrated sample was agitated to homogenize before pipetting 1ml sub sample with sample pipette . The content was placed in a sedge Wick-Rafter plankton - counting chamber and examined with Leltz-Wetzlar binocular microscope at a magnification of 200x. The plankton was identified and total number per species recorded using keys and checklists. Enumeration of zooplankton was done on natural unit count and reported as units or organisms per milliliter (mL). A total of forty-three (43) species belonging to five (5) taxonomic groups were recorded from Sombreiro River. Bacillariophyceae was represented by 18 species consisting of 41.9% by composition. This was followed by Chlorophyceae (14 species) consisting of 32.6%, Cyanophyceae (8 species) consisting of 18.6%, Chrysophyceae (1species) consisting of 2.3% and Xanthophyceae (2species) consisting of 4.7%. Bacillariophyceae was the highest, 49.9%. This was followed by Chlorophyceae, 25.0%. The others were Cyanophyceae (15.8%), Chrysophyceae (2.4%) and Xanthophyceae (6.9%).