Phytoplankton Composition and Abundance in Mbiakong River, Cross River Estuary, Niger Delta, Nigeria

The phytoplankton composition and abundance in Mbiakong River, Cross river estuary, Niger Delta, Nigeria was studied for a period of one year (March, 2021-February, 2022). Plankton net of mesh size 55µm was used to collect plankton samples from below the water surface, after towing for 5 minutes. The content was emptied into plastic containers and fixed immediately with 4% formalin in the field for preservation. After 48hrs in the laboratory, the preserved plankton samples were concentrated to 10 ml. The concentrated sample was agitated to homogenize before pipetting 1ml sub sample with sample pipette. Enumeration and identification were performed using a zeis inverted microscope at x400 and x 1000 magnification. Species identification was done using recommended keys and guides. A total of 615 individual organisms comprising of 35 species belonging to five taxonomic groups were recorded from Mbiakong River. The most abundant group was the Bacillariophyceae which was represented by 12 species (302 organisms) consisting of 49.11%. This was followed by Chlorophyceae represented by 10 species (199 organisms) consisting of 32.36%, Cyanophyceae represented by 12 species (109 organisms) consisting of 17.72%, Euglenophyceae represented by one species (three organisms) consisting of 0.33% and the least abundant was the Dinophyceae represented by one species (two organisms) consisting of 0.14%. The study revealed that species composition and abundance was high in June.