The Effects of Flood on Amassoma Flood Plain Sediments Niger Delta, Nigeria was studied for a period of six months (November – December, 2012 and January, 2013 for the dry season and April, May and June; 2013 for the Wet season) and compared with previous results obtained in the study area. A total of forty-three (43) phytoplankton species belonging to five (5) families were present both before and after flooding. These include: BACILLARIOPHYCEAE: Meloira granulate, Melosira varians, Melosira distance, Melosira pusila, Naviicula viridula, Nitzischia sigma, Cyclotella operculata, Cyclotella omata, Cosinodiscus lacustris, Cymbella lata, Fragilaria intermedia, Gyrosigma acuminatum, Pinnularia horealis, Amphora ovalis, Synedra ulna, Stephanodiscus asroea and Tabellaria fenestrrata; CHLOROPHYCEAE: Volvox aureus, Volvox globator, Coelastrum reticulate, Closterium intermedium, Closterium pervulum, Closterium gracile, Crusigenia puadrata, Crusigenia truncate, Netrium digitatus, Netrium intermedium, Gonatozygon aculeatum, Spirogyra sp, Spirotaenia condensate and Desmidium sp; CYNOPHYCEAE: Anabaena spiroides, Anabaena affinis, Anabaena arnoldii, Oscillartoria lacustris, Oscillartoria princeps, Raphidiopsis mediteranea, Rivularia sp and Lymbya limnetica; CHRYSOPHYCEAE: Dinobryon sertularia and XANTHOPHYCEAE: Trbonema minus and Tribonema viridis. Phytoplankton population also decreased drastically after the flooding though there was no significant variation between sampling stations.
