This paper reported a fifteen month study of the patterns of variation of phytoplankton, physical and chemical characteristics of the Imo River estuary between April 2001 and June 2002 were reported. There were remarkable spatial and temporal variations of physico-chemical parameters and significant difference in the stations (p< 0.05). A wide array of phytoplankton species distributed in 221 taxa, 85 genera, 37 families, 16 orders in 7 divisions; with chlorophyta > bacillariophyta > Cyanophyta > Dinophyta > Euglenophyta > Chrysophyta > Rhodophyta. Phytoplankton density and diversity were highest in the brackish water, mesohaline zone of the estuary. The trend of wet season nutrient enrichment was observed and maximum phytoplankton concentration was however not coincidental with nutrient enrichment. Early dry season assemblages were characterized by relatively large number of chlorophyta and pennate diatoms in the freshwater and brackishwater zones of the estuary. The dynamic throughput of the estuary is a function of seasonal nutrient input and the effect of the adjacent sea on the estuary.

Water logging areas are basically designated by water affluences in permanent or seasonal basis. But due to accelerated rate of human intervention and human induced modification of natural processes, natural wetland landscapes also have today under acute seasonal water scarcity. Wetland areas have been gradually squeezing, permanent wetland areas have transmuted into semi permanent wetlands with groundwater table (GWT) slashing down rapidly. Due to intensive boro culture, as much as 2444 mini deeps ground water table have been slashed by 0.32 m./ year since 1968 to 2008 during summer but it is more higher (0.35 m./year) between 2001-2008. During May, 1968 G.W.T. depth was 6.09 m. whereas it is almost 20.19 m by 2008 Changes in land use to some extent mitigate such ensuing threats of ground water scarcity as a result the entire hydrological and ecological scenario of the wetland landscape has under gone massive negative transformation.

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