Abstract:
Sustainable estuary management provides fishery resources, supports livelihoods and maintains
estuarine food webs. However, these are highly dependent on hydrological factors and nutrients
effects of the estuary itself. We studied seasonal phytoplankton quantity and composition of the
Pasur River estuary in the Sundarbans mangrove forest, Bangladesh to understand the
phytoplankton structure and identify potential indicators of environmental changes. Water and
phytoplankton samples were collected at 11 different locations around the study region from
January to December 2019 to assess spatial and temporal differences. Significant differences (p <
0.05) in the average salinity were observed between the dry and rainy seasons. Elevated
phytoplankton (blue-green algae) concentrations were associated with decreased salinity while
increased diatom abundance was linked to higher salinity. Phytoplankton succession from blue-green
algae (wet season) to diatoms (dry season) occurred due to variations in physicochemical parameters
and nutrient factors. Simultaneously, phytoplankton diversity and density were shown to change in
response to habitat quality and seasonal variation. This study highlights the potential impacts of both
human activities and natural factors on the population structure in these estuarine environments.
