| dc.description.abstract | An experiment was conducted on some physico-chemical parameters with seasonal
variation and diversity indices of plankton community of Dhepa river in Dinajpur district
from May 2014 to April 2015. The whole experiment duration was divided into four
seasons such as summer, autumn, winter and spring. Samples were collected fortnightly
from four sampling sites named Vogdoma, Nijpara-1, Nijpara-2 and Itvata. Physicochemical parameters and plankton community were determined both at the field level and
departmental laboratory of Fisheries Management, Hajee Mohammad Danesh Science and
Technology University, Dinajpur. Significant level of variation (P<0.05) was observed both
in physico-chemical factors and plankton community according to the seasons. Depth,
dissolved oxygen, pH, PO4-P, hardness and chlorophyll-a were found higher during winter
season but reverse result was observed in temperature and transparency. Depth and
dissolved oxygen were highest during summer season. Water level of this river was
influenced by sluice gate. The plankton community consisted of 74 genera in 4 groups of
phytoplankton and 3 groups of zooplankton. The number of genera and density of plankton
showed high seasonal variation during winter and summer. Majority of plankton community
was shared by phytoplankton. The density of plankton community was higher (32.33×103
cell/L) during winter following phytoplankton and summer due to zooplankton. The density
of Chlorophyceae, Bacillariophyceae had the highest density during the early winter and
Cyanophyceae during late winter. Rotifera, Cladocera and Copepoda were higher during
summer and late autumn to early winter. Plankton community had the highest (3.68) and
lowest (2.50) Shannon-Weaver diversity index during winter and summer, respectively. The
Shannon-Weaver diversity index remained constant at around 2.78 to 3.44. The maximum
Evenness index (1.12) occurred in autumn season, whereas the minimum (0.90) was in
spring season. The highest genus richness was observed in the month of November during
winter season where as lowest (4.88) in the month of October. Both the highest number of
genera and total number of individuals was highest in the month of November. The
Shannon-Weaver diversity index value indicates good water quality of the river especially
during winter season | en_US |
