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International Journal of Marine Science 2013, Vol.3, No.16, 128-134
http://ijms.sophiapublisher.com
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0.364±0.06 mg/L was observed at surface of Supoti
canal water in post monsoon and the minimum
concentration of TP, 0.053±0.001 mg/L occurred at
surface water of Bogi in winter.
During post monsoon season, TP concentration varied
from 0.326 mg/L to 0.409 mg/L in Passur River. In
Arpangashiaand and Malancha River it varied from
0.075 mg/L to 0.144 mg/L and in Baleswar and
Bhola River it varied between 0.106 mg/L and
0.364 mg/L (Figure 11).
Figure 11 Comparison of total phosphorus (TP) concentration
in three River systems during post monsoon
During winter season, TP concentration varied between
0.091 mg/L to 0.371 mg/L in Passur River. In
Arpangashia and Malancha River it varied from
0.060 mg/L to 0.113 mg/L and in Baleswar and
Bhola River it varied between 0.053 mg/L and
0.144 mg/L (Figure 12).
Figure 12 Comparison of total phosphorus (TP) concentration
in three River systems during winter
In the mangrove River water Nitrogen and
Phosphorus concentration vary considerably. Figure 5
represents that the minimum values (2.31 mg/L) of
TN was observed at surface water of Arpangashia
River in Post monsoon season. On the other hand the
maximum concentration (5.95 mg/L) occurred at
surface water of Poshurtola of Malancha River in
winter season (Figure 5). Higher concentration of total
Nitrogen was found in winter because of less dilution
due to reduction of runoff and currents. Seasonal
change in the concentration of total Phosphorus
varied from the minimum values (0.060 mg/L) was
observed at surface water of Kolagachi River Point
in winter season to the maximum level (0.409 mg/L)
occurred at surface water of Poshurtola of Malancha
River in post monsoon (Figure 9).
The higher level of total nitrogen in winter season and
higher level of total phosphorus in post monsoon
season is in agreement with Adeyemo (2004) who
found the nutrient load of water of Ibadan River
system during rainy and dry seasons in the range of
phosphate (2.23~16.2 ppm and 0.35~2.8 ppm
respectively); Total nitrogen (0.13~0.9 ppm and
0.47~3.4 ppm respectively). The high level of nitrogen
observed during this study is in agreement with
Wolfhard and Reinhard, (1998), who concluded that
nitrogen are usually built up during dry seasons. This
study is contradictory to the findings of some other
study which is given below (Table 2).
The phosphorus and Nitrogen concentrations in water
were high as compared to the standard (0.2 mg/L)
guidelines (EPA, 2002); however Phosphorus
concentration was higher during the post monsoon
season Figure 6, while Nitrogen was higher during the
winter season Figure 5. Land use around Riverine areas
in Sundarbans mangrove is predominantly for
farmland and could be a possible explanation for the
high levels of phosphate from run-off during rainy
seasons as observed in this study. There are various
sources of phosphorus to Rivers such as, runoff from
surface catchments, and interaction between the water
and sediment from dead plant and animal remains at
the bottom of Rivers. Phosphorus is regarded as the
main culprit among the nutrients responsible for
eutrophication of River water, as it is the primary
initiating factor. The result reveals that the nutrient
load in the watershed is high; destruction of the
Rivers can therefore result because of nutrient
enrichment, productivity, decay and sedimentation
(Adeyemo, 2004).