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Abstract:
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The water quality and primary productivity of Valanthakad backwater (9° 55 10. 24 N latitude and 76° 20 01. 23 E
longitude) was monitored from June to November 2007. Significant spatial and temporal variations in temperature,
transparency, salinity, pH, dissolved oxygen, sulphides, carbon dioxide, alkalinity, biochemical oxygen demand, phosphatephosphorus,
nitrate-nitrogen, nitrite-nitrogen as well as primary productivity could be observed from the study. Transparency
was low (53.75 cm to 159 cm) during the active monsoon months when the intensity of solar radiation was minimum, which
together with the run off from the land resulted in turbid waters in the study sites. The salinity in both the stations was low (0.10
‰ to 4.69 ‰) except in August and November 2007. The presence of total sulphide (0.08 mg/ l to 1.84 mg/ l) and higher
carbon dioxide (3 mg/ l to 17 mg/ l) could be due to hospital discharges and decaying slaughter house wastes in Station 1 and
also from the mangrove vegetation in Station 2. Nitrate-nitrogen and phosphate-phosphorus depicted higher values and
pronounced variations in the monsoon season. Maximum net primary production was seen in November (0.87 gC/ m3/ day) and
was reported nil in September. The chlorophyll pigments showed higher values in July, August and November with a negative
correlation with phosphate-phosphorus and nitrite-nitrogen. The study indicated that the water quality and productivity of
Valanthakad backwater is impacted and is the first report from the region |