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Short-term variability of water quality and its implications on phytoplankton production in a tropical estuary (Cochin backwaters - India)

DRS at CSIR-National Institute of Oceanography

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Title Short-term variability of water quality and its implications on phytoplankton production in a tropical estuary (Cochin backwaters - India)
 
Creator Madhu, N.V.
Balachandran, K.K.
Martin, G.D.
Jyothibabu, R.
Thottathil, S.D.
Nair, M.
Joseph, T.
Kusum, K.K.
 
Subject Nutrients
tropical estuary
Primary production
Phytoplankton
 
Description Changes in the phytoplankton biomass (chlorophyll a), production rate, and species composition were studied over two seasons using the time series measurements in the northern limb of the Cochin estuary in relation to the prevailing hydrological conditions. The present study showed the significant seasonal variation in water temperature (F = 69.4, P less than 0.01), salinity (F = 341.93, P less than 0.01), dissolved inorganic phosphorous (F = 17.71, P less than 0.01), and silica (F = 898.1, P less than 0.01) compared to nitrogen (F = 1.646, P less than 0.05). The uneven input of ammonia (3.4-224.8 mu M) from upstream (Periyar River) leads to the inconsistency in the N/P ratio (range 6.8-262). A distinct seasonality was observed in Si/N (F = 382.9, P less than 0.01) and Si/P (F = 290.3, P less than 0.01) ratios compared to the N/P ratio (F = 1.646, P less than 0.05). The substantial increase in chlorophyll a (average, 34.8 plus or - 10 mg m sup(-3)) and primary production (average, 1304 plus or - 694 mg C m sup(-3) day sup(-1)) indicated the mesotrophic condition of the study area during the premonsoon (PRM) and it was attributed to the large increase in the population of nanoplankton (size less than 20 mu) such as Skeletonema costatum, Thalassiosira subtilis, Nitzschia closterium, and Navicula directa. In contrast, during the post monsoon (PM), low chlorophyll a concentration (average, 9.33 plus or – 9.2 mg m sup(-3)) and primary production (average, 124 plus or - 219 mg C m sup(-3) day sup(-1)) showed the predominance of heterotrophic condition. It can be stated that favorable environmental conditions (optimum nutrients and light intensity) prevailing during the PRM have enhanced the abundance of the nanoplankton community in the estuary, whereas during the PM, the light limitation due to high turbidity can reduce the nanoplankton growth and abundance, even though high nutrient level exists.
 
Date 2010-10-07T10:21:48Z
2010-10-07T10:21:48Z
2010
 
Type Journal Article
 
Identifier Environmental Monitoring and Assessment, vol.170(1-4); 287-300
no
http://drs.nio.org/drs/handle/2264/3728
 
Language en
 
Relation Environ_Monit_Assess_170_287.jpg
 
Rights An edited version of this paper was published by Springer. This paper is for R & D pupose and Copyright [2010] Springer.
 
Publisher Springer