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Impact of eutrophication on the occurrence of Trichodesmium in the Cochin backwaters, the largest estuary along the west coast of India

DRS at CSIR-National Institute of Oceanography

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Title Impact of eutrophication on the occurrence of Trichodesmium in the Cochin backwaters, the largest estuary along the west coast of India
 
Creator Martin, G.D.
Jyothibabu, R.
Madhu, N.V.
Balachandran, K.K.
Nair, M.
Muraleedharan, K.R.
Arun, P.K.
Haridevi, C.K.
Revichandran, C.
 
Subject algal blooms
phytoplankton
eutrophication
nutrients
 
Description Phytoplankton studies in early 1970s have shown the annual dominance of diatoms and a seasonal abundance of Trichodesmium in the lower reaches of the Cochin backwaters (CBW) and adjacent coastal Arabian Sea during the pre-summer monsoon period (February to May). Surprisingly, more recent literature shows a complete absence of Trichodesmium in the CBW after 1975 even though their seasonal occurrence in the adjacent coastal Arabian Sea continued without much change. In order to understand this important ecological feature, we analyzed the long-term water quality data (1965-2005) from the lower reaches of the CBW. The analyses have shown that salinity did not undergo any major change in the lower reaches over the years and values remained greater than 30 throughout the period. In contrast, a tremendous increase was well marked in levels of nitrate (NO sub(3)) and phosphate (PO sub(4)) in the CBW after 1975 (av. 15 and 3.5 mu M, respectively) compared with the period before (av. 2 and 0.9 mu M, respectively). Monthly time series data collected in 2004-2005 period from the lower reaches of the CBW and coastal Arabian Sea have clearly shown that the physical characteristics like salinity, temperature, water column stability, and transparency in both regions are very similar during the pre-summer monsoon period. In contrast, the nutrient level in the CBW is several folds higher (NO sub(3), 8; PO sub(4), 4; SiO sub(4), 10; and NH sub(4), 19 mu M) than the adjacent coastal Arabian Sea (NO sub(3), 0.7; PO sub(4), 0.5; SiO sub(4), 0.9; and NH sub(4), 0.6 mu M). The historic and fresh time series data evidences a close coupling between enriched levels of nutrients and the absence of Trichodesmium in the Cochin backwaters.
 
Date 2013-02-05T05:17:37Z
2013-02-05T05:17:37Z
2013
 
Type Journal Article
 
Identifier Environmental Monitoring and Assessment, vol.185(2); 2013; 1237-1253
http://drs.nio.org/drs/handle/2264/4244
 
Language en
 
Rights An edited version of this paper was published by Springer. This paper is for R & D purpose and Copyright [2012] Springer.
 
Publisher Springer