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| Titel |
Seasonal occurrence of anoxygenic photosynthesis in Tillari and Selaulim reservoirs, Western India |
| VerfasserIn |
S. Kurian, R. Roy, D. J. Repeta, M. Gauns, D. M. Shenoy, T. Suresh, A. Sarkar, G. Narvenkar, C. G. Johnson, S. W. A. Naqvi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 7 ; Nr. 9, no. 7 (2012-07-09), S.2485-2495 |
| Datensatznummer |
250007181
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| Publikation (Nr.) |
 copernicus.org/bg-9-2485-2012.pdf |
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| Zusammenfassung |
| Phytoplankton and bacterial pigment compositions were
determined by high performance liquid chromatography (HPLC) and liquid
chromatography-mass spectrometry (LC-MS) in two freshwater reservoirs
(Tillari Dam and Selaulim Dam), which are located at the foothills of the
Western Ghats in India. These reservoirs experience anoxia in the
hypolimnion during summer. Water samples were collected from both reservoirs
during anoxic periods while one of them (Tillari Reservoir) was also sampled
in winter, when convective mixing results in well-oxygenated conditions
throughout the water column. During the period of anoxia (summer),
bacteriochlorophyll (BChl) e isomers and isorenieratene, characteristic of
brown sulfur bacteria, were dominant in the anoxic (sulfidic) layer of the
Tillari Reservoir under low light intensities. The winter observations
showed the dominance of small cells of Chlorophyll b-containing green algae and
cyanobacteria, with minor presence of fucoxanthin-containing diatoms and
peridinin-containing dinoflagellates. Using total BChl e concentration
observed in June, the standing stock of brown sulfur bacteria carbon in the
anoxic compartment of Tillari Reservoir was estimated to be 2.27 gC m−2,
which is much higher than the similar estimate for carbon derived
from oxygenic photosynthesis (0.82 gC m−2. The Selaulim Reservoir also
displayed similar characteristics with the presence of BChl e isomers and
isorenieratene in the anoxic hypolimnion during summer. Although sulfidic
conditions prevailed in the water column below the thermocline, the
occurrence of photo-autotrophic bacteria was restricted only to mid-depths
(maximal concentration of BChl e isomers was detected at 0.2% of the
surface incident light). This shows that the vertical distribution of
photo-autotrophic sulfur bacteria is primarily controlled by light
penetration in the water column where the presence of H2S provides a
suitable biogeochemical environment for them to flourish. |
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