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Tracing the carbon and nitrogen flow in the mangrove ecosystem of the Gautami, Godavari delta, Bay of Bengal (India)
Dehairs, F.A.; Rao, R.; Chandramohan, P.; Raman, A.V.; Marguiller, S.; Hellings, L. (2000). Tracing the carbon and nitrogen flow in the mangrove ecosystem of the Gautami, Godavari delta, Bay of Bengal (India). Hydrobiologia 431(2-3): 225-241. dx.doi.org/10.1023/A:1004072310525
In: Hydrobiologia. Springer: The Hague. ISSN 0018-8158, more
Peer reviewed article  

Available in  Authors 

Author keywords
    stable isotope tracers; carbon; nitrogen; mangroves; litterfall; suspended matter; zooplankton; macrobenthos

Authors  Top 
  • Dehairs, F.A., more
  • Rao, R.
  • Chandramohan, P.
  • Raman, A.V.
  • Marguiller, S.
  • Hellings, L.

Abstract
    Stable carbon isotopic composition and C/N ratio were used to trace the input of carbon associated with mangrove litter into the estuary of the Godavari–Gautami delta system and Kakinada bay (Andhra Pradesh, India). Suspended organic matter in the mangrove channels was more depleted in 13C (average d13C = –24.5‰) than in Kakinada bay which showed d13C values for suspended matter (average d13C = –22.7‰) closer to those expected for marine phytoplankton. Suspended organic matter from mangrove channels was enriched in nitrogen (average C/N atom ratio = 12.7) and 13C (average d13C = –24.5‰) relative to mangrove leaf litter, which had a C/N ratio of 75 and a d13C value of –28‰. Lowest C/N ratios for suspended matter were observed during southwest monsoon when rainfall was highest. Although in general, mangrove litter fall was also lower during this period, no clear correlation was observed between litter fall and C/N ratio of suspended matter. In general, the composition of suspended matter pointed towards phytoplankton as a major component. Isotopic composition of zooplankton suggested selective feeding on 13C-enriched, marine phytoplankton in open Kakinada bay and on 13C-depleted organic matter, such as estuarine phytoplankton and mangrove litter, in the mangrove channels. From the d13C signature, it appeared that mangrove carbon was present to some extent in zooplankton and macrofauna from the mangrove mudflats and channels, but the signal rapidly decreased in Kakinada bay. Nitrogen isotopic composition of zooplankton and macrofauna indicated a progressive enrichment of 15N away from the mangrove forest towards the northern part of Kakinada bay, in approach of Kakinada city. This is thought to reflect input of anthropogenic nitrogen enriched in 15N and subsequent uptake of this enriched nitrogen into the aquatic food chain.

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