Carbon isotopic and biochemical fingerprints of sedimentary organic matter in lower Narmada and Tapi rivers, north-west coast of India
Abstract
Sources of organic matter (OM) in lower Narmada and Tapiriver-estuaries were examinedusing
organic carbon to nitrogen ratio (Corg/N),stable carbon isotope ratio (
13Corg) andlignin phenol
biomarkers. The signature of lower Corg (av. 0.50%)and higher
13Corg (av. -20.3‰) inNarmada
and,higher Corg (av. 0.85%) and lower
13Corg (av. -22.8‰)in Tapihighlight the difference in OM
characteristics ofboth systems, nevertheless they flow adjacent to each other. TheOM in Tapiwas
predominated by fresh plant tissues, as indicated by higher 8=1.2–3.2 mg/100mgCorg,lower Ad/Alv
= 0.22-0.46 and lower LPVI = 17-23. The plant OM present in the sediments of Narmada was
previously degraded and mixed with soil. The OMcontribution from algaewas restricted to estuarine
stations in both the rivers, which was~50% in Narmada and ~35% in Tapi. The contribution of OM
from fresh vascular plant was higher (20% to 63%) in Tapithan Narmada (2% to 35%). This study
illustrated the benefits of using lignin phenols along withCorg/N and
13Corgto identify the potential
OM sourcesin two large river-estuary systems of India, whichhighlighted the complex interaction of
natural and anthropogenic processes acted on theterrestrial OM compositions
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