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Stable carbon isotopes and the C : N ratio In the estuaries of the Pamlico and Neuse Rivers. North Carolina
Author(s) -
Matson Ernest A.,
Brinson Mark M.
Publication year - 1990
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1990.35.6.1290
Subject(s) - estuary , seston , tributary , oceanography , particulates , phytoplankton , salinity , environmental science , dominance (genetics) , brackish water , isotopes of carbon , littoral zone , sediment , hydrology (agriculture) , total organic carbon , environmental chemistry , geology , ecology , chemistry , nutrient , biology , paleontology , biochemistry , cartography , geotechnical engineering , gene , geography
The C: N and stable C isotope ratios ( δ 13 C) of sedimentary and seston organic C (OC) were used to identify OC sources and sites of deposition in two large estuaries in North Carolina. In the upper 10 km of the oligohaline zones, C : N ratios of sediment are characteristic of particulate terrestrial plant material (>15). The δ 13 C values increase linearly with distance from freshwater tributaries to the mouths of the estuaries (∼20‰ salinity), >40 km from the ocean. Observed gradients in isotopic and C : N ratios imply that conservative mixing of freshwater and marine OC occurs. Phytoplankton in the estuaries produce at least 10 times more particulate OC than is delivered in runoff, however, and its biomass is recycled at rates much faster than those of water exchange. The observed gradients are therefore largely attributed to recycling of a resident pool of estuarine C, atmospheric CO 2 , and an increasing marine bicarbonate fraction from the salt wedge downriver. Essentially lentic conditions in these estuaries ensure the dominance of in situ biological processes.