15N enrichment in the surface Particulate Organic Nitrogen of the north-eastern Arabian Sea from the middle to the waning phase of the winter monsoon: possible causes
Other literature type
A temporal increase of ~5‰ in the average nitrogen isotopic
composition (δ<sup>15</sup>N<sub>PON</sub>) of surface particulate organic
nitrogen was observed in the open north-eastern Arabian Sea during January
to late February-early March 2003, despite the presence of <i>T. erithraeum</i> (up to ~11%), a diazotroph that fixes atmospheric N<sub>2</sub>, in the latter period.
Hydrographic conditions and residence time of nitrate in the water column
suggested that this increase could be a combined effect of denitrification
in the subsurface layer and inefficient utilization of nitrate entrained in
the water column during January.