Nitrogen Uptake Rates during Spring in the NE Arabian Sea

Table 2

Station number, nitrate, nitrite, phosphate, Chl a, total cell counts (including Trichodesmium), and abundance of Trichodesmium at the surface and 𝛿¹⁵N of surface natural PON data at different sampling stations.

Station no.	NO3^− (𝜇M)	NO2^− (𝜇M)	PO4^2− (𝜇M)	Chl a (mg m^−3)	Total cell counts (cells L^−1)*	Trichodesmium (trichomes L^−1)	𝛿^15N (‰)
1^b	—	—	—	0.15	1840	240	—
2^a,#	nd	0.02	0.24	0.17	840	768	6.5
3^a	—	—	—	0.18	1376	96	7.4
4^a,#	0.1	0.03	0.43	0.85	8338	1056	4.3
5^b,#	nd	0.02	0.23	0.23	1428	374	8.8
6^b	—	—	—	0.14	672	192	5.5
7^b	—	—	—	0.11	180	90	7.2
8^b,#	nd	0.02	0.23	0.18	616	44	10.5
9^b	—	—	—	0.14	972	72	—
10^b,#	nd	0.03	0.36	0.16	756	nd	7.9
11^b	—	—	—	0.16	728	26	—
12^b,#	nd	0.03	0.38	0.14	1188	nd	11.4
13^b	—	—	—	0.17	812	nd	—
14^a,#	0.33	0.03	0.48	0.32	3099	2160	4.6
15^a,#	0.88	0.09	0.68	6.63	4256	4004	2.5

a: denotes coastal locations (water depth <200 m). b: denotes open ocean locations (water depth >200 m). #: denotes stations at which nitrate, ammonium and urea uptake rates measurements were carried out. —: no data available. nd: not detectable (below analytical limit of detection). *: total cell counts include all the phytoplankton including Trichodesmium. Phytoplankton, other than Trichodesmium, are in the unit of cells L⁻¹. Trichodesmium counts (trichomes L⁻¹) are not converted into cells L⁻¹.