- Title
- Nitrate uptake estimates phytoplankton incorporation of dissolved NO3- at selected depths from CCE LTER process cruises in the California Current System, 2011 – 2016 (ongoing).
- Abstract
- Nitrate uptake samples (1.1-L) of seawater are taken each day shortly before noon on the CTD rosette up-cast during the CCE Process cruises (since 2011, ongoing). Approximate nitrate concentrations are determined at sea and the samples are spiked with 15NO3- at a concentration equivalent to ~10% ambient nitrate. Samples (one sample per depth) are incubated for 24 hours in polycarbonate bottles held at natural light and temperature conditions on the in situ array. After recovery samples are filtered onto pre-combusted GF/F filters, which are analyzed for particulate nitrogen and δ15N by mass spectrometry in the Scripps Analytical Facility. Accurate nitrate concentrations are determined after the cruise from frozen and filtered samples analyzed by autoanalyzer (see separate Dissolved Inorganic Nutrients dataset by Ralf Goericke). Nitrate uptake is calculated using the equations in Dugdale & Wilkerson (1986). In surface waters where nitrate concentrations are often quite low, we spike with a minimum of 10 nmol L-1 15NO3-. Since this can lead to a bias (high) in calculated nitrate uptake, when post-cruise nitrate analyses showed that our spike concentration was greater than 10% of ambient nitrate, we multiplied by the uptake calculated from the equations of Dugdale & Wilkerson (1986) by (ambient NO3-)/(ambient NO3- + added 15NO3-). Primary production was simultaneously estimated from 14C uptake in triplicate 250-mL bottles (plus a dark bottle) incubated similarly on the in situ array (see separate Primary Production – Particulate dataset by Ralf Goericke). We calculated f-ratios by assuming that phytoplankton uptake occurred at Redfield carbon:nitrogen ratios of 106:16 (mol:mol). To eliminate the impact of phytoplankton that may be engaged in luxury nitrate uptake in the deep euphotic zone, we also report conservative nitrate uptake, which is the minimum of nitrate uptake or primary production divided by the Redfield C:N ratio. This value thus sets a maximum for nitrate uptake at equal to primary production (after conversion from mg C to umol N).
- Keywords
- oceans, nitrate, CTD, concentration, particulates, primary production, RAPID: Responses of the California Current Ecosystem to El Nino 2015-16
- LTER Data System Record
- http://dx.doi.org/10.6073/pasta/0b280f0012bf601f94171892d84328a2
- Projects
-
California Current Ecosystem LTER
- Creators
-
Stukel, Mike (mstukel@fsu.edu)
- Contact
- CCE LTER Information Manager (ccelter.im@gmail.com)
Data
| table |
Nitrate Uptake
Main data table for dataset |
Rows: 245 Columns: 9 |
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