Nitrate concentration
- 364,992
- values
- 6,937
- flagged
i
6,937 of these 364,992 values (1.9 %) are flagged by their provider as questionable or bad. The Explorer, the climatology and its anomalies leave them out; do the same when you read the data yourself (cc_qual_ok_sql()in calcofi4r,qual_ok_sql()in calcofi4py). - 14,282
- sampling events
- 1959–2021
- years
- 1
- dataset
- 0–5,351 m
- depth
- every month
- seasons
NO3− · nitrate · 62.004 g/mol · CHEBI:17632
Concentration of nitrate per unit volume of the water column. Nitrate may be expressed in terms of mass or quantity of substance.
Seal Analytical continuous-flow AutoAnalyzer 3 (AA3)
520 nm
Bottle sampling methods on calcofi.org ↗How do the eutrophication and pollution impact ocean productivity and water quality?
CalCOFI holds 364,992 values of it from 14,282 sampling events in one dataset, 1959–2021, from the surface to 5,351 m. At 200–500 m it has risen 0.23 per decade since 1984.R Nitrate is the fertiliser upwelling lifts into the light; the spring blooms, and the fisheries above them, run on it. At depth it has risen as oxygen fell, the fingerprint of changing source waters.C
other ways to say why · 5
- Nitrate at the surface is a fingerprint of recent upwelling: where it is high, cold deep water has just arrived and a bloom follows. needs a citation before it can be the pick
- GOOS asks How do the eutrophication and pollution impact ocean productivity and water quality? source
- GOOS asks Is the biomass of the ocean changing? source
- Wikipedia Upwelling source
- Wikipedia Nitrate is a polyatomic ion with the chemical formula NO3−. Salts containing this ion are called nitrates. Nitrate · CC BY-SA 4.0 · rev. 1378622700
The measurement
Measured in i
One row per series, one cell per year, darker with more values — the same strip the front
door draws per dataset and a species page draws per taxon. Each row is one dataset's own
measurement_type; the label is written once, in the title above.
i
One row per series, one cell per year, darker with more values — the same strip the front door draws per dataset and a species page draws per taxon. Each row is one dataset's own measurement_type; the label is written once, in the title above.
-
series
nitrate· source columnno3u_m· flag columnno3q6,937 flagged · 1.9 %
The structure
ChEBI: “A nitrogen oxoanion formed by loss of a proton from nitric acid. Principal species present at pH 7.3.” · RDKit 2026.03.6 from the ChEBI molfile, in the page’s ink · CC BY 4.0. ChEBI’s roles are never shown.
How it is measured
A modification of Armstrong (1967): the seawater sample passes through a cadmium column that reduces nitrate to nitrite, then sulfanilamide and N-(1-naphthyl)ethylenediamine couple it into a red azo dye read in a 10 mm flow cell; nitrate is the combined nitrate-plus-nitrite reading minus a parallel nitrite-only run without the cadmium column. (calcofi.org Bottle sampling methods)
- NO3- -> NO2- (cadmium column, 98-100% efficient)
- NO2- + sulfanilamide + NED -> red azo dye
- absorbance read at 520 nm
Why it matters
The familiar scale i
Bars are each series' 5th–95th percentile, the line its minimum to maximum, the ring its median;
the marks are metadata/measurement_scale.csv's, each hovering to its own source.
i
Bars are each series' 5th–95th percentile, the line its minimum to maximum, the ring its median;
the marks are metadata/measurement_scale.csv's, each hovering to its own source.
The record’s own history i
Deeper than the climatology reaches: 1,468 values at 1000–2000 m, 687 values at 2000+ m have no
normal to depart from, because the release’s climatology stops at its
deepest built bin. Carrying it to the bottom is one argument of
build_climatology() and puts these bands on the page too.
i
Deeper than the climatology reaches: 1,468 values at 1000–2000 m, 687 values at 2000+ m have no
normal to depart from, because the release’s climatology stops at its
deepest built bin. Carrying it to the bottom is one argument of
build_climatology() and puts these bands on the page too.
the GOOS specification sheet for this Essential Ocean Variable lists it, and asks
GOOS asks
- How do the eutrophication and pollution impact ocean productivity and water quality?
- Is the biomass of the ocean changing?
GOOS specification sheet ↗ · quoted, not copied
The record
Ways in i
Read from measurements.json of release
v2026.10.05, written at release by
calcofi4db::build_measurements_catalog() beside
taxa.json. The catalog's index is
/measurements/; the JSON-LD on this page is a
schema.org/DefinedTerm in the NERC P01 term set with a
PropertyValue per series.
ExplorerExplorer · a depth section vs normaldb-queryi
Read from measurements.json of release v2026.10.05, written at release by calcofi4db::build_measurements_catalog() beside taxa.json. The catalog's index is /measurements/; the JSON-LD on this page is a schema.org/DefinedTerm in the NERC P01 term set with a PropertyValue per series.
SELECT * FROM read_json('…/v2026.10.05/catalog.json')
-- objects[] WHERE table = 'obs_env'
-- AND partition_value = 'nitrate'library(calcofi4r)
con <- cc_get_db() # the promoted release
tbl(con, "obs_env") |> filter(measurement_type %in% c("nitrate"))import calcofi4py as cc
con = cc.cc_get_db()
con.sql("SELECT * FROM obs_env WHERE measurement_type IN ('nitrate')").df()By depth i
Values per depth band at the release grain, one thin bar per series. The bands are the
record's own (0-10 … 2000+ m).
i
Values per depth band at the release grain, one thin bar per series. The bands are the record's own (0-10 … 2000+ m).
By month i
Values per calendar month, one row per series: CalCOFI's quarterly cruises show as peaks in
the months the ships sail.
i
Values per calendar month, one row per series: CalCOFI's quarterly cruises show as peaks in the months the ships sail.
Range & quality
details
- bounds
- The registry declares
-1 … 60 µmol/Lfornitrate; a value outside it is dropped at the ingest (drop_out_of_bounds()). - observed
- Hydrographic Bottle
nitrate-0.4 · median 18.8 · 56 µmol/L (5th–95th percentile 0–39.8) - flags
- Hydrographic Bottle
nitrateno3qon 7,215 of 364,992 rows:4277 ·61 ·86,937; qual_ok keeps 358,055. The codes are this dataset's own vocabulary, uninterpreted. - baseline
- A monthly climatology exists for this measurement (the release's climatology table: 1993–2013, dataset × grid cell × calendar month × 10 m bin), so the Explorer can draw anomalies against it rather than values.
Related measurements i
The same quantity from another platform or another kind of sample, each its own page and
never merged into this one: a dataset's own bottle samples would count that dataset twice, an underway intake
is not a cast, and a replicate is not a mean. The reason is the record's
(related[].why).
i
The same quantity from another platform or another kind of sample, each its own page and never merged into this one: a dataset's own bottle samples would count that dataset twice, an underway intake is not a cast, and a replicate is not a mean. The reason is the record's (related[].why).
- Bottle nitrate btl_nitrate · CTD Cast Files · 1993–2026 · 143,515 values · P01 NTRAZZXX the same quantity from the CTD files' own bottle samples — plausibly the same physical bottles, so merging them would count the bottle dataset twice
Cite
Cite the release; each dataset's own citation, licence and DOI are on its page — Hydrographic Bottle. The Explorer's Share → Cite writes it for the view you make.