Nitrate
Nitrate concentration
µmol/Lkey nitrateNERC P01 NTRAZZXXP06 units UPOXseries nitrate
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 0.21 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
- 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). - 1959–2021
- years
- 1
- dataset
- 0–5,351 m
- depth
- every month
- months
Measured in
1 dataset
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 %
Explorera depth section vs normaldb-queryERDDAPThis page as JSON R · Python · Parquet
Every way in 8 ways · ERDDAP · Parquet · R · Python · JSON
Read from measurements.json of release v2026.10.21, 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-querySELECT * FROM read_json('…/v2026.10.21/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()The structure NO3− nitrate
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 Seal Analytical continuous-flow AutoAnalyzer 3 (AA3) at 520 nm
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 6 ways to say it · EOV Nutrients
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
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 record’s own history 6 depth bands against the 1993–2013 normal
Each year against the normal 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.
Units and range µmol/L · -1 … 60 declared · 6,937 flagged
µmol/L (umol/L in metadata/measurement_type.csv) · P06 units UPOX
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 × station × the cruise's month × 10 m bin), so the Explorer can draw anomalies against it rather than values.
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.
By depth · by month 0–5,351 m · every month
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.
Cite the release, v2026.10.21
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.