Chlorophyll maximum
Chlorophyll-a at its maximum: the 3 m running mean at chl_max_depth
µg/Lkey chl_maxP06 units UGPLseries chl_max
one value per cast One value per cast. This measurement is worked out once for each cast rather than read at every depth, so it has no depth profile and no anomaly against a normal; its values are rows of sample_measurement, not of obs_env.
CalCOFI holds 9,255 values of it from 9,255 sampling events in one dataset, 1993–2026, one per cast.R Chlorophyll peaks at a depth rather than at the surface, and the height of that peak is how much plant life the water column holds at its richest layer: the base of the food web the rest of the survey counts.C
- 9,255
- values
- 0
- flagged
- 1993–2026
- years
- 1
- dataset
- 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
chl_max· source columnest_chlorophyll_a_sta_corrone value per cast sensor mean no flag at this grain no P01 concept
Explorerdb-queryThis page as JSON R · Python · Parquet
Every way in 6 ways · 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.
Explorerdb-querySELECT * FROM read_json('…/v2026.10.21/catalog.json')
-- objects[] WHERE table = 'sample_measurement'
-- then filter the rows:
-- measurement_type IN ('chl_max')library(calcofi4r)
con <- cc_get_db() # the promoted release
tbl(con, "sample_measurement") |> filter(measurement_type %in% c("chl_max"))import calcofi4py as cc
con = cc.cc_get_db()
con.sql("SELECT * FROM sample_measurement WHERE measurement_type IN ('chl_max')").df()The structure chlorophyll-a measured fluorometrically’s, standing in
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 Computed from the CTD fluorometer profile (corrected to bottle chlorophyll-a)
Chlorophyll-a at its maximum: the smoothed value (3 m running mean) at the depth of the maximum. (the record's own derivation (measurement_type.csv); questions Q02 (Rasmus Swalethorp, 2026-09-23))
- smooth the 1 m profile with a 3 m running mean
- take the highest smoothed value
Why it matters 4 ways to say it · EOV Phytoplankton biomass and diversity
the GOOS specification sheet for this Essential Ocean Variable lists it
other ways to say why · 3
- It is the smoothed value at the depth of the maximum, taken from the CTD fluorometer corrected to bottle chlorophyll-a, so a single narrow spike is not read as the peak. needs a citation before it can be the pick
- Wikipedia Chlorophyll a source
- Wikipedia The deep chlorophyll maximum (DCM), also called the subsurface chlorophyll maximum, is the region below the surface of water with the maximum concentration of chlorophyll. The DCM generally exists at the same depth as the nutricline, the region of the ocean where the greatest change in the nutrient concentration occurs with depth. Deep chlorophyll maximum · CC BY-SA 4.0 · rev. 1374126571
Units and range µg/L · 0 … 1000 declared · 0 flagged
µg/L (ug/L in metadata/measurement_type.csv) · P06 units UGPL
details
- bounds
- The registry declares
0 … 1000 µg/Lforchl_max; a value outside it is dropped at the ingest (drop_out_of_bounds()). - observed
- CTD Derived Products
chl_max0.0059 · median 0.7631 · 83.16 µg/L (5th–95th percentile 0.2528–6.356) - flags
- CTD Derived Products
chl_maxcarries no quality code at the release grain; qual_ok keeps all 9,255. - 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.
- derivation
- calcofi4db::ctd_chl_max(window_m = 3): the 3 m running mean of est_chlorophyll_a_sta_corr at chl_max_depth (questions Q02)
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 month every month
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 — CTD Derived Products. The Explorer's Share → Cite writes it for the view you make.