Chlorophyll-a
Chlorophyll-a measured fluorometrically
µg/Lkey chlorophyll_aNERC P01 CPHLZZXXP06 units UGPLseries chlorophyll_a
CalCOFI holds 245,666 values of it from 13,934 sampling events in one dataset, 1973–2021, from the surface to 1,122 m. At 10–50 m it has risen 0.03 per decade since 1984.R Every phytoplankter carries chlorophyll-a, so it is the standard measure of how much plant life the sunlit layer holds: the base of the food web the rest of the survey counts.C
- 245,666
- values
- 610
- flagged
i
610 of these 245,666 values (0.2 %) 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). - 1973–2021
- years
- 1
- dataset
- 0–1,122 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
chlorophyll_a· source columnchlor_a· flag columnchlqua610 flagged · 0.2 %
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 = 'chlorophyll_a'library(calcofi4r)
con <- cc_get_db() # the promoted release
tbl(con, "obs_env") |> filter(measurement_type %in% c("chlorophyll_a"))import calcofi4py as cc
con = cc.cc_get_db()
con.sql("SELECT * FROM obs_env WHERE measurement_type IN ('chlorophyll_a')").df()The structure 2 structures
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 Filter, 90% acetone extraction, benchtop fluorometer
A known volume filtered onto a GF/F filter, cold-extracted in 90% acetone for 24-48 hours and read on a fluorometer; the extract is then acidified, which strips the magnesium and turns chlorophyll into phaeopigment, and read again (Yentsch & Menzel 1963; Holm-Hansen et al. 1965; Lorenzen 1967). (calcofi.org Bottle sampling methods)
Bottle sampling methods on calcofi.org ↗Why it matters 5 ways to say it · EOV Phytoplankton biomass and diversity
the GOOS specification sheet for this Essential Ocean Variable lists it, and asks
GOOS asks
- Is the biomass of the ocean changing?
GOOS specification sheet ↗ · quoted, not copied
other ways to say why · 4
- Chlorophyll is what satellites see as ocean colour, and bottle chlorophyll like CalCOFI’s is among the ground truth their algorithms were fitted to. needs a citation before it can be the pick
- GOOS asks Is the biomass of the ocean changing? source
- Wikipedia Phytoplankton source
- Wikipedia Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. Chlorophyll a · CC BY-SA 4.0 · rev. 1373717553
The record’s own history 5 depth bands against the 1993–2013 normal
Each year against the normal i
Deeper than the climatology reaches: 49 values at 500–1000 m, 26 values at 1000–2000 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: 49 values at 500–1000 m, 26 values at 1000–2000 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 µg/L · at least -1 declared · 610 flagged
µg/L (ug/L in metadata/measurement_type.csv) · P06 units UGPL
details
- bounds
- The registry declares
at least -1 µg/Lforchlorophyll_a; a value outside it is dropped at the ingest (drop_out_of_bounds()). - observed
- Hydrographic Bottle
chlorophyll_a-0.001 · median 0.16 · 66.11 µg/L (5th–95th percentile 0–1.69) - flags
- Hydrographic Bottle
chlorophyll_achlquaon 610 of 245,666 rows:897 ·9513; qual_ok keeps 245,056. 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 0–1,122 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.