Functional group field guide

Phytoplankton

Microscopic photosynthetic organisms that support marine food webs and participate in global carbon cycling.

Last updated 2026-09-28 · Reviewed against listed sources
Group
Many lineages, including diatoms and cyanobacteria
Energy source
Sunlight in the euphotic zone
Role
Primary production and food-web support
What varies
Biomass, productivity, and community composition by place and season

How to read this guide

Use the quick facts on Phytoplankton to connect habitat, resource supply, movement and human pressure at the scale described here. A single status label cannot represent every Phytoplankton population, site or observation period.

What scientists are still studying

For Phytoplankton, distribution records and long-term monitoring are uneven across regions, while responses to temperature and resource availability can be measured in different ways. Treat the location and duration of observational gaps as part of the result.

Related learning

Sources checked

  • NASA Earth Observatory: Ocean Color
  • NOAA Ocean Service: Phytoplankton
  • Global Ocean Observing System: Ocean observations

Phytoplankton field guides page summarizes public scientific and institutional material. Values relevant to Phytoplankton may change with dataset, location, season and method, so comparisons should retain those conditions.

Ocean field notebook / field guides

Field plan: Phytoplankton

Microscopic photosynthetic organisms that support marine food webs and participate in global carbon cycling.

Station 01

System boundary

Track the chemical or biological rate being measured, the water mass sampled and the timescale over which the signal is expected to persist. Relate that field focus to “How to read this guide” before moving to “What scientists are still studying.”

Station 02

Measurements to log

Pair regional records that expose spatial variation with field observations made with consistent sampling effort. Record depth, location, date, units and sampling effort so a change in conditions is not mistaken for a change in the ocean.

Station 03

Change signal

Compare “What scientists are still studying” with “Related learning.” Decide whether the pattern represents exposure, response or recovery, and state the observation period needed to tell them apart.

Open the pre-dive checklist
  • Which variable can be observed directly?
  • Which mechanism needs a second instrument or comparison site?
  • What result from the page sources and linked institutional records would change the planned conclusion?