Fitoplankton

Fitoplankton are the photosynthetic component of planktonic communities in oceans, seas, and freshwater systems. They are microscopic organisms that drift with currents and derive energy from sunlight. The group includes diatoms, dinoflagellates, coccolithophores, green algae, and cyanobacteria. Most are single-celled, though some form colonies or chains. They require light and inorganic nutrients such as nitrate, phosphate, and trace metals.

Through photosynthesis, fitoplankton convert carbon dioxide into organic matter, forming the base of aquatic food webs. They support zooplankton and thus virtually all higher trophic levels, including commercially important fisheries. They also contribute significantly to global oxygen production and play a key role in the marine carbon cycle through the biological carbon pump, whereby carbon fixed by photosynthesis can be transported to deeper waters when organisms die and sink.

In oceans, phytoplankton populations are governed by light availability, nutrient supply, temperature, and water column mixing. Seasonal changes, upwelling, and stratification drive blooms, which can be rapid increases in biomass. Some blooms are benign, others produce toxins or create hypoxic conditions that harm wildlife and human activities. Harmful algal blooms are a particular concern in coastal regions and can affect drinking water and fisheries.

Study and monitoring often rely on chlorophyll-a measurements as a proxy for biomass, satellite remote sensing, microscopy, and molecular methods. Climate change and nutrient pollution influence phytoplankton distribution, community composition, and productivity, with potential impacts on carbon sequestration and food webs. In some languages, fitoplankton is the common term; in English, the standard term is phytoplankton.