The abundance and types of plankton present in an area influences the nature of the local food chain, and helps regulate the exchange of carbon dioxide gas between the ocean and atmosphere, which plays a role in the greenhouse effect. Nutrient availability peaks during the spring after winter storms have mixed cold, nutrient-rich waters near the surface. Sunlight is also increasing at this time. The simultaneous presence of ample sunlight and nutrients leads to a rapid growth in phytoplankton populations. This is called the spring bloom.
Plants contain a variety of pigments.
Chlorophyll a, found in all land plants, is the major photosynthetic pigment. It captures the energy found in red and blue wavelengths of light and uses it to produce glucose during photosynthesis. Oceanographers commonly measure the concentration of chlorophyll a to determine the amount of phytoplankton in their samples. In addition, oceanographers study the various accessory pigments found in the phytoplankton. Many of these pigments are found exclusively in one class of phytoplankton and can easily be used to determine if specific groups are present.