Chlorophyll a

Temporal coverage: 02 July 2013 - Present

The MODIS Chlorophyll a layer provides the near-surface concentration of chlorophyll a in milligrams of chlorophyll pigment per cubic meter (mg/m³) in the ocean. Chlorophyll is a light harvesting pigment found in most photosynthetic organisms. In the ocean, phytoplankton all contain the chlorophyll pigment, which has a greenish color. Derived from the Greek words phyto (plant) and plankton (made to wander or drift), phytoplankton are microscopic organisms that live in watery environments, both salty and fresh. Some phytoplankton are bacteria, some are protists, and most are single-celled plants.The concentration of chlorophyll a is used as an index of phytoplankton biomass. Phytoplankton fix carbon through photosynthesis, taking in dissolved carbon dioxide in the sea water and producing oxygen, enabling phytoplankton to grow. Changes in the amount of phytoplankton indicate the change in productivity of the ocean and as marine phytoplankton capture almost an equal amount of carbon as does photosynthesis by land vegetation, it provides an ocean link to global climate change modeling. The MODIS Chlorophyll a product is therefore a useful product for assessing the “health” of the ocean. The presence of phytoplankton indicates sufficient nutrient conditions for phytoplankton to flourish, but harmful algal blooms (HABs) can result when high concentrations of phytoplankton produced toxins build up. Known as red tides, blue-green algae or cyanobacteria, harmful algal blooms have severe impacts on human health, aquatic ecosystems and the economy. Chlorophyll features can also be used to trace oceanographic currents, atmospheric jets/streams and upwelling/downwelling/river plumes. Chlorophyll concentration is also useful for studying the Earth’s climate system as it is plays an integral role in the Global Carbon Cycle. More phytoplankton in the ocean may result in a higher capture rate of carbon dioxide into the ocean and help cool the planet.

The MODIS Chlorophyll a product is available from both the Terra and Aqua satellites. The sensor and imagery resolution is 1 km, and the temporal resolution is daily.

References: Earthdata Search: MODISA_L2_OC; OceanColor Web - Level 1&2 Browsers; OceanColor Web - Chlorophyll a; NASA Earth Observations - Chlorophyll Concentration