Photosynthetic pigment at 400-530 nm. However, none of the pigments absorbs well in the green-yellow region, which is responsible for the abundant green we see in nature. Like plants, the cyanobacteria use water as an electron donor for photosynthesis and therefore liberate oxygen; they also use chlorophyll as a pigment. In addition, most cyanobacteria use phycobiliproteins, water-soluble pigments which occur in the cytoplasm of the chloroplast, to capture light energy and pass it on to the chlorophylls. (Some cyanobacteria, the prochlorophytes, use chlorophyll b instead of phycobilin.) It is thought that the chloroplasts in plants and algae all evolved from cyanobacteria. Several
Deep chlorophyll maximum of phytoplankton that have adapted to functioning in low light conditions. To adapt to low light conditions, some phytoplankton populations have been found to have increased amounts of chlorophyll counts per cell, which contributes to the formation of the DCM. Rather than an increase of overall cell numbers, seasonal light limitation or low irradiance levels can raise the individual cellular chlorophyll content. As depth increases within the mixing zone, phytoplankton must rely on having higher pigment counts (chlorophyll) to capture photic energy. Due to the higher concentration of chlorophyll in the phtoplankton present, the DCM does not predict the depth