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However, when porphyrin-based photoautotrophs evolved and started to photosynthesize, which included both the primitive purple bacteria using bacteriochlorophyll and cyanobacteria using chlorophyll, highly reactive dioxygen was released as a byproduct of water splitting and started to accumulate, first in the ocean and then in the atmosphere.
Chlorophyll b is made by the same enzyme acting on chlorophyllide b. The same is known for chlorophyll d and f, both made from corresponding chlorophyllides ultimately made from chlorophyllide a. [39] In Angiosperm plants, the later steps in the biosynthetic pathway are light-dependent. Such plants are pale if grown in darkness.
Ocean chlorophyll concentration as a proxy for marine primary production. Green indicates where there are a lot of phytoplankton, while blue indicates where there are few phytoplankton. – NASA Earth Observatory 2019. [1] Marine primary production is the chemical synthesis in the ocean of organic compounds from atmospheric or dissolved carbon ...
Chlorophyll a, b, and d. Chlorophyll synthase [14] completes the biosynthesis of chlorophyll a by catalysing the reaction EC 2.5.1.62. chlorophyllide a + phytyl diphosphate chlorophyll a + diphosphate. This forms an ester of the carboxylic acid group in chlorophyllide a with the 20-carbon diterpene alcohol phytol.
In 2010, a fifth type of chlorophyll, namely chlorophyll f, was discovered by Min Chen from stromatolites in Shark Bay. [40] Halococcus hamelinensis , a halophilic archaeon , occurs in living stromatolites in Shark Bay where it is exposed to extreme conditions of UV radiation, salinity and desiccation . [ 41 ]
The tiny (0.6 μm) marine cyanobacterium Prochlorococcus, discovered in 1986, forms today an important part of the base of the ocean food chain and accounts for much of the photosynthesis of the open ocean [84] and an estimated 20% of the oxygen in the Earth's atmosphere. [85]
Ocean salinity is derived mainly from the weathering of rocks and the transport of dissolved salts from the land, with lesser contributions from hydrothermal vents in the seafloor. [12] Evaporation of ocean water and formation of sea ice further increase the salinity of the ocean.
The ocean is the body of salt water that covers approximately 70.8% of Earth. [8] In English, the term ocean also refers to any of the large bodies of water into which the world ocean is conventionally divided. [9] The following names describe five different areas of the ocean: Pacific, Atlantic, Indian, Antarctic/Southern, and Arctic.