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Phytoplankton (/ ˌ f aɪ t oʊ ˈ p l æ ŋ k t ə n /) are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems.The name comes from the Greek words φυτόν (phyton), meaning 'plant', and πλαγκτός (planktos), meaning 'wanderer' or 'drifter'.
Phytoplankton need nitrogen in biologically available forms for the initial synthesis of organic matter. Ammonia and urea are released into the water by excretion from plankton. Nitrogen sources are removed from the euphotic zone by the downward movement of the organic matter. This can occur from sinking of phytoplankton, vertical mixing, or ...
Microorganisms preferentially consume oxygen in nitrate over phosphate leading to deeper oceanic waters having an N:P ratio of less than 16:1. From there, the ocean's currents upwell the nutrients to the surface where phytoplankton will consume the excess Phosphorus and maintain a N:P ratio of 16:1 by consuming N 2 via nitrogen fixation. [9]
Phytoplankton absorb energy from the Sun and nutrients from the water to produce their own nourishment or energy. In the process of photosynthesis, phytoplankton release molecular oxygen (O 2) into the water as a waste byproduct. It is estimated that about 50% of the world's oxygen is produced via phytoplankton photosynthesis. [61]
It has been estimated that half of the world's oxygen is produced by phytoplankton. [7] [8] Larger autotrophs, such as the seagrasses and macroalgae are generally confined to the littoral zone and adjacent shallow waters, where they can attach to the underlying substrate but still be within the photic zone.
Marine phytoplankton mostly inhabit sunlit surface waters as photoautotrophs, and require nutrients such as nitrogen and phosphorus, as well as sunlight to fix carbon and produce oxygen. However, some marine phytoplankton inhabit the deep sea, often near deep sea vents, as chemoautotrophs which use inorganic electron sources such as hydrogen ...
Ancestors of Prochlorococcus contributed to the production of early atmospheric oxygen. [26] Despite Prochlorococcus being one of the smallest types of marine phytoplankton in the world's oceans, its substantial number make it responsible for a major part of the oceans', world's photosynthesis, and oxygen production. [ 2 ]
Microalgae, capable of performing photosynthesis, are important for life on earth; they produce approximately half of the atmospheric oxygen [2] and use the greenhouse gas carbon dioxide to grow photoautotrophically. "Marine photosynthesis is dominated by microalgae, which together with cyanobacteria, are collectively called phytoplankton."