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What is Phytoplankton?

Phytoplankton Meaning

To provide the Phytoplankton definition, we can say that Phytoplankton is a type of autotrophic (self-feeding) plankton that is found in both ocean and freshwater habitats. Phytoplankton, including trees and other land plants, get their energy from photosynthesis. This implies phytoplankton needs sunlight to survive, therefore they reside in lakes and oceans' well-land surface layers (euphotic zone).

Phytoplankton definition states that, in contrast to terrestrial plants, is spread over a greater surface area, is subjected towards less seasonal variation and has much higher turnover rates than trees (days versus decades). As a consequence, phytoplankton reacts to climate change quickly on a global scale. Phytoplankton examples are important players in the global carbon cycle that lay the backbone of freshwater and marine food webs. Despite accounting for just approximately 1% of global plant biomass, these make up roughly half of global photosynthetic activity and half of the global oxygen production.

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Photosynthesising bacteria, phytoplankton algae, and armour-plated coccolithophores are all phytoplankton examples. The cyanobacteria, diatoms, and dinoflagellates are among the most important phytoplankton species, but there are many others. The majority of phytoplankton is too tiny to be observed individually with the naked eye. Nevertheless, due to the existence of chlorophyll inside their cells and accessory pigments (including xanthophylls or phycobiliproteins) in certain species, some varieties can appear as coloured patches on the water surface whenever present in sufficient numbers.


Now you know what is phytoplankton or phytoplankton meaning. Let’s take a look into the types. Phytoplankton is photosynthetic microscopic biotic species that live in the top sunlit layer of most oceans and freshwater bodies on the planet. These are primary producers or organisms that create organic compounds from carbon dioxide mixed with water, a mechanism that keeps the aquatic food web afloat.


Photosynthesis provides energy to phytoplankton, so they must survive in the well-lit outer surface (dubbed the euphotic zone) of a sea, ocean, lake, and other such body of water. Around half of all photosynthetic activity on Earth is attributed to phytoplankton. The large proportion of oceanic and several freshwater food webs are based on their accumulated energy fixation through carbon compounds (primary production).

Although almost every phytoplankton species are obligate photoautotrophs, a few are mixotrophic, and some are heterotrophic because they are not pigmented. Dinoflagellate genera including Dinophysis and Noctiluca, which acquire organic carbon by swallowing certain organisms or detrital material, are the most well-known.

Phytoplankton is found in the ocean's photic zone, where photosynthesis is feasible. They absorb carbon dioxide and release oxygen throughout photosynthesis. Photodegradation of phytoplankton can occur when solar radiation is too strong. Phytoplankton cells need nutrients to expand, that come from continental weathering, rivers, and glacial ice meltwater at the ends. Dissolved organic carbon (DOC) is introduced further into the ocean by phytoplankton. Phytoplankton act as prey for fish larvae, zooplankton, as well as other heterotrophic species because they are the foundation of marine food webs. Bacteria and viral lysis may also break them down.

While some phytoplankton cells, including dinoflagellates, can migrate vertically, these cannot aggressively move against currents, therefore these sink gradually and eventually fertilise the seafloor containing dead cells and detritus.

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Both photoautotrophic microorganisms in aquatic food chains are referred to as phytoplankton. With exception of terrestrial ecosystems, wherein plants are the majority of autotrophs, phytoplankton is a complex community that includes protistan eukaryotes as well as eubacterial and archaebacterial prokaryotes. Approximately 5,000 species of marine phytoplankton have been identified. It's questionable how this diversity arose in the face of limited resources (restricting niche differentiation).

While several other types of algae are described, cyanobacteria, the diatoms, and dinoflagellates are by far the most common classes of phytoplankton in terms of numbers.

The coccolithophorids, for example, are responsible for releasing large quantities of dimethyl sulphide into the atmosphere. As per the CLAW Hypothesis, DMS is oxidised to form sulphate, which may lead to the population of cloud condensation nuclei throughout areas where atmospheric aerosol particle concentrations remain low, resulting in greater cloud cover and cloud albedo.

Under different habitats, different forms of phytoplankton support various trophic levels. Picoplankton and nanoplankton (often known as picoflagellates and nanoflagellates) are inhabited by picoeukaryotes and cyanobacteria including Micromonas in oligotrophic oceanic regions like that of the Sargasso Sea and the South Pacific Gyre.

Larger dinoflagellates seem to be the leading phytoplankton in some more active environments controlled by upwelling or higher terrestrial inputs, and they represent a greater proportion of the biomass.

Factors Affecting Abundance

Scientists from NASA and Oregon State University collaborated on the NAAMES project, which lasted five years and explored elements of phytoplankton dynamics in marine ecosystems, as well as how these dynamics affect atmospheric clouds, aerosols, and climate (The full form of NAAMES is North Atlantic Aerosols and Marine Ecosystems Study). The research centred on the North Atlantic Ocean's sub-arctic zone, which hosts one of the nation's biggest recurring phytoplankton blooms.

The North Atlantic was an excellent place to evaluate prevailing scientific theories in an effort to comprehend the position of phytoplankton aerosol emissions on Earth's energy budget because of its long record of study and convenient accessibility.

NAAMES was created to study particular periods of the annual phytoplankton cycle, such as the minimum, climax, and intermediate reducing and rising biomass, in terms of solving disputes about bloom formation scheduling and the trends that drive annual bloom re-creation.

Role of Phytoplankton

The atmospheric inorganic compounds, gas composition, and trace element fluxes, and also the transport and rotation of organic material through biological processes, are all influenced by phytoplankton. Throughout the surface ocean, photosynthetically fixed carbon is quickly reused or recycled, whereas a portion of this biomass is transported as sinking particles to the ocean floor, in which it undergoes continuing transformation processes such as remineralization.


Phytoplankton is an important food source in mariculture and aquaculture. Both of these use phytoplankton as a source of nutrition for their farm animals. Phytoplankton seems to be a naturally found organism that is brought into enclosures by regular seawater circulation. Phytoplankton should be harvested and incorporated directly into aquaculture. Plankton may be harvested from a water body or cultured, but the latter approach is seldom employed. Phytoplankton has been used as a food source for rotifers, which then eat other certain species. Few types of aquacultured mollusks, such as giant clams and pearl oysters, are fed phytoplankton.

Using ocean-colour data from satellites, a 2018 report suggested the nutritional quality of natural phytoplankton in respect of protein, carbohydrate, and lipid throughout the world ocean, and discovered that the calorie content of phytoplankton varies significantly across oceanic regions and seasons.

Aquaculture is described as the development of phytoplankton within laboratory circumstances. Phytoplankton is grown for a number of reasons, such as a food source for aquaculture species and as a dietary supplement for captive invertebrates in aquariums. Small-scale laboratory colonies of less than 1L to commercial aquaculture cultures of many tens of thousands of litres are all possible.

Interesting Facts about Phytoplankton

Interesting facts about phytoplankton: Phytoplankton not only serve as the foundation of the food chain, but they also play an important part in the global carbon cycle. Phytoplankton extract carbon dioxide from seawater throughout photosynthesis, producing energy as a by-product, yet preserving the carbon in organic compounds.

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FAQs on Phytoplankton

1. Define Plankton Bloom.

Ans. Plankton blooms are a natural occurrence, seen in the ocean. Phytoplankton, microscopic plants which float throughout the ocean's upper, sunlit waters, are to blame. The colour of the water surface varies whenever significant numbers of phytoplankton congregate in one region. Coccolithophores are a unique type of plankton.

2. Is it Possible to Live without Plankton?

Ans. Plankton is the foundation of the aquatic food web; without it, all larger species will perish. For millions around the world, no plankton means no fish, which means no food.