What is phytoplankton? Most phytoplankton are too small to be seen with the naked eye. However, in high enough quantities, some species can be seen as colored spots on the surface of the water, due to the content of chlorophyll inside their cells and auxiliary pigments such as phycobiliproteins or xanthophylls.
What is phytoplankton
Phytoplankton are photosynthetic microscopic biotic organisms that live in the upper water layer of almost all oceans and lakes on Earth. They are the creators of organic compounds from carbon dioxide dissolved in water - that is, the initiators of the process that maintains the aquatic food web.
Photosynthesis
Phytoplankton obtain energy through photosynthesis and therefore must live in a well-lit surface layer (called the euphotic zone) of an ocean, sea, lake or other body of water. Phytoplankton makes up about half of allphotosynthetic activity on earth. Its cumulative fixation of energy in carbon compounds (primary production) is the basis for the vast majority of oceanic and many freshwater food chains (chemosynthesis being a notable exception).
Unique Species
Although almost all species of phytoplankton are exceptional photoautotrophs, there are some that are mitotrophs. These are usually non-pigmented species that are actually heterotrophic (the latter are often considered zooplankton). The best known are the dinoflagellar genera such as Noctiluca and Dinophysis, which obtain organic carbon by ingesting other organisms or detrital material.
Meaning
Phytoplankton absorb energy from the sun and nutrients from the water to produce their own food. During photosynthesis, molecular oxygen (O2) is released into the water. It is estimated that about 50% or 85% of the world's oxygen comes from the photosynthesis of phytoplankton. The rest is produced by photosynthesis by land plants. To understand what phytoplankton is, you need to be aware of its great importance for nature.
Relationship with minerals
Phytoplankton are critically dependent on minerals. These are primarily macronutrients such as nitrate, phosphate or silicic acid, the availability of which is determined by the balance between the so-called biological pump and the rise of deep, nutrient-rich waters. However, in large areasIn oceans such as the Southern Ocean, phytoplankton are also limited by the lack of micronutrient iron. This has led some scientists to advocate fertilization of iron as a means of counteracting the accumulation of human-produced carbon dioxide (CO2) in the atmosphere.
Scientists have been experimenting with adding iron (usually in the form of s alts such as ferrous sulfate) to the water to encourage phytoplankton growth and remove atmospheric CO2 into the ocean. However, disputes over ecosystem management and iron fertilization efficiency have slowed down such experiments.
Variety
The term "phytoplankton" covers all photoautotrophic microorganisms in aquatic food chains. However, unlike terrestrial communities where most autotrophs are plants, phytoplankton are a diverse group including protozoan eukaryotes such as eubacterial and archaebacterial prokaryotes. There are about 5,000 known species of marine phytoplankton. How this diversity evolved despite limited food resources is not yet clear.
The most important groups of phytoplankton include diatoms, cyanobacteria and dinoflagellates, although many other groups of algae are represented in this highly diverse group. One group, the coccolithophorids, are responsible (in part) for releasing significant amounts of dimethyl sulfide (DMS) into the atmosphere. DMS oxidizes to form sulfate, which in areas of low concentration of aerosol particles cancontribute to the emergence of special areas of air condensation, which mainly leads to an increase in cloudiness and fog above the water. This property is also characteristic of lake phytoplankton.
All types of phytoplankton support different trophic (i.e. food) levels in different ecosystems. In oligotrophic oceanic regions such as the Sargasso Sea or the South Pacific Ocean, the most common phytoplankton are small, single-celled species called picoplankton and nanoplankton (also called picoflagellates and nanoflagellates). Basically, phytoplankton refers to cyanobacteria (Prochlorococcus, Synechococcus) and picoeukaryotes such as Micromonas. In more productive ecosystems, large dinoflagellates are the basis of phytoplankton biomass.
Influence on the chemical composition of water
In the early twentieth century, Alfred C. Redfield found similarities between the elemental composition of phytoplankton and the major dissolved nutrients in the deep ocean. Redfield suggested that the ratio of carbon to nitrogen to phosphorus (106:16:1) in the ocean is controlled by the demands of phytoplankton, as the phytoplankton subsequently release nitrogen and phosphorus as they remineralize. This so-called "Redfield ratio" in describing the stoichiometry of phytoplankton and seawater has become a fundamental principle for understanding the evolution of marine ecology, biogeochemistry, and what phytoplankton are. However, the Redfield coefficient is not a universal value and may diverge due to changes in the composition of exogenous nutrients and microbes.in the ocean. The production of phytoplankton, as the reader should already understand, affects not only the level of oxygen, but also the chemical composition of ocean water.
Biological features
The dynamic stoichiometry inherent in unicellular algae reflects their ability to store nutrients in an internal reservoir and change the composition of the osmolite. Different cellular components have their own unique stoichiometric characteristics, for example, resource (light or nutrient) data-gathering devices such as proteins and chlorophyll contain a high concentration of nitrogen but a low content of phosphorus. Meanwhile, genetic growth mechanisms such as ribosomal RNA contain high concentrations of nitrogen and phosphorus (N and P, respectively). The phytoplankton-zooplankton food chain, despite the difference between these two types of creatures, is the basis of the ecology of water spaces throughout the planet.
Life cycles
Based on the distribution of resources, phytoplankton are classified into three life stages: survival, flowering, and consolidation. The surviving phytoplankton have a high N:P (nitrogen and phosphorus) ratio (> 30) and contain many resource gathering mechanisms to sustain growth when resources are scarce. Blooming phytoplankton have a low N:P ratio (<10) and are adapted to exponential growth. Consolidated phytoplankton have a similar N: P to Redfield ratio and contain a relatively equal ratio of growth and resource accumulation mechanisms.
Present and future
A study published in Nature in 2010 found that marine phytoplankton have declined substantially in the world's oceans over the past century. Phytoplankton concentrations in surface waters are estimated to have decreased by about 40% since 1950 at a rate of about 1% per year, possibly in response to ocean warming. The study sparked controversy among scientists and led to heated debates. In a subsequent 2014 study, the authors used a large database of measurements and revised their analysis methods to address several published criticisms, but ended up with similarly disturbing conclusions: Phytoplankton algae numbers are rapidly declining.
