![Global ocean chlorophyll concentration October 2019](https://upload.wikimedia.org/wikipedia/commons/e/e0/Global_ocean_chlorophyll_concentration_October_2019.png)
Marine primary production is the chemical synthesis in the ocean of
organic compound
In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...
s from atmospheric or dissolved
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
. It principally occurs through the process of
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
, which uses light as its source of energy, but it also occurs through
chemosynthesis
In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydro ...
, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all
life
Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energ ...
on Earth relies directly or indirectly on
primary production
In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through c ...
. The organisms responsible for primary production are called
primary producers
An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Work ...
or
autotroph
An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Works", ...
s.
Most marine primary production is generated by a diverse collection of
marine microorganisms
Marine microorganisms are defined by their habitat as microorganisms living in a marine environment, that is, in the saltwater of a sea or ocean or the brackish water of a coastal estuary. A microorganism (or microbe) is any microscopic livin ...
called
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
and
cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
. Together these form the principal primary producers at the base of the
ocean food chain and produce half of the world's oxygen. Marine primary producers underpin almost all marine animal life by generating nearly all of the oxygen and food marine animals need to exist. Some marine primary producers are also
ecosystem engineers which change the environment and provide
habitats for other marine life.
Primary production in the ocean can be contrasted with primary production on land. Globally the ocean and the land each produce about the same amount of primary production, but in the ocean primary production comes mainly from cyanobacteria and algae, while on land it comes mainly from
vascular plant
Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...
s.
Marine algae includes the largely invisible and often
unicellular
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...
microalgae, which together with
cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
form the ocean
phytoplankton
Phytoplankton () 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 (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'.
Ph ...
, as well as the larger, more visible and complex
multicellular
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...
macroalgae
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
commonly called
seaweed
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
. Seaweeds are found along coastal areas, living on the floor of
continental shelves and washed up in
intertidal zone
The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...
s. Some seaweeds drift with plankton in the sunlit surface waters (
epipelagic zone
The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...
) of the open ocean. Back in the
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
, some phytoplankton evolved into
red
Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...
,
brown
Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing or painting, brown is usually made by combining the colors orange and black. In the RGB color model us ...
and
green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
. These algae then invaded the land and started evolving into the
land plant
The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as sist ...
s we know today. Later in the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
some of these land plants returned to the sea as
mangrove
A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
s and
seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...
es. These are found along coasts in
intertidal regions and in the brackish water of
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
. In addition, some seagrasses, like seaweeds, can be found at depths up to 50 metres on both soft and hard bottoms of the continental shelf.
Marine primary producers
Primary producer
Primary or primaries may refer to:
Arts, entertainment, and media Music Groups and labels
* Primary (band), from Australia
* Primary (musician), hip hop musician and record producer from South Korea
* Primary Music, Israeli record label
Works
...
s are the
autotroph
An autotroph or primary producer is an organism that produces complex organic compounds (such as carbohydrates, fats, and proteins) using carbon from simple substances such as carbon dioxide,Morris, J. et al. (2019). "Biology: How Life Works", ...
organisms that make their own food instead of eating other organisms. This means primary producers become the starting point in the
food chain
A food chain is a linear network of links in a food web starting from producer organisms (such as grass or algae which produce their own food via photosynthesis) and ending at an apex predator species (like grizzly bears or killer whales), det ...
for
heterotroph
A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
organisms that do eat other organisms. Some marine primary producers are specialised bacteria and archaea which are
chemotroph
A Chemotroph is an organism that obtains energy by the oxidation of electron donors in their environments. These molecules can be organic ( chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototro ...
s, making their own food by gathering around
hydrothermal vents
A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...
and
cold seeps
A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. ''Cold'' does not mean that the temperature of the see ...
and using
chemosynthesis
In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydro ...
. However, most marine
primary production
In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through c ...
comes from organisms which use
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
on the carbon dioxide dissolved in the water. This process uses energy from sunlight to convert water and
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells.
Marine primary producers are important because they underpin almost all marine animal life by generating most of the
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
and food that provide other organisms with the chemical energy they need to exist.
The principal marine primary producers are
cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
,
algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
and marine plants. The
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
released as a by-product of photosynthesis is needed by
nearly all living things to carry out
cellular respiration
Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be des ...
. In addition, primary producers are influential in the global
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
and
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
cycles. They stabilize coastal areas and can provide habitats for marine animals. The term
division
Division or divider may refer to:
Mathematics
*Division (mathematics), the inverse of multiplication
*Division algorithm, a method for computing the result of mathematical division
Military
*Division (military), a formation typically consisting ...
has been traditionally used instead of
phylum
In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature f ...
when discussing primary producers, although the
now accepts the terms as equivalent.
In a reversal of the pattern on land, in the oceans, almost all photosynthesis is performed by algae and cyanobacteria, with a small fraction contributed by
vascular plants
Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...
and other groups. Algae encompass a diverse range of organisms, ranging from single floating cells to attached
seaweeds
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
. They include photoautotrophs from a variety of groups.
Eubacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
are important photosynthetizers in both oceanic and terrestrial ecosystems, and while some
archaea
Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...
are
phototroph
Phototrophs () are organisms that carry out photon capture to produce complex organic compounds (e.g. carbohydrates) and acquire energy. They use the energy from light to carry out various cellular metabolic processes. It is a common misconcep ...
ic, none are known to utilise oxygen-evolving photosynthesis.
A number of
eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
s are significant contributors to primary production in the ocean, including
green alga
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
e,
brown alga
Brown algae (singular: alga), comprising the class (biology), class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the ...
e and
red alga
Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...
e, and a diverse group of unicellular groups. Vascular plants are also represented in the ocean by groups such as the
seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...
es.
Unlike terrestrial ecosystems, the majority of primary production in the ocean is performed by free-living
microscopic organisms
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
called
phytoplankton
Phytoplankton () 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 (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'.
Ph ...
. It has been estimated that half of the world's oxygen is produced by phytoplankton.
Larger autotrophs, such as the seagrasses and macroalgae (
seaweed
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
s) are generally confined to the
littoral
The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal a ...
zone and adjacent shallow waters, where they can
attach to the underlying substrate but still be within the
photic zone. There are exceptions, such as ''
Sargassum
''Sargassum'' is a genus of brown (class Phaeophyceae) macroalgae ( seaweed) in the order Fucales. Numerous species are distributed throughout the temperate and tropical oceans of the world, where they generally inhabit shallow water and coral ...
'', but the vast majority of free-floating production takes place within microscopic organisms.
The factors limiting primary production in the ocean are also very different from those on land. The availability of water, obviously, is not an issue (though its
salinity
Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...
can be). Similarly, temperature, while affecting
metabolic
Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
rates (see
Q10), ranges less widely in the ocean than on land because the
heat capacity
Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K).
Heat capacity i ...
of seawater buffers temperature changes, and the formation of
sea ice
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oce ...
insulates it at lower temperatures. However, the availability of light, the source of energy for photosynthesis, and mineral
nutrients
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...
, the building blocks for new growth, play crucial roles in regulating primary production in the ocean.
Available Earth System Models suggest that ongoing ocean bio-geochemical changes could trigger reductions in ocean NPP between 3% and 10% of current values depending on the emissions scenario.
In 2020 researchers reported that measurements over the last two decades of primary production in the
Arctic Ocean
The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...
show an increase of nearly 60% due to higher concentrations of
phytoplankton
Phytoplankton () 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 (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'.
Ph ...
. They hypothesize new nutrients are flowing in from other oceans and suggest this means the Arctic ocean may be able to support
higher trophic level production and additional
carbon fixation
Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. The compounds are then used to store energy and as ...
in the future.
Cyanobacteria
Cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
are a phylum (division) of bacteria, ranging from unicellular to
filamentous and including
colonial species, which
fix inorganic carbon into organic carbon compounds. They are found almost everywhere on earth: in damp soil, in both freshwater and marine environments, and even on Antarctic rocks.
In particular, some species occur as drifting cells floating in the ocean, and as such were amongst the first of the
phytoplankton
Phytoplankton () 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 (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'.
Ph ...
. These bacteria function like algae in that they can process nitrogen from the atmosphere when none is in the ocean.
![Cyanobacteria guerrero negro](https://upload.wikimedia.org/wikipedia/commons/c/c0/Cyanobacteria_guerrero_negro.jpg)
The first primary producers that used photosynthesis were oceanic
cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
about 2.3 billion years ago. The release of molecular
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
by
cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
as a by-product of photosynthesis induced global changes in the Earth's environment. Because oxygen was toxic to most life on Earth at the time, this led to the near-extinction of
oxygen-intolerant organisms, a
dramatic change which redirected the evolution of the major animal and plant species.
![Prochlorococcus marinus (cropped)](https://upload.wikimedia.org/wikipedia/commons/6/67/Prochlorococcus_marinus_%28cropped%29.jpg)
The tiny marine cyanobacterium ''
Prochlorococcus
''Prochlorococcus'' is a genus of very small (0.6 μm) marine cyanobacteria with an unusual pigmentation ( chlorophyll ''a2'' and ''b2''). These bacteria belong to the photosynthetic picoplankton and are probably the most abundant photosynth ...
'', discovered in 1986, forms today part of the base of the ocean
food chain
A food chain is a linear network of links in a food web starting from producer organisms (such as grass or algae which produce their own food via photosynthesis) and ending at an apex predator species (like grizzly bears or killer whales), det ...
and accounts for more than half the photosynthesis of the open ocean and an estimated 20% of the oxygen in the Earth's atmosphere.
It is possibly the most plentiful genus on Earth: a single millilitre of surface seawater may contain 100,000 cells or more.
Originally, biologists thought
cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...
was algae, and referred to it as "blue-green algae". The more recent view is that cyanobacteria are bacteria, and hence are not even in the same
Kingdom
Kingdom commonly refers to:
* A monarchy ruled by a king or queen
* Kingdom (biology), a category in biological taxonomy
Kingdom may also refer to:
Arts and media Television
* ''Kingdom'' (British TV series), a 2007 British television drama s ...
as algae. Most authorities exclude all
prokaryotes
A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Connec ...
, and hence cyanobacteria from the definition of algae.
Biological pigments
Biological pigment
Biological pigments, also known simply as pigments or biochromes, are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments. Many biol ...
s are any coloured material in plant or animal cells. All biological pigments selectively
absorb certain wavelengths of light while
reflecting others.
[Lee, DW (2007) Nature's palette - the science of plant color. University of Chicago Press] The primary function of pigments in plants is
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
, which uses the green pigment
chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
and several colorful pigments that absorb as much light energy as possible.
Chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
is the primary pigment in plants; it is a
chlorin
In organic chemistry, chlorins are tetrapyrrole pigments that are partially hydrogenated porphyrins. The parent chlorin is an unstable compound which undergoes air oxidation to porphine.
The name chlorin derives from chlorophyll. Chlorophyll ...
that absorbs yellow and blue wavelengths of light while reflecting
green
Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...
. It is the presence and relative abundance of chlorophyll that gives plants their green color.
Green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
and plants possess two forms of this pigment: chlorophyll ''a'' and chlorophyll ''b''.
Kelp
Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms.
Kelp grows in "underwat ...
s,
diatom
A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...
s, and other photosynthetic
heterokont
Heterokonts are a group of protists (formally referred to as Heterokonta, Heterokontae or Heterokontophyta). The group is a major line of eukaryotes. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which ...
s contain chlorophyll ''c'' instead of ''b'', while red algae possess only chlorophyll ''a''. All chlorophylls serve as the primary means plants use to intercept light in order to fuel photosynthesis.
Chloroplasts
Chloroplast
A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...
s (from the Greek ''chloros'' for green, and ''plastes'' for "the one who forms"
) are
organelle
In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' the ...
s that conduct
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
, where the photosynthetic pigment
chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
captures the
energy
In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...
from
sunlight
Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...
, converts it, and stores it in the energy-storage molecules while freeing
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
from water in
plant
Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
and
algal
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
cells. They then use the stored energy to make organic molecules from
carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
in a process known as the
Calvin cycle
The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...
.
A chloroplast is a type of organelle known as a
plastid
The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a membrane-bound organelle found in the Cell (biology), cells of plants, algae, and some other eukaryotic organisms. They are considered to be intracellular endosy ...
, characterized by
its two membranes and a high concentration of
chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
. They are highly dynamic—they circulate and are moved around within plant cells, and occasionally
pinch in two to reproduce. Their behavior is strongly influenced by environmental factors like light color and intensity. Chloroplasts, like
mitochondria
A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...
, contain their own
DNA, which is thought to be inherited from their ancestor—a photosynthetic
cyanobacterium
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blue ...
that was
engulfed by an early
eukaryotic
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
cell. Chloroplasts cannot be made by the plant cell and must be inherited by each daughter cell during cell division.
Most chloroplasts can probably be traced back to a single
endosymbiotic event
An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualism (biology), mutualistic relationship.
(The term endosymbiosis is from the Greek language, G ...
, when a cyanobacterium was engulfed by the eukaryote. Despite this, chloroplasts can be found in an extremely wide set of organisms, some not even directly related to each other—a consequence of many
secondary and even
tertiary endosymbiotic events
An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship.
(The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within" ...
.
Microbial rhodopsin
Phototrophic metabolism relies on one of three energy-converting pigments:
chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...
,
bacteriochlorophyll
Bacteriochlorophylls (BChl) are photosynthetic pigments that occur in various phototrophic bacteria. They were discovered by C. B. van Niel in 1932. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanobact ...
, and
retinal
Retinal (also known as retinaldehyde) is a polyene chromophore. Retinal, bound to proteins called opsins, is the chemical basis of visual phototransduction, the light-detection stage of visual perception (vision).
Some microorganisms use retin ...
. Retinal is the
chromophore found in
rhodopsin
Rhodopsin, also known as visual purple, is a protein encoded by the RHO gene and a G-protein-coupled receptor (GPCR). It is the opsin of the rod cells in the retina and a light-sensitive receptor protein that triggers visual phototransduction ...
s. The significance of chlorophyll in converting light energy has been written about for decades, but phototrophy based on retinal pigments is just beginning to be studied.
![Salt ponds SF Bay (dro!d)](https://upload.wikimedia.org/wikipedia/commons/2/22/Salt_ponds_SF_Bay_%28dro%21d%29.jpg)
In 2000 a team of microbiologists led by
Edward DeLong
Edward Francis DeLong (born 1958), is a marine microbiologist and professor in the Department of Oceanography at the University of Hawaii, Manoa, and is considered a pioneer in the field of metagenomics. He is best known for his discovery of th ...
made a crucial discovery in the understanding of the marine carbon and energy cycles. They discovered a gene in several species of bacteria
responsible for production of the protein
rhodopsin
Rhodopsin, also known as visual purple, is a protein encoded by the RHO gene and a G-protein-coupled receptor (GPCR). It is the opsin of the rod cells in the retina and a light-sensitive receptor protein that triggers visual phototransduction ...
, previously unheard of in bacteria. These proteins found in the cell membranes are capable of converting light energy to biochemical energy due to a change in configuration of the rhodopsin molecule as sunlight strikes it, causing the pumping of a
proton
A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...
from inside out and a subsequent inflow that generates the energy.
[''Bacteria with Batteries'', Popular Science, January 2001, Page 55.] The archaeal-like rhodopsins have subsequently been found among different taxa, protists as well as in bacteria and archaea, though they are rare in complex
multicellular organism
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...
s.
Research in 2019 shows these "sun-snatching bacteria" are more widespread than previously thought and could change how oceans are affected by global warming. "The findings break from the traditional interpretation of marine ecology found in textbooks, which states that nearly all sunlight in the ocean is captured by chlorophyll in algae. Instead, rhodopsin-equipped bacteria function like hybrid cars, powered by organic matter when available — as most bacteria are — and by sunlight when nutrients are scarce."
There is an
astrobiological
Astrobiology, and the related field of exobiology, is an interdisciplinary scientific field that studies the origins, early evolution, distribution, and future of life in the universe. Astrobiology is the multidisciplinary field that investig ...
conjecture called the
Purple Earth hypothesis which surmises that original life forms on Earth were retinal-based rather than chlorophyll-based, which would have made the Earth appear purple instead of green.
Marine algae
Algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
is an informal term for a widespread and diverse collection of photosynthetic
eukaryotic
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
organisms which are not necessarily closely related and are thus
polyphyletic
A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of converg ...
. Unlike higher plants, algae lack roots, stems, or leaves.
Algal groups
Marine algae have traditionally been placed in groups such as:
green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
,
red algae
Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...
,
brown algae
Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and po ...
,
diatom
A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...
s,
coccolithophore
Coccolithophores, or coccolithophorids, are single celled organisms which are part of the phytoplankton, the autotrophic (self-feeding) component of the plankton community. They form a group of about 200 species, and belong either to the kingdo ...
s and
dinoflagellate
The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...
s.
Green algae
Green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
live most of their lives as single cells or are filamentous, while others form
colonies
In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the '' metropolitan state'' ...
made up from long chains of cells, or are highly differentiated macroscopic seaweeds. They form an informal group containing about 8,000 recognized species.
Red algae
Modern
red algae
Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...
are mostly
multicellular
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...
with differentiated cells and include many notable
seaweed
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
s.
As
coralline algae
Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of ...
, they play an important role in the ecology of coral reefs. They form a (disputed) phylum containing about 7,000 recognized species.
File:Cyanidium O5A.jpg, Cyanidiophyceae
Cyanidiophyceae is a class of unicellular red algae within subdivision Cyanidiophytina, and contain a single plastid, one to three mitochondria, a nucleus, a vacuole and floridean starch. Most are extremophiles inhabiting acid hot springs. The ...
colony, a class of unicellular red algae
File:Porphyra umbilicalis Helgoland.JPG, The seaweed ''Porphyra umbilicalis
Green laver (), known as ''aonori'' (; ) in Japan, ''sea cabbage'' () or ''hutai'' () in China, and ''parae'' () in Korean, is a type of edible green seaweed, including species from the genera ''Monostroma'' and ''Ulva'' ('' Ulva prolifera'', ' ...
''
Brown algae
Brown algae
Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and po ...
are mostly
multicellular
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...
and include many seaweeds, including
kelp
Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms.
Kelp grows in "underwat ...
. They form a
class
Class or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used differentl ...
containing about 2,000 recognized species.
Diatoms
![Star stick diatom](https://upload.wikimedia.org/wikipedia/commons/5/57/Star_stick_diatom.jpg)
Altogether, about 45 percent of the
primary production
In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through c ...
in the oceans is contributed by
diatoms
A diatom (New Latin, Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group com ...
.
File:Diatoms (248 05) Various diatoms.jpg, Diatom
A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising sev ...
s are one of the most common types of phytoplankton
File:Diatoms through the microscope.jpg, They are a major algae group generating about 20% of world oxygen production.
File:Diatom algae Amphora sp.jpg, Diatoms have glass like cell walls called frustule
A frustule is the hard and porous cell wall or external layer of diatoms. The frustule is composed almost purely of silica, made from silicic acid, and is coated with a layer of organic substance, which was referred to in the early literature on ...
s which are made of silica
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...
.
File:Phytoplankton in the form of a diatom chain.jpg, Diatoms linked in a colonial
Colonial or The Colonial may refer to:
* Colonial, of, relating to, or characteristic of a colony or colony (biology)
Architecture
* American colonial architecture
* French Colonial
* Spanish Colonial architecture
Automobiles
* Colonial (1920 au ...
chain
Coccolithophores
File:Emiliania huxleyi.png, The ubiquitous ''Emiliania huxleyi
''Emiliania huxleyi'' is a species of coccolithophore found in almost all ocean ecosystems from the equator to sub-polar regions, and from nutrient rich upwelling zones to nutrient poor oligotrophic waters. It is one of thousands of different ...
''
File:Cwall99 lg.jpg, ''Emiliania huxleyi'' bloom off south England
Coccolithophore
Coccolithophores, or coccolithophorids, are single celled organisms which are part of the phytoplankton, the autotrophic (self-feeding) component of the plankton community. They form a group of about 200 species, and belong either to the kingdo ...
s are almost exclusively marine and are found in large numbers throughout the
sunlight zone of the
ocean
The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
. They have
calcium carbonate plates (or scales) of uncertain function called ''
coccolith
Coccoliths are individual plates or scales of calcium carbonate formed by coccolithophores (single-celled phytoplankton such as '' Emiliania huxleyi'') and cover the cell surface arranged in the form of a spherical shell, called a ''coccosphere' ...
s'', which are important
microfossils
A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...
. Coccolithophores are of interest to those studying global
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
because as
ocean acidity increases, their coccoliths may become even more important as a
carbon sink
A carbon sink is anything, natural or otherwise, that accumulates and stores some carbon-containing chemical compound for an indefinite period and thereby removes carbon dioxide () from the atmosphere.
Globally, the two most important carbon si ...
.
The most abundant species of coccolithophore, ''
Emiliania huxleyi
''Emiliania huxleyi'' is a species of coccolithophore found in almost all ocean ecosystems from the equator to sub-polar regions, and from nutrient rich upwelling zones to nutrient poor oligotrophic waters. It is one of thousands of different ...
'' is an ubiquitous component of the plankton base in
marine food webs
Compared to terrestrial environments, marine environments have biomass pyramids which are inverted at the base. In particular, the biomass of consumers (copepods, krill, shrimp, forage fish) is larger than the biomass of primary producers. Thi ...
.
Management strategies are being employed to prevent eutrophication-related coccolithophore blooms, as these blooms lead to a decrease in nutrient flow to lower levels of the ocean.
Dinoflagellate
File:CSIRO ScienceImage 7609 SEM dinoflagellate.jpg, Dinoflagellates
File:Karenia brevis.jpg, '' Karenia brevis'' produces red tides highly toxic to humans
File:Algal bloom(akasio) by Noctiluca in Nagasaki.jpg, Red tide
A harmful algal bloom (HAB) (or excessive algae growth) is an algal bloom that causes negative impacts to other organisms by production of natural phycotoxin, algae-produced toxins, mechanical damage to other organisms, or by other means. HABs are ...
Mixotrophic algae
Other groups
File:Diplonema papillatum SEM image.gif, Diplonemid
Diplonemidae is a family of biflagellated unicellular protists that may be among the more diverse and common groups of planktonic organisms in the ocean. Although this family is currently made up of three named genera; '' Diplonema'', ''Rhynchopus ...
s may be abundant in the world oceans
Traditionally the
phylogeny
A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...
of microorganisms, such as the algal groups discussed above, was inferred and their
taxonomy
Taxonomy is the practice and science of categorization or classification.
A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...
established based on studies of
morphology
Morphology, from the Greek and meaning "study of shape", may refer to:
Disciplines
* Morphology (archaeology), study of the shapes or forms of artifacts
* Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...
. However developments in
molecular phylogenetics
Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
have allowed the evolutionary relationship of species to be established by analyzing their
DNA and
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
sequences. Many taxa, including the algal groups discussed above, are in the process of being reclassified or redefined using molecular phylogenetics. Recent developments in
molecular sequencing
In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which suc ...
have allowed for the recovery of
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
s directly from environmental samples and avoiding the need for culturing. This has led for example, to a rapid expansion in knowledge of the abundance and diversity of
marine microorganisms
Marine microorganisms are defined by their habitat as microorganisms living in a marine environment, that is, in the saltwater of a sea or ocean or the brackish water of a coastal estuary. A microorganism (or microbe) is any microscopic livin ...
. Molecular techniques such as genome-resolved
metagenomics
Metagenomics is the study of genetic material recovered directly from environmental or clinical samples by a method called sequencing. The broad field may also be referred to as environmental genomics, ecogenomics, community genomics or microb ...
and
single cell genomics are being used in combination with
high throughput techniques.
Between 2009 and 2013, the
''Tara'' Oceans expedition traversed the world oceans collecting plankton and analysing them with contemporary molecular techniques. They found a huge range of previously unknown photosynthetic and mixotrophic algae. Among their findings were the
diplonemid
Diplonemidae is a family of biflagellated unicellular protists that may be among the more diverse and common groups of planktonic organisms in the ocean. Although this family is currently made up of three named genera; '' Diplonema'', ''Rhynchopus ...
s. These organisms are generally colourless and oblong in shape, typically about 20 µm long and with two flagella.
Evidence from
DNA barcoding
DNA barcoding is a method of species identification using a short section of DNA from a specific gene or genes. The premise of DNA barcoding is that by comparison with a reference library of such DNA sections (also called "sequences"), an indiv ...
suggests diplonemids may be among the most abundant and most species-rich of all marine eukaryote groups.
By size
Algae can be classified by size as ''microalgae'' or ''macroalgae''.
Microalgae
Microalgae are the microscopic types of algae, not visible to the naked eye. They are mostly
unicellular
A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...
species which exist as individuals or in chains or groups, though some are
multicellular
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...
. Microalgae are important components of the
marine protists
Marine protists are defined by their habitat as protists that live in Marine habitat, marine environments, that is, in the saline water, saltwater of seas or oceans or the brackish water of coastal Estuary, estuaries. Life originated as marine ...
, as well as the
marine phytoplankton. They are very
diverse. It has been estimated there are 200,000-800,000 species of which about 50,000 species have been described.
[Starckx, Senne (31 October 2012]
A place in the sun - Algae is the crop of the future, according to researchers in Geel
Flanders Today, Retrieved 8 December 2012 Depending on the species, their sizes range from a few micrometers (µm) to a few hundred micrometers. They are specially adapted to an environment dominated by viscous forces.
File:Zooxanthellae.jpg, Zooxanthellae
Zooxanthellae is a colloquial term for single-celled dinoflagellates that are able to live in symbiosis with diverse marine invertebrates including demosponges, corals, jellyfish, and nudibranchs. Most known zooxanthellae are in the genus ''Sy ...
is a photosynthetic algae that lives inside hosts like coral
Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and sec ...
File:Paramecium bursaria.jpg, A single-celled ciliate
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a ...
with green zoochlorellae
''Zoochlorella'' is a ''nomen rejiciendum'' for a genus of green algae assigned to ''Chlorella''. The term zoochlorella (plural zoochlorellae) is sometimes used to refer to any green algae that lives symbiotically within the body of a freshwater ...
living inside endosymbiotic
An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship.
(The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within ...
ally
File:Euglena mutabilis - 400x - 1 (10388739803) (cropped).jpg, '' Euglena mutabilis'', a photosynthetic flagellate
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word ''flagellate'' also describes a particular construction (or level of organization) characteristic of many prokaryotes and eukaryotes and their ...
Macroalgae
Macroalgae
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
are the larger,
multicellular
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...
and more visible types of algae, commonly called
seaweed
Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...
s. Seaweeds usually grow in shallow coastal waters where they are anchored to the seafloor by a
holdfast. Seaweed that becomes adrift can wash up on beaches.
Kelp
Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera. Despite its appearance, kelp is not a plant - it is a heterokont, a completely unrelated group of organisms.
Kelp grows in "underwat ...
is a large brown seaweed that forms large underwater
forests
A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...
covering about 25% of the world coastlines. They are among the most productive and dynamic ecosystems on Earth.
[Mann, K.H. 1973. Seaweeds: their productivity and strategy for growth. Science 182: 975-981.] Some ''
Sargassum
''Sargassum'' is a genus of brown (class Phaeophyceae) macroalgae ( seaweed) in the order Fucales. Numerous species are distributed throughout the temperate and tropical oceans of the world, where they generally inhabit shallow water and coral ...
'' seaweeds are planktonic (free-floating) and form floating drifts.
Like microalgae, macroalgae (seaweeds) are technically
marine protists
Marine protists are defined by their habitat as protists that live in Marine habitat, marine environments, that is, in the saline water, saltwater of seas or oceans or the brackish water of coastal Estuary, estuaries. Life originated as marine ...
since they are not true plants.
File:Giant Kelp.jpg, Giant kelp
''Macrocystis pyrifera'', commonly known as giant kelp or bladder kelp, is a species of kelp (large brown algae), and one of four species in the genus ''Macrocystis''. Despite its appearance, it is not a plant; it is a heterokont. Giant kelp is ...
is technically a protist since it is not a true plant, yet it is multicellular and can grow to 50 m
File:Sargassum on the beach, Cuba.JPG, ''Sargassum
''Sargassum'' is a genus of brown (class Phaeophyceae) macroalgae ( seaweed) in the order Fucales. Numerous species are distributed throughout the temperate and tropical oceans of the world, where they generally inhabit shallow water and coral ...
'' seaweed is a brown alga with air bladders that help it float
File:Histrio histrio by A. H. Baldwin.jpg, Sargassum fish
The sargassum fish, anglerfish, or frog fish (''Histrio histrio'') is a frogfish of the family (biology), family Antennariidae, Monotypic taxon, the only species in its genus. It lives among ''Sargassum'' seaweed which floats in subtropical ocea ...
are camouflaged to live among drifting ''Sargassum'' seaweed
File:Ventricaria ventricosa.JPG, This unicellular bubble algae lives in tidal zone
The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...
s. It can have a 4 cm diameter.
Evolution of land plants
![Earliest land plants](https://upload.wikimedia.org/wikipedia/commons/1/17/Earliest_land_plants.jpg)
The diagram on the right shows an evolutionary scenario for the conquest of land by streptophytes.
Streptophyte algae include all
green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
, and are the only photosynthetic
eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
s from which the macroscopic land flora evolved ''(red lines)''. That said, throughout the course of evolution, algae from various other lineages have colonized land ''(yellow lines)'' — but also streptophyte algae have continuously and independently made the wet to dry transition (convergence of red and yellow). Throughout history, numerous lineages have become extinct ''(X labels)''. Terrestrial algae of various taxonomic affiliations dwell on rock surfaces and form biological
soil crusts. From the diversity of the
paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
streptophyte algae, however, did an organism whose descendants eventually conquered land on a global scale emerge: a likely branched filamentous — or even
parenchymatous
Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms.
Etymology
The term ''parenchyma'' is New Latin from the word ...
— organism that formed
rhizoidal structures and experienced desiccation from time to time. From this "hypothetical hydro-terrestrial alga", the lineages of
Zygnematophyceae
Zygnematophyceae (or Conjugatophyceae) is a class of green algae in the paraphylum streptophyte algae, also referred to as Charophyta, consisting of more than 4000 described species. It contains five orders: the Spirogloeales, the Serritaeniales ...
and
embryophyte
The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as sist ...
s (land plants) arose.
In its infancy, the trajectory leading to the embryophytes was represented by the — now extinct — earliest land plants.
The earliest land plants probably interacted with beneficial
substrate microbiota that aided them in obtaining nutrients from their substrate. Furthermore, the earliest land plants had to successfully overcome a barrage of terrestrial stressors (including ultraviolet light and photosynthetically active
irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...
, drought, drastic temperature shifts, etc.). They succeeded because they had the right set of traits — a mix of adaptations that were selected for in their hydro-terrestrial algal ancestors, exaptations, and the potential for co-option of a fortuitous set of genes and pathways.
During the course of evolution, some members of the populations of the earliest land plants gained traits that are adaptive in terrestrial environments (such as some form of water conductance,
stomata-like structures, embryos, etc.); eventually, the "hypothetical
last common ancestor
In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The ...
of land plants" emerged. From this ancestor, the extant
bryophyte
The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and mosses. Bryophyta s.s. consists of the mosses only. They are characteristically limited in ...
s and
tracheophyte
Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They a ...
s evolved. While the exact trait repertoire of the hypothetical last common ancestor of land plants is uncertain, it will certainly have entailed properties of
vascular
The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away f ...
and
non-vascular plant
Non-vascular plants are plants without a vascular system consisting of xylem and phloem. Instead, they may possess simpler tissues that have specialized functions for the internal transport of water.
Non-vascular plants include two distantly rel ...
s. What is also certain is that the last common ancestor of land plants had traits of algal ancestry.
Marine plants
![Evolution of seagrasses Pengo 8](https://upload.wikimedia.org/wikipedia/commons/e/e2/Evolution_of_seagrasses_Pengo_8.png)
Back in the
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...
, some phytoplankton evolved into
red
Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...
,
brown
Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing or painting, brown is usually made by combining the colors orange and black. In the RGB color model us ...
and
green algae
The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga as ...
. Green algae then invaded the land and started evolving into the
land plant
The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as sist ...
s we know today. Later, in the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
, some of these land plants returned to the sea as
mangrove
A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
s and
seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...
es.
Plant life can flourish in the brackish waters of
estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...
, where
mangroves
A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in severa ...
or
cordgrass
''Spartina'' is a taxon of plants in the grass family, frequently found in coastal salt marshes. Its species are commonly known as cordgrass or cord-grass, and are native to the coasts of the Atlantic Ocean in western and southern Europe, north ...
or
beach grass might grow.
Flowering plant
Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...
s grow in sandy shallows in the form of
seagrass meadow
A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...
s,
mangrove
A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
s line the coast in tropical and subtropical regions and
salt-tolerant
Halotolerance is the adaptation of living organisms to conditions of high salinity. Halotolerant species tend to live in areas such as hypersaline lakes, coastal dunes, saline deserts, salt marshes, and inland salt seas and springs. Halophiles a ...
plants thrive in regularly inundated
salt marsh
A salt marsh or saltmarsh, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated ...
es. All of these habitats are able to sequester large quantities of carbon and support a
biodiverse
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity'') ...
range of larger and smaller animal life. Marine plants can be found in
intertidal zone
The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...
s and shallow waters, such as
seagrass
Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the orde ...
es like Zostera, eelgrass and turtle grass, ''Thalassia''. These plants have adapted to the high salinity of the ocean environment.
Light is only able to penetrate the top so this is the only part of the sea where plants can grow.
The surface layers are often deficient in biologically active nitrogen compounds. The marine nitrogen cycle consists of complex microbial transformations which include the Nitrogen fixation, fixation of nitrogen, its assimilation, nitrification, anammox and denitrification. Some of these processes take place in deep water so that where there is an upwelling of cold waters, and also near estuaries where land-sourced nutrients are present, plant growth is higher. This means that the most productive areas, rich in plankton and therefore also in fish, are mainly coastal.
Mangroves
Mangroves provide important nursery habitats for marine life, acting as hiding and foraging places for larval and juvenile forms of larger fish and invertebrates. Based on satellite data, the total world area of mangrove forests was estimated in 2010 as .
File:Mangrove-Keti Bundar.jpg, Mangroves
![Zostera marina dis](https://upload.wikimedia.org/wikipedia/commons/2/26/Zostera_marina_dis.png)
* Spalding, M. (2010
''World atlas of mangroves'' Routledge. . .
Seagrasses
Like mangroves, seagrasses provide important nursery habitats for larval and juvenile forms of larger fish and invertebrates. The total world area of seagrass meadows is more difficult to determine than mangrove forests, but was conservatively estimated in 2003 as .
File:Floridian seagrass bed.jpg, Seagrass meadow
File:Leafy Sea Dragon SA.jpg, Leafy sea dragon, Sea dragons camouflaged to look like floating seaweed live in kelp forests and seagrass meadows
Stoichiometry
The stoichiometry (measurement of chemical reactants and Product (chemistry), products) of primary production in the surface ocean plays a crucial role in the Marine biogeochemical cycles, cycling of elements in the global ocean. The ratio between the elements carbon (C), nitrogen (N), and phosphorus (P) in exported organic matter expressed in terms of the C:N:P ratio helps determine how much Atmospheric carbon cycle, atmospheric carbon is Carbon sequestration, sequestered in the deep ocean with respect to the availability of limiting nutrients.
On geologic timescales, the N:P ratio reflects the relative availability of nitrate with respect to phosphate, both of which are externally supplied from the atmosphere via nitrogen fixation and/or continents via river supply and lost by denitrification and burial. On shorter timescales, the average stoichiometry of exported bulk particulate organic matter reflects the elemental stoichiometry of
phytoplankton
Phytoplankton () 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 (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'.
Ph ...
, with additional influences from biological diversity and secondary processing of organic matter by zooplankton and heterotrophic bacteria. In the face of global change, understanding and quantifying the mechanisms that lead to variability in C:N:P ratios are crucial in order to have an accurate projection of future climate change.
A key unresolved question is what determines C:N:P of individual phytoplankton. Phytoplankton grows in the Epipelagic zone, upper light-lit layer of the ocean, where the amount of inorganic nutrients, light, and temperature vary spatially and temporally.
Laboratory studies show that these fluctuations trigger responses at the cellular level, whereby cells modify resource allocation in order to adapt optimally to their ambient environment. For example, phytoplankton may alter resource allocation between the P-rich biosynthetic apparatus, N-rich light-harvesting apparatus, and C-rich energy storage reserves. Under a typical future warming scenario, the global ocean is expected to undergo changes in nutrient availability, temperature, and
irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...
. These changes are likely to have profound effects on the physiology of phytoplankton, and observations show that competitive phytoplankton species can acclimate and adapt to changes in temperature, irradiance, and nutrients on decadal timescales. Numerous laboratory and field experiments have been conducted that study the relationship between the C:N:P ratio of phytoplankton and environmental drivers. It is, however, challenging to synthesize those studies and generalize the response of phytoplankton C:N:P to changes in environmental drivers.
Individual studies employ different sets of statistical analyses to characterize the effects of the environmental driver(s) on elemental ratios, ranging from a simple t test to more complex mixed models, which makes interstudy comparisons challenging. In addition, since environmentally induced trait changes are driven by a combination of Phenotypic plasticity, plasticity (acclimation), adaptation, and life history, stoichiometric responses of phytoplankton can be variable even amongst closely related species.
Meta-analysis/systematic review is a powerful statistical framework for synthesizing and integrating research results obtained from independent studies and for uncovering general trends. The seminal synthesis by Geider and La Roche in 2002, as well as the more recent work by Persson et al. in 2010, has shown that C:P and N:P could vary by up to a factor of 20 between nutrient-replete and nutrient-limited cells. These studies have also shown that the C:N ratio can be modestly plastic due to nutrient limitation. A meta-analysis study by Hillebrand et al. in 2013 highlighted the importance of growth rate in determining elemental stoichiometry and showed that both C:P and N:P ratios decrease with the increasing growth rate. In 2015, Yvon-Durocher et al. investigated the role of temperature in modulating C:N:P. Although their dataset was limited to studies conducted prior to 1996, they have shown a statistically significant relationship between C:P and temperature increase. MacIntyre et al. (2002) and Thrane et al. (2016) have shown that irradiance plays an important role in controlling optimal cellular C:N and N:P ratios. Most recently, Moreno and Martiny (2018) provided a comprehensive summary of how environmental conditions regulate cellular stoichiometry from a physiological perspective.
The elemental stoichiometry of marine phytoplankton plays a critical role in global biogeochemical cycles through its impact on nutrient cycling, secondary production, and carbon export. Although extensive laboratory experiments have been carried out over the years to assess the influence of different environmental drivers on the elemental composition of phytoplankton, a comprehensive quantitative assessment of the processes is still lacking. Here, the responses of P:C and N:C ratios of marine phytoplankton have been synthesized to five major drivers (inorganic phosphorus, inorganic nitrogen, inorganic iron, irradiance, and temperature) by a meta-analysis of experimental data across 366 experiments from 104 journal articles. These results show that the response of these ratios to changes in macronutrients is consistent across all the studies, where the increase in nutrient availability is positively related to changes in P:C and N:C ratios. The results show that eukaryotic phytoplankton are more sensitive to the changes in macronutrients compared to prokaryotes, possibly due to their larger cell size and their abilities to regulate their gene expression patterns quickly. The effect of irradiance was significant and constant across all studies, where an increase in irradiance decreased both P:C and N:C. The P:C ratio decreased significantly with warming, but the response to temperature changes was mixed depending on the culture growth mode and the growth phase at the time of harvest. Along with other oceanographic conditions of the subtropical gyres (e.g., low macronutrient availability), the elevated temperature may explain why P:C is consistently low in subtropical oceans. Iron addition did not systematically change either P:C or N:C.
Evolutionary timeline
See also
*
Algae
Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...
* Aquatic plants
* Biological pump
* Evolutionary history of plants
* Oceanic carbon cycle
* Plant evolution
* Timeline of plant evolution
* Evolution of photosynthesis
References
Further reading
* Paul G. Falkowski, Falkowski, Paul (Ed.) (2013
''Primary Productivity in the Sea''Springer. .
* Falkowski, Paul and John Albert Raven, Raven, John A. (2013
''Aquatic Photosynthesis''Second edition revised, Princeton University Press. .
* Falkowski P and Knoll AH (2011
''Evolution of Primary Producers in the Sea''Academic Press. .
* Kirk, John T. O. (2010
''Light and Photosynthesis in Aquatic Ecosystems''Third edition revised, Cambridge University Press. .
{{aquatic ecosystem topics, expanded=marine
Marine organisms,
Marine biology,
Biological oceanography, *
Evolution-related timelines
Marine botany
Algae
Seagrass
Seaweeds
Branches of botany