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Marine biology is the scientific study of the biology of
marine life Marine life, sea life, or ocean life is the plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, thr ...

marine life
, organisms in the
sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.
sea
. Given that in
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
many
phyla
phyla
, families and
genera Genus /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
have some species that live in the sea and others that live on land, marine biology classifies species based on the
environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...
rather than on
taxonomy Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a specific classification scheme. Originally used only about biological ...
. A large proportion of all
life on Earth
life on Earth
lives in the ocean. The exact size of this ''large proportion'' is unknown, since many ocean species are still to be discovered. The ocean is a complex three-dimensional world covering approximately 71% of the Earth's surface. The habitats studied in marine biology include everything from the tiny layers of surface water in which organisms and abiotic items may be trapped in
surface tension Surface tension is the tendency of liquid surfaces at rest to shrink into the minimum surface area possible. Surface tension is what allows objects with a higher density than water such as razor blades and insects (e.g. Gerridae, water strid ...

surface tension
between the ocean and atmosphere, to the depths of the
oceanic trench , while the lithosphere is subducted back into the asthenosphere at trenches Oceanic trenches are prominent long, narrow topography, topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding ocean ...
es, sometimes 10,000 meters or more beneath the surface of the ocean. Specific habitats include
estuaries An estuary is a partially enclosed coastal body of brackish water Brackish water, also sometimes termed brack water, is water occurring in a natural environment having more salinity File:IAPSO Standard Seawater.jpg, upInternational Associatio ...

estuaries
,
coral reef A coral reef is an underwater ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient c ...

coral reef
s,
kelp forest Kelps are large brown algae The 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. Most b ...

kelp forest
s, seagrass meadows, the surrounds of
seamount A seamount is a large geologic landform that rises from the ocean floor but that does not reach to the water's surface (sea level Mean sea level (MSL) (often shortened to sea level) is an mean, average level of the surface of one or more of ...
s and thermal vents,
tidepool Tide pools or rock pools are shallow pools of seawater Seawater, or salt water, is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly co ...

tidepool
s, muddy, sandy and rocky bottoms, and the open ocean (
pelagic The pelagic zone consists of the water column A water column is a concept Concepts are defined as abstract ideas A mental representation (or cognitive representation), in philosophy of mind Philosophy of mind is a branch of philosophy ...
) zone, where solid objects are rare and the surface of the water is the only visible boundary. The organisms studied range from microscopic
phytoplankton Phytoplankton () are the autotrophic An autotroph or primary producer is an organism that produces complex organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compoun ...

phytoplankton
and
zooplankton Zooplankton (; ) are heterotroph A heterotroph (; from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often ro ...

zooplankton
to huge
cetaceans Cetaceans (from la, Cetus (mythology), cetus, lit=whale, from grc, κῆτος, translit=Cetus (mythology), kētos, lit = huge fish, sea monster) are aquatic mammals constituting the infraorder Cetacea (). Key characteristics are their fully aq ...

cetaceans
(whales) in length.
Marine ecology Marine ecosystems are the largest of Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's surface is land consisting of continent A continent is one of several ...
is the study of how marine organisms interact with each other and the environment. Marine life is a vast resource, providing food, medicine, and raw materials, in addition to helping to support
recreation Recreation is an activity of leisure Leisure has often been defined as a quality of experience or as free time. Free time is spent away from , , , , and , as well as necessary activities such as and ing. Leisure as an experience usuall ...

recreation
and
tourism Tourism is travel Travel is the movement of people between distant geographical location In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of th ...

tourism
all over the world. At a fundamental level, marine life helps determine the very nature of our planet. Marine organisms contribute significantly to the
oxygen cycle Oxygen cycle refers to the movement of oxygen through the atmosphere (air), Biosphere (plants and animals) and the Lithosphere (the earth’s crust). The oxygen cycle demonstrates how free oxygen is made available in each of these regions, as wel ...

oxygen cycle
, and are involved in the regulation of the Earth's
climate Climate is the long-term pattern of weather Weather is the state of the atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a la ...

climate
.
Shore A shore or a shoreline is the fringe of land Land is the solid surface of Earth that is not permanently submerged in water. Most but not all land is situated at elevations above sea level (variable over geologic time frames) and consist ...

Shore
lines are in part shaped and protected by marine life, and some marine organisms even help create new land. Many species are economically important to humans, including both finfish and shellfish. It is also becoming understood that the well-being of marine organisms and other organisms are linked in fundamental ways. The human body of knowledge regarding the relationship between life in the sea and important cycles is rapidly growing, with new discoveries being made nearly every day. These cycles include those of matter (such as the
carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere, atmosphere of the Earth. Carbon is the main component of biological compounds as well as ...

carbon cycle
) and of air (such as
Earth's respiration
Earth's respiration
, and movement of energy through
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...

ecosystem
s including the ocean). Large areas beneath the ocean surface still remain effectively unexplored.


Biological oceanography

Marine biology can be contrasted with biological oceanography.
Marine life Marine life, sea life, or ocean life is the plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, thr ...

Marine life
is a field of study both in marine biology and in biological oceanography. Biological oceanography is the study of how organisms affect and are affected by the
physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scie ...

physics
,
chemistry Chemistry is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. T ...

chemistry
, and
geology Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek ...

geology
of the
oceanographic system
oceanographic system
. Biological oceanography mostly focuses on the
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...
s within the ocean; looking at how they are affected by their environment and how that affects larger marine creatures and their ecosystem.Lalli, Carol M., and Timothy R. Parsons. "Introduction." Biological Oceanography: An Introduction. First Edition ed. Tarrytown, New York: Pergamon, 1993. 7-21. Print. Biological oceanography is similar to marine biology, but it studies ocean life from a different perspective. Biological oceanography takes a bottom up approach in terms of the food web, while marine biology studies the ocean from a top down perspective. Biological oceanography mainly focuses on the ecosystem of the ocean with an emphasis on plankton: their diversity (morphology, nutritional sources, motility, and metabolism); their productivity and how that plays a role in the global carbon cycle; and their distribution (predation and life cycle). Biological oceanography also investigates the role of microbes in food webs, and how humans impact the ecosystems in the oceans.


Marine habitats

Marine habitats can be divided into
coastal The coast, also known as the coastline or seashore, is defined as the area where land meets the ocean The ocean (also the sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the worl ...

coastal
and
open ocean The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth, as illustrated on the right. The word "pelagic" is derived . The pelagic zone can be thought of in terms of an imaginary cylinder ...
habitats. Coastal habitats are found in the area that extends from the
shoreline A shore or a shoreline is the fringe of land Land is the solid surface of Earth that is not permanently submerged in water. Most but not all land is situated at elevations above sea level (variable over geologic time frames) and consist ...

shoreline
to the edge of the
continental shelf A continental shelf is a portion of a continent A continent is any of several large landmass A landmass, or land mass, is a large region In geography Geography (from Greek: , ''geographia'', literally "earth descriptio ...

continental shelf
. Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf. Alternatively, marine habitats can be divided into
pelagic The pelagic zone consists of the water column A water column is a concept Concepts are defined as abstract ideas A mental representation (or cognitive representation), in philosophy of mind Philosophy of mind is a branch of philosophy ...
and
demersal The demersal zone is the part of the sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.< ...
habitats. Pelagic habitats are found near the surface or in the open
water column A water column is a concept Concepts are defined as abstract ideas A mental representation (or cognitive representation), in philosophy of mind Philosophy of mind is a branch of philosophy that studies the ontology and nature of the mind ...
, away from the bottom of the ocean and affected by
ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range ...
s, while demersal habitats are near or on the bottom. Marine habitats can be modified by their inhabitants. Some marine organisms, like corals, kelp and sea grasses, are
ecosystem engineer are the prototypical ecosystem engineer because of the effects their dams A dam is a barrier that stops or restricts the flow of surface water, water or underground streams. Reservoirs created by dams not only suppress floods but also prov ...
s which reshape the marine environment to the point where they create further habitat for other organisms.


Intertidal and near shore

Intertidal zone The intertidal zone, also known as the foreshore or seashore, is the area above water level Water level, also known as gauge height or stage, is the elevation of the free surface of a sea, stream, lake or reservoir relative to a specified ve ...
s, the areas that are close to the shore, are constantly being exposed and covered by the ocean's
tides Tides are the rise and fall of sea level Mean sea level (MSL) (often shortened to sea level) is an average In colloquial, ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of t ...

tides
. A huge array of life can be found within this zone. Shore habitats span from the upper intertidal zones to the area where land vegetation takes prominence. It can be underwater anywhere from daily to very infrequently. Many species here are scavengers, living off of sea life that is washed up on the shore. Many land animals also make much use of the shore and intertidal habitats. A subgroup of organisms in this habitat bores and grinds exposed rock through the process of
bioerosion Bioerosion describes the breakdown of hard ocean substrates – and less often terrestrial substrates – by living organisms. Marine bioerosion can be caused by mollusk Mollusca is the second-largest phylum of invertebrate Inve ...
.


Estuaries

Estuaries An estuary is a partially enclosed coastal body of brackish water Brackish water, also sometimes termed brack water, is water occurring in a natural environment having more salinity File:IAPSO Standard Seawater.jpg, upInternational Associatio ...

Estuaries
are also near shore and influenced by the
tides Tides are the rise and fall of sea level Mean sea level (MSL) (often shortened to sea level) is an average In colloquial, ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of t ...

tides
. An estuary is a partially enclosed coastal body of 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 freshwater river environments and saltwater maritime environments. They are subject both to marine influences—such as tides, waves, and the influx of saline water—and to riverine influences—such as flows of fresh water and sediment. The shifting flows of both sea water and fresh water provide high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.


Reefs

Reef A reef is a ridge or shoal A tidal sandbar connecting the islands of Waya and Wayasewa of the Yasawa Islands, Fiji ">Fiji.html" ;"title="Yasawa Islands, Fiji">Yasawa Islands, Fiji In oceanography, geomorphology, and earth sciences, a s ...

Reef
s comprise some of the densest and most diverse habitats in the world. The best-known types of reefs are
tropical The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S; these latitudes correspond to ...

tropical
coral reef A coral reef is an underwater ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient c ...

coral reef
s which exist in most tropical waters; however, reefs can also exist in cold water. Reefs are built up by
coral Corals are marine invertebrates Marine invertebrates are the invertebrates that live in marine habitats. Invertebrate is a blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a ver ...

coral
s and other
calcium Calcium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elem ...

calcium
-depositing animals, usually on top of a rocky outcrop on the ocean floor. Reefs can also grow on other surfaces, which has made it possible to create
artificial reef An artificial reef is a human-created underwater structure, typically built to promote marine life Marine life, sea life, or ocean life is the plant Plants are predominantly photosynthetic Photosynthesis is a process used by p ...
s. Coral reefs also support a huge community of life, including the corals themselves, their symbiotic
zooxanthellae Zooxanthellae is a colloquial term for single-celled dinoflagellate The dinoflagellates (Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a count ...

zooxanthellae
, tropical fish and many other organisms. Much attention in marine biology is focused on coral reefs and the
El Niño es, El Niño, translation=The Boy (; ) is the warm phase of the El Niño–Southern Oscillation El Niño–Southern Oscillation (ENSO) is an irregular periodic variation in winds and sea surface temperatures over the Tropics, tropical easte ...
weather phenomenon. In 1998, coral reefs experienced the most severe mass bleaching events on record, when vast expanses of reefs across the world died because sea surface temperatures rose well above normal. Some reefs are recovering, but scientists say that between 50% and 70% of the world's coral reefs are now endangered and predict that
global warming Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been , but the current changes are more rapid than any known events in Earth's history. The main cau ...

global warming
could exacerbate this trend.


Open ocean

The open ocean is relatively unproductive because of a lack of nutrients, yet because it is so vast, in total it produces the most primary productivity. The open ocean is separated into different zones, and the different zones each have different ecologies. Zones which vary according to their depth include the
epipelagic The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål ...
,
mesopelagic The mesopelagic zone (Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is app ...
,
bathypelagic The bathyal zone or bathypelagic – from Greek βαθύς (bathýs), ''deep'' – (also known as midnight zone) is the part of the open ocean The pelagic zone consists of the water column of the open ocean, and can be further divided into ...
,
abyssopelagic The abyssal zone or abyssopelagic zone is a layer of the pelagic zone The pelagic zone consists of the water column of the open ocean, and can be further divided into regions by depth, as illustrated on the right. The word "pelagic" is derive ...
, and
hadopelagic The hadal zone (named after the realm of Hades, the Greek underworld, underworld in Greek mythology), also known as the hadopelagic zone, is the deepest region of the ocean, lying within oceanic trenches. The hadal zone is found from a depth of a ...
zones. Zones which vary by the amount of light they receive include the
photic The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmå ...
and
aphotic zone The aphotic zone (aphotic from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...
s. Much of the aphotic zone's energy is supplied by the open ocean in the form of
detritus In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms ...

detritus
.


Deep sea and trenches

The deepest recorded
oceanic trench , while the lithosphere is subducted back into the asthenosphere at trenches Oceanic trenches are prominent long, narrow topography, topographic depressions of the ocean floor. They are typically wide and below the level of the surrounding ocean ...
measured to date is the
Mariana Trench The Mariana Trench or Marianas Trench is located in the western Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, de ...
, near the
Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

Philippines
, in the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. ...

Pacific Ocean
at . At such depths,
water pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies ma ...
is extreme and there is no sunlight, but some life still exists. A white
flatfish A flatfish is a member of the ray-finned Actinopterygii (New Latin ('having rays') + Greek ( 'wing, fins')), members of which are known as ray-finned fishes, is a clade (traditionally Class (biology), class or subclass) of the Osteichthyes, ...

flatfish
, a shrimp and a jellyfish were seen by the American crew of the
bathyscaphe A bathyscaphe ( or ) is a free-diving Image:Junko-Kitahama Apnea-Monofin cropped.jpg, Freediver with monofin, ascending Freediving, free-diving, free diving, breath-hold diving, or skin diving is a form of underwater diving that relies on apnea ...
''
Trieste Trieste ( , ; sl, Trst ; german: Triest ) is a city and seaport The Porticciolo del Cedas port in Barcola The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (wher ...

Trieste
'' when it dove to the bottom in 1960. In general, the deep sea is considered to start at the
aphotic zone The aphotic zone (aphotic from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...
, the point where sunlight loses its power of transference through the water. Many life forms that live at these depths have the ability to create their own light known as bio-luminescence. Marine life also flourishes around
seamount A seamount is a large geologic landform that rises from the ocean floor but that does not reach to the water's surface (sea level Mean sea level (MSL) (often shortened to sea level) is an mean, average level of the surface of one or more of ...
s that rise from the depths, where fish and other sea life congregate to spawn and feed.
Hydrothermal vent A hydrothermal vent is a fissure A fissure is a long, narrow crack opening along the surface of the Earth. It is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in the Earth's crust, on ice sheets and glaciers, and ...
s along the
mid-ocean ridge A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics File:Earth cutaway schematic-en.svg, upright=1.35, Diagram of the internal layering of Earth showing the lithosphere above the asthenosphere (not to scale) Plate ...
spreading centers act as
oases In geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population i ...

oases
, as do their opposites,
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 seepa ...
. Such places support unique
biome A biome is a collection of plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respi ...
s and many new
microbe A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms ar ...
s and other lifeforms have been discovered at these locations.


Marine life

In biology many phyla, families and genera have some species that live in the sea and others that live on land. Marine biology classifies species based on the environment rather than on taxonomy. For this reason marine biology encompasses not only organisms that live only in a marine environment, but also other organisms whose lives revolve around the sea.


Microscopic life

As inhabitants of the largest environment on Earth, microbial marine systems drive changes in every global system. Microbes are responsible for virtually all the
photosynthesis Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion (Doctor Who audio), "Conversion" (''Doctor Who'' audio), an episode of the audio drama ' ...

photosynthesis
that occurs in the ocean, as well as the cycling of
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
,
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
,
phosphorus Phosphorus is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical el ...

phosphorus
and other
nutrients A nutrient is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * Matter, anything that has mass and ta ...
and trace elements. Microscopic life undersea is incredibly diverse and still poorly understood. For example, the role of
virus A virus is a submicroscopic infectious agent In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

virus
es in marine ecosystems is barely being explored even in the beginning of the 21st century. The role of
phytoplankton Phytoplankton () are the autotrophic An autotroph or primary producer is an organism that produces complex organic compound , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemical compoun ...

phytoplankton
is better understood due to their critical position as the most numerous
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 Works", 3 ...
on Earth. Phytoplankton are categorized into
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical ...

cyanobacteria
(also called blue-green algae/bacteria), various types of
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
(red, green, brown, and yellow-green),
diatom Diatoms (''diá-tom-os'' 'cut in half', from ''diá'', 'through' or 'apart', and the root of ''tém-n-ō'', 'I cut') are a major group of algae Algae (; singular alga ) is an informal term for a large and diverse group of s. It is a grou ...

diatom
s,
dinoflagellate The dinoflagellates (Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 m ...
s, euglenoids,
coccolithophorid A coccolithophore (or coccolithophorid, from the adjective) is a Unicellular organism, unicellular, eukaryotic phytoplankton (alga). They belong either to the kingdom Protista, according to Robert Whittaker (ecologist), Robert Whittaker's Kingdom ...
s,
cryptomonad The cryptomonads (or cryptophytes) are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterio ...
s, chrysophytes, chlorophytes,
prasinophyte The Prasinophytes (incl. Tetraphytina) or chlorophyta Image:Taiwan 2009 East Coast ShihTiPing Giant Stone Steps Algae FRD 6581.jpg, Green algae on coastal rocks at :zh:石梯坪, Shihtiping in Taiwan Chlorophyta or Prasinophyte, Prasinophyta ...
s, and silicoflagellates.
Zooplankton Zooplankton (; ) are heterotroph A heterotroph (; from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often ro ...

Zooplankton
tend to be somewhat larger, and not all are microscopic. Many
Protozoa Protozoa (singular protozoon or protozoan, plural protozoa or protozoans) is an informal term for a group of Unicellular organism, single-celled eukaryotes, either free-living or Parasitism, parasitic, that feed on organic matter such as other mi ...

Protozoa
are zooplankton, including dinoflagellates, zooflagellates, foraminiferans, and radiolarians. Some of these (such as dinoflagellates) are also phytoplankton; the distinction between plants and animals often breaks down in very small organisms. Other zooplankton include cnidarians, Ctenophora (phylum), ctenophores, chaetognatha, chaetognaths, molluscs, arthropods, Tunicate, urochordates, and annelids such as polychaetes. Many larger animals begin their life as zooplankton before they become large enough to take their familiar forms. Two examples are fish larvae and sea stars (also called starfish).


Plants and algae

Microscopic algae and plants provide important habitats for life, sometimes acting as hiding places for larval forms of larger fish and foraging places for invertebrates. Algal life is widespread and very diverse under the ocean. Microscopic photosynthetic algae contribute a larger proportion of the world's photosynthetic output than all the terrestrial forests combined. Most of the ecological niche, niche occupied by sub plants on land is actually occupied by macroscopic
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
in the ocean, such as ''Sargassum'' and kelp, which are commonly known as seaweeds that create
kelp forest Kelps are large brown algae The 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. Most b ...

kelp forest
s. Plants that survive in the sea are often found in shallow waters, such as the seagrasses (examples of which are eelgrass, ''Zostera'', and turtle grass, ''Thalassia''). These plants have adapted to the high salinity of the ocean environment. The foreshore, intertidal zone is also a good place to find plant life in the sea, where mangroves or cordgrass or Ammophila (Poaceae), beach grass might grow.


Invertebrates

As on land, invertebrates make up a huge portion of all life in the sea. Invertebrate sea life includes Cnidaria such as jellyfish and sea anemones; Ctenophora (phylum), Ctenophora; sea worms including the phylum (biology), phyla Platyhelminthes, Nemertea, Annelida, Sipuncula, Echiura, Chaetognatha, and Phoronida; Mollusca including shellfish, squid, octopus; Arthropoda including Chelicerata and Crustacea; Porifera; Bryozoa; Echinodermata including starfish; and Urochordata including sea squirts or tunicates. Invertebrates have no backbone. There are over a million species.


Fungi

Over 1500 species of fungi are known from marine environments. These are parasitic on marine algae or animals, or are saprobes on algae, corals, protozoan cysts, sea grasses, wood and other substrata, and can also be found in sea foam. Spores of many species have special appendages which facilitate attachment to the substratum. A very diverse range of unusual secondary metabolites is produced by marine fungi.


Vertebrates


Fish

A reported Diversity of fish, 33,400 species of fish, including bony fish, bony and cartilaginous fish, had been described by 2016, more than all other vertebrates combined. About 60% of fish species live in saltwater.


Reptiles

Reptiles which inhabit or frequent the sea include sea turtles, sea snakes, terrapins, the marine iguana, and the saltwater crocodile. Most extant taxon, extant marine reptiles, except for some sea snakes, are oviparity, oviparous and need to return to land to lay their eggs. Thus most species, excepting sea turtles, spend most of their lives on or near land rather than in the ocean. Despite their marine adaptations, most sea snakes prefer shallow waters nearby land, around islands, especially waters that are somewhat sheltered, as well as near estuaries.Stidworthy J. 1974. Snakes of the World. Grosset & Dunlap Inc. 160 pp. .[ftp://ftp.fao.org/docrep/fao/009/y0870e/y0870e65.pdf Sea snakes] a
Food and Agriculture Organization of the United Nations
Accessed 7 August 2007.
Some extinction, extinct marine reptiles, such as ichthyosaurs, evolved to be viviparity, viviparous and had no requirement to return to land.


Birds

Birds adapted to living in the marine environment are often called seabirds. Examples include albatross, penguins, gannets, and auks. Although they spend most of their lives in the ocean, species such as gulls can often be found thousands of miles inland.


Mammals

There are five main types of marine mammals, namely cetaceans (toothed whales and baleen whales); sirenians such as manatees; pinnipeds including seals and the walrus; sea otters; and the polar bear. All are air-breathing, and while some such as the sperm whale can dive for prolonged periods, all must return to the surface to breathe.


Subfields

The marine ecosystem is large, and thus there are many sub-fields of marine biology. Most involve studying specializations of particular animal groups, such as phycology, invertebrate zoology and ichthyology. Other subfields study the physical effects of continual immersion in sea water and the ocean in general, adaptation to a salty environment, and the effects of changing various oceanic properties on marine life. A subfield of marine biology studies the relationships between oceans and ocean life, and global warming and environmental issues (such as carbon dioxide displacement). Recent marine biotechnology has focused largely on marine biomolecules, especially proteins, that may have uses in medicine or engineering. Marine environments are the home to many exotic biological materials that may inspire Bionics, biomimetic materials.


Related fields

Marine biology is a branch of
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
. It is closely linked to oceanography, especially biological oceanography, and may be regarded as a sub-field of marine science. It also encompasses many ideas from ecology. Fisheries science and marine conservation can be considered partial offshoots of marine biology (as well as environmental studies). Marine Chemistry, Physical oceanography and Atmospheric sciences are closely related to this field.


Distribution factors

An active research topic in marine biology is to discover and map the biological life cycle, life cycles of various species and where they spend their time. Technologies that aid in this discovery include pop-up satellite archival tags, acoustic tags, and a variety of other data loggers. Marine biologists study how the
ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range ...
s, tides and many other oceanic factors affect ocean life forms, including their growth, distribution and well-being. This has only recently become technically feasible with advances in Global Positioning System, GPS and newer underwater visual devices. Most ocean life breeds in specific places, nests or not in others, spends time as juveniles in still others, and in maturity in yet others. Scientists know little about where many species spend different parts of their life cycles especially in the infant and juvenile years. For example, it is still largely unknown where juvenile sea turtles and some year-1 sharks travel. Recent advances in underwater tracking devices are illuminating what we know about marine organisms that live at great Ocean depths. The information that pop-up satellite archival tags give aids in certain time of the year fishing closures and development of a marine protected area. This data is important to both scientists and fishermen because they are discovering that by restricting commercial fishing in one small area they can have a large impact in maintaining a healthy fish population in a much larger area.


History

The study of marine biology dates back to Aristotle (384–322 BC), who made Aristotle's biology#Empirical research, many observations of life in the sea around Lesbos, laying the foundation for many future discoveries. In 1768, Samuel Gottlieb Gmelin (1744–1774) published the ''Historia Fucorum'', the first work dedicated to marine
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
and the first book on marine biology to use the new binomial nomenclature of Carl Linnaeus, Linnaeus. It included elaborate illustrations of seaweed and marine algae on folded leaves. The British naturalist Edward Forbes (1815–1854) is generally regarded as the founder of the science of marine biology. The pace of oceanographic and marine biology studies quickly accelerated during the course of the 19th century. The observations made in the first studies of marine biology fueled the age of discovery and exploration that followed. During this time, a vast amount of knowledge was gained about the life that exists in the oceans of the world. Many voyages contributed significantly to this pool of knowledge. Among the most significant were the voyages of where Charles Darwin came up with his theories of evolution and on the formation of coral reefs. Another important expedition was undertaken by HMS Challenger (1858), HMS ''Challenger'', where findings were made of unexpectedly high species diversity among fauna stimulating much theorizing by population ecologists on how such varieties of life could be maintained in what was thought to be such a hostile environment. This era was important for the history of marine biology but naturalists were still limited in their studies because they lacked technology that would allow them to adequately examine species that lived in deep parts of the oceans. The creation of marine laboratories was important because it allowed marine biologists to conduct research and process their specimens from expeditions. The oldest marine laboratory in the world, Station biologique de Roscoff, was established in France in 1872. In the United States, the Scripps Institution of Oceanography dates back to 1903, while the prominent Woods Hole Oceanographic Institute was founded in 1930. The development of technology such as sound navigation ranging, scuba diving gear, submersibles and remotely operated vehicles allowed marine biologists to discover and explore life in deep oceans that was once thought to not exist.


See also

* Acoustic ecology * Aquaculture * Bathymetry * Biological oceanography * Freshwater biology * Modular ocean model * Oceanic basin * Oceanic climate * Phycology * World Ocean Atlas


Lists

* Glossary of ecology * Index of biology articles * Large marine ecosystem * List of ecologists * List of marine biologists * List of marine ecoregions (WWF) * Outline of biology * Outline of ecology


References


Further references

* Morrissey J and Sumich J (2011
''Introduction to the Biology of Marine Life''
Jones & Bartlett Publishers. . * Mladenov, Philip V., Marine Biology: A Very Short Introduction, 2nd edn (Oxford, 2020; online edn, Very Short Introductions online, Feb. 2020), http://dx.doi.org/10.1093/actrade/9780198841715.001.0001, accessed 21 Jun. 2020.


External links


Smithsonian Ocean Portal

Marine Conservation Society
*
Marine Ecology - an evolutionary perspective

Free special issue: Marine Biology in Time and Space

Creatures of the deep ocean
– ''National Geographic'' documentary, 2010.
Exploris


- From the University of Washington Library
Marine Training Portal
- Portal grouping training initiatives in the field of Marine Biology {{DEFAULTSORT:Marine Biology Marine biology, Biological oceanography Fisheries science Oceanographical terminology