Marine biology is the scientific study of the biology of marine life, organisms that inhabit the sea. Given that 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.
A large proportion of all life 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,[ Oceanographic and Bathymetric Features Marine Conservation Institute. Uploaded 18 September 2013.] 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 between the ocean and atmosphere, to the depths of the , sometimes 10,000 meters or more beneath the surface of the ocean.
Specific habitats include estuaries, , , seagrass meadows, the surrounds of and , , muddy, sandy and rocky bottoms, and the open ocean (pelagic) zone, where solid objects are rare and the surface of the water is the only visible boundary. The organisms studied range from microscopic phytoplankton and zooplankton to huge cetaceans (whales) in length. Marine ecosystem 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 and 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, and are involved in the regulation of the Earth's climate.
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) and of air (such as Earth's respiration, and movement of energy through 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 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,
chemistry, and
geology of the
ocean. Biological oceanography mostly focuses on the
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).
Marine habitats
Marine habitats can be divided into
coastal and
open ocean habitats. Coastal habitats are found in the area that extends from the
shoreline to the edge of the 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 and
demersal habitats. Pelagic habitats are found near the surface or in the open
water column, away from the bottom of the ocean and affected by
, 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 engineers which reshape the marine environment to the point where they create further habitat for other organisms.
Intertidal and near shore
, the areas that are close to the shore, are constantly being exposed and covered by the ocean's
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.
Estuaries
Estuaries are also near shore and influenced by the
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
comprise some of the densest and most diverse habitats in the world. The best-known types of reefs are
tropical which exist in most tropical waters; however, reefs can also exist in cold water. Reefs are built up by
and other
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
. Coral reefs also support a huge community of life, including the corals themselves, their symbiotic
zooxanthellae, tropical fish and many other organisms.
Much attention in marine biology is focused on coral reefs and the El Niño 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.[NOAA (1998) Record-breaking coral bleaching occurred in tropics this year. National Oceanic and Atmospheric Administration, Press release (October 23, 1998).][ICRS (1998) Statement on Global Coral Bleaching in 1997-1998. International Coral Reef Society, October 15, 1998.] 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 could exacerbate this trend.[Bryant, D., Burke, L., McManus, J., et al. (1998) "Reefs at risk: a map-based indicator of threats to the world's coral reefs". World Resources Institute, Washington, D.C.][Wilkinson, C. R., and Buddemeier, R. W. (1994) "Global Climate Change and Coral Reefs:Implications for People and Reefs". Report of the UNEP-IOC-ASPEI-IUCN Global Task Team on the Implications of Climate Change on Coral Reefs. IUCN, Gland, Switzerland.]
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,
mesopelagic,
bathypelagic,
abyssopelagic, and
hadopelagic zones. Zones which vary by the amount of light they receive include the
Photic zone and
. Much of the aphotic zone's energy is supplied by the open ocean in the form of
detritus.
Deep sea and trenches
The deepest recorded
oceanic trench measured to date is the
Mariana Trench, near the
Philippines, in the
Pacific Ocean at . At such depths,
water pressure is extreme and there is no sunlight, but some life still exists. A white
flatfish, a shrimp and a jellyfish were seen by the crew of the
bathyscaphe Trieste when it dove to the bottom in 1960, which led to scientific debate surrounding the likelihood of bony fish surviving in such deep waters. General scientific consensus has discredited the possible viewing of a flatfish at such depths.
[Polmar, Norman; Mathers, Lee J. (January 2020). "The First Deepest Dive". U.S. Naval Institute Proceedings. 146/1/1, 403.][ Seven Miles Down: The Story of The Bathyscaph Trieste. , Rolex Deep Sea Special, January 2006.]
In general, the deep sea is considered to start at the aphotic zone, the point where sunlight loses its power of transference through the water.
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 their environment rather than their 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
photosynthesis that occurs in the ocean, as well as the cycling of
carbon,
nitrogen,
phosphorus and other
nutrients and trace elements.
Microscopic life undersea is incredibly diverse and still poorly understood. For example, the role of in marine ecosystems is barely being explored even in the beginning of the 21st century.
The role of phytoplankton is better understood due to their critical position as the most numerous primary producers on Earth. Phytoplankton are categorized into cyanobacteria (also called blue-green algae/bacteria), various types of algae (red, green, brown, and yellow-green), , , Euglenid, , , , , , and .
Zooplankton tend to be somewhat larger, and not all are microscopic. Many Protozoa are zooplankton, including dinoflagellates, , , and . 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 , ctenophores, chaetognatha, , , Tunicate, and such as . Many larger animals begin their life as zooplankton before they become large enough to take their familiar forms. Two examples are 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 occupied by sub plants on land is actually occupied by macroscopic algae in the ocean, such as Sargassum and kelp, which are commonly known as that create .
Plants that survive in the sea are often found in shallow waters, such as the (examples of which are eelgrass, Zostera, and turtle grass, Thalassia). These plants have adapted to the high salinity of the ocean environment. The foreshore is also a good place to find plant life in the sea, where mangroves or cordgrass or beach grass might grow.
Invertebrates
As on land,
invertebrates, or animals that lack a backbone, make up a huge portion of all life in the sea. Invertebrate sea life includes
Cnidaria such as
jellyfish and
; Ctenophora;
including the 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
or
.
Fungi
Over 10,000
species of
fungi are known from marine environments.
These are parasitic on
marine algae or animals, or are
on algae, corals, protozoan cysts, sea grasses, wood and other substrata, and can also be found in
sea foam.
[Kirk, P.M., Cannon, P.F., Minter, D.W. and Stalpers, J. "Dictionary of the Fungi". Edn 10. CABI, 2008] Spores of many species have special appendages which facilitate attachment to the substratum.
A very diverse range of unusual secondary
is produced by marine fungi.
Vertebrates
Fish
A reported 33,400 species of fish, including
bony fish and cartilaginous fish, had been described by 2016,
more than all other vertebrates combined. About 60% of fish species live in saltwater.
Reptiles
which inhabit or frequent the sea include
,
,
, the
marine iguana, and the saltwater crocodile. Most
extant taxon marine reptiles, except for some sea snakes, are
oviparity and need to return to land to lay their eggs. Thus most species, excluding 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 at Food and Agriculture Organization of the United Nations . Accessed 7 August 2007.] Some
extinction marine reptiles, such as
Ichthyosauria, evolved to be
viviparity and had no requirement to return to land.
Birds
Birds adapted to living in the marine environment are often called
. Examples include
albatross,
,
, and
. Although they spend most of their lives in the ocean, species such as
can often be found thousands of miles inland.
Mammals
There are five main types of marine mammals:
(
and
);
such as
;
including seals and the
walrus;
; and the
polar bear. All are air-breathing, meaning that 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
, especially
, that may have uses in medicine or engineering. Marine environments are the home to many exotic biological materials that may inspire
Bionics.
Through constant monitoring of the ocean, there have been discoveries of marine life which could be used to create remedies for certain diseases such as cancer and leukemia. In addition, Ziconotide, an approved drug used to treat pain, was created from a snail which resides in the ocean.
Related fields
Marine biology is a branch of
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 also closely related to this field.
Distribution factors
An active research topic in marine biology is to discover and map the life cycles of various species and where they spend their time. Technologies that aid in this discovery include pop-up satellite archival tags,
, and a variety of other
data loggers. Marine biologists study how the
,
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 GPS and newer underwater visual devices.
Most ocean life breeds in specific places, nests 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 and some in the first year of their life travel. Recent advances in underwater tracking devices are illuminating what we know about marine organisms that live at great ocean depths.
History
The study of marine biology dates to
Aristotle (384–322 BC), who made many observations of life in the sea around
Lesbos, laying the foundation for many future discoveries.
["History of the Study of Marine Biology - MarineBio.org". MarineBio Conservation Society. Web. Monday, March 31, 2014. ] In 1768, Samuel Gottlieb Gmelin (1744–1774) published the
Historia Fucorum, the first work dedicated to marine
algae and the first book on marine biology to use the new binomial nomenclature of
Carl Linnaeus. It included elaborate illustrations of seaweed and marine algae on folded leaves.
[Gmelin S G (1768) Historia Fucorum Ex typographia Academiae scientiarum, St. Petersburg.][Silva PC, Basson PW and Moe RL (1996) Catalogue of the Benthic Marine Algae of the Indian Ocean page 2, University of California Press. .] 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.[Ward, Ritchie R. Into the ocean world; the biology of the sea. 1st ed. New York: Knopf; distributed, 1974: 161] Another important expedition was undertaken by 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.[Gage, John D., and Paul A. Tyler. Deep-sea biology: a natural history of organisms at the deep-sea floor. Cambridge: Cambridge University Press, 1991: 1] 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 Concarneau, France founded by the College of France in 1859.[Maienschein, Jane. 100 years exploring life, 1888-1988: the Marine Biological Laboratory at Woods Hole. Boston: Jones and Bartlett Publishers, 1989: 189-192] The development of technology such as Sonar, scuba diving gear, and remotely operated vehicles allowed marine biologists to discover and explore life in deep oceans that was once thought to not exist.
In 1960, the bathyscaphe Trieste descended the furthest point man had yet traveled, bottoming Challenger Deep at 35,797 feet.
See also
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
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
