Marine biology

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Marine biology is the scientific study of the plants, animals and other organisms that live in the ocean or any other body of water. 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.

There are many practical reasons to study marine biology. Marine life represents 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 produce much of the oxygen we breathe and probably help regulate the earth's climate. Shorelines are in part shaped and protected by marine life, and some marine organisms even help create new land.

Various species of reef fish.

[edit] Overview

Underwater life differs greatly from land life (shown: cuttlefish, which have no close terrestrial relatives).

Marine biology covers a great deal, from the microscopic, including plankton and phytoplankton, which can be as small as 0.02 micrometers and are both hugely important as the primary producers of the sea, to the huge cetaceans (whales) which reach up to a reported 33 meters (109 feet) in length.

The habitats studied by 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 abyssal trenches, sometimes 10,000 meters or more beneath the surface of the ocean. It studies habitats such as coral reefs, kelp forests, tidepools, 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.

A large proportion of all life on Earth exists in the oceans. Exactly how large the proportion is is still unknown. While the oceans comprise about 71% of the Earth's surface, due to their depth they encompass about 300 times the habitable volume of the terrestrial habitats on Earth.

Many species are economically important to humans, including the food fishes. It is also becoming understood that the well-being of marine organisms and other organisms are linked in very fundamental ways. Human understanding is growing of the relationship between life in the sea and important cycles such as that of matter (such as the carbon cycle) and of air (such as Earth's respiration, and movement of energy through ecosystems). Large areas beneath the ocean surface still remain effectively unexplored.

[edit] Subfields

The marine ecosystem is large, and thus there are many subfields of marine biology. Most involve studying specializations of particular species (i.e., phycology, invertebrate zoology, 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 affects of changing various oceanic properties on marine life. A subfield of marine biology studies the relationships between oceans and ocean life, and global weather 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 biomimetic materials.

An interesting branch of marine biology is aquaculture; which some countries do a lot of in the oceans, especially Japan.

[edit] Related fields

Marine biology is closely linked to both oceanography and biology. It also encompasses many ideas from ecology. Fisheries science and marine conservation can be considered partial offshoots of marine biology.

[edit] Lifeforms

[edit] Microscopic life

A copepod.

Microscopic life undersea is incredibly diverse and still poorly understood. For example, the role of viruses 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), diatoms, dinoflagellates, euglenoids, coccolithophorids, cryptomonads, chrysophytes, chlorophytes, prasinophytes, and silicoflagellates.

Zooplankton tend to be somewhat larger, and not all are microscopic. Many Protozoa are zooplankton, including dinoflagellates, zooflagellates, foraminiferans, and radiolarians. Some of these (such as dinoflaggelates) are also phytoplankton; the plant/animal distinction often breaks down in very small organisms. Other zooplankton include cnidarians, ctenophores, chaetognaths, molluscs, arthropods, 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).

[edit] Plants and algae

Giant kelp.

Plant life is relatively rare undersea. Most of the niche occupied by plants on land is actually occupied by macroscopic algae in the ocean, such as Sargassum and kelp which are commonally known as seaweeds. The non algae plants that do survive in the sea are often found in shallow waters, such as the seagrasses (examples of which are eelgrass, Zostera, and turtlegrass, Thalassia). These plants have adapted to the high salinity of the ocean environment. The intertidal zone is also a good place to find plant life in the sea, where mangroves or cordgrass or beach grass might grow.

[edit] Marine invertebrates

A crown-of-thorns starfish.

As on land, invertebrates make up a huge proportion of all life in the sea. Invertrebrate sea life includes Cnidaria such as Jellyfish and sea anemone; Ctenophora; sea worms including phyla: Plathyhelminthes, Nemertea, Annelida, Sipuncula, Echiura, and the Phoronida; Mollusca including shellfish, squid, octopus; Crustaceans; Porifera including sponges, Bryozoa, Echinodermata including starfish; and Urochordata - sea squirts or tunicates.

[edit] Fish

Oceanic whitetip shark.

Main article: Fish

Fish have evolved very different biological functions from other large organisms. Fish anatomy includes a two-chambered heart, operculum, secretory cells that produce mucous, swim bladder, scales, fins, lips and eyes. Fish breathe by extracting oxygen from water through their gills. Fins propel and stabilize the fish in the water.

Well known fish include: sardines, anchovy, tuna, clownfish (also known as anemonefish), and bottom fish which include halibut and ling cod. Predators include sharks and barracuda.

[edit] Reptiles

Sea turtle.

Main article: Marine reptile

Reptiles which inhabit or frequent the sea include sea turtles, marine iguanas, some snakes, and occasionally some crocodiles.

Like almost all amphibians, most reptile species live on or near land, not in the ocean.

[edit] Birds

Chinstrap Penguin.

Many bird species spend much of their time on, in, or near the ocean. Penguins and puffins spend much of their time in sea-water. Seabirds are, generally, birds which feed on things in the ocean. Anseriformes and loons live on water surfaces.

[edit] Marine mammals

A sea otter.

Main article: Marine mammal

There are five main types of marine mammals.

Cetaceans include toothed whales (Suborder Odontoceti), such as the Sperm Whale, dolphins, and porpoises. Cetaceans also include baleen whales (Suborder Mysticeti), such as Gray Whales, Humpback Whales, Dall's porpoise, and Blue Whales.
Sirenians include manatees, the Dugong, and the extinct Steller's Sea Cow.
Seals (Family Phocidae), sea lions (Family Otariidae - which also include the fur seals), and the Walrus (Family Odobenidae) are all considered pinnipeds.
Sea Otters are members of the Family Mustelidae, which includes weasels and badgers.
Finally, Polar Bears (Family Ursidae) are sometimes considered marine mammals because of their dependence on the sea.

[edit] Oceanic Habitats

[edit] Reefs

Main article: Coral reef

Reefs comprise some of the densest and most diverse habitats in the world. The best-known types of reefs are tropical coral reefs which exist in most tropical waters; however, reefs can also exist in cold water. Reefs are built up by corals 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 artificial reefs. Coral reefs also support a huge community of life, including the corals themselves, their symbiotic zooxanthellae, tropical fish and many other organisms.

Corals.

Much attention in marine biology is focused on coral reefs and the El Niño weather phenomenon. In 1998, coral reefs experienced a "once in a thousand years" bleaching event, in which vast expanses of reefs across the Earth died because sea surface temperatures rose well above normal. Some reefs are recovering, but scientists say that 58% of the world's coral reefs are now endangered and predict that global warming could exacerbate this trend.

[edit] Deep sea and trenches

The ocean is deep, very deep in some places. The deepest recorded measure to date is the Mariana Trench, near the Philippines, in the Pacific Ocean at 10924 m (35838 ft). At such depths, water pressure is extreme and there is no sunlight, but some life still exists. Small flounder (family Soleidae) fish and shrimp were seen by the American crew of the bathyscaphe Trieste when it dove to the bottom in 1960.

Other notable oceanic trenches include Monterey Canyon, in the eastern Pacific, the Tonga Trench in the southwest at 10,882 m (35,702 feet), the Philippine Trench, the Puerto Rico Trench at 8605 m (28232 ft), the Romanche Trench at 7760 m (24450 ft), Fram Basin in the Arctic Ocean at 4665 m (15305 ft), the Java Trench at 7450 m (24442 ft), and the South Sandwich Trench at 7235 m (23737 ft).

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. Many life forms that live at these depths have the ability to create their own light.

Much life centers on seamounts that rise from the deeps, where fish and other sea life congregate to spawn and feed. Hydrothermal vents along the mid-ocean ridge spreading centers act as oases, ass do their opposites, cold seeps. Such places support unique biomes and many new microbes and other lifeforms have been discovered at these locations.

[edit] Open ocean

The great expanse of open ocean habitat is huge, and many species can be found passing through it and living in it. The term "open ocean" usually is meant to refer to the vast stretches of water between points of land, or between undersea mounts. Contrary to popular notions the open ocean is often not the place where marine animals spend the majority of their lives. Most species simply pass through the open ocean on their ways to other places. Larger species are the main ongoing inhabitants.

[edit] Intertidals and shore

Intertidal zones, those areas close to shore, are constantly being exposed and covered by the ocean's tides. A huge array of life lives within this zone.

Shore habitats span from the upper intertidal zones to the area where land vegetation takes prominence. It can be underwater anwhere 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.

[edit] How oceanic factors affect distribution of various organisms

An active research topic in marine biology is to discover and map the life cycles of various species and where they spend their time. Marine biologists study how the ocean currents, tides and many other oceanic factors affect ocean lifeforms, 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 or not in others, spends time as juveniles in still others, and in maturity in yet others. Scientists know little about where many species spent different parts of their life cycles. For example, it is still largely unknown where sea turtles travel. Tracking devices do not work for some life forms, and the ocean is not friendly to technology. But these factors are being overcome in many instances.

[edit] Famous marine biologists

Jacques-Yves Cousteau, co-inventer of the aqua-lung, is well known for popularizing marine biology.

Ali Abdelghany (1944- ) Egyptian marine biologist
Jakob Johan Adolf Appellöf (1857-1921), Swedish marine zoologist.
Joseph Ayers, marine neurophysiologist and biomimetic researcher.
Samuel Stillman Berry (1887-1984), U.S. marine zoologist.
Henry Bryant Bigelow (1879 – 1967), U.S. marine biologist.
Rachel Carson (1907-1964) American Marine Biologist and Author.
Ilham Artüz (1924-1993) Turkish Marine Biologist and Oceanographer
Carl Chun (1852-1914), German marine biologist
Jacques-Yves Cousteau (1910-1997), French marine biologist and explorer.
Anton Dohrn (1840-1909), German marine biologist.
Sylvia Earle (born 1935), American oceanographer.
Hans Hass (born 1919), Austrian marine biologist and diving pioneer
Gotthilf Hempel (born 1929), German marine biologist
Johan Hjort, Norwegian marine zoologist and one of the founders of ICES.
Bruno Hofer (1861-1916), German fisheries scientist.
Hirohito (1901-1989), Japanese emperor and jellyfish taxonomist
Uwe Kils (born 1951), German marine biologist
August David Krohn (1803 – 1891), Russian/German zoologist.
William Elford Leach (1790-1836), English zoologist and marine biologist.
Philip S. Lobel Professor, Boston University Marine Program
Nicholai Miklukho-Maklai (1846-1888), Russian marine biologist and anthropologist.
Sir John Murray (1841-1914), Scots-Canadian marine biologist.
Harald Rosenthal (born 1937), German hydrobiologist known for his work in fish farming and ecology.
Michael Sars (1809 – 1869), Norwegian theologian and biologist.
Georg Sars (1837-1927), Norwegian marine biologist.
Ruth Turner (1915-2000), marine biologist.
Robert Paine Professor, emeritus University of Washington intertidal Ecologist
Charles Wyville Thompson (1832-1882), Scottish marine biologist