Marine biology
Marine biology is the study of animal and plant life within saltwater ecosystems. 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 deals with those species in which life is spent only (or mainly) in the water, thus its classification is based on the environment rather than on taxonomy.
Overview
Marine biology covers a great deal, from the microscopic plankton (with phytoplankton hugely important as the primary producers of the sea), to the huge cetaceans (or whale).
A large (exactly how large is unknown at this point) proportion of all life on earth is contained in the oceans. Including many species that are economically important to humans, including the food fishes. It is also becoming understood that the well being of marine organisms and non ocean dwelling organisms is linked in some very fundamental ways.
Subfields of marine biology
The Marine ecosystem being so huge, there are quite a number of subfields in marine biology, mostly involving specializations in particular species and biomes, such as reef habitats, tide pool ecology, and geothermal ventricals.
There are also subfields reserved for studying the physical effects of continual immersion in sea water, and the ocean in general, as well as for the ways that various changing oceanic properties affect marine life. Not being our realm, scientists study how various organisms have adapted to this salty environment.
In addition, 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. An interesting branch of marine biology is aquaculture. Marine environments are the home to many exotic biological materials that may inspire biomimetic materials.
Related fields
Marine biology is closely linked to both oceanography and biology. It also encompasses ideas from ecology. Fisheries science can be considered a partial offshoot of marine biology, as can marine conservation.
Lifeforms studied in marine biology
Microscopic life
Plant life
Other sea life
Cnidarias such as Jellyfish and sea anemone, Ctenophoras, sea worms including phylums: Plathyhelminthes, Nemertea, Annelida, Sipuncula, Echiura, and the Phoronidas; Mollusca including shellfish and squid and octopus, Crustaceans, Poriferas including sponges, Bryozoa, Echinoderms including starfish, Urochordata - sea squirts or tunicates.
Fishes
Main article: Fish
Fishes inhabit the largest, (by volume) biome on planet earth and since they exist in a watery environment it means that very different biological functions have evolved. Fish anatomy includes two chamber heart, operculem, secretory cells that produce mucous, swim bladder, scales, fins, gills, lips and eyes. Fish breathe under water by extracting oxygen from sea water through their gills. Fins are used to propel and stabilize them in their watery environment.
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.
Marine mammals
Reefs
Reefs comprise some of the densest bio habitats in the world as far as number of species within a given area. They can be incredibly diverse. Even cold water reefs. Tropical reefs are known best though, and exist in most tropical waters.
Reefs are built up by coral and other calcined deposits, usually on top of a rocky outcrop on the ocean floor. Reefs can evolve on other things too though, which has given rise to the human ability to create artificial reefs.
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 at 10,924 m (35,838 ft). Water pressure at these depths is extreme and there is no light from above, but some life still exists here. Small flounder Soleidae fish and shrimp were seen by the american crew of the Bathyscaphe Trieste when it dived to the bottom in 1960.
Other notable deeps include Monterey Canyon, in the eastern Pacific, the Tonga Trench in the south west at 32,000 feet, the Philippine trench, the Puerto Rico Trench at 8,605 m (28,232 ft), the Romanche Trench at -7,760 m (24,450 ft), Fram Basin in the Arctic at -4,665 m, the Java Trench at 7,450 m (24,442 ft), and the South Sandwich Trench at -7,235 m.
In general the deep sea is considered to start at the photic zone, the point where sunlight looses 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 around seamounts that rise from the deeps. Fish and other sea life use these as congregating areas, for spawning, and feeding.
Hydrothermal vents in the ocean floor act as oasis's for life. As well as their opposites, cold seeps. These places support unique biomes and many new microbes have been discovered at these places.
How oceanic factors affect distribution of various organisms
An active research topic in marine biology, is discovering and mapping the life cycles of various species and where they spend their time. Marine Biologists study how the ocean currents affect ocean life, and the effect of the multitudes of other oceanic factors on their growth and well being. This has only recently become technically feasible with the advances in GPS and newer underwater visual devices.
Most ocean life and fish breed in specific places, nest or not in others, spend their time as juveniles in still others, and in maturity in yet others. Scientists were at a loss for quite a while as to the location of many species during different parts of their life cycles. In fact where sea turtles travel is still largely unknown. Tracking devices just don't work for some life forms, and the rigors of the ocean are not friendly to technology. But these factors are being overcome in many instances.
History of marine biology
In recent times, marine biologists are trying to complete the mapping of underwater species with the help of modern techniques, which could help in exploring the deepest oceanic depressions in which it is supposed that new species could be found, eventually of potential great interest also for the theories on evolution.
Institutions, well-known journals
Many universities teach courses in marine biology.