Oceans vary in their chemical and physical characteristics. Some of these characteristics include light, pressure, temperature, and nutrients, all of which affect the variety and abundance of species. Generally speaking, the number of species decreases as the distance from the equator increases.
The lack of sediment in the water is a key factor for marine species. The transparency of the water allows light to travel through. Light is used by phytoplankton and many other organisms to make food by the process of photosynthesis.
The number of life forms in much of the oceans is scarce at best. However, some areas do support many different habitats and communities. One of these areas is the Sargasso Sea. Seamounts, some tall enough to reach near the surface, also support many life forms.
Surface Waters
This region (euphotic zone), with its nutrient-rich water, provides a yield of 12.6 million tons a year to fisheries. Producers like phytoplankton, dinoflagellates, and diatoms are the basis in the food chain, since they use light to photosynthesize. Organisms that feed on these producers include anchovetta and sardine. Sea birds like the gull, cormorant, booby, and brown pelican in turn feed on anchovettas and sardines. The largest of the organisms include dolphins, sharks, and toothed whales.
In the Depth
The deepest level of the ocean (below 650 feet) is called the aphotic pelagic zone. Although the environment of this region is relatively stable, food is scarce since the organisms there are entirely dependent on the one level above it for nutrients. Food supplies and the density of organisms generally decrease with depth. However, the diversity of life is relatively high.
Predators tend to have reduced muscle mass and long, thin bodies to conserve energy. They include the hatchetfish, cookiecutter shark, and viper fish. In addition, predators tend to have large heads and jaws and flexible bodies, which allows fish like the Chiasmodon niger and the gulper eel to swallow large fish.
The sea floor is the bottom of the ocean, called the benthic zone. The types of creatures include sessile (permanently attached to a substrate) animals, creeping animals, and burrowing animals. They depend on sinking bits of other decomposing animals to survive.
Other Animals: sea pens, sea lilies, glass sponges, brittle stars, sea cucumbers, Bathyterus or tripod fish, bivalve mollusks.