Marine Regions

Marine regions cover three-fourths of the earth's surface and its algae provides much of the oxygen supply to this world.  The evaporation of the seawater provides rainwater for the land.

Oceans
This is the largest ecosystem in the world.  Much like ponds and lakes, the ocean is separated into zones; intertidal, pelagic, abyssal, and benthic.  The intertidal zone is where the water meets the land, whether it is submerged or exposed when waves or tides come in and out.  On rocky coast, this zone is vertical and only where highest of tides reach, there are algae and mollusks.  Further submerged in this zone there are a more diverse array of algae and small animals, for instance, herbivorous snails, crabs, sea stars, and small fish.

The pelagic is the zone that is further from the land, so basically the open ocean. This zone is generally cold, even though it is hard to get a temperature range it on because there is a thermal stratification with constant mixing of warm and cold tides.  This zone's flora species is surface seaweeds and the fauna include many species of fish and mammals.  For instance, clown fish, dolphins, and whales.  Many of these species feed on the plankton.

The benthic zone is directly below the pelagic zone, however this zone is not the deepest of the zones.  The benthic zone consist of sand, slit. or dead organism.  The temperature decreases the farther down the zone goes because light has trouble penetrating into deeper waters.  Flora is mainly represented by seaweed while the fauna includes a vast variety of bacteria, fungi, sponges, sea anemones, worms, sea stars, and fishes.

The abyssal is the deepest of all the zones.  The water in this region tends to stay around 3 degrees Celsius, has a high pressure, high in oxygen, but it usually is low in nutrients.  This zone is home to many invertebrates and fishes.

Coral Reefs
Coral reefs tend to be distributed along warm, shallow waters and can be found as barriers along continents, fringing islands, and atolls.  Naturally, the dominant organism is corals.  Reefs are usually lacking in nutrients, so corals obtain their nutrients from algae through photosynthesis or they reach out for plankton. 

Estuaries
This is an area where freshwater rivers or streams merge into an ocean.  The ecosystem is very different from most because there is a mixing of different types of water.  The fauna included in this ecosystem are algae, seaweed, marsh grass, and mangrove trees.  There is also a diverse fauna within here.  Such as, worms, oysters, and crabs.