The main characteristics of aquatic ecosystems are:
- Its biotope is covered by water.
- Its environmental conditions, especially that of the oceans, are quite stable.
- Water, although it allows living beings to float, also offers resistance to their displacement.
- Its main conditions are:
- Water currents. Sea currents transport the nutrients necessary for living beings. Most organisms live in the surface areas of the ocean.
- Salinity. Depending on the concentration of salts dissolved in water, there are:
Marine ecosystems (saltwater ecosystems)
The main characteristics of marine ecosystems are:
- The average temperature of the great oceanic masses varies little, from 31 ºC on average in the equatorial zones, to -2 ºC in the polar zones.
- Salinity is usually about 35 grams of salts per liter of water, an amount that remains fairly constant.
- Marine currents, tides and waves condition the life of the marine ecosystem.
- These ecosystems include the oceans, seas, marshes, etc., but can also appear salt water in the interior of the continents, such as the Dead Sea.
Some of the main saltwater ecosystems are:
- Ecosystems on the cliffs. The waves hit the rocks and, together with the sea currents, make the organisms that are adapted to live there have to attach themselves strongly to the rocks, with sticky filaments like mussels or with suckers like limpets.
- Ecosystems on the beaches Live filter feeders, such as clams and other molluscs , which feed by filtering the water. There are also aquatic plants , such as Posidonia.
- Ecosystems in the high seas. It is the largest zone, and animals are usually in the photic zone, the zone illuminated by the sun's rays. There is a lot of diversity of species : whales, dolphins, fish, etc.
- Ecosystems in coral reefs. In shallow areas of tropical regions there may be coral reefs with great biodiversity, with sponges, polyps, fish, crustaceans, molluscs, etc.
- Abyssal Plain Ecosystems. At the bottom of the sea, where sunlight does not reach, the animals have to adapt to total darkness. Some have organs that produce light.