Marine ecosystems are found in the oceans. Marine environments are characterized by an average salt concentration of 3%. Oceans cover nearly three fourths of surface df the earth. There is following importance of the marine ecosystem:
- Most of the rainfall on.the earth takes place by evaporation of seawater.
- The ocean temperatures have a major effect on world climate and wind patterns.
- Marine algae supply a large portion of the world’s oxygen. These algae consume huge amounts of atmospheric carbon dioxide.
Th9 marine communities are distributed according to the depth and their distance from shore. There are following zones of oceans:
- Photic zone: The open water of ocean where light can penetrate is called photic zone. Phytoplankton, zoo-. plankton, and many fish species occur in this zone.
- Aphotic zone: The zone below the photic zone where light cannot penetrate is called aphotic zone. The ocean is much deep. Therefore, most of the ocean is without of light. Only a small amount of light is produced by a few luminescent fishes and invertebrates.
- Intertidal zone: The shallow zone where land meets water is called the intertidal zone. It has large number of brown and red algae.
- Neritic zone: The shallow regions over the continental shelves beyond the intertidal zone is called neritic zone.
- Oceanic zone: The zone below the continental shelf reaching very great depths is called oceanic zone.
- Pelagic zone: The open water of any depth is called pelagic zone.
- Benthic zone: The open water at the seafloor is called benthic zone.
Human impacts on oceans
Humans harvest the ocean heavily. They dump waste in it. It highly pollutes the oceans.. Its effects are being studied. The amount of seafood is decreasing The whales, dolphins, and other marine mammals are in danger of extinction. Many coastal areas are polluted.