Marine ecosystems make up the largest aquatic system in the world covering more then 70 percent of the planet. Marine ecosystems are considered to be the habitats that complete the larges system from the shores to the dark abandoned sea floor. The marine ecosystem includes: marshes, tidal zones, estuaries, the mangrove forest, lagoons, sea grass beds, the sea floor, and the coral reefs. Just like every other ecosystem in the world, the aquatic ecosystems feed off each other maintaining a balanced marine ecosystem. The marine ecosystems are important to the world, because without them the marine life would not have and protection from predators, which will eventually make the marine life go extinct.
Marine ecosystems importance
Marine Ecosystems are an important part of the world, because the marine ecosystems give marine life such as: tiny plankton, fish, crustaceans, invertebrates, reptiles, marine mammals, sharks, and rays a place to live and survive. It also gives those marine animals a place to hunt. Many marine life have an important role in the world such as the tiny plankton because without them the world would build up with carbon dioxide, the plankton absorbs the carbon dioxide in the air and releases oxygen back into the air. Without marine ecosystems to protect the tiny plankton, more species would become extinct. The most important marine ecosystems for marine life are estuaries and coral reefs. These two marine ecosystems are important because the estuaries are breeding territories for many marine animals, because it is easy for young-lings to survive there, since there are no known predators that live in that region. Coral reefs are important for the marine life, because it provides a shelter for various amount of species. Coral reefs also are the most diverse ecosystem in the whole aquatic system. Without all the marine ecosystems the marine food web and the whole ocean would be in a spiral downward curve.
Marine ecosystem threats
The threats that have impacted the marine ecosystems are pollution and overfishing. Pollution is impacting the marine ecosystems, because as more carbon dioxide is released into the air more of the ice caps are melting. Therefore, the rising of ocean levels and the decrease in salinity levels. Are causing problems for the marine life. If the salinity levels keep dropping the marine life that survive in salt water will not be able to survive in the fresh water rich waters. Pollution is killing marine animals not only in the salinity drop, but also they eat or get trapped in harmful garbage, marine life in the ocean die from swallowing or getting caught on trash everyday. Over one million sea birds are killed by pollution every year. Also three hundred dolphin and porpoise are killed by pollution, by either swallowing trash or getting tangled in trash and one hundred thousand marine mammals are killed by ingesting plastics and other pollution substance every year.  Pollution is a major reason why marine ecosystems are being threatened. But, another threat to marine ecosystems are overfishing. Overfishing is a threat for marine ecosystems because a decrease in number of a species will effect the marine food web disrupting the whole ocean. If overfishing causes a specie to become extinct in the marine ecosystem then it will have one of the species in the ocean to become overpopulated. Once one specie becomes overpopulated then that organism dominates the ocean making other species to become endangered or extinct. The threats in the marine ecosystems can have an impact that the system will never repair itself, which will disrupt the world more then any other ecosystem would. However, the Government stepped in and passed an amendment that decreases overfishing. This amendment helps the ocean to recover the decrease of marine animals. The amendment puts a set limit for the marine species we manage. In 2014, 91 percent of annual limits were nit exceeded and only 9 percent were exceed. There are numinous amount of reason why catch limits are being exceeded such as: miscount of population, by catch in a fishery, and fishing rates are higher than estimated. Scientist track these number to manage overfishing so population does not deplete more. 
Add any other relevant external links in the section.
- How the whales are being disturbed , by NOAA Marine Studies
-  - by NASA Marine Studies
- This page is a study by NOAA about the marine mammals .
- Helps people see the different species in the marine ecosystem , by Oceana, 2015
- Shows the marine animals that are at risk , by EPA, 2015