Marine ecosystem

Marine ecosystems are the largest of Earth's aquatic ecosystems and are distinguished by waters that have a high salt content. These systems contrast with freshwater ecosystems, which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply[1][2] and 90% of habitable space on Earth.[3] Marine ecosystems include nearshore systems, such as the salt marshes, mudflats, seagrass meadows, mangroves, rocky intertidal systems and coral reefs. They also extend outwards from the coast to include offshore systems, such as the surface ocean, pelagic ocean waters, the deep sea, oceanic hydrothermal vents, and the sea floor. Marine ecosystems are characterized by the biological community of organisms that they are associated with and their physical environment.

Ecosystem services

In addition to providing many benefits to the natural world, marine ecosystems also provide social, economic, and biological ecosystem services to humans. Pelagic marine systems regulate the global climate, contribute to the water cycle, maintain biodiversity, provide food and energy resources, and create opportunities for recreation and tourism.[17] Economically, marine systems support billions of dollars worth of capture fisheries, aquaculture, offshore oil and gas, and trade and shipping.

Ecosystem services fall into multiple categories, including supporting services, provisioning services, regulating services, and cultural services.[18]

Threats to marine ecosystems

Although marine ecosystems provide essential ecosystem services, these systems face various threats.[19]

Human exploitation and development

Coastal marine ecosystems experience growing population pressures with nearly 40% of people in the world living within 100 km of the coast.[20] Humans often aggregate near coastal habitats to take advantage of ecosystem services. For example, coastal capture fisheries from mangroves and coral reef habitats are estimated to be worth a minimum of $34 billion per year.[20] Yet, many of these habitats are either marginally protected or not protected. Mangrove area has declined worldwide by more than one-third since 1950,[21] and 60% of the world's coral reefs are now immediately or directly threatened.[22][23] Human development, aquaculture, and industrialization often lead to the destruction, replacement, or degradation of coastal habitats.[20]

Moving offshore, pelagic marine systems are directly threatened by overfishing.[24] Global fisheries landings peaked in the late 1980s, but are now declining, despite increasing fishing effort.[17] Fish biomass and average trophic level of fisheries landing are decreasing, leading to declines in marine biodiversity. In particular, local extinctions have led to declines in large, long-lived, slow-growing species, and those that have narrow geographic ranges.[17] Biodiversity declines can lead to associated declines in ecosystem services. A long-term study reports the decline of 74–92% of catch per unit effort of sharks in Australian coastline from 1960s to 2010s.[25]


Invasive species

  • Global aquarium trade
  • Ballast water transport
  • Aquaculture

Climate change

  • Warming temperatures
  • Increased frequency/intensity of storms
  • Ocean acidification
  • Sea level rise

See also


  1. "Oceanic Institute". Retrieved 2018-12-01.
  2. "Ocean Habitats and Information". 2017-01-05. Retrieved 2018-12-01.
  3. "Facts and figures on marine biodiversity | United Nations Educational, Scientific and Cultural Organization". Retrieved 2018-12-01.
  4. "What is a Salt Marsh?" (PDF). New Hampshire Department of Environmental Services. 2004.
  5. US Department of Commerce, National Oceanic and Atmospheric Administration. "What is a salt marsh?". Retrieved 2019-03-20.
  6. US Department of Commerce, National Oceanic and Atmospheric Administration. "What is a mangrove forest?". Retrieved 2019-03-21.
  7. "Mangroves". Smithsonian Ocean. Retrieved 2019-03-21.
  8. US Department of Commerce, National Oceanic and Atmospheric Administration. "What is the intertidal zone?". Retrieved 2019-03-21.
  9. US Department of Commerce, National Oceanic and Atmospheric Administration. "What is an estuary?". Retrieved 2019-03-22.
  10. US Department of Commerce, National Oceanic and Atmospheric Administration. "Estuaries, NOS Education Offering". Retrieved 2019-03-22.
  11. "Estuaries". 2013-11-14. Retrieved 2019-03-24.
  12. US Department of Commerce, National Oceanic and Atmospheric Administration. "What is a lagoon?". Retrieved 2019-03-24.
  13. Miththapala, Sriyanie (2013). "Lagoons and Estuaries" (PDF). IUCN, International Union for Conservation of Nature.
  14. "Corals and Coral Reefs". Ocean Portal | Smithsonian. 2012-09-12. Retrieved 2018-03-27.
  15. "The Deep Sea". Ocean Portal | Smithsonian. 2012-07-24. Retrieved 2018-03-27.
  16. "The Benthic Zone". Ecosystems. Retrieved 2018-03-27.
  17. "Millenium Ecosystem Assessment, Marine Systems" (PDF).
  18. "Ecosystem Services | Mapping Ocean Wealth". Retrieved 2018-03-27.
  19. "Status of and Threat to Coral Reefs | International Coral Reef Initiative". Retrieved 2018-12-01.
  20. "Millennium Ecosystem Asessment, Coastal Systems" (PDF).
  21. Alongi, Daniel M. (September 2002). "Present state and future of the world's mangrove forests". Environmental Conservation. 29 (3): 331–349. doi:10.1017/S0376892902000231. ISSN 1469-4387.
  22. "Coral Reefs". Ocean Health Index. Retrieved 2018-12-01.
  23. "Reefs at Risk Revisited | World Resources Institute". Retrieved 2018-12-01.
  24. Coll, Marta; Libralato, Simone; Tudela, Sergi; Palomera, Isabel; Pranovi, Fabio (2008-12-10). "Ecosystem Overfishing in the Ocean". PLoS ONE. 3 (12): e3881. doi:10.1371/journal.pone.0003881. ISSN 1932-6203. PMC 2587707. PMID 19066624.
  25. Mumby, Peter J.; Mark A. Priest; Brown, Christopher J.; Roff, George (2018-12-13). "Decline of coastal apex shark populations over the past half century". Communications Biology. 1 (1): 223. doi:10.1038/s42003-018-0233-1. ISSN 2399-3642. PMC 6292889.
  26. EPA,OW, US (2017-01-30). "Threats to Coral Reefs | US EPA". US EPA.

Further reading

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