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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Marine ecosystem | 3/4 | https://en.wikipedia.org/wiki/Marine_ecosystem | reference | science, encyclopedia | 2026-05-05T07:35:30.386953+00:00 | kb-cron |
Organisms that live freely at the surface, termed neuston, include keystone organisms like the golden seaweed Sargassum that makes up the Sargasso Sea, floating barnacles, marine snails, nudibranchs, and cnidarians. Many ecologically and economically important fish species live as or rely upon neuston. Species at the surface are not distributed uniformly; the ocean's surface harbours unique neustonic communities and ecoregions found at only certain latitudes and only in specific ocean basins. But the surface is also on the front line of climate change and pollution. Life on the ocean's surface connects worlds. From shallow waters to the deep sea, the open ocean to rivers and lakes, numerous terrestrial and marine species depend on the surface ecosystem and the organisms found there. The ocean's surface acts like a skin between the atmosphere above and the water below, and harbours an ecosystem unique to this environment. This sun-drenched habitat can be defined as roughly one metre in depth, as nearly half of UV-B is attenuated within this first meter. Organisms here must contend with wave action and unique chemical and physical properties. The surface is utilised by a wide range of species, from various fish and cetaceans, to species that ride on ocean debris (termed rafters). Most prominently, the surface is home to a unique community of free-living organisms, termed neuston (from the Greek word, υεω, which means both to swim and to float. Floating organisms are also sometimes referred to as pleuston, though neuston is more commonly used). Despite the diversity and importance of the ocean's surface in connecting disparate habitats, and the risks it faces, not a lot is known about neustonic life. A stream of airborne microorganisms circles the planet above weather systems but below commercial air lanes. Some peripatetic microorganisms are swept up from terrestrial dust storms, but most originate from marine microorganisms in sea spray. In 2018, scientists reported that hundreds of millions of viruses and tens of millions of bacteria are deposited daily on every square meter around the planet.
=== Deep sea and sea floor ===
The deep sea contains up to 95% of the space occupied by living organisms. Combined with the sea floor (or benthic zone), these two areas have yet to be fully explored and have their organisms documented.
=== Large marine ecosystems ===
In 1984, National Oceanic and Atmospheric Administration (NOAA) of the United States developed the concept of large marine ecosystems (sometimes abbreviated to LMEs), to identify areas of the oceans for environmental conservation purposes and to enable collaborative ecosystem-based management in transnational areas, in a way consistent with the 1982 UN Convention on the Law of the Sea. This name refers to relatively large regions on the order of 200,000 km2 (77,000 sq mi) or greater, characterized by their distinct bathymetry, hydrography, productivity, and trophically dependent populations. Such LMEs encompass coastal areas from river basins and estuaries to the seaward boundaries of continental shelves and the outer margins of the major ocean current systems. Altogether, there are 66 LMEs, which contribute an estimated $3 trillion annually. This includes being responsible for 90% of global annual marine fishery biomass. LME-based conservation is based on recognition that the world's coastal ocean waters are degraded by unsustainable fishing practices, habitat degradation, eutrophication, toxic pollution, aerosol contamination, and emerging diseases, and that positive actions to mitigate these threats require coordinated actions by governments and civil society to recover depleted fish populations, restore degraded habitats and reduce coastal pollution. Five modules are considered when assessing LMEs: productivity, fish and fisheries, pollution and ecosystem health, socioeconomics, and governance. Periodically assessing the state of each module within a marine LME is encouraged to ensure maintained health of the ecosystem and future benefit to managing governments. The Global Environment Facility (GEF) aids in managing LMEs off the coasts of Africa and Asia by creating resource management agreements between environmental, fisheries, energy and tourism ministers of bordering countries. This means participating countries share knowledge and resources pertaining to local LMEs to promote longevity and recovery of fisheries and other industries dependent upon LMEs.
Large marine ecosystems include:
== Role in 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. 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. The productivity of a marine ecosystem can be measured in several ways. Measurements pertaining to zooplankton biodiversity and species composition, zooplankton biomass, water-column structure, photosynthetically active radiation, transparency, chlorophyll-a, nitrate, and primary production are used to assess changes in LME productivity and potential fisheries yield. Sensors attached to the bottom of ships or deployed on floats can measure these metrics and be used to quantitatively describe changes in productivity alongside physical changes in the water column such as temperature and salinity. This data can be used in conjunction with satellite measurements of chlorophyll and sea surface temperatures to validate measurements and observe trends on greater spatial and temporal scales. Bottom-trawl surveys and pelagic-species acoustic surveys are used to assess changes in fish biodiversity and abundance in LMEs. Fish populations can be surveyed for stock identification, length, stomach content, age-growth relationships, fecundity, coastal pollution and associated pathological conditions, as well as multispecies trophic relationships. Fish trawls can also collect sediment and inform us about ocean-bottom conditions such as anoxia.
== Threats ==