| Abstract from DBPedia | Marine ecosystems are the largest of Earth's aquatic ecosystems and exist in 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 and 90% of habitable space on Earth. Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides. Other near-shore (neritic) zones can include mudflats, seagrass meadows, mangroves, rocky intertidal systems, salt marshes, coral reefs, lagoons. In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web. Marine ecosystems are characterized by the biological community of organisms that they are associated with and their physical environment. Classes of organisms found in marine ecosystems include brown algae, dinoflagellates, corals, cephalopods, echinoderms, and sharks. Marine ecosystems are important sources of ecosystem services and food and jobs for significant portions of the global population. Human uses of marine ecosystems and pollution in marine ecosystems are significantly threats to the stability of these ecosystems. Environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, climate change, and building on coastal areas. Moreover, much of the carbon dioxide causing global warming and heat captured by global warming are absorbed by the ocean, ocean chemistry is changing through processes like ocean acidification which in turn threatens marine ecosystems. Because of the opportunities in marine ecosystems for humans and the threats created by humans, the international community has prioritized "Life below water" as Sustainable Development Goal 14. The goal is to "Conserve and sustainably use the oceans, seas and marine resources for sustainable development".海洋生態系（かいようせいたいけい）は、地球上で最大の水生生態系であって、塩沼、海岸、河口 、ラグーン、マングローブ、サンゴ礁、深海、底質などの海洋環境と生息する生物をいう。 塩分濃度の低い淡水生態系と対比される。海水面は地球表面の三分の二を覆っている。 一般に海洋生態系は、光合成を行い水中の栄養塩を吸収する植物プランクトンや海藻等の一次生産者を基礎として、一次生産者（死んだ有機物も含む）を直接間接的に捕食する生物、さらに生物間の食物連鎖で構成されている。また、水温や日照、潮流、海底地形、栄養塩濃度、酸素濃度等の海洋環境の影響を受けて、水域毎に海洋生態系を構成する（海洋環境に適応した）生物が異なる。 なお、サンゴ礁を形成する造礁性サンゴは、光合成を行う褐虫藻と共生することにより、暖水かつ低栄養塩の海洋環境に適応した生物であり、そのような海洋環境の海洋生態系の基礎生産を支える重要な生物である。 海洋生態系は、通常、大規模な生物多様性を持っているため、 外来種に対する強い耐性を持っていると考えられている。 (Source: http://dbpedia.org/resource/Marine_ecosystem) |
