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An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. [1]
There are also reptilian animals that are highly evolved for life in water, although most extant aquatic reptiles, including crocodilians, turtles, water snakes and the marine iguana, are technically semi-aquatic rather than fully aquatic, and most of them only inhabit freshwater ecosystems.
Semiaquatic animals include: Vertebrates. Amphibious fish; also several types of normally fully aquatic fish such as the grunion and plainfin midshipman that spawn in the intertidal zone; Some amphibians such as newts and salamanders, and some frogs such as fire-bellied toads and wood frogs.
Phosphorus has a different role in aquatic ecosystems as it is a limiting factor in the growth of phytoplankton because of generally low concentrations in the water. [13] Dissolved phosphorus is also crucial to all living things, is often very limiting to primary productivity in freshwater, and has its own distinctive ecosystem cycling. [17]
Estuaries are extremely productive ecosystems that many humans and animal species rely on for various activities. [21] This can be seen as, of the 32 largest cities in the world, 22 are located on estuaries as they provide many environmental and economic benefits such as crucial habitat for many species, and being economic hubs for many coastal ...
Marine mammals are mammals that rely on marine (saltwater) ecosystems for their existence. They include animals such as cetaceans (whales, dolphins and porpoises), pinnipeds (seals, sea lions and walruses), sirenians (manatees and dugongs), sea otters and polar bears. They are an informal group, unified only by their reliance on marine ...
They include animals such as sea lions, whales, dugongs, sea otters and polar bears. Like other aquatic mammals, they do not represent a biological grouping. [26] The humpback whale is a fully aquatic marine mammal. Marine mammal adaptation to an aquatic lifestyle vary considerably between species.
Marine invertebrates are animals that inhabit a marine environment apart from the vertebrate members of the chordate phylum; invertebrates lack a vertebral column. Some have evolved a shell or a hard exoskeleton. The earliest animals may belong to the genus Dickinsonia, [2] 571 million to 539 million years ago. [3]