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Marine protists are defined by their habitat as protists that live in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. Life originated as marine single-celled prokaryotes (bacteria and archaea) and later evolved into more complex eukaryotes. Eukaryotes are the more developed life forms ...
Plankton (from Greek for wanderers) are a diverse group of organisms that live in the water column of large bodies of water but cannot swim against a current. As a result, they wander or drift with the currents. [153] Plankton are defined by their ecological niche, not by any phylogenetic or taxonomic classification.
Marine life, sea life or ocean life is the collective ecological communities that encompass all aquatic animals, plants, algae, fungi, protists, single-celled microorganisms and associated viruses living in the saline water of marine habitats, either the sea water of marginal seas and oceans, or the brackish water of coastal wetlands, lagoons ...
Life histories connect disparate ecosystems; species that live at the surface during one life history stage may occupy the deep sea, benthos, reefs, or freshwater ecosystems during another. A diversity of fish species utilize the ocean's surface, [ 119 ] either as adults or as nursery habitat for eggs and young.
Bacteria inhabit soil, water, acidic hot springs, radioactive waste, [61] and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Once regarded as plants constituting the class Schizomycetes, bacteria are now classified as prokaryotes.
The health of an aquatic ecosystem is degraded when the ecosystem's ability to absorb a stress has been exceeded. A stress on an aquatic ecosystem can be a result of physical, chemical or biological alterations to the environment. Physical alterations include changes in water temperature, water flow and light availability.
Deep ocean water contains the largest reservoir of nitrogen available to hydrothermal vents, with around 0.59 mM of dissolved nitrogen gas. [24] [25] Ammonium is the dominant species of dissolved inorganic nitrogen, and can be produced by water mass mixing below hydrothermal vents and discharged in vent fluids. [25]
Some protists accomplish this using contractile vacuoles, while freshwater fish excrete excess water via the kidney. [4] Although most aquatic organisms have a limited ability to regulate their osmotic balance and therefore can only live within a narrow range of salinity, diadromous fish have the ability to migrate between fresh and saline ...