Representing the most comprehensive and authoritative answer yet to one of humanity's most ancient questions -- "what lives in the sea?" -- Census of Marine Life scientists today released an inventory of species distribution and diversity in key global ocean areas.
Scientists combined information collected over centuries with data obtained during the decade-long Census to create a roll call of species in 25 biologically representative regions -- from the Antarctic through temperate and tropical seas to the Arctic.
Scientists find that the number of known, named species contained in the 25 areas ranged from 2,600 to 33,000 and averaged about 10,750, which fall into a dozen groups. On average, about one-fifth of all species were crustaceans which, with mollusks and fish, make up half of all known species on average across the regions.
The full breakdown follows:
•19% Crustaceans (including crabs, lobsters, crayfish, shrimp, krill and barnacles),
•17% Mollusca (including squid, octopus, clams, snails and slugs)
•12% Pisces (fish, including sharks)
•10% Protozoa (unicellular micro-organisms)
•10% algae and other plant-like organisms
•7% Annelida (segmented worms)
•5% Cnidaria (including sea anemones, corals and jellyfish)
•3% Platyhelminthes (including flatworms)
•3% Echinodermata (including starfish, brittle stars, sea urchins, sand dollars and sea cucumbers)
•3% Porifera (including sponges)
•2% Bryozoa (mat or 'moss animals')
•1% Tunicata (including sea squirts)
The rest are other invertebrates (5%) and other vertebrates (2%). The scarce 2% of species in the "other vertebrates" category includes whales, sea lions, seals, sea birds, turtles and walruses. Thus some of the best-known marine animals comprise a tiny part of marine biodiversity.
How much is unknown?
In October, the Census will release its latest estimate of all marine species known to science, including those still to be added to WoRMS and OBIS. This is likely to exceed 230,000.
Greatest threats
According to the Census studies published in PLoS ONE, the main threats to marine life to date have been overfishing, lost habitat, invasive species and pollution, although the relative importance of the threats varied among regions. Emerging threats include rising water temperature and acidification, and the enlargement of areas characterized by low oxygen content (called hypoxia) of seawater. These too will vary regionally (surface temperature, for example) whereas others are more global (such as acidification).
Overfishing not only depletes the exploited fish themselves but also depletes other species like turtles, albatrosses, sharks and mammals, caught unintentionally. It alters food webs within ecosystems.
Coastal urbanization, sediment runoff and nutrients in sewage and fertilizer washed from the land and causing eutrophication and hypoxia are destroying marine habitats.
The more enclosed seas -- Mediterranean, Gulf of Mexico, China's shelves, Baltic, and Caribbean -- were reported to have the most threatened biodiversity.
Source: www.sciencedaily.com
Scientists combined information collected over centuries with data obtained during the decade-long Census to create a roll call of species in 25 biologically representative regions -- from the Antarctic through temperate and tropical seas to the Arctic.
Scientists find that the number of known, named species contained in the 25 areas ranged from 2,600 to 33,000 and averaged about 10,750, which fall into a dozen groups. On average, about one-fifth of all species were crustaceans which, with mollusks and fish, make up half of all known species on average across the regions.
The full breakdown follows:
•19% Crustaceans (including crabs, lobsters, crayfish, shrimp, krill and barnacles),
•17% Mollusca (including squid, octopus, clams, snails and slugs)
•12% Pisces (fish, including sharks)
•10% Protozoa (unicellular micro-organisms)
•10% algae and other plant-like organisms
•7% Annelida (segmented worms)
•5% Cnidaria (including sea anemones, corals and jellyfish)
•3% Platyhelminthes (including flatworms)
•3% Echinodermata (including starfish, brittle stars, sea urchins, sand dollars and sea cucumbers)
•3% Porifera (including sponges)
•2% Bryozoa (mat or 'moss animals')
•1% Tunicata (including sea squirts)
The rest are other invertebrates (5%) and other vertebrates (2%). The scarce 2% of species in the "other vertebrates" category includes whales, sea lions, seals, sea birds, turtles and walruses. Thus some of the best-known marine animals comprise a tiny part of marine biodiversity.
How much is unknown?
In October, the Census will release its latest estimate of all marine species known to science, including those still to be added to WoRMS and OBIS. This is likely to exceed 230,000.
Greatest threats
According to the Census studies published in PLoS ONE, the main threats to marine life to date have been overfishing, lost habitat, invasive species and pollution, although the relative importance of the threats varied among regions. Emerging threats include rising water temperature and acidification, and the enlargement of areas characterized by low oxygen content (called hypoxia) of seawater. These too will vary regionally (surface temperature, for example) whereas others are more global (such as acidification).
Overfishing not only depletes the exploited fish themselves but also depletes other species like turtles, albatrosses, sharks and mammals, caught unintentionally. It alters food webs within ecosystems.
Coastal urbanization, sediment runoff and nutrients in sewage and fertilizer washed from the land and causing eutrophication and hypoxia are destroying marine habitats.
The more enclosed seas -- Mediterranean, Gulf of Mexico, China's shelves, Baltic, and Caribbean -- were reported to have the most threatened biodiversity.
Source: www.sciencedaily.com
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