If the number of species that live on land is not fully known, our knowledge of marine life diversity is much less. Even the scanty information available is not easily accessible. The Census of Marine Life (COML), a decade-long initiative involving 2,700 scientists from 80 countries, the largest-ever collaboration of marine biologists, has partially succeeded in addressing this issue. In a collection of papers published in the open access journal, PLoS One, COML has released an inventory compilation of known and new marine species along with their distribution and diversity pattern in key global ocean areas. The 25 biologically representative regions under study extend from the Antarctic through temperate and tropical seas to the Arctic. The results published do not include highly diverse areas like the Arabian Sea where the inventories continue, and the final findings are expected in October. The average number of known species in the 25 regions is about 11,000. On an average, crustaceans, including crabs, lobsters and shrimp, along with fish and molluscs, make up nearly half of all known species. The compilation challenges the notion that knowledge of diversity can be extrapolated from one location to another. For instance, about half of New Zealand and Antarctic marine species and a quarter of those seen in Australia and South Africa are endemic to those regions. South Korea, China, South Africa and the Baltic have most species relative to their seabed area. Evidently, marine species have not flourished uniformly across the world.

Though 230,000 marine species are known and, at least, 1,200 new species discovered by COML, 70-80 per cent still remain undiscovered. But there is a possibility that many species may be lost even before they are discovered and the diversity of known species affected, with over-fishing, pollution, and habitat loss posing great threats. Of grave concern is that these threats are real in all the 25 regions. Over-fishing occurred across a range of marine species harvested, and the spill-over of over-harvesting has resulted in the depletion of by-catch species abundance. Pollution and other human interventions such as dredging are affecting marine diversity in ways not fully known to us. While the threat from these activities is well known, enclosed seas such as the Mediterranean, Gulf of Mexico, and seas off China are at greater peril than the open seas. The effects of climate change, such as oxygen depletion and acidification, are beginning to affect marine life. The COML predictions of species loss may well come true unless the ecologically disruptive course is corrected.

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