One Ocean, Many Worlds of Life - Convention on Biological Diversity

Looking closely at bubble anemones, delicate s<strong>of</strong>t pink deep-sea octocorals at 1500 metres depth,
brain corals and jellyfish, one can only be amazed by the incredible shapes and colours.
flickr/silkebaron NOAA/Aquapix
In 2011, a team <strong>of</strong> scientists looked at all the known species on Earth, and
the different categories into which they are grouped, and extrapolated an
estimate <strong>of</strong> approximately 8.7 million species on Earth, 2.2 million <strong>of</strong> which
live in the ocean. This would mean, they said, that 91 percent <strong>of</strong> all marine
species have yet to be discovered—and that’s after the huge effort put forth
by the Census <strong>of</strong> Marine <strong>Life</strong>. In fact, they say, finding and describing future
species is likely only to become harder, as our current inventory is filled with
species that have large geographical ranges, are abundant, or are large and
easy to see. Increasingly, if we want to find new species, we’re going to have
to look for “hotspots” <strong>of</strong> species in hard-to-reach places like the deep sea.10
Even if we assume that those scientists are correct and that there are more
than two million species in the ocean, that still is only part <strong>of</strong> the story.
Because when they say two million species, those researchers are referring
to species as most <strong>of</strong> us generally think <strong>of</strong> them: plants and animals, for
example. But such multicellular life forms comprise only a small fraction <strong>of</strong>
the life in the ocean, both in terms <strong>of</strong> variety and abundance.
Imagine you could weigh all the life in the ocean and rank all the different
types <strong>of</strong> life according to which weighed the most. You would probably
expect that, added together, all the whales in the ocean might weigh the
most, even though there are far fewer <strong>of</strong> them than there used to be, simply
because whales are so massive. Or maybe fish would collectively be the
heaviest grouping, because some <strong>of</strong> them—whale sharks, for example—are
also pretty big and because there are so many fish in the sea.
If you did think that, you’d be wrong. When measured by weight, more than
90 percent <strong>of</strong> ocean life are microbes: invisible or virtually invisible to the
naked human eye. Added together, all the microbes in the sea weigh more
14 Marine BiOdiversity