A mere handful of seafloor mud may contain as many species as are found in a square meter of tropical rainforest. The fantastic assemblage seen above was gathered from a single scoop of mud, about 2 inches deep and 5 inches across.
“It’s easy, when you get away from the coast, to think of the oceans
as a homogeneous blue. It’s a lot more complex than that,” said
biologist Craig McClain of the National Evolutionary Synthesis Center.
McClain and colleagues collected the mud while surveying distributions of seafloor organisms,
the lives of which are shaped by “marine snow” — a slow, steady, shower
of organic particles that drift down from high in the water column.
Like terrestrial snow, the deep-sea-life-sustaining version doesn’t
collect uniformly but gathers in drifts and eddies. In a paper published
last year in Marine Ecology, McClain and others showed that, depending on snowfall, seafloor communities could vary wildly in the space of a few feet. In terrestrial terms, it was a bit like finding deserts and swamps separated by footsteps.
In a December Proceedings of the Royal Society B paper, the researchers again looked at seafloor distributions — but this time, rather than surveying one small seabed plot, they took samples from across the Atlantic Ocean.
They found large-scale, trans-Atlantic patterns, somewhat reminiscent of the vast and elegant patterns seen in blooming plankton, but not measured before on seafloors.
“The oceans are not as uniform as we have a tendency to think of
them,” said McClain. “When you actually look at the ocean, you find that
it’s a mosaic.”
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