When many people hear the word "biodiversity," they immediately think of tropical rainforests, or coral reefs; but as this picture demonstrates, biodiversity is a concept that ought to be more closely associated with the ocean floor, as well.
Incredibly, the species you see gathered in the image up top were were collected in a single, handful-sized scoop of seafloor mud. But here's what's really mind blowing: move a few feet in any direction from the site these organisms were collected, and the mud sample you gather is liable to turn up a very different set of creatures.
According to Craig McClain — Assistant Director of Science for the National Evolutionary Synthesis Center and chief editor for Deep Sea News — up until the 1960s, the ocean floor was widely regarded as something of a uniform "wasteland" when it came to organismal diversity. Over the last few decades, however, scientists have come to realize that this assumption could not be further from the truth.
But the ocean floor seems like an awfully harsh environment. How do these creatures manage to survive, let alone speciate? According to McClain, the answer to both of these questions is closely tied to something called "marine snow":
The lack of light in the deep oceans precludes photosynthesis. Thus, primary production of carbon, the base of a food web, is virtually absent. Deep-sea organisms are reliant upon a trickle of falling material from the productive shallow oceans overhead. This material is largely a low quality and low quantity mixture of decaying bodies and feces degraded further by bacteria on its decent into the deep. Roughly 2-5% of the total carbon on the ocean's surface falls to the deep seafloor, the equivalent of roughly 2-3 tablespoons from a 5-pound bag of sugar. This sinking material, marine snow, falls as a dusting on the ocean bottom. But like a light snow in your yard does not form an even layer and Buffalo receives more snow than Miami, marine snow too is denser in some spots whether an area the size of coffee table or an entire ocean.
McClain goes on to explain how research by him and other scientists (including, most recently, a publication in December's issue of Proceedings of the Royal Society B), has revealed that deep-sea species are incredibly sensitive to even minute differences in marine snow distributions; the tiniest variations in carbon availability translate to vastly different seafloor habitats, at least as far as the marine life living there is concerned. The result is a seafloor mosaic not unlike a patchwork quilt, with each square of "quilt material" corresponding to a unique ecological domain.
These findings help explain not only why you can find such incredible diversity within a small ecological niche (i.e. the handful of seafloor mud from which the species up top were collected), but between them, as well (that is to say, the patch of seafloor located just a few feet away). Read more about the fascinating studies on the patch-mosaic hypothesis of deep-sea life over on Deep Sea News.
Top image by Craig McClain via Deep Sea News; Marine snow by American Scientist via Deep Sea News