seafloor core

seafloor core

Jan. 27, 2012 -- Living 1,000 meters under water in Monterey Canyon, off the coast of California, are tiny critters that burrow in the sediments of the seafloor with their feeding appendages poking out into the water column, their entire life cycle dependent on the quantity of marine detritus or "snow" that settles to the bottom from the surface waters.

The above compilation of deep-sea coastal residents came from a delicately dredged scoop of mud only 7 centimeters in diameter by 5 centimeters deep (5 inches across and 2 inches deep). And this explosion of biodiversity in miniature is unique to its own location. The look and feel of the crowd changes just a few meters away.

The marine snow -- the waste and body carcasses of surface plankton -- does not accumulate evenly on the seafloor. In Monterey Canyon, the sediment changes with the slope of the canyon, but even in areas that are flat the accumulation rates vary. The marine snow falls according to surface currents and plankton population explosions, and gathers and moves in drifts and eddies. Tiny juvenile bivalves and worms swim in the water column and either settle in a location with enough snowfall to feed themselves as they mature, or they die, their bodies joining the marine snow drifts.

Biologist Craig McClain of the National Evolutionary Synthesis Center, recently published in the Proceedings of the Royal Society B paper a study on how the distribution of marine bivalves varies across the seafloor. Comparing datasets of seafloor samples with ocean patterns and running computer simulations, his team found that the complexity of the communities depended significantly on how much food was available in a given location, despite the young swimmers' capabilities for dispersing nearly 750 kilometers from their birth site.

The local communities seem to establish themselves based on average snowfall, with their young doing the same, settling in new homes that may be hundreds of kilometers away, but that don't deviate more than a spoonful in terms of yearly marine snow accumulation.

Courtesy Craig McClain

Row 1 bivalve (mollusk), polychaete (worm), ophiuroid (brittle star), polychaete, bivalve, cumacean (crustacean), amphipod (crustacean)

Row 2 cumacean, sea anemone, aplacophoran (mollusk), bivalve, cumacean, bivalve, aplacophoran

Row 3 polychaete, bivalve, cumacean, bivalve, big polychaete, amphipod, 2 oligochaetes (worms)

Row 4 scaphopod (mollusk), bivalve, aplacophoran, long polychaete, cumacean, amphipod, bivalve

Row 5 bivalve, polychaete, aplacophoran, amphipod, bivalve, amphipod, polychaete

Row 6 ostracod (crustacean), polychaete with tube, bivalve, anemone, polychaete, amphipod, polychaete, bivalve

Row 7 polychaete, gastropod (mollusk), amphipod, caprellid shrimp (crustacean), scaphopod, bivalve, polychaete, cumacean