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Images: The Mysterious Movements of Deep-Sea Larvae

Tiny larvae of deep-sea organisms, such as this 350-micron-long larva of a deep-sea gastropod, Bathymargarites symplector, are the aquatic animal equivalent of seeds. The larvae are dispersed in the deep sea, carried by oceanic flows, and settle at vent sites where they find nutrients to grow.

{From the Photographic Identification Guide to Larvae at Hydrothermal Vents in the Eastern Pacific by S.W. Mills, S.E. Beaulieu, and L.S. Mullineaux http://www.whoi.edu/science/B/vent-larval-id]. (Photographic Identification Guide to Larvae at Hydrothermal Vents in the Eastern Pacific)

A larva of a deep-sea bivalve called Bathypecten vulcani collected on the East Pacific Rise. Its diameter is 840 microns (the width of a human hair is about 100 microns).
[From the Photographic Identification Guide to Larvae at Hydrothermal Vents in the Eastern Pacific by S.W. Mills, S.E. Beaulieu, and L.S. Mullineaux http://www.whoi.edu/science/B/vent-larval-id.] (Photographic Identification Guide to Larvae at Hydrothermal Vents in the Eastern Pacific)

WHOI biologists used stacked plastic plates, called "sandwiches" (left), as artificial substrates for larvae of vent animals. The sandwiches were deployed on the seafloor near a hydrothermal vent site with Alvin and later recovered (center) to see how larvae (tubeworms, in the right photo) settled and grew on them. (Skylar Bayer/Brown University; WHOI Alvin Group/LADDER III cruise)

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WHOI scientist Dennis McGillicuddy used a computer model developed by NOAA scientist Bill Lavelle in a series of experiments that simulated where particles—representing larvae released at a mid-ocean ridge—would end up. In the experiment above, light blue dots represent starting points of particles released 10 meters above the ridge crest, spaced 1 kilometer apart and spanning 20 kilometers across the ridge crest. Dark blue lines indicate their pathways; red dots represent where they ended up 30 days after release.

(Courtesy of Dennis McGillicuddy, Woods Hole Oceanographic Institution)

In the first experiment of its kind, a specially designed injector system on the submersible Alvin released a jet of sulfur hexafluoride(SF6), a harmless chemical tracer, from a 50-millimeter orifice. The SF6 dissolved into the seawater, and scientists tracked where it flowed over the next several weeks to learn how oceanic flows might disperse the larvae of deep-sea organisms. (P.R. Jackson, J.R. Ledwell, and A.M. Thurnherr)

Between 32 and 52 days after the tracer was released at about 9°30'N (around No. 2 on the left map), researchers took 100 samples of water in various locations (or "stations," indicated by numbered circles) to see where the tracer dispersed. White circles=no tracer found; pink=a little tracer; red=a lot of tracer found. Stations 2 through 53 of the tracer survey (left map) showed the tracer had moved to 9o50’ N, demonstrating that larvae could make the 20-mile trip along the ridge axis within a larval lifespan. Stations 54 to 100, sampled subsequently, showed that the tracer moved about 50 kilometers west of the ridge, before heading back toward the same ridge it came from. (Courtesy of Jim Ledwell, Woods Hole Oceanographic Institution)