Thursday, March 5, 2015

What are we pumping from the deep sea?

The Plankton Pump is currently our most efficient means of collecting demersal [near-bottom] plankton from the deep sea. 

This includes both holoplankton (organisms that live as plankton their whole life) and meroplankton (organisms that live in the plankton only during one part of their life, such as larvae of benthic organisms).

Generally, the holoplankton is dominated by copepods (>50%), but other substantial groups include chaetognaths, ostracods, and polychaetes. Meroplankton, on the other hand, is very small and present at very low densities, which means that a very fine filter (mesh) size and a large sampling effort is needed to catch these organisms. However, the meroplanktonic component is of special interest because larvae of benthic organisms or other dispersal stages are very important for the supply and dispersal of benthic populations. Therefore, data about meroplankton is useful for estimating recovery abilities of benthic populations after a disturbance event, such as a mining operation. 

Oliver Kersten, the proud papa of the Plankton Pump free vehicle, flashes a look of satisfaction after a successful recovery.

After the acoustic release is contacted from the ship, the lander floats to the surface with the aide of 8 hard-hat glass floats.

When it is due to surface, everyone gathers on deck to watch for the flash of the strobe in the darkness.

After it is spotted, the captain maneuvers the ship alongside the lander, which is referred to as the "package" so that it can be snagged with a  grappling hook.

It is then walked around to the a-frame, where the winch is used to bring it back on board the ship.

 Recovery of the plankton pump free vehicle through the R/V Thompson's A-frame, made possible by the helpful hands of the ship's exceptional crew. They make even the trickiest of recoveries look effortless.

In order to sample the bentho-pelagic zooplankton community, a free-vehicle was outfitted with two plankton pumps that filter seawater 3 m above the abyssal plain (seafloor) for about 23 hours on each deployment.

Oliver really "dives in" to his work!
After recovery, the samples of each pump are split into two subsamples to allow for both a morphological analysis and DNA analysis. Based on the analysis type, these subsamples are then fixed and preserved in either formaldehyde or ethanol, and further analyzed (sorting, identifying organisms, DNA extraction etc.) back in the lab on land.

Written By: Oliver Kersten, Hawaii Pacific University

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