Tuesday, September 4, 2012

The Video Plankton Recorder

Hello, this is Alex. Each day during this survey portion of our cruise we are deploying our Video Plankton Recorder (VPR) down to a depth of 1000 meters on 3 to 4 casts per day. The VPR is mounted below the Conductivity, Temperature, Depth sensor (CTD) rosette with its Niskin bottles used to collect seawater for chemical analysis.  The VPR's strobe light can be seen flashing in this deployment video as it illuminates plankton that are then captured by an adjacent high-magnification camera.

Did you see a jelly pass in front of the descending rosette?  It is too large to be fully imaged within the VPR's frame of view, though we often get partial pictures of large gelatinous organisms.  Each frame is 14 X 14 millimeters and 15 frames are recorded per second.  We have a computer program that automatically selects images that fit our criteria of brightness, focus, and size in order to select and save zooplankton pictures.  Here are some particularly nice pictures from our casts on this cruise, including pteropods, the primary target of our research.

Limacina helicina pteropods; although actual species
identification can be difficult with these images,
we have net samples which give us supplementary information

A cute jelly
An amphipod with buggy eyes
A colorful copepod

Beautiful blue jelly
Fun with krill

This chaetognath, or arrow worm, has a brood of eggs on her "hip"
They are ambush predators in the plankton
Collecting in situ images allows us to see the structure of fragile gelatinous organisms, which collapse out of water and can easily be damaged by nets.  The VPR also gives us the exact location of animals in the water column, and we can couple environmental information from the CTD with the depth distribution of the animals to learn more about their habitat needs. Essentially the VPR is like an underwater microscope -- rather than using nets to bring animals up to the surface where we then look at them under a microscope, we're taking the microscope to them!

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