Friday, May 17, 2013


Collecting water from the rosette CTD
Taking water samples from the rosette CTD
SBE #19 -- the CTD used on the mini-bongo and
sub-surface nueston nets
We use a lot of other gear in addition to nets while on the ship. One of most important are our CTDs, or Conductivity-Temperature-Depth devices. These can range from small cylindrical models to large frames that have water collection bottles (Niskin bottles) attached to them. Each one reports data back to the ship via a wire connecting to an onboard computer. We have one of the less involved versions attached to our subsurface neuston frame and use it to monitor the depth of the net. The rosette CTD goes down to hundreds of meters in depth and measures not only salinity, temperature, and depth but also chlorophyll and dissolved oxygen; its attached bottles are triggered by one of the Foster's survey techs at a computer to collect water at 50 meters, the surface, and wherever the chlorophyll maximum is. 

Those water samples taken by the rosette CTD are filtered using a vacuum pump onto filter pads. These pads are taken and used to measure the concentrations of various chlorophylls in the water column. 

A third device we use on every net tow is a flowmeter. This piece of gear looks like a tiny rocket and hangs in the net frame. We record the numbers on the side at the start and the end of the tow and use these, along with the size of the frame, to calculate the amount of water moving through the net. 

Last but not least -- drifters! We have a pile of these large floating balls that we deploy at areas we think have an interesting current pattern. They have a long "sail" that hangs down through the water column and is supposed to prevent movement due to wind and aid with movement due to currents. A transmitter inside the drifter connects to satellites which relay its position back to us. From this information we can track direction and speed of currents. 

Taking the filter pads off of our chlorophyll vacuum
K. Doering removing the filter
pads off the vacuum pump
to save them for further
Drifter. The ball floats on top of the water while the blue sail
(stretched out to the left) hangs down below.

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