GO-Flo Bottles

The GO-Flo bottles are a tried and true way to collect water samples.  They are based upon collection techniques that do not require electronic triggering or major metal components.  You may think the ones featured here are similar to those used on the CTD Rosette, but if you look closely you will see many differences.

The name comes from a combination of the manufacturer and the method of sampling.  The bottles are made by General Oceanics, and they allow water to flow through them once past the initial top layer of water, and up until they are triggered to close.  The tubes are made of stout PVC that can be sent to depths of 500m or more.  These particular bottles also incorporate minimal metals in their overall composition which make them perfect for very specific samplings.

In our case, they are being used to collect samples to study trace metals in the waters of the Gulf of Mexico.  To have an aluminum frame, stainless steel parts, use a steel rosette with sacrificial zinc nodes, or even rest the bottles on the side of a ship made of iron with rust would contaminate the samples.  Great care is taken in ensuring there are no particles accidentally added to the bottles before they dive down to the depths.  They are brought out of a clean room, with both the top and bottom covered with plastic bags, and attached to a special line that is coated with a synthetic material.  Granted there are a few pieces of metal holding this bottle intact (wing nuts, springs), but substantially less than a Niskin bottle on a typical Rosette.  While it is resting on the side rail of the ship, it is not allowed to touch the metal.  The crew fashioned a custom wooden shelf to keep the bottle, still with its bags on, pristine. 

The GO-Flo bottles are attached one at a time to the line.  The top and bottom of the tube are equipped with a stopper ball, which first must be rotated 90 degrees to close it.  The bottle goes into the water closed to avoid any surface level contaminants or pollutants.  Their presence would not create an accurate profile of what the scientists are looking for in the water column if they were to remain in the sample.  As the bottles are lowered past the surface, the increased water pressure causes the pressure release valve to pop in and the ball at the top and the bottom of the bottle to roll open 90 degrees.  The bottle is also equipped with a “messenger” that will later trigger a chain reaction to close each bottle. 

In our deployments, we have been sending down 5 bottles at each location.  Once all 5 bottles have been closed, sent down to a specific depth of interest, and the triggers set, a messenger is sent down.  This one is basically a shuttle that rides down the line and collides with the valves on the bottles all down the line to trigger them to close.  We hold the line to feel for each one to close.  After some time, we give the signal to pull them back up, and the careful process of bringing them to the clean room begins.  There, both filtered and unfiltered water samples are collected using every precaution to minimize the samples’ exposure to any trace-metals or contaminants on board.