To calibrate the glider's carbon dioxide and oxygen sensors, a make-shift chemistry lab was set up on the back deck of our fishing vessel. Water samples were taken for these parameters, together with nutrients, and we also profiled with a CTD (an instrument that measures temperature and salinity).
Our fishing boat chem lab. Water samples needing to be kept chilled were stored in our portable mini-fridge (middle left).
Seawater was collected using a Niskin bottle (top center) on a metal cable. A CTD (bottom center) was attached beneath the bottle at the bottom of the cable. A winch was then used to lower the bottle/CTD to the desired sampling depth.
The ends of the sampling bottle are initially cocked open. Once the bottle has been lowered to the desired depth, a metal weight ('messenger') is sent down the cable, triggering the ends of the Niskin to snap shut, thus capturing seawater at the bottle's depth.
The bottle is then winched back up to the surface and water samples extracted from it using a hose - in this case for nutrients.
Here, a sample for carbon dioxide has just being collected.
Chemicals need to be added to the samples for oygen and carbon dioxide - something requiring a steady hand on a moving boat.
Photo credits: Doug Piercey Jr
