The CTD takes the Vital Signs of the Sea

Filed Under (cruise blog) by Ting on 22-08-2009 and tagged

CTD (Conductivity, Temperature, Density)

19 collecting the samples from the CTD

I have enjoyed a routine of assisting, Margaret, with the deployment of the CTD. The CTD holds an array of water collection bottles and several sensors that record vital information about the water into which we are sending our 3 different landers to stay overnight. We’ve gotten into the routine of sending down the CTD when the landers first go out and right before they are hauled back onto the boat. You can think of the CTD as taking the vital signs of the ocean just as your nurse takes your vital signs every time you see your doctor.

19 The CTD takes the plungeThe some of the information from the CTD comes back immediately (via a very long cable) to Wecoma’s on-board computer system. Margaret and I watch as a graph is produced that shows temperature, salt concentration, oxygen concentration, and light transmission (clarity). This information is gathered as the CTD is lowered down to about 1 meter above the sea floor. After reviewing this information we can determine from what depths we what to collect our water. While sitting at our computer station we can close a bottle, thus we can choose to collect a sample from any depth. As soon as all the samples are collected we bring the CTD back on board the boat.

Margaret has been collecting samples in search of methane. Methane is a gas that can be found along the Oregon coast, near volcanic vents, within the boundary zones of the Juan de Fuca plate. Methane is also found in smaller concentrations as a product of the decomposition of dead plants and animals. Today, Margaret was quite surprised to find an elevated level of methane show up in water collected from 120 meters. a sight off a Cape Perpetua.

My job on board is to collect water samples that will later be tested for oxygen, nutrients, and salts. I, also, collect and filter water for future pigments and particle detection and analysis.

Me collecting water samples

Me collecting water samples

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