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1. Fishing for micro-plankton

2. Ross and Mike awaiting net

3. Ross and Mike dressed for the cold

4. Ross and Mike collecting samples from net

From: Graham Quartly
Date: Thu, 18 Dec 2008 19:46
Subject: Fishing for micro-plankton

On Wednesday, I resolved to find out what Mike and Ross were doing during one of our CTD stations.

Normally when we stop to lower the CTD (Conductivity-Temperature Depth) sampling package over the side, I will be manning the console watching the data come in, and guiding the winch driver as to how close to the sea bottom it has got. While that was happening I would hear message on the radio about 'Nets down to 50m'; so yesterday I left Matt and Terri in charge of the CTD monitoring and followed Mike and Ross to the front of the ship.

They are interested in the micro-plankton found in the water column, and go fishing for them with a long net. The net has a pressure-controlled opening at the top, so when it is lowered through the water and then hauled back, it only remains open for a certain depth range. This allows Ross and Mike to see what is lurking in the water column below 50m, without their sample being contaminated by surface-dwellers.

Inside the net is a series of meshes to sieve the plankton according to their size. When the system is brought on-board, Mike and Ross collect the content of the net bottles that look a little like large milk bottles. These plankton samples are then taken to the lab for analysis under the microscope.

Graham