Thomas Ward, September 13, 2010

NOAA Teacher At Sea: Thomas Ward
Aboard NOAA Ship Miller Freeman

Mission: Fisheries Surveys
Geographical Area of Cruise: Eastern Bering Sea
Date: September 13, 2010

The Procedure

The way that we collect data is done by three methods. They are the beam trawl, the benthic sled and the benthic grab. The beam trawl is a metal beam supported by a cable on the ship. Hanging from the beam is a net that when dragged behind the ship opens up. The trawl is pulled behind the ship for a specific amount of time.

The benthic sled is a piece of equipment that looks like it would be right at home on the snowy slopes of Central New York. It is a sled that gets dragged on the bottom and collects plankton (look out Eugene). The net is a finer mesh than the one used on the beam trawl. At the end of the net is a container that collects the plankton, we call it a cod end.  At the opening of the net is a device called the flow meter which looks like a little hand held fan. This performs the function of measuring the amount of water or flow that is going through the net. The meter has a counter on it and needs to be read and reset at each sampling station. This instrument gives the scientists a sense of the volume of water flowing into the net.

Flow Meter
Benthic Sled

The last device we are using is the benthic grab.  This device and the wet bulb on the bridge are instruments closest to my curriculum, Earth Science.  In fact, while on the bridge one officer asked another for the wet bulb temperature, very cool, I almost pulled out my sling psychrometer and compared data.  Any how, the grab is opened up and set and then lowered into the water.  When the grab hits the bottom, the weight and the downward force of the grab forces it shut, and into the bottom, scooping up sediment as it closes.  Of course because of the nature of this scientific expedition we are more concerned with organic matter than sediment.  I will have to say the scientist that I am working with have a natural curiosity toward all of Earth’s wonders.

These devices are deployed one at a time.  After each piece returns to the surface the crew maneuvers the ship so that subsequent samplings are performed at the same area.

I was going to write about life on board but the seas have gotten rougher and I am sea sick.

Leave a Reply

%d bloggers like this: