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The plankton net is emptied. Photo: Jens Joachim Hiorth

Heave to

10 days ago
Written by Ronald Toppe
Ocean research > Heave to

Heave to

10 days agoOcean research
Written by Ronald Toppe
The plankton net is emptied. Photo: Jens Joachim Hiorth

Friday Statsraad Lehmkuhl slowed to a full stop, and lay still for a couple of hours.

- We heaved to today, Captain Jens Joachim Hiorth wrote in his daily report.

What he ordered was to turn the sails so that they braked Statsraad Lehmkuhl up, and kept the ship still against the wind. Two instruments were to be fired several hundred meters into the depths.

Heave. Photo: Ingrid Wollberg
Heave. Photo: Ingrid Wollberg

Into the depths

The ship is equipped with instruments that take samples of the water automatically around the clock. The content of CO2 and oxygen, the amount of phytoplankton, temperature, and salinity are measured once a minute.

These samples are taken from an intake on the side of the ship, and thus only tell something about the conditions just below the sea surface. The researchers will investigate the depths as well, and on Friday a special sampler was used for the first time.

Thr CTD-instrument. Photo: Ingrid Wollberg
Thr CTD-instrument. Photo: Ingrid Wollberg

The CTD instrument

A metal frame with a white and red plastic cylinder in the middle was hooked onto a 750 meter long line, and dropped to the bottom. The instrument is called CTD, which stands for conductivity, temperature and depth.

Conductivity tells how well the water conducts electricity, and is a way of measuring salinity. The pressure tells how deep down the instrument is at all times. The temperature is recorded all the way, and is used together with salinity and pressure to calculate the density of the water, or the weight if you will. The instrument also measures how much light from the surface there is left.

Immediately

The information is stored in the instrument, and loaded into the PC and sent ashore after the instrument has been hoisted back on board.

- It is cool that we can see all the graphs immediately, says Erlend Mundal, one of the two students responsible for the sampling.

In the video below you see the instrument being used. When the bottom is reached, the line is connected to a counter, which measures how much line that is hauled in using a power block.

The plankton net

After the CTD is back on board the ship, a plankton net is attached to the line. The net is lowered to 200 meters and slowly hauled back. The plankton caught the net collects in a container at the end. The contents of the container is preserved on alcohol, and taken back to scientists on land.

The plankton net. Photo: Ingrid Wollberg
The plankton net. Photo: Ingrid Wollberg

The garbage diary

The guard teams on board have different tasks. One of them is to stand buoy guard; to watch and cry out if anyone should fall overboard. You quickly disappear in sight in the waves out at sea, so this is an important job.

The buoy guard also keeps the garbage diary. Here entries of plastic garbage seen floating around is noted, along with time and direction.

The buoy guard stands at the stern of the ship. Photo: Ingrid Wollberg
The buoy guard stands at the stern of the ship. Photo: Ingrid Wollberg
- Have you seen anything? Photo: Ingrid Wollberg
- Have you seen anything? Photo: Ingrid Wollberg
The garbage diary. Photo: Ingrid Wollberg
The garbage diary. Photo: Ingrid Wollberg
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