6 April 2016

The professor and the dead zone

Meet the Professor! 134 professors gathered on Wednesday, 30 March at Dom Square to visit primary schools in Utrecht and surroundings to speak about their research. Marine scientist Caroline Slomp rode her bicycle to the Groen van Prinsterer School in De Bilt.

Caroline Slomp used the Dutch word ‘monster’, which means sample, to talk about her sea specimens. The pupils of group 7 were completely confused. They had been looking forward to the professor’s visit for five months already and had an idea of what kind of person she would be in their heads. They had understood that the professor researches ‘dead zones’, but now they believed that this friendly woman hunts sea monsters. Caroline was thrown into confusion when told by the teacher that the children didn’t understand her. She laughed. Of course! Although she had tried to avoid using professional terms, she wasn’t aware  that ‘monster’ was also one.


Caroline Slomp regularly travels to the Baltic Sea aboard a large ship to research blue algae, which is responsible for the deoxygenation of large bodies of water. The dead zone in the Baltic is one and a half times as big as the Netherlands. She tells us as we are biking from Dom Square to De Bilt that people often ask her ‘Who are you going with?’ As it is her research, she arranges the ship and composes the team.

Blue algae in the sea is normal,  but to have so much of it isn’t. She asks the class what could be the cause of this increased amount and what does algae need to grow? ‘Sunlight’ answers a girl cautiously. ‘Yes, but what do you need more?’ asks Caroline. ‘Water’ comes the answer. Caroline responds ‘Yes, the sea has plenty of it. But algae are plants, like trees or houseplants. What do you give to plants at home to make them grow?’ ‘Manure!’ ‘That’s right!’ How manure gets into the sea is a difficult process to understand. ‘And why do you find more blue algae in the Baltic Sea than in the North Sea?’ ‘Climate?’ ‘Heat? Caroline nods cautiously: temperature is an important factor, but it is not the cause. A boy answers: ‘A lot of countries are located around the Baltic Sea.’ ‘Yes, that’s the answer’ says Caroline. ‘That is how more manure gets into the Baltic Sea. The sea is also less open than the North Sea and the sea water doesn’t mix very well in the Baltic.’

Blue water

Fresh water is lighter than salt water and the two do not mix easily. It is time for an experiment to show this. In an aquarium filled with fresh water, Caroline opens a bottle filled with blue-coloured salt water. The blue water stays at the bottom of the aquarium. In another experiment Caroline shows how to take a sample of the seabed. She has brought a layer cake and an apple corer. Every child can take part in the drilling. Everything that can go wrong on the seabed also happens in the classroom. By accident, your bore is not level and a sample falls from the corer etc.

‘How could we get rid of the dead zones?’ Caroline asks the pupils. Scientists have already thought of everything the kids come up with: blow oxygen into the sea, clear the algae, add something to the sea to kill the algae, etc. But all of these solutions are too expensive or cannot be done. Such a challenge makes science fun: you always encounter new things you don’t understand and you are always searching for an answer that doesn’t exist yet. It’s a beautiful definition: science is what you cannot find in Wikipedia.


Caroline says she is satisfied when biking back to Utrecht Science Park. ‘Did you notice the girls were more reserved about asking questions than the boys?’ When Caroline was around that age she thought experiments were a bit scary. Look at what she is doing now!