The student who counts sea slugs
Ever since he was a child, Verboom has been fascinated by snails and shells. ‘I’d say I’m fairly knowledgeable’, he says. This knowledge came in handy when the RUG, in collaboration with Naturalis and Stichting Anemoon, was putting together an international research team to study Bonaire’s marine biodiversity. ‘There was no one in the team who would be studying molluscs, so they invited me.’
He says the past three weeks were ‘an amazing experience’. Verboom was sent out to count the slugs who eat coral, like the Coralliophila and the Cyphoma, with the latter also being called ‘flamingo tongue’.
He also drew up a list of all the molluscs living in the island waters. ‘To do that, I had to gather almost two hundred grams of sand during every dive I did.’ Now that he’s returned home, he will be studying the sand to find out what kind of shells it contains.
Bag full of sand
Getting the sand back to Groningen turned out to be quite the challenge. ‘We were allowed 23 kilos of luggage on the plane, and I had a bag full of diving gear’, says Verboom. ‘But on the way back, I was carrying twenty bags of sand, and my luggage was way too heavy.’ He dumped his diving gear and returned home with a bunch of sand.
At Bonaire, he did approximately thirty dives; twice a day. He would check the number of slugs at a certain location and catalogue which types of coral they ate. ‘I mainly did a lot of counting.’
Occasionally he would go on the third dive at night. ‘That’s when other animal come out of the woodwork, so I had a better picture of all the molluscs in the area’, he explains. Some sea slugs are nocturnal, which means the nighttime dives provided him insight into which corals they ate.
The team tried to make dives in all the waters around the island. ‘Many people come to Bonaire to dive, but they mainly focus on the west side, where there are beaches and a lovely reef close to the beach’, says Verboom.
But the researchers also went diving on the east side, where there are pointy rocks and big waves. ‘We were hit by metre-high waves’, says Verboom. The team spotted turtles and two different kinds of sharks. ‘That was pretty cool.’
Expedition leader Bert Hoeksema, professor by special appointment of biology at the RUG, had studied sea slugs together with a student of his before, but that was on Curaçao. ‘But nobody had ever studied these slugs around Bonaire, of whether they have any serious impact on the health of coral reefs’, says Verboom.
The official results still need to be calculated, but he can give us a little preview. ‘I can cautiously say that the animals aren’t a threat to the coral reefs.’ That’s a good thing, he says, since, in contrast to the rest of the world, the Bonaire coral reefs are doing pretty well.