Imagine a dark, cold ocean. It is so deep that it is pitch dark. You probably wouldn't imagine much life there at the seafloor. But guess again. The slopes of the Rockall Bank, hundreds of meters below sea level, are home to one of the largest coral banks of the world. How is it possible that corals live in such a harsh environment, where do the organisms get their energy from? That's is an important quest of the ATLAS project. A Dutch initiative, under the name NICO (National Initiative on Changing Oceans), allowed ATLAS researchers to visit Rockall Bank with the research vessel Pelagia.
“You're on the Atlantic, some of the most hostile seas in the world”, warn the fishermen in Galway when asked for advice. We are about to set sail to Rockall bank, a day and a half sailing from the calm peaceful harbour. That is, when the weather agrees.
It all starts great, dolphins chase the ship, the sunset is magnificent, and the atmosphere on board is festive: we are finally going! Off on a new adventure. Looking for cold water corals in the deep, dark, cool sea. The big quest of the expedition is to find out how it’s possible that these animals survive the harsh environment they are living in. The schedule is tight, chief scientist Dick van Oevelen has a strict plan: make measurements at 7 locations and, pick up the equipment he installed a year ago.
As soon as we leave the relative tranquil bay, pass the Aran Islands and reach the open sea, it turns out the fishermen knew what they were talking about. Wind force 8. The waves that hit the ship are so tall that the view from my cabin at the third deck resembles that of a washing machine. Pelagia looked like a huge ship before, but suddenly feels like a tiny dinghy.
I'm not the only one affected by the motion of the ship. Half of the science team is wiped out. The weather not only causes sea sickness, it also slows down the ship – it doesn't help that one of the two engines is broken - and the waves makes it impossible to use some of the equipment. The multinet for example was supposed to collect samples of zooplankton at different depths, but it is too delicate to handle on the rocking ship. Everyone on board gives it their all. Unfortunately, it slowly becomes clear we will not be able to sample all stations that were planned for. Van Oevelen draws up a new schedule.
Tiny orange dot
After some days the weather gets better. The motion sickness fades away, the mood improves. Everybody has found their rhythm on the ship. The sampling with the CTD, a device that fills water bottles and takes other measurements at several depths, goes smooth, and the multinet collects zooplankton. The time has come to collect the moorings that were anchored to the seafloor and, were measuring the water column for a year. A signal is sent to release the ballast. If everything goes as planned, the instruments will slowly move upward to the surface. Everybody runs to the bridge, to look for the big orange buoy. And yes! There it is! The captain is the first to spot the tiny orange dot and changes course, so we can pick it up.
The equipment is hoisted on board. Everyone is excited. All instruments seem to have worked perfectly the last year. They've collected samples of sedimenting particles and measured the current velocity, salinity, fluorescence, and temperature. But to the biologists on board the most interesting thing are the buoys that floated deep in the ocean. Their smooth orange surfaces have changed into small worlds of their own, overgrown with remarkable sea creatures: sea squirts, anemones, and tiny pink shells.
The measurements are almost ready. Just a few more measurements with the water-bottle equipment, up and down, up and down, suitably referred to as yo-yoing, and we are ready to go back home. Suddenly the scientists notice something strange in the data. Was the phytoplankton first only found in the top layer of the water column, now it appears to have mixed down to a few hundred of meters deep. What is going on? Dick van Oevelen, Christian Mohn and Anna van der Kaaden get very excited.
You would expect the food that is produced in the higher regions near the ocean surface, to slowly sink down. On the way down, it gets eaten by many species. Only the poor scraps make it to the bottom and form a homogeneous layer of not so nutritious food. Hardly enough for the corals to feed on. So how do the corals live, and over hundreds of thousands of years, even formed mounds of hundreds of meters high? The theory of the scientists on board is that the coral mounds create turbulence in the ocean. This turbulence mixes relatively fresh food from the surface to the seafloor. So, the corals alter their environment in their favour, kind of like how the beaver changes the flow of streams to their benefit.
All hands on deck
And now we are finding phytoplankton at great depths. Are these new measurements a true sign that the theory is right, are the corals the real ecosystem engineers by influencing the currents? The scientists are not sure yet. They want to sample a few stations. Van Oevelen immediately asks the captain to sail back to the previous station, a few miles back on the bank, to do some final measurements. The captain agrees, but we have to hurry, there is a storm coming, and it is still a two-day sail back to Galway. In the last few hours of the expedition it's all hands-on deck. Night- or dayshift, everybody chips in to process the extra samples that are taken. At noon the CTD is hoisted on board for the last time. The expedition is over, time to go home.
On the way back, I stand next to Van Oevelen on the deck of the ship. We look at the water, the waves are getting bigger again, it starts to rain. As much as I look forward to standing on solid surface, I realise that I feel a bit sad about going back, that the mission is over. Van Oevelen starts to laugh. “What do you mean, 'the mission is over', the mission is just beginning!” He explains that the most important part of his research, the analysis of the samples and data, is just as exciting as this trip. “The major part of the work, data analysis, the puzzling, is only about to begin.”
By: Edda Heinsman, Freelance Journalist at Nemo Kennislink and NIOC expedition participant
Edda Heinsman is a (freelance) science journalist/writer for the Dutch popular science TV show FOCUS and the website NemoKennislink.nl. She studied physics and astrophysics at the University of Amsterdam. For Kennislink she reported frequently about the NICO-expedition, and was invited to join the mission in search for Cold Water Corals.