By Edith Oosenbrug

The oceans of our planet are its green lungs. Every year, with the advent of spring and the rising elevation of the sun, clusters of seaweed wander from tropical latitudes towards polar regions. Spring storms ensure that nutrients, such as nitrates and phosphates, are transported from the depths of the ocean to its surface. Within a few days a greater amount of biomass is produced here than over a comparable area of tropical rain forest.

Research on the high seas

The research vessel, RV Poseidon (1), left Bremerhaven on 6th March with destination Madeira to examine this oceanic spring bloom. It will arrive in the harbour at Funchal on the 22nd. Ralf Schiebel, from the ETH Geological Institute Zurich, is scientific head of the expedition (2). He is accompanied by three further researchers from ETH and others from Kiel and Warnemünde, Germany.

Researchers from ETH will be on the research vessel, RV Poseidon for three weeks. Picture: IFM GEOMAR (1). large

One goal of the expedition is the central Madeira basin west of that island. A long term mooring, belonging to the Leibniz Institute of Marine Sciences at Kiel University (3) will be replaced. Measuring instruments are installed on this mooring that, over the past year, have collected and stored hydrographical data and sediment samples. They will complete a twenty-year series of oceanographical data. "The new data and samples should serve to advance our understanding of marine metabolism," explains Schiebel.

During their journey south, along 20 degrees longitude, roughly every 24 hours researchers will measure salt content and temperature of the water down to great depths. In addition, they will take samples of the water, which they will filter and examine for seaweed with the raster electron microscope (4) when they get back to ETH Zurich. Their focus of their interest are coccolithophores, siliceous algae and dinoflagellates. So far, worldwide there has been no such detailled integrated study of these three important groups of seaweed. The succession of this primary producer, known for many years as "Margalef's Mandala“, builds the basis for the higher food chain.

"Seaweed as climate indicator"

"Apart from its importance in the food chain, seaweed is also responsible for the production of oxygen and greenhouse gases," says Schiebel. Coccolithophores, for example, produce dimethylsulphide (DMS), a gas that is relevant to climate. In addition, when tiny calcium chips – so-called coccolithes– flake off, carbon dioxide is set free. Diatoms and dinoflagellates, on the other hand, withdraw carbon dioxide from the seawater. Gases produced near the surface of the ocean escape into the atmosphere. "If this system becomes unstable, it can trigger numerous positive and negative feedbacks," says the sea geologist.

A precise understanding of seaweed succession is thus of great relevance to climate research, in order to estimate anthropogenic influences and predict climate variability in the medium-term.

The departure of the ETH crew (from the left): Ursi Brupbacher, Hsin-chi Lan and Ralf Schiebel. large

Seaweed can do more; it is also a very reliable indicator of earlier climatic periods. It reacts very sensitively to changes in temperature, solar radiation and the concentrations of nutrients. This means that it is a valuable object for paleo-oceanographic research.

Colourful ocean

To make sure that they're not fishing in muddy waters, the team examines the chlorophyll content of the surface water every day. Global images, taken by the SeaWiFS satellite (5), can be viewed on the internet. These images clearly show the colour of the sea, a direct indicator of chlorophyll content. So the team can quickly localise a build-up of plankton and plot the research vessel's course accordingly. This satellite-supported "remote" steering is guaranteed by colleagues at ETH back home in Zurich.

An ocean voyage – a source of pleasure?

This is Schiebel's fifteenth research voyage to date. All in all, he's spent more than a year at sea. "Naturally, some days are more boring than others. But I enjoy sitting on deck for an hour when things are quiet, looking out to sea," he admits. And he says that it's important to eat well because apart from the research, there's not much else for the researchers on board to do. "If the food is bad, you've got a mutiny on your hands," he jokes.

Satellite SEAWIFS map of 6th March 2004. Green/orange indicate the presence of chlorophyll. Dark blue means "oceanic desert", and white means clouds. Picture: SeaWiFS (5).

As an outsider, one can become quite green when one listens to Schiebel talking about his experiences over the past ten years. But he counters, "Just be grateful you aren't coming. The beginning isn't much fun. Spring in the North Atlantic is the time for storms. 'White John' might strike some of us down at any time with a bout of seasickness!" The stormy weather period might not just be responsible for seasickness for some of us; it can also effect annual variations in the spring bloom of seaweed. "Thanks to a long series of observation data we know that the bloom always follows a similar pattern," says is Schiebel, "and it is this detail that we want to investigate here."

Over the coming weeks, Schiebel will be reporting to ETH Life on the research and the ETH-crew's experiences aboard RV Poseidon. We're looking forward to hearing from them with impatience!