S 29° 36’ 4″ E 95° 00’ 33″ – One winter’s evening in Callao, in Spain’s viceroyalty of Perú, Luis Née packed his botanical equipment for a voyage. The 59-year-old botanist had arrived in Perú with the Malaspina expedition from Australia in late July 1793. The Descubierta would continue through the Strait of Magellan to Buenos Aires, on the other side of the continent. Née would walk.Here on the Hespérides, people are starting to talk of going walkabout, too, when we reach Australia. They’ll have to walk a long way to make up for the month’s confinement and isolation. Over the weekend, we reached our most remote point: almost 1,000 nautical miles from the Île de Amsterdam, a tiny French island. Australia was straight ahead and equidistant. The ship was in the heart of an oligotrophic gyre, a part of the ocean with fewer nutrients than coastlines, coral reefs, or upwelling zones. Unlike Née, whose assignment was to plunge through a land filled with life, the modern Malaspina expedition is sifting through the loneliest of seas.
Oligotrophic zones lend themselves to relentless routine. Visit Martí Galí Tàpias in the late morning in his shared, single-porthole laboratory at the waterline and he will be fiddling with hoses and dials. Visit the biogeochemist in the late afternoon and he will be shuffling bottles from one shelf to another in his laboratory, concentrating samples in liquid nitrogen and reading a printout from his chromatographer. Visit him after the evening meeting and he will be in his laboratory, cleaning bottles and planning tomorrow’s collections and experiments. The graduate student at the CSIC’s Institute of Marine Sciences (ICM) in Barcelona is measuring dimethyl sulfide (DMS), a gas emitted by plankton which some researchers suspect of helping to seed clouds at sea.
Neé would probably have understood. He averaged almost 28 kilometres a day, including a visit to the volcano Chimborazo in modern-day Ecuador, on one 500 kilometre stretch of his journey (Missouri Botanical Garden) and returned over one thousand plant specimens to Spain (Australian National Herbarium). Galí’s labor is better measured in nanomols per litre. Every morning he collects his daily allotment of water from the sampling rosetta and returns to his cramped laboratory at the ship’s waterline. There, Galí siphons off gas from the water and passes it through a chromatographer to measure the DMS.
“Look. The amount of DMS dropped during the storm,” he says, running his finger over a dip in a chart of DMS he’s measured since we left Cape Town. “Otherwise it’s about the same day to day,” he adds. Something is keeping the DMS levels stable.
In 1987 Robert Charlson, James Lovelock, Meinrat Andrae, and Stephen Warren proposed the idea that DMS, a byproduct from plankton and microbes, could rise to the surface, mix with atmospheric gases, and form sulphur aerosols, which some researchers think promotes cloud formation (Nature 326, 16 April 1987, p. 655). If extra sunlight hit the sea, DMS production might rise. The extra gas could form additional clouds, which would reflect back some of the extra sunlight, and restore the sea, and its DMS-producing denizens, to its previous state. The idea was that biology might serve as the planet’s thermostat.
Many studies have explored the DMS cycle since then, Galí says, though there is little agreement in his research community over how DMS influences cloud formation. Instead, he’s trying to tally up how much DMS each plankton community produces and how much of the gas escapes to the atmosphere. With his freshly-caught batch of plankton each morning he measures the DMS in the water, then tries to tease out how much of the DMS gets consumed by certain microbes, how much gets broken down by sunlight, and how much is left to escape into the atmosphere. “These things should depend on local conditions, but the overall DMS produced by the communities here doesn’t seem to change very much,” he says.
One possibility is that some species respond to short-term changes in light levels or stress or temperature by producing more DMS while other species produce less. “We want to see how productivity changes with these environmental variables in high resolution,” Galí says, during a break from the lab to watch the sun set and eat an orange. High resolution means that he must visit his laboratory first thing in the morning and throughout the evening, in addition to normal working hours, to keep up with the continual flow of water and DMS.
On Saturday afternoon the ship’s residents celebrated Carnaval with a costume contest. Galí wore a foil costume labeled “Turbo Molecular Pump” but had to slip belowdecks in the middle of the celebration to make a measurement using one of his real instruments. Written in black marker on the back of his costume were the words, “It’s not an obsession.”
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