Way up at the top of Tara’s mast sit two funnels that look like the two halves of an orange. All day and through the night, these so-called inlets collect outside air so that Tara’s onboard researchers can monitor it for aerosols—tiny airborne particles that can have a big impact on the weather and the ocean ecosystem.
Once air passes through the orange inlets, it enters black tubes that snake down to a large motorized pump below TARA’s decks. The pump pulls the air into four circular filter chambers, each about the size of a hockey puck. “We are pumping all day,” says Guillaume Bourdin, TARA’s oceanographic engineer. “All the particles in the air are in those filters.” After extracting the aerosols from the air, Bourdin sends his filters back to Israel’s Weizmann Institute of Science. Michel Flores, a Weizmann researcher, will try to identify particles collected in those filters using tools like an electron microscope.
Les deux capteurs d’aérosols placés en tête de mat – Vincent Hilaire / Fondation Tara Expéditions
Ocean aerosols interest Bourdin and Flores because the prevalence and composition of these aerosols can affect the marine environment profoundly. For one thing, Bourdin says, aerosols influence the climate and can alter weather patterns. The transfer of aerosols between the atmosphere and the ocean’s surface affects cloud formation and can play a key role in large-scale climate processes. Some ocean particles that rise into the air allow Bourdin to interpret the state of life below the water’s surface. “Iron is a micronutrient used by phytoplankton to grow,” he says. “In some areas of the Pacific, the very low concentration of iron is limiting phytoplankton growth, the first level of the food chain.” But when iron is transported by aerosols, it can encourage phytoplankton growth in ecosystems that are iron-limited. This enrichment most likely affects other animals higher up on the food chain.
Un filtre d’aérosol récupéré sur un des “entonnoirs” – Maéva Bardy / Fondation Tara Expéditions
Flores also wonders if infectious particles can be transported in the air between two remote places. Bourdin hopes to collect viruses or bacteria on his filters that would reveal whether they can travel long distances through the air and still infect hosts, as reported in a previous study. Some of these viruses infect phytoplankton and can cut off algal growth sharply in just a few days, stopping a bloom of phytoplankton. Like iron particles, then, airborne viruses can play a major role in oceanic cycles. Using the data he’s gathered so far, Bourdin also hopes to improve the precision of computer models that could predict how aerosol particles affect the ocean ecosystem and climate. It’s important to know what aerosols are doing now, he says, to understand what could happen in the future.
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