WEIZMANN INSTITUTE OF SCIENCE
A look at our oceans
In The Vardi Group lab at the Weizmann Institute of Science’s Plant and Environmental Sciences Department, Professor Assaf Vardi and his team study the global impacts of microbial interactions in the ocean. We take a look at two of his recent research projects
Blowing in the wind... is plastic From their use in beauty products through to synthetic textiles, plastics are often the answer to many manufacturing problems across the globe. However, as the plastic in our oceans splinters into smaller pieces without breaking down chemically, the resulting microplastics — defined as particles smaller than 5mm across — are becoming a serious ecological problem. Research by Prof Assaf Vardi, with Prof Ilan
Koren and Prof Yinon Rudich of the Institute’s Earth and Planetary Sciences Department, has shown these particles don’t just end up in landfills — they’re reaching far-flung parts of the ocean, spreading the potential to harm the marine environment and, by entering into the food chain, affect human health. The findings show the level of pollution in what were believed to be pristine marine environments – such as areas of the North Atlantic Ocean, where samples were collected – is much higher than expected. While the way in which oceans absorb
materials from the atmosphere has been widely studied, the opposite process, called
30 Israeli Academia | 2022
aerosolization, had been much less investigated. Identifying and quantifying the microplastics trapped in the air samples was far from easy, but the results were worth the effort. The team showed the source of these particles is most likely plastic waste discarded near shores, which made its way into the ocean before getting swept up by wind through bubbles on the surface and blown hundreds of miles away. Such minuscule fragments can stay airborne
for hours or even days, during which they’re exposed to UV light and other atmospheric components. Following these chemical interactions, the particles eventually fall back into the ocean, at which time they could be even more toxic to any marine life that ingests them. It’s a problem societies will have to deal with
for a long time to come. Like all aerosols, when microplastics interact with other parts of the atmosphere, they become part of large planetary cycles. And even if we don’t add any further plastics to our waterways, the situation will continue to get worse as the plastic that’s already polluting our oceans continues to break up.
Survival of the fewest Phytoplankton have a major impact on the carbon cycle in the ocean, providing up to 50 percent of the planet’s oxygen and acting as a major sink for atmospheric CO2
. Despite their impact, much is
still unknown about these marine organisms — especially when it comes to how they respond to and survive environmental changes. Unbeknown to most, phytoplankton undergo
some of the most extreme population swings on the planet, forming blooms that cover thousands of miles then crashing to barely detectable levels within weeks. Prof Assaf Vardi and his team set out to understand which cellular mechanisms can help cells survive these fluctuations – and go on to form more blooms. To this aim, they developed new technology
that allows them to expose cells to various stresses and observe their reaction under a microscope for periods of 24 hours. It’s an original experimental approach: most research on microorganisms has so far tended to average out the behavior of a group, which can miss the unique strategy employed by each individual cell.
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