NWO grant for study into harmful algal blooms in melting polar ice

Polar ice is melting faster than ever. Rising temperatures are the main driver, but microscopic algae that have been trapped in the ice for thousands of years may also play a role. Once released, these algae can form blooms: large clusters of algae that discolour the surface. Whereas clean ice reflects most sunlight, such darker patches absorb more heat. The result? Accelerated melting. “It is a self-reinforcing process,” says Uddalok Sen, Assistant Professor of Physical Chemistry and Soft Matter. “But we still don’t fully understand its initial stages.”

To investigate this, Sen scales down the polar environment to a laboratory setting. His team works with tiny ice cubes, just a millimetre in size. These contain frozen algae, just like real polar ice. They then simulate the melting process by melting small, targeted sections of the ice using a laser. “At the poles, the same thing happens: thinner ice or areas with algal colonies melt faster than their surroundings,” Sen explains. Under a microscope, the researchers track how the cells are released, move, and eventually stick together.

Individual algal cells can still move independently, but once they encounter one another, they produce a kind of natural glue that causes them to stick together and lose their mobility. From that point on, they depend on flowing meltwater, which brings different colonies together. In this way, small clusters can grow into visible algal blooms. “We want to understand exactly how that transition works,” says Sen. “How do cells cluster together and under which conditions?”

The newly awarded grant allows PhD candidate Ayushi Bhatt to take on the practical work. In addition, Sen will use the funding to adapt the experimental setup required for the project. “Because we are working with ice and frozen algae, we need to prevent condensation and unwanted warming during measurements,” he says. To maintain stable low temperatures, the entire microscope must be housed inside a specially designed low-temperature box. “That makes it quite a technical challenge.”

Although the research is fundamental in nature, its implications could be far-reaching. Algae form the basis of food webs in polar regions and play a crucial role in global oxygen production. At the same time, large-scale algal blooms and shifting environmental conditions may disrupt ecosystems. “If meltwater transports large amounts of algae into new environments, we don’t yet know what will happen, or what it means for other organisms,” Sen says. Dense algal colonies may also create low-oxygen zones in the water, affecting other species.

The Open Competition ENW-XS is a funding scheme from Dutch research council NWO. These grants of up to €50,000 are intended to support promising ideas and to facilitate innovative and more speculative initiatives within the seven Domain Science disciplines. The proposed research is ground-breaking and high-risk. What counts is that all results, be they positive or negative, must contribute to the advancement of science. In total, NWO has allocated €2.8 million to 56 projects.

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• Open Competition ENW-XS