There's a Surprising Connection Between Dangerous Algal Blooms And The Himalayas
A loss of snow and ice on Earth's highest mountain peaks could be driving dangerous changes in the food chains of distant coastal water, according to new research.
Like a gardener turning over soil, cold winter winds blowing down from the Himalayan mountains are known to fertilise the Arabian sea by chilling the surface and causing the dense waters to sink, only to be replaced with fresh currents rich in nutrients.
Due to climate change, however, winter monsoons are rapidly becoming warmer and moister, leaving marine habitats with less oxygen and nutrients, and allowing microbes that thrive in an oxygen-depleted wasteland to bloom instead.
Recently, it's gotten so bad, the thick green swirls of algal blooms can actually be seen from space.
What you're looking at is Noctiluca scintillans - also known as sea sparkle for its bioluminescent effects. This is a millimetre-long marine dinoflagellate that can survive and thrive without oxygen or sunlight. Before the turn of the century, however, its presence along the coasts of Somalia, Yemen, and Oman was practically unheard of.
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"This is probably one of the most dramatic changes that we have seen that's related to climate change," says Joaquim I. Goes from Columbia University, who has been studying the rapid rise of this organism for more than 18 years.
"We are seeing Noctiluca in Southeast Asia, off the coasts of Thailand and Vietnam, and as far south as the Seychelles, and everywhere it blooms it is becoming a problem. It also harms water quality and causes a lot of fish mortality."
Using field data and NASA satellite imagery, scientists have now connected the rise of these algae blooms to melting glaciers and a weakened winter monsoon.
"Collectively, these changes have resulted in an increase in net-heat flux from the atmosphere into [Arabian Sea] surface waters that indicates an increase in the upper [Arabian Sea] ocean heat content since 2000," the authors write.
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On the other hand, Noctiluca can survive in harsher environments, sometimes even by eating other microorganisms. Additionally, ammonia easily builds up in their own bodies, making the algae a particularly nasty, even poisonous morsel.
In today's rapidly changing Arabian Sea, this deadly and adaptive behaviour appears to be "short-circuiting the food chain", leaving fish poisoned, diatoms outcompeted and jellyfish numerous.
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In countries like Somalia and Yemen, the authors fear this annual bloom, which is only getting bigger with the years, could harm local fisheries, leading to further unrest, poverty and deprivation as climate change strengthens its grip and the Himalayas continue to melt at an unprecedented rate.
"The inability of large zooplankton, except salps and jellyfish to feed on Noctiluca, is indicative of the capacity of Noctiluca blooms to short-circuit the trophic food chain,"
https://www.sciencealert.com/shrinking-snowcaps-in-the-himalayas-might-be-driving-harmful-algal-blooms-in-the-arabian-seaEcosystem state change in the Arabian Sea fuelled by the recent loss of snow over the Himalayan-Tibetan Plateau region (OA)
https://www.nature.com/articles/s41598-020-64360-2
