Snowcaps to Arabian Sea: How Algal Blooms threaten our Food Chain

India continues to grapple with the coronavirus emergency, but another grave threat to public health is the focus of a dramatic Nature Scientific Reports study to be released on May 4. Its lead author, Dr. Joaquim Goes of Columbia University told Mint, “our planet’s alarm bells are ringing. There are very serious implications for India. All the hard-won economic gains of the past two decades could be wiped out now, just as the pandemic has done for the USA.”

Goes and his co-authors - which include his wife, Dr. Helga do Rosario Gomes - at Columbia’s Lamont-Doherty Earth Observatory, along with colleagues at Sultan Qaboos University in Oman, and Tiangong and Xiamen universities in China, have been tracking the astonishing, exponential spread of a tiny plankton (Noctilucascintillans) in the Arabian Sea over almost two decades.

Once almost unknown in these waters, this “uniquely resilient” organism is now “forming thick, malodorous green swirls and filaments that are visible even from space.” According to Goes, “they occupy an area that is almost three times the size of the state of Texas. And since they are not a preferred food for most higher trophic organisms, they mostly attract only salps, jellyfish and turtles, thereby short-circuiting the food chain in the Arabian Sea. At least 120 million people along these coasts are now at risk. Our countries have to act now, to escape the growing crisis.

The new study, entitled Ecosystem state change in the Arabian Sea fuelled by the recent loss of snow over the Himalayan- Tibetan plateau region, is an unusually all-encompassing snapshot of the interconnected impacts of climate change.

Its abstract explains, “global warming has exerted a disproportionately strong influence on the Eurasian land surface, causing a steady decline in snow cover [in the Himalayas].” This has disrupted “winter convective mixing” which occurs when cold winter winds blow over the Arabian Sea, driving the surface waters down, which are in turn replaced by nutrient rich waters from below. That process allows photosynthetic phytoplankton – the basic building block of our ocean food chain – to thrive, along with all the fish species that eventually result in the seafood bounty so many of us rely on. The spectacular growth of Noctiluca demonstrates the scale of the threat to our nutritional security.

Goes says his study indicates that countries like India now face an unavoidable reckoning, “we cannot deny the Himalayan and Tibetan glaciers are melting. They are central to our weather, food and health security, and feed the rivers that are integral to our culture and identity. Here, you can see the profound changes that are taking place in the oceans as well. Yet, instead of investing in renewable energy resources, and taking advantage of the fact that we are ideally situated in the sunbelt, we continue to rely on fossil fuels to drive the engines of our economy.”

The ocean biologist and his wife (both of them were initially educated in their native Goa) are in lockdown in New York City, one of the worst-hit Covid-19 global hotspots. Goes says, “We have not stepped out for the past 8 weeks. The transition to working from home hasn't been easy, but thanks to technology we have been able to surmount many challenges. I am sure many private enterprises, and even government offices, are realizing that their workers are as productive working from home. With less air travel, and diminished dependence on cars, we are seeing our waterways and air becoming cleaner. For many who believed that we cannot cut down on our dependence on fossil fuels to sustain economic growth, the virus has taught us a lesson.”

The stunning growth in Noctiluca“blooms” has calamitous implications for the economies and societies that surround the Arabian Sea. According to Columbia’s in-house The Earth Institute, “In Oman, desalination plants, oil refineries and natural gas plants are forced to scale down operations because they are choked by Noctiluca blooms, and the jellyfish that swarm to feed on them. The resulting pressure on the marine food supply, and economic security may also have fueled the rise in piracy in countries like Yemen and Somalia.”

Goes told Mint, “exactly the same changes that we report along the coasts of Oman and Yemen are happening (albeit on a smaller scale) not too far from of our fish loving state of Goa. We know that Ratnagiri andVengurla in Maharashtraare already seeing these blooms.” He also shared an alarming video taken last month by a student researcher in coastal Kerala, that clearly shows “patches when the surface seemed to have a yellow hue full of Noctiluca like cells.”

Tracking this spectacularly adaptable millimeter-sized organism has proven to behighly effective, because its presence is dead-certain indication of already-disrupted food chains.

The Earth Institute says, “Unlike diatoms, Noctiluca (also known as sea sparkle) doesn’t rely only on sunlight and nutrients; it can also survive by eating other microorganisms. This dual mode of energy acquisition gives it a tremendous advantage to flourish. [Its] second advantage is that its endosymbionts accumulate a lot of ammonia in the cell, making the organism unpalatable to larger grazers. As a third advantage, the accumulated ammonia is also a repository of nitrogenous nutrients for the endosymbionts, making them less vulnerable to diminishing inputs.”

The prescient decision to track Noctiluca almost twenty years ago has turned out to be the scientific equivalent of hitting the jackpot.

Goes told Mint, “it was a chance discovery by our collaborator Dr. Prabhu Matondkar of the National Institute of Oceanography, who noticed this organism in the waters off the coast of Gujarat. Around 2005, using data from NASA’s ocean color satellite, we also began noticing contrary to what we expected, that its productivity during the winter monsoon was also rising. In 2009, with the help of NASA and the US government, the Indian Space Research Organization and India’s Ministry of Earth Sciences, we began examining the physiology of this organism more closely, and discovered that it was thriving because the Arabian Sea was losing oxygen.”