Shouldn’t we care as much about phytoplankton as we do about the rainforests? – Anagha Raghunandan

The air we breathe is quite special; it contains approximately 21% oxygen. Ever wonder from where all this oxygen comes from? Let me guess, trees, right? What if I say there are microscopic, single celled organisms, called phytoplankton, drifting on the surface of water bodies, and that they are responsible for more than 50% of earth’s oxygen supply. If we take two breaths, for one of them, we need to thank the phytoplankton, even though we do not know much about them in their own natural habitat.

The earth defines what we think of as ‘normal’ and ‘habitable’. Most of the visible organisms live in a relatively limited range of temperatures of 5°C to 40°C and are protected from the sun’s harmful radiation by our atmosphere. The earliest evidence of life dates back to 3.5 billion years ago, in a world with very low or no oxygen levels. These organisms, anaerobic single-celled prokaryotes, known as ‘extremophiles’, did not depend on oxygen metabolism. Instead, they used other molecules, such as sulphur, iron, and hydrogen, to produce energy. These oxygen independent metabolic pathways made early life on Earth possible.

Scientists have reconstructed earth’s ~4.6 billions of years history with the help of geological and genetic evidence. Remarkably, the oldest known bacteria were sophisticated single-celled photosynthetic organisms, ‘cyanobacteria’, that drastically transformed the terrestrial environment, ocean, atmosphere and helped make the planet habitable. The extremes still exist out there, often still dominated by the microbial communities. They are found all over the world, in places like the Himalayas, Yellowstone National Park, Iceland, Kamchatka, New Zealand, Italy, Mt. Lassen, and in the hypersaline bodies of water like Great Salt Lake, and Dead Sea.

These photosynthetic organisms use sunlight just as terrestrial plants do, and to convert carbon dioxide (CO2), water (H2O), and minerals into organic matter and oxygen. Not only that, but certain types of phytoplankton contribute in the formation of trace gases: Dimethyl Sulphide (DMS), sulphate aerosols, and cloud condensation nuclei (CCN), essential for the formation of clouds, which also scatter harmful ultraviolet rays directly back into space to keep our planet cool. They contribute to the marine iodine cycle, the movement of iodine from the ocean to the land, and balance the ozone levels between the troposphere and the stratosphere.

Plankton are also our largest supplier of fossil fuels. When these organisms die, they get buried, compressed, and that ultimately turns into reserves of oil and gas. Every year we consume the oil equivalent of approximately a million years of plankton buried beneath the ocean floor.

Phytoplankton live in the surface layers of the ocean penetrated by sunlight, known as the euphotic zone. The huge biomass formed by surface phytoplankton constitutes the very base of the food chain, thus, are being depended on by larger organisms. Phytoplankton are consumed by protists, groups of zooplanktonic animals, and larvae. These organisms are themselves food for large predators—jellyfish, fish, birds, marine mammals, humans, etc.

However, with water bodies being polluted nowadays, phytoplankton may grow out of control and form harmful algal blooms (HABs). These blooms can produce extremely toxic compounds that have harmful effects on fish, shellfish, mammals, birds, and even people.

We should ask a question, have we done enough to save them like we do for the rainforests on earth? Scientists observed a decline in phytoplankton population in around eight out of ten ocean regions, and estimated a global rate of decline of approximately 1% per year over the last 50 plus years. This can be correlated with the climate change in our atmosphere. So, if the plankton were to reduce or disappear, it would set off a devastating chain reaction in the food chain; impacting about 70% of the human population who live within 60 km of the coastline, who predominantly rely on the aquatic food source. Them being the largest producers of oxygen, we would have less oxygen, and more carbon dioxide in the atmosphere, which could possibly lead to the next Ice Age of our planet.

So what should be done? Just like how agencies are managing the policies to reduce our carbon footprint, they should also start managing water pollution. Bringing awareness among citizens is the first step in managing the crisis.

So, shouldn’t we thank the phytoplankton for that one breath?

– Anagha Raghunandan
10th Grade, Canara High School, Oorva, Mangaluru
anagha_r@icloud.com