Plankton: the true lungs of the earth
The Amazon rainforest is often referred to as the lungs of the Earth, as its trees and plants produce an impressive 20% of the world’s oxygen. Yet, there are organisms that contribute even more to oxygen production: plankton.
Types of plankton
Plankton is a collective term for microorganisms living in water. Most of them drift with the water currents to move. Broadly speaking, plankton is divided into two categories: zooplankton, which resemble tiny animals, and phytoplankton, which are more plant-like. The latter perform a process similar to plants—photosynthesis. Using sunlight, water, and carbon dioxide, they produce sugars and oxygen.
Oxygen production powerhouse
The oxygen production by plankton is not to be underestimated. Phytoplankton is responsible for more than half of the oxygen on Earth. This oxygen is vital for life—from tardigrades in ponds to camels in deserts, and even for humans. Without oxygen, life as we know it would not exist. This life-giving process happens not just in the oceans but also in the pond around the corner. Next time you walk near water, take a deep breath and thank the microbes that make it possible.
A potential climate solution
Phytoplankton’s ability to absorb CO2 is often regarded as a potential solution to climate change. These tiny organisms play a critical role in regulating atmospheric CO2 and are key players in the carbon cycle. When there’s more CO2 in the environment, phytoplankton grow faster and produce more food. With less CO2, their growth slows. This feedback loop makes them essential for balancing Earth’s climate.
Challenges for phytoplankton
However, phytoplankton cannot solve climate change alone. Rising global temperatures make it harder for these microbes to thrive. Like all organisms, phytoplankton have an optimal temperature range for growth. When it gets too hot or too cold, their survival is at risk. Warmer summers often lead to the rapid growth of cyanobacteria, also known as blue-green algae. If global temperatures continue to rise, even these microbes may struggle to grow, impacting the entire aquatic food chain as phytoplankton form its base.
Floating homes and pollution
Ocean pollution is another threat to phytoplankton. Marine microbiologists, who study microbes in saltwater environments, are investigating how plastic pollution affects these tiny organisms. Plastic isn’t directly lethal to phytoplankton but disrupts their growth. It can block sunlight, essential for photosynthesis, or act as a "floating home" for microbes that attach to it and grow. This shift in microbial communities can have cascading effects on the food chain, impacting marine ecosystems at every level.
Earth’s ancient rescuers
Despite the challenges they face, phytoplankton—especially cyanobacteria—should not be underestimated. Throughout Earth’s history, they have transformed the planet multiple times. Over 2.4 billion years ago, during the Great Oxidation Event, cyanobacteria released massive amounts of oxygen into the atmosphere, altering the planet forever. After the asteroid impact that wiped out the dinosaurs, phytoplankton played a critical role in rebuilding marine ecosystems. Every major extinction event in Earth’s history has seen phytoplankton emerge as key players in restoring life.