Table of Contents
Phytoplankton produce oxygen through photosynthesis, allowing organisms like us to breathe and survive.
When the earth came into existence 4.55 billion years ago, it was hardly a planet that could host life. The atmosphere lacked oxygen and was largely made up of carbon dioxide. The temperatures weren’t hospitable either, much like modern-day Venus. The planet underwent massive changes over the years to host life. One of the primary needs of life is oxygen; in some ways, water played a part in how oxygen came into our world.
How did oxygen form?
Even before oxygen arose, Earth needed to have water to house life. The leading theory says that water came to Earth through collisions with asteroids.
The early atmosphere demanded an organism that could survive in the absence of oxygen. About at halfway age, Tiny blue-green algae or cyanobacteria rose to the occasion. These microorganisms performed photosynthesis by using carbon dioxide and water to produce glucose and the essential by-product: oxygen.
All this oxygen was initially trapped inside minerals and seawater, but soon, cyanobacteria started to produce enough oxygen to oxygenate the atmosphere. This event is known as the Great Oxidation Event.
Most of the oxygen now is produced by phytoplankton deep in the ocean. Notably, the smallest bacteria capable of photosynthesis, Prochlorococcus, produces 20% of the world’s oxygen, which is more than the tropical rainforests combined.
Is phytoplankton a plant?
If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck… right? Just like land plants, phytoplankton are green, filled with chlorophyll , and turn carbon dioxide into oxygen! Yet, there are some key differences. Phytoplanktons are not plants. Instead, there are two kinds: diatoms and cyanobacteria. These are protists and bacteria respectively.
Diatoms are eukaryotes . Eukaryotes have cell membranes and are relatively complex. Plant and animal cells fall under this category, making diatoms more similar to plants. Diatoms are also famous for their beautiful, crystalline snowflake shapes!
The second kind of phytoplankton is a prokaryotes . These cells do not have cell membranes and are simpler. They are actually bacteria that can photosynthesize! The large majority of these are known as cyanobacteria.
Cyanobacteria also have the special distinction of being one of the oldest organisms on Earth. In the first two billion years of the Earth’s existence, it was not a hospitable place to live! There was very little oxygen, and most of the atmosphere was carbon dioxide and nitrogen. Cyanobacteria photosynthesized until the whole planet changed, and the atmosphere became 21% oxygen!
How do plants make oxygen?
Most of the oxygen on Earth comes from a process known as photosynthesis. Three essential components are necessary for photosynthesis. Carbon dioxide, sunlight, and a pigment known as chlorophyll. Plants photosynthesize to make carbohydrates, which provide them the energy to grow, flower, and make seeds.
Chlorophyll is responsible for giving plants their distinctive green color. It performs a very unique function. Chlorophyll traps sunlight and converts light energy to chemical energy. This powers the reaction of photosynthesis!
Carbon dioxide and water are the raw materials needed to make carbohydrates. Carbohydrates are large molecules made of carbon and hydrogen. Using the energy from sunlight, plants combine carbon dioxide and water. Combining the carbon dioxide and water means getting rid of the oxygen present. Life-giving oxygen, which is so important to us, is actually a waste product for plants!
In short, plants combine water and carbon dioxide using energy from the sun to produce carbohydrates. Oxygen is a waste product of this reaction.
Phytoplankton are full of chlorophyll too! Even though they are not the same organisms as plants, they still photosynthesize in the same way, to produce the same things.
Where does our oxygen come from?
Approximately half of all the oxygen on Earth comes from phytoplankton in the ocean! Larger kelp and seaweed are also ocean oxygen producers . This brings the total ocean oxygen production up to 50-80%. The smallest photosynthetic organism, Prochlorococcus, produces 20% of the world’s oxygen all alone!
Mosses and ferns are also one of the most important producers of oxygen. The Amazon rainforest is known as the ‘Lungs of the Earth’.
Phytoplankton and the Food Chain
Phytoplankton are primary producers and are at the base of all oceanic food chains. The energy which supports life on Earth comes from the sun. Plants convert sunlight to other forms of energy, supporting organisms which cannot photosynthesize.
Imagine a hungry lion. It feeds on deer which roam in the savannah, and the deer feed on grass. The grass converts sunlight into chemical energy. The lion would not exist without the grass.
Phytoplankton are the grass of the ocean! Phytoplankton are fed on by slightly larger, non-photosynthetic plankton. These are eaten by smaller fish, then bigger fish, then by predators like sharks or dolphins!
Phytoplankton occupy the category of primary producer. Then come the primary consumers, secondary consumers, tertiary consumers, and quaternary consumers. Rarely do ecosystems have more than four levels, as energy is lost along every step of the food chain.
From changing the atmosphere of prehistoric Earth to still being the largest producer of oxygen, we have a lot to thank phytoplankton for! The role of these organisms is definitely much larger than their tiny size would suggest.
Glossary
Chlorophyll: A green pigment that traps sunlight
Eukaryotes: Simple cells with no cell membrane
Producer: An organism that uses sunlight to create carbohydrates
Prokaryotes: Complex cells with cell membranes
Flesch Kincaid Grade Level: 7.6
Flesch KinkaidReading Ease: 46.4
Contributors
Copyright @smorescience. All rights reserved. Do not copy, cite, publish, or distribute this content without permission.
