A LIFE-SUSTAINING RELATIONSHIP:
Ocean & Humans
PART 1 (of 5)
Oxygen: Breathing Life Into Humans
May 14, 2025
The ocean (and the seas) plays a crucial role in sustaining human life. In fact, this relationship goes surprisingly much further than just the opportunity of eating seafood.
Some of the roles the ocean serves
: from removing harmful carbon-dioxide from the air, to releasing oxygen necessary for humans to breathe and for the Earth’s ecosystems to stay functional, to supporting land-based food supply, to regulating our climate, to providing a means for transportation of goods from one place on Earth to others, to driving economies by supporting global trade, to providing livelihood for millions of people, and even to serving our well‑being and pleasures to enjoy the ocean in various ways.
In fact,
about half of the oxygen generated on Earth is by understory marine life (such as plankton or seaweed) in the ocean and the seas. Although there are differing views among experts as to how much (if any) of the oxygen generated by the ocean in our current days is released into the atmosphere (and how much it retains to sustain its marine life), all experts agree that a large part of the abundance of oxygen in the air we breathe today can be attributed to the ocean.
In fact, most of that accumulated over hundreds of millions of years. And yet, even as we have oxygen in the atmosphere enough for millennia, the low-oxygen areas in the ocean are growing, affecting fish life, the ecosystem, and ultimately human life.
Oxygen is an absolute necessity for ecosystems to stay alive
, as well as for many species (including humans).
And, the ecosystems of the Earth are an absolute necessity for humans to stay alive.
So, how exactly does the ocean play a role in our lives? And, why would we not be alive without it? … And, have we mentioned phytoplankton’s role in our lives?
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THE ESSENCE
THE DETAILS
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In the ocean, some of the marine life produce energy
by using the Sun’s light, carbon‑dioxide, and nutrients in the water
(through a process, called photosynthesis) in order to make food for themselves, too grow, and to reproduce—while releasing oxygen in the process
.
  1. Plants, algae, bacteria (plankton) in the ocean produce food for themselves, releasing oxygen in the process
  2. Some of that oxygen enters the atmosphere (the air we breathe)
  3. The air we breathe today contains 21% of oxygen (besides 78% of nitrogen, and other gases), of which:
    • some comes from plants and organisms in the ocean (plankton)
    • some comes from land plants (i.e. trees, shrubs, etc.)
    • much of it accumulated in the atmosphere over millions of years
    • despite comprising only 21% of the air, oxygen is the very gas that plays a crucial role in sustaining our lives
  4. Our human bodies take in oxygen by breathing it in (ventilation) ⟶ uses that oxygen for the process of respiration (part of metabolism) to release energy from the food we eat ⟶ which then removes carbon‑dioxide from our bodies by exhaling (breathing it out)
  5. Our released energy powers the essential life processes within our bodies (all the way down to the cellular level), such as muscle function, nerve function, maintenance of our body temperature … and more.
  6. Oxygen is necessary for sustaining many forms of life—from ecosystems, to various species, including humans
And, when it comes to generating the oxygen, in the first place, size is by no means a determinant of importance. In fact, the tiny single‑celled organism (called phytoplankton) in the depths of the ocean quite literally plays the role of make‑or‑break for human life … and for the Earth, as a whole. So, what is phytoplankton, and what does it do to provide for our lives?
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the nitty‑gritty
PHYTOPLANKTON:
THE TINY SINGLE-CELLED ORGANISM IN THE OCEAN THAT’S CRUCIAL IN SUSTAINING HUMAN LIFE
  • WHAT IS PHYTOPLANKTON
    • Microscopic organisms* (bacteria, protists, or single‑celled plants) that live in the ocean surface and watery environments, and provide for human life in various forms
    • Phytoplankton produce food for themselves in order to grow and to reproduce
    • They use the process of photosynthesis to generate chemical energy
    • During photosynthesis, they use sunlight + carbon-dioxide + nutrients from the sea ⟹ Release oxygen
    • Lifespan of the phytoplankton is only a few days ⟹ Its reproduction and growth level are essential to even the healthy sustenance of human life
  • WHY THEY ARE IMPORTANT
    • Release oxygen that humans need
    • Remove harmful carbon‑dioxide from the air
    • Provide for the plants and wildlife (both in the sea and on the land) that become part of the food supply chain to feed humans
    • Support the life of plants, fish, wildlife of all sizes (from microscopic plants to fish to multi‑ton whales)
  • PHYTOPLANKTON’S NICKNAMES
    • ‘The foundation of the aquatic food web’
    • ‘The oceanic biological productivity’
      • ⟶ next
      • ⟵ back
      • ⟹ consequently
      • ⟸ as said before
    EXPAND ALL COLLAPSE ALL
    • THE CONNECTION:
    Phytoplankton ⟷ THE EARTH’S CLIMATE ⟷ HUMAN LIFE
  • CARBON‑DIOXIDE
    • During photosynthesis (when producing food for themselves), phytoplankton consume carbon‑dioxide. In other words, Phytoplankton sucks some of the harmful carbon‑dioxide from the air that humans breathe.
      • Some of this carbon‑dioxide is carried to the deep ocean (when phytoplankton die)
      • Some are transferred to different levels of the ocean as phytoplankton is eaten by the different ocean creatures
    • The amount of carbon‑dioxide consumed by phytoplankton is on scale equivalent to that of forests and land plants
    • This “Biological Carbon Pump” transfers ~10 gigatonnes of carbon from the atmosphere to the ocean each year ⟹ Even small changes in the amount and growth of phytoplankton affect the carbon‑dioxide level in the air ⟹ which affects global surface temperatures
  • OXYGEN
    • As part of the photosynthesis process, phytoplankton release oxygen
    • Oxygen is essential for sustaining marine life, for maintaining the ecosystems, for the food supply, for regulating the climate, for the ecosystems to be able to support human life, and for humans to breathe in order to stay alive
  • THE CONNECTION
    • Phytoplankton‑amount and growth (in the ocean and seas) = Productivity level
    • Change in phytoplankton productivity = Change in: fisheries, human food supply (even those grown on land), level of harmful carbon‑dioxide in the air, the climate of the Earth, and essentially the sustainability of human life
    • Growth in human‑generated greenhouse gases in the atmosphere ⟹ Phytoplankton cannot keep up with removing enough carbon‑dioxide from the air ⟹ The ocean surface becomes warmer and warmer ⟹ The warm and cold layers of the water become less able to mix vertically ⟹ Nutrients from the cold deep water cannot come up to the warm surface water that’s needed for the phytoplankton to photosynthesize ⟹
      • Less photosynthesis = Less “Productivity” = Less removal of carbon-dioxide from the air, and less oxygen generated by phytoplankton = Lesser food supply chain security for humans = Greater level of climate change
      • ⟶ next
      • ⟵ back
      • ⟹ consequently
      • ⟸ as said before
    EXPAND ALL COLLAPSE ALL
THE SIMILARITIES BETWEEN OCEAN‑GROWN Phytoplankton AND LAND PLANTS, such as forests:
  1. As some of the phytoplankton in the ocean die, they sink to the ocean floor, and part of their organic carbon is buried; and remains so for millions of years. However, if disturbed (or dug up in some ways) that carbon can be released into the atmosphere.
  2. Forests and other land plants also take in carbon‑dioxide through photosynthesis, and retain it as long as they are not disturbed. Cutting the forests or plans (or disturbing their environment), however, releases the stored carbon‑dioxide into the air ⟵ not good for humans.
  3. Even if oceans or forests are not taking in more carbon‑dioxide or releasing more oxygen, the human activities (e.g. driving cars, burning oil, etc.) increase the amount of carbon‑dioxide into the air ⟹ Causing the Earth to warm.
WHAT CAN YOU DO ABOUT IT?
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In fact, quite a lot. Even if you don’t live near the ocean, your everyday habits affect the health of the ocean … and, as a consequence, it has an effect on your health and well-being. There are simple everyday actions you can take to contribute to a healthy ocean … and a healthy you.
RESPECT THE OCEAN & THE SEAS
At the base of taking care of the ocean lies respect for its power, which literally enables the proper functioning of human life. This respect in our minds can trigger our actions that are essential in taking care of the ocean … so that it can continue to take care of us.

And, that includes not only the enormous ocean, but also all watery ecosystems.
When there is a choice between buying disposable or re‑usable products, choose the re‑usable.

When there is choice between buying plastic and paper, keep in mind that plastic doesn’t completely decompose, and stays around for decades or even centuries. Much of it ends up in the ocean.

If you can make good use of your existing products (such as electronics, clothing, etc.) for longer, do so, instead of replacing them too soon, and unnecessarily.
BE MINDFUL OF WHAT KINDS OF PRODUCTS—HOW MUCH, AND HOW OFTEN—YOU BUY
RECYCLE
If you already bought plastic products (including plastic water bottles), recycle them. Don’t just throw them away—because they will end up in the ocean … causing pollution, and ultimately affecting human life—including yours.
Be there. Feel its power. Remember its role in your being alive.
VISIT THE OCEAN AND THE SEAS, THE RIVERS, THE MARSHES, THE WETLANDS … and all
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