When we think about what moves the ocean, we usually picture crashing waves, raging storms, and powerful tides. That’s not wrong—but it’s not the full story either. Beneath the surface, there’s another force quietly mixing the seas: marine life itself.
This hidden process is called biogenic ocean mixing. It might not get much spotlight, but it plays a surprisingly important role in how the ocean works—and possibly even in how the climate behaves.
Let’s break it down in plain English.
What Is Ocean Mixing—and Why Should You Care?
Ocean mixing is the process where water from different layers of the ocean blends together. It helps distribute heat, salt, oxygen, and nutrients throughout the sea.
Why it matters:
- It feeds plankton and fuels marine food webs.
- It helps regulate the Earth’s climate.
- It supports life from the tiniest organisms to the largest whales.
Traditionally, scientists believed this mixing was mostly driven by winds, tides, and differences in water temperature. That’s still true—but it turns out those aren’t the only players in the game.
The Surprising Role of Marine Life
Over the last couple of decades, researchers have started realizing something wild: swimming animals may be mixing the ocean too.
This process, called biogenic mixing, is exactly what it sounds like—mixing caused by living things.
Imagine thousands of tiny animals moving up and down every day, or schools of fish swimming in tight formation. These movements create small currents and turbulence that can help stir ocean layers together.
It’s like stirring your coffee with a spoon—but the spoon is alive.
Meet the Mixers: Creatures That Move Water
So who’s doing the work down there? Here are a few standout contributors:
Zooplankton
These microscopic drifters migrate up and down in the water column every day—some traveling hundreds of meters. Their mass movement stirs up water and nutrients, especially at night when they rise closer to the surface.
Fish Schools
When large numbers of fish swim in sync, they displace serious volumes of water. This can create localized mixing zones, especially in coastal areas or around reefs.
Jellyfish and Krill
Jellyfish pulse through the water using jet propulsion. Krill swarm in massive numbers and flutter their tiny limbs like underwater snow blowers. Both can create vertical mixing as they move through layers of water.
Did You Know?
- Zooplankton migration is the largest animal movement on Earth. Every night, trillions of tiny creatures rise hundreds of meters toward the surface—and return by dawn. It's called diel vertical migration, and it happens across the globe, every single day.
- Krill may look small, but together they outweigh all humans on Earth. Their massive swarms can stretch for kilometers and are a key part of ocean mixing and food chains.
- A single jellyfish can move more water than you’d expect. Some species can displace tens of liters per hour just by pulsing through the water.
- Biogenic mixing can reach hundreds of meters deep. In some places, the turbulence caused by animals has been measured as being as strong as that created by ocean tides.
How It Actually Works
Mixing isn’t just about movement—it’s about how that movement affects the layers of the ocean.
- When an animal swims, it pushes water around its body.
- In large groups, this movement adds up to turbulence—tiny swirls that can break down the boundary between different water layers.
- Over time, this helps nutrients rise up from the deep and oxygen trickle down.
Even though an individual jellyfish or plankton might only create a tiny disturbance, billions of them moving together can have a huge cumulative effect.
Does This Really Matter on a Global Scale?
Here’s where it gets interesting—and controversial.
Some scientists argue that biogenic mixing is significant enough to rival winds and tides, at least in certain parts of the ocean. Others say it’s a smaller effect, but still worth studying.
Either way, recent studies using high-tech tools—like underwater drones, dye tracers, and computer models—suggest that the impact of marine life on ocean dynamics has been underestimated.
Why It Matters for More Than Just Ocean Nerds
Understanding biogenic mixing isn’t just about satisfying curiosity. It connects to some big-picture issues:
- Nutrient Cycling: More mixing means more nutrients reaching surface waters—fueling plankton blooms that support the whole marine food chain.
- Carbon Cycle: Plankton absorb carbon dioxide. If mixing changes where and how plankton grow, it could impact how much CO₂ the ocean can store.
- Climate Models: Current models may overlook the role of marine life in moving heat and carbon. Including biogenic mixing could improve predictions.
There’s Still a Lot We Don’t Know
Despite the excitement, there are still many unanswered questions:
- How much mixing is really happening due to biology?
- Where is it strongest?
- How does it change with seasons or climate shifts?
Researchers are working on it—but it's tricky. Studying this stuff in the open ocean isn’t easy. It takes creative tools, funding, and a lot of patience.
Final Thoughts: The Ocean Is More Alive Than We Thought
We often imagine the ocean as a passive body of water, shaped only by weather and gravity. But it turns out it’s being stirred from within—by the very life it supports.
Every time a fish swims, a krill wriggles, or a jellyfish pulses, it’s adding energy into the system. And when enough of them do it together, it changes the way the ocean works.
In other words: the sea doesn’t just carry life—it’s moved by it.
As the old proverb goes:
"Even the smallest drop can cause ripples across the pond."
Marine life may be tiny—but together, they might be stirring the world.