Off the coast of New Zealand, scientists have spotted vast milky white plankton blooms—a stunning yet troubling sign of rising ocean temperatures.
These blooms, composed of coccolithophore algae, may seem harmless, but their increasing presence signals a fundamental shift in ocean ecosystems, one that echoes changes seen 130,000 years ago when Earth last experienced significant warming.
A Natural Process with a New Twist
Coccolithophores naturally shed their calcium carbonate shells, or coccoliths, which create white clouds in the ocean before sinking to the seafloor.
However, what’s alarming scientists is that these blooms are appearing farther south, an indication that New Zealand’s cooler waters are reacting to human-caused global warming.
Researchers from Victoria University of Wellington have charted these blooms using satellite imagery and ship observations.
Their findings align with past warm periods in Earth’s history, showing that when ocean temperatures increase by just 1 to 2 degrees Celsius, coccolith deposits surge.
According to lead researcher Bella Duncan, sediment samples from the ocean floor confirm this pattern.
“Our results show that during the last warm period, sediments on the seabed were mainly made up of coccoliths,” Duncan explains.
This suggests the New Zealand ocean is now responding to modern global warming in a similar way.
A Pattern That Challenges Our Assumptions
Many assume that the ocean can act as an endless buffer against climate change, but this new research suggests that protection is breaking down.
While previous studies have shown that the oceans have absorbed 93% of human-caused global warming since the 1970s, this has come at a steep cost.
Josh Hrala from ScienceAlert explains: “Our oceans have absorbed the brunt of climate change, becoming sicker in the process. T
his could explain why temperature changes on land have not been as extreme as in the water.”
The consequences of these changes go beyond plankton migrations.
Warmer waters are fostering harmful bacterial growth, disrupting fish populations, and altering the carbon cycle.
Scientists are now racing to understand what this means for marine ecosystems, carbon dioxide absorption, and oceanic health in the decades to come.
The Future of Our Oceans
To connect today’s bloom events to prehistoric climate shifts, researchers extracted 200,000-year-old sediment cores from the Campbell Plateau, south of New Zealand.
These cores revealed that coccolith abundance spiked during warm periods, reinforcing concerns that history is repeating itself.
“While the ramifications on fish stocks, carbon dioxide uptake, and general ocean health have yet to be fully understood, it is clear that change is underway,” says scientist Lionel Carter.
Coccoliths play a critical role in tracking oceanic temperature shifts, but their impact extends further.
These phytoplankton marine plants are vital to the marine food web, absorbing carbon dioxide for photosynthesis and supporting diverse ecosystems.
However, their migration signals a dramatic shift that could impact the entire oceanic carbon cycle.
With ocean surface temperatures now at their highest levels in over a century, these observations aren’t just academic—they’re a call to action.
The more we learn from these changes, the better we can prepare for the inevitable consequences of warming seas.
