Ocean Colour Change

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A satellite-derived image of Earth showing the Atlantic Ocean and surrounding continents, overlaid with false-colour data indicating phytoplankton concentrations. Bright greens and yellows highlight dense blooms near coastlines, particularly where the Amazon River meets the sea. Deep blues and purples mark nutrient-poor waters farther offshore. This image, based on NASA SeaWiFS data from 2003–2006, visualises chlorophyll levels that reflect the abundance of microscopic phytoplankton. These organisms photosynthesise using chlorophyll, and their seasonal growth is fuelled by land-borne nutrients and winter mixing. Blooms peak in spring and decline by early summer as nutrients are depleted and grazers multiply.

The edge extends
past grey-rims
drawn through
old plankton maps.
Where blue thins,
a green-thick seam
unspools,
threading north
with nothing
to net.
Each swell carries
a drift-line echo:
hunger’s anchor,
drifter’s bloom.
No signal,
just a reshaping –
shoal-quiet,
current-bent,
a pattern slipped
from one hinge
to another.
And further down,
the fish-shadows
turn,
but not back –
never back.

A satellite-derived image of Earth showing the Atlantic Ocean and surrounding continents, overlaid with false-colour data indicating phytoplankton concentrations. Bright greens and yellows highlight dense blooms near coastlines, particularly where the Amazon River meets the sea. Deep blues and purples mark nutrient-poor waters farther offshore. This image, based on NASA SeaWiFS data from 2003–2006, visualises chlorophyll levels that reflect the abundance of microscopic phytoplankton. These organisms photosynthesise using chlorophyll, and their seasonal growth is fuelled by land-borne nutrients and winter mixing. Blooms peak in spring and decline by early summer as nutrients are depleted and grazers multiply.
Phytoplankton blooms flourish along coastlines and across oceans, driven by nutrient surges from rivers and winter storms (Image Credit: NASA Goddard Space Flight Center, via Wikimedia Commons).

This poem is inspired by recent research, which has found that oceans are getting greener near the poles and bluer in the subtropics.

Ocean colour change is one of the clearest signs of shifting marine ecosystems in a warming world, and over the past twenty years, the colours of our oceans have shifted. Greener tones are moving closer to the poles, while subtropical waters are turning a deeper blue. This change is more than visual. Instead, it signals a shift in phytoplankton – the microscopic organisms at the base of the marine food web. Like plants on land, phytoplankton use sunlight to grow. However, as the oceans warm, their growth patterns are changing. These changes matter because phytoplankton support marine ecosystems and help absorb carbon dioxide. As a result, shifts in where they thrive could affect marine life, fishing industries, and coastal communities.

In this study, researchers used satellite data from 2003 to 2022 to measure ocean colour. This allowed them to track chlorophyll, a key marker of phytoplankton. Their results showed a clear trend: chlorophyll levels are rising near the poles and falling in the subtropics. In particular, this pattern is most evident in the Northern Hemisphere. Therefore, the growing contrast – described as “greener green and bluer blue” – reveals a widening gap in ocean productivity. Furthermore, such shifts in phytoplankton could ripple through food webs and alter ecosystem balance. These changes could have wide-reaching effects, from declining fish stocks to disrupted economies. Ultimately, it is vital to understand how warming seas are reshaping life in the ocean, and what this means for the future.

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