Earth’s Oceans Were Once Green, And Scientists Say They Could Shift Color Again

Earth's oceans were once green due to iron-rich waters and climate change may cause a return to green hues.

Advertisement
Written by Gadgets 360 Staff | Updated: 15 April 2025 20:09 IST
Highlights
  • Ancient oceans were green due to their high iron content
  • Cyanobacteria adapted to green light for photosynthesis
  • Climate change is increasing phytoplankton, altering ocean color
Earth’s Oceans Were Once Green, And Scientists Say They Could Shift Color Again

Green-tinted ocean waters observed near Iwo Island, Japan, resemble ancient Earth's seas

Photo Credit: Pixabay/pexels

Japanese scientists say that the evolution of photosynthesis caused Earth's oceans to be formerly green, as per a report. The study suggests that the oceans supported only single-celled organisms and featured environments with barren landscapes of grey, brown, and black rocks. Within a period of 1.5 billion years, the slow changes in ocean chemistry could help explain why blue-green algae developed both types of photosynthetic pigments. The color of the planet's oceans is linked to water chemistry and life influence.

Before Blue: The Green Ocean Era

According to the report, Earth's oceans were once green. The chemistry and evolution of photosynthesis account for this shift. Discovered throughout the Archean and Paleoproterozoic ages, banded iron formations—which were laid between 3.8 and 1.8 billion years ago—were formed when life was limited to one-celled creatures in the oceans; the continents were desolate gray, brown, and black rock and silt terrain.

Green Seas Sparked Life

The first life using sunlight emerged in the Archean eon, when Earth's atmosphere and seas lacked gaseous oxygen. These creatures started the "Great Oxidation Event," a significant ecological turning point permitting advanced life on Earth, using anaerobic photosynthesis. The "bands" of various colours in banded iron formations capture this change with an oscillation between iron deposits devoid of oxygen and red oxidized iron.

The case for green oceans in the Archean eon starts with an observation: waters around the Japanese volcanic island of Iwo Jima have a greenish hue linked to a form of oxidized iron — Fe(III). Blue-green algae thrive in the green waters surrounding the island, and their ancestors evolved alongside other bacteria that use ferrous iron instead of water as the source of electrons for photosynthesis.

Advertisement

Life Changes Ocean Colours

Photosynthetic organisms use pigments (mostly chlorophyll) in their cells to transform carbon dioxide into sugars using the energy of the sun. Genetically engineered modern blue-green algae with phycoerythrobilin (PEB) grow better in green waters, suggesting that pale-green dot worlds viewed from space are excellent candidate planets to harbor early photosynthetic life.

The color of our oceans is linked to water chemistry and the influence of life. Purple oceans could be possible on Earth if the levels of sulfur were high, red oceans could be possible under intense tropical climates, or a type of algae linked to "red tides" could dominate the surface oceans. As the sun ages, changes in the color of our oceans are inevitable, as nothing is permanent at geological timescales.

Advertisement

 

 

For the latest tech news and reviews, follow Gadgets 360 on X, Facebook, WhatsApp, Threads and Google News. For the latest videos on gadgets and tech, subscribe to our YouTube channel. If you want to know everything about top influencers, follow our in-house Who'sThat360 on Instagram and YouTube.

Advertisement

Related Stories

Popular Mobile Brands
  1. BSNL Rs. 197 Prepaid Plan's Validity Reduced: Old vs. New Benefits
  2. CMF Watch 3 Pro Launched With Up to 13 Days Battery Life: Price, Features
  3. iQOO Neo 11 and Neo 11 Pro Key Specifications Tipped
  4. [Exclusive] Oppo K13 Turbo Series to Launch in India in Early August
  5. ViewSonic X1-4K Pro, X2-4K Pro and SP7 Projectors Launched in India
  6. Vivo V60 Price in India, Features Tipped; Said to Launch on August 12
  7. Xiaomi 16 Series May Include 50-Megapixel Selfie Cameras
  8. OnePlus 15, OnePlus Ace 6 Launch Timeline Leaked, Could Debut Together
  9. Netflix Might Be Using Runway's AI Video Tools in Content Production
  10. Google Pixel 10 Pro Design Officially Revealed Ahead of August 20 Launch
  1. Samsung Galaxy Watch Ultra Gets One UI 8 Watch Update With Wear OS 6 Features
  2. AMD Unveils Stable Diffusion 3 Medium Model With Support for 4-Megapixel Image Generation on Ryzen AI Laptops
  3. Samsung Galaxy Z Fold 7 Reportedly Outpaces Galaxy Z Flip 7 in Pre-Orders in South Korea
  4. Lava Blaze Dragon 5G Price Range, Key Features Revealed Ahead of July 25 Launch in India
  5. Samsung Galaxy Z Fold 6 Price in India Slashed After Galaxy Z Fold 7 Launch
  6. Honor Pad GT 2 Pro With Snapdragon 8 Gen 3 SoC, 10,100mAh Battery Launched: Price, Specifications
  7. CMF Watch 3 Pro Launched With 1.43-Inch AMOLED Screen, Up to 13 Days Battery Life: Price, Features
  8. Netflix Reportedly Testing Runway’s AI Video Tools in Content Production
  9. Vivo V60 Could Launch in India on August 12; Key Specifications and Price Tipped
  10. iOS 18.6 Release Candidate Beta Released Alongside macOS 15.6 RC and More for Both Public and Developers
Gadgets 360 is available in
Download Our Apps
Available in Hindi
© Copyright Red Pixels Ventures Limited 2025. All rights reserved.