The world’s oceans hold a deep secret: glowing stretches of water known as the ‘milky seas’ that cast an otherworldly haze over the horizon. Scientists are on the cusp of unraveling the mystery behind this phenomenon, which may reveal new insights into the ocean ecosystem and its role in the Earth system.
The ocean has long been a source of fascination and mystery, and one phenomenon that has captivated sailors for centuries is the ‘milky seas‘ – glowing stretches of water that cast an otherworldly haze of green and white, spanning to the horizon and beyond. But what causes this eerie display, and how can scientists predict when and where it will occur?
Milky seas are rare and unusual ocean phenomena where the water appears milky white due to a high concentration of bioluminescent 'organisms'.
These microorganisms, such as dinoflagellates, emit light when disturbed, creating a glowing effect.
This occurs in tropical waters with low oxygen levels, allowing the organisms to thrive.
Scientists have observed this phenomenon in various parts of the world, including the Mediterranean and the Gulf of Mexico.
The search for answers has been ongoing for decades, with researchers creating a database of every recorded sighting over the past 400 years in the hope of teasing out an underlying pattern to the phenomenon. A new paper published in the ‘journal Earth and Space Science‘ reveals that by analyzing this data, scientists may be able to observe the milky seas and collect samples that have so far eluded them.
Bioluminescence is believed to be the key to unlocking the secrets of the milky seas, but what creature produces it? Researchers have identified a strain of bacteria, ‘Vibrio harveyi‘, which is known to be bioluminescent. However, more research is needed to confirm this theory and understand its role in the ocean ecosystem.
The milky seas are incredibly rare, with only one known photograph taken at sea level, and a water sample collected by a research vessel’s chance encounter in 1985 near the ‘Yemeni island of Socotra‘. This strain of bacteria remains the prime suspect, but it’s far from conclusive evidence. Other questions remain unanswered, such as what role milky seas play in the ocean ecosystem, or how they fit into the carbon cycle.
Recent insights gleaned from modern satellite imagery, combined with mapping hundreds of years of accounts, suggest that the milky seas are concentrated around the ‘Arabian Sea‘ and ‘Southeast Asian waters‘. The timing of sightings appears to be statistically related to the ‘Indian Ocean Dipole‘ and the ‘El Niño Southern Oscillation‘, recurring climate patterns that involve changes to the temperature of the waters.
The regions where this phenomenon occurs most frequently are around the northwest Indian Ocean near Somalia and Socotra, Yemen, with nearly 60 percent of all known events occurring there. However, more research is needed to fully understand the significance of milky seas in nature and their potential impact on the ocean ecosystem.
As scientists continue to unravel the secrets behind the milky seas, they are reminded of the incredible expressions of our biosphere that remain unexplored. The existence of these glowing stretches of water points to uncharted connections between the surface and the sky, and between microscopic to global-scale roles of bacteria in the Earth system.
