Science
Earth from space: Ethereal algal vortex blooms at the heart of massive Baltic 'dead zone'
Where is it? The Gulf of Finland in the Baltic Sea.
What's in the photo? A swirling mass of algae trapped in an ocean vortex.
Which satellite took the photo? Landsat 8.
When was it taken? July 18, 2018.
This striking green spiral emerged in the Baltic Sea during a massive algal bloom in 2018. While the swirling microbes have an ethereal beauty in the image, this belies an unseen danger they brought with them as they created a massive, toxic "dead zone."
The large spiral, which was around 15.5 miles (25 kilometers) across at its widest point, appeared in the Gulf of Finland — an arm of the Baltic Sea sandwiched between Finland, Estonia and Russia, according to NASA's Earth Observatory. The swirl mainly consisted of tiny photosynthetic marine bacteria, known as cyanobacteria, as well as some glass-armored plankton, known as diatoms.
The mass of microscopic creatures was trapped in a large vortex, or whirlpool, created by two opposing currents colliding. It is common for algae to be swept up by ocean currents, creating stunning seascapes when viewed from above. However, it is rare to see such a perfectly formed spiral.
Algae naturally bloom in this region of the sea every summer when vertical ocean mixing brings an abundance of nutrients to the surface. However, in recent decades these blooms have exploded in size and frequency as additional nutrients from human activities, such as agricultural run-off, have been dumped into the water.
Between 2003 and 2020, the average size of algal blooms increased by 13% globally, a 2023 study showed.
Related: 12 amazing images of Earth from space
Although algal blooms can be visually stunning, they can also be extremely destructive. When algae amasses near the surface, it temporarily decreases the amount of oxygen in the waters below, potentially suffocating nearby marine creatures, which filter oxygen from the water to breathe, according to the Woods Holes Oceanographic Institution. Scientists often refer to these oxygen-starved areas as "dead zones."
-
Science19h ago
Mountain-size 'planet killer' asteroid will make a close approach to Earth this week — and you can watch it live
-
Science1d ago
Gaia space telescope helps astronomers image hidden objects around bright stars
-
Science1d ago
'The early universe is nothing like we expected': James Webb telescope reveals 'new understanding' of how galaxies formed at cosmic dawn
-
Science1d ago
Earth from space: Near-lifeless 'Land of Terror' looks like an alien landscape in the Sahara
-
Science2d ago
Saturn's planet-wide storms driven by seasonal heating, Cassini probe reveals
-
Science2d ago
Human ancestor 'Lucy' was hairless, new research suggests. Here's why that matters.
-
Science2d ago
Space photo of the week: Hubble roars back to life with exquisite image of nearby galaxy
-
Science3d ago
Is Jupiter's Great Red Spot an impostor? Giant storm may not be the original one discovered 350 years ago