The image above, "Eye of an Algal Storm" was captured by the European Space Agency's Sentinel-2A satellite over the middle of the Baltic Sea on 7 August. With a spatial resolution of just 10 metres, ripples and waves are captured in stunning detail. In the top centre of the image, you can even make out the wake of a ship as it slices through cyanobacteria-laden waters.
Here's another, slightly more zoomed-out view of the algal bloom from the same day:
Algae blooms make striking pictures, but they also produce toxic pollution and eat up all the oxygen in the water, choking out other marine life forms. That's why we now have a 11,265km² dead zone in the Gulf of Mexico. There are a lot of things that can cause algae to grow like weeds, including warm waters, calm seas and fertiliser pollution. (The first two are implicated in the current Baltic bloom).
Meanwhile on this side of the Atlantic, algae fed by phosphorus-rich agricultural run-off are making the Great Lakes look unusually emerald. Scientists studying Lake Erie say it's almost certain to be the worst bloom on record.
And if that wasn't enough, a warm Pacific Ocean blob is feeding another massive algae bloom, one that runs the entire length of the west coast from Alaska to California.
This bloom, composed mainly of pseudo-nitzschia algae, is particularly worrisome because it's producing domoic acid, a potent neurotoxin that can make its way into mammals via shellfish. Fisheries in affected areas have been closed for the US summer.