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Earth Matters

August Puzzler Answer: Bloom in the Baltic Sea

August 26th, 2015 by Kathryn Hansen


When I first saw the image for the August puzzler, I was struck by its beauty. The blue-green swirls look like they could be the brush strokes of an impressionist painting. Instead, this false-color scene was acquired by the Operational Land Imager (OLI) on Landsat 8.

Without any land visible in the scene, I thought it would be at least a day or two before receiving a correct guess. I was wrong. Congratulations to Helen Macintyre who was the first to correctly post a correct answer to the blog on August 18, just 94 minutes after the puzzler was posted.

Macintyre wrote, “Initially I thought hurricane, but the strands in the upper left seem too sharp and thin. I think this is an algal bloom swirling in ocean currents. The line near the top I think is a large ocean liner cutting through this, leaving a darker colored wake.”

Indeed, the scene shows a phytoplankton bloom. This particular bloom contains cyanobacteria—an ancient type of marine bacteria that, like other phytoplankton, capture and store solar energy through photosynthesis.

Later that same day, Kari Nöjd posted a comment and became the first to correctly guess the phenomenon and its location. In fact, Nöjd was the only participant to correctly place this bloom in the Baltic Sea. Excellent work!

Nöjd wrote, “My guess is that this picture shows sea surface where algae is blooming. The line is from the boat, which is driving through the sea surface. Picture could have been taken from the Baltic Sea where has been big algae blooming fields forming for the past month … Unfortunately this is also effect of a human behavior. Nutrients from fields and waste waters increase the algae blooming.”

According to NASA oceanographer Norman Kuring, major cyanobacteria blooms like this one appear in the Baltic Sea nearly every summer, “and they always look like this in the satellite data.” Physical measurements from an expert in the field, however, were required to confirm that the bloom was cyanobacteria.

As for the line cutting through the scene? Yes, that’s the result of a ship cruising through the bloom. There are other ships too, as well as an airplane, visible in the zoomed-out version posted in our August 23, 2015, Image of the Day.

On Facebook, Scot Hoffman was the first to guess algae bloom. In fact, a lot of comments on Facebook noted that the scene was a bloom, but the location remained elusive. Many thought it might be Lake Erie—a good guess because blooms are visible during the summer in that lake as well.

One Response to “August Puzzler Answer: Bloom in the Baltic Sea”

  1. Peter says:

    It looks just like the clouds. Wonderful!