Snapshots #42: Algal Blooms

September 8, 2022

This is an archived issue. Sign up here to receive the Planet Snapshots newsletter every Thursday morning.

Halloween supplies have hit store shelves, signaling the official end of summer in the northern hemisphere. Yet as the days shorten and temperatures (supposedly) cool, one unassuming organism continues to flourish with impressive zest: phytoplankton. This microscopic-single-celled-aquatic-photosynthetic organism is the foundation of the marine food web. And when conditions are just right, phytoplankton can exponentially grow in events called “algal blooms.”

Blooms occur when the right mixture of warm water, excess nutrients, and sunlight is achieved — making late spring and summer an ideal time for growth. Phytoplankton contain chlorophyll, the green pigment that allows certain organisms to photosynthesize. So as the phytoplankton grow to epic proportions, so too does the green pigment in the water. Together these give rise to their whirls, swirls, and sweeping patterns. In other words: massive algal bloom + satellites in orbit = sublime images.

Algae encompasses a broad family of plants. And different organisms create different algal blooms (hence the varying colors). But we’re not taxonomists so we’re taking a simplistic approach to classification here. Most of the images in this issue are showing blooms of cyanobacteria, aka blue-green algae, like the above progression in Nevada’s Pyramid Lake. But others, like this summer’s Hood Canal bloom, are caused by coccolithophores, a phytoplankton that turns dark waters a tropical-blue as their calcium carbonate plates reflect sunlight.

Not all algal blooms are harmful. But when they are, they’re bad. If you live in the San Francisco Bay Area then you’re likely aware that recent local news coverage has been a mix of “it’s hot” and “we just had the largest algal bloom on record.” Algae needs the right nutrients to bloom, and — in this very specific sense — wastewater from 8 million people is kale-smoothie-caliber nutritious. If there’s one way to excessively ruin a beach day, it’s an algal bloom spurred by human fecal matter. Just ask those who live by Lake Valencia, Venezuela’s largest freshwater lake that hosts rampant blooms from a constant influx of wastewater.

Of course, algal blooms have far more serious consequences than interrupting day plans, like producing deadly toxins and infiltrating drinking water. Plus they tend to suck all the air out of the room, making them unpopular at parties and fatal for marine life reliant on oxygen. It’s estimated that the Bay Area’s algal bloom killed tens of thousands of fish and could cost $14 billion in overall damages, and that’s just one of hundreds that happen in the US alone.

If you thought climate change wasn’t appearing in this story, then think again. Warmer ocean temperatures, greater atmospheric carbon dioxide, and more shallow coastal water are all factors predicted to benefit algal blooms and harm ecosystem health in the future. The good news is that a number of companies are turning to satellite data to help address this growing threat.

Remember how we mentioned earlier that the green pigment chlorophyll allows satellites to spot algal blooms’ extraordinary patterns? Of course you do. Well that’s what the leftmost panel below shows: a true-color comparison of algae growing in a German lake analyzed by EOMAP​. But there’s far more data that can be gleaned beyond what the human eye can see here. Satellites capture certain spectral bands that enable researchers at EOMAP to calculate the amount of silt and chlorophyll present in the lake, as seen in the middle panels. And these then inform their assessment on the likelihood of a harmful algal bloom event occurring.

Algal blooms are one of Earth’s many beautiful but deadly features. In a certain respect, they’re kind of like Frankenstein: big, often green, not entirely understood, and sometimes monstrous. Yet just because they’re dangerous doesn’t necessarily mean they’re wicked. Simply that, as with all things liable to get carried away, it’s best to keep a keen eye on them.

All imagery Ⓒ 2023 Planet Labs PBC

Editor: Ryder Kimball | Images: Ryder Kimball, Robert Simmon, Max Borrmann, and Julian Peschel