When the waters in Hood Canal and other waterways connected to the Salish Sea start to take on the turquoise hues of the Caribbean, it means the coccolithophores have arrived. Though they were a bit tardy this year, these microscopic, plant-like organisms have become regular summer visitors in Washington’s waters.
When present in great numbers, coccolithophores can make even the darkest green or navy blue waters turn a bright blue; this is a result of their chalky calcium carbonate plates (coccoliths) that reflect light. Like most phytoplankton, coccolithophores float near the ocean surface and turn sunlight and carbon dioxide into sugars and oxygen. In turn, they become food for the grazing zooplankton, shellfish, and finfish. Coccolithophores and other phytoplankton also play an important, but not fully understood, role in the global carbon cycle, taking carbon dioxide out of the atmosphere and eventually sinking it to the bottom of the ocean.
Satellites spotted the latest coccolithophore bloom in Hood Canal this week. The Operational Land Imager-2 on Landsat 9 acquired the image above on August 21, 2022. The image below was acquired by the Operational Land Imager on Landsat 8 on August 20, 2022.
“We didn’t see such a bloom last year, although we were all looking hard for it,” said Teri King, a marine water quality specialist with Washington Sea Grant at the University of Washington. This year’s bloom was late to appear, as it took awhile to get the right blend of water temperatures. Water in Hood Canal does not always mix well, meaning the upper layers can have different temperatures and salinities than deeper layers—leading to stratification. While other phytoplankton species are often limited by low nutrient conditions, coccolithophores can thrive.
“The later bloom this year might be an artifact from the spring conditions,” King explained. “We had an incredibly wet, cold spring and, biologically, things are delayed. For example, our clams are just spawning now when we normally see them spawn in May and June.”
King and colleagues run several citizen-science and applied science programs—including Bivalves for Clean Water and SoundToxins—to monitor and document harmful algal blooms, unusual bloom events, and new species entering the Salish Sea. King’s team has identified the coccolithophore species this year as Emiliania huxleyi, one of the most common and abundant on Earth.
“E. huxleyi has a host of biotechnology uses because of its anti-parasitic, anti-tumor, antibiotic, and anti-fungal properties,” King wrote. “This species is not toxic, and does not harm fish, shellfish, or hinder any human recreation.”
NASA Earth Observatory images by Lauren Dauphin, using Landsat data from the U.S. Geological Survey. Story by Michael Carlowicz, with reporting from Kathryn Hansen.