From more than 400 miles above Earth, NASA is tracking some of the planet’s smallest life forms drifting just beneath the ocean’s surface to monitor how global warming affects ocean health. 

The microscopic organisms known as phytoplankton fuel the entire aquatic food web. They provide food for small fish, zooplankton and crustaceans like krill that are then eaten by larger pelagic species like tuna and whales. Without them, the oceanic food chain would collapse. They also play a vital role in our carbon cycle. 

Similar to plants, phytoplankton absorb carbon dioxide from the atmosphere through photosynthesis and store it in their single-celled bodies. When they die and decompose, some of this carbon falls to the ocean floor. Every year, about ten gigatonnes of carbon is transferred from the atmosphere to the deep ocean through this process. 

But not all phytoplankton are alike. There are at least a hundred thousand different species, which vary in color, size, composition and function. While most are benign, sudden growth in some species caused by temperature changes or influxes of nutrients can result in harmful algal blooms, which can poison or suffocate fish and other marine life and cause respiratory distress and other illnesses in humans.  

NASA’s newly launched Plankton, Aerosol, Climate, ocean Ecosystem satellite (PACE) is now—for the first time from space—distinguishing between different types of phytoplankton and monitoring their distribution around the world. 

Measuring Ocean Color 

Equipped with state-of-the-art technology that observes a wide range of the electromagnetic spectrum of the ocean, land and the atmosphere, PACE is able to detect the unique pigments of different phytoplankton groups. Unlike previous satellite technologies that were used to observe the planet in six to eight colors, PACE’s hyperspectral sensor, the Ocean Color Instrument, can produce images in more than 100 different colors, from the ultraviolet to near infrared. 

“By filling in all of those gaps in the rainbow,” we are now able to view the planet like never before, said Jeremy Werdell, a NASA oceanographer who has overseen the mission’s operations and development over the last decade as PACE project scientist. “It’s like putting on glasses. Before it was fuzzy. Now, it’s clear.” The first image produced by PACE was released to the public last month, showing two distinct phytoplankton communities drifting off the coast of South Africa in late February—one a bright pink community of Synechococcus phytoplankton and the other a neon green community of picoeukaryotes algae.

But, PACE is not only tracking phytoplankton. It is also observing tiny airborne particles floating through the atmosphere called aerosols and monitoring how they interact with the ocean. While aerosols may include particles generated by fossil fuels, pollutants and soot, they also include natural particles including volcanic ash, wildfire smoke and sea spray. 

Each of these has an impact on the climate depending on their makeup and color. Lighter colored aerosols reflect sunlight and have a cooling effect on the atmosphere. Darker ones absorb sunlight and cause the atmosphere to heat up. 

Some, like wildfire smoke, fuel phytoplankton blooms by depositing extra nutrients in the ocean, according to a study on the impact of Australian wildfires on phytoplankton blooms in the Southern Ocean. 

The more scientists learn about how the ocean and the atmosphere interact, as well as how carbon moves through the ecosystem, the better they can predict future climate change, said Werdell.  To date, he said, “These are places that have the highest unknowns in climate modalities.”  

Early Adopters

Several years prior to launch, PACE initiated its Early Adopter program to train researchers specializing in a wide range of fields including fisheries, aquaculture, air quality, climate and agriculture, how to analyze and interpret the new satellite data. 

Currently, around thirty different scientists are gearing up to apply PACE data—which is free and available to the public—to their research and make sure local communities benefit so they can make more informed climate decisions, said Werdell. “These resources are gifts that really do impact everyday lives,” said Werdell. 

Michelle Tomlinson, an oceanographer at the National Oceanic and Atmospheric Administration (NOAA) and expert in forecasting harmful algal blooms, has been a part of the PACE Early Adopter program from its inception. She is gearing up to use PACE data to help provide more accurate data on harmful algal blooms to the public.

 “It will help us provide better information to the management community and those grappling with these blooms,” Tomlinson said. 

Harmful algal blooms are becoming increasingly frequent and widespread, in large part because of climate change and increasing pollution. Last summer hundreds of sea lions and dolphins washed ashore on Southern California beaches, dead or sick, allegedly poisoned by a marine algae called Pseudo-nitzschia. On Long Island, in New York, more than five shellfish beds were closed due to a toxic “Red Tide” caused by another marine algae, Alexandrium, which causes paralytic shellfish poisoning. 

In Fort Myers, Florida, health advisories warned the public to steer clear of waters carpeted with a smelly scum-forming blue-green algae called cyanobacteria that can cause skin rashes, gastrointestinal issues and respiratory distress. As global temperatures warm the sea’s surface, some phytoplankton groups grow at a more rapid rate. Increased rainfall in some areas has also been linked to these growth spurts, especially when coupled with nutrient runoff from fertilizers used on farms and gardens. 

Before PACE, the ability to predict and monitor these blooms has been limited, said Tomlinson. Other satellite technologies used to study ocean color—which is largely determined by how sunlight interacts with phytoplankton and other microscopic matter in the water—can identify a general presence of the phytoplankton by identifying the common greenish pigment many of them share called chlorophyll. 

They cannot distinguish between different types of phytoplankton, however, said Tomlinson.  The only way to determine whether or not certain phytoplankton were toxic was through physical water sampling, requiring more time and resources, she said. 

PACE’s Ocean Color Instrument, however, can now distinguish between different phytoplankton groups by identifying their unique color. Each group of these organisms contains a unique pigment they use to absorb sunlight and make their own food. 

“Depending on the pigment they have, they’re going to let off wavelengths of light in different ranges,” said Tomlinson. “If one species optically looks different from the other you can start to tease them out,” she said. 

In the next few months, as PACE’s data becomes more easily accessible, Tomlinson hopes she’ll be able to give more accurate data to state agencies regulating and managing public beaches and fisheries about harmful algal blooms.  

She wants to give them enough forewarning to allow them to prepare for the blooms and mitigate harmful impacts by moving shellfish beds, using different water sources for shellfish hatcheries or treating the water with chemicals to eradicate a specific type of phytoplankton.

Air Quality 

Marcela Loría-Salazar, assistant professor of meteorology at the University of Oklahoma, is gearing up to use PACE data on aerosols to study air pollution in areas where there are fewer ground-based air quality monitors.

According to Loría-Salazar, who leads the Atmospheric Aerosols and Air Quality Laboratory (AAAQ Lab) at the University of Oklahoma, information about air quality is more available in cities than in places like Oklahoma. 

“The middle of the country doesn’t have this information” she said. “We want to use satellite data to show people there what they are being exposed to.” 

Since undergoing training offered by the PACE Early Adopter program, Loría-Salazar said she feels well prepared to take advantage of all the satellite has to offer. She will be using data produced by the Ocean Color Instrument to detect the colors of specific aerosols, which change depending on how close the airborne particles are to earth’s surface. 

“Other satellites were not able to provide that information at the magnitude that Pace will do it,” she said. 

The darker the smoke is, for example, the closer it is to the Earth, so people will have a higher likelihood of developing asthma and cardiorespiratory issues. Where smoke is whiter, or more distant, people tend to have more cardiovascular problems. 

“Therefore the color matters. It’s telling us if the smoke is fresh or the smoke has aged. And they have two different paths to human health,” she said. 

By detecting the type and location of different aerosols, as well as the concentration and source, Loría-Salazar and her team hope to engage decision makers in developing more effective exposure models and other resources to mitigate the harmful impacts of pollutants on their citizens. 

“If it’s natural [like wildfire smoke] we can create mitigation strategies,” she said. “If it’s human made we can create policy.”