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Even on the ground, detecting algae type by color is not a sure bet. It takes lab testing to tell whether the skim of algae on the surface of a lake, pond or stream is harmless or potentially toxic.
From space, it can be more challenging because of water’s light absorbing qualities. Scientists from the USGS Earth Resources Observation and Science (EROS) Center are working with other USGS researchers to find more ways to use Landsat satellite data and other remotely sensed data to identify harmful algal blooms (HABs) on Earth.
The goal is to coordinate efforts across the USGS to use every resource available to warn the public of potential issues as soon as possible and to provide policy makers with information in their states. HABs can pollute drinking water sources and produce toxins that are potent enough to threaten people’s wellbeing. Recreational water bodies can be unsafe to swim in. Aquatic life and habitat conditions are also threatened when HAB levels grow too high.
Using satellite data to monitor algae isn’t new, but the USGS plans to leverage Landsat satellite data even more in its new scientific plan to study HABs.
The appeal of pairing satellite observations with traditional water testing methods is clear. Earth observation satellites like Landsat can track color changes in water bodies that indicate algal growth, helping biologists and ecologists determine when and where to concentrate their testing efforts on the ground.
“There’s a lot of value in the remotely sensed information because we can’t be in all places at all times,” said Jennifer Graham, a USGS research hydrologist at the New York Water Science Center. “One of the biggest challenges when studying harmful algal blooms in the field is they are incredibly variable in space and time, and things can change very quickly.”
The remote sensing observations have to be detailed enough and frequent enough to capture changes in color “so we can start to pin down what the biology is of these algal blooms and whether or not they may be toxic or have the potential to become toxic,” said Chris Crawford, a USGS research physical scientist at EROS.
“We define a harmful algal bloom as when you have an accumulation of algae that is extensive enough to cause some kind of harm,” said Graham.
“Excessive biomass can foul drinking water intakes and can cause real aesthetic challenges because some algae-produced compounds aren’t necessarily toxic but do cause taste and odor problems in drinking water supplies,” she said.
Crawford hopes to use Landsat satellite data to create analysis ready data (ARD)—data that has been preprocessed so that it’s easy to analyze for researchers who study HABs but don’t have a remote sensing background. “Landsat has been really focused on being a terrestrial land remote sensing system,” he said. “We really need to be thinking about the water in the same way we think about the land. My plug-in here is making HABs, water quality and inland aquatics an observational priority for the Landsat mission.”
The next Landsat mission, aptly named Landsat Next, is a trio of satellites that will have much-enhanced instruments so scientists will have even better tools to monitor HABs. “Our requirements for how we observe inland water and coastal water zones are evolving and changing,” Crawford said. “In the future, with Landsat Next coming online, I think there’s strong potential to tackle this aquatic problem with higher temporal, spatial and spectral observations.”
Landsat Next’s instruments will be designed to measure new visible light spectral bands that will help detect chlorophyll and organic material in the water, making it easier to observe HABs. The Landsat Next constellation of satellites will take a complete snapshot of Earth every 6 days at the Equator (and more frequently with an increase in latitude), compared to the current 8 day revisit rate with Landsat 8 and 9. “The improved observational frequency will provide more cloud-free imagery that will enable early warning capabilities for emerging water quality concerns for lakes, rivers and the coastal zones that affect human and ecosystem health,” Crawford said.
“Then if we can focus on linking what’s happening in the upper water column and at the surface with what’s being observed from the sky, this is sure to improve HABs modeling, which I think reflects real progress on this important and growing environmental problem.”
Graham welcomes this USGS approach, seeing its value to answer specific questions. “How many HABs did we see in New York this summer? We can look to that satellite-based information to see them all instead of just the handful that we were able to sample,” she said. “So understanding the when and the where will also help us understand the why and the how.”
Remote sensing—and Landsat specifically—is a key part of the all-hands-on-deck USGS approach toward detecting, observing, and quantifying HABs. This collective approach empowers researchers and policymakers alike, offering them the tools needed to safeguard drinking water sources and address the growing environmental challenge of HABs.
Listen to a podcast and watch our Image of the Week video to learn more about monitoring lakes and potential algal blooms.
Typically, we use Landsat data to study changes on the land—you know, Landsat. In this episode of Eyes on Earth, we learn how satellite images and pixels of water, along with actual water samples, are helpful in determining the productivity of lakes across the United States. We talk with Mendenhall Fellow and Research Geographer Dr.
Typically, we use Landsat data to study changes on the land—you know, Landsat. In this episode of Eyes on Earth, we learn how satellite images and pixels of water, along with actual water samples, are helpful in determining the productivity of lakes across the United States. We talk with Mendenhall Fellow and Research Geographer Dr.
This summer in central India, a mystery in color emerged. In the space of just days, the surface of Lonar Lake turned bright pink, then returned to green. As scientists study the cause of the event, other lakes around the world offer clues.
This summer in central India, a mystery in color emerged. In the space of just days, the surface of Lonar Lake turned bright pink, then returned to green. As scientists study the cause of the event, other lakes around the world offer clues.
Read more about USGS efforts to help monitor harmful algal blooms.
Listen to a podcast and watch our Image of the Week video to learn more about monitoring lakes and potential algal blooms.
Typically, we use Landsat data to study changes on the land—you know, Landsat. In this episode of Eyes on Earth, we learn how satellite images and pixels of water, along with actual water samples, are helpful in determining the productivity of lakes across the United States. We talk with Mendenhall Fellow and Research Geographer Dr.
Typically, we use Landsat data to study changes on the land—you know, Landsat. In this episode of Eyes on Earth, we learn how satellite images and pixels of water, along with actual water samples, are helpful in determining the productivity of lakes across the United States. We talk with Mendenhall Fellow and Research Geographer Dr.
This summer in central India, a mystery in color emerged. In the space of just days, the surface of Lonar Lake turned bright pink, then returned to green. As scientists study the cause of the event, other lakes around the world offer clues.
This summer in central India, a mystery in color emerged. In the space of just days, the surface of Lonar Lake turned bright pink, then returned to green. As scientists study the cause of the event, other lakes around the world offer clues.
Read more about USGS efforts to help monitor harmful algal blooms.
