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Meet the plants and animals that help scientists keep an eye on the environment

Daphnia, go-to freshwater plankton (Image 1 of 7)

Daphnia are tiny crustaceans that live in ponds and lakes. Their color, size and abundance serve as indicators of environmental health. In the early 1900s, Daphnia were used for toxicological screening. Researchers are now using DNA and RNA sequencing to track how gene expression in Daphnia changes over time. The results help them predict the toxicity of chemicals to other species.

Herring gulls, a warning system for global pollutants (Image 2 of 7)

The eggs of herring gulls have provided data on pollutants in the Great Lakes region of the U.S. and Canada since the 1970s. Scientists also monitor Arctic-breeding seabirds such as thick-billed murres and northern fulmars. The number one finding from bird studies is that concentrations of contaminants such as DDT, PCBs and dioxins have declined as a result of regulations.

Mussels, coastal pollution watchdogs (Image 3 of 7)

Mussels, oysters and clams are ideal for pollution monitoring because they are common and easy to collect. In addition, they tend to concentrate pollutants from the surrounding seawater, making detection easier. Mussel watch programs are used globally to identify the sources and distribution of chemical pollutants and to assess human health risks.

Trout, monitors of the Great Lakes (Image 4 of 7)

Lake trout occupy the top of the food web, live long, grow big and have high body fat — all characteristics that make them perfect for biomonitoring. Canadian-U.S. monitoring of lake trout in the Great Lakes since the 1970s has tracked changes in the concentrations of legacy pollutants and emerging pollutants of concern.

Lichens, indicators of air quality (Image 5 of 7)

Lichens are composite organisms assembled from fungi and algae or cyanobacteria. They readily absorb contaminants and are good sentinels for air quality. They are sensitive to sulfur dioxide, ammonia and nitrates, and they accumulate metals such as mercury from power plants and lead and zinc from ore smelters.

Caribou, Arctic environmental rangers (Image 6 of 7)

Caribou are favored as sentinels for their large size and extensive migrations near the top of the world. They provide some of the longest data sets for radioactive contaminants from nuclear weapons testing. Monitoring radioisotopes in caribou took on additional significance after the Chernobyl reactor accident in in 1986 and the Fukushima reactor accident in 2011.

Honeybees, poster insects for pollinators (Image 7 of 7)

Honeybees qualify as valuable sentinels by virtue of contaminants that show up in the honey they produce. A recent study of nearly 200 honey samples from around the world found traces of neonicotinoid pesticides in 75 percent of the samples. About one-third of the samples had high enough concentrations to harm bees.


Editor’s note: This photo gallery is an edited version of the article “Meet the Sentinels,” which appeared in the November 20, 2017, edition of Chemical & Engineering News. Please see the original article for more in-depth descriptions of the remarkable role these creatures play in helping to protect the planet.

In the movie “Arrival,” a team of scientists takes along a canary in a cage when visiting an alien spaceship. The purpose of the canary is never disclosed, but one assumes it serves as a sentinel — as the bird once did in coal mines — to alert the team if environmental conditions in the spaceship turn unfavorable.

Scientists have identified dozens of animals and plants that can function as sentinel species — harbingers of danger to human health and the environment. They have used sentinels to track persistent organic pollutants, to check for toxic metals, and to look at changes in nitrogen and phosphorus nutrients as well as dietary shifts that could be the result of climate change or invasive species.

Sentinel species aren’t a replacement for other types of sampling or lab research. However, they go further by providing physical evidence of how pollutants are damaging ecological systems.

New technologies are changing how scientists monitor sentinel species. For example, researchers are now using microsensors fitted to the backs of honeybees to analyze their ability to pollinate. Others are using drones to snatch snot samples from the blowholes of whales at sea to evaluate their well-being.

Click through the photos above to learn about a few key sentinel species and how they are helping us monitor the health of our environment. View Ensia homepage

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