Biochemical controls: chemical control of ecosystems (Introduction)

by David Turell , Wednesday, March 05, 2025, 19:30 (13 hours, 46 minutes ago) @ David Turell

They are called keystone chemicals:

https://www.quantamagazine.org/a-new-chemical-view-of-ecosystems-20250305/

"The biological world is awash in chemical signals. Ants lead their nest mates to food with winding trails of pheromones, plants exude aerosols to warn their neighbors of herbivores, and everything you experience as “smell” is a molecule latching onto your nose. Some molecular messages find their targets; most linger unread in the environment. But sometimes, other species — chemical eavesdroppers, bystanders or visitors — can pick up and interpret the signals in their own way. If the message is powerful enough, the impact can ripple out across an ecosystem.

"In 2007, biologists named these potent molecules after a popular concept in ecology. “Keystone species,” such as starfish in Pacific Northwest tidepools, aren’t abundant, but they have outsize effects on the food web — making those species as crucial to their ecosystems as a load-bearing keystone in an archway. If they’re removed, the idea goes, the entire ecosystem could collapse into a different form. “Keystone molecules,” then, are rare chemicals that can structure, shape and alter connections between species across entire ecosystems.

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"Now, a comprehensive study published in Science Advances has combined field work, chemical analysis and community ecology to lend fresh support to the keystone molecule theory(opens a new tab). Researchers studying pungent Alderia sea slugs in a California mudflat isolated molecules new to science from their unappetizing slime. As the scientists studied this cocktail and later introduced it to the mudflat, they recorded profound effects on other species and on the overall nature of the habitat.

“'One small, simple molecule can be tying together these seemingly unrelated species and whole ecosystem processes,” said study author Patrick Krug(opens a new tab), a marine biologist at California State University, Los Angeles. “It is now being recognized as this general phenomenon that we’ve just been kind of oblivious to.”

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"In a 2013 paper, they identified four outstanding examples(opens a new tab): tetrodotoxin, a neurotoxin produced by many animals including the newts, pufferfish and octopuses; saxitoxin, which is made by algae and makes shellfish toxic to predators; pyrrolizidine alkaloids, a widespread plant-produced poison that deters herbivores and attracts insects; and dimethylsulfoniopropionate (DMSP), a sulfur-rich compound produced by marine algae.

"Across many ecosystems, these chemicals have widespread effects. DMSP, for example, is the ocean’s dinner bell: When the algae are eaten by krill and fish, the chemical leaches into the water and can form gas plumes over the ocean. Seabirds smell the plume from miles away. They follow it to feast on fish and then fly back to their nests, where they deposit excrement laden with nutrients that fuel plant growth on land.

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"We are intuitively familiar with the power of chemical signals. The smell of baking bread or stinking garbage can completely alter our behavior. In the case of Alderia sea slugs, their chemistry overwhelms the local food web. (my bold)
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"Krug’s experiment confirmed that when alderenes seep into the mud, they restructure the entire community. They drive species out. They affect the quality and content of the soil. They’re used as a reproductive defense by an unrelated species; they’ve even compelled an organism from a different animal phylum to evolve into a slug mimic. The rare chemical has become the main structural element within the mudflat ecosystem — like a keystone in an archway.

“'You have a single slug species making some pretty straightforward little chemical defenses, and it’s changing who’s there and who’s not there,” said Kubanek, who was not involved in the research. “The slug goo is having a really big effect on the whole ecosystem.'”

Comment: animals and plants speak to each other in chemical signals, which create automatic responses as my bold insists. That some key molecules shape ecosystems is an amazing but a logical discovery.