麻豆淫院

In the cobalt waters off San Diego, the key to tracking a powerful greenhouse gas drifts just below the surface. Tiny ocean microbes living in oxygen-starved waters turn everyday nutrients into nitrous oxide (N鈧侽)鈥攁 compound better known as laughing gas, but far less funny for the planet.

"The gas traps roughly 300 times more heat than carbon dioxide (CO鈧�) and also eats away at Earth's ozone layer," says Xin Sun, assistant professor of biology at Penn's School of Arts & Sciences. "Having better information on where and how N鈧侽s are made can help scientists forecast global emissions more accurately as the climate changes."

Sun and her collaborators spent six weeks at sea studying the chemistry and ecology behind this process, sampling water from 40 to 120 meters deep in the Eastern Tropical North Pacific Ocean, one of the largest oxygen-depleted regions on Earth.

Their work, in Nature Communications, shows how microbial competition鈥攏ot just raw chemistry鈥攄rives the production of N鈧侽 and how even subtle shifts in oxygen or nutrients can cause sudden, dramatic jumps in greenhouse gas output.

"There's a multistep pathway that starts with nitrate (NO鈧冣伝) and turns it into nitrite (NO鈧傗伝) before finally producing N鈧侽," Sun explains. "And there's another that skips straight from nitrite to N鈧侽. You'd expect the shorter one to win, but it doesn't."

Sun likens the microbe populations to two neighboring delis that both make bagels but start with different ingredients.

The first group, starting with nitrate, is like a full-service bakery that begins with flour鈥攎ixing, fermenting, and baking everything in-house. The second group, starting from nitrite, is more like a specialty shop that depends on finding premade dough drifting through the water.

Because flour (nitrate) is far more abundant than ready-made dough (nitrite), the longer, multistep pathway turns out to be more efficient.

Low-oxygen conditions generally favor N鈧侽 production, but the team found that adding more oxygen doesn't dampen production smoothly. Instead, oxygen shakes up which microbial "shops" dominate. "Oxygen doesn't act like a dimmer switch," Sun says. "It changes who's in charge."

While feeding microbes more nutrients might seem like a good way to boost production, the teams also found it can actually push the main N鈧侽-makers out of the picture, cutting gas release to nearly zero.

By letting microbial groups compete and collaborate inside a new model, the team captured these sharp ecological fluctuations that older, chemistry-only models smoothed over.

Their findings could refine climate models that predict sea-level changes, extreme weather, and changing ocean chemistry鈥攁nd help identify which regions contribute the most greenhouse gas output.