Question

Passage:

The Permian-Triassic extinction event, which occurred approximately 252 million years ago, represents the most severe biodiversity crisis in Earth's history, resulting in the loss of up to 96 percent of marine species and 70 percent of terrestrial vertebrate species. For decades, the dominant paradigm among paleontologists, championed by researchers such as Douglas Erwin, attributed this mass dying to a gradual process of severe environmental degradation. Erwin argued that a dramatic regression of sea levels eliminated vast swaths of shallow coastal habitats, slowly choking marine ecosystems over millions of years while simultaneously intensifying continental climates.

However, subsequent high-precision radiometric dating revealed that the extinction was remarkably abrupt, unfolding over a mere 60,000 years. This temporal compression prompted a shift toward catastrophic models. Geochemist Luann Becker proposed that, much like the later Cretaceous-Paleogene extinction, the Permian-Triassic event was triggered by a massive bolide impact. Becker cited the discovery of fullerenes—cage-like carbon molecules containing trapped extraterrestrial helium and argon isotopes—in Permian-Triassic boundary layers as definitive proof of a sudden, catastrophic collision.

Contemporaneously, a theory emphasizing endogenous terrestrial catastrophes gained widespread traction. Geologist Paul Wignall theorized that the eruption of the Siberian Traps, a colossal flood basalt province, was the primary driver. According to Wignall, the unprecedented volcanism released massive quantities of carbon dioxide and sulfur dioxide, leading to runaway greenhouse warming and severe acid rain that decimated terrestrial plant life. While compelling, the volcanism model struggled to fully account for the specific isotope excursions observed in marine carbonates.

Addressing this gap, biogeochemist Lee Kump advanced the "chemocline upward excursion" hypothesis. Kump argued that the initial volcanic warming severely stratified the oceans, halting deep-water circulation. This stagnation allowed anaerobic green sulfur bacteria to proliferate in the deep ocean, producing toxic levels of hydrogen sulfide. As the chemocline—the boundary between oxygenated surface waters and anoxic deep waters—rose to the surface, massive upwellings of hydrogen sulfide gas erupted into the atmosphere, poisoning terrestrial life and depleting the ozone layer.

Most recently, evolutionary biologist Daniel Rothman introduced a microbial culprit. Rothman identified a horizontal gene transfer event that equipped the archaeal genus *Methanosarcina* with the ability to process acetate efficiently. This evolutionary leap enabled the microbes to consume vast amounts of organic carbon that had accumulated in the oceans. The resulting exponential microbial bloom released catastrophic volumes of methane—a potent greenhouse gas—into the atmosphere, triggering a rapid and lethal cascade of climate alterations.

Question:
Based on the explicit information in the passage, match each of the following researchers with the specific finding, mechanism, or theory they proposed to explain the Permian-Triassic extinction event.