Stanford Researchers Identify Metabolic Trap That Caused Permian Extinction

While the event was catastrophic, the researchers found that survival was not random; it was dictated by the metabolic ability of organisms to tolerate rising temperatures and declining oxygen levels in the ocean.

The Volcanic Trigger and Ocean Deoxygenation

The Great Dying was precipitated by massive volcanic eruptions in Siberia, which released gargantuan amounts of carbon dioxide and methane into the atmosphere. This release transformed Earth into a greenhouse-gas planet, causing global temperatures to climb. As the oceans warmed, they lost approximately 80% of their oxygen. Research indicates that half of the seafloor, particularly at greater depths, became completely devoid of oxygen.

For animals accustomed to the relatively cool, well-oxygenated oceans that characterized the Paleozoic period, these rapid environmental changes created an insurmountable physiological challenge. While tropical organisms were already somewhat adapted to warmer, lower-oxygen conditions, those inhabiting cold, oxygen-rich waters found themselves unable to cope with the changing chemistry.

The Metabolic Trap: Why Brachiopods Perished

Before the extinction, seafloors were dominated by slow-metabolizing, bottom-dwelling, largely immobile filter feeders. These included brachiopods—which resembled clams but were anatomically distinct—and crinoids, or sea lilies. These groups had thrived for approximately 280 million years.

However, as ocean temperatures rose, the oxygen demands of these organisms increased. Because their bodies were not adapted to transport oxygen efficiently under these new conditions, they could not keep pace with the rising demand.

Survival of the Faster Metabolisms

In contrast to the Paleozoic fauna, other animal groups fared significantly better. Approximately half of the mollusks, such as clams and snails, survived the extinction, alongside fish and echinoderms like starfish and sea urchins.

The researchers discovered that these survivors possessed faster metabolisms and body plans better suited for the harsh new environment. Modern marine animals like bivalves, gastropods, and fish generally possess features such as gills, more efficient blood flow, and larger, more muscular bodies. Although these traits require more energy under normal circumstances, they allowed these animals to better supply oxygen to their tissues as temperatures climbed and oxygen levels dropped.

Our findings show that, across different organism groups, extinctions happened at much higher rates for those more vulnerable to increases in water temperature and decreases in oxygen availability, said lead study author Jose Andres Marquez, a former PhD student in the lab of Erik Anders Sperling at Stanford.

Methodology and Future Implications

To reach these conclusions, the team developed a model based on the metabolic oxygen balance of various species. They tested this model using direct physiological measurements from living relatives of ancient groups, including brachiopods collected from the San Juan Islands in Washington. This approach addressed limitations in previous research, which had relied primarily on data from modern, commercially important species.

The researchers noted that the conditions preceding the Great Dying—a relatively cool, well-oxygenated ocean subjected to a massive injection of carbon dioxide—bear a resemblance to the climate of recent history, which is being altered by the burning of fossil fuels. By understanding how Earth’s biota responded to these stressors 252 million years ago, scientists hope to gain better insight into the vulnerabilities of modern marine life in the face of ongoing climate change.

Sources: A Z Animals, Thedebrief.