Darkness and Body Size Shaped End-Cretaceous Marine Extinction Patterns

Why It Matters

The findings provide a mechanistic link between impact‑winter conditions and selective marine extinction, improving our ability to model past biodiversity crises and anticipate how modern climate stressors might affect ocean ecosystems.

Key Takeaways

• Impact winter darkness drove 78% plankton functional type loss.
• Extinction thresholds scaled with body size; larger plankton vanished.
• Small (<2.5 µm) plankton survived, especially at high latitudes.
• Solar radiation reduction, not CO₂, primary extinction driver in model.
• Model aligns with fossil record, supporting trait‑based extinction framework.

Pulse Analysis

The end‑Cretaceous mass extinction has long been attributed to the Chicxulub impact, yet the precise pathways that led to the dramatic loss of marine life remained debated. Traditional explanations focused on ocean acidification or temperature spikes, but recent proxy data suggest a more nuanced picture. By integrating a trait‑based ecosystem model with realistic post‑impact forcings—dust‑laden darkness, a CO₂ pulse, and nutrient influx—researchers have recreated the rapid collapse of plankton diversity observed in the fossil record, offering a fresh perspective that bridges geological evidence with modern ecological theory.

EcoGENIE’s simulations reveal that the abrupt reduction in solar radiation—often called an "impact winter"—was the primary catalyst for extinction. The darkness curtailed photosynthetic energy, deepened the mixed layer, and altered nutrient dynamics, leading to a 99.5% drop in global primary production. Crucially, the model incorporates body‑size‑dependent biomass thresholds, showing that larger plankton required more energy and therefore crossed extinction limits faster than their smaller counterparts. This dual mechanism explains why tiny mixotrophs and high‑latitude nanoplankton persisted while larger foraminifera and zooplankton vanished, aligning closely with paleontological patterns across latitudes.

Beyond reconstructing a historic event, the study reshapes how scientists view mass‑extinction dynamics. It underscores the importance of energy availability and organismal traits in determining survival, concepts that are directly applicable to contemporary ocean stressors such as reduced light penetration from increased turbidity or shifting nutrient regimes. Incorporating size‑based extinction thresholds into Earth system models could enhance predictions of ecosystem responses to rapid climate change, making this research a valuable template for future interdisciplinary investigations.