K-Pg shelled plankton died off in days. Why does darkness explain it better than acid dissolving shells?

Answer: Sunlight loss kills food base

Sunlight loss kills food base ✓ — Right — losing sunlight is the cleaner fit. After the K-Pg impact, dust and aerosols blocked light for months, halting photosynthesis at the base of the marine food web. Calcifying plankton starved within weeks. Acidification did happen but unfolded over years and would have spared deep-sea calcifiers — yet those died too, pointing to darkness, not chemistry, as the prompt cause.

Acid instantly melts all shells — Acid instantly melting shells overstates the chemistry. Even severe acidification thins shells over years to centuries, not days. The K-Pg record shows plankton vanishing in weeks — too fast for dissolution to be the lead actor; the kinetics don't fit.

Acid affects only reef builders — Acid affecting only reef builders is true today but wrong for this event. Reef corals did suffer, but so did open-ocean coccolithophores, foraminifera, and even some deep-sea calcifiers — a global pattern that maps to darkness, not shallow-water chemistry alone.