In asteroid darkness, why did some algae survive by becoming less plant-like?

Answer: They ate small prey

They ate small prey ✓ — They ate small prey. Some surviving algal plankton were mixotrophs, able to combine photosynthesis with prey ingestion, so darkness did not make them helpless. The neat twist is that a plant-like cell can survive a failed light economy by behaving partly like a tiny predator.

They stopped dividing — Stopping division can help microbes endure stress for a while, but it cannot rebuild an ocean food web. The recovery evidence points to active feeding: prey ingestion and mixotrophy helped survivors persist and later restore primary production. Dormancy is a pause button; hunting is a bridge back to growth.

They made thicker chalk — Thicker chalk is almost the opposite of the winning move. Calcifying plankton were heavily damaged, and making carbonate structures costs energy when energy is scarce. The survivors that matter here were not simply better shell-builders; they had a second nutrition mode when sunlight failed.