Why did freshwater animals survive the asteroid impact winter better than land animals?

Answer: They fed on detritus washed into rivers and lakes

They fed on detritus washed into rivers and lakes ✓ — Correct! When sunlight was blocked after the asteroid impact, plants stopped growing on land. Land animals that relied on fresh plants or herbivores starved. But freshwater animals could eat detritus—dead leaves, carcasses, and other organic matter washed into rivers and lakes. This stored food kept the aquatic food web running for months or years, giving them a survival edge.

They lived in water that stayed warmer than the air — Wrong. While water does hold heat better than air, the key advantage wasn't temperature. Many freshwater habitats actually cooled down. The real reason is that freshwater food webs could tap into a reservoir of dead organic matter, which didn't depend on sunlight for production.

They required less oxygen to survive the impact winter — Wrong. Oxygen levels in water can drop when organic matter decays, but that would stress rather than help animals. The survival advantage came from food availability, not oxygen. In fact, some land animals could hold their breath or had efficient lungs, but they still starved.