"I am a piece of ocean left behind by the tide. I am a whole ecosystem in a rocky puddle. I am destroyed by one careless foot. What am I?"

Answer: A Rock Pool (Tide Pool). Rock pools form in coastal areas when the tide retreats, trapping seawater in rocky depressions. They contain entire miniature ecosystems — fish, crabs, anemones, sea urchins. They are fragile; a single misstep can destroy creatures that have lived there for years.