The ocean has many different ecosystems, or communities of living organisms and their environment. Life in the ocean is more diverse and plentiful than on land. In fact, the very first life on Earth, a microscopic single-celled organism, probably started in the ocean 3.5 billion years ago. About 80% of all marine organisms live in the euphotic zone. This is the top layer of the ocean, from the water’s surface down to about 100 meters. The euphotic zone is also known as the sunlit zone. It gets enough light for plants to undergo photosynthesis, or convert the sun’s energy into food. It contains vibrant ecosystems such as coral reefs, mangroves, kelp forests, and estuaries. Food and shelter are plentiful in the euphotic zone, which is home to most ocean fish, jellyfish, sea turtles, seals, coral, starfish, and shellfish.

Why is marine life so plentiful in the euphotic zone?

A
This zone is at the very bottom of the ocean, so fish can absorb minerals from the sand.

B
This zone provides enough light, food, and shelter to support a wide variety of organisms.

C
This zone is home to all plants and animals that do not need sunlight to survive.

D
This zone is used as farmland, growing crops that fish and other sea organisms eat.