Explanation:

- Freshwater Ecosystem: The benthic zone is present at the bottom of lakes, rivers, and streams. It's home to various organisms like algae, insects, and some fish.

- Saltwater Ecosystem: The benthic zone exists in the ocean's depths. It hosts a wide array of life forms such as coral reefs, fish, and sea beds.

- Tundra Ecosystem: Primarily known for its cold climate and frozen soil, it doesn’t have a typical benthic zone like aquatic ecosystems.

- Forest Ecosystem: Generally, it is land-based and doesn't have a benthic zone like in aquatic systems.

Salt water ecosystem is indeed correct. The benthic zone is found here, as it refers to the ocean floor.