Which of the following is NOT a freshwater aquatic ecosystem?

• A. Lake
• B. Estuary
• C. Pond
• D. River

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the definition of a freshwater aquatic ecosystem. These ecosystems contain water with low concentrations of dissolved salts, typically less than 1%. Examples include lakes, ponds, and rivers.
2. Step 2: Identify the characteristics of each option: Lakes, ponds, and rivers are all freshwater ecosystems because they contain primarily fresh water.
3. Step 3: Define an estuary. An estuary is a coastal area where freshwater from rivers meets and mixes with saltwater from the ocean, resulting in brackish water (a mix of fresh and saltwater).
4. Step 4: Recognize that because estuaries contain a mixture of saltwater and freshwater, they are not classified as purely freshwater aquatic ecosystems.
5. Step 5: Conclude that among the options given, the estuary is NOT a freshwater aquatic ecosystem.