Question

The term oligotrophic in lake ecosystem refers to

• A. higher nutrients in water
• B. high aquatic productivity
• C. algal blooms
• D. low nutrients and low productivity

Hint:

Oligotrophic = Clear, Deep, Low P/N, High \(O_2\).
Eutrophic = Murky, Shallow, High P/N, Low \(O_2\). Eutrophication is the process of moving from oligo to eutrophic.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Lakes are classified based on their nutrient levels and biological productivity, a characteristic known as their trophic state. "Trophic" comes from the Greek word for nourishment. The main trophic states are oligotrophic, mesotrophic, and eutrophic.

Step 2: Detailed Explanation:
- Oligotrophic (Option 4): Derived from "oligo" (few) and "trophic" (nourishment). These lakes are characterized by low nutrient concentrations (especially Nitrogen and Phosphorus). As a result, they have low biological productivity, meaning they have very little algae or aquatic plant growth. These lakes are typically very clear, with high dissolved oxygen levels even at the bottom, and are often found in mountainous or rocky regions.
- Eutrophic: The opposite state, characterized by high nutrient levels (Option 1), high productivity (Option 2), and frequent algal blooms (Option 3). These lakes are often shallow, murky, and can suffer from oxygen depletion.
- Mesotrophic: An intermediate state with moderate nutrients and productivity.
Therefore, an oligotrophic lake is a nutrient-poor, clean-water ecosystem with limited plant life.

Step 3: Final Answer:
The term oligotrophic describes water bodies with minimal nutrient availability and consequently low rates of photosynthesis and biological growth.