Question

After eutrophication a lake becomes

• A. Dystrophic
• B. Bog
• C. Reservoir
• D. Oligotrophic

Hint:

Lake Succession Stages: Oligotrophic (Young/Nutrient-poor) $\rightarrow$ Mesotrophic $\rightarrow$ Eutrophic (Nutrient-rich) $\rightarrow$ DYSTROPHIC BOG (Senescent/Organic-rich).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Limnological trophic lake succession and ontogeny: hyper-eutrophication accelerates organic matter accumulation, humic acid loading, and oxygen exhaustion, evolving into a dystrophic brown-water senescent stage.
Key Formula or Approach:
\[ \text{Lake Trophic Ontogeny: Oligotrophic (Pristine)} \rightarrow \text{Mesotrophic} \rightarrow \text{Eutrophic (High N, P)} \xrightarrow{\text{Hyper-enrichment / Senescence}} \mathbf{Dystrophic / Bog} \]

Step 2: Detailed Explanation:
In lake ontogeny, limnology, and trophic classification:
- Lakes naturally undergo ecological succession over geological timescales (accelerated by anthropogenic nutrient pollution):
1. Oligotrophic: Deep, clear, nutrient-poor, high dissolved oxygen.
2. Eutrophic: Nutrient-rich (high N and P), dense algal blooms, shallowing depth.
3. Dystrophic (A) Senescent Bog: Advanced terminal stage resulting from extreme post-eutrophication succession. Characterized by massive accumulation of undecomposed organic detritus, high humic acid content (brown-stained bog water), low pH ($< 5.5$), severe hypolimnetic oxygen deficits, and reduced biological biodiversity before transforming into a wetland bog.

Step 3: Final Answer:
Hence, after eutrophication a lake becomes Dystrophic, matching option (A).