Q1. What is the primary cause of eutrophication in aquatic ecosystems?
- Excessive input of nutrients like nitrogen and phosphorus
- Decrease in water temperature
- Increased sedimentation
- Overgrazing near water bodies
Correct Option: 1. Excessive input of nutrients like nitrogen and phosphorus
Explanation: Eutrophication occurs when water bodies receive excess nutrients (mainly nitrogen and phosphorus), often from agricultural runoff, sewage, or industrial discharge. These nutrients promote excessive algal growth, which disrupts the aquatic ecosystem.
Q2. Which of the following is NOT an effect of eutrophication?
- Decreased oxygen levels in water
- Increased biodiversity
- Algal blooms
- Death of aquatic organisms
Correct Option: 2. Increased biodiversity
Explanation: Eutrophication leads to oxygen depletion and habitat degradation, which decreases biodiversity by creating unfavorable conditions for many species. Sensitive species die off, and only tolerant or invasive species may thrive.
Q3. What term is used to describe rapid growth of algae due to favorable conditions like nutrient enrichment and warm water?
- Coral bleaching
- Algal bloom
- Bioremediation
- Water logging
Correct Option: 2. Algal bloom
Explanation: An algal bloom refers to a rapid increase in the population of algae in a water system. It is often caused by nutrient enrichment and warm temperatures.
Q4. Why is the term “Red Tide” considered a misnomer for harmful algal blooms?
- They always occur during low tides
- They are always red in color
- They are not caused by tides and may not be red
- They only affect terrestrial ecosystems
Correct Option: 3. They are not caused by tides and may not be red
Explanation: “Red Tide” is misleading because harmful algal blooms (HABs) are not related to tides and the water may appear red, green, brown, or even colorless depending on the algal species and concentration.
Q5. Which of the following is a method for removing nutrients from lakes?
- Introducing invasive species
- Fertilizer application
- Flushing with nutrient-rich water
- Deep water abstraction
Correct Option: 4. Deep water abstraction
Explanation: Deep water abstraction involves removing nutrient-rich deep water from lakes to reduce internal nutrient recycling and minimize algal blooms.