Eutrophication

Question 1

what is eutrophication?

Answer 1

Eutrophication refers to the nutrient enrichment of aquatic ecosystems, which poses serious problems for water bodies and the organisms relying on such habitats.

Question 2

causes of eutrophication

Answer 2

• Excess phosphates entering water systems from:
• Agricultural runoff.
• Detergents.
• Other sources like cutting tropical rainforests.

Question 3

impact of eutrophication on water systems

Answer 3

• Algae die and decay, depleting dissolved oxygen in the water, leading to anoxic (oxygen-free) conditions. This results in:
• Foul-smelling gases like hydrogen sulphide (H₂S) and ammonia (NH₃).
• Formation of thiol-alcohols (RSH), which contain sulfur instead of oxygen.

Question 4

how can eutrophication be toxic?

Answer 4

Ammonia can exist in two forms:
1. Unionised ammonia (NH₃): Toxic to fish, especially at high pH levels.
2. Ionised ammonia (NH₄⁺): Less toxic and present in low pH conditions.

Question 5

effects of eutrophication

Answer 5

Anoxia: Leads to fish-kills, foul-smelling odours.

Algal blooms: Uncontrolled growth of aquatic vegetation.

Increased turbidity: Reduced water clarity.

Reduced productivity: Lower fish yields due to decreased oxygen levels.

Depletion of oxygen: In deeper layers of aquatic ecosystems.

Toxic substances: Increased growth of toxic algal species.

Recreational decline: Water quality deteriorates, limiting recreational use.

Species composition changes: The biodiversity in water bodies is altered.