Which one of the following conditions is not suitable for the growth of coral-reefs ?

Question

Accepted Answer

Sedimented water is not suitable for the growth of coral reefs because:

*   **Sediment smothers corals:** High levels of sediment in the water column reduce light penetration, which is essential for the symbiotic algae (zooxanthellae) living within coral tissues. These algae provide the coral with the majority of its energy through photosynthesis. Reduced light hinders photosynthesis, starving the coral.
*   **Sediment clogs feeding structures:** Sediment can also clog the feeding structures of corals, making it difficult for them to capture food particles from the water.
*   **Sediment abrasion:** Suspended sediment can physically abrade and damage coral tissues.
*   **Increased turbidity:** Sediment increases water turbidity, further reducing light penetration and hindering coral growth.

Now, let's explain why the other options are incorrect:

*   **Option 1: Clean and shallow water:** Clean and shallow water *is* suitable for coral reef growth. Shallow water allows for sufficient sunlight penetration, and clean water ensures that the corals are not smothered by sediment or pollutants.
*   **Option 3: Salinity between 27‰ to 30‰:** This salinity range *is* suitable for coral reef growth. Corals thrive in relatively stable salinity levels, and this range falls within the optimal range for many coral species.
*   **Option 4: Oceanic currents:** Oceanic currents *are* important for coral reef growth. They bring in nutrients and oxygen, remove waste products, and help disperse coral larvae.