How you know that paraquat did not cause the coral bleaching

Answer: Coral bleaching is mostly cause by temperature changes in water, light or nutrients. It cannot be caused by paraquat.

Explanation:

Coral bleaching occur when Coral expel symbiotic algae living in their tissues. Coral bleaching is caused when there is changes in temperature, light and nutrients requirement for Coral survival. These can lead to reduced reproductive capacity, reduced growth rate and increase mortality rates.