What are the different ways in which water gets polluted? How does it affect the life forms?

(N/A) The addition of undesirable substances like fertilizers,pesticides,and poisonous substances such as mercury salts into water bodies. These can also include disease-causing organisms,such as the bacteria that cause cholera.
$(b)$ The removal of desirable substances like dissolved oxygen from the water adversely affects aquatic organisms.
$(c)$ $A$ sudden change in the temperature of water bodies is dangerous and affects the breeding of aquatic life. The eggs and larvae are particularly sensitive to these temperature changes.