Write in brief about the harmful effects of water pollution.

(N/A) The harmful effects of water pollution are:
$(i)$ Addition of undesirable substances such as fertilizers,pesticides,and mercury salts used in paper industries. This results in changes to both the physical and chemical characteristics of water.
$(ii)$ Polluted water may contain disease-causing harmful bacteria such as those causing cholera,typhoid,etc.
$(iii)$ The reduction of dissolved oxygen levels adversely affects aquatic organisms.
$(iv)$ Any change in water temperature affects the breeding patterns of aquatic organisms.
$(v)$ The eggs and larvae of various aquatic animals are particularly susceptible to temperature changes.