What term describes the behavior of an animal which warns others that a predator is approaching?

Communication signal

Animals send communication signals not only in their species but also in other species to warn each other against a predator. Usually animals uses following signals to communicate

a)Visual – these are  of two types namely badges and dispaly

b)Auditory/sound base – This includes barking, growling, purring etc.

c)Chemical (release of any chemical)  

d)Tactile ( touch based)  

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.