Do organisms with higher fitness mean that they have survive to an advanced age? why or why not?

No. Having a higher fitness in biology means surviving  to reproductive age, finding a mate, and producing offspring. The more offspring an organism produces during its lifetime, the greater its biological fitness, regardless of how long the organism lives. If an organsim produces 5 offspring during their lifetime and dies at an early age, they would still be considered more fit than an organism that lived a long life and did not produce any offspring.

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.