How does DDT as a water pollutent undergo biological magnification

DDT is added to plants where it get mixed with water and  creates water pollution  then it get to water bodies like small streams rivers etc. Here biological magnification undergo as 
                                              
 WATER(0.003 ppb ) - ZOOPLANKTORY (0.04 ppm ) - SMALL FISHES (0.5 ppm) -

BIG FISHES(2 ppm ) -FISH EATING BIRDS (25 ppm )

in this food chain the concentration of DDT powder increases from water to fish eating birds  (0.003 ppb - 25 ppm ) through biomagnification .