As DDT moves up the trophic levels in food chains or webs, does its concentration increase or decrease?
DDT increases as it moves up a food chain.
DDT increases or biomagnifies if we look at a food chain. DDT is fat-soluble, meaning animals store it in fatty tissues. It also takes a relatively long amount of time to break down.
Thus, if a predator consumes multiple organisms and each organism has a small amount of DDT, the amount of DDT in the predator is going to be the result of all of those small amounts combined.
In the image below, we see that the concentration of DDT in large fish is 2ppm (parts per million) but the fish-eating bird has a concentration of 25ppm.
To learn more about DDT and biomagnification, check out this link.