Biomagnification is the term used to describe the increase in the concentration of a toxic substance or chemical in the tissues of organisms. The levels of biomagnification tend to increase in the higher levels of the food chain.
For example: Heavy metals, toxic chemicals, wastes from humans, animals, etc., when discharged into the sea and oceans, tend to affect the marine organisms causing diseases, genetic defects, and many behavioral changes.
However, the severity of the damage varies in between the different species, with the animals at the top of the marine food chain being affected the most.
From the given options, copepods (a group of crustaceans) are probably the least affected in the biomagnification process, since they are at the bottom of the food chain.