Killifish, grass shrimp, fiddler crabs, blue crabs, and young bluefish in contaminated estuaries differ ecologically from reference populations in relatively uncontaminated environments. All five of these species show reduced activity and feeding, but only fishes show reduced growth. In these areas, killifish are poor predators, eat much detritus, have poor predator avoidance, and are smaller and less abundant. Bluefish have reduced rates of feeding and growth. Both killifish and bluefish have altered thyroid glands and neurotransmitters, which may underlie behavioral changes. Shrimp in contaminated environments show unchanged levels of predator avoidance; compensatory energetic partitioning favors growth and reproduction despite reduced feeding. With less predation pressure, shrimp are larger and more numerous. Fiddler crabs tend to spend more time in burrows and experience reduced predation. With ample food, metal depuration through molting, and reduced population size, they grow larger. In contaminated estuaries, we've found that juvenile blue crabs are less likely to be eaten by adults; adults are impaired in prey capture but are larger, despite eating much detritus and algae. Release from top-down effects from humans—as a result of a fishery advisory—may allow crabs to live longer. It appears that differences in physiology and trophic interactions modify the effects of reduced feeding on the different species.