Energy dispersive x-ray spectroscopy (EDS) is a method for analyzing the elemental (chemical) composition of synthetic and natural structures, and has been useful in identifying trace metals in forensics and ecotoxicology. To date, it has never been applied to detect trace elements in invertebrate secretions. Here, I describe a study that uses EDS to characterize the protective secretions of sessile rotifers and to determine if metal pollutants are incorporated into their secretions.