Emerging nanotechnology has received great attention in recent years because of its widescale use in consumer products, healthcare, and medical applications, among others. Due to such rapid growth of nanomaterial manufacturing and use, these materials will inevitably be released into the environment. Currently little information exists on the fate and toxicological effects of nanoparticles in the environment including aquatic matrices. In this review, we discuss 1) possible ecological risks of silver nanomaterials as unbiodegradable and bioaccumulative contaminants, 2) environmental application of nanomaterials, 3) biological effects of nanomaterials to aquatic invertebrates and fishes, including biological fate and their indirect effects, 4) problems on nano-toxicity research, 5) regulatory science, and 6) nano-science and ecological risk. Here we highlight the need for further researches in order to understand the potential environmental/ecological hazard and risk of nanomaterials, with scientifically validated and environmentally relevant testing methods.