The present disclosure provides methods for determining the toxicity of fresh-water and marine sediments and sediment pore water containing indigenous or introduced toxicants from each as a one-time analysis and/or for analysis over a period of time. The present disclosure further provides kits assembled for the afore-mentioned determination. The methods and kits of the present disclosure can be used for analyzing sediment and pore water samples from, among other locations, all environments where species having a dormant life stage may exist including, for example, natural zooplankton.