Critical knowledge gaps and relevant variables requiring consideration when performing aquatic ecotoxicity assays.

The increasing diversity and complexity of contaminants released in the environment continuously lead to new challenges when applying ecotoxicity assays. This paper comprises a review concerning exposure assessment and highlights important variables that should be taken into account when investigating aquatic media toxicity under both laboratory or field conditions. Thus, to reflect as much as possible what occurs in nature, ecotoxicity assays must carefully consider these variables in their experimental design. This includes contaminant properties, the selected bioindicators and biomarkers, the dose mode/regime, concentration vs. load, exposure to single vs. multiple contaminants and exposure of single vs. multiple species. Many of these, however, are not usually taken into account, leading to critical knowledge gaps in this area, discussed in detail herein.