Biota are important bioindicators because they reflect the potential harm of emissions and releases of mercury to air, water and land. Because there are not suitable models to predict the methylation process and the entry of methylmercury into the food web, high trophic level biota is recommended (i.e., trophic level 4 or higher). High trophic level biota can therefore be used to identify spatial gradients, including ecosystem sensitivity spots, and to track changes over time. The technical report compiled and synthesized information available through the “Global Biotic Mercury Synthesis” or GBMS, this database on mercury in biota and identified information and data gaps, comparability, options for filling gaps, available modelling capabilities to assess changes, baselines, and proposed monitoring approaches with an estimated budget.