Assessment of Available Models for Studying the Coupling of Atmospheric Inputs on Biota

The objective of this deliverable is to review and report the available models for studying the coupling of atmospheric inputs of persistent organic pollutants and their accumulation in planktonic food webs. Atmospheric inputs are known to be the main input of pollutants to open sea marine environments and also be important in coastal environments. The modelling of these interactions is important because atmospheric inputs are very dynamic and variable with time and can induce temporally high concentrations in the water column. Therefore, the models needed for studying these interactions should be dynamic (not at equilibrium or steady state) in order to be able to be able to predict the high observed environmental variability, and thus able to predict episodes were potential threshold values are obtained. Furthermore, these models should also be able to take into account the interactions between fate and impact of pollutants and trophic status, which allows studying together the two drivers considered within the Thresholds IP (nutrients and pollutants). The models reviewed here are those of the three main atmospheric deposition processes; namely dry aerosol deposition, wet deposition and diffusive exchanges. Furthermore the current knowledge of the accumulation processes and cycling of organic pollutants in phytoplankton is reviewed. There are few reports of the quantification and parameterization of accumulation and cycling of POPs in bacteria and zooplankton. Here, novel results obtained for zooplankton within the threshold IP are presented which suggest an important role of these in POP cycling. It is identified that more research is needed on the role of bacteria in the impact of POPs in aquatic food webs. One of the issues that previous models were not able to assess is the relative importance of atmospheric inputs and inputs from sediments of POPs in food webs. Sediments are known to be a source of pollutants for benthic food webs, but their influence is not clear in the pelagic zone. The 1D model developed within Thresholds allows to elucidate the relative importance of these two sources of pollutants for the first time. It is shown that the atmosphere is the main contributor for the most part of the water column, except for very shallow ecosystems. Furthermore, some of the interactions between trophic status and atmospheric inputs as provided by models are also reviewed here. The present review will allow in the next future to couple these models with toxicity models including the concepts of thresholds in order to identify whether points of no return and thresholds do happen in ecosystems due to pollutants as a driver.JRC.H.5-Rural, water and ecosystem resource