Atmospheric Deposition Effects onPlankton Communities in the EasternMediterranean: A MesocosmExperimental Approach

International audienceThe effects of atmospheric deposition on plankton community structure wereexamined during a mesocosm experiment using water from the Cretan Sea (EasternMediterranean), an area with a high frequency of atmospheric aerosol deposition events.The experiment was carried out under spring-summer conditions (May 2012). Themain objective was to study the changes induced from a single deposition event,on the autotrophic and heterotrophic surface microbial populations, from viruses tozooplankton. To this end, the effects of Saharan dust addition were compared to theeffects ofmixed aerosol deposition on the plankton community over 9 days. The effects ofthe dust addition seemed to propagate throughout the food-web, with changes observedin nearly all of the measured parameters up to copepods. The dust input stimulatedincreased productivity, both bacterial and primary. Picoplankton, both autotrophic andheterotrophic capitalized on the changes in nutrient availability and microzooplanktonabundance also increased due to increased availability of prey. Five days after thesimulated deposition, copepods also responded, with an increase in egg production.The results suggest that nutrients were transported up the food web through autotrophs,which were favored by the Nitrogen supplied through both treatments. Although, theeffects of individual events are generally short lived, increased deposition frequencyand magnitude of events is expected in the area, due to predicted reduction in rainfall and increase in temperature, which can lead to more persistent changes in planktoncommunity structure. Here we demonstrate how a single dust deposition event leadsto enhancement of phytoplankton and microzooplankton and can eventually, throughcopepods, transport more nutrients up the food web in the Eastern Mediterranean Sea