
Changes in Si delivery to coastal systems, caused by human activities (e.g. reservoir construction, agricultural development, de-forestation, and urbanization) can cause shifts in phytoplankton community structure, with impacts through the whole aquatic food web. Although nutrient exports to surface waters have been altered permanently by human activities, the extent and potential impact on Si, N, and P ratios and human activities are rarely evaluated simultaneously in one basin. By using data from fieldwork and long monitoring datasets from International Protection of the Danube River (ICPDR) I assessed the effects of natural and human controlling factors on nutrient loads and stoichiometry for N, P, Si in the Danube River and its tributaries.