Detecting natural and anthropogenic trends of Po River loads in the North Adriatic: the importance of data mining and time series analysis

The load of freshwater and chemical compounds by the rivers have a pivotal role on most of physical, chemical, biological and geological characteristics of N Adriatic ecosystem, being this area a shallow continental shelf receiving one of the largest runoff of Mediterranean. In particular, Po River constitutes the most important source of freshwater, organic and suspended matter and nutrients in this region, with averaged discharges of 45 km3/y of freshwater, 164 kt-N/y of TN, 8 kt-P/y of TP, 140 kt-Si/y of SiO2, 205 kt-C/y of TOC and 3920 kt/y of TSM, during the recent period 1995-2012. During the last decade, a growing number of scientific studies has pointed out the importance of the oscillations of river loads as a factor regulating the long term evolution of productivity and of eutrophication problems and dystrophic events in this marine region. This finding has made outdated the view of river inputs as a stationary (i.e. climatological) component of this marine ecosystem. These oscillations originate by a complex interaction between natural trends, mainly induced by the climate, and development of human activities and they act over temporal scales from seasons to millennia. However, the oscillations of river loads in the Adriatic are not yet adequately analyzed, even in the last century, due to the difficulty of data mining, the incompleteness of time series and the dispersion of the competences on monitoring activities among different institutions. The aim of this study is to provide an updated analysis of Po river load in the Adriatic, in order to better highlight its oscillations and effects in the marine ecosystem. River water flows in 1917-2012 and nutrient concentration in freshwater in 1988-2012 were reanalyzed, paying a special attention on the past and present problems that affect these data series and limit their utilization for the environmental research.