A water quality model as tool for the evaluation of the limiting nutrient

Eutrophication is one of the major environmental problem that affect water bodies in general and especially coastal zones: the high nutrient loads emitted by the different anthropic activities are usually discharged by the river system in these areas. The identification of the limiting nutrient plays a key role in the study of eutrophication process: this permits to predict algal group that could easily grow in the ecosystem, to focus the management efforts on the most sensitive nutrient… Usually a very simple method is used to evaluate the limiting nutrient: the N:P ratio is calculated starting from data coming from monitoring program and then compared with the Refield ratio. The different methodologies for the estimation of the limiting nutrient have been applied on the coastal zone affected by the Po river discharge. This area, defined by means of a statistical analysis of salinity, is part of the Northern Adriatic sea. It is evident the different methodologies give different results and that the difference is not Trascurabile.