Effects of intense physical and biological forcing factors on CNP pools in coastal waters (Gulf of Trieste, northern Adriatic sea)

To obtain more insight into the effects of severe forcing factors on a shallow coastal system, theelemental stoichiometry and the availability and partition of nitrogen, phosphorus and carbon in dissolvedand particulate pools were assessed during events of particularly strong inputs of freshwater, highsalinity anomalies, wind storms, algal blooms and elevated heterotrophic respiration processes. Theresearch is based on data collected in the Long Term Ecological Research station of the Northern AdriaticSea (Gulf of Trieste), from January 1999 to December 2010. During all considered events, stoichiometricratios were higher than Redfield, due to an excess of carbon and nitrogen in relation to phosphorus. Theparticularly intense meteorological and biological events considered in this study altered the abundance,the relative availabilities of C, N and P and the stoichiometric ratios in different directions. Freshwaterinputs and phytoplankton blooms caused a rise in the ratio between dissolved organic carbon andphosphorus, in N:P and C:P in the particulate compartment and, in the case of high freshwater only, indissolved inorganic N:P, while the opposite was observed during events dominated by ingression ofsouth-eastern waters and heterotrophic processes, when stoichiometric ratios decreased. Strong windevents, which are mainly due to north-easterly winds, did not seem to significantly modify thebiogeochemical properties in the bottom layer.