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

Abstract

To obtain more insight into the effects of severe forcing factors on a shallow coastal system, the elemental stoichiometry and the availability and partition of nitrogen, phosphorus and carbon in dissolved and particulate pools were assessed during events of particularly strong inputs of freshwater, high salinity anomalies, wind storms, algal blooms and elevated heterotrophic respiration processes. The research is based on data collected in the Long Term Ecological Research station of the Northern Adriatic Sea (Gulf of Trieste), from January 1999 to December 2010. During all considered events, stoichiometric ratios were higher than Redfield, due to an excess of carbon and nitrogen in relation to phosphorus. The particularly 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. Freshwater inputs and phytoplankton blooms caused a rise in the ratio between dissolved organic carbon and phosphorus, in N:P and C:P in the particulate compartment and, in the case of high freshwater only, in dissolved inorganic N:P, while the opposite was observed during events dominated by ingression of south-eastern waters and heterotrophic processes, when stoichiometric ratios decreased. Strong wind events, which are mainly due to north-easterly winds, did not seem to significantly modify the biogeochemical properties in the bottom layer.