Nutrient release from sediments and the role of bioturbation in the Goro Lagoon (Italy)

The nutrients released from the sea bottom through resuspension or diffusion may play an important role in determining the trophic state of aquatic environments. As well as quantifying the nutrients, it is important to recognize the factors and mechanisms which mostly affect their release and determine their extent. Direct measurements of NH3, PO4 and SiO2 fluxes were made by means of benthic chambers in the Sacca di Goro (a lagoon within the Po River Delta), as an obvious consequence of previous investigations into the processes of nutrient regeneration and release from the sea bottom in the coastal areas facing the Po River Delta. The role that macrobenthic organisms play through bioturbation and irrigation was investigated by determining and quantifying the species in the sediments below each benthic chamber. The results showed the following: (a) generally high fluxes with significant differences between day and night hours; (b) the importance of macrobenthos and the structures that it builds in sediments; (c) limited differences between the two areas examined (North-Central area and Valle di Gorino -- the eastern part of the Goro lagoon) which, however, differ considerably in terms of sedimentology and hydrology.