Catalano¹, Giulio, Giorgio Budillon², Rosabruna La Ferla³, Paolo Povero⁴, Mariangela Ravaioli⁵, Vincenzo Saggiomo⁶, Alessandra Accornero², Maurizio Azzaro³, Gian Carlo Carrada⁷, Federico Giglio⁵, Leonardo Langone⁵, Olga Mangoni⁷, Cristina Misic⁴ and Monica Modigh⁶

¹CNR - Istituto Talassografico, ISMAR - Office of Trieste, Viale Gessi, 2, 34123 Trieste, Italy, E-mail: giulio.catalano@itt.ts.cnr.it, ²Institute of Oceanography and Meteorology, University "Parthenope", 80127 Napoli, Italy, ³CNR - Istituto Sperimentale Talassografico, IAMC - Office of Messina, 98122 Messina, Italy, ⁴Dept. for Territory and its Resources, University of Genova, 16132 Genova, Italy, ⁵CNR - Institute of Marine Geology, ISMAR - Office of Bologna, 40129 Bologna, Italy, ⁶Stazione Zoologica "A. Dohrn", 80121 Napoli, Italy and ⁷Dept. of Zoology, University "Federico II", 80134 Napoli, Italy

A global budget of carbon and nitrogen in the Ross Sea (Southern Ocean)

The present work attempts to provide a global budget of carbon and nitrogen in the Ross Sea on the basis of vertical fluxes from the upper productive layer to the sediments and cross slope horizontal transfer to the open ocean over a period lasting from late spring (November) to summer (February). To this end, a large data set combining results from ten Italian oceanographic cruises as well as from the literature was utilized. The deep layer, the most relevant for the continental shelf pump, releases carbon to the open ocean in the form of DIC, DOC and POC. As to particulate organic nitrogen, less than 1 Gmol is released to the deep ocean, but the nitrogen balance becomes strongly positive considering the 19 Gmol imported from the open ocean. Our estimates indicate that during an average austral summer, the amount of matter recycled through biological and sedimentary processes within the Ross Sea is almost one order of magnitude higher than the amount exchanged with the open ocean. Within the upper layer, 3486 and 523 Gmol of carbon and nitrogen, respectively, are incorporated into biomass, of which about 50% are later exported to the deep layer. Since the burial is negligible (less than 0.5%), considering the upper and deep layer together, we estimate that about 3155 Gmol of carbon and 473 Gmol of nitrogen are channelled to the higher trophic levels and to the dissolved organic pool. In this context, grazing appears as a relevant mechanism of export.