Pelagic organic matter in the Adriatic Sea in relation to winter hydrographic conditions

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Abstract
The spatial distribution of chlorophyll a (Chla), paniculate organic carbon (POC) and nitrogen (PON), net zoopiankton ash-free dry weight (AFDW), dry weight (DW) and carbon and nitrogen content, in parallel with primary production, was studied during a joint Yugoslav cruise in January 1980. The results were interpreted in relation to hydrographic properties, with special emphasis on the relationship between pelagic parameters. Spatial distribution of POC, PON and net zoopiankton AFDW and C and N contents showed similarities over the major part of the Adriatic, while Chla and POC showed dissimilarities since higher Chla values were restricted to the northwestern part of the Adriatic, separated from the rest of the Adriatic by a pronounced thermal front extending south of the Istrian peninsula. High POC was found in the centre of the south Adriatic gyre and in the Jabuka Pit, the latter filled with cold water originating from the area located south of the thermal front. The areas of high POC were characterized by a higher POC recycling time than in other Adriatic regions. High Chla, POC, PON and net zooplankton AFDW and C and N contents in parallel with increased primary production were found in the southwestern part of the Adriatic off Puglia (Italy) affected by a continuous terrigenous supply of nutrients. The observed spatial distribution pattern of pelagic organic matter suggests that this distribution is mostly influenced by hydrographic conditions and that the assumption of permanent productivity zones in the Adriatic is not applicable to the winter situation.