Intrusion of high-salinity water causes accumulation of transparent exopolymer particles (TEP) in the northern Adriatic Sea

Abstract

We present evidence that transparent exopolymer particles (TEP) accumulate in the northern Adriatic Sea as a result of the intrusion of oligotrophic high-salinity water (OHSW) from the south during summer. Samples were collected in June and July of 2007 in haloclines, and in the layers above and below them, at 2 stations in the region of the highest influx of OHSW. In June, we observed that concentrations of TEP in the upper part of the water column were 10 times higher at the eastern station as compared to the western station. This coincided with an intrusion of OHSW at the eastern station while the western station remained unaffected. In July, 2 stronger events involving OHSW encompassed both stations, leading to significant accumulations of TEP in the haloclines and in the layers above. Furthermore, during the period of maximal TEP accumulation, we noted pronounced increases in the abundance of diatoms and in bacterial numbers. These increases coincided with low cell-specific production of bacterial biomass, and a low abundance of actively respiring (CTC+) bacteria. In contrast, during the period of lower TEP concentration in the halocline, we observed an increase in the abundance of CTC+ bacteria, and in cell-specific β-glucosidase activity, probably indicating enhanced degradation of TEP in this layer. © Inter-Research 2011.