| Popis: |
The northernmost part of the Adriatic (NAd) as shallow and small when compared to the rest of the Adriatic is affected the most by global change stressors such as water column warming, changes in thermohaline conditions impacted by the Po River flows and circulation regimes of the Adriatic- Ionian Bimodal Oscillating System, BiOS. All these stressors highly impact NAd ecosystem structure and functions, including biogeochemical processes. The NAd conditions are highly variable, both in space and time. Near the Istrian coast a large anticyclonic gyre usually appears during warm part of the year, around station SJ107. Another anticyclonic gyre is typical for the area near the Po delta (station SJ108). Between these two locations dynamic conditions seem to be highly variable as well. In this work we focus on long term changes in organic matter (OM) parameters (dissolved-DOC and particulate organic carbon-POC, and its surface active fraction-SAS) which indicate changes in bioproduction degree of the selected area represented by the most eastern and the most western part of the Po River transect (SJ107, SJ101, SJ108). Special focus is on June- August interval when OM parameters reach generally their highest seasonal values. Changes in OM parameters are correlated with the Po river discharge rates, as well as BiOS, biological activity and modelled primary production. Temporal changes in the first component of PCA as representative for the entire area, is then computed. Correlations between eastern and western part of the NAd are very high regarding DOC, and POC content only in July, implying that similar forcing drive changes in both regions. Higher POC fluctuations are more expressed near the Po delta, pointing to higher primary production and/or larger DOC to POC transformations due to shifts in salinity when fresh and marine waters mix. Seasonal contribution of zooplankton to DOC pool is evaluated. |
