The seasonal variability of gross primary production in the southern Baltic Sea in the course of a year for 1965–1998 (average) and the scenario for 2050 in the upper layer are presented in Figure 1. The seasonal dynamics of primary production in the upper layer at the study sites in 1965–1998 is characterized by

two peaks: a sharp one during the spring bloom (ca 12 mgC m−3 h−1 in April – GdD, ca 8 mgC m−3 h−1 in the second half of April – GtD and ca 9 mgC m−3 h−1 in late April and early May – BD) and another one at the end of summer, slightly higher than the first one in the upper layer (ca 9 and 9.5 mgC m−3 h−1 in GtD and BD respectively) (Figure 1). The increase in primary production in the scenario for 2050 as compared to 1965–1998 can be attributed to changed nutrient, temperature and radiation conditions (Dzierzbicka-Głowacka learn more 2005, Kuliński et al. 2011). Typical features of the seasonal dynamics of primary production are well reflected in the annual primary production cycles. In particular, a well developed spring bloom (April), and a somewhat less intensive but Navitoclax supplier prolonged late summer/autumn bloom (August and September)

are clearly distinguishable. The curve representing primary production integrated over the whole upper water layer exhibits a slightly less intensive spring peak in BD and GtD (Figure 1), obviously because of the limited primary production in the subsurface water layer. Time series scenarios of the state variables Phyt, Zoop, DetrP and POC are presented in Figure 2 (Gdańsk Deep, upper layer), while simulated monthly and seasonal averages for phytoplankton, zooplankton, pelagic detritus and POC in the all three areas (GdD, BoD, GtD) for 1965–1998 and 2050 are presented in Figures 3 and 4. In 1968–1998 (Figure 2), phytoplankton, zooplankton, detritus and POC increase and decrease in the upper layer of GdD; their first-spring concentration

maxima are 200 mgC m−3 for phytoplankton biomass in April, 110 mgC m−3 for zooplankton biomass in June and 360 mgC m−3 for pelagic detritus at the end of May. The POC concentration reaches a level of about 410 mgC m−3 in the upper layer from April to November. The POC concentrations in the 2050 scenario are twice those Urease characteristic of the scenario for 2010 and are 2.5 times larger than in 1965–1998. The annual cycles of POC and the contributions of phytoplankton (Phyt), zooplankton (Zoop) and detritus (DetrP) in the whole upper water layer ( Figure 2) indicate large POC concentrations in early summer resulting from the Phyt bloom and the detritus due to Phyt mortality. Zoop contributes little, if anything, to the POC pool until late June. Between July and November, zooplankton is the smallest of the three POC components. The contribution of Phyt to POC is close to that of detritus.