Zingster Stream and boddens
In contrast to the Kleine Breite (Schlei), at Zingster Stream (sampling
point E), the salinity values exhibited a more pronounced seasonal
trend, with lower δ-values in winter/spring and higher values in summers
(Fig. 4). This is a common pattern in Baltic Sea lagoons and related to
the seasonal discharge pattern of inflowing rivers (Cyberski,
Wróblewski, & Stewart, 2000) (Fig. 4). Short-term salinity fluctuations
on the other hand can be explained by influence of different water
masses from either the eastern or western side of the Zingster Stream,
which is controlled by wind direction and water level differences
(Schumann et al., 2006). The water isotope values mirror the seasonal
salinity trend throughout the studied time period
(24th March 2020 – 9th March 2021;
Fig. 4), i.e. show lower values in winter/spring and higher in summers
(Fig. 4). Comparable to the Schlei, the correlations between water
isotopes and water / air temperature, as well as
O2-saturation cannot rule out effects of these
parameters onto δ-values. This is especially true for lower temperatures
in the colder winter (2020/21) compared to the mild winter (2019/20),
which could explain the lower δ-values in Jan-March 2021.
A similar seasonal trend in water isotopes as in Zingster Stream is
discovered at all sampling locations at the DZBC, i.e. from the inflow
of the Recknitz (sampling point B) to the outflow from the boddens
towards the Baltic Sea (sampling point H) (Fig. 5). The decreasing
influence of freshwater inflow along this transect is clearly visible at
increasing salinities, despite the actual seasonal salinity trends are
different in the outer boddens (F, G, H) compared to the innermost
boddens (B, C) (Fig. 5a). Close to the outflow towards the Baltic Sea
(point H), high salinities up to 14 psu were observed in February 2020
and March 2021. Those areas are more susceptible to salinity changes of
the Baltic Sea, which in turn are influenced by salt water intrusion
events from the North Sea, via the Little Belt, Great Belt and Øresund
(Volker Mohrholz, 2018) (Fig. 1). Especially in February 2020 large
amounts of salt water was driven by two major storms into the Baltic Sea
(V. Mohrholz, 2018) (Fig. 3).