2. Study area
The northeastern German coast of the Baltic Sea is basically a flooded
glacial moraine landscape. It is characterized by extensive bays,
shallow lagoons (the boddens) and marine inlets, which form the mixing
zone between rivers and the marine realm (Correns, 1977; Schwarzer,
Ricklefs, Bartholomä, & Zeiler, 2008). These zones are characterized by
hydrologic events which in turn affect biochemical characteristics of
the ecosystem. For example they react sensitively both to discharge
pulses from rivers and inflow events from the marine side after storms
(Gocke, Rheinheimer, & Schramm, 2003). Further, a dense net of water
management structures, such as water retention flaps, partially
attenuate freshwater flow from creeks into the lagoons. Here, automatic
ones will release water from creeks when the lagoons are low while some
manual flaps exist, which are operated by hand (Funkel, 2004) .
For this study, water samples were taken along three transects,
encompassing salinity gradients (Figs. 1 and 2; Supplementary Tables S1
and S2):