Moses Sternfahrt-9, Chemical transformation of chlorophyll-a and dissolved organic matter along the Elbe to the North Sea (German Bight) in 2022

As the previous cruises were mainly conducted in August / September, this cruise was set up to cover a late spring situation in the German Bight. The cruise track and positions of the stations were similar to Sternfahrt_5 in September 2020, thus covering a wide range from 7.6°E to 8.9°E and from 53.5°N to 54.8°N. Continuous sampling for Chlorophyll-a and dissolved organic matter from the Elbe, Tide-Elbe and North Sea and subsequent detailed analysis at the UFZ will give new insights on the chemical transformations of these compounds. The southern North Sea (German Bight) is influenced by the water flowing into the Tide-Elbe area and how it is further modified. For a better understanding of the different branches of relevant events it is necessary to investigate the main impacting factors for the terrestrial and coastal water quality. Therefore, during different cruises between 2019 and 2022 a group of parameters was continuously traced from the Elbe River basin (Czech/German border) to Tide-Elbe and Elbe estuary (Hamburg, Germany) until the German Bight. The vessel Littorina started already on the 29th of May in Kiel heading to the assembly point Cuxhaven and setting up the sensor systems. On May 30th all ships began the cruise traveling to Heligoland, nevertheless only the Ludwig Prandtl and Littorina could realize the first inter-calibration station (see file description) in front of Cuxhaven. An inter-calibration with all ships was conducted the next morning (31st of May) in front of Heligoland, before they went separate ways. While the Littorina crew covered the eastern part of the sampling area going towards Büsum, the scientists from Ludwig Prandtl headed further North to the island Amrum and the Uthörn covered the western part (see map in additional metadata). Littorina followed on the way to Büsum a more direct track, while on its way back to Heligoland on June 1st, the crew took a different route to extend the area further north. On the 2nd of June they travelled straight back to Cuxhaven to the last joined station with all three vessels. Instead, Ludwig Prandtl stayed the third and fourth day around Amrum, where they had to start sampling early in the morning (03:44h, 03:30h), due to the tide dependent entrance to the port. From there they headed directly back to Cuxhaven. The vessel Uthörn made a circuit north of Heligoland on the second day. On the third day the crew navigated from Heligoland to Cuxhaven and back to Heligoland in a triangle form. The last day the vessel headed back to Bremerhaven with a detour in Cuxhaven. Thus, all vessels closed the survey on the 2nd of June with a last inter-calibration station off Cuxhaven at about 10h. Additional information about the whole campaign and different cruises can be found in the article(s) cited, see also 'related to'.