Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Heincke	HE444	12.05.2015 - 15.05.2015		North Sea

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Bohrmann Gerhard	Universitat Bremen, Zentrum fur Marine Umweltwissenschaften	Bremerhaven	Bremerhaven

Ziel der Reise / Objectives of Cruise:

Expedition HE444 was planned to test a novel R2Sonic multibeam echosounder for its capabilities to image gas bubbles in the water column. As a test location a known shallow-water (approx. 40 m) gas seepage area in the northern section of the Dutch North Sea (license block B13) was chosen. It was intended to image rising gas bubbles with the multibeam echosounder in various set-ups in order to find the best settings. The cruise commenced on Tuesday 12 May 2015 at 6 am UTC in Bremerhaven. After a transit of ca. 190 nm the research area was reached at 03:40 UTC on Wednesday 13 May and the first hydroacoustic survey was started. The survey was designed as reconnaissance survey to detect active gas emissions using the ship-mounted Kongsberg EM710 multibeam echosounder. Parallel to the EM710, also the Innomar SES2000 sediment echosounder and the moon pool-deployed R2Sonic 2026 were operated. Based on the results of the first survey a small area was chosen for detailed mapping using the R2Sonic echosounder. On the way to the starting point of the new detail survey, the signal of the R2Sonic echosounder was lost some time after adjusting its settings. After retrieving the sonar from the moon pool it was realized that a welding seam of the sonar holder had broken and the transducers were lost. This happened between 11:30 and 11:56 UTC on 13 May. After analyzing the situation a search survey using the ship's multibeam echosounder was started it the hope of locating the lost sonar in the EM710 backscatter data at 12:06 UTC. Due to the weather conditions and sea state, the quality of the recorded data was very poor and the search for the sonar remained unsuccessful. Based on the weather forecast it was decided to stay in the research area until the next morning (14 May) in order to make another attempt to locate the lost sonar before steaming back to Bremerhaven. During the night a survey with the ship's multibeam and sediment echosounders were conducted to obtain additional data for the better understanding of the regional geology and seepage system. Between 04:25 and 05:30 UTC on 14 May the CTD/ rosette was deployed at three stations along a transect through the seepage area in order to obtain water samples for the later analyses of methanotrophs. As the weather conditions remained bad, it was decided to leave the research area and to steam back to Bremerhaven. On the way back an additional sediment echosounder survey was conducted in the northern part of the German North Sea. The cruise ended in Bremerhaven on Friday 15 May, 7:00 UTC.

Messungen / Measurements