Report: Gunni Ærtebjerg
Cruise leader: Jan Damgaard
Participants: Kjeld Sauerberg, Peter Kofoed, Dorete Jensen.
This report is based on preliminary data, which might later be corrected. Citation permitted only when quoting is evident. This file contains the summary only. To get the full report, click here. This file is in Adobe Acrobat ™ format. If you do not have a a Adobe Acrobat ™ Reader, click here, to download
Summary
Strong westerly winds had changed the hydrographic situation since the cruise in October. The salinity had increased in the surface water and decreased in the bottom water, and generally the salinity was higher than normal for the season, except for lower salinity in the Kattegat bottom water. A large water mass of 30-33 PSU, which might originate from the Jutland Coastal Current, was present in the northern Kattegat from the surface to about 50 m depth and further south in Kattegat as bottom water. The stratification had decreased, and a relatively strong halocline (10-13 PSU) was present only in the Sound, southernmost Kattegat, northern Great Belt and Arkona Sea. Inflow of salty oxygen rich water from the Sound and Belt Sea to the Arkona Sea was evident. The temperature was in the whole water column 9.7-12.0°C and higher than normal for the season.
Nitrate, phosphate and silicate were now present in the surface water, except for nitrate in the areas with the strongest stratification mentioned above. Relatively high concentrations of nitrite (0.5-0.8 µmol/l) and high concentrations of ammonium (1-3.5 µmol/l) were observed in the northern and eastern Kattegat in the 30-33 PSU water.
Relatively high concentrations of chlorophyll-a (3-6 µg/l) were observed in the central and southern Kattegat, Sound, Great Belt, Kiel Bight and central Arkona Sea. The lowest concentrations of 0.8-1.3 µg/l were observed in the northern Kattegat. The dominating species in eastern Kattegat were Proboscia alata, Chaetoceros spp., Pseudonitzschia spp. and Ceratium lineatum, in the southern Belt Sea Ceratium lineatum, C. tripos and C. fusus and in Mecklenburg Bight also Probiscia alata and Guinardia flacida. In the Arkona Sea large centric diatoms dominated.
Since the cruise in October the minimum oxygen concentration had increased in all areas, except in the north-eastern Kattegat. The lowest oxygen concentration of 3.1-3.6 ml/l (49-56%) was observed in the Sound and south-eastern Kattegat. Oxygen depletion was no longer present in the investigated Danish open sea areas.