Leibniz Institute for Baltic Sea Research Warnemünde

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1 Leibniz Institute for Baltic Sea Research Warnemünde C r u i s e R e p o r t r/v "Elisabeth Mann Borgese" Cruise-No. EMB 45 Monitoring Cruise 3 May 12 May 213 Kiel Bight to Northern Baltic Proper This report is based on preliminary data Leibniz-Institut für Ostseeforschung Warnemünde an der Universität Rostock Seestraße 15 D Rostock- Warnemünde GERMANY

2 1. Cruise No.: EMB Dates of the cruise: from 3 May to 12 May Particulars of the research vessel: Name: Elisabeth Mann Borgese Nationality: Germany Operating Authority: Leibniz Institute for Baltic Sea Research (IOW) 4. Geographical area in which ship has operated: Kiel Bight to Northern Baltic Proper 5. Dates and names of ports of call No port of call 6. Purpose of the cruise Baltic monitoring in the frame of the COMBINE Programme of HELCOM 7. Crew: Name of master: Uwe Scholz Number of crew: 1 8. Research staff: Chief scientist: Dr. Wasmund, Norbert Scientists: Engineers: Technicians: Dr. Kuss, Joachim Ruickoldt, Johann Donath, Jan Beier, Sebastian Kreuzer, Lars Lage, Susanne Pötzsch, Michael Jürgensmann, Susanne, Henseler, Christina Scholz, Christian 9. Co-operating institutions: All institutions dealing with HELCOM monitoring programmes. 1. Scientific equipment CTDO bathysonde, water samplers, plankton nets 11. General remarks and preliminary results The area under investigation extended from Kiel Bight to the Northern Gotland Sea (station map see Figs. 1-3). On the way back, selected HELCOM stations in the Bornholm Sea, Arkona Sea and Mecklenburg Bight were sampled a second time for nutrient, phytoplankton and zooplankton data. The hydrographical, chemical and biological investigations were performed according to the Manual of the COMBINE Programme of HELCOM. Concerning the weather conditions, the cruise can roughly be divided into 4 periods: 1.) , while cruising through Mecklenburg Bight and Kiel Bight: high air pressure ( hpa), low easterly wind (<7 m/s), air temperature during the day 7-9 C, sunny. Due to the rather calm conditions, the water column was strongly

3 stratified. In shallower coastal areas (e.g. TFO5), the halocline started already at a depth of 7 m, but the strongest gradient was found between 15 and 2 m in the deeper central stations of Kiel Bight and Mecklenburg Bight (Stat. TF 361, TF36, TF12). The salinity increased at the most westerly station TF36 from 14 g/kg at the surface to 27 g/kg near the bottom with oxygen concentrations in the bottom water of 5-8 ml/l. The relatively high Secchi depth of 9 to 13 m indicated that no phytoplankton bloom occurred at that time. 2.), Mecklenburg Bight and western Arkona Sea: lower air pressure ( hpa), southerly winds up to 1 m/s, air temperature 6-8 C, sunny. The halocline starts in the central Arkona Sea at about 17 m depth. Salinity reaches 2 g/kg near the bottom with oxygen concentrations still higher than 5 ml/l. 3.) : This main part of the cruise covered the eastern Arkona Sea ( ), Bornholm Sea ( ), Eastern Gotland Basin and northern Baltic Proper ( ). The weather was still sunny, with high air pressure ( hpa), low south-westerly winds up to 1 m/s and air temperature of 5-1 C. Only in the afternoon of the it became cloudy with slight rain. The halocline started in the western part of the Bornholm Basin at a depth of 5 m, where water temperature was C. Below that depth, water temperature increased by 3-4 grd and oxygen concentration decreased to a minimum of ml/l at a depth of 7 m. In the southern part of the Gotland Basin (station TF 259, TF255), the halocline started at 6 m depth at a water temperature of 2 C, which increased to 5 C at about 84 m depth, where oxygen concentration decreased to almost zero. Below this minimum level, the oxygen concentration increased to over 3 ml/l. Up to station TF263, oxygen concentrations were relatively high near the bottom. In the deepest part of the Gotland Basin (stations TF272, TF271), the oxygen concentrations became zero at 115 m depth. At stations TF286 and TF285, oxygen was depleted below 1 m depth. The Secchi depth was high (11 m in Eastern Gotland Sea, 9 m in Bornholm Sea). 4.) , from the Landsort Deep and western Gotland Sea back to the Bornholm Sea ( ), Arkona Sea and Mecklenburg Bight ( ): It was cloudy; air pressure ranged from 18 to 11 hpa on with increase to 113 hpa on The south-westerly winds decreased from 8 m/s to 2 m/s on Similar to the Eastern Gotland Sea, the temperature increased sharply below the halocline (6 m) whereas the oxygen concentration decreased strongly to zero at a depth of 86 m also in the Western Gotland Sea (station TF284, TF24). The surface water temperatures (-1 m; C) of selected stations of this cruise are compared with early long-term mean values ( ) collected during our May cruises in the 197s and 198s in the table below. Because of the rather cold and long winter, surface water temperatures in the first half of May of 213 were lower than long-term data from the beginning of the systematic monitoring programme. Area: Mecklenburg Bight (stat. TF12) Arkona Sea (stat. TF113) Bornholm Sea (stat. TF213) Eastern Gotland Sea (stat. TF271) Farö Deep (stat. TF286) Karlsö Deep (stat. TF245) The long-term trend of increasing water temperature [ C] is representatively reflected in the deep water layers of the central deeps of the Baltic Proper. Only in the Bornholm Deep, the bottom-near water was warmer than the historical long-term mean of the 197s and 198s:

4 May Mean Bornholm Deep Gotland Deep Farö Deep Landsort Deep Karlsö Deep Appendix Tables 1& 2: Preliminary results for selected parameters in the surface layer and the nearbottom layer (unvalidated results) Figs. 1-3: Fig. 4: Fig. 5: Station grid (total grid and two sub-maps) Oxygen /hydrogen sulphide concentrations in the near-bottom layer for selected stations Transsect from the Kiel Bight to the Farö Deep for temperature, salinity and oxygen (unvalidated data) Dr. Norbert Wasmund Scientist in charge

5 Table 1: Surface layer ( - 1m) Area Station Temperature Salinity PO 4 3- NO 23 - * Date Name/ No. ** C PSU mol/dm 3 mol/dm 3 Kiel Bight Meckl. Bight Lübeck Bight Arkona Basin Bornholm Deep Stolpe Channel SE Gotland Basin Gotland Deep Fårö Deep Landsort Deep Karlsö Deep TF36/ 5 TF12/ 7 TF22/ 6 TF113/ 17 TF213/ 35 TF222/ 37 TF259/ 39 TF271/ 46 TF286/ 48 TF284/ 51 TF245/ * NO NO 3 ; NO 2 was present only in traces in most areas under investigation ** Station name see maps (Fig. 1-3)

6 Table 2: Bottom-near water layer Area Station Sampl. Depth Temp. Salinity O 2 PO 4 3- NO 23 - * Date Name/ No. ** m C PSU cm³/dm³ mol/dm 3 mol/dm 3 Kiel Bight Meckl. Bight Lübeck Bight Arkona Basin Bornholm Deep Stolpe Channel SE Gotland Basin Gotland Deep Fårö Deep Landsort Deep Karlsö Deep TF36/ 5 TF12/ 7 TF22/ 6 TF113/ 17 TF213/ 35 TF222/ 37 TF259/ 39 TF271/ 46 TF286/ 48 TF284/ 51 TF245/ * NO NO 3 ; NO 2 was present only in traces in most areas under investigation ** Station name see maps (Fig. 1-3)

7 EMB45 / map all monitoring stations Kiel Odense Lübeck DENMARK TF69TF15 TF14 TF13 TF19 TF113 TF114 ABBoje TF111 TF115 TF112 TF76 TF75 TF78 TF361 TF2 TF1 TF3 TF121 TF74 TF36 TF73 TF1 Gedser TF3 TF15 TF72 Sassnitz TF4 Fehmarn TF46 TF11 TF41 TF22 TF12 TFO5 Rostock GERMANY Kopenhagen Trelleborg Ystad TF12 SWEDEN TF145 map 1 TF14 TF142 map 2 TF144 BORNHOLM Ronne Karlskrona TF2 Longitude [ ] TF212 TF213 TF221 TF214 Koszalin Kalmar Västervik ÖLAND TF222 POLAND TF245 TF24 TF284 Visby GOTLAND TF256 TF259 TF255 Gdynia Slite Gdansk TF283 TF25 TF263 TF26 limit 1-22 / // scale TF286 TF272 TF27 TF271 TF285 Kalingrad Liepaja LATVIA Klaipeda Ventspils Department Physical Oceanography Jan Donath Leibniz Institute for Baltic Sea Research Warnemünde Latitude [ ] EMB4 / map 1 monitoring stations Kiel Odense TF36 TF361 Lübeck Fehmarn TF22 TF1 TF11 TF12 DENMARK Gedser TF4 TF46 TF41 GERMANY Fig1 and 2: Total station map and detailed map of the western Baltic Sea. TFO5 Rostock Longitude [ ] Kopenhagen TF76 TF75 TF78 TF74 TF2 TF73 TF3 TF72 TF3 TF1 Trelleborg Sassnitz Ystad Ronne BORNHOLM TF115 TF69 TF113 TF114 TF12 TF14 TF13 TF15 TF19 limit 1-15 / // scale TF111 ABBoje TF112 TF121 TF15 TF145 TF14 TF142 TF Department Physical Oceanography Jan Donath Leibniz Institute for Baltic Sea Research Warnemünde Latitude [ ]

8 Karlskrona Kalmar Västervik ÖLAND GOTLAND Fig. 3: Map of monitoring stations in the Baltic Proper EMB45 / map 2 monitoring stations TF2 TF212 TF213 TF221 TF214 Longitude [ ] Visby EMB45 / map O2 monitoring oxygen bottom - concentration [ml/l] Kiel Odense 6.91 Lübeck Fehmarn 5.54 DENMARK 5.8 Gedser Rostock GERMANY Kopenhagen 8.13 Trelleborg TF Ystad Sassnitz 8.92 TF245 SWEDEN TF24 BORNHOLM Ronne TF284 TF256 TF255 TF259 Karlskrona 3.72 Longitude [ ] Fig. 4: Oxygen/hydrogen sulphide concentrations in the near-bottom layer (selected stations) Slite TF283 TF TF263 TF26 TF286 TF272 TF27 TF271 TF285 limit / // scale Liepaja Klaipeda Ventspils LATVIA Department Physical Oceanography Jan Donath Leibniz Institute for Baltic Sea Research Warnemünde -.78(H2S) -.63(H2S) -.7(H2s) -3.57(H2S) Kalmar Koszalin Västervik ÖLAND POLAND Visby GOTLAND Gdynia Slite Gdansk limit 1-22 / // scale (H2S) Kalingrad Liepaja LATVIA Klaipeda Ventspils Department Physical Oceanography Jan Donath Leibniz Institute for Baltic Sea Research Warnemünde Latitude [ ] Latitude [ ]

9 MONITORING - EMB45 Kiel Bight - Gotland Sea : :13 UTC TF36 TF361 TF1 TF11 TF41 TF46 TF2 TF1 TF3 TF115 TF114 TF113 TF15 TF14 TF12 TF145 TF144 TF142 TF14 TF2 TF212 TF213 TF221 TF222 TF256 TF259 TF255 TF253 TF25 TF263 TF26 TF272 TF271 TF27 TF286 TF285-1 Depth [m] Temperature [ C] Depth [m] Salinity [psu] Depth [m] Oxygen [ml/l] Distance [n.m.] 1 5.srf 213 Leibniz Institute for Baltic Sea Research Warnemünde, Department Physical Oceanography Jan Donath Fig. 5: Transsect from the Kiel Bight to the Farö Deep for temperature, salinity and oxygen.