Changes in spatial distribution of primary production,photosynthetic pigments and phytoplankton species composition during two surveys in the German bight |
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| Institution: | 1. College of Marine and Environmental Sciences, Tianjin University of Science and Technology, Tianjin 300457, PR China;2. Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science and Technology, Tianjin 300457, PR China;3. State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, Zhejiang 310012, PR China;4. College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, PR China;1. Natural History Museum of Denmark, Department of Biology, University of Copenhagen, Øster Farimagsgade 5, 1353 Copenhagen K, Denmark;2. Geological Survey of Denmark and Greenland, Department of Glaciology and Climate, Øster Voldgade 10, 1350 Copenhagen K, Denmark;3. Université Laval, Département de Biologie, Pavillon C-É Marchand, G1V 0A6 Québec City, Quebec, Canada;4. Marine Biological Section, Dept of Biology, University of Copenhagen, Universitetsparken 4, 1st floor, 2100 Copenhagen, Denmark;5. NIRAS, Ceres Allé 3, 8000 Aarhus C, Denmark;6. Orbicon, Department for Nature and Environment, Jens Juuls vej 16, 8260 Viby, Denmark;7. Alfred Wegener Institut-Helmholtz Zentrum für Polar- und Meeresforschung, Chemische Ökologie, Am Handelshafen 12, 27570 Bremerhaven, Germany |
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| Abstract: | A grid of 61 stations was sampled twice in the German Bight. At all stations dissolved nutrients (Si, P, N), fluorescence, temperature and salinity were measured along the vertical at surface, 5 m, 10 m, and 10 m intervals till the bottom. At selected stations photosynthetic rates were measured with 14C method (both surveys) and pigment with a HPLC method (first survey). Phytoplankton species composition was dominated by small diatoms, mainly Leptocylindrus minimus, flagellates, both dinoflagellates and choanoflagellates and near shore blooms of Phaeocystis pouchetii. Primary production and chlorophyll-a showed a linear correlation (r=0.90, n=23). Primary production showed highest rates along the North and East Frisian islands, where phytoplankton was dominated by Phaeocystis and Leptocylindrus. These coastal stations were completely mixed whereas a large part already showed stratification due to salinity and temperature. Thermocline and pycnocline were at about 10 m depth. No differences in oxygen content of surface or bottom waters were observed. Silicate and phophate concentrations were very low whereas nitrogen still showed very high concentrations. Low hypolimnetic oxygen concentrations are only possible when transport of primary produced organic matter is transported to stratified regions later in summer. Rapid growth of blooms was observed within a weeks period. More primary production measurements in the German Bight should be done to allow for budget calculations of oxygen consumption below the thermocline. |
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