DETERMINACION COMPARATIVA DE LA PRODUCCION PRIMARIA CON LAS TECNICAS DE 14C Y 02 EN AGUAS SALOBRES CON DIFERENTES GRADOS DE EUTROFICACION

The primary productivity of phytoplankton was determined in the mesotrophic Kiel Bight (KB), the eutrophic Kiel Fjord (KF) and the hypertrophic Schlei Fjord using the 14C-technique and the 0 2 -method. Results of these measurements were compared. These brackish areas of the Western-most part of the Baltic Sea differ markedly in primary productivity (PP). If the depth of maximum productivity alone is considered, the PP, on a volumetric basis, of the Schlei was 9 times higher than in the Kiel Fjord and more than 40 times that of the Kiel Bight. On an area basis the differences were much smaller since the compensation depth in the Schlei was found at no more than 0.8 m, whereas in the Kiel Bight it was 5.5 m and 5.2 m in the Kiel Fjord. In agreement with theoretical considerations, the PP determined with the 1*C-technique (1*C-PP) was larger than the net productivity (NP) and smaller than the gross productivity (GP), both determined with the 0 2-method using a photosynthetic quotient of 1.2. On average, in the Kiel Fjord the NP was 9 % smaller and the GP 36 % larger than the 14C-PP. In the Kiel Bight the NP was 40 % smaller and the GP 72 % larger. However, the relation NP<14CPP<GP was found only in the Kiel Bight and - Fjord, whereas in the polyproductive Schlei the 14C-PP was larger than both the NP and GP (32 % larger than the NP and 7 % larger than the GP). This deviation from theoretical values may be due, in part, to a senescent phytoplankton, which may have had a PQ smaller than 1.2.