Short-term fluctuations of microbial and chemical variables during different seasons in coastal Baltic waters

Short-term fluctuations of microbial, planktological and chemical variables were studied in a nearshore area of the Kiel Bight during 4 different seasons. The following mean values in January, March, June and September were found: total bacterial numbers: 0.59, 0.46, 1.44 and 2.11 × 10⁶ cells ml⁻¹; maximum uptake velocity of glucose: 0.004, 0.037, 0.102 and 0.127 μg C l⁻¹h⁻¹; turnover rate of glucose: 17.9, 142, 496 and 265 % d⁻¹. Seasonal amplitude of variations in dissolved organic carbon was small. Maximum uptake velocity per bacterial cell increased by more than an order of magnitude between January and March and decreased slightly during the following seasons. Strong short-term variations of microbial parameters were detected, which did not show distinct diel rhythms. If these exist they are masked by changing hydrographical conditions.