Bakteriologische Untersuchungen an in der Brandungszone angetriebenem Algenmaterial

Abstract

The microbiological aspects of accumulations of ragged macroalgae in the surf zone of the Kiel Bight [West Germany] were investigated. High counts of saprophytic bacteria including agar-, starch- and cellulose-digesting forms were found regularly associated with algal material. The bacterial counts increased with both the algal count and with the extent to which the algae had been ground by the wave action. Laboratory experiments showed that under high nutrient conditions both the number of saprophytes and the number of specialized microbes increased during the 1st 2 days of incubation. After reaching the maximum counts, the number of bacteria decreased considerably within 24 h. In the same period a short term development of protozoa was observed. The total number of cells (direct counts) showed only small fluctuations during the decomposition of algal material. Changes in the composition of bacterial populations were not observed under the microscope. The NH4 derived from the decomposition of proteins was oxidized to NO2 and NO3 by nitrifying bacteria. More nitrifying bacteria were found on the algal material than in the surrounding water. Bacterial activity and lysis of cells led to a considerable decrease in the content of particulate organic C within 1 wk. Dissolved organic C was decomposed very rapidly during the period of highest bacterial activity.