40-year long-term study of microbial parameters near Helgoland (German Bight, North Sea): historical view and future perspectives

Since 1873, the waters at Helgoland Roads (sampling station “Kabeltonne”) have been sampled daily to determine temperature and salinity. In 1962, microbiological parameters were determined for the first time to establish microbiological long-term studies on marine bacteria, starting with the colony-forming units (CFU). In the following years, several other microbiological parameters were integrated for different periods of time (e.g. activity parameters like ATP and ectoenzymatic activity, marine yeasts, oil-degrading bacteria, flagellates and molecular methods like PCR followed by denaturing gradient gel electrophoresis). To date, the total count of bacteria, flagellates and viruses have been acquired using fluorescent DNA dyes and epifluorescence microscopy. Here we present both a historical overview of the methods used and examples of results obtained over the past 40 years. Furthermore, we try to evaluate challenging new methods for marine microbial ecology, appropriate for long-term studies of marine bacteria.