Bakteriologisch-ökologische Untersuchungen in Sandstränden an Nord- und Ostsee

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Abstract
Investigations carried out at the beaches of the North Sea, Baltic and some other sea areas during the years 1967-1976 show in spite of all hydrographical and climatological differences, a fundamental conformity of the bacterial population, which applies to distribution and composition of the microflora. Of special importance is the occurrence of extreme halotolerant forms with wide ecological amplitudes. These bacteria are to a high extent adapted to the extreme location conditions such as great fluctuations of salinity, temperature and nutrient concentration. They are able to survive frequent exsiccation and rewetting without damage. Their share of the saprophytic flora increases considerably especially in the upper 20 cm of the beaches during the warm season. This plays a corresponding role in regard to mineralization of organic matter. Marine bacteria represent the majority of the extreme halotolerants. Gram-negative rods dominate, and are able to decompose proteins, carbohydrates and fats. Of 31 bacterial strains investigated, 23 show salinity optima of 30-50%. They can be distinguished from usual marine bacteria by high salinity maxima of 125-280% and relatively large temperature maxima of 40-45.degree. C, but not by their biochemical properties. In addition to natural factors like submerging, sun, wind, and rain the microflora are also influenced by beach life and bathing during the summer season. The share of terrestrial bacteria and coliforms increases at more frequently visted beach sectors. Baltic Sea beaches are more affected than those of the North Sea.