Brackish water as an environment

Abstract

1. Water is the most abundant compound on the surface of the Earth and the chemical basis for life on Earth. 2. The strong polarity of the water molecule assigns special physical and chemical properties to water as the direct environment in which aquatic organisms live, propagate and interact. 3. The surface tension of water creates the pleuston habitat and the viscosity of water requires adaptations, but it is also utilised by organisms for their life functions. 4. Water remains liquid over a broad range of temperatures, and the density anomaly of water makes ice float, which allows life to exist below the ice even when the water surface freezes. 5. In the brackish water of the Baltic Sea the ionic composition and the marine carbonate system deviate from marine water, which requires physiological adaptations of the organisms living in the Baltic Sea. 6. Natural brackish waters are classified according to ecologically relevant salinity ranges.