'A lake is the landscape's most beautiful and expressive feature. It is earth's eye; looking into which the beholder measures the depth of his own nature. The fluviatile trees next the shore are the slender eyelashes which fringe it, and the wooded hills and cliffs around are its overhanging brows.' 'A field of water betrays the spirit that is in the air. It is continually receiving new life and motion from above.' 'Nothing so fair, so pure, and at the same time so large, as a lake, perchance, lies on the surface ofthe earth. Sky water. It needs no fence. Nations come and go without defiling it. It is a mirror which no stone can crack, whose quicksilver will never wear off, whose gilding Nature continually repairs; no storms, no dust, can dim its surface ever fresh; - a mirror in which all impurity presented to its sinks, swept and dusted by the sun's hazy brush, - this the light dust-cloth, - which retains no breath that is breathed on it, but sends its own to float as clouds high above its surface, and be reflected in its bosom still.' (Henry David Thoreau: 'Walden; or Life in the Woods'. Fourth printing, April 1953, Ri!lehart & Company, New York).

Inhalt
Input-output budgets at Langtjern, a small acidified lake in southern Norway.- Dissolved inorganic substances: A study of mass balance in three small drainage basins.- Dilution and acidification effects during the spring flood of four Swedish mountain brooks.- Trace metals in Swedish natural fresh waters.- Selenium as a growth factor for plankton algae in laboratory experiments and in some Swedish lakes.- Origin and production of phosphatases in the acid Lake Gardsjon.- Bacterioplankton in the acidified Lake Gårdsjön.- Respiration of plankton in two small polyhumic lakes.- Seasonal development of bacterioplankton in two forest lakes in central Sweden.- Relations between production and biomass of phytoplankton in four Swedish lakes of different trophic status and humic content.- Primary production and phytoplankton in two small, polyhumic forest lakes in southern Finland.- Zooplanktic indicators of trophy and their food.- Growth and feeding of Fredericella sultana (bryozoa) in the outlet of a humic acid lake.- The food preference of vendace (Coregonus albula) in South Swedish forest lakes including the predation effect on zooplankton populations.- Food and food selection of cisco (Coregonus albula L.) in a dysoligotrophic lake.- Differences in growth of perch (Perca fluviatilis L.) in two small forest lakes.- Ecological effects of lime treatment of acidified lakes and rivers in Sweden.