Introduction to the studies of pollution in the Oslofjord

Abstract

1. The Oslofjord penetrates inland over a distance of about 60 nautical miles from the open Skager-Rak to the capital city of Norway. At the town of Drøbak, about 2/3 up the fjord, there are a series of obstacles to a free exchange of water, the main passage being a channel about 300 m wide with a sill depth of 19 m. Inside Drøbak, the fjord consists of two wider basins, “Vestfjorden” and “Bunnefjorden” with depths down to 164 and 160 m. The area of the inner fjord is 191 km2; it holds about 9.4×109 m3 of water. The discharge of freshwater is about 800 million m3 per year, polluted by a population of 700 thousand and considerable industry. 2. Faunistic studies were made byO. F. Müller in the 18th, M. andG. O Sars in the 19th century, while more extensive hydrobiological studies were initiated byJ. Hjort andH. H. Gran about 1900. They were subsequently extended through participation of the staffs of biological institutes of the University of Oslo, especially from the early thirties, when the importance of the pollution for the biology of the inner fjord had become well documented. 3. In 1953 the situation had become so alarming that the authorities of the city of Oslo were warned that the use of the fjord as recipient for the city sewage had detrimental effects which required their attention and that more comprehensive studies were needed. The Norwegian Institute of Water Research (NIVA) was asked to plan and direct the cooperative investigations which have been carried out in the years 1962 to 1965. The Institute of Marine Biology of the University of Oslo and the Geophysical Institute of the University of Bergen participated in these studies. 4. This summer the results were reported to the supporting authorities in a general report, edited byK. Baalsrud, Director of NIVA, and in 20 special reports by participating scientists.