SKÄLDERVIKENS EUTROFIERING - EN STUDIE AV NÄRSALTSTRANSPORTER OCH FÖRORENINGSKÄLLOR I RÖNNEÅNS VATTENDRAGSSYSTEM 1978-1984, Eutrophication of the Bay of Skälderviken - a Study of Nutrient Loading and Nutrient Sources in the River Rönneå Drainage Basin 1978-1984

Algal blooms and oxygen deficiency in the hypolimnion have become common in coastal waters of the eastern Kattegat (southern Sweden). Increased nitrogen and phosphorus loads from inland waters are supposedly responsible for these phenomena. During the past few years the lowest summer oxygen concentrations of the Kattegat were found in Skälderviken bay. The Rönneå is the main source of freshwater to Skälderviken. The greatest part of the Rönneå’s drainage basin (1 460 km2) is located downstream of the hypertrophic Lake Ringsjön. The drainage basin consists of 52 % wooded land and 26 % arable land. From 1978 to 1984 the mean annual concentration of nitrogen in the river increased from 2.5 mg/1 N at the outflow of Lake Ringsjön to 3.5 mg/1 N at the mouth of the Rönneå, while the mean concentration of phosphorus decreased from 160 /μg/1 P to about 100 /μg/1 P. “Complete abstract not presented.”