Resipientundersøkelse i Randsfjorden 2003

Abstract

The environmental quality of Ranfjorden is regarded as little affected by municipal sewage the water quality normally varies between Very Good and Good (classes I-II). There are, however, evident effects from sewage at station 1 in the vicinity of the innermost outlet, Mjølanodden. This is regarded as a local problem and might be solved by changing the position of the outlet. The abundance of fast-growing algae in the littoral zone also gives evidence of elevated nutrient levels in the inner fjord. Oxygen-levels in the fjord are classified as Good to Very Good. The results from the benthic-fauna investigations indicate a need for remediation in order to obtain good environmental status (class II) throughout the inner fjord. However, it is not certain if the status can be improved merely by reducing the municipal sewage discharges. The observed decrease in concentrations of contaminants in sediments from 1992 to 2003 is probably related to the remediating action that has been taken in the area. The mining company Rana Gruber and the river Ranelva are supplying the fjord with large amounts of inorganic material. Variations in the input will have major influence on the concentration of pollutants in the sediments. The discharge of particulate matter from Rana Gruber have negative impact on both hard-bottom and soft-bottom communities. These effects might camouflage effects from eutrophication.