Sammendrag
During the autumn 2014 macroinvertebrates, benthic algae and water quality were assessed at 5 sites
in River Glomma, one site in River Vorma and at one site in Lake Øyeren. The average phosphorus
concentration in Øyeren in 2014 was 7.8 μgP/l, classifying the lake to be at very good ecological
status, according to the Water Framework Directive criteria. The average concentration of chlorophyll
a in the production period was 4.1μg/l classifying the lake to very good ecological status.
The upper part of River Glomma is polluted by copper (average 4.88 μg/l), probably caused by runoff
from abandoned mines. The benthic algae at the uppermost sites of the river indicated very good
ecological status with respect to eutrophication. The ecological status was reduced downstream. The
ecological status according to benthic algae in River Vorma was good. The ecological status according
to benthic macroinvertebrates was very good at the uppermost sites with respect to organic load and
eutrophication, however it was reduced to good status further downstream. In Vorma the ecological
status according the macroinvertebrates was good. On the average the ecological status measured by
macroinvertebrates and benthic algae was fairly in accordance with each other, even though there was
a tendency for lower status as measured by macroinvertebrates.
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