Sammendrag
This report presents the results of environmental surveillance in freshwaters in the vicinity of the gas
terminal at Kollsnes, Øygarden in Hordaland, Norway. The surveillance program consisted of monitoring
chemical and biological conditions in two lakes. The program is part of a time series, and results are
compared with previous data.
Both of the examined lakes were poor in nutrients. However, biotic interactions seem to be responsible
for unexpectedly high phytoplankton biomass levels in both lakes relative to the low phosphorus levels.
This could be explained by cascading effects of intense predation on zooplankton by dense populations of
three-spined sticklebacks.
Species composition of aquatic macrophytes confirmed that the lakes are not overloaded with nutrients, as
both lakes met the standards of ‘Very good ecological status’ according to the EU Water Framework
Directive implementation in Norway. However, the aquatic vegetation also indicated that both lakes are,
or have been, impacted by acidification. This result is consistent with water chemistry data from the
1990’s. The 2013 data show no indication that local nitrogen oxide emissions contribute to acidification of
the lakes.
A slight improvement in acidity was apparent in both lakes when compared to conditions in the 1990’s.
Further, a marked increase in contents of organic carbon was evident in both lakes. These developments
appear to general for the region, in part due to reduced sulphur deposition and partly due to climate
change (increased precipitation).
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