Kollsnes gas terminal. Environmental surveillance 2018: Freshwaters

Summary

This report presents results of environmental surveillance in freshwaters in the vicinity of the gas terminal at Kollsnes, Øygarden municipality in Hordaland county, Norway. The surveillance program consisted of monitoring chemical and biological conditions in two lakes, and is aimed at detecting potential effects of nitrogen oxides (NOx) released to air from the gas terminal. The program is part of a time series that repeats every 5th year, and results are compared with previous data. Within this project, additional monitoring focusing on terrestrial vegetation has been reported separately (Håland 2018). The ecological conditions in lakes Steinsvatn and Stølevatn were evaluated based primarily on phytoplankton biomass and composition as well as aquatic vegetation, following quality criteria developed under the Water Framework Directive as implemented in Norway. For the influence of eutrophication, we evaluated Lake Steinsvatn to be in Very good ecological state, while Lake Stølevatn was in Good ecological state. The difference between evaluations was caused by differences in the phytoplankton. Both lakes were evaluated to be in Good ecological state relative to acidification. Nonetheless, the water vegetation did indicate slight effects of acidification in both, and most pronounced in Lake Steinsvatn. Larger water-level fluctuations in Lake Steinsvatn may influence on this result. The zooplankton of both lakes appeared to be strongly suppressed through fish predation, with low species richness and unusual species composition. A few species known as moderately sensitive to acidification were recorded. Water chemistry data confirmed that both lakes are oligotrophic, with low concentrations of phosphorus and nitrogen. We detected no signs of chemical changes relative to previous records that could be attributed to nitrogen fallout from the gas terminal. A slight improvement in pH conditions relative to previous years was recorded in both lakes. In addition, we detected a slight increase in total organic carbon in both lakes. Both trends are continuations of previously known regional changes, which are attributed partly to declining atmospheric sulphur emissions, and partly to changing climate (increasing temperature, higher precipitation). We recommend that future monitoring in freshwaters should be better adapted to the criteria for data collection specified under the Water Framework Directive.