Investigative monitoring of benthic algae E18 Arendal-Tvedestrand

Summary

Construction of a new main road (E18) between Arendal and Tvedestrand, Norway, was initiated in mid-August 2015. To assess the impact of the construction work, preliminary surveys of the benthic algae and heterotrophic growth (bacteria and fungi) were undertaken at 14 locations in 5 water courses in early August. The results showed varying amounts of benthic algae, both in relation to % cover and species diversity. Classification of ecological status based on PIT (eutrophication), AIP (acidification) and HBI (organic load) showed moderate status of the two locations 3.10 in Langgangselva and 6.20 in Songebekken. These locations thus do not reach the environmental objective of good or very good ecological status according to the Water Framework Directive. The remaining locations showed good or very good ecological status. These classifications, along with the species lists, will make a good basis for comparison for future surveys after the road construction intervention.