S. Kristiansen, IMPACT OF INCREASED RIVER DISCHARGE ON THE PHYTOPLANKTON COMMUNITY INTHE OUTER OSLOFJORD, NORWAY, Hydrobiologia, 363, 1998, pp. 169-177
An extraordinary flood event occurred in Southern Norway in May-June 1
995. The impact of fresh water discharge from the river Glomma on phyt
oplankton species composition and on primary production during the flo
od was studied. The phytoplankton community was dominated by species u
sually found in the fjord, the diatom Skeletonema costatum dominated t
he community together with cyanobacteria. Potentially harmful species
(e.g. Chrysochromulina polylepis) were found in low cell densities. No
large increase in nutrient concentrations were found. Primary product
ion and uptake rates of nitrate and ammonium were very low in low-sali
nity water near the river outlet. Nutrients from the river water were
efficiently utilized in the open part of the fjord. The flood trigged
a phytoplankton bloom dominated by harmless, species commonly observed
in the fjord plankton.