Reconstructing the salinity and environment of the Limfjord and Vejlerne Nature Reserve, Denmark, using a diatom model for brackish lakes and fjords

Diatoms in surface sediments from a data set of 27 brackish lakes and nine fjords in Jutland, Denmark (range 0.2 - 31 g.L-1 total dissolved solids (TDS)), were analysed using multivariate methods to determine response to measured parameters (depth, total phosphorus (TP), total nitrogen (TN), TN/TP, salinity, water body type). Water body type, salinity, depth and TP together explained 25.3% of the variation in the diatom data and were all independently significant predictors. A diatom-salinity model (r(jack)(2) = 0.887, root mean square error of prediction = 0.246 log salinity, g.L-1) was developed from the 36 sample training set and applied to fossil diatom assemblages in three sediment cores from the east Vejlerne wetland, Denmark, a nature reserve created after the damming of an embayment of the polyhaline Limfjord (similar to26 g.L-1 TDS) in the late 19th century. The diatom-inferred salinity reconstructions reflect the known salinity history of the Limfjord and the freshwater-subsaline Vejlerne lakes, and appear sensitive to documented North Sea storms in the 16th and 17th centuries, which had major impacts on the brackish Limfjord herring fishery. Diatom-salinity models may be useful tools in long-term studies of coastal and estuarine areas to test hypotheses concerning aquatic resources and ecological, hydrographic, and cultural change.