Salt-marsh diatom distributions in Ho Bugt (western Denmark) and the development of a transfer function for reconstructing Holocene sea-level changes

Modern diatom samples and associated environmental variables were collected from the Kjelst Enge and Moservه salt marshes in the northern part of Ho Bugt, western Denmark. The relationship between diatom assemblages and elevation was investigated in order to assess the potential use of diatoms as sea-level indicators. Diatoms were found to be well preserved across the salt-marsh surface. A total of 54 diatom taxa were found with relative abundances greater than 3%. Cluster analysis reveals the presence of three vertical assemblage zones. The relationship between diatoms and environmental variables (elevation, pH, salinity) was explored using Canonical Correspondence Analysis (CCA). A series of partial CCAs shows that 24% of the explained variance can be attributed to elevation relative to tidal levels. Associated Monte Carlo permutation tests demonstrate that this relationship is significant (p = 0.014). We developed weighted averaging (WA) and weighted-averaging partial least squares (WA-PLS) transfer functions from 40 surface diatom samples. The WA-PLS transfer function was found to perform best (r2jack = 0.90, root mean square error of predictionjack = 0.14 m) and was subsequently applied to reconstruct salt-marsh surface elevations from the diatom assemblages in a core from Kjelst Enge salt marsh. The results indicate that with appropriate chronologic control it will be possible to establish a high-precision record of changing sea level from this core.