A study of Mg/Ca in benthic foramini-fera sampled across a large salinity gradient

Abstract: Multiple studies have found a link between Mg/Ca in foraminifera and various environmental factors (e.g Billups and Schrag, 2002; Dissard et al., 2010; Ferguson et al., 2008). This has allowed for paleoenvi-ronmental reconstructions based on Mg/Ca in foraminifera to be made. My thesis has intended to find the influence of temperature and salinity on Mg/Ca in three species and one benthic Genus of foraminifera (Bulimina.marginata, Globobulimina.turgida, Nonionellina.labradorica and Elphidium spp.). The foraminifera were collected from eight modern coretops close to the Swedish coast from Hanö bay in the Baltic Sea to Skagerrak. In order to examine the accuracy of the produced calibration equations, an attempt was made to reconstruct temperature and salinity condit-ions in Lomma Bay. This was done by analysing the Mg/Ca in B.marginata and Elphidium spp. specimens from a core retrieved there and using the calibration equations to estimate past temperature and salinity. The produced calibration equations showed R2 values for temperature ranging from 0.1 to 0.5 and from 0.05 to 0.99 for salinity. R2 values from a multiple regression anlysis conducted on the data ranges from 0.11 to 1.00. The small number of data points resulted in low p-values for all examined taxa, this in combination with a lack of correspon-dance between estimated values for Lomma Bay temperature and salinity and actual modern values indicates that the calibration equations are not reliable. Large variations in Mg/Ca are observed ranging from 0.5 mmol/mol (G.turgida) to 1.6 mmol/mol (N.labradorica). Theese large variations occur over narrow gradients in temperature and salinity indicating that theese variations are mainly due to vital effects. My thesis contributes to increased knowledge of the distribution of Mg/Ca within benthic species of foraminifera and will contribute to increased knowledge of how Mg/Ca varies due to temperature and salinity in estuarine areas .