Samples were routinely analysed for wet density (WD), percentage dry weight (%DW) at 105 °C, and loss-on-ignition analysis (LOI) at 550 °C, and data used to calculate diatom accumulation rates (DAR) in the sediment core. LOI is an approximation of organic content in sediment cores (Bengtsson and Enell, 1986). Each sample was prepared for diatom analysis using the procedure outlined in Mackay et al. (1998), minimizing additional dissolution of valves by omitting chemical pretreatments during preparation. Divinylbenzene microspheres (mean diameter 6.4 μm) were added to enable diatom concentrations and accumulation rates to be calculated (Battarbee and Kneen, 1982). Suspensions were settled on glass coverslips and permanent slides made using Naphrax slide mountant (refractive index 1.73). Diatoms were counted using oil immersion phase contrast light microscopy at ×1000 magnification.