Calcareous Nannofossil Assemblages from the Central Mediterranean Sea over the Last Four Centuries: The Impact of the Little Ice Age

We present decadal-scale calcareous nannofossil data from four short cores (Station272, 37170 N, 12480 E, 226m depth; St 342, 36420 N, 13550 E, 858.2m depth;St 407, 36230 N, 14270 E, 345.4m depth; C90-1M, 40360 N, 14420 E, 103.4 mdepth)5 recovered in the central Mediterranean Sea (northern Sicily Channel and TyrrhenianSea), which, on the basis of 210Pb activity span the last 200-350 years. Assemblagesare dominated by placoliths, mostly Emiliania huxleyi, while, at least in the Sicily Channelsediments, Florisphaera profunda was an important part of the coccolithophorecommunity.10 The paleoenvironmental reconstruction, based on ecological preference of speciesand groups, suggests that the Tyrrhenian core C90-1M maintained higher productivitylevels over recent centuries, with respect to the Sicily Channel sites, possibly becauseof more pronounced winter phytoplankton blooms, in agreement with modern primaryproductivity variations over the last ten years.15 The lowermost part of the record of one of the cores from the Sicily Channel, Station407, which extends down to 1650AD, is characterized by drastic changes in productivity.Specifically, below 1850AD, the decrease in abundance of F. profunda and theincrease of placoliths, suggest increased productivity. The chronology of this changeis related to the main phase of the Little Ice Age, which might have impacted the hy20drography of the southern coast of Sicily and promoted vertical mixing in the watercolumn. The comparison with climatic forcings points out the importance of strongerand prolonged northerlies, together with decreased solar irradiance. The identificationof the LIA in the northern Sicily Channel cover the Bond cycle BO that was missing ina previous study of Holocene climatic anomalies in the Sicily Channel.25 Finally, we suggest that major abundance changes in reworked nannofossil specimens,recorded in the Tyrrhenian core C90-1M, might be linked to variations in terrigenoussupply from land. Paradoxically, higher amounts of reworking correspond todry periods. We argue that soil and rock vulnerability is enhanced during times ofprolonged drought and vegetation cover loss.