Climate induced human demographic and cultural change in northern Europe during the mid-Holocene.

The transition from hunter-gatherer-fisher groups to agrarian societies is arguably the most significant change in human prehistory. In the European plain there is evidence for fully developed agrarian societies by 7,500 cal. yr BP, yet a well-established agrarian society does not appear in the north until 6,000 cal. yr BP for unknown reasons. Here we show a sudden increase in summer temperature at 6,000 cal. yr BP in northern Europe using a well-dated, high resolution record of sea surface temperature (SST) from the Baltic Sea. This temperature rise resulted in hypoxic conditions across the entire Baltic sea as revealed by multiple sedimentary records and supported by marine ecosystem modeling. Comparison with summed probability distributions of radiocarbon dates from archaeological sites indicate that this temperature rise coincided with both the introduction of farming, and a dramatic population increase. The evidence supports the hypothesis that the boundary of farming rapidly extended north at 6,000 cal. yr BP because terrestrial conditions in a previously marginal region improved.

Using fluffy layer material to study the fate of particle-bound organic pollutants in the southern Baltic Sea.

This paper examines the utility of fluffy layer material for studying and monitoring the environmental levels, transport, and fate of particle-bound contaminants in coastal ecosystems. Fluffy layer material is the very young and mobile layer of particulate matter that accumulates on the sediment surface under quiescent conditions. We used this material to study the behavior of polycyclic aromatic hydrocarbons (PAHs) that are discharged by the Oder River into the Baltic Sea. With the fluffy layer material, it was possible to (i) do fingerprint analysis to trace the sources of PAHs in the river discharge, (ii) follow the modification of the PAHs from the mouth of the river to the depositional basin and identify the responsible processes, (iii) monitor the seasonal variation in the PAH input, (iv) study the influence of a major flood event on the PAH loading to the coastal ecosystem, and (v) conduct a PAH mass balance to estimate the contribution of the Oder River source to PAH accumulation in the depositional basin. The fluffy layer material integrated the particle-bound contaminant signal over a period ranging from several days to several months, depending on the sampling location. As such, fluffy layer material is a valuable addition to the matrixes commonly used for studying particle-associated chemicals: SPM and sediment, which reflect time scales of hours and years, respectively.