Early Anthropogenic Transformation of the Danube-Black Sea System

Abstract

Over the last century humans have altered the export of fluvial materials leading to significant changes in morphology, chemistry, and biology of the coastal ocean. Here we present sedimentary, paleoenvironmental and paleogenetic evidence to show that the Black Sea, a nearly enclosed marine basin, was affected by land use long before the changes of the Industrial Era. Although watershed hydroclimate was spatially and temporally variable over the last ~3000 years, surface salinity dropped systematically in the Black Sea. Sediment loads delivered by Danube River, the main tributary of the Black Sea, significantly increased as land use intensified in the last two millennia, which led to a rapid expansion of its delta. Lastly, proliferation of diatoms and dinoflagellates over the last five to six centuries, when intensive deforestation occurred in Eastern Europe, points to an anthropogenic pulse of river-borne nutrients that radically transformed the food web structure in the Black Sea.

Periodic input of dust over the Eastern Carpathians during the Holocene linked with Saharan desertification and human impact

“…It is sensible to assume that the local deforestation (visible around the Mohos bog as meadows for hay harvesting) has caused local soil erosion and increased dust production from very proximal sources (Mulitza et al, 2010). This is a clear sign of the persistent human impact on local to regional scales during the early Holocene (Giosan et al, 2012;Schumacher et al, 2016), which is also mirrored in the nearby Lake Sfânta Ana record (Magyari et al, 2009). As indicated by regional studies (e.g.…”

“…The link between atmospheric circulation patterns and dust input has been studied intensively (Allan et al, 2013;Kylander et al, 2013a;Marx et al, 2009;Le Roux et al, 2012) with clear evidence of climate variations linked with the dust cycle (Goudie and Middleton, 2006). Generally, dust is produced in arid zones (Grousset and Biscaye, 2005) and may be transported thousands of miles before deposition (Grousset et al, 2003).…”

Unusual C35 to C38 alkenones in mid-Holocene sediments from a restricted estuary (Charlotte Harbor, Florida)

“…The C 36 alkenones in sediments from the Black Sea were also relatively enriched in deuterium with reported values between -112‰ and -162‰ (Giosan et al, 2012) corresponding, based on co-occuring C 37 alkenones, to salinity between 20 and 30. The offset in δD between C 36 and C 37 alkenones in the Black Sea of ca.…”

“…The D values of the C 36:2 and C 38:2 ethyl ketones from Unit II are unusual, since D enriched values of between -79‰ and -115‰ have only rarely been observed in natural systems (Giosan et al, 2012) and are offset from δD values in Unit I sediments by ca. 100‰.…”

Testing the D / H ratio of alkenones and palmitic acid as salinity proxies in the Amazon Plume

“…All these factors potentially exceed the effects of salinity and may impede the use of δD C 37 as a palaeosalinity proxy. Nevertheless, palaeoclimate studies have made successful use of δD C 37 as a palaeosalinity proxy (van der Meer et al, 2007(van der Meer et al, , 2008Giosan et al, 2012;Schmidt et al, 2014;Pahnke et al, 2007). However, in some cases, factors like species' variability complicated δD C 37 -based salinity reconstructions (Kasper et al, 2015).…”