Pre- and post-industrial environmental changes as revealed by the biogeochemical sedimentary record of Drammensfjord, Norway

Abstract

The biogeochemical sedimentary record of the anoxic Drammensf jord, Norway, was investigated on a decadal to centennial time scale over the last millennium, in order to reconstruct the pre-industrial f jord environment and ecosystem and humaninduced environmental changes. The sediments were dated by a combination of 14 C and 210 Pb analysis and varve counting. Analysis of the bulk sedimentary parameters and of the biomarker distribution revealed that the sedimentary organic matter of the f jord is primarily of terrigenous origin, indicating that the f jord was oligotrophic or mesotrophic. The f jord's bottom water has been continuously euxinic since at least 1000 AD, but photic zone euxinia occurred only irregularly in the f jord. The organic matter flux and composition remained virtually invariable until the 18th century. After that time, the flux of material derived from coniferous trees started to increase, indicated by elevated concentrations of dehydroabietic acid and related compounds, but also by raising levels of C 24 n-alcohols and fatty acids. This marked the onset of sawmill activities in the hinterland. After the beginning of the industrial revolution, around 1850, the flux of organic waste from sawmills and paper mills increased substantially. It is suggested that slow bacterial degradation of this relatively nutrient-poor organic waste caused a gradual eutrophication trend, which is reflected in substantial increased bacterial and moderately increased other aquatic biomarker accumulation rates. After the industrial revolution, this trend accelerated and was possibly enhanced by a growing population of the area with accompanying agricultural and domestic waste. This promoted primary productivity and changed the phytoplankton composition in the f jord. D

Historical records of coastal eutrophication-induced hypoxia

“…These changes correspond to a 20-30% reduction in upwelling and a 1.5-3 • C increase in temperature and suggest climatic influences on productivity (Stott et al, 2000). In deeper parts of Drammensfjord (∼110 m), pyrite-containing laminations indicate that hypoxic conditions have persisted throughout the last 1000 yrs (Alve, 1990(Alve, , 1991Smittenberg et al, 2005). Laminations are developed in other Norwegian fjords, for example, at 29-m depth in the Kyllaren Fjord (Smittenberg et al, 2004).…”

“…Lipid biomarkers (sterols, fatty acids, fatty alcohols) preserved in sediments are powerful tools for tracing environmental changes (Ficken and Farrimond, 1995;Canuel, 2000, 2002;Smittenberg et al, 2004Smittenberg et al, , 2005. Marine organisms, including bacteria, diatoms and dinoflagellates, produce characteristic lipid biomarkers that track changes in plankton communities in response to eutrophication.…”

Developments in Radiocarbon Technologies: From the Libby Counter to Compound-Specific AMS Analyses

“…Mollenhauer et al 2006). The influx of anthropogenic carbon, mostly from fossil fuel burning and spills have been extensively investigated (Reddy et al 2002a,b;Tanner et al 2004;Slater et al 2005Slater et al , 2006Smittenberg et al 2005;White et al 2005;Wakeham et al 2006). Interestingly, not all suspected pollution indicators are necessarily man-made.…”

Carbon isotopic composition of branched tetraether membrane lipids in soils suggest a rapid turnover and a heterotrophic life style of their source organism(s)

“…Thus far, only three studies reported the carbon isotopic composition of branched GDGTs (Pancost and Sinninghe Damsté, 2003;Smittenberg et al, 2005;Oppermann et al, 2010). The foremost reason for such few studies is that GDGT lipids themselves are not GC-amenable, and carbon isotopic determinations typically require either offline isolation (using, for example, preparatory liquid chromatography) of GDGTs or the chemical cleavage of the ether bonds, thereby releasing the GC-amenable octacosane components.…”

“…The glycerol units, however, comprise fewer than 10% of the carbon atoms of the whole tetraether. Using the first approach, Smittenberg et al (2005) reported δ 13 C values of −28.4‰ and −28.6‰ in sediment samples from Drammensfjord, Norway. These branched GDGT are most likely derived from forested soils in the catchment of the Drammen river and soils directly surrounding the fjord (Huguet et al, 2007).…”