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| Titel |
Hypoxia in the Baltic Sea as revealed by lipid biomarkers |
| VerfasserIn |
Klaas G. J. Nierop, Cornelia I. Blaga, Gert-Jan Reichart, Tom Jilbert, Caroline P. Slomp, Jaap S. Sinninghe Damsté |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053655
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| Zusammenfassung |
| Anthropogenic nutrient loading is a main cause of decreasing oxygen concentrations in the
Baltic Sea leading to an increase of so-called hypoxia (oxygen concentrations less than 2
mg/L oxygen) during the last century. In addition, natural, climate change-driven hypoxia
appeared during the last 8000 years. The increased flux of organic material to the bottom
water and sediments due to nutrient enrichment has disrupted the balance between oxygen
supply through physical processes and oxygen consumption from decomposition of organic
material. Apart from effects of oxygen concentrations on biogeochemical dynamics in the
sediment (e.g., N, P, S and Fe cycling) microbial and benthic faunal communities are affected
as well. The history of the various (micro)organisms is recorded in sediment cores, in
particular in the form of lipid biomarkers that are unique for a certain group of
organisms.
In this study, we assess whether the sedimentary record carries evidence for low-oxygen
conditions in the Bothnian Sea. This part of the Baltic Sea is currently well-oxygenated, but
may have experienced periods of low-oxygen conditions in the past. A preliminary study of
cores SR5 spanning the last 8000 years (recovered from the southern part of the Bothnian
Sea) and LL19 (from the Baltic Proper) revealed that the organic carbon is mainly
terrestrial-derived as evidenced by the high concentrations of higher plant lipids (n-alkanes,
n-alcohols, n-fatty acids). Common biomarkers typical of oxygen depleted conditions,
such as isorenieratene (from green sulfur-reducing bacteria) and lycopane (marine
photoautotrophs) were absent from the sediments. By contrast, 2,23- (C24) and 2,25- (C26)
alkanediols were highly abundant, and although their source organisms is yet unknown,
these compounds have been observed in several other oxygen depleted sediments.
Although cores SR5 and LL19 are from different locations with the Baltic proper
nowadays much more oxygen depleted than the Bothnian Sea, the relative abundances
of lipid biomarkers was rather similar albeit in a somewhat different distribution. |
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