IP25 AND BRASSICASTEROL: THE BIOMARKER AS ICE PROXY FOR THE SEA ICE COVERING IN THE ARCTIC OCEAN

Abstract

Stable biomolecules play an important role in the oceans because they can be used to determine the origin and the translocation of the organic material such as sterols which are synthesized by plants. In recent times, a major focus has been on a new biomarker in the high latitudes, a highly branched Isoprenoid (HBI) as the new sea ice proxy 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl) Pentadecane (IP25, Ice Proxy with 25 carbon atoms). The stability of the proxies such as sterols and HBI is important because only an almost inert character of the molecules ensures its reproducible use as biomarker proxy.In this research, different analytical methods were used to check whether these components actually fulfill the requirements of duration and storage to be stable that possible degradation processes such as microbial degradation and autoxidation. However, duration and storage are proven negligible or can be treated as the secondary essential factors. For this purpose, samples of a sediment core from the continental shelf of the East Siberian Sea were analyzed. Samples from this core were stored (1) deep frozen directly after sampling (-30°C) and (2) at 5°C for an extended time period.The results show that the degradation processes are negligible or least only of secondary importance. The concentrations of the biomarker show good correlations. The ratio between Brassicasterol and IP₂₅ (PIP₂₅-Index) is not affected by the different storages. In addition, all measurements using gas chromatography and mass spectrometry result in nearly the same concentrations of the compounds.