Home run for the RV Maria S. Merian:
Research vessel sets off towards the Baltic Sea ice
for the "Deep Baltic" mission

16.03.2021 – Eye to eye with a living "oxygen indicator"

After leaving the icy Bottenwiek, we continue the geological program: multicorers and gravity corers are used to search for post-glacial deposits. Are they there? Are they eroded? Incidentally, we find evidence in our MUC tubes that the bottom water here in the Bothnian Sea is sufficiently ventilated even at a water depth of more than 120 m: the very large isopod Saduria crawls out of the tubes, about 6 cm in size.  It must live here in large numbers, because we have a specimen in almost every tube. Where these crawling animals exist, the sediments are churned up and no longer show any stratification. Sedimentologists use this circumstance to distinguish in the older sediments oxygen-poor from oxygen-rich conditions at the bottom of the Baltic Sea, merely on the basis of stratification.

Text and Photo: Barbara Hentzsch (IOW) | click photo to enlarge