Ancient DNA derived from alkenone-biosynthesizing haptophytes and other algae in Holocene sediments from the Black Sea

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 21 (2006): PA1005, doi:10.1029/2005PA001188.Holocene sea surface temperatures (SST) of the Black Sea have been reconstructed using sedimentary C37 unsaturated alkenones assumed to be derived from the coccolithophorid haptophyte Emiliania huxleyi, whose fossil coccoliths are an important constituent of the unit I sediments. However, alkenones can also be biosynthesized by haptophyte species that do not produce microscopic recognizable coccoliths. A species-specific identification of haptophytes is important in such U 37 K′-based past SST reconstructions since different species have different alkenone-SST calibrations. We showed that 18S rDNA of E. huxleyi made up only a very small percentage (less than 0.8%) of the total eukaryotic 18S rDNA within the up to 3600-year-old fossil record obtained from the depocenter (>2000 m) of the Black Sea. The predominant fossil 18S rDNA was derived from dinoflagellates (Gymnodinium spp.), which are predominant members of the summer phytoplankton bloom in the modern Black Sea. Using a polymerase chain reaction/denaturing gradient gel electrophoresis method selective for haptophytes, we recovered substantial numbers of a preserved 458-base-pair (bp)-long 18S rDNA fragment of E. huxleyi from the Holocene Black Sea sediments. Additional fossil haptophyte sequences were not detected, indicating that the E. huxleyi alkenone-SST calibration can be applied for at least the last ∼3600 years. The ancient E. huxleyi DNA was well protected against degradation since the DNA/alkenone ratio did not significantly decrease throughout the whole sediment core and 20% of ∼2700-year-old fossil E. huxleyi DNA was still up to 23,000 base pairs long. We showed that fossil DNA offers great potential to study the Holocene paleoecology and paleoenvironment of anoxic deep-sea settings in unprecedented detail.This work was supported by a grant from the Netherlands Organization for Scientific Research (NWO) (Open Competition Program 813.13.001 to M.J.L.C.) and NSF grant OCE0117824 to S.G.W., which we greatly appreciate

Current Practice of Cord Clamping in The Netherlands: A Questionnaire Study

Background: Recent meta-analyses recommend delayed cord clamping (DCC) after uncomplicated births as well as preterm births, but there is no clear definition of timing and uniform national guidelines are lacking. Objective: We aimed to investigate if guidelines for the timing of cord clamping (CC) are followed and what the national practice entails. Methods: A postal questionnaire concerning CC after uncomplicated vaginal, Caesarean term and preterm deliveries was sent to all midwifery practices (n = 526) and obstetrical departments (n = 94) in the Netherlands. Results: The response rate was 81% (500/620). CC protocols were present in 16 and 38% of midwifery and obstetric practices, respectively. Early cord clamping (ECC) was recommended in 54%, DCC in 33%, 6% indicated a specific time point and 7% did not specify. In current practice, DCC was applied after uncomplicated vaginal term deliveries in 90% and ECC in 6%, and no timing was specified in 4%. Midwives used DCC more often than obstetricians (97 vs. 75%). Cessation of cord pulsations was often (54%) used as a time point, 40% used a fixed time point, 2% waited for placental expulsion and 4% did not specify. ECC was preferred in obstetric practices after Caesarean deliveries (in 81%). In preterm births, ECC was practised by 36%, DCC by 54 and 10% did not specify. Conclusion: In the Netherlands, although often not protocolized, DCC is widely used after uncomplicated vaginal term and preterm deliveries, but not after Caesareans. Cessation of cord pulsation is often used as the time point for CC. (C) 2014 S. Karger AG, Base