ALBERT

Description: Investigations indicate that the Iceland Ice Sheet was reduced in size during MIS 3 but readvanced to the shelf break at the LGM. Retreat occurred very rapidly around 15 k–16 k cal. yr BP. By contrast, the margin of the ice sheet on the East Greenland shelf, north of the Denmark Strait, was at or close to the shelf break during MIS 3 and 2 and retreat starting ∼17 k cal. yr BP. Quantitative X-ray diffraction analysis of the 〈2 mm sediment fraction was undertaken on 161 samples from Iceland and East Greenland diamictons, and from cores on the slopes and margins of the Denmark Strait. Weight% mineralogical data are used in a principal component analysis to differentiate sediments derived from the two margins. The first two PC axes explain 52% of the variance. These associations are used to characterise sediments as being affiliated with (a) Iceland, (b) East Greenland or (c) mixed. The contribution from Iceland becomes prominent during MIS 2. The extensive outcrop of early Tertiary basalts on East Greenland between 68° and 71° N is an alternative source for basaltic clasts and North Atlantic sediments with εNd(0) values close to ±0.

Description: Myrionecta rubra, a ubiquitous planktonic ciliate, has received much attention due to its wide distribution, occurrence as a red tide organism, and unusual cryptophyte endosymbiont. Although well studied in coastal waters, M. rubra is poorly examined in the open ocean. In the Irminger Basin, North Atlantic, the abundance of M. rubra was 0–5 cells/ml, which is low compared with that found in coastal areas. Distinct patchiness (100 km) was revealed by geostatistical analysis. Multiple regression indicated there was little relationship between M. rubra abundance and a number of environmental factors, with the exception of temperature and phytoplankton biomass, which influenced abundance in the spring. We also improve on studies that indicate distinct size classes of M. rubra; we statistically recognise four significantly distinct width classes (5–16, 12–23, 18–27, 21–33 μm), which decrease in abundance with increasing size. A multinomial logistic regression revealed the main variable correlated with this size distribution was ambient nitrate concentration. Finally, we propose a hypothesis for the distribution of sizes, involving nutrients, feeding, and dividing of the endosymbiont.

Description: A visible tephra horizon in the NGRIP ice core has been identified by geochemical analysis as the Fugloyarbanki Tephra, a widespread marker horizon in marine cores from the Faroe Islands area and the northern North Atlantic. An age of 26 740 ± 390 yr b2k (1s uncertainty) is derived for this tephra according to the new Greenland Ice Core Chronology (GICC05) based on multiparameter counting of annual layers. Detection of this tephra for the first time within the NGRIP ice core provides a key tie-point between marine and ice-core records during the transition between MIS 3 and 2. Identification of this volcanic event within the Greenland records demonstrates the future potential of using tephrochronology to precisely correlate palaeoarchives in widely separated localities that span the last glacial period, as well as providing a potential method for examining the extent of the radiocarbon marine reservoir effect at this time.

Description: Archived scales and otoliths constitute a unique source of DNA that potentially enables extension of the temporal scale of genetic studies of fish populations by decades and even centuries. We review recent insights into fish population and conservation genetics obtained using analysis of DNA from archived samples. This involves both new knowledge about demographic parameters and population structure in wild populations and insights into consequences of anthropogenic pressure resulting from over-harvesting, habitat degradation and stocking. We show that the latter category of studies have led to significant changes of management practices. Ongoing improvement of genetic methods will undoubtedly further expand the ability to utilize historical DNA samples. We envisage that temporal comparisons of large numbers of coding genes will lead to novel insights into selective responses of fish populations to anthropogenic challenges, particularly fisheries-induced selection and global warming. However, both acquisition and storage of historical DNA samples can be hurdles to temporal genetic analyses, while degradation and low copy number in historical DNA samples render genetic data from such sources prone to technical artefacts. We summarize recommendations for storage of samples and DNA extraction and provide checklists for validation of genotyping results. Finally, we stress that validation procedures also involve documentation of the time and population of origin of historical samples, and the inferences drawn should account for the technical and statistical uncertainties associated with historical DNA analysis.