Pollen record and dating of a sediment profile from Ahlequellmoor in Germany

A pollen diagram from the Ahlequellmoor in the Solling area shows the history of vegetation and settlement over the last 7,800 years. In the early Atlantic period mixed deciduous forest with mainly Tilia together with Ulmus and Quercus grew in the area. In the late Atlantic period Quercus became most abundant. Fagus spread in the Sub-boreal period at about 2700 B.C. Since ca. 900 B.C. the Solling was covered by beech forests with some oak. In prehistoric times woodland grazing is indicated. Only in Medieval times are two settlements in the vicinity of the Ahlequellmoor reflected in the pollen diagram. The earlier one is dated to about A.D. 750-1020, and may be connected with the former Monastery of Hethis, which is thought to have existed close to the fen from A.D. 815 to 822. The second Medieval settlement dates to the 11th-12th century. The large-scale woodland destruction of late Medieval and modern times is not clearly visible. The silvicultural measures of the last 200 years are reflected by increasing values of spruce and grassland taxa.

Pollen record and dating of a sediment profile from Lake Voulkaria, Greece

A palynological investigation of a Holocene profile from Lake Voulkaria, western Greece, was carried out as a contribution to the environmental history of the coastal area of northwestern Acarnania and the Classical city of Palairos. It shows that deciduous oaks dominated the natural vegetation of the area throughout the Holocene. Until ca. 7000 B.C. Pistacia occurred abundantly, while other evergreen woody taxa were rare. At ca. 6300 B.C. an expansion of Carpinus orientalis/Ostrya can be observed. Around ca. 5300 B.C. spreading of Erica indicates a change to a drier climate and/or first human impact. Since ca. 3500 B.C. an increase of evergreen shrubs now clearly indicates land-use. The foundation of the Classical city of Palairos led to a temporary expansion of Phillyrea maquis. Within this period, molluscs of brackish water indicate the use of the lake as a harbour after the construction of a connection to the sea. The deciduous Quercus woodland recovered when human impact decreased in the area, and lasted until modern times.

B/Ca ratios in planktonic foraminifera

Boron isotope systematics indicate that boron incorporation into foraminiferal CaCO3 is determined by the partition coefficient, KD = [B/Ca](CaCO3)/[B(OH)4**-/HCO3**-](seawater), and [B(OH)4?/HCO3?](seawater), providing, in principle, a method to estimate seawater pH and PCO2. We have measured B/Ca ratios in Globigerina bulloides and Globorotaliainflata for a series of core tops from the North Atlantic and the Southern Ocean and in Globigerinoides ruber (white) from Ocean Drilling Program (ODP) site 668B on the Sierra Leone Rise in the eastern equatorial Atlantic. B/Ca ratios in these species of planktonic foraminifera seem unaffected by dissolution on the seafloor. KD shows a strong species-specific dependence on calcification temperature, which can be corrected for using the Mg/Ca temperature proxy. A preliminary study of G. inflata from Southern Ocean sediment core CHAT 16K suggests that temperature-corrected B/Ca was ~30% higher during the last glacial. Correspondingly, pH was 0.15 units higher and aqueous PCO2 was 95 ?atm lower at this site at the Last Glacial Maximum. The covariation between reconstructed PCO2 and the atmospheric pCO2 from the Vostok ice core demonstrates the feasibility of using B/Ca in planktonic foraminifera for reconstructing past variations in pH and PCO2.

Data compilation on the biological response to ocean acidification: environmental and experimental context of data sets and related literature

The exponential growth of studies on the biological response to ocean acidification over the last few decades has generated a large amount of data. To facilitate data comparison, a data compilation hosted at the data publisher PANGAEA was initiated in 2008 and is updated on a regular basis (doi:10.1594/PANGAEA.149999). By January 2015, a total of 581 data sets (over 4 000 000 data points) from 539 papers had been archived. Here we present the developments of this data compilation five years since its first description by Nisumaa et al. (2010). Most of study sites from which data archived are still in the Northern Hemisphere and the number of archived data from studies from the Southern Hemisphere and polar oceans are still relatively low. Data from 60 studies that investigated the response of a mix of organisms or natural communities were all added after 2010, indicating a welcomed shift from the study of individual organisms to communities and ecosystems. The initial imbalance of considerably more data archived on calcification and primary production than on other processes has improved. There is also a clear tendency towards more data archived from multifactorial studies after 2010. For easier and more effective access to ocean acidification data, the ocean acidification community is strongly encouraged to contribute to the data archiving effort, and help develop standard vocabularies describing the variables and define best practices for archiving ocean acidification data.

Sedimentology of various cores from the West Antarctic continental margin

Three megascopic and disseminated tephra layers (which we refer to as layers A, B, and C) occur in late Quaternary glaciomarine sediments deposited on the West Antarctic continental margin. The stratigraphical positions of the distal tephra layers in 28 of the 32 studied sediment cores suggest their deposition during latest Marine Isotopic Stage (MIS) 6 and MIS 5. One prominent tephra layer (layer B), which was deposited subsequent to the penultimate deglaciation (Termination II), is present in almost all of the cores. Geochemical analyses carried out on the glass shards of the layers reveal a uniform trachytic composition and indicate Marie Byrd Land (MBL), West Antarctica, as the common volcanic source. The geochemical composition of the marine tephra is compared to that of ash layers of similar age described from Mount Moulton and Mount Takahe in MBL and from ice cores drilled at Dome Fuji, Vostok and EPICA Dome C in East Antarctica. The three tephra layers in the marine sediments are chemically indistinguishable. Also five englacial ash layers from Mt. Moulton, which originated from highly explosive Plinian eruptions of the Mt. Berlin volcano in MBL between 142 ka and 92 ka ago, are chemically very similar, as are two tephra layers erupted from Mt. Takahe at ca. 102 ka and ca. 93 ka. Statistical analysis of the chemical composition of the glass shards indicates that the youngest tephra (layer A) in the marine cores matches the ash layer erupted from Mt. Berlin at 92 ka, which was previously correlated with tephra layers in the EPICA Dome C and the Dome Fuji ice cores. A tephra erupted from Mt. Berlin at 136 ka seems to correspond to a tephra layer deposited at 1733 m in the EPICA Dome C ice core. Additionally, the oldest tephra (layer C) in the marine sediments resembles an ash layer deposited at Vostok around 142 ka, but statistical evidence for the validity of this correlation is inconclusive. Although our results underscore the potential of tephrostratigraphy for correlating terrestrial and marine palaeoclimate archives, our study also reveals limitations of this technique, which may result in the miscorrelation of tephra. Such pitfalls comprise failure to recognise the occurrence of various tephra layers in marine sediment cores, 'swamping' of records with chemically indistinguishable tephra from a single volcanic source, and exclusive use of 'geochemical fingerprinting' for correlating ash layers.