Geochemistry of ODP Sites 121-758 and 121-757

Nd isotopes are useful tracers for paleoceanography due to the short Nd residence time in seawater and the large differences between the isotopic signatures of various geological reservoirs. Therefore, ?Nd variations reflect the geological history of individual oceanic basins. Using a differential dissolution technique, which extracts Nd isotopes of seawater trapped in MnO2 coatings and carbonates in marine sediment, we measured almost two hundred samples from ODP Sites 758 and 757 in the Northern Bay of Bengal covering the last 4 Ma. For the first time, we have shown a covariation between epsilon-Nd and d18O over at least the last 800 ka. We also show that from 4 Ma to 2.6 Ma, epsilon-Nd is almost constant and starts to fluctuate at 2.6 Ma when northern glaciations increased. From 2.6 Ma to 1 Ma the fluctuation period is close to 40 ka while from 1 Ma to present it is dominantly 100 ka. We attribute these findings to mixing between Himalayan river water (that ultimately originates as Indian summer monsoon rain) and normal Bay of Bengal seawater. Previous studies on seawater, using epsilon-Nd, d18O analyzed on planktonic foraminifera and sedimentary data, can be integrated into this model. A simple quantitative binary mixing model suggests that the summer monsoon rain was more intense during interglacial than glacial periods. During last glacial episode, the monsoon trajectory was deviated to the east. At a large scale, the Indian monsoon is fully controlled by the variations in Northern Hemisphere climate but with a complex response function to this forcing. Our study clearly establishes the large potential of Nd isotope data to evaluate the hydrological river regime during the Quaternary and its relationship with climate fluctuations, particularly when the sediment archive is sampled close to sediment sources.

Occurrence and chemistry of microtektites of ODP Site 121-758

The Toba lake event, the Australasian microtektite event, and the Cretaceous/Paleogene boundary were analyzed on the basis of foraminifers, carbonate content, trace elements, and spherules (microtektites). The Toba ash event, recovered in Hole 758C, may have had minor influences on the foraminiferal populations. The Australasian tektite event has probably some influence on foraminiferal ecology, because the larger specimens become scarce just above the microtektite layer. Microtektites recovered from Hole 758B closely resemble spherules recovered from several Cretaceous/Paleogene boundary localities in North America. The Cretaceous/Paleogene spherules, however, are usually larger and are completely altered to goyazite in the terrestrial environment and to smectite in a marine environment. The Cretaceous/Paleogene boundary of Hole 752B does not show obvious anomalous trace-element concentrations, and iridium concentrations are below our detection limits. The trace-element pattern is dominated by the alternation of chalk with volcanic ash layers above the Cretaceous/Paleogene boundary.

Organic carbon geochemistry of ODP Leg 121 samples

Organic petrological and geochemical analyses were performed on samples cored on Broken Ridge and Ninetyeast Ridge in the Central Indian Ocean during Leg 121. Organic carbon (Corg) contents are less than 1% in each individual sample and average Corg values calculated for larger stratigraphic units are less than 0.2%. Generally, there is more organic matter in Cretaceous sediments than in Tertiary. In the Cretaceous, the bulk of the organic matter consists of terrigenous debris, but a significant contribution of marine-derived organic matter was found in some samples, especially in the early Maestrichtian on Broken Ridge (Site 754). The youngest Pliocene-Pleistocene sediments at Site 758 (northern part of Ninetyeast Ridge) contain a significant amount of clastic material transported to the site by the (distal) Bengal Fan. In these sediments, Corg contents of up to 0.9% were measured and are due to the inflow of terrigenous organic debris. Corg values are positively correlated with bulk sediment accumulation rates (i.e., sediments contain more organic matter at times of faster deposition). The size of terrigenous organic particles is generally small in all sediments. The extremely small number of particles in the Cretaceous sediments at Site 758 and their smaller grain size, compared to the Cretaceous sediments on Broken Ridge, indicate that Cretaceous surface water paleocurrents flowed from southeast to northwest in the Proto-Indian Ocean. In the central Indian Ocean, sediments deposited above the carbonate compensation depth consist of nannofossil and foraminiferal oozes. In contrast to Corg values, calcite contents in the sediments are negatively correlated with bulk sediment accumulation rates (i.e., carbonate oozes were deposited only during times of extremely slow sedimentation). Therefore, older sediments deposited in the young and still narrow Indian Ocean accumulated faster and are less carbonate-rich than Neogene sediments, although carbonate accumulation rates were higher.

Abundance of calcareous nannofossils in ODP Hole 121-752B (Table 1)

A biostratigraphically complete Cretaceous/Tertiary boundary was recovered during Ocean Drilling Program Leg 121. The boundary, cored in ODP Hole 752B on Broken Ridge, is the most expanded deep-sea section yet recovered by ODP/DSDP. The initial Danian subzone, CP la, spans nearly 5 m and the underlying uppermost Maestrichtian Nephrolithus frequens Zone extends 50 m below the boundary. The paleolatitude of Broken Ridge at Cretaceous/Tertiary time is estimated at 50°-55°S which includes this site among the latest in a series of complete or near complete high southern latitude Cretaceous/Tertiary boundary sections recovered by ODP (Leg 113 Site 690 and Leg 119 Site 738). The boundary at Site 752 lies at the base of a thick (6-6.5 m) volcanic ash unit composed of multiple ash layers which overlies indurated Maestrichtian chalks. Magnetostratigraphy indicates that the boundary lies within Subchron 29R, which is the case for all other known complete sections for which the polarity has been determined. Anomalous abundances of the trace element iridium are present at the boundary. A second iridium peak, 80 cm above the boundary, corresponds to an increase in redeposited Cretaceous nannofossils. The nannofossil succession is similar to that found at previously studied austral high-latitude ODP drill sites with few differences due to the more northerly location of this site. Individual nannofossil species were counted and placed into three categories. A plot of the percent abundance of Cretaceous, Tertiary, and 'survivor' groups illustrates the rapid replacement of the Cretaceous nannoflora by 'survivor' forms beginning at the boundary and the dominance of this latter group through the initial Danian biozone. This 'survivor' or opportunistic assemblage is then rapidly replaced by newly evolved Tertiary taxa. The assemblage of the uppermost Maestrichtian is biased toward dissolution-resistant forms such as Micula decussata. In those few intervals where preservation is good, the dissolution susceptible species, Prediscosphaera stoveri, is more prevalent and overall diversity of the assemblage is higher. The 'survivor' assemblage is dominated by Zygodiscus sigmoides and Thoracosphaera. The Tertiary assemblage consists of rare Biantholithus sparsus, the first of this group to appear. It is followed several meters upsection by Cruciplacolithus primus. Cruciplacolithus tenuis and small Prinsius spp. dominate the assemblage beginning at about 5 m above the boundary.

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.

(Table 1) Individual codes, haplotype codes, GenBank accession numbers for DNA sequences and sample locality of the analysed Betamorpha fusiformis specimens from the ANDEEP III expedition

Based on our current knowledge about population genetics, phylogeography and speciation, we begin to understand that the deep sea harbours more species than suggested in the past. Deep-sea soft-sediment environment in particular hosts a diverse and highly endemic invertebrate fauna. Very little is known about evolutionary processes that generate this remarkable species richness, the genetic variability and spatial distribution of deep-sea animals. In this study, phylogeographic patterns and the genetic variability among eight populations of the abundant and widespread deep-sea isopod morphospecies Betamorpha fusiformis [Barnard, K.H., 1920. Contributions to the crustacean fauna of South Africa. 6. Further additions to the list of marine isopods. Annals of the South African Museum 17, 319-438] were examined. A fragment of the mitochondrial 16S rRNA gene of 50 specimens and the complete nuclear 18S rRNA gene of 7 specimens were sequenced. The molecular data reveal high levels of genetic variability of both genes between populations, giving evidence for distinct monophyletic groups of haplotypes with average p-distances ranging from 0.0470 to 0.1440 (d-distances: 0.0592-0.2850) of the 16S rDNA, and 18S rDNA p-distances ranging between 0.0032 and 0.0174 (d-distances: 0.0033-0.0195). Intermediate values are absent. Our results show that widely distributed benthic deep-sea organisms of a homogeneous phenotype can be differentiated into genetically highly divergent populations. Sympatry of some genotypes indicates the existence of cryptic speciation. Flocks of closely related but genetically distinct species probably exist in other widespread benthic deep-sea asellotes and other Peracarida. Based on existing data we hypothesize that many widespread morphospecies are complexes of cryptic biological species (patchwork hypothesis).

Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix, supplementary material

Siberian boreal forests are expected to expand northwards in the course of global warming. However, processes of the treeline ecotone transition, as well astiming and related climate feedbacks are still not understood. Here, we present 'Larix Vegetation Simulator' LAVESI, an individual-based spatially-explicit model that can simulate Larix gmelinii (RUPR.) RUPR. stand dynamics in an attempt to improve our understanding about past and future treeline movements under changing climates. The relevant processes (growth, seed production and dispersal, establishment and mortality) are incorporated and adjusted to observation data mainly gained from the literature. Results of a local sensitivity analysis support the robustness of the model's parameterization by giving relatively small sensitivity values. We tested the model by simulating tree stands under modern climate across the whole Taymyr Peninsula, north-central Siberia (c. 64-80° N; 92-119° E). We find tree densities similar to observed forests in the northern to mid-treeline areas, but densities are overestimated in the southern parts of the simulated region. Finally, from a temperature-forcing experiment, we detect that the responses of tree stands lag the hypothetical warming by several decades, until the end of 21st century. With our simulation experiments we demonstrate that the newly-developed model captures the dynamics of the Siberian latitudinal treeline.