Age model for the time between 3.45 and 2.45 Ma of ODP Site 189-1172

Calcareous nannoplankton assemblages and benthic d18O isotopes of Pliocene deep-sea sediments of ODP site 1172 (East of Tasmania) have been studied to improve our knowledge of the Southern Ocean paleoceanography. Our study site is located just north of the Subtropical Front (STF), an ideal setting to monitor migrations of the STF during our study period, between 3.45 and 2.45 Ma. The assemblage identified at ODP site 1172 has been interpreted as characteristic for the transitional zone water mass, located south of the STF, based on: (i) the low abundances (< 1%) of subtropical taxa, (ii) relatively high percentages of Coccolithus pelagicus, a subpolar type species, (iii) abundances from 2-10% of Calcidiscus leptoporus, a species that frequently inhabits the zone south of the STF and (iv) the high abundances of small Noelaerhabdaceae which at present dominates the zone south of the STF. Across our interval the calcareous nannoplankton manifests glacial-interglacial variability. We have identified cold events, characterized by high abundances of C. pelagicus which coincide with glacial periods, except during G7. After 3.1 Ma cold events are more frequent, in concordance with global cooling trends. Around 2.75 Ma, the interglacial stage G7 is characterized by anomalous low temperatures which most likely are linked to definite closure of the Central American Seaway (CAS), an event that is believed to have had global consequences. A gradual increase of very small Reticulofenestra across our section marks a significant trend in the small Noelaerhabdaceae species group and has been linked to a general enhanced mixing of the water column in agreement with previous studies. It is suggested that a rapid decline of small Gephyrocapsa after isotopic stage G7 might be related to the cooling observed in our study site after the closure of the CAS.

Major and rare earth element concentrations of basalts beneath ODP Hole 118-735B (Table 3)

A wide-angle seismic experiment at the Atlantis II Fracture Zone, Southwest Indian Ridge, together with geochemical analyses of dredged basalt glass samples from a site conjugate to Ocean Drilling Program hole 735B has allowed determination of the thickness and the most likely lithological composition of the crust beneath hole 735B. The measured Na, composition of 3.3 +/- 0.1 corresponds to a melt thickness of 3 +/- 1 km, a result consistent with rare earth element inversions which indicate a melt thickness of between 1.5 and 4.5 km. The seismic crustal thickness to the north and south of the Atlantis Platform (on which hole 735B is located) is 4 +/- 1 km, and probably consists largely of magmatic material since the seismic and inferred melt thicknesses agree within experimental uncertainty. Beneath hole 735B itself. the Moho is at a depth of 5 +/- 1 km beneath the seafloor. The seismic model suggests that, on average. about 1 km of upper crust has been unroofed on the Atlantis Platform. However, allowing for the inferred local unroofing of 2 km of upper crust at 735B, the base of the magmatic crust beneath this location is probably about 2 km beneath the seafloor, and is underlain by a 2-3 km thick layer of serpentinised mantle peridotite. The P-wave velocity of 6.9 km/s for the serpentinised peridotite layer corresponds to a 35 +/- 10 vol% serpentine content. The Moho beneath hole 735B probably represents a serpentinisation front.

FTIR-inferred biogeochemical properties for the past 3.6 Myr in the sediment record of core ICDP5011-1 in Lake Elgygytgyn, NE Russia

A number of studies have shown that Fourier transform infrared spectroscopy (FTIR) can be applied to quantitatively assess lacustrine sediment constituents. In this study, we developed calibration models based on FTIR for the quantitative determination of biogenic silica (BSi; n = 420; gradient: 0.9-56.5%), total organic carbon (TOC; n = 309; gradient: 0-2.9%), and total inorganic carbon (TIC; n= 152; gradient: 0-0.4%) in a 318 m-long sediment record with a basal age of 3.6 million years from Lake El'gygytgyn, Far East Russian Arctic. The developed partial least squares (PLS) regression models yield high cross-validated (CV) R2CV = 0.86-0.91 and low root mean square error of cross-validation (RMSECV) (3.1-7.0% of the gradient for the different properties). By applying these models to 6771 samples from the entire sediment record, we obtained detailed insight into bioproductivity variations in Lake El'gygytgyn throughout the middle to late Pliocene and Quaternary. High accumulation rates of BSi indicate a productivity maximum during the middle Pliocene (3.6-3.3 Ma), followed by gradually decreasing rates during the late Pliocene and Quaternary. The average BSi accumulation during the middle Pliocene was ~3 times higher than maximum accumulation rates during the past 1.5 million years. The indicated progressive deterioration of environmental and climatic conditions in the Siberian Arctic starting at ca. 3.3 Ma is consistent with the first occurrence of glacial periods and the finally complete establishment of glacial-interglacial cycles during the Quaternary.

Altered neurotransmitter function in CO2-exposed stickleback (Gasterosteus aculeatus): a temperate model species for ocean acidification research

Studies on the consequences of ocean acidification for the marine ecosystem have revealed behavioural changes in coral reef fishes exposed to sustained near-future CO2 levels. The changes have been linked to altered function of GABAergic neurotransmitter systems, because the behavioural alterations can be reversed rapidly by treatment with the GABAA receptor antagonist gabazine. Characterization of the molecular mechanisms involved would be greatly aided if these can be examined in a well-characterized model organism with a sequenced genome. It was recently shown that CO2-induced behavioural alterations are not confined to tropical species, but also affect the three-spined stickleback, although an involvement of the GABAA receptor was not examined. Here, we show that loss of lateralization in the stickleback can be restored rapidly and completely by gabazine treatment. This points towards a worrying universality of disturbed GABAA function after high-CO2 exposure in fishes from tropical to temperate marine habitats. Importantly, the stickleback is a model species with a sequenced and annotated genome, which greatly facilitates future studies on underlying molecular mechanisms.