delta Deuterium of alkenone and BIT index of sediment core 64PE304-80 samples

Reconstructing past ocean salinity is important for assessing paleoceanographic change and therefore past climatic dynamics. Commonly, sea water salinity reconstruction is based on foraminifera oxygen isotope ratio values combined with sea surface temperature reconstruction. However, the approach relies on multiple proxies, resulting in relatively large uncertainty and, consequently, relatively low accuracy of salinity estimates. An alternative tool for past ocean salinity reconstruction is the hydrogen isotope composition of long chain (C37) alkenones (dDalkenone). Here, we applied dDalkenone to a 39 ka long coastal sediment record from the Eastern South African continental shelf in the Mozambique Channel, close to the Zambezi River mouth. Despite changes in global sea water dD related to glacial - interglacial ice volume effects, no clear changes were observed in the dDalkenone record throughout the entire 39 ka. The BIT index record from the same core showed high BIT values during the glacial and low values during the Holocene. This indicates a more pronounced freshwater influence at the core location during the glacial, resulting in alkenones depleted in deuterium during that time and, thereby, explains the lack of a clear glacial-interglacial alkenone dD shift. Correlation between the BIT index and dDalkenone during the glacial period suggests that increased continental runoff potentially changed the growth conditions of the alkenone producing haptophytes, promoting coastal haptophyte species with generally more enriched dDalkenone values. We therefore suggest that the application of dDalkenone for reconstructing past salinity in coastal settings may be complicated by changes in the alkenone producing haptophyte community.

Floral and faunal characteristics and content of photosynthetic pigment in soils of northern Victoria Land, Antarctica

Although soil algae are among the main primary producers in most terrestrial ecosystems of continental Antarctica, there are very few quantitative studies on their relative proportion in the main algal groups and on how their distribution is affected by biotic and abiotic factors. Such knowledge is essential for understanding the functioning of Antarctic terrestrial ecosystems. We therefore analyzed biological soil crusts from northern Victoria Land to determine their pH, electrical conductivity (EC), water content (W), total and organic C (TC and TOC) and total N (TN) contents, and the presence and abundance of photosynthetic pigments. In particular, the latter were tested as proxies for biomass and coarse-resolution community structure. Soil samples were collected from five sites with known soil algal communities and the distribution of pigments was shown to reflect differences in the relative proportions of Chlorophyta, Cyanophyta and Bacillariophyta in these sites. Multivariate and univariate models strongly indicated that almost all soil variables (EC, W, TOC and TN) were important environmental correlates of pigment distribution. However, a significant amount of variation is independent of these soil variables and may be ascribed to local variability such as changes in microclimate at varying spatial and temporal scales. There are at least five possible sources of local variation: pigment preservation, temporal variations in water availability, temporal and spatial interactions among environmental and biological components, the local-scale patchiness of organism distribution, and biotic interactions.

(Table 1) Organic carbon, hydrogen and oxygen index and hydrocarbons at DSDP Hole 93-603B

C2-C8 hydrocarbon concentrations (about 35 compounds identified, including saturated, aromatic, and olefinic compounds) from 27 shipboard-sealed, deep-frozen core samples of DSDP Hole 603B off the east coast of North America were determined by a gas-stripping/thermovaporization method. Total yields representing the hydrocarbons dissolved in the pore water and adsorbed on the mineral surfaces of the sediments vary from 22 to 2400 ng/g of dryweight sediment. Highest yields are measured in the two black shale samples of Core 603B-34 (hydrogen index of 360 and 320 mg/g Corg, respectively). In organic-carbon-normalized units these samples have hydrocarbon contents of 12,700 and 21,500 ng/g Corg, respectively, indicating the immaturity of their kerogens. Unusually high organic-carbonnormalized yields are associated with samples that are extremely lean in organic carbon. It is most likely that they are enriched by small amounts of migrated light hydrocarbons. This applies even to those samples with high organic-carbon contents (1.3-2.2%) of Sections 603B-28-4, 603B-29-1, 603B-49-2, and 603B-49-3, because they have an extremely low hydrocarbon potential (hydrogen index between 40 and 60 mg/g Corg). Nearly all samples were found to be contaminated by varying amounts of acetone that is used routinely in large quantities on board ship during core-cutting procedures. Therefore, 48 samples from the original set of 75 collected had to be excluded from the present study.

Table 1. Tree growth index and reconstructed precipitation series from 515 BC to AD 1993 based on the archaeological and living tree ring datasets from Dulan and Shenge, China

Annual precipitation for the last 2,500 years was reconstructed for northeastern Qinghai from living and archaeological juniper trees. A dominant feature of the precipitation of this area is a high degree of variability in mean rainfall at annual, decadal, and centennial scales, with many wet and dry periods that are corroborated by other paleoclimatic indicators. Reconstructed values of annual precipitation vary mostly from 100 to 300 mm and thus are no different from the modern instrumental record in Dulan. However, relatively dry years with below-average precipitation occurred more frequently in the past than in the present. Periods of relatively dry years occurred during 74-25 BC, AD 51-375, 426-500, 526-575, 626-700, 1100-1225, 1251-1325, 1451-1525, 1651-1750 and 1801-1825. Periods with a relatively wet climate occurred during AD 376-425, 576-625, 951-1050, 1351-1375, 1551-1600 and the present. This variability is probably related to latitudinal positions of winter frontal storms. Another key feature of precipitation in this area is an apparently direct relationship between interannual variability in rainfall with temperature, whereby increased warming in the future might lead to increased flooding and droughts. Such increased climatic variability might then impact human societies of the area, much as the climate has done for the past 2,500 years.

Physiological and ecological variables measured at the high and low pCO2 reef sections

Experiments have shown that ocean acidification due to rising atmospheric carbon dioxide concentrations has deleterious effects on the performance of many marine organisms. However, few empirical or modelling studies have addressed the long-term consequences of ocean acidification for marine ecosystems. Here we show that as pH declines from 8.1 to 7.8 (the change expected if atmospheric carbon dioxide concentrations increase from 390 to 750 ppm, consistent with some scenarios for the end of this century) some organisms benefit, but many more lose out. We investigated coral reefs, seagrasses and sediments that are acclimatized to low pH at three cool and shallow volcanic carbon dioxide seeps in Papua New Guinea. At reduced pH, we observed reductions in coral diversity, recruitment and abundances of structurally complex framework builders, and shifts in competitive interactions between taxa. However, coral cover remained constant between pH 8.1 and ~7.8, because massive Porites corals established dominance over structural corals, despite low rates of calcification. Reef development ceased below pH 7.7. Our empirical data from this unique field setting confirm model predictions that ocean acidification, together with temperature stress, will probably lead to severely reduced diversity, structural complexity and resilience of Indo-Pacific coral reefs within this century.

Alkenone unsaturation index and alkenones in ODP Hole 161-977A

A number of essential elements closely related to each other are involved in the Earth's climatic system. The temporal and spatial distribution of insolation determines wind patterns and the ocean's thermohaline pump. In turn, these last two are directly linked to the extension and retreat of marine and continental ice and to the chemistry of the atmosphere and the ocean. The variability of these elements may trigger, amplify, sustain or globalize rapid climatic changes. Paleoclimatic oscillations have been identified in this thesis by using fossil organic compounds synthesized by marine and terrestrial flora. High sedimentation rate deposits at the Barents and the Iberian peninsula continental margins were chosen in order to estimate the climatic changes on centennial time resolution. At the Barents margin, the sediment recovered was up to 15,000 years old (unit ''a'', from latin ''annos'') (M23258; west of the Bjørnøya island). At the Iberian margin, the sediment cores studied covered a wide range of time spans: up to 115,000 a (MD99-2343; north of the Minorca island), up to 250,000 a (ODP-977A; Alboran basin) and up to 420,000 a (MD01-2442, MD01-2443, MD01-2444, MD01-2445; close to the Tagus abyssal plain). At the northern site, inputs containing marine, continental and ancient reworked organic matter provided a detailed reconstruction of climate history at the time of the final retreat of the Barents ice sheet. At the western Barents continental slope, warm climatic conditions were observed during the early Holocene (~from 8,650 a to 5,240 a ago); in contrast, an apparent long-term cooling trend occurred in the late Holocene (~from 5,240 a to 760 a ago), in consistence with other paleoarchives from northern and southern European latitudes. The Iberian margin sites, which were never covered with large ice sheets, preserved exceptionally complete sequences of rapid events during ice ages hitherto not studied in such great detail: during the last glacial (~from 70,900 a to 11,800 a ago), the second glacial (~from 189,300 a to 127,500 a ago), the third ice age (~from 278,600 a to 244,800 a ago) and the fourth (~from 376,300 a to 337,500 a ago). In this thesis, crucial research questions were brought up concerning the severity of different glacial periods, the intensity and rates of the recorded oscillations and the long distance connections related to rapid climate change. The data obtained provide a sound basis to further research on the mechanisms involved in this rapid climate variability. An essential point of the research was the evidence that, over the past 420,000 a, at the whole Iberian margin, warm and stable long periods similar to the Holocene always ended abruptly in few centuries after a gradual deterioration of climate conditions. The detailed estimate of past climate variability provides clues to the natural end of the present warm period. Returning to an ice age in European lands would be exacerbated by a number of factors: a lack of differential solar heating between northern and southern north Atlantic latitudes, enhanced evaporation at low latitudes, and an increase in snowfall or iceberg discharges at northern regions. It must be emphasized that all climatic oscillations observed in this thesis were caused by forces of nature, i.e. the last two centuries were not taken into consideration.

Stable isotope record and aklenonen index of MIS 11 sediments

The interglacial known as Marine Isotope Stage 11 has been proposed to be analogous to the Holocene, owing to similarities in the amplitudes of orbital forcing. It has been difficult to compare the periods, however, because of the long duration of Stage 11 and a lack of detailed knowledge of any extreme climate events that may have occurred. Here we use the distinctive phasing between seasurface temperatures and the oxygen-isotope records of benthic foraminifera in the southeast Atlantic Ocean to stratigraphically align the Holocene interglacial with the first half of the Marine Isotope Stage 11 interglacial optimum. This alignment suggests that the second half of Marine Isotope Stage 11 should not be used as a reference for 'pre-anthropogenic' greenhouse-gas emissions. By compiling benthic carbon-isotope records from sites in the Atlantic Ocean on a single timescale, we also find that meridional overturning circulation strengthened about 415,000 years ago, at a time of high orbital obliquity. We propose that this mechanism transported heat to the high northern latitudes, inhibiting significant ice-sheet build-up and prolonging interglacial conditions. We suggest that this mechanism may have also prolonged other interglacial periods throughout the past 800,000 years.

Permafrost Favorability Index Map (PFI) for the Chilean Semi-Arid Andes

The Permafrost Favorability Index (PFI) map for the Chilean Semi-Arid Andes (29°S-32°S) indicates where permafrost is likely to occur (resolution 30 m x 30 m). The predicted favorability of permafrost occurrence ranges between 0 and 1, where high PFI values indicate most favorable environmental conditions for permafrost existence and low values indicates that permafrost will be present in exceptional circumstances with favorable local conditions. Conditions highly favorable to permafrost presence (PFI > 0.75) are predicted for 1051 km² of mountain terrain, or 2.7 % of the total area of the watersheds studied. Favorable conditions are expected to occur in 2636 km², or 6.8% of the area. Especially the Elqui and Huasco watersheds in the northern half of the study area where a substantial surface portion (11.8 % each) was considered to be favorable for permafrost presence, while predicted favorable areas in the southern Limarí and Choapa watersheds are mostly limited to specific sub-watersheds.

Natural high pCO2 increases autotrophy in Anemonia viridis (Anthozoa) as revealed from stable isotope (C, N) analysis

Contemporary cnidarian-algae symbioses are challenged by increasing CO2 concentrations (ocean warming and acidification) affecting organisms' biological performance. We examined the natural variability of carbon and nitrogen isotopes in the symbiotic sea anemone Anemonia viridis to investigate dietary shifts (autotrophy/heterotrophy) along a natural pCO2 gradient at the island of Vulcano, Italy. delta 13C values for both algal symbionts (Symbiodinium) and host tissue of A. viridis became significantly lighter with increasing seawater pCO2. Together with a decrease in the difference between delta 13C values of both fractions at the higher pCO2 sites, these results indicate there is a greater net autotrophic input to the A. viridis carbon budget under high pCO2 conditions. delta 15N values and C/N ratios did not change in Symbiodinium and host tissue along the pCO2 gradient. Additional physiological parameters revealed anemone protein and Symbiodinium chlorophyll a remained unaltered among sites. Symbiodinium density was similar among sites yet their mitotic index increased in anemones under elevated pCO2. Overall, our findings show that A. viridis is characterized by a higher autotrophic/heterotrophic ratio as pCO2 increases. The unique trophic flexibility of this species may give it a competitive advantage and enable its potential acclimation and ecological success in the future under increased ocean acidification.