ALBERT

Description: Tropical South America is one of the three main centres of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the 'Walker' circulation1). Although this area plays a key role in global climate cycles, little is known about South American climate history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the tropical Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last Glacial Maximum—marked in the drill core by continuous deposition of lacustrine sediments—appear to have occurred in phase with summer insolation maxima produced by the Earth's precessional cycle. Short-duration, millennial events correlate well with North Atlantic cold events, including Heinrich events 1 and 2, as well as the Younger Dryas episode. At both millennial and orbital timescales, cold sea surface temperatures in the high-latitude North Atlantic were coeval with wet conditions in tropical South America, suggesting a common forcing.

Description: According to small subunit ribosomal RNA (ss rRNA) sequence comparisons all known Archaea belong to the phyla Crenarchaeota, Euryarchaeota, and—indicated only by environmental DNA sequences—to the 'Korarchaeota'1, 2. Here we report the cultivation of a new nanosized hyperthermophilic archaeon from a submarine hot vent. This archaeon cannot be attached to one of these groups and therefore must represent an unknown phylum which we name 'Nanoarchaeota' and species, which we name 'Nanoarchaeum equitans'. Cells of 'N. equitans' are spherical, and only about 400 nm in diameter. They grow attached to the surface of a specific archaeal host, a new member of the genus Ignicoccus3. The distribution of the 'Nanoarchaeota' is so far unknown. Owing to their unusual ss rRNA sequence, members remained undetectable by commonly used ecological studies based on the polymerase chain reaction4. 'N. equitans' harbours the smallest archaeal genome; it is only 0.5 megabases in size. This organism will provide insight into the evolution of thermophily, of tiny genomes and of interspecies communication.

Description: THE rare deep-sea octopod Cirrothauma murrayi Chun 1910 was first described from a single specimen caught during the Michael Sars Expedition of 1910 (ref. 1). Until now it has been caught only four more times2. We describe here three specimens of this species that were recently caught during biological cruises of RRS Discovery (Fig. 1). All of these animals, including the Discovery ones, have been caught at depths of more than 1,500 m, except one that was dip-netted through the ice of the Arctic Ocean3.

Description: THE Sierra Leone Rise, located in the east equatorial Atlantic, forms a discontinuous chain of seamounts as shallow as 2 km extending with a general NE–SW trend from near the Sierra Leone coast of Africa, to the St Paul fracture zone near the Mid-Atlantic Ridge (Fig. 1). The origin of this feature has remained a topic of discussion. Sheridan et al.1 have hypothesised that the Sierra Leone Rise is a volcanic structure formed at the beginning of the opening of the Atlantic in the early Cretaceous period. The twin features of the Sierra Leone and the Ceara Rises are probably of oceanic origin and were created 80 Myr ago or later in their present-day position with respect to Africa and South America2. The Atlantic ocean exhibits several similar aseismic structures which appear symmetrically oriented with respect to the mid-oceanic ridge, such as the Walvis–Rio Grande Rise and the Iceland Faeroes–Iceland Greenland Ridges. These structures are volcanic edifices having a composition similar to that found in their associated islands3–7. Deep sea drilling of the Ceara Rise8,9 penetrated a basaltic basement of the upper Cretaceous period (Maestrichtian) (Leg 39, Site 354). Similarly, a DSDP hole (Leg 41, Site 366) on the Sierra Leone Rise, penetrated sediments of the same period, without reaching basement10. We report here the discovery of alkali-rich volcanics in an area of the Sierra Leone Rise. The sediment overlying the rock fragments is aged ∼45 Myr.

Description: The onset of the Palaeocene/Eocene thermal maximum (about 55 Myr ago) was marked by global surface temperatures warming by 5–7 °C over approximately 30,000 yr (ref. 1), probably because of enhanced mantle outgassing2, 3 and the pulsed release of approx1,500 gigatonnes of methane carbon from decomposing gas-hydrate reservoirs4, 5, 6, 7. The aftermath of this rapid, intense and global warming event may be the best example in the geological record of the response of the Earth to high atmospheric carbon dioxide concentrations and high temperatures. This response has been suggested to include an intensified flux of organic carbon from the ocean surface to the deep ocean and its subsequent burial through biogeochemical feedback mechanisms8. Here we present firm evidence for this view from two ocean drilling cores, which record the largest accumulation rates of biogenic barium—indicative of export palaeoproductivity—at times of maximum global temperatures and peak excursion values of delta13C. The unusually rapid return of delta13C to values similar to those before the methane release7 and the apparent coupling of the accumulation rates of biogenic barium to temperature, suggests that the enhanced deposition of organic matter to the deep sea may have efficiently cooled this greenhouse climate by the rapid removal of excess carbon dioxide from the atmosphere.

Description: Living coelacanths (Latimeria chalumnae) are normally found only in the western Indian Ocean, where they inhabit submarine caves in the Comores Islands. Two specimens have since been caught off the island of Manado Tua, north Sulawesi, Indonesia, some 10,000 kilometres away. We sought to determine the ecological and geographic distribution of Indonesian coelacanth populations with a view to drawing up conservation measures for this extremely rare fish. During our explorations, we discovered two living Indonesian coelacanths 360 km southwest of Manado Tua.

Description: We determined the coordination environment of Zn2+ in aqueous Cl- brines at 25 °C and 300 °C using ab initio molecular dynamics simulations. The ZnCl+ and ZnCl2 complexes exist as pseudo-octahedral ZnClm(H2O)6-m clusters at 25 °C but occur as pseudo-tetrahedral ZnClm(H2O)4-m clusters at 300 °C. The ZnCl3- complex occurs as the pseudo-tetrahedral ZnCl3(H2O)- cluster at 25 and 300 °C. The tetrahedral ZnCl42- complex, however, is the dominant Zn−Cl complex at 25 °C, at least in highly concentrated (7.4 m) Cl- brines. The change in hydration number with temperature for the ZnCl+ and ZnCl2 complexes will complicate extrapolations of solvation energies to hydrothermal conditions using a Born-model-based equation of state.

Description: A SIMPLE model for continental basement structures at rifted continental margins comprises large fault blocks which trend approximately parallel to, and step down towards, the continental–ocean boundary (for example, see ref. 1). These blocks may be cut by faults which strike across the margin, and, in many theoretical discussions, are shown as being separated from the true oceanic crust by an intermediate zone (see transitional crust of Fig. 3, ref. 2). On many rifted margins these features are deeply buried by young sediments and cannot be stutied in detail. On Goban Spur (Fig. 1), a marginal plateau south-west of Ireland, the young sediment cover is abnormally thin, however, and we have been able to map in detail a 150 km wide continental basement fracture pattern of horsts and grabens using a simple seismic reflection system (160 inch3 air-gun and two-channel hydrophone array). We also suggest a location for the continent–ocean boundary between the Spur and Porcupine Abyssal Plain. There are few previously published data from Goban Spur relevant to our study, although valuable sampling3 and geophysical3–5 results have been obtained north and south of the area.

Description: Breaking waves markedly increase the rates of air–sea transfer of momentum, energy and mass. In light to moderate wind conditions, spilling breakers with short wavelengths are observed frequently. Theory and laboratory experiments have shown that, as these waves approach breaking in clean water, a ripple pattern that is dominated by surface tension forms at the crest. Under laboratory conditions and in theory, the transition to turbulent flow is triggered by flow separation under the ripples, typically without leading to overturning of the free surface15. Water surfaces in nature, however, are typically contaminated by surfactant films that alter the surface tension and produce surface elasticity and viscosity16, 17. Here we present the results of laboratory experiments in which spilling breaking waves were generated mechanically in water with a range of surfactant concentrations. We find significant changes in the breaking process owing to surfactants. At the highest concentration of surfactants, a small plunging jet issues from the front face of the wave at a point below the wave crest and entraps a pocket of air on impact with the front face of the wave. The bubbles and turbulence created during this process are likely to increase air–sea transfer.

Description: The valuable nutraceutical γ-linolenic acid (GLA, (6Z,9Z,12Z)-octadecatrienoic acid) is biosynthesized by a series of regio- and stereoselective dehydrogenation reactions that are catalyzed by a set of enzymes known as fatty acid desaturases. As part of ongoing research into the mechanism of these remarkable catalysts, we have examined the cryptoregiochemistry (site of initial oxidation) of Δ6 desaturation as it occurs in the protozoan Tetrahymena thermophila. Two complementary approaches that address this issue are described. In the first set of experiments, we measured the individual primary deuterium kinetic isotope effects associated with the C−H bond cleavages at C-6 and C-7. Competition experiments using appropriately deuterium-labeled 4-thiasubstrates revealed that a large KIE (kH/kD = 7.1 ± 0.5) was observed for the C−H bond-breaking step at C-6, whereas the C−H bond cleavage at C-7 was insensitive to deuterium substitution (kH/kD = 1.04 ± 0.05). These results point to C-6 as the site of initial oxidation in Δ6 desaturation since the first chemical step in this type of reaction is rupture of a strong, unactivated C−H bond, an energetically difficult process that typically exhibits a large KIE. This conclusion was supported by the results of our second approach, which involved locating the position of the putative diiron oxo oxidant with respect to substrate by monitoring the efficiency of oxo transfer to a series of thia fatty acid probes. Thus only a 6-thia-analogue is converted to significant amounts of the corresponding sulfoxide (9% yield). The absolute configuration of this product was determined to be S using (S)-MPAA as a chiral shift reagent. Taken together, these results point to the abstraction of the C-6 pro S hydrogen as the initial event in Δ6 desaturation as it occurs in T. thermophila.