ALBERT

Description: WHILE ammonites and all other ectocochleate cephalopods became extinct, nautiloids survived relatively unchanged from the Ordovician, suggesting that they are unusually well adapted to their niche. Here we obtain high-resolution tracks of Nautilus positions and depths, combined with telemetered jet pressures, which clarify both its lifestyle and economics. Nautilus is more active in nature than in captivity1, but its energy costs are lower than projected2,3. Viewing Nautilus as 'vertic', rather than benthic, resolves this contradiction. Records show that the cost of transport is the same in any direction within a vertical plane. Living on a reef face swept by a lateral current means that vertical movements4,5 sample large areas for chemical trails. A detected trail can be followed upcurrent in the slow-moving boundary layer, but no effort is wasted on horizontal movement without good prospects for food; long-range movements are downcurrent and made by drifting. Once fed, a Nautilus can reduce its energy costs by moving to deeper, cooler waters, where a single meal can last for months.

Description: Scattered groups of these ancient fish may all stem from a single remote population. Coelacanths were discovered in the Comoros archipelago to the northwest of Madagascar in 1952. Since then, these rare, ancient fish have been found to the south off Mozambique, Madagascar and South Africa, and to the north off Kenya and Tanzania — but it was unclear whether these are separate populations or even subspecies. Here we show that the genetic variation between individuals from these different locations is unexpectedly low. Combined with earlier results from submersible and oceanographic observations1, 2, our findings indicate that a separate African metapopulation is unlikely to have existed and that locations distant from the Comoros were probably inhabited relatively recently by either dead-end drifters or founders that originated in the Comoros.

Description: There has been concern about recent temperature trends and the future effects of CO2 concentrations in the atmosphere1,2; but instrumental records only cover a few decades to a few centuries and it is essential that proxy data sources, such as pollen spectra from peats and lake sediments, be carefully interpreted as climate records. Several workers have shown statistically significant associations between the modern pollen rain and climatic parameters, an approach that by-passes the recognition of pollen/vegetation units. Statistically defined equations that associate abiotic and biotic elements are called transfer functions. We report here on the application of transfer function equations to nine middle and late Holocene peat and lake sediment sequences from northern Canada (Fig. 1).

Description: THE vestimentiferan tubeworm Riftia pachyptila is found around hydrothermal vent areas in the deep sea. Intracellular bacterial chemoautotrophic symbionts use the oxidation of sulphide from the effluent of the vents as an energy source for CO2 fixation. They apparently provide most or all of the nutritional requirements for their gutless hosts1–5. This kind of symbiosis has since been found in many other species from various other phyla from other habitats6–9. Here we present results that the bacteria of R. pachyptila may cover a significant fraction of their respiratory needs by the use of nitrate in addition to oxygen. Nitrate is reduced to nitrite, which may be the end product (nitrate respiration)10 or it may be further reduced to nitrogen gas (denitrification)11. This metabolic trait may have an important role in the colonization of hypoxic habitats in general by animals with this kind of symbiosis.

Description: Alfred Wegeners Notizbuch "Kontinental-Verschiebungen" : eine Einführung / von Reinhard Krause und Jörn Thiede: 2005 jährt sich der Geburtstag Alfred-Wegeners zum 125. Mal (geboren 1. November 1880). Bei den Vorbereitungen auf dieses Jubiläum und auf die Feier des 25- jährigen Bestehens der Stiftung Alfred-Wegener-Institut für Polar- und Meeresforschung sind die Unterlagen, die auf Alfred Wegener persönlich zurückgehen, sorgfältig durchgesehen worden. Bei seinem Enkel Dr. Günther Schönharting in Eichhofen / Bayern wurden zwei wichtige Dokumente aufgefunden, nämlich ein umfangreiches Notizbuch mit dem Wort „Kontinental-Verschiebungen“ beschriftet und die erste Auflage seines Buches „Die Entstehung der Kontinente und Ozeane“ (erschienen im Jahr 1915), das mit Leerseiten durchschossen gebunden war, und in dem sich zahlreiche schriftliche Verbesserungen befanden, die in die Gestaltung späterer Auflagen eingingen. Da das Notizbuch „Kontinental-Verschiebungen“ mit seinen zahlreichen Exzerpten und Vermerken ein wertvolles Dokument darstellt, ohne das die wissenschaftliche Auseinandersetzung Alfred Wegeners mit seiner eigenen Hypothese nur schwierig nachzuvollziehen ist, haben wir uns entschieden, dieses Notizbuch zu transkribieren und gemeinsam mit seinem Faksimile in diesem Heft zu veröffentlichen. Möge diese Veröffentlichung eine anregende Quelle für wissenschaftsgeschichtlich interessierte Forscher darstellen!

Description: The results of seismic studies in the near-shore, shallow waters of the south-western Kara Sea - at the Shpindler, Kharsavey and Mare-Sale sites - showed the presence of a seismic interface which can be interpreted as a submarine permafrost table. The proposed permafiost exhibits a continuous distribution and a strongly dissected top surface overlain by unfrozen sediments. The permafrost table is located at a depth of 4-6 m and 5-10 m below the sea floor at the Shpindler and Mare-Sale sites, respectively. Three dimensional modeling of the permafrost table suggests the presence of relict buried thermodenudational depressions (up to 2 km across) at a minimum sea depth of 40-45 m at the Shpindler and Mare-Sale sites. The depressions may be considered as paragenetic to thermocirques found in cliffs at the Shpindler site. At the Kharasavey site, the permafrost table has an elongated depression parallel to the modern shoreline. The maximum depression depth is 20 m below the seafloor. At present, the relict therrnocirques (Shpindler and Mare-Sale) and the elongated depression (Kharasavey) are completely filled in with sediment and are not evident in modern bottom topography.

Description: During the last decade detailed coastal studies along the Arctic Seas have been conducted within the frame of the Arctic Coastal Dynamics (ACD) Program. The results indicate that shore dynamics play an important role in the balance of sediment and organic carbon in the Arctic basin. Arctic coastal sediment flux exceeds river sediment discharge and other terrestrial sediment sources. Based on newly obtained data, this presentation evaluates average coastal erosion rates as well as sediment and organic fluxes within the Siberian Arctic coastal Zone. The Siberian Arctic sector includes four seas: the Kara, Laptev, East Sibesian and Chukchi Seas. The total length of the Siberian Arctic coastline, including the islands, is about 29,500 km. Most parts of this coast are characterized by very active coastal erosion processes. A considerable proportion of the Siberian Arctic coasts (especially for the Laptev and East Siberian Seas) consists of ice-rich permafrost deposits, which are rapidly reworked by sea erosion. It has been found that the coastal sediment flux into the seas listed above plays a dominant role in their sediment budget. Based on the amount of coastal sediment released to the sea and the average organic carbon contents of the key types of coastal deposits, the total organic carbon (TOC) supplied to the Siberian Arctic Seas (SAS) has been estimated. The assessment of these lithologic-dynamic Parameters is based On unified methods, which involve detailed coastal segmentation and GIS-analyses. The calculated values of the sediment and TOC fluxes are considerably different from previously published data. Our results suggest that both coastal sediment flux (158 million tons per year) and coastal TOC flux (4.6 million tons per year) to the SAS significantly contribute to the Arctic Ocean sediment and carbon budget. This study was supported by the INTAS (grant 01 - 2329).

Description: Under the framework of the Arctic Coastal Dynamics (ACD) program two projects of the International Association for the Promotion of Co-operation with Scientists from the New Independent States of the Former Soviet Union (INTAS) focused on ACD related topics. The objectives of the first project "Arctic coastal dynamics of Eurasia: classification, modern state and prediction of its development based on GIS technology" (2002-2004) had been to develop a coastal classification and to generate GIS based map products for the coastal Zone of the Eurasian Arctic. The Russian Part of the circum-Arctic ACD classification and segmentation has been completed within this project. The overall objective of the second project "Arctic coasts of Eurasia: dynamics, sediment budget and carbon flux in connection with permafrost degradation" (2002-2005) is to quantify the material flux through coastal erosion in order to improve our understanding of the Arctic sediment and organic carbon budget. This presentation summarizes the main results of the two projects and provides an overview of more specific results which are shown in a series of Posters.

Description: In the context of gradual Cenozoic cooling, the timing of the onset of significant Northern Hemisphere glaciation 2.7 million years ago is consistent with Milankovitch's orbital theory, which posited that ice sheets grow when polar summertime insolation and temperature are low. However, the role of moisture supply in the initiation of large Northern Hemisphere ice sheets has remained unclear. The subarctic Pacific Ocean represents a significant source of water vapour to boreal North America, but it has been largely overlooked in efforts to explain Northern Hemisphere glaciation. Here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic Pacific Ocean, indicating that 2.7 million years ago late-summer sea surface temperatures in this ocean region rose in response to an increase in stratification. At the same time, winter sea surface temperatures cooled, winter floating ice became more abundant and global climate descended into glacial conditions. We suggest that the observed summer warming extended into the autumn, providing water vapour to northern North America, where it precipitated and accumulated as snow, and thus allowed the initiation of Northern Hemisphere glaciation.

Description: THE supply of dissolved inorganic carbon (DIC) is not considered to limit oceanic primary productivity1, as its concentration in sea water exceeds that of other plant macronutrients such as nitrate and phosphate by two and three orders of magnitude, respectively. But the bulk of oceanic new production2 and a major fraction of vertical carbon flux is mediated by a few diatom genera whose ability to use DIG components other than CO2, which comprises 〈 1% of total DIC3, is unknown4. Here we show that under optimal light and nutrient conditions, diatom growth rate can in fact be limited by the supply of CO2. The doubling in surface water pCO2 levels since the last glaciation from 180 to 355 p.p.m.5,6 could therefore have stimulated marine productivity, thereby increasing oceanic carbon sequestration by the biological pump.

Description: Analysis of aeolo-marine dust deposits in the subtropical eastern Atlantic enables the strength of the major wind patterns during the late Quaternary to be evaluated and gives an insight into the climate of North Africa.

Description: Sexual mimicry among animals is widespread, but does it impart a fertilization advantage in the widely accepted ‘sneak–guard’ model of sperm competition? Here we describe field results in which a dramatic facultative switch in sexual phenotype by sneaker-male cuttlefish leads to immediate fertilization success, even in the presence of the consort male. These results are surprising, given the high rate at which females reject copulation attempts by males, the strong mate-guarding behaviour of consort males, and the high level of sperm competition in this complex mating system

Description: The tropics have been suggested as the drivers of global ocean and atmosphere circulation and biogeochemical cycling during the extreme warmth of the Cretaceous period1, 2; but the links between orbital forcing, freshwater runoff and the biogeochemistry of continental margins in extreme greenhouse conditions are not fully understood. Here we present Cretaceous records of geochemical tracers for freshwater runoff obtained from a sediment core off the Ivory Coast that indicate that alternating periods of arid and humid African climate were driven by orbital precession. Our simulations of the precession-driven patterns of river discharge with a global climate model suggest that ocean anoxia and black shale sedimentation were directly caused by high river discharge, and occurred specifically when the northern equinox coincided with perihelion (the minimum distance between the Sun and the Earth). We conclude that, in a warm climate, the oceans off tropical continental margins respond rapidly and sensitively to even modest changes in river discharge.