Abundance of copepods from multinet samples during POLARSTERN cruise ANT-XX/1

Abundance and species composition of copepods were studied during the expedition ANT XXI/1 on a latitudinal transect in the eastern Atlantic from 34°49.5' N to 27°28.1' S between 2-20 November 2002. Stratified zooplankton tows were carried out at 19 stations with a multiple opening-closing net between 300 m water depth and the surface. Cyclopoid and calanoid copepods showed similar patterns of distribution and abundance. Oithona was the most abundant cyclopoid genus, followed by Oncaea. A total of 149 calanoid copepod species were identified. Clausocalanus was by far the most abundant genus, comprising on average about 45% of all calanoids, followed by Calocalanus (13%), Delibus (9%), Paracalanus (6%), and Pleuromamma (5%). All other genera comprised on average less than 5% each, with 40 genera less than 1%. The calanoid copepod communities were distinguished broadly in accordance with sea surface temperature, separating the subtropical from the tropical stations, and were largely determined by variation in species composition and species abundance. Nine Clausocalanus species were identified. The most numerous Clausocalanus species was C. furcatus, which on average comprised half of all adult of this genus. C. pergens, C. paululus, and C. jobei, contributed an average of 19%, 9%, and 9%, respectively. The Clausocalanus species differed markedly in their horizontal and vertical distributions: C. furcatus, C. jobei, and C. mastigophorus had widespread distributions and inhabited the upper water layers. Major differences between the species were found in abundance. C. paululus and C. arcuicornis were biantitropical and were absent or occurred in very low numbers in the equatorial zone. C. parapergens was found at all stations and showed a bimodal distribution pattern with maxima in the subtropics. C. pergens occurred in higher numbers only at the southern stations, where it replaced C. furcatus in dominance. In contrast to the widespread species, the bulk of the C. paululus, C. arcuicornis, C. parapergens, and C. pergens populations was concentrated in the colder, deeper water layers below the thermocline, thereby avoiding the warm surface waters. C. lividus was found only at the most northern and C. ingens only at the most southern stations. Both species were found almost exclusively in the upper 50 m. The distinct differences in abundance and horizontal and vertical distribution suggest a strong ecological differentiation among the Clausocalanus species.

Age model and ostracod countings from IODP Site 306-U1314

We present a detailed study of glacial/interglacial deep sea benthic ostracod assemblage variability at IODP Site U1314 (subpolar North Atlantic) in relation to the history of ice-rafting events and changes in deep ocean circulation over the past 170 ky. Our records of ostracod diversity, abundance and dissolution and sediment properties (IRD and CaCO3) show an excellent correspondence to high amplitude orbital and millennial variability observed in the climate records (d13C and d18O) from neighboring deep water sites, suggesting that the benthic meiofauna fluctuates synchronously with the prevailing oceanographic conditions (surface ocean conditions, deep ocean circulation and water temperature and food flux). Krithe (dominant), Argilloecia and Cytheropteron are the most abundant and diverse genera in association with Rockallia enigmatica. Three ostracod assemblages are recognized. The genera Pennyella, Argilloecia, Pelecocythere, Ambocythere, Pseudobosquetina, Bradleya and Nannocythere are associated with interglacials and interstadials, and possibly reflect increased flux of food to the sediments and more vigorous NADW formation. A transitional assemblage composed of species of Cytheropteron, Xestoleberis and Eucythere is restricted to climatic transitions and indicate moderate environmental conditions and seasonal productivity. A glacial/stadial assemblage is characterized by a temporal predominance of either intermediate-depth and shallow water Arctic/subarctic species (belonging to Cytheropteron, Polycope, Pedicythere, Swainocythere, Cluthia, Heterocyprideis, Elofsonella and Finmarchinella) or abyssal North Atlantic ostracods (Bythocythere, Dutoitella, Bathycythere and Bythocypris). The influx of high latitude taxa can be partially explained by ice-rafting, but may also represent a shift of the location of intermediate and deep water convection to the area south of Iceland. Therefore the combination of species characteristic of different watermasses during glacials may reflect shifts in the influence of high nutrient southern source water (e.g. AABW) vs. low nutrient GNAIW during glacials.

Pollen distribution of sediment core MD96-2048 from the Western Indian Ocean

Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ~120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka.

Distribution of microorganisms in recent sediments of Kiel Bay

Die angewandte Mikropaläontologie bestimmt heute im wesentlichen das Alter eines Gesteins mit Hilfe von Faunenvergesellschaftungen. Aus der Zusammensetzung der Fauna, aus dem Einsatz oder Fehlen bestimmter Gattungen und Arten, aus den Mineralien, die das Gestein aufbauen, aus dem ganzen Bild, das eine aus einem Gestein herausgeschlämmte Fauna dem Bearbeiter gibt, läßt sich das Alter dieses Gesteins festlegen. Will man aber verschiedene Bohrungen, vor allem auch räumlich weit voneinander getrennter Gebiete, miteinander parallelisieren, so liegt das Kernproblem der Mikropaläontologie in der Frage, ob es sich bei verschiedenen Faunen tatsächlich um Alters- oder nur um Faziesunterschiede handelt. Da die Grundlagen der mikropaläontologischen Arbeitsweise zum weitaus größten Teil auf den Ergebnissen von Untersuchungen fossiler Faunen beruhen, müssen zu ihrer Unterbauung Untersuchungen an recentem Material folgen. Besonders spielt das Ineinandergreifen mariner und brackischer Sedimente in der angewandten Mikropaläontologie eine große Rolle. Auf Grund der Tatsache, daß ein großer Teil von Gattungen und Arten der Foraminiferen an der Wende Kreide/Tertiär ausstirbt und neue an ihre Stelle treten, stellt Glässner (1948) die Behauptung auf, daß die aktualistisch gewonnenen Ergebnisse für vortertiäre Faunen nur eine geringe Bedeutung besitzen. Auch seien vortertiäre, brackische Foraminiferen nicht bekannt (Glässner 1948, S. 191). Hiltermann (1948) konnte aber bereits im nordwestdeutschen Malm brackische, d. h. in Brackwasser eindringende Foraminiferen nachweisen. Auf jeden Fall behalten aktualistische Unterlagen ihren Wert für das Tertiär und Quartär. Die Faunen, die in recenten, brackischen Sedimenten nebeneinander auftreten, sind in einem Bohrprofil in einem Gestein übereinander zu erwarten. Gelingt es, die Beziehungen einer recenten Fauna zu ihrer Umwelt zu klären, dann können umgekehrt aus fossilen, ihnen gleichen oder ähnlichen Faunen Rückschlüsse auf die Entstehungsbedingungen von Gesteinen gezogen werden. Unter Umständen können der Verlauf einer Transgression, Küstennähe, die Höhe des Salzgehaltes des Meerwassers, die vorherrschenden Temperaturen u. a., aus ihnen abgelesen werden. Die Ostsee ist ein klassisches Brackwassergebiet der Erde. Ihr westlicher Teil, die Kieler Bucht, wurde erst in jüngster geologischer Zeit vom Meer überflutet. Nach Tapfer (1940) begann hier die flandrische Transgression erst etwa um 7500 v. d. Zw. mit dem Erreichen des heutigen Meeresniveaus. Seit dieser Zeit erst entstehen neue Küstenformen, wird der Meeresboden umgelagert und bilden sich marine und brackische Absätze in diesem Gebiet.

Pollen and spores of sites GeoB8331 and GeoB8323, Namaqualand Mudbelt, Holocene South Africa

To better understand Holocene vegetation and hydrological changes in South Africa, we analyzed pollen and microcharcoal records of two marine sites GeoB8331 and GeoB8323 from the Namaqualand mudbelt offshore the west coast of South Africa covering the last 9900 and 2200 years, respectively. Our data corroborate findings from literature that climate developments apparently contrast between the summer rainfall zone (SRZ) and winter rainfall zone (WRZ) over the last 9900 years, especially during the early and middle Holocene. During the early Holocene (9900-7800 cal.yr BP), a minimum of grass pollen suggests low summer rainfall in the SRZ, and the initial presence of Renosterveld vegetation indicates relatively wet conditions in the WRZ. Towards the middle Holocene (7800-2400 cal. yr BP), a rather moist savanna/grassland rich in grasses suggests higher summer rainfall in the SRZ resulting from increased austral summer insolation and a decline of fynbos vegetation accompanied by an increasing Succulent Karoo vegetation in the WRZ possibly suggests a southward shift of the Southern Hemisphere westerlies. During the last 2200 years, a trend towards higher aridity was observed for the SRZ, while the climate in the WRZ remained relatively stable. The Little Ice Age (ca. 700-200 cal. yr BP) was rather cool in both rainfall zones and drier in the SRZ while wetter in the WRZ.