ALBERT

Description: RECENT advances in 40Ar/39Ar dating1,2 have made it possible to date individual K-feldspar grains from Pleistocene tephra, a capability that greatly improves the reliability and temporal resolving power of the method. Here we apply these new techniques to the dating of a phonolite tephra from the East Eifel volcanic field in West Germany, which is sandwiched between loess and palaeosol (alfisol) deposits, and which was therefore erupted during the transition from a glacial to an interglacial period. Our age estimate for this transition is 215±4 kyr (1 σ), which has important implications for the marine δ18O timescale and for models of global climate change during the Pleistocene. The results show that single-grain dating can detect and compensate for the large quantities of xenocrystic contaminants which are found in many tephra deposits. This technique could be used to date the tephra layers found in marine sediment cores and the results could greatly enhance the reliability of the marine δ18O timescale for more rigorous Fourier analysis testing of the Milankovitch hypothesis.

Description: In a midoceanic region of the northeast Atlantic, patches of freshly deposited phytodetritus were discovered on the sea floor at a 4500 m depth in July/August 1986. The color of phytodetritus was variable and was obviously related to the degree of degradation. Microscopic analyses showed the presence of planktonic organisms from the euphotic zone, e.g., cyanobacteria, small chlorophytes, diatoms, coccolithophorids, silicoflagellates, dinoflagellates, tintinnids, radiolarians, and foraminifers. Additionally, crustacean exuviae and a great number of small fecal pellets, “minipellets,” were found. Although bacteria were abundant in phytodetritus, their number was not as high as in the sediment. Phytodetrital aggregates also contained a considerable number of benthic organisms such as nematodes and special assemblages of benthic foraminifers. Pigment analyses and the high content of particulate organic carbon indicated that the phytodetritus was relatively undegraded. Concentrations of proteins, carbohydrates, chloroplastic pigments, total adenylates, and bacteria were found to be significantly higher in sediment surface samples when phytodetritus was present than in equivalent samples collected at the same stations in early spring prior to phytodetritus deposition. Only the electron transport system activity showed no significant difference between the two sets of samples, which may be caused by physiological stress during sampling (decompression, warming). The chemical data of phytodetritus samples displayed a great variability indicative of the heterogeneous nature of the detrital material. The gut contents of various megafauna (holothurians, asteroids, sipunculids, and actiniarians) included phytodetritus showing that the detrital material is utilized as a food source by a wide range of benthic organisms. Our data suggest that the detrital material is partly rapidly consumed and remineralized at the sediment surface and partly incorporated into the sediment. Incubations of phytodetritus under simulated in situ conditions and determination of the biological oxygen demand under surface water conditions showed that part of its organic matter can be biologically utilized. Based on the measured standing stock of phytodetritus, it is estimated that 0.3–3% of spring primary production sedimented to the deep-sea floor. Modes of aggregate formation in the surface waters, their sedimentation, and distribution on the seabed are discussed.

Description: ROOTH proposed that the Younger Dryas cold episode, which chilled the North Atlantic region from 11,000 to 10,000 yr BP, was initiated by a diversion of meltwater from the Mississippi drainage to the St Lawrence drainage system. The link between these events is postulated to be a turnoff, during the Younger Dryas cold episode, of the North Atlantic's conveyor-belt circulation system which currently supplies an enormous amount of heat to the atmosphere over the North Atlantic region2. This turnoff is attributed to a reduction in surface-water salinity, and hence also in density, of the waters in the region where North Atlantic Deep Water (NADW) now forms. Here we present oxygen isotope and accelerator radiocarbon measurements on planktonic foraminifera from Orca Basin core EN32-PC4 which reveal a significant reduction in meltwater flow through the Mississippi River to the Gulf of Mexico from about 11,200 to 10,000 radiocarbon years ago. This finding is consistent with the record for Lake Agassiz which indicates that the meltwater from the southwestern margin of the Laurentide Ice Sheet was diverted to the northern Atlantic Ocean through the St Lawrence valley during the interval from ~11,000 to 10,000 years before present (yr BP).

Description: Food samples from 27 Buller’s mollymawks Diomedea bulleri from the New Zealand region showed that cephalopods were, by frequency of occurrence and by mass, their preferred food. Fish, crustaceans, and tunicates, in decreasing order of importance, also were taken. Seventeen species of Cephalopoda were identified by their beaks, with 78.5% of individuals belonging to the Ommastrephidae (77% Nototodarus spp.) and 10% to the Histioteuthidae. The diet was compared with that of four other small species of Diomedea, and found to be similar to that of D. chrysostoma, D. irrorata, and D. cauta, but different from that of D. melanophris, whose preferred food is euphausiids. Squid-fishing operations around New Zealand may come into competition with Buller’s mollymawk.

Description: Squid regurgitated by Greyheaded and Yellownosed Albatrosses at the Prince Edward Islands were predominantly two onychoteuthid species, Kondakovia longimana and Moroteuthis knipovitchi. Both squid are characteristic of cold, Antarctic waters and may have been caught south of the Antarctic Convergence, some 350 km to the south of the breeding station. Both albatross species regurgitated similar squid (by species and size), and these squid were similar to those found in previous studies of the diet of Wandering, Sooty and Lightmantled Sooty Albatrosses at the Prince Edward Islands

Description: The development of natural plankton populations in tanks (1000l) and in Kiel Bight is compared with special references to mechanisms affecting species composition in spring and early summer. In a first experiment, three tanks filled with surface water just prior to the bloom (February 1983) were held under different light conditions. Exponential growth coincided with onset of the growth in the field. Growth in the two darkened tanks was retarded. In the field, a bloom of mainly Thalassiosira polychorda was observed, whereas in the light tank Thlassiosira 'pseudonana' and in the two darker tanks Skeletonema costatum were the domninant species. The observed shift in species compositions between tanks and in the field can be attributed partly to differences in growth strategies of species involved but also to the specific effect of population enclosure. In a second experiment (May/ June 1983) the influence of grazing pressure was studied in two tanks with different abundance of metazooplankton. Nauplii as well as large protozoans were grazed down more rapidly than the samller phytoflagellates, which confirmed earlier hypotheses based on field observations. After decline of grazers, possibly due to starvation, a succession from bacteria to nanoflagellates and then ciliates was observed.

Description: One of the most striking features of the upper North Atlantic Ocean is an extensive layer of water with temperature close to 18°C and salinity close to 36.5‰, (ref. 1). This 18°C water is formed by winter convection in the Sargasso sea2,3, but aspects of the annual rate of 18°C water formation remain obscure4. We have simulated this water mass formation by integrating a one-dimensional model along a 4-yr trajectory of a water column circulating around the Sargasso Sea. Winter convection is deep (≥200 m) in regions where the ocean suffers a net annual heat loss to the atmosphere, and shallow (≤lOOm) where the ocean gains heat each year. The origin of the thermostad (nearly isothermal layer) is a thick layer of nearly homogeneous water subducted beneath the seasonal boundary layer in the year that the water column passes through the line dividing annual cooling from annual heating. We estimate the annual production of 18°C water to be 446,000 km3 yr−1. Downstream, more stratified central water is formed each year at a rate that depends more on Ekman pumping (wind-forced convergence) than on the decreasing depth of winter convection

Description: Long-term investigations of pore-water ammonium concentrations and sediment oxygen uptake were carried out in three different sediment types along a slope in Kiel Bight. The inverse relation between mineralization rates and ammonium concentrations at the three stations is explained by the differences in the role of various mechanisms transporting nutrients out of the sediments. Direct water exchange due to turbulent or density driven processes, bioturbation and pumping activity of benthic macrofauna and molecular diffusion are involved to various extents in nutrient fluxes out of the sediments studied. The role of different sediment types in the interaction with the pelagic system is discussed in a conceptual framework of pelagic system functioning in Kiel Bight.

Description: The publications of Matsuoka (1983) and Bujak (1984) on dinoflagellate cysts from the Neogene of Japan and the Paleogene‐Neogene of the Bering Sea‐northern North Pacific areas, respectively, resulted in the erection of two new species by each author which are synonymous. Impagidinium pacificum Bujak and Spiniferites ovatus Bujak are therefore designated junior synonyms of Impagidinium japonicum Matsuoka and Spiniferites hexatypicus Matsuoka. Another species, Spiniferites ovatus Matsuoka, does not occur in the material examined by Bujak. Specimens assigned by Matsuoka to Nematosphaeropsis labyrinthea and Tectatodinium pellitum are reassigned to Nematosphaeropsis lemniscata Bujak and Filisphaera filifera Bujak, respectively. The species Reticulatosphaera stellata Matsuoka, which Matsuoka designated the type species of his new genus Reticulatosphaera, is designated a subjective junior synonym of a species originally named by Benedek (1972) as Cleistosphaeridium actinocoronatum. C. actinocoronatum is transferred to Reticulatosphaera and becomes the type‐species of this genus. Specimens assigned to Areoligera senonensis Lejeune‐Carpentier sensu Gocht 1969 by Matsuoka (1974, 1983) and Tanyosphaeridium fusiform by Matsuoka (1974) are reattributed to Systematophora ancyrea and Distatodinium fusiforme (Matsuoka) comb, nov., respectively. Bujak also erected eight Eocene to Pleistocene concurrent‐range zones, two of which were named the I. pacificum and Spiniferites ovatus Zones. These are renamed the I. japonicum and 5. hexatypicus Zones, and the zonation is modified to extend the Trinovantedinium boreale Zone into the early Oligocene, and to restrict the S. hexatypicus Zone to the Miocene.

Description: Morphological characteristics of two large females of Haliphron atlanticus STEENSTRUP (= Alloposus mollis VERRILL) are described and illustrated. The soft and gelatinous body, the shape of the mantle aperture, the formation of the funnel and adhesive apparatus, and the straplike septa connecting the mantle and funnel and containing the stellate ganglion are characteristic features of the species. One specimen, weighing 41 kg after fixation, was found dead near Bergen (60°14′ N, 5°16′ E) in May 1983. The other, weighing 25 kg after being frozen, was caught alive at 210 m off Vestvägöy in the Lofoten archipelago (68°20′ N. 14°14′ E) in November 1984. It was possibly feeding on the prawn, Pandalus borealis KRøYER. Both specimens had arms partly missing and web torn, but were otherwise well preserved. Previous records of H. atlanticus are confined to tropical and warm-temperate areas. The present findings represent the first records from north of 42° N.

Description: This check-list is a compilation of the marine molluscs recorded from Norway and the abyssal depths of the Norwegian Sea. Molluscs not recorded from the Norwegian fauna but found on the North Sea plateau, the British North Sea coast, the Swedish west coast, and in Danish waters are also included. Distributional data are provided for each species. Most commonly used synonyms are listed, together with type species for each accepted generic name. Systematical code numbers are included for easy retrieval of information. An alphabetical index of all generic names mentioned concludes the check-list. Recent taxonomic alterations and all distributional records are documented by literature references.