ALBERT

Description: In both terrestrial and aquatic environments introductions of non-indigenous species are continuing and represent one important component of global change. Negative biotic interactions by resident species may prevent successful invaders from becoming pests. Few experimental data are available on the presence and significance of such biotic resistance other than predation or competition. This study addresses the role of habitat structure provided by a native eelgrass (Zostera marina) canopy on growth and survival of the non-indigenous mussel Musculista senhousia, a habitat-modifying gregarious suspension feeder with strong effects on native infauna and eelgrass. In 2 southern California bays, a series of transplantation experiments using tagged mussels revealed that inside an eelgrass canopy, Musculista growth rates were reduced by more than half in 3 of 4 experiments compared to adjacent unvegetated areas. Musculista survival also decreased inside the vegetation in a 4-mo experiment. As one element of habitat structure, we tested the effects of eelgrass patch size, using natural (1 site) and planted (1 site) eelgrass patches of defined sizes. Growth rates of Musculista were highest outside the vegetation and decreased as eelgrass patch size increased. As a potential mechanism for the canopy effects, we suggest that Musculista receives less food inside the vegetation. In the experimental plots, the presence and spatial extent of the macrophyte canopy strongly affected near bottom (10 cm) horizontal water flow assessed with a direct dye tracking method. Reduced mussel growth rates were linearly associated with lower water flow, and presumably, food flux. Over a period of 7 mo, food resources (particulate chlorophyll a) were consistently lower 1 and 5 cm above the sea floor inside eelgrass patches compared to the sand flat. The reduction in food availability matched the growth reduction of Musculista. Also, mussel condition (dry flesh mass/shell mass) was worse in individuals growing in eelgrass than in the sand flat. Previous experiments revealed that dense beds of Musculista impede the rhizome growth and vegetative propagation of eelgrass, yet mussels attain abundances sufficient for interference only if eelgrass beds are patchy. Thus, anthropogenic disturbances on eelgrass beds, which often result in meadow fragmentation, and the proliferation of Musculista may have synergistic negative effects on the persistence of eelgrass beds.

Description: The global sediment mass-age distribution indicates large variations in the rates of carbonate sedimentation through time. The largest mass of carbonate deposited during the entire history of the earth was produced during the Cambrian, possibly following on an episode of phosphogenesis in the Late Precambrian. A second major episode occurred during the Late Devonian, probably reflecting the invasion of land by plants that altered the rock-weathering and soil-forming regimes. Other lesser pulses of carbonate deposition occurred in the Late Permian, Triassic, and Cretaceous. A shift in the locus of carbonate deposition from shallow waters to the deep sea occurred during the Cretaceous.

Description: In situ experiments were run with the seastar Asterias rubens to investigate the influence of epibiosis on predation preferences. Mussels (Mytilus edulis) monospecifically fouled by different epibiont species (the barnacle Balanus improvisus, the red filamentous alga Ceramium strictum, the sponge Halichondria panicea and the hydrozoan Laomedea flexuosa) and macroscopically clean mussels were exposed and seastar predation was monitored by SCUBA. Asterias rubens preferred macroscopical unfouled mussels as prey. Fouling generally reduced predation pressure on the mussel hosts (associational resistance). Barnacles protected mussels less efficiently than hydrozoans or algae. We hypothesize that in top-down controlled communities this influence of epibiosis on predation pressure should affect mussel community patterns. A survey of natural mussel-epibiont distribution in the presence or absence of A. rubens showed that the prevalence of differently fouled mussels differed between predation-exposed and predation-protected habitats. Natural mussel-epibiont associations reflected the preferential predation of the major local predators. Additionally, higher epibiotic diversity and evenness could be observed at locations accessible to benthic predators as compared with habitats protected from predation. As blue mussels and seastars are important structuring and controlling elements in the shallow water community of Kiel Fjord, major consequences of epibiosis on the entire system are discussed.

Description: At Aqaba in the Northern Gulf of Aqaba, Red Sea, the stable oxygen isotope record of a Por#es lutea coral colony was studied. From a vertical and a horizontal core two parts from the base of the colony (10 years of coral growth), and two parts from the living surface (12 years of coral growth) were analysed with a monthly sampling resolution. The results show that seasonality of sea surface temperatures (SST) in the northem GulfofAqaba has increased since the early 19th century, mainly due to higher summer temper- atures. 8~80-ratios indicate that SST increased by at least 1.3~ Horizontal and vertical cores display dif- ferent variations in the modern parts, probably caused by the very shallow water depth of the youngest part of the vertical core.

Description: Repeatable species dominance patterns across nutrient ratio gradients are found both in culture competition experiments and in natural waters. However, the mechanisms behind these similar patterns need not to be identical. In chemostat experiments, such patterns are caused by the two-way competitive interactions between contemporaneously occurring organisms. Nutrient competition may be important in situ too, but there is an additional effect of early successional species influencing the nutrient environment for later successional species, without being influenced themselves by their successors.

Description: Cyanobacteria are important constituents of most aquatic ecosystems on earth, and planktonic forms frequently show mass development in lakes and estuaries. Despite extensive scientific efforts directed towards research on cyanobacteria, a comprehensive theory explaining their success is lacking. Because cyanobacteria comprise a diverse group of organisms, it is concluded that any analysis of the conditions leading to cyanobacterial dominance in pelagic ecosystems should consider at least three different subgroups, classified based on presence or absence of (i) buoyancy regulation and (ii) the ability to fix molecular nitrogen. In this review, nine single-factor hypotheses regarding regulation of cyanobacterial development are examined against the background of physiological and ecological characteristics of these organisms. Special emphasis has been put on understanding differences in nitrogen metabolism between cyanobacteria and algae which directly relate to a hypothesis conceming inorganic nitrogen forms and cyanobacterial success previously presented by our research group. The review lends support to the theory that cyanobacteria have a low competitive ability for nitrate compared with algae and a high ability to compete for ammonium, particularly under nitrogen-limiting conditions. Finally it is concluded that to understand cyanobacterial devlopment and how high Standing Stocks in pelagic ecosystems are maintained requires parts o f all the single-factor hypotheses initially presented.

Description: The density of seawater is a complex function of temperature, salinity, and pressure. Because of the non-linearity of the equation of state of seawater, the densities of sea waters having the same temperature and the same salinity differences (with respect to the mean salinity of the ocean) will vary with the mean salinity of the ocean. Although this strange property of seawater is evident in a plot of the equation of state, it has never been considered in trying to reconstruct ancient ocean circulation. These differences in the density field may have caused the ocean to respond differently to atmospheric forcing in the past. The different response may hold the key to understanding "ocean anoxic events" and episodes of large-scale burial of organic carbon and production of petroleum source rocks.

Description: The Late Cretaceous was much warmer than today. There was no significant ice at high latitudes, meridional thermal gradients were low, and continental interiors remained warm during winter. Late Cretaceous atmospheric C02 concentrations were about four times greater than today and an enhanced "greenhouse" effect contributed to the overall warmth of the Late Cretaceous. However , increases in atmospheric C02 tend to increase temperatures at all latitudes and do not explain the very low thermal gradients recognized in the geologic record. Increased poleward ocean heat transport has been cited as a mechanism for maintaining low meridional thermal gradients during the Cretaceous. However , ocean heat transport values larger than the present day are difficult to reconcile. In addition, low meridional thermal gradients suggest sluggish atmospheric circulation, implying that the advection of heat from the warm oceans into the continental interiors was limited. In general, paleoclimate simulations using Atmospheric General Circulations Models (AGCMs) have not been successful in simulating the low meridional thermal gradients and warm winter continental interiors of the Cretaceous, forcing the concept of "equability" to be questioned. Until recently, the physical effects of vegetation on pre-Quaternary climates have largely been ignored. Terrestrial ecosystems influence global climate by affecting the exchange of energy, water, and momentum between the land surface and the atmosphere. In a new approach to pre-Quaternary paleoclimate modeling, Campanian (80 Ma) climate and vegetation have been simulated using a global climate model (GENESIS Version 2.0), coupled to a predictive vegetation model (EVE), resulting in a realistic simulation of Late Cretaceous climate. The predicted distribution of Late Cretaceous vegetation played an important role in the maintenance of low meridional thermal gradients, polar warmth, and equable continental interiors. High latitude forests reduced albedo, especially during snowcovered months, and increased net surface radiation and latent heat flux.

Description: The use of stable isotope analysis in ecological and wildlife studies is rapidly increasing. Studies include evaluating flow of nutrients in ecosystems and studying dietary composition of individual animals. Several mixing models have been developed to evaluate the relative contribution of different foods to the diet of consumers. All these mixing models require that all prey types will be significantly different in bivariate space. This requirement usually poses a problem in analyzing data of stable isotope ratios because sample sizes in most studies are small and seldom normally distributed. We propose a randomization test that we based on the K nearest-neighbor approach. Results from our simulations of power revealed that the K nearest-neighbor test appears to have high power even with small sample sizes and comparatively low displacement. The K nearest-neighbor test described here provides the preliminary statistical analysis necessary for the use of the mixing models, and therefore is a new, powerful tool for analyzing stable isotope data. In evaluating the test performance on data collected from American martens (Martes americana) and their prey on Chichagof Island, Southeast Alaska, we were able to reject our null hypothesis that all samples of prey were drawn from identical populations (P = 0.05). A program written in Pascal or S-Plus is available from the authors to evaluate the K nearest-neighbor statistic for several groups.

Description: Newly hatched Baltic cod Gadus morhua larvae are typically found at depths 〉60 m. This is a region of low light and prey availability, hence generating the hypothesis that larvae have to migrate from hatching depth to the surface layer to avoid starvation and improve their nutritional condition. To test this hypothesis, Baltic cod larvae were sampled during the spawning seasons of 1994 and 1995 with depth-resolving multiple opening/closing nets. Each larva was aged by otolith readings and its RNA/DNA ratio was determined as a measure of nutritional condition. The RNA/DNA ratios of these larvae aged 2-25 days (median 10 days) ranged from 0.4 to 6.2, corresponding to levels exhibited by starving and fast-growing larvae in laboratory calibration studies (starvation, protein growth rate, Gpi= -12.2% day−1; fastgrowing larvae, Gpi=14.1%day−1) respectively. Seventy per cent of the field caught larvae had RNA/DNA ratios between the mean values found for starving and fed laboratory larvae. Only larvae aged 8-11 days had higher mean RNA/DNA ratios above 45 m than below (t-test, P〈0.05). However, the instantaneous protein growth rates were significantly higher for all larval age groups in the surface layers (t-test, P〈0.05). Starving larvae were found in all depths sampled (10-85 m), whereas growing larvae (positive Gpi) were restricted to samples taken shallower than 45 m. These superior growth rates above 45 m corroborate the hypothesis and imply that migration to the shallow water layers is a prerequisite for good nutritional condition, growth and survival of Baltic cod larvae. The frequent occurrence of cod larvae older than 8 days in the deep water in poor condition suggests that a proportion of the larvae will die from Starvation in the deep layers of the Baltic Sea.

Description: This paper presents trace element and Sm-Nd isotope data on the Mönchalpgneiss in order to compare the geochemistry of the two polymetamorphic igneous suites that comprise over 30% of the Austroalpine Silvretta nappe. The first are the so-called "Younger Orthogneisses" of the "Fliielagranitic Association" and the second are the "Older Orthogneisses" including the Mönchalpgneisswhich are associated with metagabbros, metadiorites, metatonalites and metagranitoids. U-Pb zircon results from the Mönchalpgneiss are indicative of anatectic processes in late Cambrian to Ordovician times. A volcanic-arc (VA) tectonic environment during intrusion explains the direct association of gabbroic and metagranitoid rocks in the Engadine area. This model is in line with the distribution of major, trace and rare earth elements in these anatectic rocks. However, the significance of the geochemical results remains ambiguous, since the average continental crust and paragneisses of the Silvretta also show VA-type signatures in the respective diagrams. Nd model ages on four Mönchalpgneiss whole-rock samples from the type locality are closely grouped around 1.70 Ga, which is a commonly obtained value for European continental crust. This age is interpreted to be the result of a homogeneous mixture of different crustal components

Description: Abstract The famous association of metagabbros, eclogites, glaucophanites, jadeite rocks and ultramafics from the island of Syros forms a distinct lithostratigraphic or tectonic unit. It is interpreted as a high-pressure metamorphic ophiolite suite. This paper provides geochemical and Sr-isotope constraints on the geotectonic setting in which the magmatic protoliths of the Syros metabasites were formed. A compositional gap exists between the metagabbros with Mg-numbers [Mg# = Mg/(0.85Fetot + Mg) atomic ratio] of 0.75-0.88 on the one hand and eclogites and garnet-glaucophanites on the other hand with Mg# of 0.35-0.62, and maximum total iron contents of up to 18 wt.% FeOtot. Metagabbros from various localities and glaucophanites collected around Manna form geochemically coherent groups with smooth correlations between compatible as well as immobile incompatible elements and Mg#. By contrast, the behaviour of immobile incompatible elements, and to some extent also of compatible elements, is highly unsystematic in the eclogites and garnet-glaucophanites. Also, the more mobile elements display a wide scatter in all rocks. This, in conjunction with the unsystematic variation of Sr-isotopes, is thought to be due to secondary alteration. From the strong correlation of Ni and Cr with Mg# and the flat REE patterns lacking Eu-anomalies, a cumulus nature is inferred for olivine, clinopyroxene, and spinel, associated with intercumulus formation of plagioclase in the magmatic protoliths of the metagabbros. There is no direct genetic link between these rocks and the precursors of the Manna-type glaucophanites with REE characteristics typical of N- to T-type MORB. The extremely high geochemical diversity of the eclogites and garnet-glaucophanites from Syros favours individual evolution of their protoliths in small magma bodies as suggested for superferric eclogites from the Western and Ligurian Alps, as well as the ferrogabbros from the ophiolites of the Northern Apennines. From the geochemistry of the Syros metabasites along with the initial 87Sr/86Sr ratios of the metagabbros between 0.7031 and 0.7033, as well as an eNd value of 7.7 from a garnet glaucophanite, the magmatic protoliths are inferred to have formed in a back-arc setting. By analogy to the association of gabbros and ferrogabbros adjacent to the Atlantis II fracture zone of the SW Indian Ridge, we further suggest an origin at a spreading ridge in proximity to a transform fault.

Description: Evolution of the Caribbean Plate can be modeled by motions about six successive rotation poles. Opening of Cayman Trough has occurred since 49.5 Ma through westward motion of the Caribbean Plate, eastern Greater Antilles and Chortis Block. Before 49.5 Ma, the eastern Greater-Antilles were west of Cuba, and the southeastern margins of Yucatan and the Nicaragua Rise (Chortis) were aligned. From 67.5 to 49.5 Ma the Caribbean Plate rotated clockwise, opening the Yucatan Basin. From 100 Ma to 67.5 Ma, the Caribbean Plate, with Cuba attached, moved along the southeastern margin of Yucatan-Chortis. At 130 Ma it was attached to northwestern South America.

Description: Microspectralphotometric examinations of various recent pollen point to a different sporopollenin chemistry of the different taxa which is distinguishable by the UV-VIS absorptionspectra. The measurement areas have a diameter of 6 micron, by which several measurements for the spectra control in one pollen grain are possible. Labaratory experiments with chemical treatments as used by palynological preparation, show a clear change in the sporopollenin chemistry whichcould be identified by the absorption spectra. Therefore a new preparation technique for fossil and recent palynomorphs has to be developed to avoid chemical changes. First investigations of recent and fossil Pinus pollen have been clone on material from various facies types and a sediment core. The variations in the absorption spectra of the pollen indicate the different chemical influence of different facies types which could be used for facies analyses. Furthermore, significant changes in the absorption spectra are useful to identify reworked pollen or pollen with a different burial history. Zusammenfassung: Vergleichende mikrospektralphotometrische Untersuchungen der UV-VIS Absorptionsspektren verschiedener rezenter Pollen-Taxa zeigen, daß die Zusammensetzung bzw. Struktur des Sporopollenins bei verschiedenen Taxa variiert und daß diese anhand der Absorptionsspektren klar unterschieden werden kann. Die gemessene Fläche auf den jeweiligen Pollen hat einen Durchmesser von 6 j.lm, so daß mehrere Kontrollmessungen an einem Pollen möglich sind. Laborversuche an rezenten Pollen zeigen, daß chemische Einflüsse (z. B. HN03, Acetolyse) deutlich meßbare Veränderungen in der Struktur des Sporopollenins verursachen. Um Veränderungen des Sporepollenins durch die chemische Probenaufbereitung auszuschließen, wurde eine neue Präparationsmethode für fossile und rezente Palynomorphen entwickelt.

Description: ana marit., 27 (3/6): 145-150, 2 figs.; Frankfurt a. M.] According to the (neo-)Darwinian theory of evolution the appearance of "design" and optimization of biological properties are the results of natural selection and not of teleology. An opti· mization by selection is only possible for entities which are able to reproduce ("units of selection"). The "unit-of-selection"-problem will be discussed in relation to the atomism-holism-continuum of ecological and evolutionary concepts which range from Dawkins' "selfish gene" to LoveJock's "Gaia". Special emphasis will be given to the discussion of the group-selection problem which seems to be the critical breakpoint along this continuum. It will be shown that optimization through natural selection is only possible for units which can multiply and preserve their identity to a sufficient degree through multiplications. Such units are called replicators. Associations, communities, ecosystems and the biosphere do not qualify as replicators.

Description: In Sedimenten aus flachen Bohrungen in der Nordsee wurden gasförmige Kohlenwasserstoffe gefunden. Kohlenstoff- (Methan bis Propan) und Wasserstoff-Isotopanwerte lassen auf eine Mischung von Gasen bakterieller und thermischer Entstehung schließen. Die thermischen Gase sind in größerer Tiefe aus überwiegend mariner organischer Substanz entstanden und in die oberflächennahen Sedimente migriert. [Methane through pentane have been found in sediments from shallow North Sea boreholes. Carbon (methane through propane) and hydrogen (methane) isotope ratlos indicate both bacterial and thermal origins. The gases of thermal origin are interpreted as having been generated at considerable depth from predominantly marine source rocks and then to have migrated into the overlying sediments.]

Description: We propose that ocean conditions of the Near Islands in the western Atleutian Arc mimic those of the shallow continental shelf of the eastern Bering Sea to the extent that the marine community, including assemblages of forage fishes and their avian predators, has disinctly coastal characteristics. In contrast, marine avifauna and their prey at neighbouring Buldir Island are distinctly oceanic. For example, at the Near Islands, the ratio of thick-billed to common murres, Uria lomvia and U. aalge, is low and black.legged kittiwakes, Rissa tridacytla, but not red-legged kittiwakes, R. brevirostris, nest there. Diets of murres and kittiwkaes are dominated by sand lance, Ammodytes hexapterus, an abundant coastal species. At Buldir Island, thick-billed murres greatly outnumber common murres, red-legged kittiwakes and black-legged kittiwakes are both abundant, and diets of the birds consist primarily of oceanic squid and lantern-fish (Myctophidae). This mesoscale difference in food webs is apparently a consequence of the local physiography. A broad escarpment on the Near physiographic block creates a comparatively expansive, shallow, shelf-like habitat around the Near Islands, where a pelagic community typical of coastal regions flourished. Buldir Island is the only emergent feature of the Buldir physiographic block, with little shallow water surrounding it and, apparently, little opportunity for other than oceanic species to exist. Patterns in the distribution of fishes, and thus of sea birds, throughout the Atleutian Islands might be largely explained by the relationship between physical environments and food webs. In the larger context of fisheries oceanography, this model for the Aleutian Islands improves our ability to interpret physical and biological heterogeneity in the ocean and its relationship to regional community dynamics and trends in the abundance and productivity of individual species at higher tropic levels.

Description: The temperature relationship of routine metabolic rate (Rr) of non-feeding, non-growing Coregonus lavaretus larvae between 2 and 15°C is characterized by Q10-values ranging from l.8-2.45. The rate of growth, based on weight determinations, of first-feeding larvae amounted to 3.5, 7.6 and 9.4% day-1 at 5, 10 and 12°C respectively, from which Q10-values between 4.0 and 4.8 can be calculated. The rate of increase of muscle mass between 5 and 10°C, based on the determination of the cross-sectional area of inner muscle fibres, resulted in a Q10-value of 4.5. Water temperature influenced the pattern of growth of the inner muscle fibres. At hatching, after 360 day degrees, total muscle mass of larvae reared at 4 and 8°C was independent of temperature, but at 4°C the rate of mass increase owed more to hyperplasia (increase in fibre number) than to hypertrophy (increase in fibre mass), whereas at 8°C the opposite was the case. The calculation of power budgets (including the metabolic cost of growth) of first-feeding larvae yielded net conversion efficiencies (K2) increasing with temperature from 46.3% at 5°C to 54.7% at 12°C. Comparing our data with literature data two general conclusions can be drawn. (1) In first-feeding larvae the net, but not the gross, conversion efficiency of food energy increases with temperature. This is due to net energy input being characterized by a much higher Q10-value than energy expenditures. (2) In embryos of freshwater fish so far investigated hyperplasia plays a greater role in the increase of fibre mass than hypertrophy at the lower temperature, whereas in embryos of marine fish hyperplasia prevails at the higher temperature. It is suggested that this discrepancy correlates with the high concentration of free amino acids in the eggs of marine species which provide an additional, easily available, source of metabolic energy absent in freshwater species.

Description: The chemical composition of sediments from the Reykjanes Ridge is controlled by allochthonous and autochthonous processes. The surface sediments are characterized by relatively high contents of calciumoxide and strontium. Calcium and strontium dominate in the carbonate phase due to the high content of biogenic carbonate. A high percentage of iron and manganese are bound to oxides and hydroxides. An indication of hydrothermal activity was not observed. A considerable portion of adsorbed barium is transported in clay minerals. The higher amounts of aluminium in glacial sequences indicate an enhanced input of terrigenous material; the increase of stable bonding elemen~s points toward the large influence of detrital minerals. The distinct differences in the bonding characteristics of elements in these marine sediments in comparison to fluvial and coastal - deposits could be due to the different environmental conditions.