ALBERT

Description: 1 Zonation is often seen in environments with a strong physico-chemical gradient, such as salt marshes. It has been hypothesized that plant species are limited in their distribution by abiotic factors towards the more extreme end of the gradient, and by competition towards the more favourable end. Invasion of the native clonal grass genus Elymus in many Wadden Sea marshes may be due to increasing atmospheric nitrogen input into a nitrogen-limited environment. However, at Thmlauer Bay, Germany, Elymus athericus does not occur in lower salt marsh communities that are dominated by a dwarf shrub (Atriplex portulacoides). We therefore hypothesized that at this site the downslope (= more extreme) distributional boundary of E. athericus is a result of competition with A. portulacoides rather than of physiological limits. 2 A factorial experiment was set up to investigate the effects of removal of each competitor and fertilization. The reciprocal effects of the species on each other were measured in terms of vegetation cover and above-ground biomass. The impact of the tidal regime on plant zonation was investigated by calculating inundation frequencies at the boundary between the two plant populations from water level recordings. 3 Elymus athericus extended its distribution into the lower salt marsh when A. portulacoides was removed. The latter increased in cover but not in biomass after the removal of E. athericus. Neither species showed a response to nitrogen fertilization. The boundary between the two species in the control plots varied considerably in elevation and inundation frequency. 4 The lower distributional boundary of E. athericus can be interpreted as the result of competition with A. portulacoides. Improvement of nitrogen availability in concentrations of the same order of magnitude as annual atmospheric input had no detectable effect on plant zonation and growth. Elevation and inundation frequency were not strictly correlated with plant zonation.

Description: Heavy mineral studies of East Siberian river sediments, Laptev Sea surface sediments, and a sediment core of the western Laptev Sea were carried out in order to reconstruct the pathways of modern and ancient sediment transport from the Siberian hinterland to the Laptev Sea. The modern heavy mineral distribution of Laptev Sea surface sediments reflects mainly the riverine input. While the eastern and central part of the Laptev Sea is dominated by amphibole, which is supplied by the Lena River, the western part is dominated by pyroxene imported from the Siberian Trap basalts by the Khatanga River. The distribution of garnet and opaque minerals is additionally influenced by hydrodynamic processes. As a consequence of their high density, these minerals are predominantly deposited close to the river mouths. Heavy mineral and sedimentological studies of a sediment core of the western Laptev Sea were applied to reconstruct the postglacial history of the shelf area during the last 11 ka. In the lowermost interval of the core (〉c. 10 ka), high accumulation rates and a heavy mineral composition similar to that of the modern Khatanga river indicate fluvial conditions. Additionally, the high mica content in this interval may indicate meltwater inflow from the Byrranga mountains. Strong variations in accumulation rates, grain-size distribution, and heavy mineral composition are observed in the time interval between c. 10 and 6 ka, which represents the main transgression of the Laptev Sea shelf. During the uppermost interval (〈6 ka), rather stable conditions similar to the modem situation prevailed.

Description: The influence of mixing frequency and depth on phytoplankton functional group composition (mobile versus immobile species) was studied by enclosure experiments in a shallow, stratified lake. Mixing events were artificially induced at intervals from 2–12 d. The mixing depth was increased from the natural level (4 m) to 6 and 9 m. The mobile phytoplankton in the experiments consisted of cyanobacteria and flagellates. Among the latter, large and rapid swimming species were represented by dinoflagellates. An increase of the relative abundance of gas vacuolated cyanobacteria occurred with increasing frequency of mixing. Additionally Reynolds' hypothesis predicting the occurrence of certain mobile phytoplankton genera in response to the mixing regime could be confirmed for the condition when mixing depth exceeds the euphoric depth.

Description: Ship speed may have an important effect on the results of seabird surveys. We counted seabirds on a 20.5 X 0.3 km transect in the Kattegat that was sailed nine times with the RV "Heincke." Ship speed alternated between 9 knots and 5 knots. The numbers of the most common species, the Lesser Black-backed Gull (Larusfuscus), were significantly higher when the ship was sailing at lower speed similar to that of commercial fishing vessel when trawling in the area. It is postulated that scavenging species( e.g., gulls) are attracte to the low speed of vessels whereas non-scavengers (e.g. auks) are not

Description: The identification of developmental stages in fish eggs from plankton samples is often complicated by deformation of the embryos due to mechanical stress during the sampling procedure and by dehydration during formaldehyde fixation. The effects of formaldehyde fixation and mechanical stress on Baltic cod eggs (Gadus morhua callarias L.) were examined separately by visually comparing the morphological features of treated vs. live eggs of identical ontogenetic age. Microphotographs were made concurrently for documentation. In stage IA eggs, mechanical treatment resulted in scattered blastodiscs surrounded by single cells, while in further advanced stages the yolk membrane collapsed entirely, the yolk coagulated and the embryo extending over the yolk shrank. Formaldehyde fixation caused the yolk and the blastodisc or embryo to darken, and in some cases crystalline enclosures occurred. Eggs mechanically deformed during handling were clearly distinguishable from those that died prior to catching; however, staging was generally less accurate for formaldehyde-preserved eggs when compared with living specimens.

Description: The holocene depositional setting of the Laptev Sea was studied using three marine sediment cores from water depths between 77 and 46 m. Based on sedimentary parameters (TOC content, delta(13)C(org) Sedimentation rates) controlled by radiocarbon age models the palaeoenvironment of a strongly coupled river-shelf system was reconstructed since similar to 11 ka SP. Caused by a transgressing sea after the last glaciation, all cores reveal progressive decreases in sedimentation rates. Using the sedimentary records of a core from the Khatanga-Anabar river channel in the western Laptev Sea, several phases of change are recognized: (1) an early period lasted until similar to 10 ka BP characterized by an increased deposition of plant debris due to shelf erosion and fluvial runoff; (2) a transitional phase with consistently increasing marine conditions until 6 ka BP, which was marked at its beginning near 10 ka BP by the first occurrence of marine bivalves, high TOC content and an increase in delta(13)C(org); (3) a time of extremely slow deposition of sediments, commencing at,6 ka BP and interpreted as Holocene sea-level highstand, which caused a southward retreat of the depositional centres within the now submerged river channels on the shelf; (4) a final phase with the establishment of modern conditions after similar to 2 ka BP.

Description: The growth of Fucus vesiculosus L, germlings in chemically defined culture media containing a range of Cu concentrations (20-1000 nM) was monitored simultaneously with measurement of the Cu speciation in the media by competitive equilibrium-adsorptive cathodic stripping voltammetry, Fucus vesiculosus germlings were found to exude Cu-complexing Ligands with conditional stability constants of the order of 1.6 x 10(11), Ligand concentrations increased with increasing total dissolved Cu concentrations (Cu-T) until a concentration of 500-800 neq Cu.L-1 was reached. Concentrations of the ligand exceeded Cu-T in treatments containing 20 and 100 nM Cu-T were similar to Cu-T in the 500-nM Cu treatment, but were less than Cu-T in the 1000-nM treatment. Therefore, [Cu2+] were calculated to be at concentrations of 10(-11) - 10(-10) M in the 20- and 100-nM treatments, 10(-9) M in the 500-nM treatment, and 10(-7) M in the 1000-nM treatment, Growth rates were lowest at Cu2+ concentration 〉 10(-9). These results are discussed within the context of the potential roles for exuded copper-complexing ligands

Description: The aim of this study was to evaluate the potential of a compound diet as a live prey substitute for feeding European sea bass larvae (Dicentrarchus labrax L.). The effect of a commercial diet (Nippai ML feed) and live prey (Artemia nauplii) on tryptic enzyme activity, protein content, growth (standard length) and survival rates of sea bass larvae were tested during a 27-day rearing experiment. Sea bass larvae were divided into two groups. The live food group (control group) was fed exclusively on newly hatched Artemia nauplii (Inve AF grade), the test group was fed exclusively with the compound diet from day 15 onwards. As trypsin has been demonstrated to be a useful indicator for evaluating digestibility of food and the nutritional condition of fish larvae, individual tryptic enzyme activity was determined in both feeding groups. Larvae older than 14 days after hatching and fed on live food showed a significantly higher tryptic enzyme activity than larvae fed the compound diet. A similar relationship between tryptic activity and standard length in both test groups was detected only in small larvae (standard length 〈 7 mm). The usefulness of proteolytic enzyme activity measurements in larval fish research, as well as its use in aquaculture nutrition research, was confirmed. Protein content, increase in length and survival rates of the sea bass larvae were additionally determined in order to evaluate an influence on the diet. The protein content of larvae fed the Artemia nauplii was higher and the growth of larvae fed the compound diet was reduced. Larval mortality was not affected by the diet given.

Description: Microalgal biovolume is commonly calculated to assess the relative abundance (as biomass or carbon) of co‐occurring algae varying in shape and/or size. However, a standardized set of equations for biovolume calculations from microscopically measured linear dimensions that includes the entire range of microalgal shapes is not available yet. In comparison with automated methods, the use of microscopical measurements allows high taxonomic resolution, up to the species level, and has fewer sources of error. We present a set of geometric shapes and mathematical equations for calculating biovolumes of 〉850 pelagic and benthic marine and freshwater microalgal genera. The equations are designed to minimize the effort of microscopic measurement. The similarities and differences between our proposal for standardization and previously published proposals are discussed and recommendations for quality standards given.

Description: We looked at the routes taken by Magellanic Penguins up the beach while moving between the sea and the colony at a breeding site in San Julian, Argentina. Birds swam parallel to the shore for a period before leaving the water to cross the beach but trajectories over the beach were not perpendicular to the water's edge but at an angle of 39°. We examined the premise that birds might be optimizing for a trade off between time or energy by adopting this procedure and found that birds can gain little or no time by walking obliquely but can, under particular circumstances, save energy. These circumstances require that the previously-calculated costs of transport for walking have been over-estimated by a factor of two

Description: Various discretization methods exist for the numerical simulation of multiphase flow in porous media. In this paper, two methods are introduced and analyzed—a full-upwind Galerkin method which belongs to the classical finite element methods, and a mixed-hybrid finite element method based on an implicit pressure–explicit saturation (IMPES) approach. Both methods are derived from the governing equations of two-phase flow. Their discretization concepts are compared in detail. Their efficiency is discussed using several examples.

Description: The germination of spores of the endophytic brown algae Laminariocolax aecidioides and Laminarionema elsbetiae (Ectocarpales sensu lato) on their host Laminaria saccharina was studied using scanning electron microscopy. Zoids were the infective units in both taxa. Despite a large difference in size between spores of the species studied, the initial steps of infection were similar. Zoids settled on the host surface, and during secretion of adhesive material from their anterior end, the spores became elongated to rod-shaped and stood erect on the host. A single germ tube developed at the proximal end and penetrated the intact surface of the host. Sharp edges around the entrance hole and the absence of inward deformation of the host surface around the settled zoids suggest an enzymatic rather than a mechanical penetration mechanism.

Description: Coupled three-dimensional (3-D) physical oceanographic modelling and field sampling programmes were carried out in May 1988 and August 1991 to investigate the potential drift of larval cod (Gadus morhua L.) in the Bornholm Basin of the Baltic Sea. The goals were to predict the transport of cod larvae, thus aiding the identification of physical processes influencing larval retention/dispersal. Numerical simulations were performed using a 3-D eddy-resolving baroclinic model based on the Bryan–Cox–Semtner code adapted for the Baltic Sea. Within the Bornholm Basin, the model was initialized with ground truth data of physical parameters obtained on the research cruises, and all simulations were forced with actual wind data. Outside the basin, generalized hydrographic features of the Baltic Sea were utilized by incorporation of simulated hydrographic fields from previous model runs typical for the time periods considered. Larval drift was simulated either by incorporation of passive drifters, or as the initial horizontal distribution of larvae implemented into the model. Drift model simulations of larval transport agreed relatively well with field observations. The influence of variations in the vertical distribution on a smaller scale, i.e. vertical deviations of ± 6 m from the observed mean centre of mass, on the drift was examined, revealing no significant differences in the drift of larvae depending on their vertical distribution. The different wind forcing during the investigated time periods was linked to a retention situation in May 1988 and to a dispersal situation in August 1991. Finally, observed spatial distribution patterns of 1-group cod based on Baltic Young Fish Surveys (BYFS) were compared with their predicted transport in the larval phase and examined with respect to recruitment.

Description: Mesozooplankton production was estimated by using a new sampling technique and two alternative calculation methods. In essence, production estimates are based on significantly higher abundances. The contribution of juvenile stages to copepod and fish dynamics was generally low, so that the omission of juvenile stages in budgets will result in a small error. The situations reported in this study present a unique food web szenario, which in detail, however, was strongly dependent on methodology. Furthermore, relations between trophic levels were considered with respect to vertical distribution.

Description: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option

Description: Gracilaria conferta (Schousboe ex Montagne) J. ct G, Feldmann responded with an oxidative burst and rapid increases in respiration and halogenating activity when agar, agarose, or the agarose degradation products neoagarotetraose and neoagarohexaose were added to the growth medium, In contrast, carrageenan, oligocarrageenans, neoagarobiose, L-galactose, D-galactose, and several other mono- and oligosaccharides did not have any effect, Sixfold increases in respiration were observed 3 min after addition of neoagarohexaose. The response could only be induced in species of the genera Gracilaria and Gracilariopsis. Neoagarohexaose also elicited a release of hydrogen peroxide in less than 15 min, resulting in an immediate increase in algal brominating activity. Bleached thallus tips appeared a few hours after the addition of neoagarohexaose. This effect was dependent on the release of hydrogen peroxide and exposure to light, Exposure to light and oligosaccharide elicitors increased the production of reactive oxygen species, which reached destructive concentrations when both mechanisms were simultaneously active. Concentrations of 0.1 to 3.3 mu M agarose or agars were sufficient to trigger an increase in respiration, an oxidative burst response, and tip bleaching. However, higher concentrations of neoagarohexaose and neoagarotetraose were necessary to elicit the responses, indicating that the alga is more sensitive to oligoagars with degrees of biose-polymerization 〉 3, The extremely short reaction time and high specificity indicate that intermediates of agar degradation are recognized by Gracilaria as messengers when microbial degradation of its cell wall occurs, The physiological responses may represent the early stages of algal defense mechanisms involved in repression of pathogen ingress.

Description: 1. Monthly series of abundance indexes for the English Channel squid stock, based on fishery statistics of the United Kingdom (1980–93) and France (1986–96), were compared with water temperature data. The two objectives of the study were to test empirical predictive models and to analyse the stock–environment relationship at various time scales; both correlation and time-series statistical techniques were applied. Sea surface temperature (SST) showed inter-annual fluctuations and month-to-month auto-correlation in addition to the annual cycle. 2. Trends in squid landings and temperature at the annual scale were found to be related, whatever the statistical method used (moving averages, cumulative functions or regression using averaged data). 3. Variable selection applied in a ‘multi-month’ model suggested that fishing season indexes could be predicted from temperatures observed in the previous winter. The link between mild winter conditions and cohort success in winter/spring spawning species suggested that early life survival (and/or growth) was involved. This empirical model is a first step in the development of environment-predicted recruitment indexes useful for management advice. 4. Seasonal decomposition was performed on both the squid resource data and SST data in search of short-term relationships. In spite of the flexibility of the loliginid life-cycle, no significant relationship was found between squid seasonally adjusted indexes and temperature anomalies in the previous months. This underlined the conclusion that temperature effect on cohort success was not constant throughout the year.

Description: A 3 year study of the diets of breeding royal Eudyptes schlegeli and rockhopper E. chrysocome penguins was carried out at two nearby colonies on Macquarie Island. Diets of both species were dominated by euphausiids and myctophid fish, in particular Euphausia vallentini and Krefftichthys anderssoni. Prey items were those found in the region of the Polar Frontal Zone, confirming the importance of this zone to these penguins. Diets of both species before hatching of the chicks were variable between years, and differences in quantity of food brought ashore and degree of digestion of prey suggested inter-annual variation in distribution of prey resources. No dietary differences were detected in either penguin species across the breeding season, which reflected variability in diet at all stages, indicating that individual penguins foraged in separate areas. Significant differences between the two species were found, royal penguins consuming more myctophid fish and rockhopper penguins consuming more euphausiids. Differences were also found in the size class of prey items taken and the degree of digestion of food by both penguin species, indicating that prey were taken from different sectors of the ocean. It is concluded that the overlap in diet is small in individuals from these two spatially close colonies and, contrary to previous studies, indicates a separation in the resources used by both species. The contrast with previous studies is most likely a reflection of the different methods used to assess overlap and, to a lesser extent, the years and colonies in which the comparisons were made.

Description: Mastigophora brevipinnis Owen, 1856, is a ‘fossil teuthid’ presently considered to be a member of the coleoid cephalopod Suborder Loligosepiina Jeletzky, which in turn has been placed by various authors in or near the Vampyromorpha Grimpe. Recent morphological and biochemical analyses indicate that vampyromorphs are more closely related to the Octopoda than to the Decapodiformes. Fossils of Mastigophora from the Oxford Clay (Jurassic: Callovian) show soft-tissue preservation and evidence of arm crown specialization. Some of these fossils have up to eight short, thick arms with circular sucker-like structures and filiform distal extensions, plus what appear to be the bases of two thinner ventrolateral arms. The latter lack proximal suckers and curve medially to insert into the arm crown, similar to the tentacles that are the modified ventrolateral arms of living squids and cuttlefishes. This suggests that the thinner structures were decapod-like tentacles. If Mastigophora had tentacles homologous with those of modern decapods, then it was a decapod, because this synapomorphy defines the Decapodiformes. This indication of decapod affinities for Mastigophora brings into question the relationships of the other ‘fossil teuthids’. The inferred relationship of the Loligosepiina, including Mastigophora, with the Vampyromorpha, based largely on similarities of gladius morphology with that of living Vampyroteuthis, may reflect shared plesiomorphic characters.

Description: Microsatellite DNA markers were applied for the first time in a population genetic study of a cephalopod and compared with previous estimates of genetic differentiation obtained using allozyme and mitochondrial DNA (mtDNA) markers. Levels of genetic variation detected with microsatellites were much higher than found with previous markers (mean number of alleles per locus=10.6, mean expected heterozygosity (HE)=0.79; allozyme HE=0.08; mtDNA restriction fragment length polymorphism (RFLP) HE=0.16). In agreement with previous studies, microsatellites demonstrated genetic uniformity across the population occupying the European shelf seas of the North East Atlantic, and extreme genetic differentiation of the Azores population (RST/FST=0.252/0.245; allozyme FST=0.536; mtDNA FST=0.789). In contrast to other markers, microsatellites detected more subtle, and significant, levels of differentiation between the populations of the North East Atlantic offshore banks (Rockall and Faroes) and the shelf population (RST=0.048 and 0.057). Breakdown of extensive gene flow among these populations is indicated, with hydrographic (water depth) and hydrodynamic (isolating current regimes) factors suggested as possible barriers to migration. The demonstration of genetic subdivision in an abundant, highly mobile marine invertebrate has implications for the interpretation of dispersal and population dynamics, and consequent management, of such a commercially exploited species. Relative levels of differentiation indicated by the three different marker systems, and the use of measures of differentiation (assuming different mutation models), are discussed.

Description: Benthic microalgae and the herbivores Idothea chelipes (Isopoda) and Littorina littorea (Gastropoda) were used as an experimental model system to study the effect of herbivore type on primary producer diversity. Both herbivores enhanced diversity at intermediate grazing pressures, the enhancing effect being stronger with Littorina. This difference is explained by differences in the spatial heterogeneity of the grazed microalgal biofilm caused by behavioural differences in spatial grazing patterns. Idothea spreads its grazing pressure rather evenly in space (“lawn-mower” type), whereas Littorina creates pronounced spatial heterogeneity by moving slowly over the biofilm and decimating it within the grazing tracks (“bulldozer” type). Idothea grazing did not enhance biomass patchiness beyond the level of ungrazed controls (maximum/minimum from 1.7 to 5.5), whereas Littorina strongly increased patchiness (maximum/minimum from 45 to 850).

Description: Despite recognition that Fe availability is significant in regulating oceanic production in some regions, the biogeochemistry of this trace element is poorly understood. To complement contemporary methods of analytical chemistry, we have used an immunological approach to monitor theFenutrition of marine phytoplankton. In prokaryotes and numerous microalgae, the redox catalyst ferredoxin is functionally replaced by flavodoxin during periods of Fe deficiency. In this study, antibodies were raised against ferredoxin purified from a marine diatom, and their utility as a diagnostic indicator was assessed. A species survey demonstrated broad reactivity with both pennate and centric diatoms and additionally with several nondiatom taxa. In batch cultures of the diatom Phaeodactylum tricornutum Bohlin, in which Fe levels were varied, accumulation of ferredoxin varied with the physiological state of the culture; in unimpaired cells (Fv/Fm $ 0.65), ferredoxin levels were high, whereas levels dropped markedly in cells experiencing even slight photochemical impairment. Accumulation of flavodoxin varied inversely with that of ferredoxin. An experiment was performed to demonstrate the temporal pattern of accumulation of ferredoxin upon recovery from Fe limitation. Prior to Fe amendment,cells were physiologically impaired (chlorotic, Fv/Fm , 0.3) and contained flavodoxin but no detectable ferredoxin. Following addition of Fe, constraints on photochemistry were relaxed within hours. Coinciding with this, levels of flavodoxin declined, whereas ferredoxin was accumulated to high levels within 8 h.

Description: Rayleigh fractionation is an important, open system process that involves the progressive removal of a fractional increment of a trace substance from a larger reservoir. A consistent relationship, such as a distribution coefficient, equilibrium constant, or a fractionation factor, is maintained between the reservoir and each increment at the instant of its formation, but, once formed, each increment is thereafter removed or otherwise isolated from the system. The mathematical constraints of this process include the distribution coefficient along with a statement of material balance in the shrinking system. These constraints may be combined into a single differential equation that may be integrated to a well-known relationship discovered by Rayleigh (1902). Examples of this common process include condensation, distillation, and the formation of crystals from a melt or a solution. As shown in the following, Rayleigh fractionation explains many different characteristics of meteoric waters, and provides a first-order explanation of the MWL

Description: Periphyton was grown on transparent plastic substrata in the Kiel Fjord and used for short-term laboratory experiments to study the feeding selectivity of the periwinkle Littorina littorea in response to the vertical structure of the periphyton. The susceptibility of algae to periwinkle grazing was assessed by comparing the species-specific biomass within the grazing tracks of the snails to the biomass outside the tracks. After 3 weeks of incubation, the periphyton consisted of a scattered monolayer of algal cells without vertical structure. No apparent grazing could be found. After 6 weeks of incubation, periphyton consisted of a tightly attached undergrowth (mainly Cocconeis scutellum, Bacillariophyceae, and Myrionema sp., Phaeophyceae) and canopy of filamentous (Melosira moniliformis, Bacillariophyceae) and stalked forms (Achnanthes longipes, Bacillariophyceae). The unicellular diatoms Fragilaria tabulata and Stauroneis constricta grew partly on the primary substratum and partly as epiphytes on the canopy species. The canopy species and the epiphytes were decimated inside the grazing tracks, while the tightly attached undergrowth species appeared ungrazed.