ALBERT

Description: Indices of β-diversity are of two major types, (1) those that measure among-plot variability in species composition independently of the position of individual plots on spatial or environmental gradients, and (2) those that measure the extent of change in species composition along predefined gradients, i.e. species turnover. Failure to recognize this distinction can lead to the inappropriate use of some β-diversity indices to measure species turnover. Several commonly-used indices of β-diversity are based on Whittaker's βW (βW = γ/α, where γ is the number of species in an entire study area and α is the number of species per plot within the study area). It is demonstrated that these indices do not take into account the distribution of species on spatial or environmental gradients, and should therefore not be used to measure species turnover. The terms ‘β-diversity’ and ‘species turnover’ should not be used interchangeably. Species turnover can be measured using matrices of compositional similarity and physical or environmental distances among pairs of study plots. The use of indices of β-diversity and similarity-distance curves is demonstrated using simulated data sets.

Description: Porewater fluxes into or out of the sediments in aquatic systems are frequently estimated using Fick's First Law. This assumes that diffusive processes control the transport of nutrients. As a corollary, advection, bioturbation and chemical processes are assumed not to be significant. Through a series of sediment core incubations, this paper seeks to quantify the uncertainties involved in such assumptions. Duplicate sediment cores were collected from 28 sites along the Swan–Canning Estuary, returned to the laboratory and incubated under oxic or anoxic conditions. Porewater nutrient concentrations, sediment porosity and initial nutrient concentrations in the overlying water were measured. These parameters were used to estimate the expected nutrient fluxes via Fick's First Law. The estimated fluxes were then compared with measured fluxes of nutrients out of the sediments over the incubation period. Severe bioturbation occurred in several of the anoxic treatments, resulting in large releases of nutrients into the overlying water. Aside from these bioturbated cores, phosphate and ammonium fluxes under anoxic conditions are well predicted by Fick's First Law. Nitrate fluxes are predicted well under oxic conditions. For coarse sediments (D10 averaging 0·3 mm) and under redox conditions favourable for nutrient release, Fick's First Law predicted close to 100% of the observed fluxes. For finer grain sediments (D10 〈 0·01 mm), Fick's First Law overestimated the observed flux by up to 40%. Under unfavourable oxygen conditions, chemical retardation processes are likely to dominate fluxes, and the error associated with using Fick's First Law is increased. These results confirm the usefulness of using Fick's First Law for a baseline estimate of nutrient fluxes under favourable redox conditions. Much greater care must be taken when using Fick's First Law to estimate nutrient fluxes under unfavourable redox conditions, or under conditions when bioturbation is likely to be severe.

Description: Although they can provide valuable information on at-sea ecology, data-loggers may adversely affect energetics, diving performance, and breeding success of equipped birds. With the aim of determining the effects of leg-attached data-loggers on the activity budgets of Humboldt penguins (Spheniscus humboldti) while on land, we equipped birds kept at the Landau Zoo, Landau, Germany, with such devices. We followed them during sample periods and recorded the occurrence and length of behaviors. Birds quickly habituated to the devices within 1 day of deployment, and mean rates of device-pecking were low (0.7–1.7 pecks/hr), with device-induced behaviors accounting for 〈1% of the mean daily activity budget. The method of device attachment appears behaviorally less stressful than the traditional tape-based system in which devices are normally attached to the penguin's back. By facilitating the testing of newly developed data-loggers on captive birds, or the development of methods for device attachment, zoos and aquaria may strengthen their role in animal conservation by helping research on free-ranging animals.

Description: Agar oligosaccharides in the neoagarobiose series were prepared by partial enzyme hydrolysis, separated on Biogel P2 and P4, and analyzed by high-performance anion exchange chromatography with pulsed amperometric detection, yielding neoagarosaccharide fractions with a disaccharide repetition degree ranging from 1 (neoagarobiose) to more than 8 (neoagarohexadecaose). These fractions were analyzed for their biological activity toward the marine red alga Gracilaria conferta (Schousboe ex Montagne) J. et G. Feldmann in terms of increase of oxygen consumption, release of hydrogen peroxide, elimination of epiphytic bacteria, and induction of thallus tip bleaching. The structure–activity and dose–response relationships of neoagarosaccharides were very similar in the respiratory and oxidative burst responses and in their bactericidal properties, with neoagarosaccharides consisting of 6 to 8 disaccharide repeating units being the most active. All these responses were competitively inhibited by the reduced form of neoagarohexaose, neoagarohexaitol. In contrast, the tip-bleaching response was light dependent, required much higher concentrations of neoagarosaccharides, and was not inhibited by neoagarohexaitol, suggesting that it is an unspecific oxidative stress reaction. Putative structural effects on the recognition of endogenous agar-oligosaccharide elicitors by G. conferta are discussed.

Description: Wandering Albatrosses Diomedea exulans are frequently killed when they attempt to scavenge baited hooks deployed by long-line fishing vessels. We studied the foraging ecology of Wandering Albatrosses breeding on Marion Island in order to assess the scale of interactions with known long-line fishing fleets. During incubation and late chick-rearing, birds foraged further away from the island, in warmer waters, and showed high spatial overlap with areas of intense tuna Thunnus spp. long-line fishing. During early chick-rearing, birds made shorter foraging trips and showed higher spatial overlap with the local Patagonian Toothfish Dissostichus eleginoides long-line fishery. Tracks of birds returning with offal from the Toothfish fishery showed a strong association with positions at which Toothfish long-lines were set and most diet samples taken during this stage contained fishery-related items. Independent of these seasonal differences, females foraged further from the islands and in warmer waters than males. Consequently, female distribution overlapped more with tuna long-line fisheries, whereas males interacted more with the Toothfish long-line fishery. These factors could lead to differences in the survival probabilities of males and females. Non-breeding birds foraged in warmer waters and showed the highest spatial overlap with tuna long-line fishing areas. The foraging distribution of Marion Island birds showed most spatial overlap with birds from the neighbouring Crozet Islands during the late chick-rearing and non-breeding periods. These areas of foraging overlap also coincided with areas of intense tuna long-line fishing south of Africa. As the population trends of Wandering Albatrosses at these two localities are very similar, it is possible that incidental mortality during the periods when these two populations show the highest spatial overlap could be driving these trends.

Description: Fungi or bacteria that produce secondary metabolites often have the potential to bring up various compounds from a single strain. The molecular basis for this well-known observation was confirmed in the last few years by several sequencing projects of different microorganisms. Besides well-known examples about induction of a selected biosynthesis (for example, by high- or low-phosphate cultivation media), no overview about the potential in this field for finding natural products was given. We have investigated the systematic alteration of easily accessible cultivation parameters (for example, media composition, aeration, culture vessel, addition of enzyme inhibitors) in order to increase the number of secondary metabolites available from one microbial source. We termed this way of revealing nature's chemical diversity the 'OSMAC (One Strain-Many Compounds) approach' and by using it we were able to isolate up to 20 different metabolites in yields up to 2.6 g L(-1) from a single organism. These compounds cover nearly all major natural product families, and in some cases the high production titer opens new possibilities for semisynthetic methods to enhance even more the chemical diversity of selected compounds. The OSMAC approach offers a good alternative to industrial high-throughput screening that focuses on the active principle in a distinct bioassay. In consequence, the detection of additional compounds that might be of interest as lead structures in further bioassays is impossible and clearly demonstrates the deficiency of the industrial procedure. Furthermore, our approach seems to be a useful tool to detect those metabolites that are postulated to be the final products of an amazing number of typical secondary metabolite gene clusters identified in several microorganisms. If one assumes a (more or less) defined reservoir of genetic possibilities for several biosynthetic pathways in one strain that is used for a highly flexible production of secondary metabolites depending on the environment, the OSMAC approach might give more insight into the role of secondary metabolism in the microbial community or during the evolution of life itself.

Description: Sponges of the Aplysinidae family contain large amounts of bacteria that are embedded within the sponge tissue matrix. In order to determine the stability and specificity of the Aplysina–microbe association, sponges were maintained in recirculating seawater aquariums for 11 days. One aquarium was left untreated, a second one contained 0.45 μm filtered seawater (starvation conditions) and the third one contained 0.45 μm filtered seawater plus antibiotics (antibiotics exposure). Changes in the microbial community were monitored using group-specific, 16S rRNA targeted oligonucleotide probes, by denaturing gradient gel electrophoresis and by electron microscopic observations. Furthermore, the changes in the natural product profile were monitored using high-performance liquid chromatography. The measured parameters showed that a large fraction of the sponge-associated microbial community could not be cleared under the given experimental conditions. Based on these cumulative results we postulate that a large fraction of sponge-associated bacteria resides permanently in the Aplysina aerophoba mesohyl pointing to a highly integrated interaction between the host sponge and associated microorganisms.

Description: The aim of this study was to isolate bacteria with antimicrobial activities from the marine sponges Aplysina aerophoba and Aplysina cavernicola. The obtained 27 isolates could be subdivided into eight phylogenetically different clusters based on comparative sequence analysis of their 16S rDNA genes. The sponge isolates were affiliated with the low (Bacillus) and high G+C Gram-positive bacteria (Arthobacter, Micrococcus), as well as the α-Proteobacteria (unknown isolate) and γ-Proteobacteria (Vibrio, Pseudoalteromonas). One novel Bacillus species was identified and two species were closely related to previously uncharacterized strains. Isolates with antimicrobial activity were numerically most abundant in the genera Pseudoalteromonas and the α-Proteobacteria. The sponge isolates show antimicrobial activities against Gram-positive and Gram-negative reference strains but not against the fungus Candida albicans. A general pattern was observed in that Gram-positive bacteria inhibited Gram-positive strains while Gram-negative bacteria inhibited Gram-negative isolates. Antimicrobial activities were also found against clinical isolates, i.e. multi-resistant Staphylococcus aureus and Staphylococcus epidermidis strains isolated from hospital patients. The high recovery of strains with antimicrobial activity suggests that marine sponges represent an ecological niche which harbors a hitherto largely uncharacterized microbial diversity and, concomitantly, a yet untapped metabolic potential.

Description: A 550-km-long transect across the Ninetyeast Ridge, a major Indian ocean hotspot trail, provided seismic refraction and wide-angle reflection data recorded on 60 ocean bottom instruments. About 24 000 crustal and 15 000 upper mantle arrivals have been picked and used to derive an image of the hotspot track. Two approaches have been chosen: (i) a first-arrival tomographic inversion yielding crustal properties; and (ii) forward modelling of mantle phases revealing the structure at the crust–mantle boundary region and of the uppermost mantle. Away from the volcanic edifice, seismic recordings show the typical phases from oceanic crust, that is, two crustal refraction branches (Pg), a wide-angle reflection from the crust–mantle boundary (PmP) and a wave group turning within the upper mantle (Pn). Approaching the edifice, three additional phases have been detected. We interpret these arrivals as a wide-angle reflection from the base of material trapped under the pre-hotspot crust (Pm2P) and as a wide-angle reflection (PnP) and its associated refraction branch (PN) from a layered upper mantle. The resulting models indicate normal oceanic crust to the west and east of the edifice. Crustal thickness averages 6.5–7 km. Wide-angle reflections from both the pre-hotspot and the post-hotspot crust–mantle boundary suggest that the crust under the ridge has been bent downwards by loading the lithosphere, and hotspot volcanism has underplated the pre-existing crust with material characterized by seismic velocities intermediate between those of mafic lower crustal and ultramafic upper mantle rocks (7.5–7.6 km s−1). In total, the crust is up to ≈ 24 km thick. The ratio between the volume of subcrustal plutonism forming the underplate and extrusive and intrusive volcanism forming the edifice is about 0.7. An important observation is that underplating continued to the east under the Wharton Basin. During the shield-building phase, however, Ninetyeast Ridge was located adjacent to the Broken Ridge and was subsequently pulled apart along a transform fault boundary. Therefore, underplating eastwards of the fracture zone separating the edifice from the Wharton Basin suggests that prolonged crustal growth by subcrustal plutonism occurred over millions of years after the major shield-building stage. This fact, however, requires mantle flow along the fossil hotspot trail. The occurrence of PnP and PN arrivals is probably associated with a layered and anisotropic upper mantle due to the preferential alignment of olivine crystals and may have formed by rising plume material which spread away under the base of the lithosphere.

Description: In periphyton communities, autotrophic algae and prokaryotes live in close spatial proximity to heterotrophic components such as bacteria and micro- and meiofauna. In factorial field experiments, we manipulated grazer access and nutrient supply to periphyton communities and measured the effects on algal, ciliate, meiofaunal, and bacterial biomass. We tested whether grazing macrozoobenthos affects all periphytic components (generalist consumption), whether nutrient effects propagate through the community, and whether interactions between the different periphyton groups allow for indirect feedback mechanisms. The experiments were conducted during three different seasons in a meso-eutrophic lake in Sweden (Lake Erken) and at an adjacent coastal marine site (Väddö) of similar productivity, but with contrasting grazer fauna. We found strong direct effects of nutrients and grazing on algae at both sites. Algal biomass increased in fertilized treatments and was significantly reduced when grazers were present. The algae clearly dominated the system quantitatively and were positively correlated to the biomass of ciliates and meiofauna. The effects of grazing and nutrients were more complex for heterotrophs than for algae. Generally, the presence of grazers tended to increase the biomass of bacteria, ciliates, and meiofauna. Thus, macrograzers were not generalist consumers of the entire community, but mainly reduced algae. Furthermore, the results suggested strong indirect effects of grazing, presumably through changes in nutrient supply and algal size structure. Nutrient enrichment had weak and inconsistent effects on bacterial, ciliate, and meiofaunal biomass. There was thus no complete propagation of bottom-up effects through the community, and strong internal feedback mechanisms within the periphyton mediated the effects of macroconsumers and nutrient enrichment.

Description: The behaviour of Magellanic Penguins Spheniscus magellanicus commuting between their foraging areas and breeding areas in San Julian Bay, Argentina was studied to examine whether tidal rip currents affected travelling patterns. Although there was no apparent relationship between departure and arrival patterns and the state of the tidal cycle, birds travelling against the current dived for longer periods and had shorter rests on the surface than birds travelling with the current. In addition, birds swimming against the current hugged the banks of tidal rivers much more closely than did birds swimming with the current, thus reducing the magnitude of the current against which they had to swim. In cases of extremely high current speeds, birds travelling upstream walked. Models regarding the energetics of movement indicate that the strategies adopted by Magellanic Penguins can result in substantial energy savings.

Description: A high-resolution Holocene tephrochronology for northern Germany has been established based on systematic tephrostratigraphical analysis of three peat bogs. Microscopic volcanic ash layers have been traced and characterised petrographically and by the chemical composition of the glass shards. At least 37 ash horizons representing 16 different explosive volcanic eruptions have been identified and many can be correlated between the three sites, up to 100 km apart. The tephra layers can be related to Icelandic volcanic sources and some correlated to the eruptions of Askja 1875, Hekla 3, Hekla Selsund, Hekla 4 and Hekla 5, as well as to unspecified eruptions of Icelandic volcanic systems, e.g. Torfajökull. The source volcanoes for some tephra layers remain unidentified. Some tephra layers were known previously from the North Atlantic region (e.g. Sluggan, Glen Garry), others have not been recorded previously in the literature (e.g. microlite tephra). This study provides the first comprehensive Holocene tephrostratigraphical record for northern Germany, complementing the North Atlantic tephrostratigraphical dating framework, effectively extending it into central Europe. The study shows that Icelandic ash layers are even more widespread than hitherto thought.

Description: We studied the effects of water column mixing depth and background turbidity on phytoplankton biomass, light climate, and nutrients in two field enclosure experiments designed to test predictions of a dynamical model. In 1997 and 1998, we created gradients of mixing depth by enclosing the 100-μm-filtered phytoplankton community of a phosphorus-deficient lake in cylindrical plastic bags of varying depth (1.5–15 m) which were continuously mixed. To mimic different levels of background turbidity, we surrounded the transparent enclosure walls with a layer of opaque white (1997) or black (1998) plastic. The experiments were run for 4 wk (1997) and 6 wk (1998). The results supported two key assumptions of the model: specific production and specific sedimentation losses both decreased with increasing mixing depth. At all mixing depths, fast-sinking diatoms dominated the communities. In accordance with model predictions, algal biomass concentration and standing stock (summed over the mixed layer) showed a unimodal relationship to mixing depth when background turbidity was high (1998). When background turbidity was lower (1997), only the ascending limbs of the corresponding relationships were found, which supports the prediction that the mixing depth at which biomass peaks (i.e., becomes predominantly limited by light) increases with decreasing background turbidity. Also in accordance with predictions, light intensity at the bottom of the mixed layer decreased with increasing mixing depth and with increasing background turbidity. Finally, the data supported only the ascending limbs of the predicted inverse unimodal relationships among mixing depth and dissolved inorganic and total water column phosphorus. The absence of descending limbs in these relationships at low mixing depths was probably due to deviations of the experimental systems from two model assumptions. First, the remineralization rate of sedimented phosphorus may have been too slow to equilibrate with sedimentation losses over the experimental periods. Second, biomass yield per unit nutrient (the ratio of seston carbon to phosphorus) was not constant, but decreased with increasing mixing depth. To our knowledge, these are the first field experiments in which the effects of mixing depth on phytoplankton and its resources have been investigated systematically along a large gradient.

Description: 1. The aim of this study was to estimate patchiness in biomass and in the internal nutrient status of benthic algae on hard substrata (epilithon) in Lake Erken, Sweden, over different levels of distance, depth and time. Knowledge of the sources and scale of patchiness should enable more precise estimation of epilithic biomass and nutrient status for the entire lake. We focused on the horizontal scale, about which little is known. 2. We sampled epilithon by SCUBA diving and used a hierarchical sampling design with different horizontal scales (cm, dm, 10 m, km) which were nested in two temporal scales (within and between seasons). We also compared two successive years and three sampling depths (0, 1 and 4 m). Biomass was measured as particulate carbon and chlorophyll a (Chl a) and internal nutrient status as carbon : nitrogen : phosphorus (C : N : P) ratios and as specific alkaline phosphatase activity (APA). 3. Horizontal variation accounted for 60–80 and 7–70% of the total variation in biomass and in nutrient status, respectively, at all depths and during both years. Both small and large scales accounted for significant variation. We also found variation with time and depth. Biomass increased in autumn after a summer minimum, and the within-season variation was very high. The lowest biomass was found at 0 m depth. Both N and P limitation occurred, being higher in 1996 than in 1997 and decreased with depth. 4. As a consequence, any sampling design must address variation with distance, depth and time when estimating biomass or nutrient limitation of benthic algae for an entire lake. Based on this analysis, we calculated an optimal sampling design for detecting change in the epilithic biomass of Lake Erken between different sampling days. It is important to repeat the sampling as often as possible, but also the large scales (10 m and km) and the dm scale should be replicated. Using our calculations as an example, and after a pilot study, an optimal sampling design can be computed for various objectives and for any lake. 5. Short-term impact of the wind, light and nutrient limitation, and grazing, might be important in regulating the biomass and nutrient status of epilithic algae in Lake Erken. Patchiness in the nutrient status of algae was not coupled to the patchiness of biomass, indicating that internal nutrients and biomass were regulated by different factors.

Description: In order to clarify mechanisms influencing the reproductive success of Baltic cod (Gadus morhua L.), a modelling exercise was performed to examine the effects of the wind-driven circulation on the transport of early life stages between the western and eastern Baltic. Because the different stocks spawn in different areas and environments at different times of the year, the occurrence of variable age/length distributions of juveniles within the different potential nursery areas can be explained by the circulation pattern. A three-dimensional circulation model of the Baltic was utilized to investigate the temporal evolution of egg and larval distributions of the western Baltic cod stock, which spawns preferentially in the Danish Straits, in Kiel Bay as well as in Mecklenburg Bay. For different scenarios (1988 and 1993), within- and between-year variability of egg and larval transport showed large differences, primarily due to variations in wind forcing. In 1988, relatively low and variable wind forcing prevailed, whereas, due to sustained strong, mainly westerly, winds, in January 1993, the recent major Baltic inflow to the Baltic Sea occurred. Differences in contributions of early life stages from the western to the eastern cod stocks, depending on the physical forcing conditions, suggest that this process can be controlled by variations of atmospheric forcing conditions. The potential for early life stages from the western Baltic cod stock to drift into the Arkona Basin and the Bornholm Basin, and to contribute there to the juvenile population, has been recognized as being mainly due to strong westerly winds. During cold winters, retention of eggs, larvae and juveniles within their original spawning grounds may predominate. Transport of cod early life stages from the Øresund, as well as from the Great Belt, can occur only during periods of strong westerly winds, but significant eastwards orientated drift from Kiel Bay and Mecklenburg Bay was also evident during periods of minor westerly wind influence.

Description: In most groups of organisms, the species richness decreases from the tropics to the poles. The mechanisms causing this latitudinal diversity gradient are still controversial. We present data from a comprehensive weighted meta-analysis on the strength of the latitudinal gradient in relation to body size. We sampled literature data on the correlation between species richness and latitude for a variety of organisms, ranging from trees to protozoa. In addition, own data on the presence of large-scale diversity patterns for diatoms were included, both for local and regional species richness. The strength of the latitudinal gradient was positively correlated to the size of the organisms. Strongest decreases of species richness to the poles was found for large organisms like trees and vertebrates, whereas meiofauna, protozoa and diatoms showed weak or no correlations between species richness and latitude. These results imply that latitudinal gradients are shaped by non-equilibrium (regional) processes and are persistent under conditions of dispersal limitation.

Description: Climate variations over the Northern Hemisphere are to a substantial proportion associated with the North Atlantic Oscillation (NAO). Recently, many studies revealed the impacts of the NAO on the dynamics of organisms in different ecosystems but the results in the single studies were inconsistent. Here, we used meta‐analysis techniques for a quantitative synthesis of results. We tested the influence of the NAO on the timing of life history events, on biomass of organisms, and on biomass of different trophic levels. We found a clear NAO signature in freshwater, marine, and terrestrial ecosystems. The response of life history events to the NAO was similar in all environments but less pronounced at higher latitudes. The magnitude of the biomass response was significantly related to the NAO, either positively in aquatic or negatively in terrestrial ecosystems. The response depended on longitude, the effect being less pronounced in Eastern Europe. The results stressed that a meta‐analysis is a valuable tool in the field of climate‐driven ecosystem responses and can identify more general ecological responses than single studies. We recommend the inclusion of nonsignificant results in order to archive an objective view of the strength of NAO and climate impacts in general.

Description: A backfiring weapon: The release of H2O2 by an amino acid oxidase is the early defensive reaction of the red alga Chondrus crispus against the endophytic green algal pathogen Acrochaete operculata (see scheme). This reaction can be induced by L-asparagine, which is released by the attacker when it recognises host cell-wall κ-carrageenan oligosaccharides. The induced signal of the attacker thus serves directly as the substrate for the production of the defensive metabolite.

Description: Oxidative stability of lipids from squid tissues was compared with those of other marine lipids. On the basis of peroxide formation, total lipids (TL) from squid viscera or squid muscle with skin were most oxidatively stable, followed by squid eye TL, trout egg TL, bonito oil, and tuna orbital TL, respectively. This tendency in oxidative stabilities was also confirmed by the decrease in unoxidized polyunsaturated fatty acids during oxidation. Analyses of tocopherol contents and lipid compositions suggested that the higher oxidative stabilities of three kinds of squid tissue TL and trout egg TL compared to those of bonito oil and tuna orbital TL would be mainly because of the presence of phospholipids (PL) in squid tissue lipids and trout egg TL. However, the oxidative stability of lipids containing PL did not always decrease with increasing PL contents and stability was strongly influenced by PL composition. As squid viscera contained more than 25% of TL and these lipids were oxidatively stable, squid viscera may be used as a good resource of functional lipids rich in eicosapentaenoic acid and docosahexaenoic acid.

Description: In this study, we consider the influence of mesoscale oceanographic processes around the Falkland Islands (Islas Malvinas) in the South-west Atlantic, during the period in which the commercial squid fishery for Illex argentinus operates. Spatially referenced fishery data and satellite-derived advanced very high resolution radiometry (AVHRR) sea surface temperature (SST) data were examined using geographic information system (GIS) techniques. The distribution and relative abundance of I. argentinus in the Falkland Islands fishery was examined for the period 1989–96. Three consistent areas of high abundance were observed to the north-east (shelf-break region) and north-west (shelf region) of the islands, and close to the northern coast of East Falkland. Areas of high sea surface temperature gradients (thermal gradients) extracted from remotely sensed satellite images were used as an indicator of mesoscale oceanographic activity and compared with the location of the fishery. I. argentinus were found to be associated with areas of thermal gradients, commonly seen at the interface of Falkland Current and Patagonian shelf waters. The techniques used in this analysis allow the overlay and analysis of physical oceanographic and fishery data with potential applications in fisheries management and operational fisheries oceanography.

Description: This study examined the changing status of the marine ecosystem at the island of South Georgia (Southern Ocean) using up to 27 variables measured over 22 years from three upper trophic level predators that specialize in foraging upon krill (Eupuasia superba Dana). These variables included population size, breeding performance, offspring growth rate, foraging behaviour and diet. A method was developed for reducing these multivariate time-series to a single vector, called a combined standardized index (CSI). 2 Sensitivity analyses showed that missing values had a large effect upon the accuracy of the CSI but this effect was reduced if the individual variables were highly correlated. The level of correlation and proportion of missing values within the empirical data set were within the acceptable range. Individual variables had widely varying influence upon the CSI but, in general, those with longer time-series had the greatest influence. 3 Principal components analysis showed that variables representing offspring growth tended to explain the greatest proportion of the variability in the CSI and this was followed by variables representing diet. 4 There were 3 years in which the CSI showed extreme and significantly low values. There was a significant non-linear functional response (similar to the Holling Type II functional response) between the overall CSI and krill biomass and a similar relationship existed when the CSI was calculated for each species individually. 5 Separate analysis of variables that were likely to be representative of changing population size showed the presence of a significant decline between 1977 and 1998. There was no trend in the CSI from variables representative of foraging conditions during the summer breeding season. The study has shown that the marine ecosystem at South Georgia shows acute but transient variability that is amplified in the response of upper trophic-level predators. There is less certainty that trends in populations are a consequence of shifts in the degree to which the ecosystem can support krill-feeding seals and penguins.

Description: Cephalopod reproductive strategies are reviewed in order to clarify their current, confusing status. Based on the type of ovulation, spawning pattern and growth between egg batches or spawning periods, five comprehensive and flexible cephalopod reproductive strategies are defined. Accordingly, with these three factors the following classification is proposed. (a) Spawning once (formerly semelparity) consisting of simultaneous terminal spawning, with synchronous ovulation, monocyclic spawning and absence of growth between egg batches. (b) Spawning more than once (formerly iteroparity) including: (i) polycyclic spawning with egg-laying occurring in separate batches during the spawning season and growth occurring between production of egg batches and spawning seasons; (ii) multiple spawning, with group-synchronous ovulation, monocyclic spawning and growth between egg batches; (iii) intermittent terminal spawning, with group-synchronous ovulation, monocyclic spawning and no growth between egg batches; (iv) continuous spawning, with asynchronous ovulation, monocyclic spawning and growth between egg batches. Examples of species exhibiting each of these reproductive strategies are given. The large amount of inter-species variation in several life-history traits related to reproductive events is discussed.

Description: Individual growth rates, feeding rates (%BWd−1) and food conversions for cuttlefish (S. officinalis) hatchlings and juveniles were determined during this study. A flow-through system was used. Water temperature reached 30 °C during the hottest part of the day, gradually decreasing to 25 °C during the night; salinity varied between 37 ± 3 ppt and lights were kept on for 14 h day−1. Hatchlings were placed in separate compartments with a water volume of 1.2 L. Juvenile cuttlefish (from 0.5 to 25 g) were placed in bigger baskets, with a water volume of 5.2 L. Water flow was 120 L h−1. The biggest cuttlefish used in these experiments (〉 25 g) were gathered in groups of five and placed in circular tanks (water volume of 250–300 L). Thus, results obtained in this case are means and not individual data. During the first 10, 20, 30 and 40 days, mean growth rates (of all individuals sampled by age group) decreased consistently (11.8 ± 4.1, 9.8 ± 1.8, 8.1 ± 2.2 and 7.3 ± 0.7%BW−1 respectively); in similar fashion, mean feeding rates decreased with age group (33.7 ± 13.5, 22.0 ± 7.9, 17.3 ± 3.9 and 16.7%BWd−1 respectively). Mean food conversions varied between 3.6 and 2.5 between the age groups. When grouping results by weight class, similar patterns occur, as growth and feeding rates decrease consistently as cuttlefish grow bigger. Highest mean growth and feeding rates are obtained by hatchlings (〈 0.1 g) with 12.4 ± 4.5 and 35.3 ± 15.1%BWd−1, respectively, while the lowest growth and feeding rates were recorded for the largest animals, between 15 and 25 g (3.4 ± 1.1 and 10.8 ± 4.1%BWd−1 respectively). For these weight classes, mean food conversions varied between 2.7 ± 0.9 and 3.8 ± 2.8.

Description: 1. The rich zooplankton, fish and squid resources on the Patagonian Shelf sustain substantial populations of largely resident seabirds and marine mammals. These habitats are also visited seasonally by similar species from elsewhere but few data exist on their status and origin. Recent studies, using satellite-tracking to determine foraging ranges and feeding areas of seabirds and marine mammals breeding at South Georgia, have shown that several species make substantial use of the waters of the Patagonian Shelf. 2. Wandering albatrosses use shelf-edge areas year-round with direct observations of both sexes of almost all age classes, including, breeding, pre-breeding and non-breeding individuals. White-chinned petrels and female Northern and Southern giant petrels mainly visit during incubation and post-breeding, particularly to the Falklands Current (White-chinned petrels) and to upwelling areas around the southern shelf-break from the Burdwood Bank in the east to Staten Island and Diego Ramirez in the west (giant petrels). Northern giant petrel males during incubation and Antarctic fur seals in winter reach inner shelf habitats in the northern sector. In contrast, South Georgia populations of black-browed and grey-headed albatrosses do not appear to use the Patagonian Shelf at any stage of their breeding cycle. 3. Although the use of the Patagonian Shelf by visiting species is now best documented for South Georgia species, recent observational data confirm that seabirds from Diego Ramirez, Tristan da Cunha and Gough visit the southern and northern sectors, during both breeding and non-breeding seasons respectively. Several Antarctic species (notably Antarctic fulmar and cape petrel) winter in the region as do at least two albatross species from New Zealand; other species (especially Wilson's storm petrels) use it as a staging ground on migration, as do several species of baleen whales and possibly other cetacean species. 4. Three of the seabird species which breed on the Patagonian Shelf are Globally Threatened; seven of the visiting species (and four baleen whale species) also have this status. The Patagonian Shelf is, therefore, not only of global importance for the diversity and abundance of its resident top predators but is just as critical for the survival of many visiting species, some of which are even more endangered. 5. Combining data from satellite-tracking with conventional mapping from direct observations offers the prospect of defining the foraging ranges (and the main feeding areas within these) of a range of key top predator species. Such data should be used, in conjunction with similar information of the distributions of fish, squid and zooplankton resources and of fishing effort, to identify critical marine habitats whose precautionary, multiple-use sustainable management will be vital to protect the interests of both commercial fishers and top predators.

Description: The convergent margin of the central Sunda Arc in Indonesia was the target of a reflection and refraction seismic survey conducted in 1998 and 1999. Along two seismic lines across the subduction complex off southern Sumatra and off Sunda Strait, coincident multichannel and wide-angle data were collected, complemented by two refraction strike-lines in the forearc basin off Sumatra. The combined analysis of the acquired data allows us to present a detailed model of the subduction zone where initiation of strain partitioning occurs due to the onset of oblique subduction. The dip of the subducted plate is well defined along both dip-lines and a lateral increase from 5° to 7° from beneath the outer high off Sumatra to Sunda Strait is supported by complementary gravity modelling. The downgoing slab is traced to a depth of more than 30km. On both reflection dip-lines, a clearly developed backstop structure underlying a trench slope break defines the landward termination of the active accretionary prism and separates it from the outer high. Active subduction accretion is supported by laterally increasing velocities between the deformation front and the active backstop structure. Seismic velocities of the outer high are moderate along both lines (〈5.8kms−1 at 20km depth), suggesting a sedimentary composition. Reduced reflectivity beneath a rugged top basement traced along the outer high of both dip-lines supports a high degree of deformation and material compaction. Several kilometres of sediment has accumulated in the forearc domain, although a distinct morphological basin is only recognized off southern Sumatra and is not developed off Sunda Strait. The bathymetric elevation of the Java shelf that is encountered in the southern Sunda Strait corresponds to increased velocities of a basement high there and is connected to extensional structures of the Sunda Strait transtensional basin. Differences observed in the morphology of the forearc domain are also reflected in the lower crustal structure. Off southern Sumatra, the velocity–depth model clearly indicates a continental-type crust underlying the forearc basin, whereas lower velocities are found beneath the Sunda Strait forearc domain. Off Sumatra, some 3-D constraint on the upper plate structure is gained from the refraction strike-lines, which in addition is supported by synthetic data modelling.

Description: This paper presents high-precision U–Pb ages and initial Hf isotopic compositions of zircon from mafic to felsic rocks of the Kohistan Arc Complex, Pakistan. Three magmatic pulses tapping geochemically different reservoirs are distinguished. Partial melting of mantle with MORB-type isotopic characteristics generated 99–92-Ma-old magmas. Plutonism around 85 Ma tapped a more fertile mantle source, most likely consisting of a 〉600-Ma-old metasomatically enriched mantle, or of mantle contaminated by an old sedimentary component; 82-Ma-old felsic peraluminous dykes have MORB-type isotopic compositions considered to be inherited from remelting earlier magmas in the deep base of the arc. The isotopic results demonstrate several and rather rapid changes in melt source region during arc development. They also show that there was subordinate continental influence and negligible importance of slab components for the Hf budget during the generation of the Kohistan Arc Complex.

Description: Alkaline phosphatase activities of the diazotrophic marine cyanobacterium Trichodesmium were studied among natural populations in the northern Red Sea and in laboratory cultures of Trichodesmium sp. strain WH9601. Open‐water tuft‐shaped colonies of Trichodesmium showed high alkaline phosphatase activities with 2.4–11.7 μmol p‐nitrophenylphosphate (PNPP) hydrolyzed·μg chl a−1·h−1, irrespective of date or origin of the sample. Coastal populations of the Trichodesmium tuft colonies had low alkaline phosphatase activities with 0.2–0.5 μmol PNPP·μg chl a−1·h−1. An exception was the Trichodesmium fall maximum, when both tuft colonies and the plankton community (〈100 μm) had alkaline phosphatase activities of 0.6–7.4 μmol PNPP·μg chl a−1·h−1. Likewise, the more rare puff and bow‐tie colonies of Trichodesmium spp. in coastal waters had elevated alkaline phosphatase activities (0.8–1.6 μmol PNPP·μg chl a−1·h−1) as compared with tuft colonies coinhabiting the same waters. Intact filaments of tuft‐forming Trichodesmium sp. strain WH9601 from phosphate‐replete cultures had a base alkaline phosphatase activity of 0.5 μmol PNPP·μg chl a−1·h−1. This activity underwent a 10‐fold increase in phosphate‐deplete cultures and in cultures supplied with glycerophosphate as the sole P source. The elevated level of alkaline phosphatase activity was sustained in P‐deplete cultures, but it declined in cultures with glycerophosphate. The decline is suggested to result from feedback repression of alkaline phosphatase synthesis by the phosphate generated in the glycerophosphate hydrolysis. The enhanced alkaline phosphatase activities of Trichodesmium spp. populations provide evidence that P stress is an important factor in the ecology of Trichodesmium in the northern Red Sea.

Description: An approximation to the traveltime field is calculated for an elastic wave that propagates in a homogeneous anisotropic layer and is reflected at a plane boundary. The traveltime is approximated by a Taylor series expansion with the third derivative of the traveltime being taken into account. The coefficients of the series refer to the seismic ray, which is locally the fastest ray. Simple formulae are obtained for orthorhombic media in the crystal coordinate system, which relate the traveltimes of the reflected waves to the elastic constants of the medium. A numerical example is presented for wave propagation in orthorhombic olivine, which is a constituent of the Earth's mantle. A second example is given by an isotropic host rock with a set of parallel cracks, which is an important model for wave propagation in the Earth's crust. The elastic parameters can be determined by measuring the reflection times as a function of source–receiver offset. The approximate traveltime–distance curves are compared with traveltimes obtained from seismic ray tracing.

Description: The differences in the impact of two major groups of herbivorous zooplankton (Cladocera and Copepoda) on summer phytoplankton in a mesotrophic lake were studied. Field experiments were performed in which phytoplankton were exposed to different densities of two major types of herbivorous zooplankton, cladocerans and copepods. Contrary to expectation, neither of the two zooplankton groups significantly reduced phytoplankton biomass. However, there were strong and contrasting impacts on phytoplankton size structure and on individual taxa. Cladocerans suppressed small phytoplankton, while copepods suppressed large phytoplankton. The unaffected size classes compensated for the loss of those affected by enhanced growth. After contamination of the copepod mesocosms with the cladoceran Daphnia, the combined impact of both zooplankton groups caused a decline in total phytoplankton biomass.

Description: Fungi or bacteria that produce secondary metabolites often have the potential to bring up various compounds from a single strain. The molecular basis for this well-known observation was confirmed in the last few years by several sequencing projects of different microorganisms. Besides well-known examples about induction of a selected biosynthesis (for example, by high- or low-phosphate cultivation media), no overview about the potential in this field for finding natural products was given. We have investigated the systematic alteration of easily accessible cultivation parameters (for example, media composition, aeration, culture vessel, addition of enzyme inhibitors) in order to increase the number of secondary metabolites available from one microbial source. We termed this way of revealing nature's chemical diversity the 'OSMAC (One Strain–Many Compounds) approach' and by using it we were able to isolate up to 20 different metabolites in yields up to 2.6 g L−1from a single organism. These compounds cover nearly all major natural product families, and in some cases the high production titer opens new possibilities for semisynthetic methods to enhance even more the chemical diversity of selected compounds. The OSMAC approach offers a good alternative to industrial high-throughput screening that focuses on the active principle in a distinct bioassay. In consequence, the detection of additional compounds that might be of interest as lead structures in further bioassays is impossible and clearly demonstrates the deficiency of the industrial procedure. Furthermore, our approach seems to be a useful tool to detect those metabolites that are postulated to be the final products of an amazing number of typical secondary metabolite gene clusters identified in several microorganisms. If one assumes a (more or less) defined reservoir of genetic possibilities for several biosynthetic pathways in one strain that is used for a highly flexible production of secondary metabolites depending on the environment, the OSMAC approach might give more insight into the role of secondary metabolism in the microbial community or during the evolution of life itself.