ALBERT

Description: Palaeoenvironmental records from permafrost sequences complemented by infrared stimulated luminescence (IRSL) and 230Th/U dates from Bol'shoy Lyakhovsky Island (73°20′N, 141°30′E) document the environmental history in the region for at least the past 200 ka. Pollen spectra and insect fauna indicate that relatively wet grasssedge tundra habitats dominated during an interstadial c. 200-170 ka BP. Summers were rather warm and wet, while stable isotopes reflect severe winter conditions. The pollen spectra reflect sparser grass-sedge vegetation during a Taz (Late Saalian) stage, c. 170-130 ka BP, with environmental conditions much more severe compared with the previous interstadial. Open Poaceae and Artemisia plant associations dominated vegetation at the beginning of the Kazantsevo (Eemian) c. 130 ka BP. Some shrubs (Alnus fruticosa, Salix, Betula nana) grew in more protected and wetter places as well. The climate was relatively warm during this time, resulting in the melting of Saalian ice wedges. Later, during the interglacial optimum, shrub tundra with Alnus fruticosa and Betula nana s.l. dominated vegetation. Climate was relatively wet and warm. Quantitative pollen-based climate reconstruction suggests that mean July temperatures were 4-5°C higher than the present during the optimum of the Eemian, while late Eemian records indicate significant climate deterioration. © 2004 Taylor & Francis.

Description: Late Quaternary permafrost deposits on Big Lyakhovsky Island (New Siberian Islands, Russian Arctic) were studied with the aim of reconstructing the palaeoclimatic and palaeoenvironmental conditions of northern Siberia. Hydrogen and oxygen stable isotope analyses are presented for six different generations of ice wedges as well as for recent ice wedges and precipitation. An age of about 200 ka BP was determined for an autochtonous peat layer in ice-rich deposits by U/Th method, containing the oldest ice wedges ever analysed for hydrogen and oxygen isotopes. The palaeoclimatic reconstruction revealed a period of severe winter temperatures at that time. After a gap in the sedimentation history of several tens of thousands of years, ice-wedge growth was re-initiated around 50 ka BP by a short period of extremely cold winters and rapid sedimentation leading to ice-wedge burial and characteristic ice-soil wedges (‘polosatics’). This corresponds to the initial stage for the Late Weichselian Ice Complex, a peculiar cryolithogenic periglacial formation typical of the lowlands of northern Siberia. The Ice Complex ice wedges reflect cold winters and similar climatic conditions as around 200 ka BP. With a sharp rise in υ18O of 6‰ and υD of 40‰, the warming trend between Pleistocene and Holocene ice wedges is documented. Stable isotope data of recent ice wedges show that Big Lyakhovsky Island has never been as warm in winter as today.

Description: The reproductive system is described from 15 giant squid Architeuthis sp., collected between 1972 and 2002 in South African waters. Distinctive features of the male reproductive system are the long muscular terminal organ, with elaboration of the anterior end, and modification of the tips of the ventral arms, probably hectocotilization. The spermatophoric organ has a long finishing gland that extends from the base of the gill. The terminal organ is differentiated internally into three distinct parts, involved in the guidance, storage, protection, expulsion and possibly the coating of spermatophores. Length of spermatophores in the terminal organ varied considerably. Several stages of spermatophores were found, from tentative to false to fully formed spermatophores, within a single animal. Distinctive features of the female reproductive system are a mesentery surrounding the main blood vessels of the ovary and attaching the ovary to the dorsal gladius chamber, multiple branching (at least three times) of the genital aorta that supplies the developing oocytes, high potential fecundity (3.5–6.2 ± 106 oocytes), small eggs and short oviducts that suggest intermittent (extended) spawning. Large concentrations and single spermatangia were found in various places in females, indicating non-specific deposition. The transfer of spermatophores is probably rapid, perhaps because of considerable sexual size dimorphism (at maturity, males are much smaller than females). Implants in males are probably self-induced since the majority were found within reach of the terminal organ opening (primarily on the ventral arms in males).

Description: A type of apparent photoreceptor, the nuchal organ, is described in the sepiolid squid Euprymna scolopes. These vesicles are identified in a variety of other cephalopod species. The nuchal organs have specific structural similarities to the already well-described photosensitive vesicles. Both organs have a distinct vesiculate structure and possess a rind consisting of several types of cells. Certain rind cells from both organs send processes with microvilli into the lumen of the vesicle forming a core area. Within the cores of both organs numerous microvilli occupy much of the core volume. These histological similarities provide strong evidence that the nuchal organs, like the photosensitive vesicles, are photoreceptors. Three distinct differences also exist between the nuchal organs and photosensitive vesicles: (1) the location of the nuchal organs differs from that of all known photosensitive vesicles in cephalopods; (2) the location of the nuchal organs is highly conservative in decapod cephalopods compared to the varying locations of the photosensitive vesicles; (3) the degree of structural order generally found within photosensitive vesicles is not apparent in the nuchal organs. The function of the nuchal organ is probably different from previously described photoreceptors in cephalopods.

Description: A mature female Galiteuthis glacialis (430 mm mantle length) was caught south of the Falkland Islands (53°S, 58°W) at a depth of 976-1001 m over a bottom depth of 1582-2378 m. A total of 8 spermatangia (15-19 mm in length) were found inserted into the mantle wall, which was of gelatinous consistency. Its ovary contained 3 605±42 oocytes, mostly 2.2-2.5 mm in length, and there were 21 ripe eggs (3.0-3.2±2.2-2.7 mm) in the oviducts. Only one resorpting oocyte (1.4 mm) was found. This is the only description of a mature female of this species, though two spent females have been previously described and three more mentioned by other authors.

Description: The Patagonian longfin squid Loligo gahi undertakes horizontal ontogenetic migrations on the Falkland shelf: juveniles move from spawning grounds located in shallow, inshore waters (20–50 m depths) to feeding grounds near the shelf edge (200–350 m depths). Immature squid feed and grow in these offshore feeding grounds and, upon maturation, migrate back to inshore waters to spawn. The possible influence of environmental factors on L. gahi migrations was investigated using data from oceanographic transects, crossing the region of known L. gahi occurrence. They were made from the inshore waters of East Falkland eastwards to depths of 1250 m on a monthly basis from 1999 to 2001. Four main water types were found in the region: Shelf, Sub-Antarctic Superficial and Antarctic Intermediate water masses, and Transient Zone waters. The inshore spawning grounds occur in the Shelf Water mass, whereas the feeding squid (medium-sized immature and maturing individuals) were associated with the Transient Zone. The 5.5°C isotherm appeared to mark the limit of squid distribution into deeper waters in all seasons. Seasonal changes in water mass characteristics and location were found to be important for seasonal changes in L. gahi migrations on the Falkland shelf.

Description: A microsatellite dinucleotide-enriched library was obtained from the European squid (Loligo vulgaris) and five species-specific dinucleotide markers were optimized. These markers are highly polymorphic with average expected heterozygosity ranging from 0.706 to 0.927 and allele number ranging from 7 to 17. This set of primers is suitable for population genetic studies.

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: 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: 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: 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: 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: 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: he gut contents of a female specimen of Graneledone cf. boreopacifica collected from the caldera wall of Axial Volcano, near an active hydrothermal vent in the Northeast Pacific Ocean are reported. At least 30 individual gastropods and 46 individual polychaetes are represented in the gut contents by hard parts. Shell fragments and shells removed from the gut allow ready identification of the gastropods Provanna variabilis and Lepetodrilus fucensis, both of which are known only from North Pacific hydrothermal vents. Jaws of polychaete worms are identified as those of the nereidid, Nereis piscesae, and the predatory polynoids, Levensteiniella kincaidi and an unidentified species in the subfamily Branchinotogluminae. Not only was a considerable volume of prey hard parts ingested, the gastropod shells had been crushed before being ingested. The large size of the beaks in this genus of octopus and the increased area they offer for insertion of the superior mandible muscle, the prime mover in beak closure, support the hypothesis that these beaks exert sufficient force to crush the gastropod shells. Although cephalopods had been reported to be absent from hydrothermal vents, the data presented here demonstrate that not only do they occur in vent habitats, they actively prey on vent fauna.

Description: The sepiolid squid Euprymna scolopes forms a bioluminescent mutualism with the luminous bacterium Vibrio fischeri, harboring V. fischeri cells in a complex ventral light organ and using the bacterial light in predator avoidance. To characterize the contribution of V. fischeri to the growth and development of E. scolopes and to define the long-term effects of bacterial colonization on light organ morphogenesis, we developed a mariculture system for the culture of E. scolopes from hatching to adulthood, employing artificial seawater, lighting that mimicked that of the natural environment, and provision of prey sized to match the developmental stage of E. scolopes. Animals colonized by V. fischeri and animals cultured in the absence of V. fischeri (aposymbiotic) grew and survived equally well, developed similarly, and reached sexual maturity at a similar age. Development of the light organ accessory tissues (lens, reflectors, and ink sac) was similar in colonized and aposymbiotic animals with no obvious morphometric or histological differences. Colonization by V. fischeri influenced regression of the ciliated epithelial appendages (CEAs), the long-term growth of the light organ epithelial tubules, and the appearance of the cells composing the ciliated ducts, which exhibit characteristics of secretory tissue. In certain cases, aposymbiotic animals retained the CEAs in a partially regressed state and remained competent to initiate symbiosis with V. fischeri into adulthood. In other cases, the CEAs regressed fully in aposymbiotic animals, and these animals were not colonizable. The results demonstrate that V. fischeri is not required for normal growth and development of the animal or for development of the accessory light organ tissues and that morphogenesis of only those tissues coming in contact with the bacteria (CEAs, ciliated ducts, and light organ epithelium) is altered by bacterial colonization of the light organ. Therefore, V. fischeri apparently makes no major metabolic contribution to E. scolopes beyond light production, and post-embryonic development of the light organ is essentially symbiont independent.

Description: Morphology of statoliths and anatomy of statocysts were studied in five species of Gonatidae, Moroteuthis robusta (Onychoteuthidae) and Galiteuthis phyllura (Cranchiidae) from the northern Bering Sea, and Todarodes pacificus (Ommastrephidae) from the Pacific waters near Japan. A special experiment was carried out in order to observe statolith mobility on the macula statica and possible endolymph flows within the statocyst in freshly caught gonatid squid Berryteuthis magister. It was found that the statolith may deviate at small acute angles around three axes running through its centre of rotation (located near the spur) without any visual damage of its attachment area to the macula. This finding enabled us to re-consider previous theories and to create a new model of the squid statocyst functioning with the statolith as detector of multidimensional movement. Two types of statolith morphology are distinguished: demersal type statoliths characteristic of near-bottom decapods, and pelagic type statoliths characteristic of all pelagic squids and not dependent on their systematic position. Phylogenetic and ecological features of the statocyst and statolith structure are established. Possible evolutionary trends in development of different types of statocysts in decapods are discussed.

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: The isolation and structure elucidation of two new oleanane-type triterpene glycosides, 29-(β-D-glucopyranosyloxy)-2α,3β,23-trihydroxyolean-12-en-28-oic acid (=(2α,3β,4α,29α)-29-(β-D-glucopyranosyloxy)-2,3,23-trihydroxyolean-12-en-28-oic acid; 1) and its C(20)-epimer, 30-(β-D-glucopyranosyloxy)-2α,3β,23-trihydroxyolean-12-en-28-oic acid (=(2α,3β,4α,29β)-29-β-D-glucopyranosyloxy)-2,3,23-trihydroxyolean-12-en-28-oic acid; 2), and a novel nortriterpene glycoside, (17S)-2α,18β,23-trihydroxy-3,19-dioxo-19(18[RIGHTWARDS ARROW]17)- abeo-28-norolean-12-en-25-oic acid β-D-glucopyranosyl ester (=(1R,2S,4aS,4bR,6aR,7R,9R,10aS,10bS)-3,4,4a,4b,5,6,6a,7,8,9,10,10a,10b,11-tetradecahydro-1-hydroxy-7-(hydroxymethyl)-3′,4′,4a,4b,7-pentamethyl-2′,8- dioxospiro[chrysene-2(1H),1′-cyclopentane]-10a-carboxylic acid β-D-glucopyranosyl ester; 3) from Phlomis viscosa (Lamiaceae) are reported. The structures of the compounds were asigned by means of spectroscopic (IR, 1D- and 2D-NMR, and LC-ESI-MS) and chemical (acetylation) methods.

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: The region of north Iceland is highly sensitive climatically owing to its location with respect to atmospheric and oceanographic fronts. In this study we present total carbonate and δ18O records of benthic and planktic Foraminifera from nine sediment cores from the North Iceland Shelf. The results of this work indicate that the deglaciation of the Vestfirdir Peninsula was completed by 10 200 cal. yr BP. The 8200 cal. yr BP cold event is present only as a minor isotopic event, and seems not to have had much of a cooling effect on the bottom waters of the northwest Iceland shelf. The Holocene maximum warmth, attributed to a stronger North Icelandic Irminger Current, occurred between ca. 7800 and 6200 cal. yr BP. Over the past 4500 cal. yr BP a general cooling trend has occurred on the North Iceland Shelf, and superimposed on this overall cooling trend are a number of oscillations between periods when relatively warmer and cooler waters occupied the shelf. Relatively cooler waters were present at 4200–4000 cal. yr BP, 3200–2900 cal. yr BP, 2500–2350 cal. yr BP and 600–200 cal. yr BP, whereas relatively warmer waters were present on the shelf at 3750–3450 cal. yr BP, 2800–2600 cal. yr BP and 1700–1000 cal. yr BP.

Description: Elicitation of Gracilaria conferta (Schousboe ex Montagne) J. ct G. Feldmann with oligoagars resulted in a defense response that was strong enough to kill epiphytic bacteria associated with the alga. Up to 60% of the resident bacterial flora of healthy plants was eliminated within 60 min after addition of neoagarohexaose to the algal medium. Single isolates of agar-degrading bacteria that had been isolated previously from healthy or decaying algal tissues proved to be more sensitive, Some of them were generally unable to survive on healthy G, conferta. Others survived on unelicited plants. Approximately 90% of these more resistant agar degraders were eliminated within 15 min after elicitation. The bacterial degradation of dead tissue of G, conferta resulted in a release of elicitors. The elicitors accumulated in the medium and reached high enough concentrations within 24 h to induce a hypersensitive response in healthy algae, The eliciting agent could be destroyed with beta -agarase and was thus probably oligoagar, Application of antibiotics prevented the accumulation of the elicitor, which indicated that bacteria were responsible for its release from the algal biomass, The hypersensitive response of G. conferta after contact with oligoagars is thus a true defense response, because it enables the plant to protect itself efficiently from enzymatic attacks on its cell wall.

Description: Five microsatellite markers were developed for the snow crab (Chionoecetes opilio) and polymerase chain reaction conditions and/or primer sequences of three previously developed microsatellites were adapted for fluorescent labelling analysis. All loci were analysed in 449 individuals from 11 sampling sites in the northwest Atlantic. The high degree of polymorphism exhibited by these microsatellites (mean of 34 alleles per locus and mean observed heterozygosity of 0.76) suggests that they will be suitable for spatial and temporal genetic analysis of C. opilio populations.

Description: Deep‐sea drilling in the Antarctic region (Deep‐Sea Drilling Project legs 28, 29, 35, and 36) has provided many new data about the development of circum‐Antarctic circulation and the closely related glacial evolution of Antarctica. The Antarctic continent has been in a high‐latitude position since the middle to late Mesozoic. Glaciation commenced much later, in the middle Tertiary, demonstrating that near‐polar position is not sufficient for glacial development. Instead, continental glaciation developed as the present‐day Southern Ocean circulation system became established when obstructing land masses moved aside. During the Paleocene (t = ∼65 to 55 m.y. ago), Australia and Antarctica were joined. In the early Eocene (t = ∼55 m.y. ago), Australia began to drift northward from Antarctica, forming an ocean, although circum‐Antarctic flow was blocked by the continental South Tasman Rise and Tasmania. During the Eocene (t = 55 to 38 m.y. ago) the Southern Ocean was relatively warm and the continent largely nonglaciated. Cool temperate vegetation existed in some regions. By the late Eocene (t = ∼39 m.y. ago) a shallow water connection had developed between the southern Indian and Pacific oceans over the South Tasman Rise. The first major climatic‐glacial threshold was crossed 38 m.y. ago near the Eocene‐Oligocene boundary, when substantial Antarctic sea ice began to form. This resulted in a rapid temperature drop in bottom waters of about 5°C and a major crisis in deep‐sea faunas. Thermohaline oceanic circulation was initiated at this time much like that of the present day. The resulting change in climatic regime increased bottom water activity over wide areas of the deep ocean basins, creating much sediment erosion, especially in western parts of oceans. A major (∼2000 m) and apparently rapid deepening also occurred in the calcium carbonate compensation depth (CCD). This climatic threshold was crossed as a result of the gradual isolation of Antarctica from Australia and perhaps the opening of the Drake Passage. During the Oligocene (t = 38 to 22 m.y. ago), widespread glaciation probably occurred throughout Antarctica, although no ice cap existed. By the middle to late Oligocene (t = ∼30 to 25 m.y. ago), deep‐seated circum‐Antarctic flow had developed south of the South Tasman Rise, as this had separated sufficiently from Victoria Land, Antarctica. Major reorganization resulted in southern hemisphere deep‐sea sediment distribution patterns. The next principal climatic threshold was crossed during the middle Miocene (t = 14 to 11 m.y. ago) when the Antarctic ice cap formed. This occurred at about the time of closure of the Australian‐Indonesian deep‐sea passage. During the early Miocene, calcareous biogenic sediments began to be displaced northward by siliceous biogenic sediments with higher rates of sedimentation reflecting the beginning of circulation related to the development of the Antarctic Convergence. Since the middle Miocene the East Antarctic ice cap has remained a semipermanent feature exhibiting some changes in volume. The most important of these occurred during the latest Miocene (t = ∼5 m.y. ago) when ice volumes increased beyond those of the present day. This event was related to global climatic cooling, a rapid northward movement of about 300 km of the Antarctic Convergence, and a eustatic sea level drop that may have been partly responsible for the isolation of the Mediterranean basin. Northern hemisphere ice sheet development began about 2.5–3 m.y. ago, representing the next major global climatic threshold, and was followed by the well‐known major oscillations in northern ice sheets. In the Southern Ocean the Quaternary marks a peak in activity of oceanic circulation as reflected by widespread deep‐sea erosion, very high biogenic productivity at the Antarctic Convergence and resulting high rates of biogenic sedimentation, and maximum northward distribution of ice‐rafted debris.

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: 1. Density gradients of cladocerans and copepods were generated in an enclosure experiment to compare the impact on the plankton of a filter feeder (Daphnia hyalina × galeata) with that of more selective feeders (calanoid and cyclopoid copepods). The experiment was conducted in situ over 25 days during spring in a mesotrophic lake, Schöhsee, Germany. 2. The plankton community was monitored regularly. Daphniids were able to graze on the phytoplankton present, which mainly consisted of small (〈1000 μm3) species, whereas copepods did not show any impact on algae. 3. At the end of the experiment, Daphnia and remaining cyclopoid copepods were harvested and sorted manually, prior to analyses for stable isotopes of carbon and nitrogen. Daphniids from mesocosms stocked purely with differing densities of Daphnia showed little variability in stable isotope values, whereas those that thrived in enclosure bags together with copepods exhibited lower δ13C values. 4. The change in Daphniaδ13C indicates a change of food sources, modified by the presence of the copepods: the higher the mean abundance of copepods in the enclosures, the more 13C-depleted the daphniids. Increasing abundance of high nucleic acid (HNA) bacteria in the copepod bags may account for the trend in Daphniaδ13C via increased grazing on the bacteria themselves, or via grazing on phytoplankton utilising isotopically light CO2 from respiratory release. 5. Cyclopoid copepod stable isotope signatures were related to Daphnia and copepod abundances in copepod bags, suggesting that cyclopoids preyed on the available zooplankton.

Description: Stable oxygen and carbon isotope profiles from modern bivalve shells were investigated in order to reconstruct short-term hydrographical changes in the river-shelf system of the Laptev Sea. Oxygen isotopic profiles obtained from the aragonitic species Astarte borealis exhibit amplitude cycles interpreted as annual hydrographical cycles. These records reflect the strong contrast between summer and winter bottom water conditions in the Laptev Sea. The seasonal variations in δ18O are mainly controlled by the riverine freshwater discharge during summer with 0.5‰ per salinity unit. Corrected for a defined species-dependent fractionation offset of -0.37‰, time-dependent salinity records were reconstructed from these δ18O profiles. They indicate a good correspondence to seasonal hydrographic changes and synoptical data. Persistent trends with shell growth towards more negative δ13C values are observed in all specimens and appear to be related to metabolic changes of the bivalves during ontogeny. In contrast, short-term fluctuations are likely linked to seasonal variabilities of the river water outflow patterns and enhanced phytoplankton productivity during summer. This is corroborated by a clear watermass-related distinction of the various δ13C records made on the basis of water depth and distance from the riverine source.

Description: A recent meta-analysis indicates that trophic cascades (indirect effects of predators on plants via herbivores) are weak in marine plankton in striking contrast to freshwater plankton (Shurin et al. 2002, Ecol. Lett., 5, 785–791). Here we show that in a marine plankton community consisting of jellyfish, calanoid copepods and algae, jellyfish predation consistently reduced copepods but produced two distinct, opposite responses of algal biomass. Calanoid copepods act as a switch between alternative trophic cascades along food chains of different length and with counteracting effects on algal biomass. Copepods reduced large algae but simultaneously promoted small algae by feeding on ciliates. The net effect of jellyfish on total algal biomass was positive when large algae were initially abundant in the phytoplankton, negative when small algae were dominant, but zero when experiments were analysed in combination. In contrast to marine systems, major pathways of energy flow in Daphnia-dominated freshwater systems are of similar chain length. Thus, differences in the length of alternative, parallel food chains may explain the apparent discrepancy in trophic cascade strength between freshwater and marine planktonic systems.

Description: A total of five sediment cores from three sites, the Arctic Ocean, the Fram Strait and the Greenland Sea, yielded evidence for geomagnetic reversal excursions and associated strong lows in relative palaeointensity during oxygen isotope stages 2 and 3. A general similarity of the obtained relative palaeointensity curves to reference data can be observed. However, in the very detail, results from this high‐resolution study differ from published records in a way that the prominent Laschamp excursion is clearly characterized by a significant field recovery when reaching the steepest negative inclinations, whereas only the N–R and R–N transitions are associated with the lowest values. Two subsequent excursions also reach nearly reversed inclinations but without any field recovery at that state. A total of 41 accelerator mass spectrometry (AMS) 14C ages appeared to allow a better age determination of these three directional excursions and related relative palaeointensity variations. However, although the three sites yielded more or less consistent chronological as well as palaeomagnetic results a comparison to another site, PS2644 in the Iceland Sea, revealed significant divergences in the ages of the geomagnetic field excursions of up to 4 ka even on basis of uncalibrated AMS 14C ages. This shift to older 14C ages cannot be explained by a time‐transgressive character of the excursions, because the distance between the sites is small when compared with the size of and the distance to the geodynamo in the Earth's outer core. The most likely explanation is a difference of reservoir ages and/or mixing with old 14C‐depleted CO2 from glacier ice expelled from Greenland at site PS2644.

Description: A three-dimensional hydrodynamic model has been used to analyse temporally and spatially resolved circulation patterns in the Baltic Sea with special emphasis on drifting particles representing larval fish. The main purpose of this study was (i) to investigate potential drift patterns of larval fish, (ii) to identify its intra- and inter-annual variability for time periods based on the timing of spawning and (iii) to analyse its seasonal and spatial variability in dependence of the atmospheric forcing conditions. For the time period 1979–1998 temporally and spatially resolved simulated flow fields were used to describe the potential drift from the centre of main reproductive effort of Baltic cod (Gadus morhua). The results of the model runs demonstrate a general change in circulation pattern from retention during a first decade (1979–1988) to dispersion in the following decade (1989–1998). This increase in dispersion was related to an increase in the variability of the local wind forcing conditions over the Baltic. The more frequent occurrence of dispersion in spring of the recent decade was accompanied by a strong decay in biomass of one of the main larval fish feeding component in the central basin, the calanoid copepod Pseudocalanus elongatus. Larger dispersion of this prey organism may have affected the spatial overlap and thus the contact rates between predator and prey. Hence, this may have resulted in a food limitation for early life stages of Baltic cod and potentially contributed to the pronounced shift in cod peak spawning time from spring to late summer. Early life stages of cod originating from late spawning fish, benefited from a stronger dispersion in late summer and autumn, into shallow coastal areas with higher calanoid abundance.

Description: Sediment proxy records from a continuous, 1.5 million year long deep-sea sediment core from a site in the western Norwegian Sea were used to obtain new insights into the nature of palaeoceanographic change in the northern North Atlantic (Nordic seas) during the climatic shift of the Mid-Pleistocene Revolution (MPR). Red-green sediment colour and magnetic susceptibility records both reveal significant differences in their mean values when comparing the intervals older than 700 000 yr (700 ka) with those from the past 500 kyr. The timing and duration of these changes indicates that the MPR in the Nordic seas is characterised by a gradual transition lasting about 200 kyr. Together with further sedimentological evidence this suggests that the mid-Pleistocene climate shift was accompanied by a general change in ice-drift pattern. It is further proposed that prior to the onset of the major late Pleistocene glaciations in the Northern Hemisphere a significant proportion of the ice in the eastern Nordic seas originated from a southern provenance, whereas later it dominantly came from the surrounding landmasses.

Description: Notations for Cd stable isotope compositions and the use of reference materials are discussed. It is proposed that Cd stable isotope data should be reported as variations of the 114Cd/110Cd ratio/ using either the δ114/110Cd or ε114/110Cd notations. Future publications should report results for BAM-1012 Cd, the only currently available international Cd isotope reference material. It is also recommended that “Münster Cd” and a range of specified geological reference materials are used as additional reference materials. The final choice of a primary “zero-delta” reference standard remains the most important outstanding question.

Description: Standard length, dry mass and RNA : DNA ratio measurements of 3876 Atlantic cod Gadus morhua larvae and juveniles from 26 families of recruit (fish during their first year of spawning) and repeat spawners (fish which were in their subsequent spawning season) reared in two mesocosms (2500 and 4400 m3) under semi-natural conditions were analysed over a period of 10 weeks using microsatellites. Larvae from recruit spawners were significantly longer and heavier at hatch and throughout the 10 weeks. RNA : DNA ratios from recruit spawner offspring were only significantly higher at week 1. The smaller (2500 m3) mesocosm was characterized by low plankton density during the transition from endogenous to exogenous feeding followed by a higher density during the metamorphosis period (weeks 4 and 5), with the reverse pattern evident in the 4400 m3 mesocosm. Patterns of larval growth followed patterns of zooplankton density. Significant differences in RNA : DNA ratios between the mesocosms at all comparable sampling dates were found and within each mesocosm individual fish exhibited a wide range of growth and condition responses under the same environmental conditions. RNA : DNA ratios as a function of size differed in the amount of variability between mesocosms, indicating that the higher food density led to a higher proportion of well-conditioned larvae in the first 3 weeks. Food availability probably has a major role in determining offspring growth and condition, with limited effects due to maternal effects in cases where the broodstock females are approximately of similar size and condition.

Description: Empirical relationships are presented to estimate in fishes, asymptotic length (L∞) from maximum observed length (Lmax), length at first maturity (Lm) from L∞, life span (tmax) from age at first maturity (tm), and length at maximum possible yield per recruit (Lopt) from L∞ and from Lm, respectively. The age at Lopt is found to be a good indicator of generation time in fishes. A spreadsheet containing the various equations can be downloaded from the Internet at http://www.fishbase.org/download as popdynJFB.zip. A simple method is presented for evaluation of length–frequency data in their relationship to L∞, Lm and Lopt. This can be used to evaluate the quality of the length–frequency sample and the status of the population. Three examples demonstrate the usefulness of this method. 2000 The Fisheries Society of the British Isles

Description: A proposal is made to standardise the reporting of Ca isotope data to the δ44Ca/40Ca notation (or δ44Ca/42Ca) and to adopt NIST SRM 915a as the reference standard.

Description: Pseudocalanus elongatus is a key species in the pelagic zone of the deep basins of the Central Baltic Sea. The copepod serves as a major food organism for larval as well as for adult, pelagic planktivorous fish. Large interannual fluctuations in the standing stock of P. elongatus have been attributed to significant changes in the hydrographic environment over the last two decades. In particular, the decreasing salinity in the Baltic deep basins, a result of a change in atmospheric forcing leading to an increase in rainfall since the 1980s and of a lack of pulses of saline water intrusions from the North Sea, was found to affect reproduction and maturation of the copepod. In parallel, dramatic changes in the weight-at-age of herring, one of the most important commercial fishes of the Baltic Sea, have been observed since the late 1980s. Using time-series on herring stomach contents, as well as length and weight, we provide evidence for a chain of events relating variability in climate, salinity and P. elongatus abundance to changes in diet and condition of herring in the Central Baltic Sea.

Description: The cyanobacteria Synechococcus and Prochlorococcus are important primary producers in marine ecosystems. Because currently available approaches for estimating microbial growth rates can be difficult to apply in the field, we have been exploring the feasibility of using quantitative rRNA measurements as the basis for making such estimates. In this study we examined the relationship between rRNA and growth rate in several Synechococcus and Prochlorococcus strains over a range of light-regulated growth rates. Whole-cell hybridization with fluorescently labeled peptide nucleic acid (PNA) probes was used in conjunction with flow cytometry to quantify rRNA on a per cell basis. This PNA probing technique allowed rRNA analysis in a phycoerythrin-containing Synechococcus strain (WH7803) and in a non-phycoerythrincontaining strain and in Prochlorococcus. All the strains showed a qualitatively similar tri-phasic relationship between rRNA·cell-1 and growth rate, involving relatively little change in rRNA·cell-1 at low growth rates, linear increase at intermediate growth rates, and a plateau and/or decrease at the highest growth rates. The onset of each phase was associated with the relative, rather than absolute, growth rate of each strain. In the Synechococcus strains, rRNA normalized to flow cytometrically measured forward angle light scatter (an indicator of size) was well-correlated with growth rate across strains. These findings support the idea that cellular rRNA may be useful as an indicator of in situ growth rate in natural Synechococcus and Prochlorococcus populations.

Description: Measurements of the gas vesicle space in steady‐state light or phosphate‐limited cultures of Aphanizomenon flos‐aquae Ralfs, strain 7905 showed that gas vesicle content decreased as energy‐limited growth rate increased hut was the same at several phosphate‐limited growth rates. Upon a decrease in growth irradiance, gas vesicle content did increase in phosphate‐limited cultures, hut the cultures remained nonbuoyant as long as P was limiting. Buoyant, energy‐limited cultures lost their buoyancy in less than 2 h when exposed to higher irradiances. The primary mechanism for buoyancy loss was the accumulation of polysaccharide as ballast. Collapse of gas vesicles by turgor pressure played a minor role in the loss of buoyancy. When cultures were exposed to higher irradiances, cells continued to synthesize gas vesicles at the same rate as before the shift for at least 1 generation time. The amount of ballast required to make individual filaments in the population sink varied 4‐fold. This variation appears to be due to differences in gas vesicle content among individual filaments.

Description: Over the last two decades numerous studies have investigated the structure of the west Iberia continental margin, a non-volcanic margin characterized by a broad continent–ocean transition (COT). However, the nature and structure of the crust of the segment of the margin off SW Iberia is still poorly understood, because of sparse geophysical and geological data coverage. Here we present a 275-km-long multichannel seismic reflection (MCS) profile, line AR01, acquired in E–W direction across the Horseshoe Abyssal Plain, to partially fill the gap of information along the SW Iberia margin. Line AR01 runs across the inferred plate boundary between the Iberian and the African plates during the opening of the Central Atlantic ocean. The boundary separates crust formed during or soon after continental rifting of the SW Iberian margin from normal seafloor spreading oceanic crust of the Central Atlantic ocean. Line AR01 has been processed and pre-stack depth migrated to show the tectonic structure of the crust across the palaeo plate boundary. This boundary is characterized by a 30–40-km-wide zone of large basements highs related to landward-dipping reflections, which penetrate to depths of 13–15 km, and it marks a change in the character of the basement structure and relief from east to west. In this study, we have used pre-stack depth migrated images, the velocity model of line AR01 and magnetic data available in the area to show that the change in basement structure occurs across the fossil plate boundary, separating African oceanic crust of the M series (M21–M16) to the west from the transitional crust of the Iberian margin to the east.

Description: Active seismic investigations along the Pacific margin off Peru were carried out using ocean bottom hydrophones and seismometers. The structure and the P-wave velocities of the obliquely subducting oceanic Nazca Plate and overriding South American Plate from 8°S to 15°S were determined by modelling the wide-angle seismic data combined with the analysis of reflection seismic data. Three detailed cross-sections of the subduction zone of the Peruvian margin and one strike-line across the Lima Basin are presented here. The oceanic crust of the Nazca Plate, with a thin pelagic sediment cover, ranging from 0–200 m, has an average thickness of 6.4 km. At 8°S it thins to 4 km in the area of Trujillo Trough, a graben-like structure. Across the margin, the plate boundary can be traced to 25 km depth. As inferred from the velocity models, a frontal prism exists adjacent to the trench axis and is associated with the steep lower slope. Terrigeneous sediments are proposed to be transported downslope due to gravitational forces and comprise the frontal prism, characterized by low seismic P-wave velocities. The lower slope material accretes against a backstop structure, which is defined by higher seismic P-wave velocities, 3.5–6.0 km s−1. The large variations in surface slope along one transect may reflect basal removal of upper plate material, thus steepening the slope surface. Subduction processes along the Peruvian margin are dominated by tectonic erosion indicated by the large margin taper, the shape and bending of the subducting slab, laterally varying slope angles and the material properties of the overriding continental plate. The erosional mechanisms, frontal and basal erosion, result in the steepening of the slope and consequent slope failure.

Description: We have performed a 3-D seismic refraction tomography of a 48 × 48 km2 area surrounding ODP site 757, which is planned to host an International Ocean Network (ION) permanent seismological observatory, called the Ninetyeast Ridge Observatory (NERO). The study area is located in the southern part of the Ninetyeast Ridge, the trail left by the Kerguelen hotspot on the Indian plate. The GEOMAR Research Centre for Marine Geosciences and the Federal Institute for Geosciences and Natural Resources acquired 18 wide-angle profiles recorded by 23 ocean bottom hydrophones during cruise SO131 of R/V Sonne in spring 1998. We apply a first arrival traveltime tomography technique using regularized inversion to recover the 3-D velocity structure relative to a 1-D background model that was constructed from a priori information and averaged traveltime data. The final velocity model revealed the crustal structure down to approximately 8 km depth. Resolution tests showed that structures with approximately 6 km horizontal extent can reliably be resolved down to that depth. The survey imaged the extrusive layer of the upper crust of the Ninetyeast Ridge, which varies in thickness between 3 and 4 km. A high-velocity anomaly coinciding with a positive magnetic anomaly represents a volcanic centre from which crust in this area is thought to have formed. A pronounced low-velocity anomaly is located underneath a thick sedimentary cover in a bathymetric depression. However, poor ray coverage of the uppermost kilometre of the crust in this area resulted in smearing of the shallow structure to a larger depth. Tests explicitly including the shallow low-velocity layer confirmed the existence of the deeper structure. The heterogeneity of the upper crust as observed by our study will have consequences for the waveforms of earthquake signals to be recorded by the future seismic observatory.

Description: We present depth images, from portions of profiles that are close to flow-lines, of Cretaceous oceanic crust in the eastern Central Atlantic. Compared with post-stack time migrations, the images illustrate the improvement resulting from the application of pre-stack depth migration. The images document the scale and geometry of normal faulting in oceanic crust formed over 25 Myr at a half-spreading rate of less than 10 mm yr−1, and the variation in extensional style with position within the spreading segment. Away from major fault zones (FZs), most faults are subplanar, dip more than 35°, are associated with moderate basement relief (0.2–1 km relief) and may penetrate to deep crustal levels. These faults could be related to the lifting of the lithosphere out of the median valley to the flanking mountains. Also observed away from FZs are gently dipping to subhorizontal reflections in the upper crust, which resemble detachment faults. In contrast, the inside corner crust is more rugged, with basement highs rising up to 2 km above the intervening basins. This larger-scale topography is associated with a different style of faulting: the depth images reveal gently dipping (〈35°) faults that are rooted in the deep crust and that project to the ridgeward flank of the dome-shaped large basement highs (1–2 km vertical relief). The faults seem to continue as the ridge-facing flank of these highs and some may extend over the crest of the high to breakaways beyond. In this case, the domal highs that form the exhumed footwall to the faults can be described as oceanic core complexes. These controlling faults are up to 20 km long and have a heave of ∼10 km, sufficient to have accommodated up to 50 per cent extension and to have exhumed deep crustal and perhaps even mantle rocks. We suggest that similar faults can explain the structure and lithologies found at megamullion structures (oceanic core complexes) at inside corners near the present-day spreading ridge.

Description: The use of radar Doppler velocimetry for the observation of volcanic activity is new. We used this method to continuously observe the activity of one vent of Stromboli volcano, Italy, from the end of 2000 April until early May. During this period we recorded 702 eruptions, 132 of which occurred before a strong rain storm passed over the island on April 29. In order to interpret the recorded Doppler data we developed a program that simulates different strombolian eruption scenarios, for which we then calculate the theoretical Doppler spectra. Comparing our theoretical data with the observed data we are able to show that most of the eruptions are nearly vertical, although we did observe only one component of the eruption vector with our Doppler radar. One of the most interesting features of the data set is a significant change in eruptive behaviour that correlates with the occurrence of the rain storm: we find that on average the eruption duration increased by a factor of 2, eruptive velocities were much higher and indirect evidence indicates that the average particle diameter of the erupted material decreased. This change may have several causes, but the coincidence with the rain storm may be evidence of magma–water interaction and feedback on the volcanic activity. If the fluid source (rain) changing the eruptive style is at the surface and in near-surface layers then the main control on final eruption dynamics at Stromboli volcano must also be in rather shallow regions.

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.