bluuebunny/crossref_metadata_2025 huggingface dataset:
Plankton of Southern Chilean fjords: trends and linkages
Authors: Antezana Tarcisio
Published: October 2008

The present paper compiles and reviews past and recent results from Magellan and Fuegian fjords for an overview of the planktonic assemblage there. It first examines linkages to local, adjacent and remote environments. The plankton assemblage presents deviations from the biota of the Magellan biogeographic Province, where the occasional presence of Antarctic species is related to oceanographic phenomena at the Polar Front. Complex bathymetric and hydrographic features within the fjords suggest that the plankton is rather isolated. Adaptations and constraints for population survival, and the role of diel migrators and gregarious zooplankters with regard to bentho-pelagic coupling are discussed. Results on seasonal differences in the plankton of the largest and most isolated basin of the Strait of Magellan are compiled. In spring the plankton was dominated by large diatoms suggesting a short food chain where most of the phytoplankton bloom goes to the bottom, to the meroplankton and to a few dominant holoplankters. In summer, the phytoplankton was dominated by pico- and nanophytoplankton suggesting a more complex food web mediated by a bacterial loop. High abundance of holo- and meroplanktonic larvae coincided with spring blooming conditions.
Life history of Perarella schneideri (Hydrozoa, Cytaedidae) in the Ligurian Sea
Authors: Bavestrello Giorgio , Puce Stefania , Cerrano Carlo , Balduzzi Andrea
Published: October 2008

Perarella schneideri is a cytaeidid hydroid living in association with the bryozoan Schizoporella longirostris. In this study we have distinguished the presence of two kinds of polyps in its colonies: large gastrozooids and very extensible filiform polyps with 4 short tentacles. A study of the relationships between the hydroid and its host indicates a parasitic behaviour of P. schneideri on bryozoan adult colonies, and predation on bryozoan larvae. Study of hydroid stomach contents indicates that the trophic strategy of P. schneideri depends on two food sources: (i) a benthic one, mainly constituted of nematodes and polychaetes and (ii) a bryozoan source, which is performed in various ways. The Perarella schneideri colonies are, in turn, a food source for halacarids which perforate the hydranth wall and, penetrating the gastrovascular cavity, suck the semi-digested prey without evident damage to the polyps.
Strobilation in a species of Bougainvillioidea (Cnidaria, Hydrozoa)
Authors: Bavestrello Giorgio , Puce Stefania , Cerrano Carlo , Senes Lorenzo
Published: October 2008

In november 1994 several specimens of an unknown hydroid were collected in a tank of the Genoa Aquarium (Italy). The polyps, characterised by filiform tentacles around a proboscis, displayed unusual asexual reproduction, leading to a linear chain of three elements (strobilation) joined by alternate oro-aboral polarity. This hydroid is very similar to another, unidentified hydroid collected in 1954 in San Francisco Bay. The hydroid of the Genoa Aquarium released free medusae characterised by four marginal tentacles, four radial canals and four oral tentacles around a tubular mouth. These features indicate that the species belongs to the superfamily Bougainvillioidea.
Life in tidepools: distribution and abundance of two crawling hydromedusae, Staurocladia oahuensis and S. bilateralis, on a rocky intertidal shore in Kominato, central Japan
Authors: Hirano Yayoi M. , Hirano Yoshuiaki J. , Yamada Mayumi
Published: October 2008

Two crawling medusae, Staurocladia oahuensis (Edmondson, 1930) and S. bilateralis (Edmondson, 1930) were found to be abundant in intertidal rock pools in Kominato from late summer until early winter. The two species were found to rarely share the same individual alga, and sometimes showed exclusive occupancy of pools at higher intertidal levels. The abundance of the two species of medusae fluctuated widely over time with both species showing similar population structures during their period of occurrence. The asexual reproduction of the medusae was considered to be a cause of the distributional pattern and the fluctuation in abundance. An experiment was conducted to evaluate the rate of asexual reproduction under different conditions. At 12°C neither species performed asexual reproduction, while at 17°C and higher temperatures both species reproduced asexually at a high rate. The number of each population was found to nearly double in about a week. The coexistence of the two species of medusae in tidepools is discussed in relation to the habitat characteristics. S. oahuensis and S. bilateralis were not known previously from Japan; this constitutes a new record of both species from Japanese waters. We also found both species in several other warm water locations in Japan.
Environmental patterns and biomass distribution of gelatinous macrozooplankton. Three study cases in the South-western Atlantic Ocean
Authors: Mianzan H. W. , Guerrero R. A.
Published: October 2008

Periodic swarms or blooms of gelatinous macrozooplankton have a negative effect on many human activities such as tourism, fisheries, and industry, but for several reasons (sampling procedures, underestimation of their real abundance, etc.), they have often been neglected in the local literature. The high spatial resolution exercise of the South-western Atlantic anchovy Engraulis anchoita Recruitment Project (SARP) was therefore also suitable for estimating standing stocks of jelly macrozooplankton, attempting to establish particular environmental patterns exerting control on the spatial distribution of these facultative carnivorous predators in coastal frontal environments. These studies were carried out through a sampling programme on board the German R/V Meteor in three different systems, convergence and divergent, in the South-western Atlantic Ocean: Region A (42°S) on the Argentine shelf, characterised by tidal mixing fronts; Region B (36°S), the freshwater outflow from Río de la Plata; and Region C (28°S), under upwelling events in subtropical waters on the Brazilian shelf. In general, a dominance of gelatinous macrozooplankton, compared with the other fraction of macrozooplankton and micronekton was observed. Mean standing stock of the gelatinous zooplankton was always greater than 50% of organic carbon (org. C) in every section analysed. The lobate ctenophore Mnemiopsis leidyi dominated the zooplankton biomass in Region A, Argentina. It represented 60% of total org. C and was more abundant at the stratified zone of the front. Ctenophores were also dominant in Region B, Río de la Plata, where the related species Mnemiopsis mccradyi and the cydippid ctenophore Pleurobrachia pileus comprised 81% of total org. C. Mnemiopsis was most common in areas of vertical thermal and saline stratification, while Pleurobrachia was dominant in the less stratified areas. Gelatinous zooplankton was also the principal component of the macrozooplankton biomass in Region C, Brazil. The hydromedusae Rhacostoma atlantica and Olindias sambaquiensis dominated both the total and gelatinous biomass (68% and 7% of total org. C), being always more abundant under lower thermal stratification. It was found that, both in convergent and divergent local systems, gelatinous plankton tended to aggregate in areas where the presence of isolines outcropping to the surface (associated with production processes) was observed. These results are discussed in the context of existing hypotheses regarding ecosystem production and food webs.
Structure of an epiphytic hydroid community on Cystoseira at two sites of different wave exposure
Authors: Faucci Anuschka , Boero Ferdinando
Published: October 2008

Epiphytism is a strategy by which opportunistic species such as hydroids, escape the intense levels of competition in marine hard bottom communities. Species of the macroalgae Cystoseira have a seasonal turnover of the frond, and we hypothesise that epiphytic hydroids colonising such an unstable substrate might show some degree of specialisation. Here the first systematic study on hydroid-Cystoseira communities is presented. In particular, the seasonal and spatial distribution of epiphytic hydroids on three species of Cystoseira at two sites of different wave exposure at Porto Cesareo (Ionian Sea/Italy) were investigated. Thirty-two hydroid species were recorded which are well known from other substrates and thus are not specific to Cystoseira; dominant species were all thecates. The influence of biological factors such as competition and the structure and abundance of the host, seem to have little influence on the hydroid community. The factors of greatest influence were mostly abiotic: sedimentation rate, nutrient levels, temperature and most especially water movement. The importance of water movement was evident in the higher colonisation of algal stems, higher hydroid frequency, larger colonies, reduced colony height, species composition, and distribution on the stems at the wave-exposed site.
A semi-closed recirculating system for the in situ study of feeding and respiration of benthic suspension feeders
Authors: Ribes Marta , Coma Rafel , Gili Josep Maria , Svoboda Armin , Julia Agustí , Parera Jordi
Published: October 2008

Suspension feeding is one of the most widespread feeding strategies among benthic organisms. However, natural feeding ecology and energetics of benthic suspension feeders are poorly known. The scarcity of field methods, apparatus and protocols that facilitate obtention of reliable in situ data has contributed to this lack of knowledge. A detailed description of an improved semi-closed recirculating system as well as the experimental set up is provided for the study of energetics in benthic suspension feeders. The system, completely submersible and surface-independent, allows us to assess oxygen concentration changes and feeding rates under natural conditions. Methodological examinations are conducted to investigate: a) the circulation of the water within the chamber; b) the time required for the flushing pump to entirely renew the volume of water of the incubation chambers; c) the behavior of the species within the chambers; d) the time of acclimation to the chamber conditions for the different species; e) the maximum decrease in oxygen concentration without affecting respiration rate; f) the time required to detect changes in concentration of the natural food sources. The system and experimental protocol is tested with species from three representative phyla, Porifera, Cnidaria and Tunicata.
Kinematic comparison of bell contraction by four species of hydromedusae
Authors: Ford M. D. , Costello J. H.
Published: October 2008

Bell form strongly affects the hydrodynamic performance of swimming hydromedusae. Although the relationship between bell shape and hydrodynamic parameters has been documented for static models of different bell shapes, the dynamic differences in contraction characteristics of different bell shapes have not been described. This is an important issue in medusan motion because the way in which medusan bells contract may influence the effect of bell shape on swimming performance. We measured differences in bell morphologies and wake velocities during swimming by two prolate (streamlined) and two oblate (disc shaped) forms of hydromedusae. Our results indicate that propulsion by prolate medusae is fundamentally different than that of oblate forms. Prolate species were characterized by contraction over the entire length of the bell and produced a narrower, higher velocity jet. Oblate medusae contracted primarily near the bell margin, and produced a broader, lower velocity jet. Prolate medusae achieved higher velocities but lower Froude propulsion efficiencies than oblate medusae. The adaptive value of these patterns are interpreted in terms of foraging and life history patterns.
Towards understanding the phylogenetic history of Hydrozoa: Hypothesis testing with 18S gene sequence data
Authors: Collins A. G.
Published: October 2008

Although systematic treatments of Hydrozoa have been notoriously difficult, a great deal of useful information on morphologies and life histories has steadily accumulated. From the assimilation of this information, numerous hypotheses of the phylogenetic relationships of the major groups of Hydrozoa have been offered. Here I evaluate these hypotheses using the complete sequence of the 18S gene for 35 hydrozoan species. New 18S sequences for 31 hydrozoans, 6 scyphozoans, one cubozoan, and one anthozoan are reported. Parsimony analyses of two datasets that include the new 18S sequences are used to assess the relative strengths and weaknesses of a list of phylogenetic hypotheses that deal with Hydrozoa. Alternative measures of tree optimality, minimum evolution and maximum likelihood, are used to evaluate the reliability of the parsimony analyses. Hydrozoa appears to be composed of two clades, herein called Trachylina and Hydroidolina. Trachylina consists of Limnomedusae, Narcomedusae, and Trachymedusae. Narcomedusae is not likely to be the basal group of Trachylina, but is instead derived directly from within Trachymedusae. This implies the secondary gain of a polyp stage. Hydroidolina consists of Capitata, Filifera, Hydridae, Leptomedusae, and Siphonophora. Anthomedusae may not form a monophyletic grouping. However, the relationships among the hydroidolinan groups are difficult to resolve with the present set of data. Finally, the monophyly of Hydrozoa is strongly supported.
Experiments on layer formation in stratified shear flow
Authors: Cisneros-Aguirre Jesús , Pelegrí J. L. , Sangrà P.
Published: October 2008

We discuss the experimental methodology and present the results of several experiments on the onset and growth of instabilities in stratified shear flow. Our results include the assessment of the effective diffusivity prior to the development of the Kelvin-Helmholtz (K-H) type instability and the measurement of the velocity field. This allows us to determine that the onset of the instability takes place when the Richardson number is close to 0.25, this value slightly decreasing with increasing initial interface thickness. The formation of a fine layered structure at the interface is suggested by density profiles taken immediately after the generation of K-H billows, but the size of the full interface as well as the layers themselves decrease in the following few seconds. We hypothesize that the time scale of the K-H billows in our laboratory experiments is so short that there is no time for added mixing to further distribute and smoothen the initial layer structure.
Field validation of a semi-spherical Lagrangian drifter
Authors: Gasser M. , Salvador J. , Sangrà P. , Pelegrí J. L.
Published: October 2008

We present the design and field validation for the performance of a Semi-spherical Lagrangian Drifter (SELD). The SELD is a low-cost, low-technology, home-made alternative to much more expensive commercial Lagrangian drifters. An analysis of the SELD configuration shows that its drag area ratio is as good as TRISTAR and holey-sock drifters. Field results in a situation of near solid rotation within an oceanic vortex confirm that SELD and holey-sock drifters have an almost identical behavior.
Mesoscale structures viewed by SAR and AVHRR near the Canary islands
Authors: Barton E. D. , Flament P. , Dodds H. , Mitchelson-Jacob E. G.
Published: October 2008

Comparison of Synthetic Aperture Radar and Advanced Very High Resolution Radiometry images of sea surface backscatter and temperature during the peak of the summer Trade winds reveals many aspects of the regional oceanography of the Canary Islands. A strong correspondence occurs between the SAR and AVHRR signals. The generally uniform wind field is perturbed as it flows past the islands producing regions of calm immediately downstream. These are bounded by lines of strong horizontal wind shear that coincide with temperature fronts between warmer lee waters and the cooler surrounding ocean. Weaker winds prevail up to 50 km downstream while enhanced wind speed on the boundaries of the lee can extend more than 150 km. Lee waves are excited in the atmospheric inversion layer where the wind passes over abrupt island topography. Quantitative estimates of wind speed made with the CMOD4 algorithm are unreliable in the downstream region because wind direction is variable and unknown and because spatial gradients in air-sea temperature difference affect atmospheric boundary layer stability. A large anticyclone south of Tenerife strongly influenced the estimated wind speed probably because higher ocean temperatures in its centre caused atmospheric instability and increased radar backscatter. The temperature fronts marking boundaries of the upwelling filament and strong eddies observed in AVHRR appear as lines of current shear in the SAR images.
Flank stability and processes off the western Canary Islands: a review from El Hierro and La Palma
Authors: Urgeles Roger , Canals Miquel , Masson D. G.
Published: October 2008

The morphological characterisation of the western submarine island flanks of El Hierro and La Palma differentiates four type-zones that may give new insights into the evolution of oceanic island slopes. The different type-zones result from the interplay between constructive volcanic processes, hemipelagic settling and volcano collapses. The latter results in massive debris avalanche deposits, which form large volcaniclastic aprons. In most cases, the headwall scarps are clearly exposed on the emerged part of the islands. The events that occurred in the youngest and westernmost islands of El Hierro and La Palma have vertical runouts exceeding 6,000 m and volumes that can reach several hundred km3. The landslide frequency for the entire Canaries is one major event per 90 ka. Triggering mechanisms are closely related to magmatic processes. The increase in the shear stress is directly linked with the forceful intrusion of magma along ridge-rift systems, while in the western Canary Islands it seems that the main process reducing shear resistance may be related to the rise in pore pressure due to hydrothermal circulation.
Short-time scale coupling between thermohaline and meteorological forcing in the Ría de Pontevedra
Authors: Pardo Paula C. , Gilcoto Miguel , Pérez Fiz F.
Published: October 2008

Two cruises were performed in May-June and October-November 1997 in the Ría de Pontevedra under strong downwelling conditions. Temperature and salinity data were recorded in short sampling periods to describe the changes in thermohaline property distribution in a short time scale. In order to obtain the residual fluxes in the Ría, a bi-dimensional non-stationary salt and thermal-energy weight averaged box-model was applied. Outputs from this kinematic model were compared with Upwelling Index, river flow and density gradient, resulting in a good multiple correlation, which proves the strong coupling between thermohaline properties and meteorological variability. Ekman forcing affects the whole area but mainly controls the dynamics of outer zones. The intensity of its effect on the circulation pattern within the Ría depends on the grade of stratification of the water bodies. River flow is more relevant in inner parts. According to estimated spatially averaged velocities, water residence time is lower than two weeks in outer parts of the Ría, and decreases toward the inner zones.
Carbon dioxide system in the Canary region during October 1995
Authors: Santana-Casiano J. Magdalena , González-Dávila M. , Laglera Baquer L. M. , Rodríguez Somoza M. J.
Published: October 2008

During the cruise F/S Poseidon 212/3 (September 30-October 8, 1995) determination of carbon system variables was carried out over the section of La Palma-La Graciosa and at the ESTOC station in the Canary Island area. Total alkalinity and pH in the total scale at 25ºC were determined at 24 stations from surface to bottom. In this area, the presence of different water masses can be traced by the carbon system variables. NACW is defined by a strong gradient of AT and pH from 150 to 750 m. MW is characterised by high values of AT and pH between 1000 to 1200 m and AAIW signals are found at around 900 m in the strait between Gran Canaria and Fuerteventura with low AT, low pH and a maximum of fCO2. Assuming an atmospheric mean value of fCO2 of 360 µatm and an average surface value of 393±7 µatm, we can conclude that during this cruise this oceanic area tends to release CO2 into the atmosphere, acting as a weak source with a carbon flux towards the atmosphere of +8.0±1.8 mmol?m-2d-1. The saturation levels in the Canary Island area have been found to be higher than 3600 m for calcite and 2700 m for aragonite. The inorganic carbon/organic carbon ratio (IC/OC) varies from 0.07 at 300 m to 0.5 at 3000 m. The IC/OC ratio shows that about a 34% increase in the CT of the deep water is contributed by the inorganic CaCO3 dissolution. The IC at 300 m is around 7 µmol kg-1, increasing with depth to 37.5 µmol kg-1 at 3700 m.
The seasonal planktonic cycle in coastal waters of the Canary Islands
Authors: Arístegui Javier , Hernández-León Santiago , Montero María F. , Gómez May
Published: October 2008

The short-term temporal variation in the phytoplankton and mesozooplankton cycles was studied in a coastal area off east Gran Canaria Island. A small phytoplankton bloom, split into two peaks, appeared during late winter (end of February and March), coinciding with the lowest temperatures in the water column. A clear inverse relationship was observed between the biomasses in mesozooplankton and phytoplankton during the bloom period. The peaks in primary production and phytoplankton biomass were uncoupled in time, suggesting that biomass could depend on consumer control (grazing), and primary production on resource control (nutrients). Mesozooplankton grazing represented less than 20% of the primary production, an indication that small zooplankton and protozoans controlled the phytoplankton populations, dominated by picoplanktonic cells (> 60% of the primary production). The ratio between depth-integrated primary production and community respiration (P/R) covaried with primary production (P), showing that changes in P control the trophic status of the system. At P > 400 mgC m-2 day-1 the P/R ratio is > 1, switching the system from heterotrophy to autotrophy, a situation that takes place during the phytoplankton growth period.
Chlorophyll increase due to internal waves in the shelf-break of Gran Canaria Island (Canary Islands)
Authors: Sangrà Pablo , Basterretxea G. , Pelegrí J. L. , Arístegui J.
Published: October 2008

This paper shows observational evidence of internal wave generation and mixing in the southwest shelf-break region of Gran Canaria Island. Signals of periodic internal motion and related mixing events were detected through large pycnocline variations and subcritical gradient Richardson events. Broad areas of homogeneous dense water over the slope, where the vertical temperature field displays a wave-like pattern, provide further evidences of internal wave mixing in this region. The observed diapycnal chlorophyll transport matches with mixing events, suggesting a periodic nutrient supply to the euphotic zone through internal wave mixing. We postulate that internal wave mixing may be an important mechanism contributing to the biological enhancement reported southwest of Gran Canaria Island.
Community assembly and the emergence of ecosystem pattern
Authors: Levin Simon A. , Dushoff Jonathan , Keymer Juan E.
Published: October 2008

A fundamental problem challenging natural scientists is to understand how macroscopic patterns, such as population abundance distributions and element ratios, emerge and are sustained in ecosystems, given that evolution typically operates most strongly at the level of individuals and their genomes. How do such patterns persist in the face of evolutionary innovation? In this paper, we explore this issue through dynamical models of community assembly and metapopulation dynamics in dynamic landscapes, and discuss individual-based approaches to the control of element cycles.
Spirals on the sea
Authors: Munk Walter
Published: October 2008

Spiral eddies were first seen in the sun glitter on the Apollo Mission 30 years ago; they have since been recorded on SAR missions and in the infrared. The spirals are globally distributed, 10-25 km in size and overwhelmingly cyclonic. They have not been explained. Under light winds favorable to visualization, linear surface features with high surfactant density and low surface roughness are of common occurrence. We have proposed that frontal formations concentrate the ambient shear and prevailing surfactants. Horizontal shear instabilities ensue when the shear becomes comparable to the coriolis frequency. The resulting vortices wind the liner features into spirals. The hypothesis needs to be tested by prolonged measurements and surface truth. Spiral eddies are a manifestation of a sub-mesoscale oceanography associated with upper ocean stirring; dimensional considerations suggest a horizontal diffusivity of order 103 m2 s-1.
Unnatural Oceans
Authors: Jackson Jeremy B.C. , Sala Enric
Published: October 2008

Ecological understanding of the oceans is based on an unnatural mix of mostly small species whose trophic relations are distorted to an unknown degree by the overfishing of megafauna including sharks, sea turtles, sea cows, seals, and whales. Living habitats like seagrass beds, kelp forests, and coral reefs that once provided critical 3-dimensional habitats for refuge and reproduction of most of the biodiversity of the oceans are also greatly reduced by fishing and other factors. Successful restoration and conservation require a more realistic understanding of the ecology of pristine marine ecosystems that can only be obtained by a combination of retrospective analyses, modeling, and intensive studies of succession in very large marine reserves.
Distribution and abundance of Eledone cirrhosa (Lamarck, 1798) and Eledone moschata (Lamarck, 1798) (Cephalopoda: Octopoda) in the Mediterranean Sea
Authors: Belcari Paola , Tserpes Georges , González María , Lefkaditou Eugenia , Marceta Bojan , Piccinetti Manfrin Gabriella , Souplet Arnauld
Published: October 2008

Information on distribution, abundance and size composition of the two octopods Eledone cirrhosa and E. moschata was obtained from the MEDITS trawl surveys, carried out in a wide area of the Mediterranean basin from 1994 to 1999. Both species showed a wide geographic distribution, as they were collected in all the major areas investigated. E. cirrhosa showed a wide depth distribution, down to the 800 m isobath, while E. moschata was mostly restricted to within 200 m. Further analysis on spatio-temporal basis with a Generalised Linear Model, evidenced that differences among major areas, depth strata and their interaction were always significant. In the case of E. cirrhosa, differences among years and year-major area interaction were also significant. Two cohorts can be singled out in the size frequency distributions of E. cirrhosa, whereas only one mode can be clearly distinguished in most of the length distributions of E. moschata.
Distribution and abundance of Octopus vulgaris Cuvier, 1797 (Cephalopoda: Octopoda) in the Mediterranean Sea
Authors: Belcari Paola , Cuccu Danila , González María , Srairi Ali , Vidoris Pavlos
Published: October 2008

Information on distribution, abundance and size composition of the common octopus Octopus vulgaris was obtained from the MEDITS trawl surveys, carried out in a wide area of the Mediterranean basin from 1994 to 1999. The species showed a wide geographic distribution, since it was collected in all the major areas investigated, but differences were highlighted among the 40 geographic sectors sampled. O. vulgaris showed a narrow depth distribution, mostly restricted to within 100 m. Catches below 200 m were scarce and occasional at deeper sea bottoms. Further analysis between major areas in the depth strata 10-50 m and 50-100 m showed the Alborán Sea and Sardinian waters as the areas where the abundance of the species was the greatest. Size frequency distributions showed a wide size range, even if large individuals were represented in a very low proportion. The surveys highlighted the relevant presence of small individuals in almost all the analysed areas. Recruits with a modal length of 5-6 cm mantle length constituted the dominant mode in the histograms of a great extent of the Italian coasts and in Morocco and Corsica waters.
Depth trajectory and performance of a trawl used for an international bottom trawl survey in the Mediterranean
Authors: Bertrand Jacques , Leonori Iole , Dremière Pierre Yves , Cosimi Giulio
Published: October 2008

An international bottom trawl survey (the MEDITS programme) has been carried out every year in the Mediterranean since 1994. During each survey, about 1000 hauls are done by a fleet of 8 to 11 vessels from 10 to 800 m depth, applying a unique standardized sampling protocol. This study analyses the trajectory and the performances of the sampling gear used for this survey, from records obtained during the surveys aboard some vessels in different geographical sub-areas and at different depth levels. Two kinds of sensors have been used, one to characterize a posteriori the vertical trajectory of the trawl from the beginning of shooting to the end of hauling (830 hauls), the other to describe in real time the stabilization of the trawl at its beginning (16 hauls) and its geometry during the tow (840 hauls). The results show the variability extent of these parameters linked with vessel, area, depth and period, illustrating their impact on the swept area estimates used for biological assessments. The results strongly suggest the inforcement of a quality strategy combining the use of rigourous sampling protocols and systematic controlling of the main parameters characterizing the trawl performance during routine surveys.
Feeding guilds of western Mediterranean demersal fish and crustaceans: an analysis based in a spring survey
Authors: Cartes Joan E. , Abelló Pere , Lloris Domènec , Carbonell Aina , Torres Pedro , Maynou Francesc , Gil de Sola Luis
Published: October 2008

The MEDITS-99 sampling was performed along all the Iberian Peninsula coasts of the western Mediterranean (from the Alborán Sea to Cape Creus) in a space-scale of 1000 Km N-S, at depths ranging between 27-790 m. Fish and decapod crustaceans were dominant in the megafaunal compartment sampled by trawling. Based on both the fish and the decapod crustacean compositions, a comparison of trophic guilds has been attempted, with fish and decapods classified as: 1) migrator macroplankton feeders (mM), 2) non-migrator macroplankton feeders (nmM), 3) nektobenthos-suprabenthos feeders (NS), 4) epibenthos feeders (Epib), 5) large detritus-scavengers (Sca), 6) infaunal feeders (Inf), 7) deposit feeders (Dep) and 8) small detritivorous feeders (Det). Multivariate techniques showed the following differences in the trophodynamics of the megafaunal assemblages along the coasts of the Iberian Peninsula: 1) crustaceans (mainly decapods) have different trophic structures on the shelf and on the slope; 2) on the slope, fish exhibited more clear changes as a function of the geographical gradient than crustaceans; and 3) trophodynamics of bathyal fish showed some geographic variations between the Alborán Sea, the Catalano-Balearic Basin, and the Algerian Basin (Vera Gulf and Alicante sectors), with a progressive north-south increase in planktophagous species.
Analysis of demersal fish assemblages of the Tuscany and Latium coasts (north-western Mediterranean)
Authors: Biagi Franco , Sartor Paolo , Ardizzone Gian Domenico , Belcari Paola , Belluscio Andrea , Serena Fabrizio
Published: October 2008

A four-year time series (1994-1997) of groundfish trawl surveys performed within the European Union Project MEDITS (Mediterranean International Trawl Surveys), was analysed to identify and describe the fish assemblages along the continental shelf and slope of Tuscany and Latium (Italy), in the north-western Mediterranean. Cluster analysis was used to group samples with similar species composition in terms of abundance, biomass and frequency of occurrence. Results allowed the identification of four to five broad assemblages along the depth gradient: a strictly coastal group (< 50 m depth), two groups in the upper and lower part of the continental shelf (essentially 50-200 m), an epibathyal group (200-450 m) and a group derived from hauls made at depths greater than 450 m. Each assemblage corresponded to a faunistic association with relatively homogeneous and persistent species composition, biomass and density indices.
The general specifications of the MEDITS surveys
Authors: Bertrand Jacques A. , Gil de Sola Luis , Papaconstantinou Costas , Relini Giulio , Souplet Arnauld
Published: October 2008

An international bottom trawl survey was designed from a European Commission´s initiative to produce biological data on the demersal resources in the Mediterranean Sea. Nine Mediterranean countries are associated in the programme, which covers all the trawlable areas along their coasts from 10 to 800 m depth. From 1994 to 2000, one survey was carried out each year, applying common standardized protocols. Seven yearly surveys have therefore been done, with a total of 7,500 stations prospected. This paper presents the methods adopted to carry out the surveys.
The state of the art in stock assessment: where we are and where we are going
Authors: Hilborn Ray
Published: October 2008

Throughout the world´s major commercial fisheries the standard paradigm includes fitting a stock assessment model to the data and then applying some form of reference point or a range of reference points, usually a target exploitation rate, to calculate a point estimate of the annual allowable catch. Over the last decade the methods available to be used in these models have changed dramatically from those using only catch, catch-at-age and survey or CPUE data to methods that now use every source of data available in a totally integrated framework. The use of meta-analysis has provided formal statistical methods for incorporating information learned from other stocks. Modern methods make it possible to express uncertainty in all model outputs, but management agencies are only now learning to deal with explicit recognition of uncertainty and have lagged far behind the scientific capability to express uncertainty. While modern stock assessment models have grown increasingly complex and their development is limited to a priesthood of experts, I believe the future trend will be to base management decisions on simple rules that are more often data-based rather than model-based, while the complex models will serve primarily to evaluate the robustness of these decision rules.
Capelin and herring as key species for the yield of north-east Arctic cod. Results from multispecies model runs
Authors: Hamre Johannes
Published: October 2008

A conceptual temperature dependent multispecies model for stock interactions and harvesting of herring, capelin and cod in the Norwegian Sea-Barents Sea region has been developed. The concept presupposes that good recruitment of herring and cod is linked to warm ocean climate, which may occur with a frequency of 8 to 10 years. Strong herring year classes overlap the distribution of capelin larvae in 3-4 years causing mass mortality of the capelin fry, and depletion of the capelin stock. At the same time the herring is about to leave the Barents Sea, and lack of food in subsequent years reduces the potential yield of cod. Immature cod is the main predator on mature capelin and cannibalism is an important factor in reducing the abundance of juvenile cod when the capelin stock is rebuilding. The model is used in a study of the effects of different fishery management strategies on stocks and yield. Results show that optimum yield of cod is obtained by high fishing mortality on immature cod from the end of a warm period until the spawning stock of capelin is rebuilt. This fishing strategy will result in large fluctuation in the yearly cod catches but yield an optimum average biomass production of capelin and an optimum potential catch of cod. These results are in accordance with the catch history of cod. Prior to the 1970s, the effort of the fishery in the Barents Sea followed to a large extent the abundance of immature cod, resulting in large catches when the stock was abundant. The yearly catches varied from 0.4 to 1.3 million tonnes, but the average catch obtained in the two periods 1950-1958 and 1959-1969 are the highest on record. Moreover, the trawlers fished with small meshes in the cod end, discarding considerable quantities of the smallest fish. It is concluded that the interaction between climate and fish stocks, and fish stock interactions in the north east Atlantic region, are of fundamental importance to the dynamic of the processes which govern the fish production of the region.
Fish stock assessments and predictions: integrating relevant knowledge. An overview
Authors: Ulltang Øyvind
Published: October 2008

A variety of existing scientific knowledge can be better utilised for improving stock assessments and predictions. In particular, failure to take account of environmental effects, including both biotic and abiotic factors in the term environment, is a serious source of error in fish stock assessments and limits the time horizon of reliable predictions. The report of the EU-funded SAP project and a set of papers resulting from communications presented at the SAP symposium in Bergen in December 2000 emphasis the potential gains by integrating relevant knowledge of processes affecting fish stocks.
A comparison of two seabird communities on opposite coasts of the Alborán Sea (western Mediterranean)
Authors: Paracuellos Mariano , Jerez Diego
Published: October 2008

We compared the seabird communities at two sites of the southern and northern shores of the Alborán Sea in the Western Mediterranean (Melilla and Adra respectively) during a whole year. Similarities and differences in environmental characteristics of the two study sites were caused by a set of geographical, physical and socio-economic human factors. Sampling was performed weekly during two-hour periods by counting seabirds crossing a given point of the coast. We found similarities in the composition and seasonality of the species between Melilla and Adra. However, there were differences between the two sites in the number of species and individuals, which were usually higher on the southern shore. In this area, seabirds depending on marine trophic resources were more abundant, whereas on the northern shore the most abundant seabird species were those whose feeding habits were not so dependent on sea resources.
Impacts of fisheries on seabird communities
Authors: Furness Robert W.
Published: October 2008

Long-line by-catch of albatrosses and petrels may soon lead to species extinctions. Set-net bycatch has caused major reductions in certain seabird populations. Some fisheries may decrease numbers of seabirds by reducing abundance of prey-fish. Other fisheries may increase seabird numbers, by increasing prey-fish abundance through depletion of predatory fish stocks, or by provision of offal and discards. These latter impacts of fisheries on seabirds are often difficult to measure against a background of many and varied environmental and human influences. Depletion of stocks of small lipid-rich fish have reduced numbers of seabirds, in Peru, the Norwegian Sea, and the Barents Sea. However, reductions of predatory fish stocks in the North Sea have more than compensated for quantities of sandeels removed by the sandeel fishery. While piscivorous fish stocks remain low, sandeel fishery and seabirds appear to be able to coexist. However, if piscivorous fish stocks recover in the North Sea, reduced availability of sandeels to seabirds may affect certain species. Provision of discards and offal can stimulate large increases in scavenging seabird numbers. Desirable reductions in discard rates may have an unfortunate side-effect of forcing some scavenging seabirds to turn to killing smaller seabirds, with drastic consequences for community structure.
Seabird mortality from longline fishing in the Mediterranean Sea and Macaronesian waters: a review and a way forward
Authors: Cooper John , Baccetti Nicola , Belda Eduardo J. , Borg John J. , Oro Daniel , Papaconstantinou Costas , Sánchez Antonio
Published: October 2008

A country-by-country review of seabird mortality from longline fishing in the Mediterranean Sea and in Macaronesian waters shows a paucity of data. Of 12 Mediterranean countries known to undertake longlining, seabird mortality is only reported for six: France, Greece, Italy, Malta, Spain and Tunisia. Seabird mortality from longlining has been reported from the Azores (Portugal) but not from the other Macaronesian Islands. Only for one country, Spain, is information on the levels of mortality available, suggesting that 4-6% of the local breeding population of Cory´s shearwater Calonectris diomedea may be killed annually, a level considered unsustainable for the long-term persistence of colonies. Cory´s shearwater is the most commonly affected species, although a number of Larus gull species are also being caught. There is insufficient knowledge to conclude whether any seabird species is at conservation risk within the region, but concern is expressed for Cory´s shearwater. It is recommended that Mediterranean and Macaronesian countries conduct assessments of their longline fisheries and seabird mortality in terms of the Food and Agriculture Organization´s International Plan of Action - Seabirds. Regional fishery organisations, such as ICCAT and GFCM, should commence the collection of seabird mortality data. A longline action plan for the affected seabird species should be produced.
The incidental capture of seabirds by Spanish drifting longline fisheries in the western Mediterranean Sea
Authors: Valeiras Julio , Camiñas Juan Antonio
Published: October 2008

The western Mediterranean Sea is an important fishing area for the Spanish drifting longline fleet, targeting swordfish (Xiphias gladius), bluefin tuna (Thunnus thynnus) and albacore (T. alalunga). Some seabird species can be captured incidentally as bycatch marine fauna. From July 1999 to August 2000 information on 554 surface longline sets was collected by onboard observers of the Spanish Oceanographic Institute (IEO) on 18 longline fishing boats working within the Spanish Mediterranean fishing area. Eleven yellow-legged gulls (Larus cachinnans), 9 Cory´s shearwaters (Calonectris diomedea) and 1 Northern gannet (Morus bassanus) were captured incidentally. Bycatch rates ranged from 0.002 to 0.023 birds/1000 hooks.
Stress protein (HSP70 family) expression in intertidal benthic organisms: the example of Anthopleura elegantissima (Cnidaria: Anthozoa)
Authors: Snyder Mark J. , Rossi Sergio
Published: October 2008

Both the physiology and distribution of intertidal organisms are strongly influenced by different kinds of physical stress. Temperature, UV radiation and desiccation in low tide conditions are usually considered the most important physical stresses. These factors impact cell metabolism, and the organism´s ability to rapidly adapt to altering environmental conditions sets its tidal distribution limits. The role of the HSP70 protein (stress protein) family in thermal stress responses has been widely demonstrated. Although it has been shown that stress protein expression is a useful tool to quantify part of this physical stress, few studies have been made with different in situ intertidal organisms. To test differences in HSP70 expression under natural conditions in the intertidal environment, we chose a common cnidarian of the eastern Pacific Ocean: the anemone Anthopleura elegantissima. Polyp HSP70 expression depends on the degree of emersion and the extent of physical stress (0.1-3.6 ± 1.5 ng HSP70 mg Protein-1 were registered between fully immersed and fully emersed polyps of the same clone). The time of immersion is reflected in the recovery of polyp HSP70 levels from the high tidal exposure (reaching again as shallower clones express more HSP70 (2.5 ng HSP70 mg P-1), than deeper ones (0.1 ng HSP70 mg P-1). Also sunny and foggy environmental situations influence the stress response. Anemone clones exposed to the sunny high intertidal zone express more than three times HSP70 (2.2 ng HSP70 mg P-1) than those on a foggy high intertidal day (0.6 ng HSP70 mg P-1). For A. elegantissima, shrinking of polyps, mucus secretion, sand covering, UV absorbing molecules, and a tight patch structure work concurrently with HSP70 expression to alleviate the effects of physical stress in low tidal emersion.
Chemical defenses in Sacoglossan Opisthobranchs: Taxonomic trends and evolutionary implications
Authors: Marín Arnaldo , Ros Joandomènec
Published: October 2008

Sacoglossan sea slugs (Mollusca: Opisthobranchia) are one of the few groups of specialist herbivores in the marine environment. Sacoglossans feed suctorially on the cell sap of macroalgae, from which they "steal" chloroplasts (kleptoplasty) and deterrent substances (kleptochemistry), retaining intracellularly both host plastids and chemicals. The ingested chloroplasts continue to photosynthesize for periods ranging from a few hours or days up to 3 months in some species. Shelled, more primitive sacoglossans feed only on the siphonalean green algal genus Caulerpa, and they do not have functional kleptoplasty. The diet of sacoglossans has radiated out from this ancestral food. Among the shell-less Plakobranchidae (=Elysiidae), the more primitive species feed on other siphonales (families Derbesiaceae, Caulerpaceae, Bryopsidaceae and Codiaceae) and fix carbon, while the more "advanced" species within the Plakobranchidae and Limapontioidae have a more broad dietary range. Most of these "advanced" species are unable to fix carbon because the chloroplasts of their food algae are mechanically disrupted during ingestion. Mesoherbivores are likely to be eaten if they live on palatable seaweeds, their cryptic coloration and form not always keeping them safe from predators. Sacoglossans prefer to live on and eat chemically defended seaweeds, and they use ingested algal chemicals as deterrents of potential predators. The most ancestral shelled sacoglossans (Oxynoidae) and some Plakobranchidae such as Elysia translucens, Thuridilla hopei and Bosellia mimetica have developed a diet-derived chemical defense mechanism. Oxynoids and Thuridilla hopei are able to biomodify the algal metabolites. However, the Plakobranchidae Elysia timida and E. viridis, together with Limapontioidea species, are characterized by their ability to de novo synthesize polypropionate metabolites. A whole analysis of kleptoplasty and chemical defenses in sacoglossans may offer a better understanding of the ecology and evolution of these specialized opisthobranchs. In this paper we summarize some of the latest findings, related mainly to Mediterranean species, and offer a plausible evolutionary scenario based on the biological and chemical trends we can distinguish in them.
Building bridges across subdisciplines in marine ecology
Authors: Pomeroy Lawrence R.
Published: October 2008

Ecology has evolved many subdisciplines whose members do not necessarily communicate regularly through attending the same meetings or reading and publishing in the same journals. As a result, explanations of ecological processes are often limited to a single factor, process, or group of organisms, and this limited approach may fail to provide the best understanding of how communities and ecosystems are assembled and function. Specifically, there is a need to bring together information on the interplay of top-down and bottom-up influences on complete communities consisting of both macroorganisms and microorganisms. A number of examples from the recent literature illustrate the problems encountered in achieving this goal. These include declining fish populations, estuarine eutrophication, the complex origin of a toxic dinoflagellate bloom, and the interactions of microorganisms and macrooorganisms in marine planktonic food webs.