Benthic community structure and sediment processes on an intertidal flat: results from the ECOFLAT project

Interactions between physical and biological processes in intertidal sediments have been the focus of studies in the framework of the ECOFLAT project. Process studies were focused on the Molenplaat, a 1.5 km² intertidal flat in the Westerschelde estuary, The Netherlands. Distinct spatial patterns in the biological community on the flat were found and related to patterns in bottom shear stress as derived from a hydrodynamic model. Based on these survey results five stations were selected with contrasting sediment composition and benthic communities.Long-term net sedimentation of mainly sand was deduced from radionuclide profiles. Sedimentation of mud on the surface of part of the intertidal flat was shown to be a seasonally cyclic process, with a magnitude sufficient to significantly affect the mud balance of the estuary. Measurements of erodability as a function of tidal current showed a biological control on this variable. Benthic microalgae stabilise the sediment surface, whereas the benthic macrofauna has a destabilising effect.Food web studies show that the contrasting biological communities (microbenthos, meiobenthos, macrobenthos) at muddy and sandy sites have substantial differences in the quantitative aspects of their food web. Turnover of microalgae is much lower at muddy than at sandy sites, and this is mostly related to a lower grazing pressure. It is hypothesised that high mud content decreases the availability of benthic microalgae to grazers.We demonstrate a positive feedback between benthic microalgae and mud sedimentation which may lead to the existence of different stable states. This may explain the existence of relatively sharp boundaries and strong community contrasts in the presence of weak and smooth environmental gradients.     

Geomagnetic field intensity between 70 000 and 130 000 years B.P. from a volcanic sequence on La Réunion, Indian Ocean

A detailed paleointensity study was made of a sequence of 70 successive lava flows of the Piton des Neiges volcano on the island of La Réunion (Indian Ocean). Radiometric dating brackets the age of this sequence between 130 ± 3 ka and 72 ± 3 ka. Rock magnetic investigations show that titanomagnetites in the pseudo single domain range are the main magnetic carrier of the Natural Remanent Magnetisation (NRM). Over 350 samples were used for paleointensity determinations carried out with the Thellier method in vacuum or in an argon atmosphere. Of these, 89 samples yielded reliable results, with within-flow scatter often lower than 20%. These results indicate that the geomagnetic field intensity has varied at La Réunion between 13 and 65 μT during the period of time explored. The average value, 42 μT, is higher than the present field at La Réunion (35 μT). The results from the upper part of the section are consistent with previous results obtained for the 82–98 ka period also at La Réunion [1] and document a broad low around 95 ka. not associated with large directional changes. On a larger geographic scale, the paleointensity values from La Réunion are significantly higher than those obtained from Mount Etna [2]. Precise comparison is, however, difficult because of the lack of detail in the Etna results. In the lower part of the section, a marked intensity low, coinciding with significant deviation from the dipole field direction is observed at 115 ka and could correspond to the end of the Blake event.     

The Influence of Redox Reactions on the Uptake of Dissolved Ce by Suspended Fe and Mn Oxide Particles

Laboratory experiments were conducted to evaluate the partitioning ofrare earth elements (REE) between solution and suspended particles. Becauseof their strong tendency to complex, the REE can be used to study a varietyof marine processes and in particular particle scavenging. In this study, anemphasis was placed on examining abiotic redox processes that influence theuptake of dissolved Ce by particles. Batch sorption experiments wereconducted with REE and synthetic mineral phases over the range of pH4–9. The solutions varied in ionic strength between 0 and 0.7 M andconsisted of individual solutes (NaNO₃, NaCl, andNa₂SO₄), ionic mixtures that duplicate theseawater composition, and natural seawater. The uptake of REE from solutionwas also studied at a Pt electrode coated with using cyclic voltametry. Experimental results are consistent with uptake of dissolved Ce onto occurring by a combination of oxidativescavenging and surface complexation. The contribution of oxidativescavenging to the removal of Ce from solution is most pronounced at acidicpH, where the strictly trivalent REE exhibit little propensity for sorptiononto . Sorption of dissolved Ce onto FeOOH occursin a manner analogous to that of the other strictly trivalent REE and nocontribution from oxidative scavenging is observed on this mineral phase atlow pH. Our work also substantiates the hypothesis that anions in solution,particularly and Cl^-, aswell as those adsorbed on the surface of the particles, influence the extentof Ce uptake by . This revised version was published online in July 2006 with corrections to the Cover Date.     

Variability in the Hydrographic and Biological Features of the Gulf of Naples

Abstract. Recent observations of physico-chemical and biological parameters in the Gulf of Naples are summarized. The water masses present within the Gulf during the various periods of the year are described. The temporal and spatial distribution of surface nutrients (N-NO₃, P-PO₄, Si-SiO₄) and chlorophyll a are reported and the areas exposed to local eutrophication are identified. Biweekly sampling at a reference station has permitted us also to identify both phytoplankton and zooplankton seasonal cycles. The morphology of the basin and the uneven land runoff distribution are interpreted as causal to the variability of chemico-physical parameters and of the associated biological communities, giving rise to two subsystems (coastal and "open water") within the Gulf.     

Body size–abundance distributions of nano- and micro-phytoplankton guilds in coastal marine ecosystems

This study focuses on body size–abundance distributions of nano- and micro-phytoplankton guilds in coastal marine areas of the Southern Adriatic–Ionian region. The aim of the study was to evaluate the occurrence of common patterns of body size–abundance distributions in relation to physical, chemical and biological environmental forcing factors and to taxonomic composition of phytoplankton guilds. This paper is based on data collected during four oceanographic cruises carried out seasonally along the Southern Apulian coast (Adriatic and Ionian Seas, SE Italy) as a part of the INTERREG II Italy–Greece Program. The study was performed at 21 stations located on 7 transects perpendicular to the coastline, with 3 stations per transect at a distance of 3, 9 and 15 NM from the coastline. At each station, profiles of the major physical features of the water were determined and water samples were collected for phytoplankton and nutrient analysis. Overall, 320 nano- and micro-phytoplankton taxa were identified, 76% of which at species level, with phytoplankton cells ranging in size from 0.008 to 4697.54 ng. Body size–abundance distributions showed some common features: they were relatively invariant (average similarity 65%) with respect to taxonomic composition (average similarity 32%), right skewed (90%), leptokurtic (77%) and log normal (76%). Moreover, abiotic, biotic and spatial ecosystem components accounted for up to 75% of body size–abundance distribution variation. The results of this study suggest that body size–abundance distributions are an intrinsic property of marine phytoplankton communities, emphasising functional dependence on ecological constraints related to trophic factors and intra-guild coexistence relationships.     

The Cengio submarine turbidite system of the Tertiary Piedmont Basin,Northwestern Italy

The Cengio sandstone member of the Tertiary Piedmont Basin in northwestern Italy has a conservatively estimated volume of 2.5 to 3 km³ (length: 6.4 km; width: 4.8 km; thickness: 170 m). It is interpreted as a sandstone-rich submarine fan deposit. The Cengio member consists of eight tabular depositional sandstone lobes that are 5- to 25-m thick. These lobes filled a submarine structural depression and onlap and/or pinch-out against bounding slope mudstones. The stacking of the lobe units was related to synsedimentary tectonism.     

Strumento fotoelettrico per il calcolo del coefficiente di correlazione e per altri computi

Riassunto Si illustra un apparecchio fotoelettrico che, essendo atto al calcolo degli integrali doppi e degli integrali di numerose funzioni di funzione, si presta per determinare il coefficiente di correlazione.

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Summary A photoelectric device is illustrated which, being fit for computation of double integrals, and for squaring a great number of functions of function, is suitable to determine the correlation coefficient.

     

Sull'idrologia del Foehn

Riassunto Per alcuni casi diFöhn delle Alpi Italiane, interessanti il Piemonte e la Lombardia, sono state esaminate le variazioni dei deflussi nei giorni in cui soffiava tale vento nonchè in quelli adiacenti, trovando che di regola, quando non intervengono precipitazioni od altri fattori, ilFöhn provoca una diminuzione netta delle portate, che può raggiungere e superare il 10% e che si esplica con relativa prontezza. Si spiega tale riduzione con la forte evaporazione causata dalFöhn.

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Summary Researches have been undertaken on the influence of the Föhn in the italian Alps, regarding the runoff-variations. The Föhn causes as a rule a decrease of the runoff, which, in absence of precipitation, can reach or exceed 10%. It can be explained by the strong evaporation during the Föhn.

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Zusammenfassung Anhand einiger Föhnfälle in den italienischen Alpen wurde der Einfluss des Föhns auf die Aenderungen der Abflussmenge untersucht. Wenn empfindliche Niederschläge oder andere Faktoren nicht vorkommen, verursacht in der Regel der Föhn eine Abnahme der Abflussmenge, die 10% erreichen oder sogar überschreiten kann. Die Erklärung ist in der starken Verdunstung während des Föhns zu suchen.

     

Le barovariographe comme appareil de sondage aérologique

Summary First, the theory of the barovariograph, the deductions from which have also been confirmed by experiments, is presented with some improvements. Then there follows a concise illustration of the various possibilities of applying the instrument for the disclosure of aerological phenomena existing over a given locality.

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Zusammenfassung Zunächst wird, mit einigen Erweiterungen, die Theorie des Barovariographen dargelegt, deren Ableitungen auch experimentell bestätigt wurden. Dann folgt eine kurze Erläuterung der verschiedenen Anwendungsmöglichkeiten des Instrumentes für die Registrierung gewisser aerologischer Erscheinungen über einem Ort.

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Riasunto Dapprima viene esposta con alcuni perfezionamenti la teoria del barovariografo, le cui deduzioni sono state confermate anche sperimentalmente. Segue una illustrazione succinta delle varie possibilità applicative dello strumento per la rilevazione dei fenomeni aerologici sovrastanti una località determinata.

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Communication présentée à l'Association Internationale de Météorologie, IXe Assemblée Générale de l'UGGI, Bruxelles, Séance du 24 Août 1951.     

Nuovo metodo di registrazione dello stato del mare e primi risultati ottenuti a Genova

Riassunto Viene descritto ed illustrato un nuovo procedimento di registrazione del moto ondoso marino, il quale consiste sostanzialmente nel trasformare l'escursione verticale che subisce la superficie del mare nella compressione o dilatazione di una massa d'aria sovrastante racchiusa in un tubo verticale munito superiormente di opportuna membrana sensibile. Un tale apparecchio, installato a Prà (Genova) dal-l'Istituto Geofisico dell'Università di Genova, funziona con successo da alcuni mesi. Segue un esame dei primi risultati ivi conseguiti, dal quale appare l'importanza del passaggio dei fronti freddi sul moto ondoso del mare.

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Summary A new method for the recording of sea-wave motion is described and explained. It consists in having the vertical movement of the sea surface transformed into compression or expansion of a volume of air enclosed in a tube which is carrying on its upper part a sensitive membrane. This self-recording instrument, set up at Prà (Genoa) by the Istituto Geofisico dell'Università di Genova is functioning since several months already without giving rise to objections. Some first results obtained up now are also examided, from which it appears the importance of the passage of cold fronts.

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Zusammenfassung Es wird ein neues Verfahren für die Registrierung der Meereswellenbewegung beschrieben und erläutert. Es besteht darin, dass der vertikale Gang der Meeresoberfläche umgewandelt wird in Kompression oder Expansion einer in einem Rohre befindlichen Luftmasse, welche am oberen Teil von einer empfindlichen Membran geschlossen ist. Dieser Gerät, vom Istituto Geofisico dell'Università di Genova in Prà (Genua) aufgestellt, arbeitet bereits seit einigen Monaten einwandfrei. Einige vorläufige Ergebnisse werden dann erläutert, wofür auf die Bedeutung des Durchganges von Kaltfronten hingewiesen wird.