ALBERT

Notes: Abstract A comparison of biological and hydrographical factors was carried out in the surface waters of the Etang de Berre near Marseille. The following parameters were compared: primary production, chlorophyll a, seston, particulate carbon and albumin as biochemical indicators; temperature, salinity, oxygen, alcalinity and nutrients (phosphate, nitrate, nitrite and silicate) as physico-chemical parameters. Furthermore, quantitative and qualitative determinations of phytoplankton and zooplankton were made. During the investigations a negative correlation was found between the content of oxygen and the concentration of dissolved phosphorus. In the northern part of the area under investigation a vertical movement toward the surface exists, which can be explained by winds from the north (Mistral). The primary production and others biological factors are ten times more intensive than in the Mediterranean Sea. This fact may be due to eutrophication. In regard to the plankton, the diatoms —especially Nitzschia delicatissima CLEVE — are dominant. A relation between the percentage composition of phytoplankton and the copepod Acartia latisetosa was found.

Notes: Abstract A study of hydrographical and biological parameters has been undertaken in surface waters near the mouth of the Rhône. Salinity, temperature and nutrient salts have been recorded, and the phytoplankton, as well as the zooplankton, quantitatively and qualitatively analyzed. Furthermore, the concentrations of chlorophyll a, seston, and organic matter have been determined. The hydrographical structure near the Rhône is heterogenous. The biological results are diffcult to explain on the basis of hydrographical parameters. The numerical data of zooplankton in the investigated area are 10 times higher than those of the Mediterranean Sea. There is a great abundance of brackish and freshwater phytoplankton in the dilution zone, but these cells are dead or almost dead; these observations coincide with the low concentrations of chlorophyll a.

Notes: Abstract A study undertaken in the surface waters of the Gulf of Fos (France), revealed very low salinities, high nutrient concentrations, and very rich phytoplanktonic populations (maximum 7.5·105 cells/l). Very often the phytoplanktonic populations attain abundances 2 to 15 times higher than maximum population densities found in the Mediterranean Sea. Such high cellular concentrations seem to suppress more or less the rates of relative photosynthesis if the concentration of chlorophyll a per 1 million cells is considered. Furthermore, the analysis of particular carbon yields high values. This phenomenon can be explained by the fact that, in addition to organic carbon, other organic forms of carbon were measured, especially some carbonates which are abundant in fresh waters. The C/N ratios found seem to support this explanation.

Notes: Abstract Numerous data on physical, chemical and biological parameters in the dilution layer of the Rhône mouth have been studied by multivariate techniques: principal-component analysis, part correlation. A new technique of cluster analysis is also proposed. By these means, a very euryhaline group of zooplankton species has been isolated and the extremely low sensibility of phytoplankton towards salinity has been shown. However, temperature seems to be the most important ecological factor. Instability and eutrophy of this area do not appear to disturb the phytoplankton cycle, which occurs with its usual succession. Chlorophyll a and organic matter do not seem of value for estimation of the biomass in the area studied.

Notes: Abstract The choice of a distance is the starting point of any multivariate analysis. The purpose of this work is to provide a clearer ecological understanding of the various similarity indices based on the “presence-absence” criterion. The so-called qualitative indices are obviously divided into two kinds depending on whether negative matches (double absences) are included or not. The concept of pre-order between distances provides a possibility of grouping the coefficients satisfying the same inequality relationships: a basic scheme of classification is proposed according to these two criteria. Theoretical considerations followed by practical applications to benthic data from the North Bay of Biscay Shelf reveal the ecological significance of the different qualitative indices. “Principal co-ordinate analysis” is used to illustrate differences between structures defined by various distances. A special section is devoted to the problem of dual “species samples” in principal co-ordinate analysis.

Notes: Abstract During the “Pros IV Cruise” of the R. V. “Korotneff” (March, 1979), continuous surface measurements of hydrobiological parameters were made across the divergence zone of the Ligurian Sea (North-Western Mediterranean). Principal component analysis (PCA) applied to data of two transects provided a graphic description with a high resolution of their spatial structure. Data from the first transect (Marth 12) confirmed the well known classification of the area into coastal, intermediate and central zones. The distribution of the data points reveals a simple and direct gradient between the coastal and intermediate zones and a great complexity of hydrological structures and chlorophyll a in the intermediate zone and its transition with the central area. Projection of the variables enabled this distribution to be interpreted as an irregular succession of small areas where vertical mixing is indicated by high salinity and nutrient concentration and patches of high chlorophyll a concentration. The second transect (March 15) included two parts: one parallel to the coastline, the other perpendicular to the coast. The PCA analyses show that similar hydrobiological structures exist along the two parts of the transect, and reveal the existence of either an isotropic patch of water with the characteristics of the intermediate zone or a meander in the front between the coastal and intermediate zones. Moreover, the analyses distinguish small phytoplankton patches (500 to 700 m wide) and group them according to their interrelationships between the variables. The resolution of PCA graphs is equivalent to several sampling steps, enabling similar interpretation of the major features from a smaller set of data and thus the simultaneous analysis of all the cruise data. Throughout the 15 d duration of the cruise the delimitation of the divergence area into 3 zones persisted. The spatial structure of the coastal and central areas was very stable, while the intermediate area displayed an important time-dependent variability in hydrobiological patterns.

Notes: Abstract A multivariate technique, based on the hypothesis of parallelism of the two first principal axes, is used to estimate differences in allometric growth at the intraspecific level. This communication is concerned with an application of the method to the comparative study of the increase in carbon and nitrogen in the isopod Sphaeroma hookeri. The method allows us to consider, during growth, several chemical components, without losing sight of the functional unity of the living organism. It permits a synthetic approach to the biochemical growth of the organism, and also a comparative physiological study on the allometric phenomena that pertain particularly to elementary chemistry. The results obtained—when interpreted in terms of biochemical growth—reveal significant metabolic differences at the intraspecific level.

Notes: Abstract Pumiceous pyroclastic products are present as flows and falls at several stages of the evolution of the southern Guadeloupe volcanic island. An understanding of this volcanism had to rely on detailed petrochemical data of these products to complement similar data for effusive rocks so as to yield complete stratigraphical coverage. On the other hand most pumiceous rocks are more or less conspicuousily banded suggesting that mixing phenomena occurred to different degrees in their genesis. Three major classes of pumiceous products are found: (1) the Axial Chain deposits (2.0–0.5 My) are characterized by An90, 75-55 + En55 + Wo42En37 + Usp35-37 ± Fo68 ± Hble, SiO2 60%, SiO2/Th 35.6, and La/Th 3.9. Banded samples have components that differ in evolution indices by about 50%; (2) the Bouillante Chaine pyroclastics (0.3–0.1 My) consist of scattered deposits with variable mineralogical and geochemical compositions that seem to have erupted from a number of small eruptive centers. Qz-dacitic pumice is common with An90, 70-45 + En66-56 + Usp32-38 + Ilm94 + Hble ± Wo40-42En40-42, SiO2 62%, SiO2/Th 22.9, and La/Th 〉4. Mixed pumice samples have highly contrasted evolution indices differing by up to 120%; (3) the Pintade pumice flows and falls correspond to the major pyroclastic event (approx. 10 km3) in the southern Basse Terre area. They are characterized by An85-70 + En66-56 + Usp32-37 ± Wo42En42, SiO2/Th 18.7-22?6, and La/Th 3.0-4.0. Banded pumice lumps are scarce and show slight compositional contrasts; differences in evolution indices do not exceed 38%. Axial and Bouillante chain pyroclastics and Grande Découverte volcano pumice respectively, form two different families in trace element plots. Minor elements in pyroxenes also are distinctive. These trends are similar to those obtained for effusive rocks and define comagmatic series. Major and trace element data for the separated components of inhomogeneous pumice in each formation always plot in the corresponding series. These chemical discriminants can be used to attribute samples of unknown provenance to a given volcanic ensemble. An inverse relationship between differences in evolution indices in inhomegeneous pumice and the volume of any single eruptive sequence is noted. This is an indication that pumiceous pyroclastic rocks were erupted from a zoned magma chamber. We favor an interpretation where zonation is produced by influx of less envolved magma in superficial differentiated chambers which is a direct cause for eruption.