Facteurs hydrologiques et phytoplancton en Baie de Morlaix (Manche Occidentale)

Phytoplankton in Roscoff waters (Western English Channel) was studied in spring and summer of 1979 and 1980, parallel to seasonal changes in physical, chemical and biological variables. Strong tides prevent the formation of a seasonal thermocline and the water column remains well mixed throughout the year. Seasonal changes in temperature and salinity show a continuous increase from April to August-September. Dissolved oxygen, dissolved mineral and organic nitrogen and phosphorus vary in relation to phytoplankton production. Silicate shows a seasonal cycle, but is not completely depleted in the sea-water. A decrease of ammonia during the phytoplankton blooms in 1980 suggests that ammonia plays an important role as a nitrogen source. The NO₃/PO₄ ratio indicates that the sea-water is heavily loaded with nitrate, and shows peak values during phytoplankton blooms, due to a fall in the concentration of phosphate, which may become a limiting nutrient. However, this effect may be offset by a rapid recycling of this nutrient. Chlorophyll a and potential primary production show significant variations. The major blooms are observed in June during both years. The mean production/chl. a ratio is around 6 in both years. Phytoplankton development is marked by the succession of three major groups during the spring-summer blooms: Thalassiosira spp, Rhizosolenia spp and Chaetoceros spp. The regularity in phytoplankton species succession over a number of years suggests that the species concerned are autochtonous and well adapted to their environment.     

A comparison of energy flow through the Dublin Bay and Baie de Somme intertidal ecosystems and their network analysis

Energy (biomass) and energy flows (production, inputs, transfers and losses) were calculated for eight and twelve compartment systems (phytoplankton, benthic primary producers (macroalgae, microphytobenthos), zooplankton, benthos (meiofauna, suspensivores, deposivores and predators), fish, birds and particulate organic matter (POM) in sediment and suspended particulate matter (SPM)) both balanced and unbalanced of Dublin Bay and the Baie de Somme. The resultant models were analysed with the Scientific Committee on Oceanic Research (SCOR) network analysis package. While the two systems share many properties such as the dominant biosedimentary facies, there are fundamental differences in both structuring and responses of the systems. The network analysis suggested that the Baie de Somme was far more productive, notably in terms of water column productivity, and was the more mature system. The high organic SPM input to Dublin Bay greatly elevated the degree of detritivory such that the analysis generated metrics indicative of a mature system but which rather reflected the degree of anthropogenic stress on the system. However, the analysis of both systems displayed varying degrees of maturity. Increasing the number of compartments greatly increased the calculated throughput (T) of the system and other associated metrics such as capacity (C), ascendancy (A) and redundancy (R). In the case of Dublin Bay, a higher number of compartments increased the various measures of system maturity, but this was much less marked for the Baie de Somme. Balancing the systems also increased T, C, A and R, and, to a lesser extent but not invariably, the system maturity metrics. The ratios of the comparative system metrics such as comparative ascendancy (A/C) were much less changed by the different methodologies and as such are recommended as robust measures for intercomparison of system performance.     

Etude préliminaire des effets de la mise en eau du Réservoir de LG-2 (Territoire de la Baie James,Québec) sur le seston grossier et le zooplancton des rivières et des lacs inondés

Preliminary Study of the Effects of Impoundment of LG-2 Reservoir (James Bay Territory, Quebec) on the Net Seston and the Zooplankton of Impounded Rivers and Lakes The effects of impoundment on the biomass of net seston and zooplankton in lakes and rivers of Northern Quebec were investigated from 1978 to 1980, before, during and after the completion of LG2 Reservoir on the River La Grande (53° 54′ N, 76° 78′ W). In lotic stations, a 41–77% decrease in net seston was observed due to sedimentation of mineral particles (36–80 mg/m³ in 1978 to 10–21 mg/m³ in 1979). The ratio of organic to total seston increased from an average of 0.18 before the impoundment to 0.65 after. The flooding phase brought about a trophic upsurge; the biomass of the zooplankton increased by one to two orders of magnitude at the various sites; the greatest increases occurred in the central stations near the dam, the smallest in the upper stations near the inflow. In lake stations, no significant difference between years could be detected; the mean zooplankton biomass for all three years ranged from 6.59 mg/m³ to 34.34 mg/m³. Spatial variations between lakes were however significant. Results are compared with those in other natural lakes in Canada and reservoirs in the United States. Comparative examination of phytoplankton biomass before and after impoundment of LG2 Reservoir suggests that bacterioplankton and allochthonous organic material are key elements in the pelagic food chain after impoundment.     

Intertidal macrozoobenthos evolution of the "Baie des Veys' between 1985 and 2000

Intertidal macrozoobenthos evolution of the 'Baie des Veys' between 1985 and 2000. The distribution of intertidal macrozoobenthos in the 'Baie des Veys' (French coast of the eastern English Channel) has been studied in 2000. Results were compared with those of 1985, which are included in a long-term monitoring program established since 1973. The populations remained distributed along an estuarine-marine gradient, with a particularity on the eastern side, which is isolated from the rest of the bay by a river channel. The western and central tidal flats became more subjected by marine influence, which led to a homogenisation of the benthic communities. Oyster farming locally caused a fast decrease of the typical eastern community, which was characterized by Scoloplos armiger and Urothoe poseidonis.     

Seasonal variation in abundance and size structure of phytoplankton in Baie des Chaleurs,southwestern Gulf of St. Lawrence,in relation to physical oceanographic conditions

We investigated changes in the abundance and size structure of phytoplankton and organic seston in relation to temperature, stratification and current patterns at Gascons on the north shore of Baie des Chaleurs, eastern Canada. Phytoplankton biomass showed a general decrease during the study (May to November 1989), except for a brief diatom bloom in late October. During most of the summer, a strong temperature driven stratification was present and <5 µm cells dominated the phytoplankton community. Particles measuring <5 µm also dominated the particulate organic matter (POC and PON) throughout the year. However, only 40% of these particles could be associated with phytoplankton cells. For both particulate matter and phytoplankton, the abundance of the <5 µm size fraction was positively correlated with the Brunt-Väilsälä index of stability of the water column. Inorganic nitrogen may have limited the phytoplankton growth, as generally reported for stratified environments. Most of the biomass was probably supported by nitrogen regenerated through microbial organisms. A large bacterioplankton community was suggested by the abundance of small (<5 µm) non-phytoplanktonic particles with a low and relatively uniform C/N ratio. Larger particles were only abundant at the beginning of the study (May–June) and on one date in October. Their C/N ratios indicated they were of varied origins.     

Selectivity of mixed-function oxygenase enzyme induction in flounder (Pseudopleuronectes americanus) collected at the site of the Baie Verte, Newfoundland oil spill

A marked level of mixed-function oxygenase (MFO) enzyme induction was observed in kidney but not in liver tissues of winter flounder collected at the site of a spill of No. 2 fuel oil in Newfoundland. A number of MFO-linked, electron transport components including cytochrome P450, cytochrome P450 reductase and cytochrome b5 reductase were also slightly elevated in kidney tissues of fish at the oiled site. The results obtained in this particular field trial demonstrate that reliance on the measurement of liver MFO parameters alone could lead to false negatives in biological monitoring programs. The study also indicates that the exclusive use of liver tissues to investigate the induction potential of various chemicals should be avoided.     

Le gisement de Freiria de Rio Maior,Portugal, et sa faune de Mammiferes; Nouvelle espece de Rotundomys,consequences stratigraphiques

A new locality, close to Freiria de Rio Maior, provided a mammalian fauna associated with Charophytes, secds,Ostracods, Gastropods and Urodels. The most abundant remains correspond to a new species: Rotundomys freiriensis. This fauna has been dated as the Upper Vallesian base (MN 10), corresponding to the most recent level with small mammals found in the portuguese Miocene. Thus, the Freiria limestone succession is correlated to Cartaxo, Almoster, etc., limestones which are so developed in the Ribatejo area.     

Reflexions sur l'usage,en biologie,de la theorie de l'information

For living beings, information is as fundamental as matter or energy. In this paper we show: a) inadequacies of quantitative theories of information, b) how a qualitative analysis leads to a classification of information systems and to a modelling of intercellular communication. From a quantitative point of view, the application in biology of information theories borrowed from communication techniques proved to be disappointing. These theories ignore deliberately the significance of messages, and do not give any definition of information. They refer to quantities, based upon arbitrarily defined probabilistic events. Probability is subjective. The receiver of the message needs to have ‘meta-knowledge’ of the events. The quantity of information depends on language, coding, and arbitrary definition of disorder. The suggested objectivity is fallacious. In common language, the word ‘information’ is synonymous with knowledge of order. Following common sense a message (letters, coded signals, etc.) is information just in case it is interpretable, i.e.if it fits to a previously acquired meaning (the words of an available language, etc.). The consequence is that calculation of quantities in the sense of Shannon can be used for transmissions, but it is itself meaningless (has no significance). In linguistics and semantics, information is composed of a ‘signifier’, a physical medium (letters, coded signals, etc.), and a ‘signified’ or significance. The nature of information is complex. The laws of linguistics and semantics are valid not only at the human, organismic level, but also at the cellular and molecular level. The physiology of sensations gives us many examples for application of a concept of information An electromagnetic wave of 0,7% give us the sensation of a red colour. Sensations have no physical reality. They are purely subjective. At the cellular level communication operates by means of chemical messengers (first messengers), which generally do not penetrate the plasmic membrane. Specific captors operate as transductors: external factors are converted into secondary messengers (cyclic AMP, Ca ion, etc.). Sometimes, electric signals (like depolarization waves) may also play a part in the intercellular communication. Such processes are characterized by changes in a sequence of different molecules carried by a physical signal. What is transmitted is themeaning of the message (significance) which can be memorized by the cell, providing a possible following use. At the molecular level one can find also the processes of linguistic nature. We know that the significance of a word is changed with changing the order of letters (ADD→DAD, etc.). In the same way bases C and U are coding for serine (UCC), leucine (CUC) or proline (CCU). Here, amino-acids express the significance. In spite of the fact that this key-lock mechanism may explain many reactions, the examples prove that other elements are necessary for understanding the information. The living cell is the receiver. The message actualizes only previously learned and memorized significances or actions (trigger effect). Significance is not an emergent property of the shape of the message. It depends on the receiver and the transmitter. A word can have more than one meaning. Similarly, a messenger can order different physiological responses: muscular tension, hormonal secretion, etc.. Thus a chemical messenger is a signal which is identified and interpreted by the receiver, depending upon specific languages and previous learning. These views are in harmony with immunological and Jerne's theory (of idiotypical net). The above mentioned considerations led the author to propose thetheory of data transfer, which takes into account significance. In this theory the quantity of information is the product of the probabilistic recognition of message and the value of significance as determined by its semantic level. (See: Acta biotheoretica vol. 41 No 1/2 June 1993.) The complex nature of information asks to propose a qualitative classification with respect to thematerial support and thesignificance.

1. The material support may be linear in time (sequential reading, ADN translation)-The material support may be referred to non-temporally (drawings, logos, holograms) (Reading is instantaneous)-The material support may be in circulation, or in stock.
2. The significance may be local (tissues, organs) or general (organisms). Asignificance may be a command to be executed (imperative, conditional order) or knowledge to bememorized. The purpose of significance may be a coding for space (for morphology) or for time (ontogeny, ageing).

Conclusion: Information cannot any longer be regarded as an object. Its nature is complex, at all levels of a living being. At the molecular level to memorize an information by modification of a molecule is comparable with writing words on a diary. The key-lock process does not suppress the question of the interpretation, i.e. relations existing between the shape of a microscopic element as a molecule, and its macroscopic effect, as an antenna or a leg. There are still many unclear points in these relations, e.g. the sweet taste of molecules of tomatine and monelline. The abstract nature of significance which at the human level is concerned to mental processes, is not only a philosophical problem. In fact, there is a hypothesis based on quantum mechanics which allows to consider a physical nature of significance. In any case, the important conclusion is that significance in bio-information must be considered in relation to the message-receiver. The receiver must no longer be considered a passive one. The qualitative classification of information will allow an understanding of circulation of information in organisms and between cells.     

Etude comparative de la densite de groupes de poissons cavernicoles et epiges (characidae,cyprinidae, clariidae)

The group density of four species of cave fishes (Caecobarbus geertsi, Barbopsis devecchii, Astyanax gen. and Uegitglanis zammaranoi) and of two taxonomically related epigean species (Barbus conchonius and Hyphessobricon scholzei) was measured tridimensionally in an experimental aquarium, using a video recorder and a mirror inclined at 45° placed on top of the aquarium. The experiments were conducted in dim red light. The illumination was continuous in the case of cave fishes. For the epigean forms a 12/12 LD cycle was superimposed using dim achromatic sources. The relative positions of individuals within their own specific group were registered hourly during a week (168 h). Results show that in cave forms, the mean density of groups falls within the theoretical limits of random distribution values in all cases, whereas epigean species display a non-random aggregation tendency.     

Manifestation et Mode de Conservation de Leveillula taurica, Agent de l'Oïdium de la Tomate au Maroc

Manifestation and conservation of Leveillula taurica on tomatoes in Morocco Powdery mildew of tomato, caused by Leveillula taurica, was considered a minor disease until 1978 when serious outbreaks occurred. These outbreaks coincided with periods of a draught and the introduction of new hybrids from Europe. The pathogen infects a variety of plants, including eleven cultivated and five wild species. Infections of tomato plants were obtained by isolates collected from cultivated plants (Cynara cardunculus, Cicerarietinum, Medicago sativa, Capsicum annuum, Tropaeolum majus) and wild species (Chenopodium ambrosioides, Sonchus asper, Oxalis cemua, Urtica urens).     

Heminautilus sanctaecrucis,nouvelle espece de nautiloïde cretace

A new interpretation of the J.F. Pictet et G. Campiche's Nautilus lallierianus is here proposed. Their specimen canbe separated from Heminautilus lallierianus (d'ORB.) and Heminautilus saxbii (MORRIS). The new designation attributed is Heminautilus sanctaecrucis.