Introduction. Brazil is one of the most important producers of passion fruits. Inoculation witharbuscular mycorrhizal fungi (AMF) may reduce or eliminate the need for phosphate fertilization on this crop. Weinvestigated the response of passion fruit seedlings to inoculation with AMF and phosphorus (P) supply. Materialsand methods. A greenhouse experiment was carried out in a factorial design. The seedlings were inoculated with100 spores per plant of single or mixed AMF inoculum on sterilized or non-sterilized soil which was amended with (11 or 30) mgP × dm-3 soil applied as superphosphate or used unfertilized (4 mgP × dm-3 soil). Relative mycorrhizal dependency (RMD) of passion fruit was estimated for eachtreatment of inoculation, soil sterilization, and P level, by expressing the difference between the dry mass ofmycorrhizal plants and non-mycorrhizal plants as a percentage of the dry mass of mycorrhizal plants. Results.Inoculation was effective only on plants grown in sterilized soil with (4 or 11) mgP × dm-3 soil. Plants were "facultatively mycotrophic" when associated with AMF and when receiving a supply of 30 mgP × dm-3 soil. Seedlings in unfertilized soil with 4 mgP × dm-3 soil wereexcessively dependent on the mycorrhizal association. In soil with 11 mgP × dm-3 soil, seedlingswere marginally to moderately dependent, depending upon the AMF species used. All inoculated seedlings, withoutconsidering soil sterilization, were marginally dependent in soil with 30 mgP × dm-3 soil. Insterilized soil, independently of P, they were moderately dependent. However, in the same soil, with 30 mgP × dm-3 soil, the seedlings were marginally dependent. Discussion - conclusion. The relativemycorrhizal dependency (RMD) of the passion fruit cultivar used was influenced by the species of the inoculated AMF,soil sterilization and soil P level. Passion fruit obtained significant benefit from inoculation with AMF; thus, thesefungi can be used to improve plant growth even without P fertilization.

Empirical models were established, which link the biomasses or productions of the successive planktonic trophic levels in lakes of different depth and trophic status. Published data on 56 lakes were analysed, using both least-square and reduced-major-axis regressions. Reduced-major-axes regression technique was used in order to take into account variability due to both bottom-up and top-down forces. In shallow lakes, the energy transfer efficiency between phytoplankton and zooplankton decreases with increasing trophy. An inverse tendency appears in deep lakes. However, when considering only the oligo- and mesotrophic temperate lakes, the mean primary and secondary productivities per unit of area are about the same in shallow and in deep sites. On the other hand, shallow water bodies are characterized by a smaller mean size of the crustacean species, a lower mean biomass of zooplankton and a higher P zoo/B zoo ratio than deep lakes, probably as a response to the predation by fish. While the consumers seem to have a strong influence on the size structure and biomass of plankton, the energy flows between the trophic levels could be largely controlled by bottom-up forces.

Pendant l'été 1995 (juin - septembre), après la vidange du réservoir de Puyvalador (1421 m) sur la rivière Aude (Pyrénées orientales), la colonisation végétale des sédiments provisoirement exondés a été étudiée et cartographiée. Un faible nombre d'espèces végétales participait à cette végétalisation, dont certaines avec un fort recouvrement. Une attention particulière a été portée à la biomasse et à la composition chimique des peuplements végétaux dominants, en particulier Rorippa islandica. Les mécanismes de cette colonisation et la mobilisation des principaux éléments du cycle biogéochimique font l'objet d'une discussion. Un problème reste en suspens : l'impact sur la masse d'eau de ces éléments chimiques lors de la décomposition du matériel végétal une fois immergé.

Pacifastacus leniusculus has established hundreds of breeding populations in Britain since its introduction in 1976. One such population was established in the River Great Ouse, a major lowland river in mid-to eastern England, from 140 crayfish introduced in 1984. Estimates of growth, density and biomass of the population in 1992 are presented. Under laboratory conditions, the per moult increment (MI) and percentage per moult increment (PCMI) of crayfish were binomially correlated to their carapace length (CL), that is, the MI increased with CL and then decreased as crayfish grew old, and the PCMI decreased with increase in CL. Based on length frequency distribution data collected from the river in October and November and estimated by Bhattacharya's method, seven male cohorts while only four young female cohorts were identified because of insufficient data for old cohorts. The mean CL of each crayfish cohort was 16.6, 31.2, 41.6, 52.0, 57.8, 64.2, and 69.2 mm for 0+ to 6+ year old males respectively, and 15.4, 28.5, 39.7, and 49.8 mm for 0+ to 3+ females. There were no significant differences between growth rates of either CL or WW of males and females at age for 0+ to 3+ (no data of females > 3+ were available for comparison).

In a riffle, the densities and biomass of crayfish were significantly different between four domains with different bottom substrats and highest in the habitat with the highest density of cobbles and thus, greatest density of potential shelters. The mean densities and biomass of crayfish of all sizes in this riffle were between 10.m2 and 61 g.m−2 respectively in July and 15.m−2 and 53 g.m−2 in November. In a pool, mean density and biomass of crayfish > 30 mm CL, estimated by Fish-Ford multiple capture-mark-recapture methods, were 0.8 m−2 and 37 g.m−2 between May and August.

Several mounds in western Kenya were excavated to examine their internal structure. The mounds and the soil beneath them were found to be densely packed with discrete chambers containing fungus combs. A simple system of passages opening to the exterior provided both access and ventilation to the interior of the nest. One nest was killed by fumigation and its contents extracted. The nest population was estimated to be 0.28 million adult steriles with a biomass of 462 g dry weight, and the total dry weight of fungus comb was 2.8 kg. These estimates are very low in comparison to nests of Macrotermes spp. that build mounds of comparable size. The ratio of fungus comb weight to adult biomass (6:1) is higher than that in Macrotermes spp., perhaps because the comb is constructed in a different way.

The present results come from the campaigns of the international multidisciplinary programmeconducted by P. La Violette (Naval Oceans Research and Development Activities, NORDA), the WesternMediterranean Circulation Experiment. The mesoscale instabilities of the Mediterranean circulation induce meanders, gyres and eddies acting on the production potential of living resources. These resources are evidenced here through the cetaceans and other large organisms directly observable in the surface waters of the sea, along the track of the cruise NORDA 706 (May-June 1986), and through the underlying biomasses detected by an echo sounder, 12 kHz fishfinder. Acoustics detection was continuous, set at the same level by day and night for 15 days intenupted only when the ship stopped for hydrological measurements at 87 CTD sampling stations. The pattern of hydrological sampling was designed in order to identify the intermediate water veins in the Algerian Basin. The three sets of field data - daily visual census, continuous echo-sounding and hydrological profiles - were compared and processed in statistical factorial and multiregression analyses. These show that presence of cetaceans coincides with highly concentrated echos; other large organisms observed are distributed at random, without any link with the concentrated echos. It results that cetaceans have the ability to detect acoustically the same biomasses as humans do with a 12 kHz echo-sounder; this is an argument for the "echolocation of the Odontoceta" and "vocalization of the Mysticeta"; up to now, such processes are not accepted by all cetologists. Four examples of echogram are reported here associated with fin whales, sperm whales, pilot whales and dolphins. Dynamical analysis of the Mediterranean circulation before and during the cruise by contemporaneous remote sensing imagery (CZCS and NOAA 9) enables deduction of the dynamic characteristics of the areas where high densities of acoustical detection co-occur with the presence of cetaceans. Such areas are enriched by the intermediate water by a shearing effect against the edge or the bottom of an eddy, i.e. at the contact between two water bodies moving in opposite directions; it can also happen on the edges of two eddies where they become tangential. Thus, four areas of high productivity of living resources (high trophic-chain levels) are evidenced here in the Algerian Basin. One is linked with the frontal process of the Almeria-Oran Front; the three others, not previously described, concern the influx of levantine intermediate water intothe Western Mediterranean Basin.

Freshwater fishing is highly developed in the Amazonian basin, and the problems of managing the fish resource are becoming increasingly acute. The global model of exploited stock dynamics has proved inadequate for explaining the variations observed in catches from one year to the next. Following the results of recent studies in maritime fishing, this work aims to identify the contribution of environmental variables (hydrological parameters have been selected) to the explanation of variations in the abundance of the exploited fish community. An abundance index is calculated based on the catch per unit of effort statistics and the surface of the considered basin. Using a 12-year time series, the results show that the effect of the fishing effort on the index of abundance is negligible when viewed alongside the flood regime parameters for the years prior to the catch. The effects revealed are, in chronological order of appearance: 1) a positive effect of the water level during the flood regime peak three years previous to the catch, probably associated with recruitment for a number of species; 2) the effect of the water level during its rise two years before the catch, which may well be related to competition phenomena; and 3) the effect of severe low-water levels two years before the catch, possibly due to mass natural mortality during the severest periods of low-water. Because there are complex migratory movements of fish populations either side of low-water periods, only the estimated biomass during the flood appears to be an accurate reflection of the mean biomass in the environment. Linear models are presented, where the abundance index is a function of the hydrological parameters previously identified. The model with 3 variables corresponding to the 3 evidenced effects, explains more than 83% of the variations in the annual abundance indices.

Different random samplings were used to assess the biomass of intertidal bivalves on two main biotopes of the south west coast of New Caledonia. Over the 46.5 km line of sandy beach, the total bivalve biomass is 4.3 ± 1.8 t and the mean biomass of Atactodea striata is about 3.2 ± 1.2 t. Over the 9.85 km2 sandy-muddy shore of the study area, bivalve stocks (1.050 ± 392 t) are dominated by Gafrarium tumidum and Anadara scapha; their mean biomasses are respectively 270 ± 132 t and 418 ± 308 t. This resource is expected to meet the demand of the domestic market through an artisanal fishery.

Zooplankton samples were collected over a 21-month period in five floodplain lakes of the Orinoco River in orderto establish zooplankton species composition, abundance patterns, and biomass and their relationships with the patterns of inundations and lake morphometry. 60 rotifer taxa were identified. This group was generally more abundant thancopepods and cladocerans (mean : 73,4 % of total zooplankton). Common and abundant rotifer species included K. americana, K. cochlearis, B. mirus, B. gessneri, P. vulgaris and F. longiseta. Copepods were dominated by nauplii (mean : 73,8 % of total copepod stages). Cladocerans were scarce and dominated by M. minuta, C. cornuta and D. spinulosum.Most frequent and abundant zooplankton species were euplanktonic with a dominance of filter feeders and microphagous detritivores. Mean zooplankton density in all lakes ranged from 340 ind./l to 3 486 ind./l. Biomass ranged from 71,1 µg.l (dw) to 432,8 µg/l. Rotifers accounted for 64,7 % of the total mean zooplankton biomass in three lakes whilecopepods accounted for 57,8 % of the biomass in two lakes. Both density and biomass were markedly seasonal withhighest mean values at low waters. Mean density in the lakes was 100 times higher than in the Orinoco main stem. Lakeswith highest variabilities in surface area and water depths showed highest zooplankton densities. The type of connection (direct or indirect) established between the lakes and the major source of the water also seemed important to interpret the productivity of floodplain lakes.

The compositon, abundance and biomass of the benthic fish fauna were studied along a 6 km stretch of the GuariticoRiver. This water course is located in the western plains of Venezuela and belongs to the Apure River floodplain system.Monthly collections from June, 1990 to January, 1991 were made by means of a small trawling apparatus rigged todugout canoes according to the design of López-Rojas et al. (1984). 42 fish species were identified with a dominanceof species from the orders Siluriformes and Gymnotiformes. The fish assemblage differed markedly from other Venezuelan river systems. Seasonally, higher diversity and evenness were observed at the high water phase while the abundance, relative biomass and CPUE were higher at low water.

L'étude de la dynamique saisonnière du phytoplancton dans le lac de Pareloup a été réalisée dans le cadre plus général de la mise en œuvre d'un modèle de fonctionnement de ce réservoir en vue de sa gestion. La biomasse (poids frais µg.l-1 et chlorophylle a) et la densité cellulaire ont été suivies de mars à novembre pendant deux années. Le maximum annuel de phytoplancton (biomasse et densité cellulaire) se situe au printemps ; il est dominé par les diatomées dont le déclin est initié par la carence en silice du milieu et, sans doute, par des concentrations cellulaires en chlorophylle a minimales. Une phase claire résulte de la sédimentation des diatomées et se prolonge pendant tout l'été. Cette période estivale se caractérise par une forte production primaire et une faible biomasse, biomasse régulée par la prédation. Avec le brassage automnal, de petites espèces connaissent une croissance rapide qui s'exprime seulement en densité cellulaire; la faible augmentation des valeurs de biomasse par rapport à celles de l'été est due essentiellement à la présence de Gonyostomum semen et au léger renouveau des diatomées. Les différentes phases du développement du phytoplancton sont analysées et confrontées au modèle P.E.G. proposé par Sommer et al. (1986). La mise en place de la stratification thermique est l'élément fondamental dans le fonctionnement du réservoir de Pareloup ; chaque année, elle détermine le départ d'une succession phytoplanctonique de type cyclique.

Species composition, distribution and biomass of benthic macrophyte communities have been studied in a high mountain, oligotrophic, softwater lake from the Central Pyrenees. Isoetids (Isoetes lacustris L., Isoetes setacea Lam., Subularia aquatica L. and Eleocharis acicularis (L.) Roemer & Schultes) are the dominant macrophytes in areas over 2-3 meters in depth. Natopotamids (Sparganium angustifolium Michx.) are restricted to shallow waters. Algae (Nitella gracilis (Smith) Agardh) only predominate in deep waters. Three main communities have been distinguished : the Sparganium angustifolium community (160 g dwt m-2), the Isoetes lacustris community (120-460 g dwt m-2) and the Nitella gracilis community (11 g dwt m-2). Biomass differences between shallow and deep water Isoetes populations have been attributed to ice-scour stress. Neither irradiance nor slope can explain the lower boundaries observed in the distribution of vascular plants ; sediment features may be responsible for them. Mean lake macrophyte biomass amounts to 140 g dwt m-2 (20 g C -2), a very high value if compared with boreal lakes with similar limnological characteristics.

La dynamique des populations et la production du zooplancton ont été évaluées dans 3 retenues voisines (les lacs d'Aumar, Orédon et Aubert) et comparées aux résultats obtenus antérieurement dans le lac naturel de Port-Bielh (2 285 m) dont le zooplancton offrait une composition spécifique analogue (espèces dominantes : Polyarthra vulgaris, Mixodiaptomus laciniatus, Cyclops strenuus, Daphnia longispina).Les 3 retenues diffèrent essentiellement par le régime thermique lié à leurs caractéristiques morphométriques et hydrologiques. L'ensemble de ces caractéristiques a permis de définir une série lacustre Port-Bielh-Aumar-Orédon-Aubert, caractérisée par un abaissement progressif du climat thermique et une instabilité croissante de l'environnement.L'étude comparée du peuplement zooplanctonique en milieu naturel et en milieu perturbé, permet de préciser l'influence des modalités d'exploitation de ces retenues sur le développement de la communauté pélagique. En particulier, elle met en évidence pour la série lacustre considérée, un changement de structure de la communauté zooplanctonique, un appauvrissement spécifique de cette communauté, et une diminution progressive de la productivité de ces milieux.