Di-nitrogen fixation in a eutrophic tropical bay

Di-nitrogen fixation, measured in situ by the acetylene reduction technique, was shown to be associated with regular summer blooms of Oscillatoria erythraea in Mazatlán bay, a eutrophic tropical embayment on the Pacific Coast of Mexico. The Oscillatoria population density and the rate of di-nitrogen fixation per cell were of similar magnitude to those observed by other workers in the oligotrophic Caribbean Sea. Since the non-nitrogen limited fraction (Oscillatoria) of the total population was generally less than 10% and the nutrient supply to the bay is relatively abundant, di-nitrogen fixation does not appear to play an important role in the eutrophication of the bay.     

Mixed and Multi-Stock Fisheries

The September 2003 ICES Annual Science Conference was held inTalinn, Estonia, and Theme Session V was "Mixed and multi-stockfisheries – challenges and tools for assessments, prediction,and management." The theme session brought together researchersfrom the salmonid and marine fishery fields to address commonproblems faced when multiple fleets harvest a common stock,     

Effect of intertidal compared to subtidal exposure on the uptake,loss and oxidative toxicity of water-born benzo[a]pyrene in the mantle and whole tissues of the mussel,Mytilus edulis L

Blue mussels (Mytilus edulis, L.) were exposed to a single dose of 1 ppb benzo[a]pyrene (BaP) under subtidal (SC) or tidal conditions (TC; 6 h immersion, 6 h emersion) in order to follow its bioaccumulation in whole mussel and mantle tissue, and to compare BaP-mediated toxicity on lipids (malonaldehyde formation, MDA) in the mantle. Rapid uptake of BaP (70-80% of BaP initially introduced in tanks) was observed in both conditions after 12 h, but subsequent depuration in clean water was slower in TC mussels. BaP levels decreased in whole tissue in both conditions between 12 and 24 h, but increased in mantle. The mantle BaP levels were similar during the first 4 days in SC and TC, but whereas they decreased in SC after 7 days. BaP was retained at high levels in mantle in TC until the end of the study (14 days). In both conditions, significant increases (P < 0.05) in lipid peroxidation were observed after 4 days, but MDA levels were approximately 3 times higher in the mantle of TC than SC mussels, although BaP tissue concentrations were similar. These observations suggested that increased BaP-mediated toxicity in mantle lipid was due to the interactive effect of the tidal cycle of immersion/emersion on BaP-mediated oxidative damage.     

Résultats préliminaires sur la sédimentation pélagique de l'Atlantique tropical au Crétacé et au Tertiaire (plateau de Demerara,Leg ODP 207)

Five sites located on a bathymetric transect of the distal Demerara Rise were studied by ODP Leg 207. Albian sediments of essentially terrigenous nature (clay, siltstone, sandstone) are the oldest drilled stratigraphic levels and form apparently the top of the synrift sequence. They are overlain by Cenomanian to Santonian finely laminated black shales, rich in organic matter of marine origin, which accumulated on a thermally subsiding ramp. Early Campanian hiatuses are thought to be the result of final disjunction of Demerara Rise (South America) from Africa and the onset of deep water communication between the two Atlantic basins (south and central). The overlying Uppermost Cretaceous–Oligocene chalk includes rich and diversified calcareous plankton assemblages, as well as two radiolarian-rich intervals (Late Campanian and Middle Eocene). A complex erosional surface developed during the Late Oligocene–Early Miocene. Sedimentation was impeded since then on the intermediate and deep sites of Demerara Rise, possibly due to the action of deep submarine currents. To cite this article: T. Danelian et al., C. R. Geoscience 337 (2005).     

Experimental Research on Shear Behavior of Reinforced Concrete Composite Beams Under Uniformly Distributed Load

An experimental program was carried out to study the shear behavior of the reinforced con-crete composite beam(RCCB)subjected to two-phase uniformly distributed load.A total of 12 reinforcedconcrete composite beams were tested:10 of them were the RCCB subjected to two-phase uniformly dis-tributed load,the other 2 were the comparative reinforced concrete beams cast at the same time as theRCCB subjected to one-phase uniformly distributed load.The interface of precast unit and recast concretewas natural and rough.The test range of the main composite factors:the ratio of precast section depth tocomposite section depth was from 0.35 to 0.65,the ratio of first-phase load moment to precast section ulti-mate bearing moment was from 0.25 to 0.65.Based on the test results,the stresses of the longitudinal rein-forcements and stirrups,the load-bearing properties of the interface,the crack state and the failure charac-teristics of the RCCB under uniformly distributed load are discussed.The effects of the stirrups,the     

Glacial/interglacial sea surface temperature changes in the Southwest Pacific ocean over the past 360 ka

The phase relationship between climate parameters during terminations gives insight into deglaciation mechanisms. By combining foraminiferal Mg/Ca and alkenone thermometers with planktonic and benthic foraminiferal δ¹⁸O, we determined the phase relationship between local sea surface temperature (SST) and global seawater δ¹⁸O changes in the Coral Sea in the Southwestern Pacific over the last 360 ka. The onset of the SST warming preceded the seawater δ¹⁸O change by several ka for Termination I, II and III. During Termination I, the SST warming started at 20 ka BP, earlier than atmospheric CO₂ rise suggesting that the greenhouse effect was not the main trigger of this early warming. Compilation of ¹⁴C-dated SST records from the whole Pacific during Termination I reveals that the onset of the warming is generally earlier in the Southern and the tropical Pacific than in the North Pacific. This spatio-temporal warming pattern suggests linkage between the southern ocean and tropical Pacific. The early tropical warming could provide heat and moisture to the northern high latitudes, modifying radiative balance and precipitation over ice sheets at the onset of deglaciation.     

RICE PRODUCER‐PROCESSOR NETWORKS IN CÔTE D'IVOIRE*

ABSTRACT. Pressured by structural adjustment loan conditions, Côte d'Ivoire reduced state support for rice production and processing during the 1990s. In this article we examine how various actors in the rice commodity chain adapted to the macroeconomic reforms. Following a brief history of the rice sector, we present the results of fieldwork based on interviews conducted in 2002 of farmers, millers, traders, and workers in the state extension service and nongovernmental organizations. We found that, in the absence of state supports for farmers, private millers became the focal point of regional producer‐processor rice networks. The four networks identified became the sole source of domestic commercial rice when the state removed subsidies for fertilizer and modern seeds, privatized extension, and liberalized prices and imports. To increase their role in the national rice supply, the rice networks may need support through microlending and a focus on niche markets.