Investigations in the euphotic zone of the tropical North Atlantic: Programme and hydrography during the nectar cruises

In 1977 a multidisciplinary study of the euphotic zone of permanently stratified waters was started by the Netherlands Institute for Sea Research. The programme, North Equatorial Current Trans Atlantic Research (NECTAR), involves investigations of the carbon budget in the upper 300 m of the oligotrophic Atlantic Ocean. The sampling programme at 6 driftstations of 24 to 48 hours along 20° N in the autumns of 1977 and 1978 is described. Particular attention was paid to the measurement of primary production with the ¹⁴C method as compared with diurnal variations in biologically affected parameters. Another main scientific objective was the significance of vertical profiles of irradiance, O₂, POC, DOC, CO₂, nutrients, ETS, ATP, bacterioplankton, chlorophyll and zooplankton.The hydrographic data of the NECTAR cruises are presented and compared with the general hydrography of the area described in recent literature. Discrepancies from the latter comprise a more southerly extension of North Atlantic Water in the upper 100 m and a pronounced influence of South Atlantic Central Water in subsurface waters down to 500 m between 23° W and 32° W.     

Oxygen regime,respiratory activity and biomass of microorganisms,and the carbon budget in the Fladen Ground area (Northern North Sea) during spring

A watermass, on the Fladen Grounds, marked with a drifting buoy, was studied daily during one month in spring. Hydrographic parameters, nutrient regime, oxygen regime, biomass of microorganisms and respiratory activity were determined; the high variability of the observations is discussed. From these observations, and earlier publications on the same cruise, a carbon budget is calculated. From oxygen flux calculations it appeared that the net ecosystem production must be more than 2.5 g C m⁻².d⁻¹ which could not be verified by C-14 primary production measurements. Presumably high variability in the system in time and space makes it impossible to get a fitting budget.     

Chemical and physiological changes of phytoplankton during the spring bloom,dominated by phaeocystis pouchetii (Haptophyceae): observations in Dutch coastal waters of the North Sea

During the spring bloom of phytoplankton in Dutch coastal waters of the North Sea the flux of ¹⁴C-labelled products into pools of protein, polysaccharides, small metabolic intermediates and lipids was studied. The molecular size distribution of extracellular products, amounting to 28% of the particulate production, was determined by gel filtration. Concentrations of protein and carbohydrates were determined in the same phytoplankton samples. At an early stage of the bloom protein synthesis and protein concentration dominated over carbohydrate synthesis and carbohydrate concentration, but after the peak of the bloom carbohydrates were the predominant photosynthetic endproduct. These observations have been compared to similar observations on unialgal cultures of Phaeocystis pouchetii. The influence of phosphate depletion on the extracellular release of organic compounds and the impact of the colonial growth form of Phaeocystis pouchetii on the distribution of intra- and extracellular labelled compounds are also discussed.     

Free-living plathelminthes in sheep-grazed and ungrazed supralittoral salt marshes of the North Sea: Abundance,biomass, and their significance in food chains

The supralittoral salt marshes of the North Sea are marked by high halophyte primary productivity. The environmental factors are strongly fluctuating. Despite these features the metazoan meiofaunal abundance is equal to that found in other littoral habitats. On average 1250 marine metazoans are found per 10 cm² in ungrazed and 770 per 10 cm² in sheep-grazed supralittoral salt marshes. Nematoda dominate in numerical abundance, Oligochaeta in biomass. Plathelminthes account for 15% of marine metazoans in ungrazed and 5% in grazed salt marshes.Total plathelminth abundance increases with halophyte density, whereas the abundance of diatom-feeding Plathelminthes decreases. In ungrazed marshes on average 104 Plathelminthes are found per 10 cm², accounting for a biomass of 0.65 g DW·m⁻². In sheep-grazed marshes the average abundance is only 32 individuals per 10 cm², accounting for a biomass of 0.1 g DW·m⁻². Average individual weight is 3.2 μg DW or 2.5 μg AFDW.In grazed salt marshes, 30% of plathelminthes feed on diatoms, 66% are predators, and 4% feed on bacteria (gut analysis). In ungrazed salt marshes only 3% are diatom-feeders, and 90% are predators feeding on Nematoda, Copepoda, Oligochaeta, and smaller Plathelminthes. Presumably plathelminthes are top predators on the salt marsh meiofauna.     

Research into the Preservation and Renewal Patterns of Ancient Towns:A Case Study of Heping, Fujian, P. R. China

对超高压技术的起源、发展、特点进行概述。超高压技术在食品工业中用于杀毒灭菌,贮藏与保鲜。并在果蔬制品、肉制品、乳制品、蛋类食品、速冻产品等加工中得到广泛的应用。同时提出目前我国超高压技术存在的问题及对策,且对发展前景进行展望。     

Contribution of cultivar,fertilizer and weather to yield variation of winter wheat over three decades: A case study in the North China Plain

Long-term field measured yield data provides good opportunity to assess the impacts of climate and management on crop production. This study used the yield results from a long-term field experiment (1979–2012) at Luancheng Experimental Station in the central part of the North China Plain (NCP) to analyze the seasonal yield variation of winter wheat (Triticum aestivum L.) under the condition of sufficient water supply. The yield change of winter wheat over the last 33 growing seasons was divided into three time periods: the 1980s, the 1990s, and the years of 2001–2012. The grain yield of winter wheat during the 1980s was relative stable. During the 1990s, the annual yield of this crop was continuously increased by 193 kg/ha/year (P < 0.01). While for the past 12 years, yield of winter wheat was maintained at relative higher level, but with larger seasonal yield variation than that back in 1980s. CERES-Wheat model was calibrated and was used to verify the effects of management practices on grain yield. Seven scenarios were simulated with and without improvements in management. The simulated results show that the yield of winter wheat was decreased by 5.3% during 1990s and by 9.2% during the recent 12 seasons, compared with that during 1980s, under the scenario that the yield of winter wheat was solely affected by weather. Seasonal yield variation caused by weather factors was around −39% to 20%, indicating the great effects of weather on yearly yield variation. Yield improvement by cultivars was around 24.7% during 1990s and 52.0% during the recent 12 seasons compared with that during 1980s. The yield improvement by the increase in soil fertility and chemical fertilizer input was 7.4% and 6.8% during the two periods, respectively. The initial higher soil fertility and chemical fertilizer input might be the reasons that the responses of crop production to the further increase in chemical fertilizer were small during the simulation period. Correlation analysis of the grain yield from the field measured data with weather factors showed that sunshine hours and diurnal temperature difference (DTR) were positively, and relative humidity was negatively related to grain yield of winter wheat. The climatic change trends in this area showed that the DTR and sunshine hours were declining. This type of climatic change trend might further negatively affect winter wheat production in the future.