Observations on the ecological importance of salt marshes in the Cumberland Basin,a macrotidal estuary in the Bay of Fundy

The Cumberland Basin, a 118 km² estuary at the head of the Bay of Fundy which has an average tidal range of about 11m, contains large tracts of salt marsh (15% of the area below highest high water). Low marsh (below about 0·9 m above mean high water) is composed almost exclusively of Spartina alterniflora while the vegetation on high marsh is more diverse but dominated by Spartina patens. Because of its higher elevation, high marsh is flooded infrequently for short periods by only extreme high tides. Low marsh is inundated much more frequently by water as much as 4m deep for periods as long as 4 h per tide. Temporal variability in the occurrence of extreme tides influences the flooding frequency of high marsh for any given month and year. Using a modification of Smalley's method, the mean annual net aerial primary production (NAPP) of low and high marsh is estimated to be 272 and 172 g C m^?2, respectively. Vegetation turnover times average 1·0 and 2·0 y for low and high marsh, respectively. Because of abundant tidal energy, much of the low marsh production appears to be exported and distributed widely about the estuary. Since high levels of turbidity suppress phytoplankton production, salt marshes produce approximately half of the carbon fixed photosynthetically in the Cumberland Basin. It is concluded that salt marshes play a major ecological role in the Cumberland Basin.     

VERTICAL PROFII,ES OF CHL-A AND PRIMARY PRODUCTIVITY IN THE MIDDLE CONTINENTAL SHELF AREA AND EDDY AREA OF THE EAST CHINA SEA

Vertical profiles of chl-a and primary productivity in the middle continental shelf area and eddy area of the East China Sea were studied using data from a cruise in the East China Sea in February to March, 1997 and a cruise in July, 1998. The results showed that chl-a vertical distribution closely related to in situ hydrological and nutrient conditions. Chla-a concentration ranged from 0.22 to 0.35 mg/m³ and 0.93–1.09 mg/m³ in the eddy area and in the middle continental shelf area, respectively. In both areas, chl-a concentrations in deep layers were slightly higher than those in shallow layers, but was of the same order of magnitude. In summer, when a thermocline existed in the water column, highest chl-a concentrations appeared at the base of the thermocline layers in both areas. In the eddy area, chl-a concentration maximized at 31.743 mg/m³, and averaged 1.143 mg/m³ below 30 m depth. In the middle continental shelf area, the highest chl-a concentration was 2.120 mg/m³, the average was 1.168 mg/m³. The primary productivity reached 1418.76 mgC/(m²·d) in summer and 1360.69 mgC/(m²·d) in winter. In the eddy area, the primary productivity was 787.50 mgC/(m²·d) in summer and 159.04 mgC/(m²·d) in winter. Vertical carbon sinking rate from the deep layer to the bottom in both areas is also discussed in this paper. Contribution NO. 4183 from the Institute of Oceanology, Chinese Academy of Sciences. Project No. 49636210 supported by NSFC.     

软玉子料的形状规律及其应用

通过对软玉子料形状总结,发现子料多呈扁平状,其长宽比较小,磨圆好的子料形状可分为11类。这些特征可用于子料鉴别与特殊材料制作。     

1999年渤海浮游植物生物量的数值模拟

以浮游植物量、浮游动物量、营养盐浓度 (包括无机氮和无机磷 )以及碎屑量为生态变量 ,在HAMSOM水动力学模式的基础上构建了 1个三维浮游生态动力学NPZD模型。采用此模型研究了渤海 1999年浮游植物量和初级生产力的变化情况 ,模拟结果与实测基本相符。模拟结果表明 :1999年渤海浮游植物量的变化大致呈双峰分布 ,春季水华出现在4,5月份 ,秋季水华出现在 9,10月份 ;受透明度和局地水深的影响 ,渤海湾和辽东湾北部浮游植物量的年变化呈夏季大、冬季小的单峰分布。 1999年渤海不同海区初级生产力的变化特征是 :除莱州湾一年中有春、夏 2个峰值外 ,其它 3个海区都是夏季高、冬季低的单峰分布 ;1999年整个渤海年平均的初级生产力为 2 5 7mgC/m2 /d。     

三门湾秋季浮游植物现存量和初级生产力

对1987年9月浙江三门湾海区浮游植物细胞丰度、叶绿素a浓度和初级生产力的分布特征及其与环境的关系进行了研究。结果表明,调查海区的浮游植物细胞丰度、叶绿素a浓度和初级生产力均具有明显的空间区域性分布特征。叶绿素a浓度高值区位于三门湾顶部和健跳港口,从湾顶部往湾口海区方向,叶绿素a浓度逐渐下降。初级生产力的分布趋势与叶绿素a浓度的分布趋势一致。表层水浮游植物平均细胞丰度为(3.36±1.39)×103个/dm3,表、底层平均叶绿素a浓度分别为(1.47±0.42)μg/dm3和(1.12±0.19)μg/dm3,平均初级生产力为(36.0±29.5)mg/(m2·d)。     

大气中的有机氮化合物及其向海洋的沉降

近几年的研究表明,有机氮化合物是大气氮沉降的重要组成部分,对全球氮循环的贡献不可忽视。介绍了大气中有机氮化合物的组成、测定方法以及存在的问题,综述了大气有机氮化合物向海洋沉降的研究现状及其对海洋生态系统的影响,并探讨了未来的研究重点。     

Fluid flow equations governing primary oil migration as a separate phase

A mathematical model of primary oil migration as a separate phase out of compacting shales is presented. During burial and oil generation, source rock porosity decreases and oil saturation increases until residual oil saturation is reached. At this stage oil is expelled out by capillary and excess fluid pressure gradients. The model is a system of differential equations which relate changes in oil and water saturation in time to water and oil flow out of the source rock during burial. An additional set of equations for periods of erosion of overburden are also provided. The equations can be numerically solved by finite difference method. If oil and water flow is to be simulated during oil generation, then at each time step, changes by oil generation in oil and water saturations and porosity must be calculated. The solution procedure is briefly outlined.     

Seasonal Variations in Benthic Community Metabolism and Nitrogen Dynamics in a Shallow, Organic-Poor Danish Lagoon

The dynamics of benthic primary production and community respiration in a shallow oligotrophic, marine lagoon (Fællestrand, Denmark) was followed for 1·5 years. The shape of the annual primary production cycle was explained primarily by seasonal changes in temperature (r² = 0·67-0·72) and daylength (r² = 0·63), whereas temperature almost explained all variation in benthic community respiration (r² = 0·83-0·87). On a daily basis the benthic system was autotrophic during spring and summer supplied by 'new' and 'regenerated' nitrogen and predominantly heterotrophic during fall and winter caused by light and nutrient limitation. The linear depth-relationship between porewater alkalinity and ammonium indicated that the C:N ratio of mineralized organic matter is low in spring and summer (3-6) and high in fall and winter (9-16). This is inversely related to net primary production and thus the input of labile, nitrogen-rich algal cells. Accordingly, mineralization occurred predominantly in the upper 2-5 cm of the sediment. The pool of reactive material (microalgal cells) was estimated to account for 12% of total organic carbon in the upper 3 cm, and had an average turnover time of less than 1 month in summer. Assimilation of organic carbon by benthic animals was equivalent to about 30% of the annual gross primary production. Grazing reduced chlorophyll a concentration in the sediment during summer and spring to values 30-40% lower than in winter, but maintained a 3-4 times higher specific microalgal productivity. The rapid turnover of organic carbon and nitrogen, and important role of benthic microalgae showed that the benthic community in this oligotrophic lagoon is of a very dynamic nature.     

三门湾夏季浮游植物现存量和初级生产力

该海区的生物、化学、水文等项目进行调查。用HQM-1型有机玻璃采水器采集水样,大面观测站仅采集表层(0～1m)水样,用于测定叶绿素a质量浓度和光合作用速率。在N2和N11两个连续观测站,每隔3h采集表层和5m层的水样,用于分析叶绿素a质量浓度及营养盐浓度。同时,用浅 型浮游生物网由近底层向表层垂直拖网采集浮游植物样品,所采样品被装入容积为600cm3的塑料瓶中,并加入20cm3的福尔马林溶液固定保存,供对浮游植物细胞计数和种属鉴定之用。营养盐样品用经酸预清洗过的孔径为0.45μm的醋酸纤维膜过滤,滤液用饱和HgCl2溶液固定后,低温避光保存。图…     

Atmospherically-promoted photosynthetic activity in a well-mixed ecosystem: Significance of wet deposition events of nitrogen compounds

Wet atmospheric deposition of dissolved N, P and Si species is studied in well-mixed coastal ecosystem to evaluate its potential to stimulate photosynthetic activities in nutrient-depleted conditions. Our results show that, during spring, seawater is greatly depleted in major nutrients: Dissolved Inorganic Nitrogen (DIN), Dissolved Inorganic Phosphorus (DIP) and Silicic acid (Si), in parallel with an increase of phytoplanktonic biomass. In spring (March–May) and summer (June–September), wet atmospheric deposition is the predominant source (>60%, relative to riverine contribution) for nitrates and ammonium inputs to this N-limited coastal ecosystem. During winter (October–February), riverine inputs of DIN predominate (>80%) and are annually the most important source of DIP (>90%). This situation allows us to calculate the possibility for a significant contribution to primary production in May 2003, from atmospheric deposition (total input for DIN ≈300 kg km⁻² month⁻¹). Based on usual Redfield ratios and assuming that all of the atmospheric-derived N (AD-N) in rainwater is bioavailable for phytoplankton growth, we can estimate new production due to AD-N of 950 mg C m⁻² month⁻¹, during this period of depletion in the water column. During the same episode (May 2003), photosynthetic activity rate, considered as gross primary production, was estimated to approximately 30 300 mg C m⁻² month⁻¹. Calculation indicates that new photosynthetic activity due to wet atmospheric inputs of nitrogen could be up to 3%.