南海某些表层沉积硅藻的分布及其古环境意义

本文通过对南海表层沉积物样品的硅藻分析,试图揭示南海某些表层沉积硅藻的分布规律,以便为南海古海洋学研究提供科学依据。研究发现,Thalassionema nitzshioides为南海地区表层沉积硅藻的优势种,且其百分含量无明显的区域差异,体现了南海与周围海洋水体交换相对较弱的特征。除此之外,南海表层沉积硅藻的分布主要受到海洋环流的影响,表现在黑潮暖流、印度洋暖水的入侵以及沿岸流对南海表层沉积硅藻分布的影响。其中,Nitzshia marina, Azpeitia neocrenulata , Azpeitia africana , Rhizosolenia bergonii等暖水硅藻可作为黑潮暖流及印度洋暖水入侵南海强度的指标种。而Cyclotella stylorum , Cyclotella striata , Diploneis bombus , Traychneis aspera , Tabularia tabulata等则可看作判断沿岸流对南海水体影响强度的标志种。     

春季季风转换期间孟加拉湾的初级生产力

2010年中国科学院东北印度洋科学考察期间,对孟加拉湾水域初级生产力展开了研究.孟加拉湾表层水体的水温较高,盐度变化范围较大,且上层水体营养盐含量较低,在真光层底部营养盐浓度突然增加.表层叶绿素a浓度较低(＜0.1 mg/m3),叶绿素a最大值常出现在75 m水深处,上层水体浮游植物的生长受氮限制明显.表层潜在初级生产力低于0.2mgcm-3h-1,且初级生产速率在50-75 m出现最大值.水柱中初级生产力变化范围为199-367 mgCm-2d-1,高值出现在88°-89°(E)附近.浮游植物固碳的主要贡献者是微微型浮游生物(＜3 μm),其次是小型浮游生物(＞20 μm)和微型浮游生物(3-20 μm),但表层与75 m水深处固碳浮游植物的结构有一定差异.将孟加拉湾与阿拉伯海初级生产力进行对比,孟加拉湾水体初级生产力显著低于阿拉伯海,且初级生产力的影响因素有着显著的差异.     

超级台风“南玛都”对南海北部叶绿素a、温盐及溶解氧的影响

利用实测与遥感数据综合分析2011年南海北部叶绿素a(Chl-a)、温度、盐度及溶解氧(DO)对台风"南玛都"的响应。结果表明,台风过后一周,南海北部上层海水温度降低、Chl-a和盐度升高;最靠近台风路径的水域较周围区域水温明显降低,盐度、Chl-a和DO均升高。其中Chl-a最大值出现在50—75 m深,而DO最大值出现在5 m深,DO高值区从5 m延伸至35 m深。与此同时,吕宋海峡北部出现明显的冷涡。综合分析各生态要素,台风"南玛都"过境引起的强烈海气相互作用和上升流对吕宋海峡附近海洋生态环境造成显著影响,同时该海区也可能受到台风过程中黑潮水入侵的影响。     

南海北部夏季基础生物生产力分布特征及影响因素

2008年夏季对南海北部不同海区的基础生物生产力(初级生产力及细菌生产力)进行了调查。结果表明,表层初级生产力(C)和真光层水柱初级生产力平均值(C)分别为(0.83±1.15)mg·m-·3h-1和(225.39±136.64)mg·m-·2d-1;表层细菌生产力(C)和真光层水柱细菌生产力平均值(C)分别为(0.14±0.19)mg·m-·3h-1和(128.14±74.86)mg·m-·2d-1。基础生产力的平面分布整体呈由近岸向深海降低的趋势,同时在西沙群岛邻近水域存在一个基础生物生产力的高值区。与环境因子的相关分析表明,温度、营养盐不是影响南海细菌生产力的主要因素,细菌生产力与浮游植物生物量及初级生产过程密切相关IBP:IPP比平均值为(67.55±37.13)%。与细菌生产力的分布规律不同,IBP:IPP比值在深海海域明显高于近岸水域,在吕宋海峡附近水域发现了IBP:IPP100%的高比值区,说明异养细菌在南海寡营养海域碳循环体系中的重要生态作用。     

2006年冬季南海北部浮游植物生物量和初级生产力及其环境调控

通过2006年2月在南海北部现场调查所获得的数据分析研究了海域的浮游植物现存量和生产力,结果表明冬季浮游植物的分布特征与东北季风引起的环流场的变化关系密切。调查海域水柱平均Chla浓度的变化范围为0.03～1.21mg·m-3（平均（0.33±0.33）mg·m^-3）,高值区出现在广东沿岸及海南岛东部附近海域;初级生产力的分布范围为41.3～1040.0mgC·m^-2d^-1。由于东北季风引起近岸水体混合剧烈,不利于浮游植物生长,因此虽然沿岸带Chla浓度（（0.53±0.50）mg·m^-3）较高,但初级生产力却是最低的,只有41.3mgC·m^-2d^-1,同时冬季反气旋涡强度下降和底层富营养水的涌升,营养盐充足,因此开阔海的Chla浓度（（0.31±0.30）mg·m^-3）和初级生产力（（631.3±578.0）mgC·m^-·2d^-1）均高。浮游植物粒度级份测定表明,Pico级份对冬季南海北部浮游植物现存量和生产力的贡献很大,特别是在开阔海区,分别占47%和66%。     

强台风鲶鱼对中国南海浮游植物及渔业资源的影响

利用 Aqua 卫星搭载的 MODIS 传感器数据, 分析了慢速移动的强台风“鲶鱼” (Megi, 2010)对中国南海北部海表面温度(SST)、海表面叶绿素 a 浓度(Chl-a)、初级生产力(PP)和渔业资源的影响。结果显示在研究区域内 , SST 平均值从台风前的28.8 ℃下降到台风后的 25.6 ℃, SST 最大下降 5 ℃; Chl-a 平均值从台风前的 0.099 mg⋅m–3 上升到 0.731 mg⋅m–3, 增长 6.4 倍。应用初级生产力垂向归纳模型反演 PP, 结果表明台风“鲶鱼”极大的提高了研究区域的 PP, 台风过后 8 d 内 PP 为 1001.5 mg⋅(C⋅m2⋅d)–1, 比2001-2009 年间平均值增加 684.9 mg⋅(C⋅m2⋅d)–1; 根据台风后 8d PP 估算此次台风额外固碳 1.01 Mt。应用营养动态、 Tait 和Cushing 模型估算台风引起的渔业资源增量为 10.1× 104 t。表明慢速移动的强台风对于渔业资源生产量有较大影响。     

东海赤潮高发区春季叶绿素a和初级生产力的分布特征

2002年4-5月对东海海域进行了综合调查,分析了海区叶绿素a和初级生产力的分布特性．结果表明,大面站表层平均叶绿素a浓度为1．086mg·m-3．分级叶绿素a结果显示．春季东海浮游植物以微型和微微型(<20μm)占优势,其对海区叶绿素a的贡献为64％,超微型浮游植物(<5μm)占浮游植物生物量的27％．营养盐分布和浮游动物的摄食压力影响了叶绿素a及其粒级结构的分布．平均初级生产力为10．091mg·m-3·h-1。赤潮跟踪的R-03、RL-01、RG-01站的平均初级生产力为399．984mg·m-3·h-1．光和营养盐成为叶绿素和初级生产力平面分布的主要限制因子．表层叶绿素a和初级生产力均在调查海区的123·E纵断面冲淡区产生高值区．DC-11站浮游植物生物量异常高,表层叶绿素a达到9．082mg·m-3,初级生产力为128．79mg·m-3·h-1．但并未出现水色异常．     

粤东沿岸生态系统对夏季沿岸上升流响应的生态模型初探

粤东上升流是出现于汕头沿岸直至福建沿岸南日群岛附近季节性上升流, 通常发生于6-9 月, 七月中旬最强。利用物理耦合生态动力学模型(ROMS-NPZD), 可以较好地模拟出粤东沿岸生态系统对夏季沿岸上升流的响应。根据模拟结果, 由于沿岸上升流的影响, 粤东沿岸海域在此期间表层海水会出现低温、高盐现象, 营养盐和高浮游植物最大浓度分布水层会出现上移, 但是浮游植物最大生物量出现时间会比粤东上升流最强的时期晚10 天左右。     

19万年以来南海北部MD12-3429站浮游有孔虫记录的表层海水环境演化

南海北部陆坡具有较高的沉积速率,为古海洋和古气候演化提供了绝佳的研究材料。本研究对南海北部陆坡中部MD12-3429站(20°08.52’N, 115°49.84’E,水深903 m)的高分辨率沉积样品中的浮游有孔虫群进行研究,重建了海洋氧同位素期(MIS)6期以来上部水体结构和表层古生产力变化。并与陆坡底部MD12-3432站(19°16.88’N,116°14.52’E,水深2 125 m)对比,旨在进一步探讨南海北部陆坡上部水体环境的时空演化。结果表明：受到冰期冬季风增强和表层环流变化的共同影响,海表温度具有显著的冰期/间冰期旋回,冬季海表温度波动可达7–8°C;MIS2–4期和MIS 6期时, MD12-3429站的温跃层明显比MD12-3432站的深,可能与海平面下降后、河流输入在近岸地区形成的淡水盖层和强冬季风通过埃克曼输送形成的向岸流有关;浮游有孔虫Globigerinoidesbulloides+Neogloboquadrinadutertrei含量和非共生种/共生种比值显示南海北部陆坡初级生产力在MIS 6期晚期和MIS 2期显著增高,这可能是当时较低的海平面和较强的...     

北部湾北部海域夏季微型浮游动物对浮游植物的摄食压力

2011年8月份于北部湾北部海域5个观测站位获得的分层水样,分析了表层叶绿素a含量和表层微型浮游动物丰度以及类群组成;同时于现场采用稀释培养法研究了该海域浮游植物生长率(μ)和微型浮游动物的摄食率(g)。分析和测定结果表明:调查海区的微型浮游动物丰度400—1167个/L,类群组成以无壳纤毛虫为主;浮游植物的生长率为-1.50—1.13 d-1,微型浮游动物摄食率为0.33—1.08 d-1;推算微型浮游动物对浮游植物现存量以及初级生产力的摄食压力分别为28.1%—66.0%和-7.4%—438.4%。相对于中国其他海区,8月份北部湾北部海域微型浮游动物摄食速率处于中等水平。调查期间,广西沿海高生产力海区,浮游植物生长率大于微型浮游动物动物的摄食率,浮游植物生物量处于积累期;涠洲岛以南海域,浮游植物生产力较低,微型浮游动物摄食作用是控制浮游植物生长的重要因素。     

Influence of Typhoon Matsa on Phytoplankton Chlorophyll-a off East China

Typhoons can cause strong disturbance, mixing, and upwelling in the upper layer of the oceans. Rich nutrients from the subsurface layer can be brought to the euphotic layer, which will induce the phytoplankton to breed and grow rapidly. In this paper, we investigate the impact of an intense and fast moving tropical storm, Typhoon Matsa, on phytoplankton chlorophyll-a (Chl-a) concentration off East China. By using satellite remote sensing data, we analyze the changes of Chl-a concentration, Sea Surface Temperature (SST) and wind speed in the pre- and post-typhoon periods. We also give a preliminary discussion on the different responses of the Chl-a concentration between nearshore and offshore waters. In nearshore/coastal regions where nutrients are generally rich, the Chl-a maximum occurs usually at the surface or at the layer close to the surface. And, in offshore tropical oligotrophic oceans, the subsurface maxima of Chl-a exist usually in the stratified water column. In an offshore area east of Taiwan, the Chl-a concentration rose gradually in about two weeks after the typhoon. However, in a coastal area north of Taiwan high Chl-a concentration decreased sharply before landfall, rebounded quickly to some degree after landfall, and restored gradually to the pre-typhoon level in about two weeks. The Chl-a concentration presented a negative correlation with the wind speed in the nearshore area during the typhoon, which is opposite to the response in the offshore waters. The phenomena may be attributable to onshore advection of low Chl-a water, coastal downwelling and intensified mixing, which together bring pre-typhoon surface Chl-a downward in the coastal area. In the offshore area, the typhoon may trigger increase of Chl-a concentration through uptake of nutrients by typhoon-induced upwelling and entrainment mixing.     

Physical-Biological Coupling in the Western South China Sea: The Response of Phytoplankton Community to a Mesoscale Cyclonic Eddy

It is widely recognized that the mesoscale eddies play an important part in the biogeochemical cycle in ocean ecosystem, especially in the oligotrophic tropical zones. So here a heterogeneous cyclonic eddy in its flourishing stage was detected using remote sensing and in situ biogeochemical observation in the western South China Sea (SCS) in early September, 2007. The high-performance liquid chromatography method was used to identify the photosynthetic pigments. And the CHEMical TAXonomy (CHEMTAX) was applied to calculate the contribution of nine phytoplankton groups to the total chlorophyll a (TChl a) biomass. The deep chlorophyll a maximum layer (DCML) was raised to form a dome structure in the eddy center while there was no distinct enhancement for TChl a biomass. The integrated TChl a concentration in the upper 100 m water column was also constant from the eddy center to the surrounding water outside the eddy. However the TChl a biomass in the surface layer (at 5 m) in the eddy center was promoted 2.6-fold compared to the biomass outside the eddy (p < 0.001). Thus, the slight enhancement of TChl a biomass of euphotic zone integration within the eddy was mainly from the phytoplankton in the upper mixed zone rather than the DCML. The phytoplankton community was primarily contributed by diatoms, prasinophytes, and Synechococcus at the DCML within the eddy, while less was contributed by haptophytes_8 and Prochlorococcus. The TChl a biomass for most of the phytoplankton groups increased at the surface layer in the eddy center under the effect of nutrient pumping. The doming isopycnal within the eddy supplied nutrients gently into the upper mixing layer, and there was remarkable enhancement in phytoplankton biomass at the surface layer with 10.5% TChl a biomass of water column in eddy center and 3.7% at reference stations. So the slight increasing in the water column integrated phytoplankton biomass might be attributed to the stimulated phytoplankton biomass at the surface layer.     

A model for the prediction of harmful algae blooms in the Vietnamese upwelling area

Satellite pictures and in situ observations indicate strong phytoplankton blooms including harmful algae blooms (HABs) during southwest (SW) summer monsoon in the Vietnamese upwelling area. In this period, nutrients are provided by coastal upwelling and by the very high river runoff from the Mekong River. During SW monsoon, in general two circulation patterns exist which allow the prediction of advection and diffusion of HAB patches. A Lagrangian HAB model that is driven by a circulation model and applied to HABs in Vietnamese waters is presented. Advection which is the most complicated part in modelling transport of passive substances is validated with a Lagrangian sediment trap experiment. The model produces realistic results compared to in situ observations and satellite images and might be used for real time forecast in the future.     

Chlorophyll <Emphasis Type="Italic">a</Emphasis> as a measure of seasonal coupling between phytoplankton and the monsoon periods in the Gulf of Oman

We present data from a long time-series study to describe the factors that control phytoplankton population densities and biomass in the coastal waters of Oman. Surface temperature, salinity, nutrients, dissolved oxygen, chlorophyll a (Chl a), and phytoplankton and zooplankton abundance of sea water were measured as far as possible from February 2004 through February 2006, at two stations along the southern coast of the Gulf of Oman. The highest concentrations of Chl a (3 mg m⁻³) were recorded during the southwest monsoon (SWM) when upwelling is active along the coast of Oman. However, results from our study reveal that the timing and the amplitude of the seasonal peak of Chl a exhibited interannual variability, which might be attributed to interannual differences in the seasonal cycles of nutrients caused either by coastal upwelling or by cyclonic eddy activity. Monthly variability of SST and concentrations of dissolved nitrate, nitrite, phosphate, and silicate together explained about 90% of the seasonal changes of Chl a in the coastal ecosystem of the Gulf of Oman. Phytoplankton communities of the coastal waters of Oman were dominated by diatoms for most part of the year, but for a short period in summer, dinoflagellates were dominant.     

Ageostrophic Frontal Processes Controlling Phytoplankton Production in the Catalano-Balearic Sea (Western Mediterranean)

Buoyancy-induced unstable boundary currents and the accompanying retrograde density fronts are often the sites of pronounced mesoscale activity, ageostrophic frontal processes, and associated high biological production in marginal seas. Biophysical model simulations of the Catalano-Balearic Sea (Western Mediterranean) illustrated that the unstable and nonlinear southward frontal boundary current along the Spanish coast resulted in a strain-driven frontogenesis mechanism. High upwelling velocities of up to 80 m d^-1 injected nutrients into the photic layer and promoted enhanced production on the less dense, onshore side of the front characterized by negative relative vorticity. Additional down-front wind stress and heat flux (cooling) intensified boundary current instabilities and thus ageostrophic cross-frontal circulation and augmented production. Specifically, entrainment of nutrients by relatively strong buoyancy-induced vertical mixing gave rise to a more widespread phytoplankton biomass distribution within the onshore side of the front. Mesoscale cyclonic eddies contributed to production through an eddy pumping mechanism, but it was less effective and more limited regionally than the frontal processes. The model was configured for the Catalano-Balearic Sea, but the mechanisms and model findings apply to other marginal seas with similar unstable frontal boundary current systems.     

Plankton response to weakening of the Iberian coastal upwelling

Coastal upwelling regions, which are affected by equatorward‐wind variability, are among the most productive areas of the oceans. It has been suggested that global warming will lead to a general strengthening of coastal upwelling, with important ecological implications and an impact on fisheries. However, in the case of the Iberian upwelling, the long‐term analysis of climatological variables described here reveals a weakening in coastal upwelling. This is linked to a decrease of zonal sea level pressure gradient, and correlated with an observed increase of sea surface temperature and North Atlantic Oscillation. Weakening of coastal upwelling has led to quantifiable modifications of the ecosystem. In outer shelf waters a drop in new production over the last 40 years is likely related to the reduction of sardine landings at local harbors. On the other hand, in inner shelf and Ria waters, the observed weakening of upwelling has slowed down the residual circulation that introduces nutrients to the euphotic layer, and has increased the stability of the water column. The drop in nutrient levels has been compensated by an increase of organic matter remineralization. The phytoplankton community has responded to those environmental trends with an increase in the percentage of dinoflagellates and Pseudonitzschia spp. and a reduction in total diatoms. The former favors the proliferation of harmful algal blooms and reduces the permitted harvesting period for the mussel aquaculture industry. The demise of the sardine fishery and the potential threat to the mussel culture could have serious socio‐economic consequences for the region.     

Theory of the Upper Limit to Phytoplankton Production per Unit Area in Natural Waters

Using the maximum quantum yield of photosynthesis, the maximum daily integral of photosynthetically active radiation (PAR) and the euphotic zone depth as a basis, general formulae for the upper limits to gross and net carbon fixation in natural waters are derived by theoretical considerations. The results are compared with a set of extremely high production data published by independently working authors, including data from algal mass cultures, oxidation ponds, freshwater and salt lakes, reservoirs, rivers and canals, coastal and other marine waters, including upwelling areas. The comparison reveals a quite surprising degree of agreement and suggests that the derived formulae represent a new, theoretically sound general approach to phytoplankton production. In particular, it can be shown that the upper limit to phytoplankton production in natural waters is about three times higher than earlier estimates in the literature. The maximum energy efficiency is of the same order of magnitude as in terrestrial plant communities.     

Hydrography and characteristics of the phytoplankton in shelf and oceanic waters off southeastern Brazil during winter (July/August 1982) and summer (February/March 1984)

The physical and chemical environment, and the phytoplankton primary production of southeastern Brazil were studied in relation to the general oceanographic structure during two research cruises (winter and summer). In each cruise, a total of 91 stations were occupied. Data were collected on the spatial distribution of nutrients, phytoplankton biomass and photosynthetic capacity over the coastal, shelf and oceanic areas off São Paulo, Paraná and Santa Catarina States.During wintertime, the mixing processes between tropical warm waters of the Brazil Current and subantarctic waters of the Malvinas Current formed strong environmental gradients. The drainings of Rio de La Plata and Lagoa dos Patos are transported northwards by coastal currents, enriching the shelf waters off Santa Catarina State with inorganic nutrients and consequently increasing the chlorophyll a to the highest concentrations (> 3.5 mg m ^–3) measured during the two cruises. In slope waters chlorophyll values were always low (0.05–0.45 mg m ^–3). The chlorophyll within the euphotic layer varied from 8.8–36.7 and 1.2–18.5 mg m^–2 during winter and summer, respectively.The surface photosynthetic rates during winter and summer cruises ranged respectively from 0.21–9.17 and 0.66–19.60 mgC/mgChl.a/h. The mean rates were higher in nearshore waters and decreased seaward.The thermal structure of the water column affected the vertical distribution of chlorophyll a and photosynthesis within the euphotic zone; During unstratified periods (winter) they were uniformly distributed but the occurrence of subsurface peaks of chlorophyll and strong photosynthetic inhibition of low light adapted cells in deeper layers are associated to the seasonal thermocline. Occasionally, upwelling of deep waters from shelf break enriched the deeper euphotic layers in offshore areas. Intensive upwelling was observed off Paranagua Bay (Parana State) and the mechanisms of its formation are discussed.     

Occurrences of harmful algal blooms (HABs) associated with ocean environments in the South China Sea

Harmful algal blooms (HABs) occur frequently in the South China Sea (SCS), causing enormous economic losses in aquaculture. We analyzed historical HAB records during the period from 1980 to 2003 in SCS. We found that HABs-affected areas have expanded and the frequency of HABs varied during this period. The seasonal and annual variations, as well as causative algal species of HABs are different among the four regions. Areas with frequent HABs include the Pearl River Estuary (China), the Manila Bay (the Philippines), the Masinloc Bay (the Philippines), and the western coast of Sabah (Malaysia). HABs occurred frequently during March–May in the northern region of SCS, May–July in the eastern region, July in the western region, and year-round in the southern region. Among the species that cause HABs, Noctiluca scintillans dominated in the northern region, and Pyrodinium bahamense in the southern and eastern regions. Causative species also varied in different years for the entire SCS. Both P. bahamense and N. scintillans were the dominant species during 1980–2003. Some species not previously recorded formed blooms during 1991–2003, including Phaeocystis globosa, Scrippsiella trochoidea, Heterosigma akashiwo, and Mesodinium rubrum. Variations in HABs are related to various regional conditions, such as a reversed monsoon wind in the entire SCS, river discharges in the northern area, upwelling in Vietnam coastal waters during southwest winds and near Malaysia coastal waters during northeast winds, and eutrophication from coastal aquaculture in the Pearl River estuary, Manila Bay, and Masinloc Bay. Handling editor: D. Hamilton     

Nutrients distribution in the coastal water of East Asia relative to the Kuroshio

Nutrients in the coastal water of East Asia were surveyed from the point of contribution of the diluted water to the open water relative to the Kuroshio, the western boundary current. The Kuroshio runs along eastern Asia, sensing changes in environment in the coastal region. The nutrients-depleted water from the Kuroshio, close to the coastal water, provides heat energy and high saline water. The fresh water from the river contributes to the coastal water as diluted water and exhibits the entrainments of nutrient water into the Kuroshio. The nutrients are important parameters to monitor the interactions among the Kuroshio and inland waters. Nutrients exhibited a wide range of ratio between nitrate to phosphate, nitrate to silicate, and silicate to phosphate in East Asia as divergences from the Redfield ratios. The distribution of nutrients could also be monitored as the distribution of chlorophyll-a concentration using the ocean color sensors. Contrasts in chlorophyll-a concentration between the oligotrophic water of the Kuroshio and the trophic water of the coastal region exhibit the mixing process of two water masses. Although the chlorophyll-a concentrations estimated by the current ocean color algorithm over the coastal water are of insufficient accuracy, the distribution of chlorophyll-a concentration exhibits a variation of seasonal consumption of nutrients and response to the Kuroshio and river runoff.