红树林区硅藻丰度和生物量构成及与底栖动物的关系

对深圳福田红树林湿地中百亩区、上沙、下沙、沙嘴、观鸟亭等 5个亚区中的硅藻种类、丰度和生物量等进行了研究。结果显示 ,5区中硅藻门藻类在种类及丰度组成上均为优势类群。硅藻总生物量以观鸟亭最高 ,达 2 5 .0 76mg/L ,下沙 8.44 6mg/L ,百亩区 4.488mg/L ,沙嘴 2 .111mg/L ,上沙仅为 0 .742mg/L。最高与最低硅藻总生物量相差可达 38倍。生物量分布趋势和其丰度分布相似 ,相关系数为 0 .998,但每一单种硅藻生物量之间存在着较大差异。

富营养化对波罗的海沿海水域硅藻生活型和物种丰度的影响

营养和沉积物负荷的增加影响沿海生态系统的生物多样性和功能。由于缺乏长期监测数据,本研究通过古湖泊学研究方法对栖息地和硅藻多样性的时间变化进行了评估。本文研究了过去大约200年内芬兰湾水体富营养化对硅藻群落结构和物种丰度的影响。浮游硅藻丰度随水体富营养化和浊度的升高而显著增加。在总溶解氮浓度低于400～600g/L的阈值后,底部生境减少,硅藻物种丰度显著下降;数据分析表明多样性和生产力之间并不呈单峰型关系。城市样点物种丰度随19世纪末城市化进程而显著下降,由于20世纪80年代中期点源负荷的停止而使其中两个城市样点的丰度得以恢复,然而由于大集水区负荷扩散效应的影响,第三个样点的物种丰度没有恢复的迹象。农村样点的变化较小,且20世纪40年代后才开始发生变化。

硅藻与色素在古环境演化研究中的意义——以固城湖为例

根据固城湖GS_1孔沉积物中硅藻的丰度与组合、色素的含量与有关参数,并结合孢粉、有机碳等分析数据,较详细地讨论了从晚冰期到全新世中期(15.3～6.0ka B.P.)固城湖地区古气候古环境演化的过程。同时尝试把硅藻与色素的结合作为度量湖泊古初始生产力的有效性,以及识别沉积记录有关人类活动的可能性。文中还专门论述了全新世初期海相硅藻出现的层位特点与背景,并与太湖作了比较,这一现象对重新认识长江三角洲地区的古地理环境无疑是十分重要的。

南海晚第四纪硅藻遗体及其地质意义 Ⅷ.几个问题的讨论

本文根据分析结果阐述了两种不同样品处理方法所获得的硅藻丰度和微型硅藻的人主要种类和相对百分含量。研究表明洗涤富集法所获得的硅藻丰度存在较大误差；微型硅藻的含量普遍介于10％～20％之间，最高可达42．31％，最低为5．66％，并指出了在微型硅藻相对含量大于20％的样品中，其主要种类为具槽直链藻和条纹小环藻等沿岸底栖种，并成群体产出。最后指出了伯戈根管藻和短刺角毛藻在三柱样剖面中的数量分布与晚第四纪的气候冷暖更替无密切联系。

数据报告：布莱克海台997站位晚中新世至更新世的硅藻

ODP997站位位于大西洋布莱克海台上。布莱克海台的海底沉积受到墨西哥湾流和西部边界潜流的极深影响，其上覆亚热带中心旋回的外围海水，暖盐的墨西哥湾流和西部边界潜流（WBUC）搬运了大量的碎屑沉积物到布莱克海台形成泥砂漂移（图1）。船上超微化石分析和沉积物粒度分析发现：沉积速率随深度增加呈增加趋势，三个层位的硅藻丰度有显著高异常（Shipboard Scientific Party，1996）。因此，研究地层中硅藻堆积速率变化对于了解这一地区的古海洋学和沉积史是非常重要的。

Long-term ecological interactions between nutrient and phytoplankton community in the Changjiang estuary

Both nitrate((NO_3)^-) and soluble reactive phosphate((PO_4)^(3-)) concentration in the freshwater end-member at the mouth of the Changjiang River have increased dramatically since the 1960s.Within the same period in the sea area,with surface salinity>30,(NO_3)^-concentration has shown an obvious increase,(PO_4)^(3-) has not changed greatly and dissolved reactive silica((SiO_3)^(2-)) has deceased dramatically.An examination of the elemental ratio of(NO_3)^-to(PO_4)^(3-) at the mouth of the Changjiang River did not show a systematic trend from the 1960s to 2000s largely because both nutrients increased simultaneously.In comparison,the elemental ratio of dissolved inorganic nitrogen(DIN) to(PO_4)^(3-) in surface seawater,with salinity>22,has shown a clearly increasing trend.Furthermore,an overall historical change of the(SiO_3)^(2-):(PO_4)^(3-) ratio has undergone a reverse trend in this area.Based on the changes of(SiO_3)^(2-):(PO_4)^(3-) and DIN:(PO_4)^(3-) ratios,we can conclude that an overall historical change of(SiO_3)^(2-):DIN ratio has decreased in this area from the 1950-1960s to 2000s.The argument that phytoplankton productivity in the Changjiang estuary has been enhanced by increasing nutrient input from the riverine transport was supported by these results.A comparative study analyzing the shift of phytoplankton composition from the mid-1980s to 2000s was also made.The results indicated that the average yearly percentage of diatom species in the Changjiang estuary has decreased from 84.6% during 1985-1986 to 69.8% during 2004-2005.Furthermore,the average yearly percentage of diatom abundance in the Changjiang estuary decreased from 99.5% during to 75.5% over the same time period,while the abundance of dinoflagellates has increased dramatically,from 0.7% to 25.4%.

Diatom distribution as an environmental indicator in surface sediments of the West Philippine Basin

The distribution of diatoms from surface sediments of the West Philippine Basin was analyzed, with 68 species and varieties of diatoms from 26 genera identified. Diatom abundance varied spatially, with the absolute abundance of diatoms ranging from 0 to 3.4× 104 frustules/g. The seven tropical pelagic diatoms were Alveus marinus, Azpeitia africana, Azpeitia nodulifera, Hemidiscus cuneiformis, Hernidiscus cuneiformis var. ventricosus, Roperia tesselata and Rhizosolenia bergonii. The relative abundance of these species was greater than 20%, and their distribution pattern in the sediments was overlaid by the flow of the Kuroshio Current. Ethmodiscus rex was present at 159 stations, formed the most abundant and dominant species in the diatomaceous ooze, and thus referred to as Ethmodiscus ooze. Ethmodiscus rex was also a major contributor to primary production in the region. A principal component analysis was employed to explain the relationship between samples and variations in diatom species from the WPB. Four diatom assemblages were distinguished, representing different oceanographic conditions; their spatial distributions were closely related with the North Equatorial Current and Kuroshio Current patterns in the region. These diatom assemblages can therefore be useful in deciphering late Quaternary palaeoceanographic reconstructions of the West Philippine Basin.

Diatom diet selectivity by early post-larval abalone Haliotis diversicolor supertexta under hatchery conditions

Benthic diatoms constitute the primary diet of abalone during their early stages of development. To evaluate the dietary preferences of early post-larval abalone, Haliotis diversicolor supertexta, we analyzed the gut contents of post-larvae that settled on diatom films. We compared the abundance and species diversity of diatom assemblages in the gut to those of the epiphytic diatom assemblages on the attachment films, and identified 40 benthic diatom species in the gut contents of post-larvae 12 to 24 d after settlement. The most abtmdant taxa in the gut contents were Navicula spp., Amphora copulate, and Amphora coffeaeformis. Navicula spp. accounted for 64.0% of the cell density. In the attachment films, we identified 110 diatom species belonging to 38 genera. Pennate diatoms were the dominant members including the species Amphiprora alata, Cocconeis placentula var. euglypta, Cylindrotheca closterium, Navicula sp. 2, and A. coffeaeformis. Nano-diatoms （〈20 pm in length） accounted for a considerable proportion of the total species number and cell density of the diatom assemblages in the gut contents and on the films. This suggests that nano-diatoms are important to the efficient production of abalone seed. The difference of the composition and abundance of diatoms between in the guts and on the biofilms suggests that early post-larval grazing was selective. An early post-larval abalone preferred nano-diatoms and the genera Navicula and Amphora during the month after settlement.

Diatom assemblages in surface sediments from the South China Sea as environmental indicators

We studied diatom distribution from 62 samples from the uppermost 1 cm of sedimem in the South China Sea （SCS）, using grabs or box corers in three cruises between 2001-2007. Fifty six genera, 256 species and their varieties were identified. Dominating species included Coscinodiscus africanus, Coscinodiscus nodulifer, Cyclotella stylorum, Hemidiscus cuneiformis, Melosira sulcata, Nitzschia marina, Roperia tesselata, Thalassionema nitzschioides, Thalassiosira excentrica, and Thalassiothrix longissima. Most surface sediments in the SCS were rich ill diatoms, except for a few coarse samples. Average diatom abundance in the study area was 104 607 valve/g. In terms of the abundance, ecology, and spatial distribution, seven diatom zones （Zones 1-7） were recognized. Zone 1 （northern continental shelf） is affected by warm currents, SCS northern branch of the Kuroshio, and northern coastal currents; Zone 2 （northwestern continental shelf） is affected by intense coastal currents; Zone 3 （Xisha Islands sea area） is a bathyal environment with transitional water masses; Zone 4 （sea basin） is a bathyal-to-deep sea with stable and uniform central water masses in a semi-enclosed marginal sea; Zone 5 （Nansba Islands marine area） is a pelagic environment with relatively high surface temperature; Zone 6 （northern Sunda Shelf） is a tropical shelf environment; and Zone 7 （northern Kalimantan Island shelf area） is affected by warm waters from the Indian Ocean and coastal waters. The data indicate that these diatom zones are closely related to topography, hydrodynamics, temperature, nutrients and especially the salinity. Better understanding of the relationship between diatom distribution and the oceanographic factors would help in the reconstruction of the SCS in the past.

Effect of hydrological variability on diatom distribution in Poyang Lake, China

Poyang Lake is the largest freshwater lake in China, and it has a seasonal flooding cycle that significantly changes the water level every year. The aim of this paper was to explain how these hydrological changes influence diatom populations in Poyang Lake. The yearly hydrological cycle can be divided into 4 phases: low water-level phase, increasing water-level phase, high water-level phase and decreasing waterlevel phase. Variations in the abundance of planktonic diatoms were studied using quarterly monitoring data collected from January 2009 to October 2013. Generally, diatoms were dominant in Poyang Lake and accounted for more than 50% of the total phytoplankton biomass except in July 2009(26%) and January 2012(35%). Aulacoseira granulata and Surirella robusta were the predominant species in all four phases, and they accounted for 25.02% to 56.89% and 5.07% to 14.78% of the total phytoplankton biomass, respectively. A redundancy analysis(RDA) showed that changes in physico-chemical parameter were related to the water level, and changes in diatom biomass were related to nitrite levels and p H. These results indicate that changes in environmental parameters related to both seasonal variations and water-level fluctuations caused variations in diatom biomass and community composition in Poyang Lake. Furthermore, extreme hydrological events can have different influences on the diatom community composition in the main channel and lentic regions. This research provides data on the diatom variations in Poyang Lake and will be useful for establishing biological indicators of environmental change and protecting Poyang Lake in the future.

Environmental change and its effects on inter-decadal variations of diatom production, species composition and frustule dissolution in a coastal marginal sea

The implications of climate change during the second half of the 20th century have been reported throughout the world. Although marginal seas are sensitive to climate change and anthropogenic impacts, relatively little attention has been given to the South East Asian marginal seas. Thus, to bridge this gap in knowledge, a sediment core was collected from the coastal areas of the Leizhou Peninsula in the South China Sea （SCS） to study the inter-decadal climate change and its consequences using diatom species composition as a proxy record. Diatom absolute abundance varied from 2 300 to 68 000 and averaged 16 000 valves per gram of dry weight （v/gdw）. The fractional dissolution index （F~） was usually below 0.5, which indicates low to moderate preservation of diatom valves at coastal area of the SCS. At the inter-decadal time scale, total diatom abundance was high for the period after 1972, which coincided with 1） increased percentage of planktonic diatom abundance and F~; 2） emergence and dominance of high productivity indicative cosmopolitan species such as Thalassionema nitzschioides and Paralia sulcata （their relative abundance increased from 〈1.5% to 〉7% for the period before and after 1972, respectively）; 3） decreased relative abundance of the small-sized eutrophication indicative species, Cyclotella striata, from 70% to 40%. This study reveals that variations in the abundance of diatoms preserved in the sediment was a function of both production and dissolution/preservation of diatom valves, which in turn was intimately connected to the prevailing environmental/climatic conditions. In conclusion, these data reveal the existence of substantial changes in the coastal SCS in response to the 1970s climate shift that was recorded in different parts of the world.

Nano-and microphytoplankton community characteristics in brown tide bloom-prone waters of the Qinhuangdao coast,Bohai Sea, China

Since 2009, the newly recorded species Aureococcus anophagefferens has successively induced brown tides in the Qinhuangdao coastal waters of the Bohai Sea. Here, we focus on the phytoplankton community structure in this region and try to point out the biological background characteristics of the outbreaks of successive brown tides. We analyzed species composition,cell abundance, diversity indices and size-fractionated chlorophyll a(Chl-a) concentration monthly from March 2013 to January2014. The phytoplankton community, as observed by microscopy, underwent succession from nano-celled chained diatoms to dinoflagellates in the spring and summer, and then to micro-celled diatoms and nano-celled chained diatoms as the most prominent groups in the subsequent autumn and winter. Canonical correspondence analysis revealed that changes in the abundance of diatoms were related to nutrient availability, especially of nitrogen, while water temperature was the crucial factor influencing the abundance of dinoflagellates and A. anophagefferens. Considering the contribution of nano-celled chained species to the micro-sized Chl-a,small phytoplankton(<20 μm) composed the majority of total Chl-a and were generally abundant during our study. Abundant and diverse small phytoplankton seemed to serve as a background or seedbank for the formation of blooms of A. anophagefferens and other small-celled algae.