Particulate carbohydrates in relation to phytoplankton in the euphotic zone of the Bransfield Strait

Summary The composition and depth distribution of particulate carbohydrates for 5 stations in the Bransfield Strait is discussed in relation to phytoplankton species composition. Glucose being the most prominent sugar at diatom dominated stations is reduced by 70% from the surface to 100 m depth whereas total carbohydrates show a 40% degradation. Values for a haptophyceae dominated station are 95 and 80%, respectively.     

东海春季水华期浮游植物生长与微型浮游动物摄食

2005年4～6月在东海有害水华频发区14个站位采样,通过现场稀释法实验对春季东海水域浮游植物比生长率和微型浮游动物比摄食率进行了研究.结果表明东海有害水华频发区浮游植物群落以甲藻为优势.浮游植物比生长率在水华爆发前相对较低,平均为1.18 d~(-1);进入水华期后比生长率明显升高,但在水华站位随现存量增加而降低;非水华区比生长率近岸高、远岸低.微型浮游动物主要以急游虫和桡足类幼体为主,而种类上以砂壳纤毛虫居多.微型浮游动物比摄食率在水华爆发前波动较大,介于0.53～1.73 d~(-1),平均为0.90 d~(-1);在水华区比摄食率较为稳定,浮游植物比生长率的降低导致群落净生长率持续下降;在非水华区,比摄食率整体较高,近岸低而远岸高.微型浮游动物的摄食对浮游植物群落的生长有一定的控制作用,但在水华爆发后这种控制作用将减弱.     

Species-specific phytoplankton sedimentation in relation to primary production along an inshore--offshore gradient in the Baltic Sea

The temporal and spatial variability in the quality and quantityof settling phytoplankton material in relation to concurrentprimary production was studied using sediment traps at threecoastal stations from a semi-enclosed bay (Pojo Bay) throughthe outer archipelago to the open Gulf of Finland. The fluxof settling phytoplankton was high (9.3 g C m^–2period^–1)in Pojo Bay, especially in spring, and lower in the archipelago(8.1 g C m^–2 period^–1) and open-sea area (5.2 gC m"2 period"1), although the primary production followed theopposite pattern. A large influx of allochthonous material intoPojo Bay in spring brought allochthonous phytoplankton cellsinto the traps, but limited primary production. Diatoms werethe most abundant settled phytoplankton at all stations, butthe species composition varied between Pojo Bay (Aulacoseiraspp., Rhizosolenia minima) and the outer stations (Skeletonemacostatum, Chaetoceros spp.)At the outer stations, migratingdinoflagellates (Peridiniella catenate) comprised part of thesettling material in spring. The high settling flux of the cyanophyteAphanizomenon flos-aquae is discussed. The species compositionof the phytoplankton assemblage influenced the proportion ofthe total organic carbon sedimentation that consisted of phytoplanktoncarbon.     

初秋南沙群岛海域网采浮游植物群落特征及其与环境因子的关系

根据2011年8-9月南沙群岛海域的生物和环境调查资料,对网采浮游植物的群落特征及其与环境因子的关系进行分析.结果表明: 在鉴定的3门34属113种网采浮游植物中,甲藻门和硅藻门种类各占57.5%和40.7%,其中硅藻门的角藻属种类最多,占30.1%.网采浮游植物平均丰度为2.12×10⁴ cell·m^-3,丰度高值区出现在北部礼乐滩多涡区域和南部万安气旋涡附近海域.蓝藻门束毛藻属是网采浮游植物的主要功能群,占海域平均丰度的77.0%.主要优势种为铁氏束毛藻、红海束毛藻和夜光梨甲藻.优势种(类)存在较明显的空间差异,蓝藻门在S₃、S₅、S₆和S₁₀~S₁₄站占优势;甲藻门在中部S₄、S₇~S₉站占优势,硅藻门在南部S₁和S₂站占优势.网采浮游植物多样性和均匀度指数分别为3.10和0.62.影响浮游植物群落特征的重要环境因子有盐度、水温、铵氮、亚硝酸盐、磷酸盐和硅酸盐,以及南沙中尺度气旋涡和南沙西部沿岸流.典范对应分析排序图较好地显示了浮游植物和环境因子之间的关系.     

Trophic cascading in the Polar Frontal Zone of the Southern Ocean during austral autumn 2002

Trophic cascading resulting from coupling among phytoplankton, protozooplankton (2–200 µm) and the mesozooplankton fractions <1,000 µm and <2,000 µm was investigated at three stations in the Polar Frontal Zone of the Southern Ocean during austral autumn 2002. In the absence of any grazers, net growth rate of the phytoplankton was positive and ranged between 0.209 and 0.402 day^–1. Among the heterotrophic components of the zooplankton, protozooplankton were identified as the most important consumers of the phytoplankton biomass. The low impact of the mesozooplankton on the phytoplankton may have been related to the inability of the larger grazers to feed efficiently on the small phytoplankton cells, which dominated the total chlorophyll concentration at two of the three sampling stations. It appears that the mesozooplankton <1,000 µm consumed protozooplankton, which resulted in a decrease in the impact of the latter organisms on the phytoplankton. The presence of predatory zooplankton (mainly chaetognaths and amphipods) >1,000 µm led to a decrease in the carnivory of the <1,000-µm mesozooplankton fraction on the protozooplankton. In this situation, protozooplankton were again able to exert a considerable impact on the phytoplankton.     

Structure of the Phytoplankton Community and Its Relationship to Water Quality in Donghu Lake, Wuhan, China

The phytoplankton community structure, in terms of species composition, total standing crop,and abundance of the dominant algal species, at four stations in Donghu Lake, Wuhan, China, was investigated monthly from January 1994 to December 1996. A total of 260 taxa was observed, of which Chlorophyta (106 taxa) contributed the highest portion of the total number of taxa, followed by Bacillariophyta (82 taxa)and Cyanophyta (32 taxa). The total standing crop measured by means of chlorophyll a content, cell density,and cell biovolume, as well as the abundance of the dominant species, declined in the order of Station I to Station Ⅳ. Seasonal changes of the standing crop varied greatly among the four stations. Although the cell density at the four stations showed a single peak within a year, the peak density varied from July to November, dependent on the sampling year and the station. For chlorophyll a content and cell biovolume,multiple peaks were observed at Stations Ⅰ and Ⅱ, but a single peak was found at Stations Ⅲ and Ⅳ. The phytoplankton community structure indicated that the trophic status was the highest at Station Ⅰ (most eutrophic), followed by Station Ⅱ; Stations Ⅲ and Ⅳ were the least trophic areas. The long-term changes in phytoplankton community structure further suggested that changes in phytoplankton community structure were correlated with water quality, and eutrophication of Donghu Lake had been aggravated since the 1950s.     

Structure of the Phytoplankton Community and Its Relationship to Water Quality in Donghu Lake, Wuhan, China

The phytoplankton community structure, in terms of species composition, total standing crop,and abundance of the dominant algal species, at four stations in Donghu Lake, Wuhan, China, was investigated monthly from January 1994 to December 1996. A total of 260 taxa was observed, of which Chlorophyta (106 taxa) contributed the highest portion of the total number of taxa, followed by Bacillariophyta (82 taxa) and Cyanophyta (32 taxa). The total standing crop measured by means of chlorophyll a content, cell density,and cell biovolume, as well as the abundance of the dominant species, declined in the order of Station I to Station IV. Seasonal changes of the standing crop varied greatly among the four stations. Although the cell density at the four stations showed a single peak within a year, the peak density varied from July to November, dependent on the sampling year and the station. For chlorophyll a content and cell biovolume,multiple peaks were observed at Stations I and II, but a single peak was found at Stations III and IV. The phytoplankton community structure indicated that the trophic status was the highest at Station I (most eutrophic), followed by Station II; Stations III and IV were the least trophic areas. The long-term changes in phytoplankton community structure further suggested that changes in phytoplankton community structure were correlated with water quality, and eutrophication of Donghu Lake had been aggravated since the 1950s.     

COMBINING NEW TECHNOLOGIES FOR DETERMINATION OF PHYTOPLANKTON COMMUNITY STRUCTURE IN THE NORTHERN GULF OF MEXICO 1

In situ analysis of phytoplankton community structure was determined at five stations along the Texas Gulf coast using two instruments, the Fluoroprobe and FlowCAM. Results were compared with traditional methods to determine community structure (pigment analysis and microscopy). Diatoms and small nanoplankton (most likely haptophytes) dominated the phytoplankton community at all stations. Estimated chl concentrations for diatoms+dinoflagellates obtained via the Fluoroprobe were not significantly different for three of the five stations sampled when compared with HPLC‐chemical taxonomy analysis, whereas the concentrations of green algal and cryptophyte chl were overestimated. The FlowCAM estimates of overall nanoplankton and microplankton cell abundance were not significantly different when compared with epifluorescence microscopy, and recorded images of phytoplankton cells provided a representative population of the phytoplankton community at each station. The Fluoroprobe and FlowCAM, when used in tandem, are potentially capable of determining the general characteristics of phytoplankton community structure in situ and could be an important addition to biological observing systems in the coastal ocean.     

Phytoplankton assemblages in the deep chlorophyll maximum layers off the Mediterranean coast of Israel

Phytoplankton assemblages in the deep chlorophyll maximum andnear-surface layers were compared at seven stations in the inshoreand offshore waters of the Mediterranean coast of Israel. Thestudy included the entire spectrum of taxonomic categories overa wide size range, comprising the nano/pico phytoplankton componentsdown to 1 µm and the larger phytoplankters consistingprimarily of diatoms and dino-flagellates. The coccolithophorids<20 µm and the monads constituted the most abundantcomponents of the phytoplankton at the deep chlorophyll maximum(DCM) and near surface layer. Certain individual species, mainlypennate diatoms and smaller dinoflagellates, seemed to adaptto the DCM to form a characteristic association.     

The Standing Stock of Diatoms and Dinoflagellates in the Oligotrophic Waters of Southern Aegean Sea

The hydrography and seasonal changes in the standing stock of diatoms and dinoflagellates were studied in 9 stations located in Southern Aegean Sea. The logarithms of the measurements of each stock in each station were subjected to analysis of variance with the factors “station” and “season”. The results suggested a uniform distribution of phytoplankton at all stations within every season. On the other hand there was a significant effect of season upon phytoplankton growth. The annual temperature range (14.2 d̀C-25.6 d̀C) and the phytoplankton cycle (maxima in spring and autumn) provided evidence of the temperate character of this area.     

The effects of nutrients and their ratios on phytoplankton abundance in Junk Bay,Hong Kong

Eutrophication has been considered to be undoubtedly one of the key factors stimulating phytoplankton growth, since it involves the enrichment of a water mass with both inorganic and organic nutrients supporting plant growth. Nutrient enrichment as a result of anthropogenic activity occurs in estuaries and coastal waters as well as in lakes and freshwater impoundments, and blooms of phytoplankton are one of the effects of such an accelerated process of nutrient enrichment. This paper presents the results of a two-year survey of the nutrients and phytoplankton at 3 stations in Junk Bay, Hong Kong, carried out from 1997 to 1998. The relationships between nitrogen, phosphorus, and their ratio, with phytoplankton abundance have been studied. The results show that the highest nitrogen concentration was in Station 2 which is close to a sewage input, whereas the highest phosphorus concentration was in Station 1 which is close to a landfill area. The mean N:P ratios at the three stations were between 8 and 14. The diatoms were the dominant group during most of the year but it seems that diatoms were more sensitive than dinoflagellates and other algal groups to the increase in nutrients.     

春季东海中华哲水蚤对有害藻华物种的选择性摄食

2005年4月27日—6月5日在东海有害藻华高发区的6个典型站位采样,分析了浮游植物的群落结构,并采用现场实验研究了中华哲水蚤(Calanus sinicus)的选择性摄食.结果表明,中华哲水蚤对浮游植物的选择性摄食具有食物密度依赖性.低浮游植物细胞丰度下中华哲水蚤具有明显的选择性摄食行为,高浮游植物细胞丰度下中华哲水蚤摄食选择性由偏好转变为排斥,浮游植物细胞丰度329 cells·ml^-1是中华哲水蚤由偏好趋于排斥摄食的阈值.中华哲水蚤的选择性摄食还与食物组成有关,对于食物中的微型浮游动物,中华哲水蚤无选择性或排斥摄食.有害藻华发生区中华哲水蚤对具齿原甲藻(Prorocentrum dentatum)的偏好摄食以及对米氏凯伦藻(Karenia mikimotoi)的排斥摄食,促使藻华的物种演替最终向米氏凯伦藻水华方向发展.     

Temporal and spatial variation of the phytoplankton assemblage in the eastern Indian sector of the Southern Ocean in summer 2001/2002

The abundance and species composition of phytoplankton were investigated at stations in a permanently ice-free (61°S) and seasonally ice-covered area (64°S and 66°30′S) in the eastern Indian sector of the Southern Ocean between November 2001 and March 2002. Although a phytoplankton bloom occurred just after retreat of the sea ice at both stations in the seasonally ice-covered area, vertical stability of the water column during the bloom was weak at the most southerly station. This shows that a bloom can form even under weak vertical stability. In the bloom, diatoms dominated under weak vertical stability and Phaeocystis under strong vertical stability. In the latter case, ice algae largely contributed to development of the bloom. In the later observation period, a subsurface chlorophyll maximum (SCM) was observed at 61°S and 64°S. Species composition was different between the mixed layer and SCM at 64°S, but was uniform with depth at 61°S, indicating that the SCM is formed by different mechanisms.     

Spatial distribution of phytoplankton productivity in the Amundsen Sea, Antarctica

To date, no direct measurements of primary production were taken in the Amundsen Sea, which is one of the highest primary productivity regions in the Antarctic. Phytoplankton carbon and nitrogen uptake experiments were conducted at 16 selected stations using a ¹³C–¹⁵N dual isotope tracer technique. We found no statistically significant depletions of major inorganic nutrients (nitrate?+?nitrite, ammonium, and silicate) although the concentrations of these nutrients were markedly reduced in the surface layer of the polynya stations where large celled phytoplankton (>20?μm) predominated (ca. 64?%). The average chl-a concentration was significantly higher at polynya stations than at non-polynya stations (p?<?0.01). Average daily carbon and nitrogen uptake rates by phytoplankton at polynya stations were 2.2?g?C?m^?2?day^?1 (SD?=?±1.4?g?C?m^?2?day^?1) and 0.9?g?N?m^?2?day^?1 (SD?=?±0.2?g?N?m^?2?day^?1), respectively, about 5–10 times higher than those at non-polynya stations. These ranges are as high as those in the Ross Sea, which has the highest productivity among polynyas in the Antarctic Ocean. The unique productivity patterns in the Amundsen Sea are likely due to differences in iron limitation, phytoplankton productivity, the timing of phytoplankton growing season, or a combination of these factors.     

Phytoplankton in the surface and chlorophyll maximum off southern California in August, 1978

A synoptic sampling of 30 stations in a 25 km x40 km grid closeto the southern California coast revealed that chlorophyll andphytoplankton biomass were higher nearshore and to the south,where relatively large dinoflagellates dominated. A subsurfacechlorophyll maximum was present at each station, near the nitraclineand 10% light level. Nearshore and to the south, these maximarepresented higher levels of phytoplankton biomass than at thesurface whereas at the other stations, chlorophyll maxima couldbe attributed to physiological changes in chlorophyll contentof small flagellated phytoplankton rather than to the accumulationof phytoplankton at depth. Univariate and multivariate statisticalprocedures were used to demonstrate that phytoplankton assemblagesseparated by tens of meters in the vertical were just as differentas those separated by tens of kilometers in the horizontal.We conclude that residence time of water near the coast is ofgreat importance to the determination of the abundance and taxonomiccharacteristics of phytoplankton, and that advection of offshorewater towards the coast was the major determinant of the patternobserved during our study. ¹Present address: University of Texas, Port Aransas Marine Laboratory,Port Aransas, TX 78373, USA     

春季赤潮频发期东海微型浮游动物摄食研究

2002年4～5月在东海长江口及其邻近水域的8、11、14、23和28号5个典型站位采样。用现场稀释法对春季东海水域浮游植物的生长率和微型浮游动物对浮游植物的摄食压力等方面进行了研究．结果表明,微型浮游动物的摄食行为在东海赤潮过程起到关键作用．各站位微型浮游动物主要以急游虫、红色中缢虫和夜光藻为主,在种类上砂壳纤毛虫是主要的类群．微型浮游动物的摄食速率范围在0．28～1．13d-1,对浮游植物现存量的摄食压力范围在35．14％～811．69％。对浮游植物潜在初级生产力的摄食压力范围在74．04％～203．25％,对浮游植物碳的摄食率范围在9．58～97．91μg·L-1·d-1,靠近岸边的站位,微型浮游动物的摄食速率、对浮游植物现存量的摄食压力和对浮游植物碳的摄食率相对较高。而远离岸边的站位对浮游植物潜在初级生产力的摄食压力却较高．与世界其它海区比较此水域微型浮游动物摄食压力处于较高水平．急游虫是控制东海主要赤潮原因生物具齿原甲藻生长的关键种类．     

The relationship between phytoplankton distribution and water column characteristics in North West European shelf sea waters

Phytoplankton underpin the marine food web in shelf seas, with some species having properties that are harmful to human health and coastal aquaculture. Pressures such as climate change and anthropogenic nutrient input are hypothesized to influence phytoplankton community composition and distribution. Yet the primary environmental drivers in shelf seas are poorly understood. To begin to address this in North Western European waters, the phytoplankton community composition was assessed in light of measured physical and chemical drivers during the "Ellett Line" cruise of autumn 2001 across the Scottish Continental shelf and into adjacent open Atlantic waters. Spatial variability existed in both phytoplankton and environmental conditions, with clear differences not only between on and off shelf stations but also between different on shelf locations. Temperature/salinity plots demonstrated different water masses existed in the region. In turn, principal component analysis (PCA), of the measured environmental conditions (temperature, salinity, water density and inorganic nutrient concentrations) clearly discriminated between shelf and oceanic stations on the basis of DIN:DSi ratio that was correlated with both salinity and temperature. Discrimination between shelf stations was also related to this ratio, but also the concentration of DIN and DSi. The phytoplankton community was diatom dominated, with multidimensional scaling (MDS) demonstrating spatial variability in its composition. Redundancy analysis (RDA) was used to investigate the link between environment and the phytoplankton community. This demonstrated a significant relationship between community composition and water mass as indexed by salinity (whole community), and both salinity and DIN:DSi (diatoms alone). Diatoms of the Pseudo-nitzschia seriata group occurred at densities potentially harmful to shellfish aquaculture, with the potential for toxicity being elevated by the likelihood of DSi limitation of growth at most stations and depths.     

Abundance and distribution of invertebrate larvae in the Bellingshausen Sea (West Antarctica)

The central part of the Bellingshausen Sea has been poorly studied, partly because of the presence of ice during most of the year. The main aim of this study was to analyse the abundance and distribution of meroplankton, and the influence of oceanographic properties were investigated in the Bellingshausen Sea (West Antarctica) during the BENTART-06 cruise carried out in January–February 2006. Zooplankton samples were collected with a 80-μm mesh plankton net hauled vertically from a depth of 200?m to the surface at fifteen stations across the Bellingshausen Sea. Fifteen types of larval benthic invertebrates were found, with echinospira and nudibranch veligers being the most abundant. Hierarchical analysis and non-metric multidimensional scaling revealed a high degree of spatial variability in both larval abundance and larval types across the Bellingshausen Sea. The variability was significantly correlated with total chlorophyll-a and the contribution of large (>5?μm) phytoplankton to total chlorophyll, indicating the availability of food as an important factor determining the larval distribution observed. Nudibranch veligers, nemertean pilidia, echinoderm and planula larvae were more abundant at stations in the central Bellingshausen Sea, which was characterized by low phytoplankton biomass and production. Higher abundances of echinospira veligers and polychaete larvae were found at the more productive stations close to Peter I Island and the Antarctic Peninsula. The abundance and diversity of larval types found in the Bellingshausen Sea during the BENTART-06 cruise support the hypothesis that indirect development through larval swimming stages plays a key role in benthic recruitment in polar areas.     

Production in the Sea of Okhotsk

Primary production, microbial production and the density of planktonic microheterotrophs were estimated at 40 stations in the Okhotsk Sea in July-August 1992 during the seasonal phytoplankton minimum. The primary production by phytoplankton remained rather high even during this minimum. At most stations it was >0.6-0.8 g m^-2 day^-1, and in leftover patches of spring diatom 'bloom' it reached >5 g C m^-2 day^-1. The deep maxima of phytoplankton at the upper boundary of the seasonal thermocline were an ordinary phenomenon. The depth of the euphotic zone was normally 30-50 m in the open sea and 12-25 m at the shelf station. Any correlations between the phosphate contents in the upper mixed layer and primary production were absent at the stations. There was no adaptation of the phytoplankton to the light deficiency in deep maxima layers. The total numbers of bacterioplankton were 1-1.5 x 10⁶ ml^-1 and its biomass was close to 100 mg m^-3 in the open sea. All these numbers were 2-3 times greater at the shelf stations. In deep waters, the bacterioplankton biomass decreased to 10-40 mg m^-3. The microbial production in the upper layer was high, at 50-100 mg m^-3, decreasing 50-100 times in the deep waters. The numbers of ciliates in the upper water layer varied from 3 to 6 x 10³ l^-1 and were 1.5-2 times greater than in the shelf areas. Ciliate biomass was 60-100 mg m^-3 in the upper mixed layer, and per square metre varied to 1.5-2.5 g. The dominant ciliate taxa belonged to the naked oligotrichid genera Strombidium and Tontonia. Tentative calculations were made of the basin's annual primary production and for the analysis of energy balance in the ecosystem.      

Factors controlling the seasonal development and distribution of the phytoplankton community in the lowland course of a large river in Northern Italy (River Adige)

The principal environmental factors influencing the seasonal dynamics of phytoplankton were examined from September 1997 to July 1998 in three stations along a 26-km stretch of the lowland course of River Adige (northeast Italy). Nutrient concentrations did not appear to be limiting for the phytoplankton growth. Annual minimum concentrations of reactive and total phosphorus, and dissolved inorganic nitrogen were 22 μg P l⁻¹, 63 μg P l⁻¹ and 0.9 mg N l⁻¹, respectively. The most critical forcing factors were physical variables, mainly water discharge and other variables related to hydrology, i.e. suspended solids and turbidity, which acted negatively and synchronously by diluting phytoplankton cells and decreasing light availability. Higher algal biomass was recorded in early spring, in conditions of lower flow velocity and increasing water temperature. In late spring and summer, higher water discharge caused a decrease in phytoplankton biomass. Conversely, low algal biomass in late autumn and winter, during low discharge, was mainly related to low water temperatures and shorter photoperiod. Physical constraints had a significant and measurable effect not only on the development of total biomass, but also on the temporal dynamics of the phytoplankton community. Abiotic and biotic variables showed a comparable temporal development in the three sampling stations. The small number of instances of spatial differences in phytoplankton abundance during the period of lower flow velocity were related to the increasing importance of biological processes and accumulation of phytoplankton biomass.