New species of genera Tintinnopsis, Metacylis and Eutintinnus (Ciliophora, Spirotrichea, Tintinnida) from the Kuwaiti waters of the Arabian Gulf

The Kuwaiti waters occupy the northwestern part of the Arabian Gulf. These waters are shallow, well mixed, and characterized by a high level of biological productivity. Tintinnids form an important component of the microzooplankton community in Kuwaiti waters. They are particularly abundant in the northern waters of Kuwait, as well as in the waters of Kuwait Bay. However, the diversity of the tintinnid species has not been studied. Tintinnids were collected from Kuwaiti waters during a 1-year zooplankton survey, and tintinnid species were identified. In this paper four new species of tintinnids (Tintinnopsis failakkaensis, Metacylis pythos, Eutintinnus conicus, and E. contractus) are described from Kuwaiti waters. All these species occur commonly in these waters. Statistical comparative analysis is carried out on the basis of measurements taken from 400 specimens of tintinnids from Kuwaiti waters.     

Seasonal variation in the species composition of tintinnid cilates in Hiroshima Bay, the Seto Inland Sea of Japan

Seasonal changes in the species composition of tintinnid ciliateswere examined based on time-series samples taken at 2 week intervalsover a 3 year period in Hiroshima Bay, the Seto Inland Sea ofJapan. The maximum abundance of total tintinnids over the entireperiod was 5.7 x 10³ indi viduals l^– Among 32 speciesidentified, a consistent seasonal occurrence was recognizedin 22 species. The relationships between various environmentalfactors and the abundance of each species of tintinnids wereanalyzed using principal component analysis From this analysis,the abundance of many tintinnids was revealed to be associatedwith temperature, the <20 µm size fraction of chlorophylla and water column stability, but not with the <20 µmsize fraction of chlorophyll a, nor with salinity. From theseresults, tintinnid species were divided into five associationtypes: species whose abundance increased with increasing temperature,decreasing temperature, nanophytoplankton abundance, increasingwater column mixing, or increasing water stratification coupledwith low temperature.     

Abundance and biogeography of tintinnids (Ciliophora) and associated microzooplankton in the Southwestern Atlantic Ocean

Absolute abundances of foraminifers, polycystine and phaeodarian radiolarians, tintinnids, pteropods and early crustacean larvae and moults were assessed in a collection of 57 vertically stratified (0-100 m) net microplankton samples from 22 stations located between 34 and 58S (along 51-56°W), covered on 8-16 November 1994. Tintinnids were identified to species and measured in order to estimate their biomass from biovolume to carbon conversions. The distribution of the microzooplanktonic groups assessed was irregular and patchy, both geographically and vertically, and their abundances were characteristic of oceanic low to medium productivity environments. Tintinnid biomass was also generally low (0.05-0.40 g Cl^-1). With the exception of the tintinnids, associations between microzooplanktonic numbers and chlorophyll a were generally loose. Eighty-eight tintinnid taxa were recorded, yet only five accounted for 53% of the specimens identified. Multivariate (cluster) analysis of tintinnid specific distribution patterns clearly showed several distinct zones. From north to south, these are: Transition Zone (TZ), with three subzones, TZ north (34°S-38°S), TZ central (39°44S-44°S) and TZ south (46°S); Subantarctic Zone (SZ; 48-55°S); Polar Front Zone (55°30S); Antarctic Zone (AZ; 58-59°36S). Each of these was characterized by distinct tintinnid assemblages, abundance and biomass. With few exceptions, tintinnid cells were fairly evenly distributed throughout the upper 50 m. Taxonomic composition usually changed little with depth. Mean population depths were calculated for a subset of 35 tintinnids; 29 of these dwell preferably above 40 m. The spatial distribution of tintinnid species richness showed a more or less gradual decrease from north to south. Specific diversity and equitability generally increased with depth, and were higher in antarctic waters than the southern transitional and subantarctic ones; this trend is tentatively attributed to higher water column vertical stability south of the Polar Front.      

Roles of sulfate adsorption and base cation supply in controlling the chemical response of streams of western Virginia to reduced acid deposition

Micro-organisms are vital for the functioning of all food webs and are the major drivers of the global biogeochemical cycles. The microbial community compositions and physicochemical conditions of the different water masses in the North Sea, a biologically productive sea on the northwestern European continental shelf, were studied during two summer cruises, in order to provide detailed baseline data for this region and examine its microbial biogeography. For each cruise the stations were clustered according to their physicochemical characteristics and their microbial community composition. The largest cluster, which covered most of the central and northern North Sea, consisted of stations that were characterized by a thermally stratified water column and had low chlorophyll a autofluorescence and generally low microbial abundances. The second main cluster contained stations that were dominated by picoeukaryotes and showed the influence of influxes of North Atlantic water via the English Channel and south of the Shetland Islands. The third main cluster was formed by stations that were dominated by cyanobacteria and nanoeukaryotes in the reduced salinity Norwegian Coastal and Skagerrak waters, while the fourth cluster represented the German Bight, a region with strong riverine input, high nutrient concentrations, and consequently high heterotrophic bacterial and viral abundances. Despite the complex and dynamic hydrographic nature of the North Sea, the consistent distinctions in microbiology between these different hydrographic regions during both cruises illustrate the strong links between the microbial community and its environment, as well as the possibility to use microorganisms for long-term monitoring of environmental change.     

2013年夏威夷东南部海区表层砂壳纤毛虫的群落结构和分布特征

鉴于东太平洋热带海区表层砂壳纤毛虫和其他微型浮游动物的群落结构资料几乎空白, 我们于2013年8月14日至9月18日在夏威夷东南部海区的23个站位采样调查了表层砂壳纤毛虫群落。23个站位共采集到砂壳纤毛虫22属36种, 均为透明壳种类。各站砂壳纤毛虫种丰富度范围为15-21种, 总丰度范围为4,730-23,693个/m³, 生物量范围为9.60-88.61 μg C/m³。本海区主要优势种为镯形囊坎虫(Ascampbelliella armilla)、斯廷细瓮虫(Steenstrupiella steenstrupii)、薄壳真铃虫(Eutintinnus tenuis)和纤弱细瓮虫(Steenstrupiella gracilis), 这4种主要优势种的口径范围不同。     

莱州湾大型砂壳纤毛虫群落季节变化

为揭示莱州湾砂壳纤毛虫群落季节变化规律, 在莱州湾设置8个站位, 于2011年5-11月及2012年3-4月进行了9个航次的调查, 用浅海III型浮游生物网由底至表垂直拖网采集砂壳纤毛虫。结果表明, 莱州湾3-11月砂壳纤毛虫物种丰富度的变化范围为5-19, 周年变化呈现一峰两谷的趋势。丰度的范围为0-318 ind./L, 丰度较大(> 50 ind./L)的种类有运动类铃虫(Codonellopsis mobilis)和清兰拟铃虫(Tintinnopsis chinglanensis)。各月平均丰度随时间的变化趋势为双峰型, 最大值出现在7月(63 ind./L), 次峰值出现在5月(48 ind./L), 最小值出现在3月(2 ind./L)。黏着壳种类在3-11月均有出现, 透明壳种类仅在温度较高(> 15°C)的6-9月出现。各月的优势种数目为1种(5月)到8种(8月), 其中运动类铃虫在所有月中都是优势种, 对砂壳纤毛虫丰度周年的变化规律产生较大影响。使用各月所有种类的平均丰度对各月砂壳纤毛虫群落进行聚类分析, 得到两个群落(相似度30%): 群落I(7-9月)和群落II(3-6月、10-11月), 说明砂壳纤毛虫群落发生了明显的季节变化。砂壳纤毛虫的物种丰富度、丰度与环境因子(温度、盐度)均没有明显的相关性。     

The composition and distribution of the particulate matter in the Strait of Magellan (Chile) during the 1991 and 1995 Italian campaigns

During 1991 and 1995, the Italian National Program for Antarctic Research carried out two oceanographic campaigns in the framework of the International (Strait of) Magellan Project. In this paper, we describe the distribution, biochemical composition, and mineralogical characteristics of particulate matter and the characteristics of the water masses defining microbasins in the Strait of Magellan. The data analyses highlighted differences in quality and quantity of the suspended matter and its organic component in the basins that make up the Strait and the Pacific Ocean. The westernmost basin is subject to an eastward flow from the Pacific Ocean, and continental runoff in the surface layers, which are consequently rich in organic matter with a high C:N ratio. The central basin, Isla Carlos III–Segunda Angostura, is characterized by the mixing of Sub-Antarctic Pacific waters, continental runoff, and glacio-fluvial waters: The basin has the lowest particulate matter concentration, but at Paso Ancho showed high concentrations of organic matter with a lower C:N ratio. The easternmost basin, Segunda Angostura-Atlantic entrance, is characterized by the mixing of the water column due to strong Atlantic tides and showed high concentration of particulate matter with a high detritic component. Generally, the organic matter concentrations showed significant differences during the cruises, being higher in 1991. Using the multivariate discriminant factor analysis to determine whether statistically significant differences existed between defined sampling areas, we determined that temperature, particulate organic carbon, and total particulate matter were the variables most important for the difference between areas.     

Boreal Tintinnid Assemblage in the Northwest Pacific and Its Connection with the Japan Sea in Summer 2014

Tintinnids are planktonic ciliates that play an important role in marine ecosystem. According to their distribution in the world oceans, tintinnid genera were divided into several biogeographical types such as boreal, warm water, austral and neritic. Therefore, the oceanic tintinnid assemblage could be correspondingly divided into boreal assemblage, warm water assemblage and austral assemblage. The purpose of this study was to investigate the characteristics of boreal tintinnid assemblage in the Northwest Pacific and the Arctic, and to identify the connection between boreal tintinnid assemblage and neighboring assemblages. Surface water samples were collected along a transect from the East China Sea to the Chukchi Sea in summer 2014. According to the presence of boreal genera and warm water genera, three tintinnid assemblages (the East China Sea neritic assemblage, the Japan Sea warm water assemblage, and the boreal assemblage) were identified along the transect. The boreal assemblage extended from the Chukchi Sea to the waters north of the Sōya Strait. Densities peaks occurred at stations in the two branches of the Alaska Current and decreased both northward and southward. The densities were <10 ind./dm³ at most stations in Arctic region. The dominant genera (Acanthostomella, Codonellopsis, Parafavella, and Ptychocylis) accounted for 79.07±29.67% (n = 49) of the abundance in the boreal assemblage. The densities of the dominant genera covaried with strongly significant positive correlations. Tintinnids with lorica oral diameter of 22–26 μm and 38–42 μm were dominant and contributed 67.35% and 15.13%, respectively, to the total abundance in the boreal assemblage. The distribution and densities of tintinnids in the study area suggest that the Sōya Strait might be a geographical barrier for tintinnids expansion.     

春季和秋季东海陆架区浮游纤毛虫的丰度和生物量

于2011年春季(5月)和秋季(11月)在东海陆架区进行浮游纤毛虫丰度和生物量的调查.春季和秋季纤毛虫的平均丰度分别为(614±861)和(934±809) ind·L^-1,平均生物量分别为(1.70±3.91)和(0.93±0.99) μg C·L^-1.表层纤毛虫丰度和生物量的高值区春季主要分布在近岸及远岸海区,秋季主要分布在远岸海区.春季纤毛虫的丰度和生物量在水体上层较高;秋季纤毛虫主要分布在水体上层,有时在水体底层也会出现丰度和生物量的高值.春季无壳纤毛虫群落的粒级较大,秋季较小.砂壳纤毛虫占纤毛虫丰度的平均比例春季和秋季分别为(26.9±34.3)%和(44.9±25.2)%.两个季节共鉴定出砂壳纤毛虫27属52种,春季丰度较大的种为原始筒壳虫、橄榄领细壳虫及筒状拟铃虫,秋季丰度较大的种为原始筒壳虫、小领细壳虫及矮小拟铃虫.纤毛虫丰度与温度、叶绿素a(Chl a)浓度呈显著正相关.砂壳纤毛虫丰度与盐度呈显著负相关,群落结构变化与温度显著相关.     

Diazotrophic diversity and distribution in the tropical and subtropical Atlantic Ocean

To understand the structure of marine diazotrophic communities in the tropical and subtropical Atlantic Ocean, the molecular diversity of the nifH gene was studied by nested PCR amplification using degenerate primers, followed by cloning and sequencing. Sequences of nifH genes were amplified from environmental DNA samples collected during three cruises (November-December 2000, March 2002, and October-November 2002) covering an area between 0 to 28.3 degrees N and 56.6 to 18.5 degrees W. A total of 170 unique sequences were recovered from 18 stations and 23 depths. Samples from the November-December 2000 cruise contained both unicellular and filamentous cyanobacterial nifH phylotypes, as well as gamma-proteobacterial and cluster III sequences, so far only reported in the Pacific Ocean. In contrast, samples from the March 2002 cruise contained only phylotypes related to the uncultured group A unicellular cyanobacteria. The October-November 2002 cruise contained both filamentous and unicellular cyanobacterial and gamma-proteobacterial sequences. Several sequences were identical at the nucleotide level to previously described environmental sequences from the Pacific Ocean, including group A sequences. The data suggest a community shift from filamentous cyanobacteria in surface waters to unicellular cyanobacteria and/or heterotrophic bacteria in deeper waters. With one exception, filamentous cyanobacterial nifH sequences were present within temperatures ranging between 26.5 and 30 degrees C and where nitrate was undetectable. In contrast, nonfilamentous nifH sequences were found throughout a broader temperature range, 15 to 30 degrees C, more often in waters with temperature of <26 degrees C, and were sometimes recovered from waters with detectable nitrate concentrations.     

A seasonal study of the distributions of surface state variables in Liverpool Bay. I. winter data

The physical, chemical, and biological characteristics of the surface waters of Liverpool Bay were investigated during six seasonal cruises in 1975. The winter data has been analysed to provide criteria by which spatial and temporal changes in the distributions of surface state variables during the seasonal production cycle may be judged. Surface distribution maps observed during two winter cruises (January and December) were markedly dissimilar. This temporal variability is attributed to changing circulation patterns within the Bay induced by variations in magnitude and direction of wind stress. Despite the ‘visual’ dissimilarity in spatial distributions observed on the two cruises, principal component analysis demonstrates a similar general background which is dominated by conservative physical mixing of sea and fresh waters. During winter, the spatial variability in water characteristics originated at the boundaries of the cruise path and spread internally, primarily as a consequence of the differing composition of the source waters, to the sea area. No internal sources or sinks, either anthropogenically or biologically induced, were encountered during the winter cruises.     

宁津近岸海域大型底栖动物生态学特征和季节变化

宁津海域位于山东半岛东端,南北黄海交界处. 根据2007年1、4、7及10月4个航次(冬、春、夏、秋)对宁津近岸海域大型底栖动物调查资料,采用优势度指数、物种多样性指数、丰富度指数、均匀度指数,Bray-Curtis相似性聚类分析以及MDS标序等方法,分析了该区域内大型底栖动物的生态学特点和季节变化.结果表明： 该区域共采集到大型底栖动物243种,其中多毛类动物96种;软体动物43种;甲壳动物77种;棘皮动物13种;其他类群动物14种.各季度优势种有变化也有重叠,拟特须虫和日本倍棘蛇尾为4个季度共有优势种.调查海域年平均生物量为9.5 g·m^-2,最高生物量出现在春季,最低出现在冬季;年平均丰度为219.6 ind·m^-2,最高丰度出现在冬季,最低出现在秋季.物种多样性指数(H)变化范围2.82～3.23,物种丰富度指数(D) 2.28～2.75,物种均匀度指数(J) 0.82～0.86.聚类分析结果表明,4个航次群落分布格局均包含近岸群落和远岸群落;大型底栖动物群落结构与水深和底质等环境因子密切相关.     

Microzooplankton and tintinnid species-specific assemblage structures: patterns of distribution and year-to-year variations in the Weddell Sea (Antarctica)

Silicoflagellates, large heterotrophic dinoflagellates, radiolarians,tintinnids and micro-crustaceans were counted in 72 screened(15 µm) samples retrieved at 0–150 m from the WeddellSea in January 1989. Tintinnid species were identified and biomassestimates were carried out for all groups on the basis of measurementsof cell dimensions. Dinoflagellates dominated the micro-heterotrophiccommunity at all stations and depths (65% of overall microzooplanktoniccarbon in the 0–150 m interval), followed by the tintinnids(18%), microcrustaceans (16%) and radiolarians (1%). All groups,with the exception of silicoflagellates, peaked noticeably inthe vicinity of the southern end of the transect (76–77°S).Relationships between concentrations of chlorophyll a and microzooplanktonicbiomass were present, yet not altogether consistent, but bothphyto- and microzooplankton seemed to generally respond to regionalenhancements associated with the ice edge. Comparison with similarWeddell and Weddell-Scotia data retrieved in February-March1987 and November 1988-December 1989, respectively, are highlycoherent in terms of microplanktonic abundances, their geographicand vertical distribution patterns, and the specific make-upand distribution of tintinnid assemblages. Analyses of the oraldiameters of tintinnid morphotypes suggest that the latitudinaland vertical distribution of their five dominant taxa (whichaccount for >90% of all individuals) is structured so asto maximize resource partitioning.     

Repartition des Appendiculaires au large des cotes de Californie

Twenty-seven taxa of appendicularians have been identified fromthe cruise CALCOFI n° 7202 and their distribution has beenstudied by various numerical methods, with the purpose of definingsimultaneously the groups of associated species and the groupsof stations possessing similar characteristics. Two large recurrentgroups have been defined by the method of Fager and McGowan,corresponding approximatively to the major water masses present:central Pacific waters and equatorial Pacific waters. The methodof Williams and Lambert permits the separation of 11 southernstations and a northern group divided into 2 subgroups dependingon the presence or absence of O. dioica. The rank correlationsgive results very similar to those obtained with point correlations.Finally, principal component analysis allow good separationof the northern and southern zones by the factorial plan 1–3,while representation of the stations by the factorial plan 2–3separates the two northern subgroups depending on the presenceor absence of O. dioica. The results obtained by the differentmethods are therefore very much alike, but it is difficult toconclude they are a result of the specific cruise, or whetherthey represent a general phenomenon.     

Summer in the Ensenada Front: The distribution of phytoplankton species, July 1985 and September 1988

Two interdisciplinary cruises took place in the Ensenada Frontalregion during July 1985 and September 1988. This paper discussesthe distribution of phytoplankton species along one sectionfrom each cruise. Each year, the overall dominant species wasEmiliania huxleyi. Although hydrography of the euphotic zoneindicated the presence of water from three sources, the CentralPacific flora dominated the floral patterns. Recurrent groupanalysis identified two clusters of related groups of species,present in both years and separated by depth. These were similarto recurrent groups defined from the Climax area in the CentralNorth Pacific. Similarity maps indicated the presence of thetwo-layered structure that is characteristic of the CentralPacific flora. The transition between flora corresponded tothe depth of the chlorophyll maximum layer but also to the coolsalinity minimum layer that marks California Current water andthat is absent from the Central Pacific. The extensive entrainmentand persistence of Central Pacific flora in the Ensenada Frontalregion is unexpected.     

Varieties of a single cosmopolitan diatom species associated with surface water masses in the North Pacific

A time series of 65 sediment trap samples, representing 48-month changes in diatom flora, and 62 sediment core-tops from the western North Pacific Ocean were analyzed. Varieties of a single diatom species were found to be characteristic of two surface water masses bounded by the Kuroshio Current. Thalassionema nitzschioides var. incurvata, var. inflata and var. parva dominate in warm saline waters in the Subtropical Gyre, while T. nitzschioides sensu stricto is abundant in less-saline waters northwest of this current. Time series data on percent abundances for the three T. nitzschioides varieties in the T. nitzschioides complex are compared with path variations of the current south of Japan. Inter-annual fluctuations in percent abundance are linked to changes in surface water masses over the sediment traps in association with migration of the Kuroshio paths. This finding makes the percent abundance a useful tool for deciphering path migrations of the Kuroshio Current in the geologic past. Down-core analyses of two sediment cores collected beneath the modern Kuroshio Current were performed. A sharp increase in percent abundances from 12 to 9 kyr BP, with an abrupt change around 11 kyr BP, records the previously reported transition of the Kuroshio Current from a predominantly offshore path to its modern path. Path migrations of the Kuroshio Current may be inferred from percent abundances of these diatoms, which comprise a new proxy for delineating the paleoclimate of the northwestern Pacific in relation to changes in northward heat transport from the western equatorial Pacific Ocean by the western boundary current.     

Distribution of tintinnid species from 42° N to 43° S through the Indian Ocean

Taking advantage of the transfer of the Italian R/V “Italica” from Italy to New Zealand for the Italian Research Expedition in the Antarctic, surface sampling of plankton was carried out from 42°N to 43°S from 14 November to 16 December 2001. Collaboration between several Italian research groups resulted in the Mediterranean, Indian and Pacific Ocean Transect (MIPOT), aimed to merge oceanographic measurements with remotely sensed data and to study latitudinal changes in plankton communities. We present preliminary results on the tintinnids (abundance and species composition) along the MIPOT1 transect. Tintinnid distributions and food vacuole contents are discussed in relation to chlorophyll concentrations and contribution of phytoplankton size classes. Generally, chlorophyll concentrations were well below 0.5 mg m^?3 and tintinnid numbers were only a few tens per liter. Eighty-six tintinnid species belonging to 27 genera were recorded. Highest diversity and number of tintinnid species occurred in the warm-water regions, from the Mediterranean Sea to the Tropic of Capricorn. Shannon diversity index ranged from 1.0 (Tasman Sea) up to 2.9 (tropical Indian Ocean). Each of the oceanic provinces showed a well defined tintinnid assemblage, a tintinnid ‘fingerprint’ characterizing each area. Data are compared to previous records for the different areas and the persistence in time of typical tintinnid species is discussed.     

Environment and life cycles influence distribution patterns of hydromedusae in austral South America

We analysed hydromedusa assemblages of South America (from 22°S to 56°S and from 040°W to 080°W), their association with water masses and the influence of the life cycle on medusa distributions. The geographic distribution of 130 species of hydromedusae was compiled from literature reports (62 publications between 1913 and 2012). Seven areas were defined: Atlantic Magellanic, Argentinean, Pacific intermediate zone, Pacific Magellanic, Peruvian–Chilean, South Brazilian and Oceanic. The variance of the species–environment relationship was explained by depth and temperature. Distribution patterns of Atlantic hydromedusae are associated with neritic water masses, supporting previously proposed biogeographical provinces. Assemblages on the Pacific side of South America are under the influence of the Humboldt Current system, with a break in species distribution around Chiloé Island. Only the oceanic assemblage contained the same species in both the Pacific and Atlantic zones. We found that meroplanktonic medusae contributed more to define the neritic assemblages, while the oceanic assemblage was better defined by holoplanktonic medusae. Therefore, our data suggest that meroplanktonic hydromedusae appeared to be more restricted in distribution than holoplanktonic ones.     

Diazotrophic Diversity and Distribution in the Tropical and Subtropical Atlantic Ocean

To understand the structure of marine diazotrophic communities in the tropical and subtropical Atlantic Ocean, the molecular diversity of the nifH gene was studied by nested PCR amplification using degenerate primers, followed by cloning and sequencing. Sequences of nifH genes were amplified from environmental DNA samples collected during three cruises (November-December 2000, March 2002, and October-November 2002) covering an area between 0 to 28.3°N and 56.6 to 18.5°W. A total of 170 unique sequences were recovered from 18 stations and 23 depths. Samples from the November-December 2000 cruise contained both unicellular and filamentous cyanobacterial nifH phylotypes, as well as γ-proteobacterial and cluster III sequences, so far only reported in the Pacific Ocean. In contrast, samples from the March 2002 cruise contained only phylotypes related to the uncultured group A unicellular cyanobacteria. The October-November 2002 cruise contained both filamentous and unicellular cyanobacterial and γ-proteobacterial sequences. Several sequences were identical at the nucleotide level to previously described environmental sequences from the Pacific Ocean, including group A sequences. The data suggest a community shift from filamentous cyanobacteria in surface waters to unicellular cyanobacteria and/or heterotrophic bacteria in deeper waters. With one exception, filamentous cyanobacterial nifH sequences were present within temperatures ranging between 26.5 and 30°C and where nitrate was undetectable. In contrast, nonfilamentous nifH sequences were found throughout a broader temperature range, 15 to 30°C, more often in waters with temperature of <26°C, and were sometimes recovered from waters with detectable nitrate concentrations.     

The role of picoplankton (cyanobacteria and plastidic picoflagellates) in the diet of tintinnids

Food vacuole contents in naturally occurring populations oftintinnids in surface waters at the mouth of the Bay of Villefranchewere examined from November 1988 to December 1989. Three typesof prey were considered: cyanobactena (Synechococcus spp.),plastidic pico- and nanoflagel lates. The relative frequency(%) of these were observed in the diet of 18 tintinnid species.Results confirm that nanoflagellates constitute the dominantfraction in the diet of most of the tintinnids examined. Theyare preferentially ingested by some species, such as Amphoridesquadrilineata and Favella sp. Nevertheless, picoplankton isingested throughout the year by all the tintinnids, and canreach up to 100% of the ration mainly during winter and summer.Cyanobacteria are the prey most ingested by Rhabdonella spiralisand the only prey observed in food vacuoles of Salpingella acuminaia.As indicated by the Strauss linearity index values, picoflagellatesare actively grazed by some species (e.g. Dictyocysta elegans,Eutintinnus spp.). The implications of the ingestion of picoplanktonby tintinnids in the food webs are discussed.