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Strombidium is a species‐rich genus of oligotrichid ciliates mainly inhabiting the marine pelagial. In molecular phylogenies, the genus emerged as non‐monophyletic, and cladistic analyses suggest that it is largely characterized by plesiomorphies. A reliable split of the genus and the establishment of new genera necessitate, however, support by novel morphological and/or ultrastructural features. In the present study, the arrangement and ultrastructure of trichites are proposed as taxonomically relevant characters. Strombidium biarmatum Agatha et al., 2005 differs in the trichite pattern from the type species Strombidium sulcatum and most congeners. Aside from the trichites inserting anteriorly to the girdle kinety and generating the typical funnel‐shaped complex in the posterior cell portion, the species displays additional trichites between the adoral membranelles even visible in live cells. Here, this exceptional trichite arrangement is detailed based on transmission electron microscopic investigations. In molecular phylogenies, S. biarmatum forms a monophylum with two congeners sharing its trichite arrangement. Therefore, the strombidiid genus Heteropilum nov. gen. is established with S. biarmatum as type species to also include H. paracapitatum (Song et al., 2015) nov. comb. and H. basimorphum (Martin & Montagnes, 1993) nov. comb. Further differences discovered in the trichite ultrastructure support the organelles' taxonomic significance. [ABSTRACT FROM AUTHOR]

Ocean internal waves appear as irregular bright and dark stripes on synthetic aperture radar (SAR) remote sensing images. Ocean internal waves detection in SAR images consequently constituted a difficult and popular research topic. In this paper, ocean internal waves are detected in SAR images by employing the faster regions with convolutional neural network features (Faster R-CNN) framework; for this purpose, 888 internal wave samples are utilized to train the convolutional network and identify internal waves. The experimental results demonstrate a 94.78% recognition rate for internal waves, and the average detection speed is 0.22 s/image. In addition, the detection results of internal wave samples under different conditions are analyzed. This paper lays a foundation for detecting ocean internal waves using convolutional neural networks. [ABSTRACT FROM AUTHOR]

Although the taxonomy of oligotrich ciliates has been widely investigated, yet the species diversity remains poorly known. We newly designed a pair of oligotrich-specific LSU rDNA primers covering the 600-bp D1/D2 region, and it was effective for detecting oligotrich species. Using the primers, we constructed the cloning libraries to investigate the species diversity of oligotrichs in the northern coastal waters of the South China Sea. In total, 165 oligotrich sequences were obtained from five widely separated sampling sites. Sixty operational taxonomic units (OTUs) were obtained at 99% similarity threshold, and low-abundance OTUs with no more than two sequences contributed most of these (about 78%). Our findings are consistent with previous morphological studies, Strombidium was found the most abundant and widely distributed genus in this area. In addition, the BLAST search in the NCBI database resulted in 95% OTUs matching with named oligotrich species in similarity below 99%. Therefore, oligotrich morphospecies diversity has been underestimated as low-abundance species, and the LSU rDNA oligotrich sequence database needs to be better promoted. [ABSTRACT FROM AUTHOR]

Abstract The marine oligotrich ciliate Strombidium sulcatum , the best known marine oligotrich of the marine microozoplankton, was first cultured in Villefranche-sur-Mer 35 years ago. Cultures were maintained from 1983 to 2003 and used in 22 studies investigating a very wide variety of questions. Here we review the major findings of these studies and underline their contributions to our knowledge of planktonic ciliate ecology and microbial ecology in general. We conclude with the observation that while ecophysiology has apparently fallen out of fashion, culture work will likely return as an invaluable resource in our present 'omics' era. [ABSTRACT FROM AUTHOR]

Abstract: The morphology and phylogeny of four oligotrichid ciliates, Parallelostrombidium paraellipticum sp. n., P. dragescoi sp. n., P. jankowskii (Xu et al. 2009) comb. n., and P. kahli (Xu et al. 2009) comb. n., are described or redescribed based on live observation, protargol stained material, and SSU rRNA gene sequences. The new species P. paraellipticum sp. n. is characterized by its obovoidal cell shape, adoral zone composed of 17–21 collar, 9–11 buccal, and two thigmotactic membranelles, and extrusomes attached in one row along the girdle kinety. The new species P. dragescoi sp. n. is distinguished from its congeners by its obovoidal cell shape and a lack of thigmotactic membranelles. Based on ciliary patterns recognizable in the original slides, Omegastrombidium jankowskii Xu et al. 2009 and O. kahli Xu et al. 2009 should be transferred to the genus Parallelostrombidium Agatha 2004. Phylogenetic analyses based on SSU rRNA gene sequence data demonstrate that all four new sequences cluster with previously described congeners. The genus Parallelostrombidium is separated into two clusters, suggesting its non‐monophyly and probably corresponding to the two subgenera proposed by Agatha and Strüder‐Kypke (2014), as well as their morphological difference (cell dorsoventrally flattened vs. unflattened). [ABSTRACT FROM AUTHOR]

This study presents a new taxon of Sphenopsida, Paragiridia taioensis nov. gen. et sp. The specimens were recovered from the Bruno Peiker Outcrop, municipality of Taió, state of Santa Catarina in southern Brazil, and are preserved as impressions or compressions. They represent an autochthonous monospecific assemblage constituted of delicate plant parts, some of them still connected to each other, allowing a reconstruction of the whole plant. The root system of P. taioensis is composed of unbranched, non-articulate and continuously striated axes, covered with thin rootlets irregularly on the entire surface, sometimes dichotomized; Paracalamites -like articulated axes; and Phyllotheca -like leaf whorls. The reproductive structure is represented by fertile internodes, without bracts or foliar whorls between them. The sporangiophores are bifurcated at least once, non-peltate, with terminal clavate sporangia, densely but loosely arranged on the main axes, occurring in the middle to upper portion of the internodes. The natural new taxon, as reconstituted, lived in transitional environments that were exposed for relatively short periods, when the vegetation became established. These marginal areas were occasionally flooded and covered with large amounts of sediment that buried part or all of the community; when the water naturally receded, the plant individuals would have recolonized these marginal areas, probably using their continuously growing root systems for vegetative reproduction. In evolutionary terms, the group that includes Paragiridia and closely similar forms must have descended directly from Carboniferous Archaeocalamitaceae, in view of their simplified structure and lack of a pelta on their sporangiophores. Therefore, they probably represent a separate sphenopsid lineage, which evolved toward the development of a peltate sporangiophore organized in strobili. [ABSTRACT FROM AUTHOR]

In this study we investigated the morphology of three oligotrich (s.l.) ciliates, Strombidium guangdongense sp. nov., Cyrtostrombidium paralongisomum Tsai et al., 2015 and Strombidinopsis sinicum sp. nov. Strombidium guangdongense sp. nov. is characterized by its elongate obconical to obovoidal body shape and widely spaced dikinetids in the girdle and ventral kineties. Another new species, Strombidinopsis sinicum sp. nov. is diagnosed by its small size and semi-globular body shape without mineral envelopes. Some additional morphological data of the recently described species Cyrtostrombidium paralongisomum Tsai et al., 2015, such as the endoral membrane, are supplied based on our population. We also analysed the molecular phylogeny of each species based on small subunit rRNA (SSU rRNA) gene sequence data. The monophyly of Cyrtostrombidium is supported by our phylogenetic analyses, but the monophyly of Strombidinopsis and of the family Strombidinopsidae are both rejected by AU tests. In addition, Strombidium species have a tail branch separately from one another in phylogenetic trees, whereas strombidiids with a pigment spot group together, suggesting the latter character is a synapomorphy for this group of strombidiids. http://zoobank.org/urn:lsid:zoobank.org:act:35FE2AFD-A582-4885-BD01-48901E4C76C4 http://zoobank.org/urn:lsid:zoobank.org:act:E9D4A497-DAD6-4AA0-A044-A5A1D2C1A057 [ABSTRACT FROM AUTHOR]

To reveal the structural composition and temporal variation of the ciliate community on a long-term scale, the species composition, abundance and carbon biomass, as well as interactions with environmental factors, were investigated combining the data from two monitoring programs at Helgoland Roads. A total of 89 ciliate taxa representing 46 different genera were identified during the monitoring periods. The ciliate community was dominated by aloricate oligotrichs and the photosynthesis-performing ciliates Mesodinium rubrum and Mesodinium major in terms of abundance and carbon biomass and exhibited clear seasonal patterns, with high values in spring and summer and low values in autumn and winter and a distinct peak in June mainly due to the bloom of M. rubrum and M . major . Univariate correlation analyses were conducted using the ciliate data from two monitoring programs and the environmental parameters from the Helgoland Roads long-term date set. The results showed that the ciliate community was positively correlated with water temperature and Chlorophyll a and negatively correlated with various inorganic nutrients, and was strongly influenced by the food availability. Multivariate analyses revealed that the ciliate community exhibited not only seasonal variation at a short-term scale but also annual variation at a long-term scale in terms of community structure, dominant species and influencing factors. The results from both univariate and multivariate analyses indicate that water temperature and various inorganic nutrients might not directly control the temporal dynamics of the ciliate community but indirectly influence it via the food availability. This study is the first detailed investigation on the ciliate community in the North Sea regarding the structural composition and temporal variation in relation to environmental factors. Our findings suggest that long-term monitoring programs on the ciliate community as a crucial food web component are essential. [ABSTRACT FROM AUTHOR]

Oligotrich ciliates are common marine microplankters, but their biodiversity and evolutionary relationships have not been well-documented. Morphological descriptions and small subunit rRNA gene sequences of two new species representing two new strombidiid genera, Sinistrostrombidium cupiformum gen. nov., sp. nov. and Antestrombidium agathae gen. nov., sp. nov. are presented, and their taxonomy and molecular phylogeny are analyzed. Sinistrostrombidium gen. nov. is characterized by a sinistrally spiraled girdle kinety and a longitudinal ventral kinety. Antestrombidium gen. nov. is distinguished by tripartite somatic kineties (circular and ventral kineties plus dextrally spiraled girdle kinety). Sinistrostrombidium and Antestrombidium branched separately from one another in phylogenetic trees, clustering with different clades of strombidiids. The new genera added to the diversities of ciliary patterns and small subunit rRNA gene sequences in strombidiids leads to presentation of a new hypothesis about evolution of the 12 known strombidiid genera, based on ciliary pattern and partly supported by molecular evidence. In addition, our new morphological and molecular analyses support establishment of a new order Lynnellida ord. nov., characterized by an open adoral zone of membranelles without differentiation of anterior and ventral membranelles, for Lynnella, but we remain unable to assign the genus to a subclass with confidence. [ABSTRACT FROM AUTHOR]

The Middle to Late Miocene mixed carbonate-siliciclastic coastal wedge of the Pietra di Finale, unconformably overlying the Ligurian Alps succession, displays a carbonate portion dominated by Halimeda and Porites fragments that fall in the photozoan assemblages. Photozoan assemblages typically develop under tropical and oligotrophic conditions, while hetorozoan assemblages tend to thrive in high-nutrient settings. The Pietra di Finale Formation shows, however, that high weathering and an increase of nutrient inputs related to Alpine uplift and humid climatic conditions promoted Halimeda over the seagrass carbonate factory in the photic zone. The successful Halimeda proliferation was due to its efficient competition for nutrients, especially nitrogen. Thus, the Pietra di Finale Formation represents an interesting, counter-intuitive example in which increased nutrient concentrations promoted, instead of inhibited, a photozoan over a seagrass-related heterozoan carbonate production. [ABSTRACT FROM AUTHOR]

The oligotrichid ciliate Strombidium coronatum (Leegaard, 1915) Kahl, 1932 is redescribed from plankton samples taken in the Irish Sea, using live observation, protargol impregnation, and scannin electron microscopy. The species is characterized by a conspicuous, uniquelly shaped peristome, which is flat and roughly triangular and extends in the sagittal plane. The Irish Sea specimens measure ~ 45 × 25 µm in vivo and ~ 40 × 24 µm after protargol impregnation. The girdle kinety is equatorial, ostensibly continuous, and composed of ~ 100 dikinetids. The ventral kinety extends longitudinally on the posterior fifth of the cell and is composed of about five dikinetids. Theadoralzone of membranelles is widely open and composed of ~ 18 collar and ~ 12 buccal membranelles; the collar portion is disconnected from the buccal portion. The shape and orientation of theopisthe'sadoral zone of membranelles are apparently extraordinary, i.e., the membranelles form an inverted L-shaped stripe extending longitudinally in the elongated posterior cell portion of dividers. [ABSTRACT FROM AUTHOR]

Studying non-model organisms is crucial in the context of the current development of genomics and transcriptomics for both physiological experimentation and environmental characterization. We investigated the transcriptomes of two marine planktonic ciliates, the mixotrophic oligotrich Strombidium rassoulzadegani and the heterotrophic choreotrich Strombidinopsis sp., and their respective algal food using Illumina RNAseq. Our aim was to characterize the transcriptomes of these contrasting ciliates and to identify genes potentially involved in mixotrophy. We detected approximately 10,000 and 7,600 amino acid sequences for S. rassoulzadegani and Strombidinopsis sp., respectively. About half of these transcripts had significant BLASTP hits (E-value <10−6) against previously-characterized sequences, mostly from the model ciliate Oxytricha trifallax. Transcriptomes from both the mixotroph and the heterotroph species provided similar annotations for GO terms and KEGG pathways. Most of the identified genes were related to housekeeping activity and pathways such as the metabolism of carbohydrates, lipids, amino acids, nucleotides, and vitamins. Although S. rassoulzadegani can keep and use chloroplasts from its prey, we did not find genes clearly linked to chloroplast maintenance and functioning in the transcriptome of this ciliate. While chloroplasts are known sources of reactive oxygen species (ROS), we found the same complement of antioxidant pathways in both ciliates, except for one enzyme possibly linked to ascorbic acid recycling found exclusively in the mixotroph. Contrary to our expectations, we did not find qualitative differences in genes potentially related to mixotrophy. However, these transcriptomes will help to establish a basis for the evaluation of differential gene expression in oligotrichs and choreotrichs and experimental investigation of the costs and benefits of mixotrophy. [ABSTRACT FROM AUTHOR]

Surface water samples were collected from 19 sites in the northern Beibu Gulf in April 2011. Species composition and abundance of planktonic ciliates were investigated. They were combined with environmental data to obtain the spatial pattern of the ciliate community and its relationship with the environment. A total of 36 species belonging to 13 genera and 3 orders (Oligotrichida, Haptorida and Tintinnida) were identified, including 10 dominant species. All 19 samples were divided into three groups using cluster analysis and multidimensional scaling (MDS) on the basis of the ciliate species composition and abundance. Group 1 was the least abundant. The species of the order Oligotrichida dominated in Group 2. In contrast, Mesodinium species were of increased importance in Group 3. Redundancy analysis (RDA) revealed that ciliate communities were more closely related to the level of nitrogen (total nitrogen, nitrate nitrogen, nitrite nitrogen) and phosphorus (total phosphorus, active phosphorus) rather than other variables. As the levels of nitrogen and phosphorus increased, communities dominated by species from the order Oligotrichida were replaced by those dominated by Mesodinium species. [ABSTRACT FROM AUTHOR]

The copy number and sequence variation of the ribosomal DNA (rDNA) operon are of functional significance in evolution and ecology of organisms. However, the relationship between copy number and sequence variation of rDNA in protists has been rarely studied. Here we quantified rDNA copy numbers of oligotrich and peritrich ciliate species using single-cell quantitative PCR. We also examined the rDNA sequence variation by using single-cell PCR, cloning, and sequencing of multiple clones. We found that the rDNA copy numbers per cell were extremely high and different among even congeners, with the highest record of about 310,000. There was substantial intraindividual haplotype diversity and nucleotide diversity for the rDNA markers, with sequence differences primarily characterized by single nucleotide polymorphisms. Haplotype and nucleotide diversity was positively correlated to the rDNA copy number. Our findings provide evidence that: (1) ciliates generally have much higher rDNA copy numbers than other protists and fungi, which could lead to overestimation of the relative abundance of ciliates in environmental samples when rDNA sequence-based methodologies are used; and that (2) the rDNA might not always evolve in a strictly concerted manner in ciliates, which may raise problems in rDNA-based inference of species richness and phylogeny. [Copyright &y& Elsevier]

Phylogenetic analyses have largely resolved generic and higher level relationships within the Polytrichopsida, enabling polarisation of characters and the identification of macro-evolutionary trends. Topologies show strong geographic patterning, with major groups having predominantly Northern or Southern Hemisphere distributions and some general morphologies having arisen independently on either side of the equator. While most cases of apparent convergence have been taxonomically visible due to sufficient higher-level characters being present to distinguish unrelated genera, convergent reduction may have resulted in conflation of similar gametophytic morphologies in classification. We present further evidence for the polyphyly of Oligotrichum DC. as currently circumscribed, showing how this morphology has probably arisen through reduction on multiple occasions to produce distinct lineages that have lacked taxonomic identity. We present a preliminary arrangement of the species currently recognised in Oligotrichum, accommodating selected Southern Hemisphere taxa in Itatiella G.L.Sm., and combining Atrichopsis compressa (Hook.f. & Wilson) G.L.Sm. and Oligotrichum tenuirostre (Hook.) A.Jaeger under Notoligotrichum G.L.Sm. For several species that clearly do not belong in Oligotrichum but remain of ambiguous affinity to other genera we avoid making new combinations, as ongoing combined molecular and morphological studies have considerable potential to elucidate their relationships in the near future. [ABSTRACT FROM AUTHOR]

The morphology and small subunit rRNA (SSrRNA) gene sequence of a marine oligotrich ciliate, Williophrya maedai gen. nov., sp. nov., are reported. The new genus Williophrya is characterized by the adoral zone with no differentiation of membranelles, and the reduced somatic ciliature which comprises a bipartite girdle kinety only. In addition, the in vivo morphologies of two other oligotrichs, namely Strombidium basimorphum Martin & Montagnes, 1993 and Pseudotontonia simplicidens (Lynn & Gilron, 1993) Agatha, 2004, are reported for the first time based on Chinese populations. Improved diagnoses of both species are supplied. The phylogenetic position of Williophrya maedai is investigated based on SSrRNA gene sequence data. These show that: (1) Williophrya maedai is most closely related to Strombidium purpureum and S. apolatum; (2) Williophrya is assigned to the family Strombidiidae although it has some unique morphological features regarding its oral and somatic ciliatures. [ABSTRACT FROM AUTHOR]

Abstract: The two recently established genera Apostrombidium and Varistrombidium and the analysis of ontogenetic data in Strombidium constrictum, S. montagnesi, S. wilberti, Omegastrombidium elegans, and Paratontonia gracillima necessitated a revision of the hypothesis about the somatic ciliary pattern evolution in oligotrichid ciliates. As a consequence, the species-rich genus Strombidium was split, establishing two genera for species with a horizontal girdle kinety posterior to the oral primordium: Opisthostrombidium nov. gen. with the extrusome attachment sites along the anterior margin of the girdle kinety and posterior to the oral primordium and Foissneridium nov. gen. with the extrusome attachment sites distinctly apart from the girdle kinety and anterior to the oral primordium. The ontogenetic data revealed that the Ω-shaped girdle kinety pattern evolved convergently from the Pseudotontonia pattern with its horizontal girdle kinety in the tailed genus Paratontonia and from the Novistrombidium pattern with its dextrally spiralled girdle kinety in the tailless genus Omegastrombidium. The somatic ciliary pattern of the latter genus probably gave rise to the patterns of Apostrombidium and Varistrombidium. [ABSTRACT FROM AUTHOR]

The Mediterranean Sea is one of the most oligotrophic marine areas on earth where nitrogen fixation has been formally believed to play an important role in carbon and nitrogen fluxes. Although this view is under debate, the diazotrophs responsible for this activity have still not been investigated in the open sea. In this study we characterised the surface distribution and species richness of unicellular and filamentous diazotrophs across the Mediterranean Sea by combining microscopic counts with size fractionated in situ hybridization (TSA-FISH), and 16S rDNA and nifH phylogenies. These genetic analyses were possible owning to the development of a new PCR protocol adapted for scarce microorganisms (0.2 cellml-1). Low concentrations of diazotrophic cyanobacteria were detected and this community was dominated at 99.9% by picoplankton hybridized with Nitro821 probe, specific for unicellular diazotrophic cyanobacteria (UCYN). Among filamentous cyanobacteria only 0.02 filament ml-1 of Richelia were detected in the eastern basin, while small (0.7-1.5 μm) and large (2.5-3.2 μm) Nitro821-targeted cells were recovered at all stations and averaged 3.5 cell ml-1. The affiliation of the small Nitro821-targeted cells to UCYN-A was confirmed by 16S and nifH phylogenies in the western Mediterranean Sea. Surprisingly, the larger hybridized cells were not belonging to UCYN-B and C but to plastids of picoeukaryote. NifH gene was not recovered among picoeukaryotes, when rhizobia sequences, including the ones of Bradyrhizobia, were dominating nifH clone libraries from picoplanktonic size fractions. Few sequences of-proteobacteria were also detected in central Mediterranean Sea. While low phosphate and iron concentrations could explain the absence of Trichodesmium sp., the factors that prevent the development of UCYN-B and C remain unknown. We also propose that the dominating picoplankters probably developed specific strategies, such as associations with protists or particles and photosynthetic activity to acquire carbon for sustaining diazotrophy. Among UCYN further work will be necessary to understand their suggested role in plastid evolution [ABSTRACT FROM AUTHOR]

The marine oligotrichous ciliate Spirotontonia taiwanica n. sp. isolated from the coastal waters of northeastern Taiwan is reported, using live observation, protargol preparations and molecular data. The new species differs from the most similar, known congener Spirotontonia turbinata in the following features: (1) lower number of buccal membranelles (11–13 vs. 13–17); (2) higher number of whorls of girdle kinety (2.5 vs. 1.5); (3) lower number of macronuclear nodules (20–31 vs. 28–40); (4) larger cell size (80–104 × 40–72 vs. 44–75 × 29–56 μm); (5) larger anterior cell end to buccal vertex (50 vs. 33 μm); (6) larger ratio of cell length to cell width (1.74 vs. 1.38); (7) the different beginning of the girdle kinety (posterior to the buccal vertex vs. left of the buccal zone portion); and (8) the disappearance of the L-shaped argyrophilic structures in the last half whorl and occasionally the first 1–10 dikinetids (i.e. yes vs. no). The molecular data also reveal two distinct species, deviating by 2% or 33% base pairs. [ABSTRACT FROM AUTHOR]

Elucidating the relationship between ciliate communities in the benthos and the plankton is critical to understanding ciliate diversity in marine systems. Although data for many lineages are sparse, at least some members of the dominant marine ciliate clades Oligotrichia and Choreotrichia can be found in both plankton and benthos, in the latter either as cysts or active forms. In this study, we developed a molecular approach to address the relationship between the diversity of ciliates in the plankton and those of the underlying benthos in the same locations. Samples from plankton and sediments were compared across three sites along the New England coast, and additional subsamples were analyzed to assess reproducibility of methods. We found that sediment and plankton subsamples differed in their robustness to repeated subsampling. Sediment subsamples (i.e., 1-g aliquots from a single ∼20-g sample) gave variable estimates of diversity, while plankton subsamples produced consistent results. These results indicate the need for additional study to determine the spatial scale over which diversity varies in marine sediments. Clustering of phylogenetic types indicates that benthic assemblages of oligotrichs and choreotrichs appear to be more like those from spatially remote benthic communities than the ciliate communities sampled in the water above them. [ABSTRACT FROM AUTHOR]

The morphology and infraciliature of two new marine oligotrich ciliates, Novistrombidium sinicum n. sp. and Novistrombidium orientale n. sp., isolated from a mangrove wetland near Guangzhou, southern China, were studied from live and protargol-stained specimens. Novistrombidium sinicum is different from its congeners by the combination of the following characters: three posteriorly directed thigmotactic membranelles, one ellipsoidal macronucleus, the extrusomes equidistantly arranged, and the ventral kinety commencing below the right end of the girdle kinety. The small-sized N. orientale can be separated from its congeners by two posteriorly directed thigmotactic membranelles, one ellipsoidal macronucleus, the extrusomes equidistantly arranged, and the ventral kinety commencing below the right end of the girdle kinety. [ABSTRACT FROM AUTHOR]

Bacterial community compositions (BCC) associated with the cladoceran Bosmina coregoni and the cyclopoid copepod Thermocyclops oithonoides in oligotrophic Lake Stechlin versus eutrophic Lake Dagow (northeastern Germany) were compared using molecular techniques. We also transplanted the zooplankton from their native lake to the other lake, and studied changes in their associated BCC as a result of the modified ambient environment. Bacterial community composition associated with B. coregoni was quite conservative between the oligotrophic and eutrophic lakes, and most of the bacteria belonged to Alpha- and Betaproteobacteria. In contrast, BCC associated with T. oithonoides was highly variable and dependent on the environment, and Betaproteobacteria and Bacteroidetes were the most represented among the bacteria. Thermocyclops oithonoides from the oligotrophic lake was more able to retain its bacteria after being transplanted to the eutrophic lake than vice versa. This suggests that bacteria in oligotrophic water were more firmly attached to the copepod and better in resisting environmental fluctuations than those in eutrophic water. [ABSTRACT FROM AUTHOR]

Nutrient input in streams alters the density and species composition of attached algal communities in open systems. However, in forested streams, the light reaching the streambed (rather than the local nutrient levels) may limit the growth of these communities. A nutrient-enrichment experiment in a forested oligotrophic stream was performed to test the hypothesis that nutrient addition has only minor effects on the community composition of attached algae and cyanobacteria under light limitation. Moderate nutrient addition consisted of increasing basal phosphorus (P) concentrations 3-fold and basal nitrogen (N) concentrations 2-fold. Two upstream control reaches were compared to a downstream reach before and after nutrient addition. Nutrients were added continuously to the downstream reach for 1 year. Algal biofilms growing on ceramic tiles were sampled and identified for more than a year before nutrient addition to 12 months after. Diatoms were the most abundant taxonomic group in the three stream reaches. Nutrient enrichment caused significant variations in the composition of the diatom community. While some taxa showed significant decreases (e.g., Achnanthes minutissima, Gomphonema angustum), increases for other taxa (such as Rhoicosphenia abbreviata and Amphora ovalis) were detected in the enriched reach (for taxonomic authors, see Table 2 ) . Epiphytic and adnate taxa of large size were enhanced, particularly during periods of favorable growth conditions (spring). Nutrients also caused a change in the algal chl a, which increased from 0.5–5.8 to 2.1–10.7 μg chl · cm−2. Our results indicate that in oligotrophic forested streams, long-term nutrient addition has significant effects on the algal biomass and community composition, which are detectable despite the low light availability caused by the tree canopy. Low light availability moderates but does not detain the long-term tendency toward a nutrient-tolerant community. Furthermore, the effects of nutrient addition on the algal community occur in spite of seasonal variations in light, water flow, and water chemical characteristics, which may confound the observations. [ABSTRACT FROM AUTHOR]

Abstract: So far, neither morphology nor gene sequences have provided a reliable classification of halteriid and hypotrichid spirotrichs. Thus, we performed a comparative study on the fine structure of the resting cysts in some representative species, viz., the oligotrichs Halteria grandinella and Pelagostrombidium fallax and the oxytrichid hypotrichs Laurentiella strenua, Steinia sphagnicola, and Oxytricha granulifera. Main results include: (i) there are three different, very likely non-homologous cyst surface ornamentations, viz., spines (generated by the ectocyst), thorns (generated by the mesocyst), and lepidosomes (produced in the cytoplasm); (ii) Halteria has a perilemma; (iii) Halteria, Meseres and Pelagostrombidium have fibrous lepidosomes, while those of Oxytricha are tubular; (iv) the cyst wall structure of Pelagostrombidium and Strombidium is distinctly different from that of halteriids and oxytrichids, which are rather similar in this respect; (v) cyst ornamentation does not provide a reliable phylogenetic signal in oxytrichid hypotrichs because ectocyst spines occur in both flexible and rigid genera. The new observations and literature data were used to investigate the phylogeny of the core Spirotrichea. The Hennigian argumentation scheme and computer algorithms showed that the spirotrichs are bound together by the macronuclear reorganization band, the subepiplasmic microtubule basket, and the apokinetal stomatogenesis. The Hypotrichida and Oligotrichida are united by a very strong synapomorphy, viz., the perilemma, not found in any other member of the phylum. Halteriid and oligotrichid spirotrichs form a sister group supported by as many as 13 apomorphies. Thus, the molecular data, which classify the halteriids within the core hypotrichs, need to be reconsidered. [Copyright &y& Elsevier]

Dilution experiments were performed to examine the growth and grazing mortality rates of picophytoplankton (<2 μm), nanophytoplankton (2–20 μm), and microphytoplankton (>20 μm) at stations in the Chesapeake Bay (CB), the Delaware Inland Bays (DIB) and the Delaware Bay (DB), in early spring 2005. At station CB microphytoplankton, including chain-forming diatoms were dominant, and the microzooplankton assemblage was mainly composed of the tintinnid Tintinnopsis beroidea. At station DIB, the dominant species were microphytoplanktonic dinoflagellates, while the microzooplankton community was mainly composed of copepod nauplii and the oligotrich ciliate Strombidium sp. At station DB, nanophytoplankton were dominant components, and Strombidium and Tintinnopsis beroidea were the co-dominant microzooplankton. The growth rate and grazing mortality rate were 0.13–3.43 and 0.09–1.92 d−1 for the different size fractionated phytoplankton. The microzooplankton ingested 73, 171, and 49% of standing stocks, and 95, 70, and 48% of potential primary productivity for total phytoplankton at station CB, DIB, and DB respectively. The carbon flux for total phytoplankton consumed by microzooplankton was 1224.11, 100.76, and 85.85 μg C l−1 d−1 at station CB, DIB, and DB, respectively. According to the grazing mortality rate, carbon consumption rate and carbon flux turn over rates, microzooplankton in study area mostly preferred to graze on picophytoplankton, which was faster growing but was lowest biomass component of the phytoplankton. The faster grazing on Fast-Growing-Low-Biomass (FGLB) phenomenon in coastal regions is explained as a resource partitioning strategy. This quite likely argues that although microzooplankton grazes strongly on phytoplankton in these regions, these microzooplankton grazers are passive. [ABSTRACT FROM AUTHOR]

The distribution of ciliate plankton was compared between inner and outer areas of a harbor divided by an artificial breakwater in Kuryongpo, on the eastern coast of Korea, from February 2001 to October 2003. Less dissolved oxygen and higher concentrations of nitrogenous nutrients and phosphate were observed in the inner area. The abundance of oligotrich ciliates peaked in February 2001, when nanoflagellates bloomed in the inner area. The photosynthetic ciliate Mesodinium rubrum showed differing population dynamics annually, with blooming peaks in October 2001 in the inner area and in February 2003 in the outer area. The tintinnid species Tintinnopsis beroidea and Helicostomella subulata were generally more abundant in the outer area. Total ciliates were significantly related to oligotrich abundance in the inner area, and to tintinnid abundances in the outer area. Ciliate distribution showed quantitative and qualitative differences between the inner and outer areas in connection with the distribution of other plankton communities: oligotrich ciliate abundance increased with nanoflagellate blooms; dominance of M. rubrum was consistent with blooming of micro-sized phytoplankton (diatoms and dinoflagellates); large-sized tintinnids concurred with small dinoflagellates; and ciliate abundances decreased with mesozooplankton increases. The results indicate that the breakwater induces eutrophication in the inner area and provides suitable conditions for nanoflagellate blooms, which serially trigger opportunistic increases in oligotrich ciliates. [Copyright &y& Elsevier]

Abstract: The morphology and infraciliature of two marine planktonic ciliates, Parastrombidium faurei (Kahl, 1932) Maeda, 1986 and Strombidium capitatum (Leegaard, 1915) Kahl, 1932, from coastal waters near Qingdao (Tsingtao), northern China, were investigated based on live observation and protargol impregnation. This is the first time that these two species are reported from Yellow Sea/North Pacific. Emended diagnoses for the genus Parastrombidium and its single species P. faurei are provided as they were not studied with modern methods before. The ciliary pattern and the stomatogenesis of Parastrombidium indicate that it belongs to the order Choreotrichida Small and Lynn, 1985, family Strombidinopsidae Small and Lynn, 1985. An updated description for the “well-known”Strombidium capitatum is also included based on the Qingdao population. [Copyright &y& Elsevier]

Morphological and molecular attributes of four species of Cecidomyiidae that induce galls on junipers, Juniperus spp., in Britain and Japan were used to redefine the genus Oligotrophus Latreille, which now includes Arceuthomyia Kieffer and Schmidtiella Rübsaamen (new synonyms). Illustrated morphological descriptions are provided for the four species Oligotrophus juniperinus (Linnaeus), Oligotrophus panteli Kieffer, Oligotrophus gemmarum (Rübsaamen) (new combination) and Oligotrophus nezu Kikuti (= Arceuthomyia nakaharai Inouye (new synonymy)) and phylogenies based on partial sequencing of the mitochondrial 12S rRNA gene are reported. [ABSTRACT FROM AUTHOR]

Two new marine oligotrich ciliates, Parallelostrombidium paralatum nov. sp. and Strombidium montagnesi nov. sp., were isolated from the littoral area of Qingdao (Tsingtao), China. The morphology and infraciliature of each was studied using live observation and protargol impregnation. Based on the Qingdao population, the diagnosis for P. paralatum is given: marine Parallelostrombidium, in vivo about 70×60 µm; dorsoventrally flattened ca 2:3; cell ellipsoidal in outline with conspicuous apical protrusion; on average 27 anterior and 17 ventral membranelles; two posteriorly directed thigmotactic membranelles; macronucleus broadly ellipsoidal; extrusomes ca 10 µm long, arranged along equatorial area; girdle and ventral kineties with 71–99 and 32–42 dikinetids, respectively. Strombidium montagnesi nov. sp. is characterized thus: small marine Strombidium ∼30×20 µm in vivo with truncated conical cell shape and conspicuous equatorial ridge; hemitheca covering the posterior one‐quarter to one‐third of the cell; dorsoventrally flattened ca 2:3; about 21 anterior membranelles and six ventral membranelles; girdle kinety located in posterior one‐quarter to one‐third of the cell and has 25–27 dikinetids, while ventral kinety has 6–12 dikinetids; extrusomes ca 5 µm long, arranged along girdle kinety; single ellipsoidal macronucleus centrally positioned. [ABSTRACT FROM AUTHOR]

Cell volume, growth and production rates of two common planktonic freshwater ciliates, the prostomatid Coleps spetai and the oligotrich Rimostrombidium lacustris, were investigated in clonal laboratory cultures. The clones were isolated from oligo-mesotrophic alpine Lake Mondsee, Austria, during summer and kept in culture with the small cryptophyte Cryptomonas sp. as food. All parameters investigated revealed significant clonal differences among both species. The extent of the clonal differences was comparable to differences observed earlier between similar planktonic ciliate species. The ecological relevance of varying clonal growth rates was evaluated using a simple numerical model. The model outcome suggests that differences in growth rates by 10% may significantly alter the clonal composition in the course of a ciliate peak in temperate lakes. The experimental results and the model outcome are discussed in the context of the functional diversity of freshwater ciliates. It is concluded that the morphospecies concept, which is the most widely used concept by both ciliate taxonomists and ecologists, may severely underestimate the ecological plasticity and the functional diversity of aquatic ciliates. [ABSTRACT FROM AUTHOR]

Abstract: Morphological data from life, protargol impregnation, and scanning electron microscopy were combined with genetic data not only to describe the marine plankton ciliates Pelagostrobilidium neptuni (Montagnes and Taylor, 1994) Petz, Song, and Wilbert, 1995 and Strombidium biarmatum nov. spec., but also to elucidate their phylogenetic relationships. Additionally, the ontogenesis of P. neptuni was studied and the diagnosis of the genus Pelagostrobilidium was improved due to further data from the newly affiliated species P. epacrum (Lynn and Montagnes, 1988) nov. comb. (basionym: Strobilidium epacrum Lynn and Montagnes, 1988). The phylogenetic analysis of the small subunit ribosomal RNA genes matched the morphologic and ontogenetic assigning of P. neptuni to the choreotrichid family Strobilidiidae. The considerable genetic distance of between P. neptuni and Strobilidium caudatum corroborated the morphological differences and thus the maintenance of the genus Pelagostrobilidium. Strombidium biarmatum nov. spec. is a typical member of the genus, except for the two types of extrusomes (“trichites”): ∼12×0.5μm, needle-shaped ones attached anterior to the girdle kinety and ∼6×0.5μm, rod-shaped ones at the distal end of the intermembranellar ridges. Its flask-shaped resting cysts have several strong spines. In accordance with the morphologic data, S. biarmatum is placed within the order Oligotrichida by gene sequence analysis. The great genetic distances within the oligotrichids support the diversity found in morphologic and ontogenetic studies. [Copyright &y& Elsevier]

The morphology and ciliary pattern of a new marine oligotrichous ciliate, Strombidium wilberti nov. spec., collected from the littoral area off Qingdao, North China, are described from live observations and after protargol impregnation. This new species is characterized by: about 45-60×35-50 µ m in vivo with truncated obconical body shape and conspicuous distended cell surface which covers the posterior half of the cell; buccal cavity extending posteriorly to about one-third of body length; about eight buccal and 15 collar membranelles; girdle kinety completely closed, consisting of ca 60 dikinetids; ventral kinety conspicuously long with about 30 densely packed dikinetids, which extends anteriorly to girdle area; extrusomes about 20 µ m long, grouped in rows and arranged anterior to girdle kinety; single globular macronucleus. Related nominal congeners are compared and discussed. The Antarctic morphotype described by Petz et al. (1995) as Strombidium emergens ( Leegaard, 1915 ) Kahl, 1932 is not conspecific with the original form and is hence recognized as a new member of this genus, Strombidium petzi nov. spec. The diagnosis for this new organism: large marine Strombidium ca 95-110×60-65 µ m in vivo with elongate elliptical body shape and conspicuously shallow oral cavity. Girdle kinety continuous on ventral side with ca 100 dikinetids; ventral kinety extending from posterior area almost to girdle kinety, consisting of more than 20 dikinetids; four to five buccal and 14-15 collar membranelles. Macronucleus oval in shape; one subequatorial girdle of extrusomes. [ABSTRACT FROM AUTHOR]

Discusses an improved description of Strombidium sulcatum. Definition of strombidium sulcatum; Prominent protuberance in stained specimens; Type materials for strombidium sulcatum.

Morphogenesis and nuclear events during conjugation have been investigated for the aloricate oligotrich Pelagostrobilidium sp. using cytological staining methods. While several similarities between Pelagostrobilidium and sister groups (hypotrichs and stichotrichs) reported previously were recognized in the preconjugation behaviour, conjugation type and general nuclear division patterns, significant differences were found between them in the behaviour of oral and somatic ciliatures. In Pelagostrobilidium there was no reorganization in the somatic kineties during conjugation, in addition, it showed a very simple pattern of reorganization in the oral ciliature, which was very similar to stomatogenesis in asexual reproduction. A replacement oral apparatus was completed during the conjugation process and it very quickly replaced the old adoral zone when the conjugants separated. A noteworthy fact is that most of the parental adoral membranelles of Pelagostrobilidium persisted and were active during the entire conjugation period in spite of the loss of functional feeding organelles such as the cytostome and paroral membrane. The need to retain locomotion throughout the entire life cycle might be one of the adaptive features of oligotrichs required to occupy a certain niche in oceanic waters. The relatively short duration of the conjugation process (5.6 h) of Pelagostrobilidium is also likely to be important for life in oceanic waters. [Copyright &y& Elsevier]

Oligotrich ciliates are an abundant and important component of planktonic food webs. Classified together, based on morphology and the arrangement of the oral ciliature, they include sensu lato halteriids, strombidiids, strobilidiids, and tintinnids. The oral ciliature of tintinnids and strobilidiids, the subclass Choreotrichia, is composed of a closed circle of external polykinetids with internal polykinetids, leading to the cytostome. Strombidiid and halteriid species, the subclass Oligotrichia, have an open circle of adoral polykinetids and separate ventral polykinetids. Previous molecular phylogenetic analyses of spirotrichs have placed Halteria grandinella among the stichotrichs. Apart from H. grandinella, only one other small subunit ribosomal RNA (SSrRNA) gene sequence of an oligotrich ciliate (Strombidium purpureum) has been published. Fourteen additional species representative of the major oligotrich orders were collected to determine their phylogenetic relationships. These SSrRNA gene sequences include two strombidiids (Strombidium spp.), one strobilidiid (Strobilidium caudatum), and 11 tintinnid species (i.e. Codonellopsis americana, Eutintinnus pectinis, Eutintinnus sp., Favella panamensis, Metacylis angulata, Metacylis sp., Rhabdonella hebe, Tintinnidium mucicola, Tintinnopsis dadayi, Tintinnopsis fimbriata and Tintinnopsis tocatinensis). The subclasses Oligotrichia (excluding Halteria) and Choreotrichia form a monophyletic group and are sister group to the subclass Stichotrichia with high nodal support. The choreotrichs are confirmed as a monophyletic subclass whereas the halteriids do not cluster with the strombidiids, but within the subclass Stichotrichia. Therefore, the family Halteriidae is transferred to the order Sporadotrichida in the subclass Stichotrichia. The strombidiids form a sister clade to the subclass Choreotrichia. Since there are no clear morphological or genetical synapomorphies for these two groups combined, the separate subclasses Choreotrichia and Oligotrichia are retained. The genetic relationships among tintinnid genera do not correspond to relationships based on lorica morphology: species with agglomerated and hyaline loricae do not form separate branches but are interrelated. [ABSTRACT FROM AUTHOR]

Variations in the spatial and temporal distribution of oligotrich ciliate populations in the East China Sea were investigated during four cruises of the R/V Ocean Researcher I between December 1997 and October 1998. Over the entire continental shelf, a seasonal cycle was found with a distinct 3–5-fold increase in the abundance of oligotrich ciliates in summer. This increase appeared to be induced by the tremendous summertime runoff from the Changjiang. A radial-type spatial distribution pattern also was observed in summer, with population densities higher toward the Changjiang plume but highest of all in the margins of the plume. In spring and fall, the spatial distribution of the oligotrich ciliates was closely correlated to the abundance of cyanobacterium Synechococcus. In summer in the plume region, mixotrophic ciliates accounted for over 50% of the total ciliate population, compared to less than 30% outside the plume or that in other seasons. We propose a model in which these ciliates constitute part of the pathway through which the particulate and dissolved organic carbon in the runoff water is incorporated into the oceanic food web. [Copyright &y& Elsevier]

We analysed early spring protozooplankton peaks following winter stratification in two different basins (northeast, NE; southwest, SW) of an artificially-divided bog lake Große Fuchskuhle(Brandenburg, Germany). The maximum ciliate biomass and numbers (660 and 990 μg l–1 of organic carbon, and 290 and 260 cells ml–1 in NE and SW, respectively) were reached in the surface layer during the ice melting and then continuously decreased. The surface layers were numerically dominated by species of the genus Urotricha, while in the ciliate biomass during the first part of the study, a mixotrophic oligotrich, Pelagostrombidium mirabile prevailed (Corg up to 940 μg l–1). We observed a conspicuous ciliate peak that could not be related to the feeding activity of the dominant ciliate species upon picoplankton. Seemingly, the peak was related to the specific conditions resulting from the ice melting where these ciliates could be concentrated. Additionally, the mixotrophy of oligo-trichous species allowed them to penetrate below the oxycline, although feeding on nanoplankton such as flagellates was also very likely. Our direct measurements of uptake rates of bacteria showed that the abundant strombidiids were not nutritionally dependent on bacterivory. However, the ciliate uptake rate (up to 670 bacteria ciliate–1 h–1) contributed significantly to the overall bacteria mortality rate. The maximum (community average) cell-specific ciliate feeding rate of over 200 bacteria ciliates–1 h–1 was reached, along with an increasing contribution of scuticociliates, paralleled by a drop in large oligotrichs. [ABSTRACT FROM PUBLISHER]

1. Oligotrich ciliates are an important part of most marine plankton communities. Mixotrophic (chloroplast-sequestering) oligotrichs, a common component of marine oligotrich communities, obtain fixed carbon from both photosynthesis as well as the ingestion of particulate food. Mixotrophy, in general, is often considered an adaptation permitting exploitation of food-poor environments. We examined the hypothesis that, among oligotrichs, mixotrophs may be at a disadvantage relative to heterotrophs in food-rich conditions in a nutrient-enrichment experiment. We compared growth responses of mixotrophic and heterotrophic oligotrichs in natural communities from the N.W. Mediterranean Sea in microcosms with daily nutrient additions resulting in increases in nanoflagellates and Synechococcus populations. The results indicated that both mixotrophic and heterotrophic oligotrichs respond to prey increases with rapid growth (μ=1.2 d-1). 2. To examine the hypothesis that the proportion of mixotrophic to heterotrophic oligotrichs changes with the trophic status of a system, increasing with oligotrophy, we examined data from a variety of marine systems. Across systems ranging in chlorophyll concentration from about 0.1 to 40 μg L-1, oligotrich cell concentrations are correlated with chlorophyll concentrations, and mixotrophs are a consistent component of oligotrich communities, averaging about 30% of oligotrich cell numbers. 3. We discuss the costs, benefits and possible uses of mixotrophy in marine oligotrichs and suggest that mixotrophy in marine oligotrichs is not closely linked to the exploitation of food-poor environments, but probably serves a variety of purposes. [ABSTRACT FROM AUTHOR]

Two oligotrophic systems of different origin (one originating from the Atlantic flow, the other a typical Mediterranean one) and a frontal system were occurring in the Algerian Basin during June 1990. The copepod communities and their diversity in the epipelagic layer were closely related to these different environments. Furthermore, in this area a great number of Atlantic species of copepods have been caught, as well as 9 deep water species. In the coastal system where the modified Atlantic Water is flowing, the number of copepod species is varying from station to station, depending on mixing and turbulence processes as cyclonic and anticyclonic eddies inducing coastal upwelling (station 5) and leading to a low species diversity index as well as a low evenness, indicating a disturbed environment. In the frontal system, the main characteristic is a high density of copepods dominated by a single species, Paracalanus parvus, the low species diversity index and a very low evenness indicating an instable environment, as testified by an enhanced production and by physical-chemical gradients. In the open Mediterranean sea area where mixing and turbulence are absent, the copepod community revealed a well-diversified species composition with a high species diversity index; the relationship with the highest evenness values suggests that this community is in the stage of maturity, with dominant species of similar abundance, and that the environment is stable. Deux systemes oligotrophes d'origine differente (l'un de l'Atlantique, l'autre typiquement mediterraneen) et un systeme frontal etaient presents dans le Bassin algerien en juin 1990. Les communautes de copepodes et la diversite dans la couche epipelagique sont en relation etroite avec ces differents environnements. De plus, dans cette zone, un grand nombre d'especes de copepodes de l'Atlantique ont ete prises, ainsi que 9 especes d'eau profonde. Dans le systeme cotier ou circule l'Eau Atlantique modifiee, la densite des especes de copepodes varie d'une station a l'autre, en fonction des processus de melange et de turbulences, tels que les tourbillons cycloniques et anticycloniques induisant des upwellings cotiers et conduisant a un faible indice de diversite specifique, comme a une faible regularite [''evenness''] denotant un environnement perturbe. Dans le systeme frontal, la principale caracteristique est une haute densite des especes de copepodes, avec une seule espece dominante, Paracalanus parvus, le faible indice de diversite specifique et une tres faible regularite denotant un environnement instable, ceci mis en evidence par une production elevee et par les gradients physico-chimiques. Dans la zone de Mediterranee aux eaux ouvertes, ou melange et turbulences sont absents, la communaute de copepodes a montre une composition specifique bien diversifiee, avec un indice de diversite specifique eleve; la relation avec les plus hautes valeurs de regularite suggere que la communaute est au stade de maturite, avec les especes dominantes d'abondance similaire, et que l'environnement est stable. [ABSTRACT FROM AUTHOR]

The impact of a cyclopoid copepod population on the protozoa community (two ciliate categories and Cryptomonas) was assessed weekly during the spring cohort of Cyclops vicinus (one month duration) in hypereutrophic Lake Søbygård by in situ gradient experiments with manipulation of ambient zooplankton abundance. As C.vicinus always made up >92% of the zooplankton biomass, the response of protozoa is assumed to be a result of predation by the copepod. Significant effects of copepod biomass on protozoa net population growth rates were obtained in the four experiments. Copepod clearance rates were significantly higher on oligotrichs than on prostomatids and Cryptomonas but declined for all three protozoa categories during the first three weeks of the copepod cohort, probably because of the change in developmental instar composition of the copepod population. Grazing impact on protozoa at ambient copepod abundance was considerable (range, 0.05–0.87 day–1) and could, together with the estimated reproductive potential of protozoans (range, –0.20–0.87 day–1), account for the decline in abundance and biomass of protozoa during the cohort development. Carbon flow from the protozoa to C.vicinus (range, 2.8–23.5 μg C l–1 day–1) documents the presence of a trophic link between protozoa and the spring cohort of C.vicinus in Lake Søbygård. [ABSTRACT FROM PUBLISHER]

Determines the carbon content and rate of dark respiration on individual oligotrich ciliates. Greater mortality rate for small cells; Factors behind the considerable variance in carbon-specific respiration; Absence of significant starvation-induced reduction in carbon-specific rates.

Sediment traps were deployed in a 60 m water column near the Eddystone Lighthouse on the south west coast of England for one year from March 1984. In April, the traps collected the cysts of a planktonic ciliate with a flux of almost 35 000 m d. The cysts were attributed to a planktonic oligotrich [provisionally identified as Strombidium crassulum (Leegard) Kahl], which was common in the water at the time. Identification was achieved through the discovery of the incipient formation of the cysts in preserved water samples and by the similarity of the morphology of the cysts with that of other oligotrichid ciliates. Attempts to prove the relationship by incubation have so far failed. The production of the cysts followed the main spring bloom of diatoms and coincided with a small bloom of autotrophic oligotrichs. In the traps, the total number and percentage of cysts with contents decreased rapidly after the encystment event. However, potentially viable cysts were still recorded in the plankton eleven months later, with minimum fluxes of 200 cysts m d. Resuspension of bottom sediments by tides and storms ensured that a large population of cysts was always present in the water column during the winter, awaiting the right conditions to stimulate excystment and the initiation of a new motile population. [ABSTRACT FROM AUTHOR]

The sinking rates in two size fractions of natural phytoplankton were measured over much of the photic zone in a subtropical environment. At 24, 40 and 71 m, sinking rates (± SD) of the 3 to 20 μm fractions were 0.72±0.05, 0.83±0.05, and 0.34±0.04 m · d, respectively, and rates for the 20 to 102 μm fraction were 1.50±0.21, 1.65±0.14, and 0.95±0.22 m · d, respectively. At all depths sampled, the 20 to 102 μm size fraction was observed to sink significantly (P<0.01) faster than the 3 to 20 μm fraction. considering vertical variability, both size fractions were observed to have significantly (P<0.01) lower sinking rates at 71 m than at more shallow depths. The finding of lower sinking rates in the region which lies just above the subsurface chlorophyll maximum provides empirical support for the hypothesis that variations in phytoplankton buoyancy may be related to the maintenance of this feature which is typical in oceanic environments. Analysis of sinking rate traces describes the distributions of specific sinking velocities for each size fraction and their variation. [ABSTRACT FROM AUTHOR]