Genetic diversity of eukaryotic ultraphytoplankton in the Gulf of Naples during an annual cycle

Eukaryotic ultraphytoplankton (<5 μm) are an important component of phytoplankton populations, Dot blot hybridisation analysis using class level 16S rRNA gene probes as well as clone libraries were used to investigate the diversity of these ultraphytoplankton during a 15 mo period (2003 to 2004) in the Gulf of Naples. Hybridisation data showed the presence of 3 main classes, Cryptophyceae, Chrysophyceae and Prymnesiophyceae, along with lower signals from the Pelagophyceae. Clone libraries also contained these 4 classes as well as sequences from the Dictyochophyceae, Bacillariophyceae and Prasinophyceae. However, the Prymnesiophyceae gave the dominant hybridisation signal and constituted the majority of each clone library. Their diversity, with a total of 190 sequences belonging to 114 operational taxonomic units (OTUs), probably allows them to dominate the ultraphytoplankton throughout the whole year under differing environmental conditions. Over 100 of these OTUs were unique to different libraries, suggesting a succession of different taxa during the year. The Cryptophyceae were present most of the year with 1 OTU, corresponding to a Plagioselmis prolonga strain from the Gulf of Naples, being the dominant taxon (28 % of sequences). A striking result was the high hybridisation signal from the Chrysophyceae, which showed a preference for the summer months. The Pelagophyceae were present between December and March. Most (80 %) of the sequences found in the clone libraries were not identical to available 16S rRNA gene sequences, indicating a high amount of hidden diversity for these algal classes. However, sequences from Prasinophyceae Clade II (Mamiellales) were not detected in the clone libraries

Morphological study of Chaetoceros wighamii Brightwell (Chaetocerotaceae, Bacillariophyta) from Lake Vrana, Croatia

Chaetoceros wighamii Brightwell is a planktonic diatom species originally described from brackish waters. Since its original description, the species has been reported in a wide variety of habitats, ranging from freshwater to marine. Varying descriptions exist in the taxonomic literature and several taxa have been considered as synonyms, including freshwater species Chaetoceros amanita. In this study we provide morphological and ultrastructural information on a cultured strain isolated from freshwater sample collected in the Lake Vrana (Vransko jezero) in Croatia, in April 2011. The cells form short and robust chains with very narrow apertures, often partially occluded by silica membranes. Other distinctive features observable in light microscopy are the shape and orientation of the setae which are very long, straight and robust, diverging in various directions from the chain axis and the single parietal chloroplast extending from valve to valve. Distinct ultrastructural characteristics are the absence of processes either in intercalary or terminal valves and the ornamentation of the valve face with densely distributed ribs spreading from an irregular eccentric hyaline area without a clearly defi ned annulus. The outer surface of the terminal valve is ornamented with small spines and setae are composed of flat longitudinal filaments interconnected with short bars and ornamented with small spines tightly arranged around the setae. Our description agrees well with that reported for the freshwater morphotypes of C. wighamii (syn. C. amanita) and contributes for a reliable distinction of this intriguing taxon from similar morphotypes. This finding supports the interpretation of Chaetoceros wighamii as a freshwater/brackish species and represents the first report of a Chaetoceros species in lacustrine environment in Croatia and possibly in any Central European habitats

Controlled growth of CNT in mesoporous AAO through optimized conditions for membrane preparation and CVD operation

Anodic aluminium oxide (RAAO) membranes with a mesoporous structure were prepared under strictly controlling experimental process conditions, and physically and chemically characterized by a wide range of experimental techniques. Commercial anodic aluminium oxide (CAAO) membranes were also investigated for comparison. We demonstrated that RAAO membranes have lower content of both water and phosphorus and showed better porosity shape than CAAO. The RAAO membranes were used for template growth of carbon nanotubes (CNT) inside its pores by ethylene chemical vapour deposition (CVD) in the absence of a catalyst. A composite material, containing one nanotube for each channel, having the same length as the membrane thickness and an external diameter close to the diameter of the membrane holes, was obtained. Yield, selectivity and quality of CNTs in terms of diameter, length and arrangement (i.e. number of tubes for each channel) were optimized by investigating the effect of changing the experimental conditions for the CVD process. We showed that upon thermal treatment RAAO membranes were made up of crystallized allotropic alumina phases, which govern the subsequent CNT growth, because of their catalytic activity, likely due to their Lewis acidity. The strict control of experimental conditions for membrane preparation and CNT growth allowed us to enhance the carbon structural order, which is a critical requisite for CNT application as a substitute for copper in novel nano-interconnects

A novel type of colony formation in marine planktonic diatoms revealed by atomic force microscopy

Diatoms have evolved a variety of colonial life forms in which cells are connected by organic threads, mucilage pads or silicate structures. In this study, we provide the first description of a novel strategy of colony formation among marine planktonic diatoms. Bacteriastrum jadranum is a chain‐forming centric diatom in which sibling cells are enclosed within the optically transparent organic matrix instead of fusing of silica between setae as it is the case in all other members of the family Chaetocerotaceae. This cell jacket structure was detected by staining procedures (Alcian Blue and Coomassie Brilliant Blue G), which showed that the polysaccharides are predominant matrix constituents and revealed that the jacket reaches the span of the setae. The scanning electron microscopy (SEM) observations showed distinguishable fibrillar network firmly associated with cells. Using atomic force microscopy (AFM), we were able to visualise and characterise the cell jacket structure at molecular resolution. At nanoscale resolution, the cell jacket appears as a cross‐linked fibrillar network organised into a recognisable structure. It is composed of non‐evenly distributed high density domains (patches) surrounded and interconnected by thicker fibrils. Inside the patches are the hexagonally shaped pores decreasing in size from the patch edge towards the center. The large pore openings found between the patches are formed by the robust branching fibrils and these represent the backbone of the fibrillar network. Such structure is porous, but at the same time highly flexible and mechanically stable. We conclude that the Bacteriastrum polysaccharide jacket represents an essential part of the cell, as such specific and unique patterns have never been found in self‐assembled polysaccharide gel networks, which are usually encountered in the marine environment

GERMINATION OF RESTING STAGES OF DIATOMS AND DINOFLAGELLATES IN MARINE SEDIMENTS FROM TWO UPWELLING AREAS OF CHILE

Con el fin de evaluar la potencial germinación de los estados de resistencia de las diatomeas y dinofiagelados preservados en sedimentos superficiales, se cultivaron bajo condiciones de laboratorio sedimentos de las bahías de Mejillones (23° S) y Concepción (36° S), Chile: Ciclo L:0 12:12 h, intensidad de luz 140 umol m²s_1, temperatura ambiente y 35,4 unidades de salinidad. Las principales especies de diatomeas presentes en los sedimentos fueron Skeletonema japonicum y esporas de Chaetoceros. Los quistes de dinofiagelados estuvieron representados por Diplopsalis, Scrippsiella, Woloszynskia y las especies Protoperidinium avellanum y P. leonis. Después de 20 días de cultivo, se registró germinación y crecimiento de S. japonicum y de varias especies de Chaetoceros, sin embargo su abundancia fue baja. Las diatomeas con crecimiento abundante fueron Stauroneis legleri, Pseudostaurosira trainorii, Pseudostaurosira sp.l, Pseudostaurosira sp. 2 y Navícula pseudoreinhardtii. El dinoflagelado Woloszynskia sp. también germinó y creció abundantemente. Este trabajo incluye una breve descripción de las especies cultivadas y algunos aspectos de su ecología. Se discuten las posibles causas de la pobre germinación de las diatomeas planctónicas, siendo la baja concentración de oxígeno disuelto en las aguas de fondo uno de los principales factores que presumiblemente afectaron la sobrevivencia de las esporas de resistencia. With the aim to assess germination of diatom and dinofiagellates resting spores we cultured under laboratory conditions surface sediments collected in the Mejillones Bay (23° S) and off Concepción (36° S), Chile. These sediments were cultured in the laboratory with a 12:12 h L/D cycle, light intensity of 140 umol m² s"¹, at room temperature, and with a salinity of 35.4 units. The main diatom species in the sediments were Skeletonema japonicum and Chaetoceros spores. Dinofiagellate cysts were represented by the genera Diplopsalis, Scrippsiella, and Woloszynskia and the species Protoperidinium avellanum and P. leonis. After 20 days of culturing, germination and growth was recorded for S. japonicum and several of the Chaetoceros species, although their abundance was low. The diatoms with abundant growth were Stauroneis legleri, Pseudostaurosira trainorii, Pseudostaurosira sp.l, Pseudostaurosira sp. 2, and Navícula pseudoreinhardtii. The dinofiagellate Woloszynskia sp. also germinated and grew abundantly in the culture. This study includes a brief description of the cultured species and some aspects of their ecology. In addition, we discuss the possible causes for low levels of germination in planktonic diatoms, finding low dissolved oxygen concentrations in the bottom waters to be one of the main factors that presumably affected the survival of resting spores in the sediment

Plankton food-webs: to what extent can they be simplified?

Plankton is a hugely diverse community including both unicellular and multicellular organisms, whose individual dimensions span over seven orders of magnitude. Plankton is a fundamental part of biogeochemical cycles and food-webs in aquatic systems. While knowledge has progressively accumulated at the level of single species and single trophic processes, the overwhelming biological diversity of plankton interactions is insufficiently known and a coherent and unifying trophic framework is virtually lacking. We performed an extensive review of the plankton literature to provide a compilation of data suitable for implementing food-web models including plankton trophic processes at high taxonomic resolution. We identified the components of the plankton community at the Long Term Ecological Research Station MareChiara in the Gulf of Naples. These components represented the sixty-three nodes of a plankton food-web. To each node we attributed biomass and vital rates, i.e. production, consumption, assimilation rates and ratio between autotrophy and heterotrophy in mixotrophic protists. Biomasses and rates values were defined for two opposite system's conditions; relatively eutrophic and oligotrophic states. We finally identified 817 possible trophic links within the web and provided each of them with a relative weight, in order to define a diet-matrix, valid for both trophic states, which included all consumers, fromn anoflagellates to carnivorous plankton. Vital rates for plankton resulted, as expected, very wide; this strongly contrasts with the narrow ranges considered in plankton system models implemented so far. Moreover, the amount and variety of trophic links highlighted by our review is largely excluded by state-of-the-art biogeochemical and food-web models for aquatic systems. Plankton models could potentially benefit from the integration of the trophic diversity outlined in this paper: first, by using more realistic rates; second, by better defining trophic roles of consumers in the planktonic web. We suggest that most trophic habits present in planktonic organisms must be contemplated in new generation plankton models.</p

Spring-time dynamics of diatom communities in landfast and underlying platelet ice in Terra Nova Bay, Ross Sea, Antarctica

We investigated the composition of diatom communities in annual fast ice and their variations over time during the 1999 austral spring in Terra Nova Bay (Ross Sea, Antarctica). Diatoms varied along the ice core in both cell abundance and species composition, with a minimum in the lower layer and a peak in the platelet ice. Planktonic species constituted in total about 98% of the diatom assemblage in the surface layers of the ice core down to the thickness of 220 cm. In the bottom ice and the underlying platelet-ice layer, the contribution of planktonic diatoms was lower (60% and 65%, respectively) at the beginning of the sampling period, and then decreased further to reach 30% in the bottom ice, where a remarkable biomass increase over time was caused by in situ growth and accumulation of benthic species. By contrast in the platelet-ice layer only small changes were recorded in the composition of the diatom assemblage, which was mainly constituted by the bloom of Fragilariopsis nana. The benthic species are generally not found in the water column, while species in the platelet-ice layer presumably constitute the seed for the initial plankton bloom during the ice-free periods in Terra Nova Bay

Time series and beyond: multifaceted plankton research at a marine Mediterranean LTER site

Plankton are a pivotal component of the diversity and functioning of coastal marine ecosystems. A long time-series of observations is the best tool to trace their patterns and variability over multiple scales, ultimately providing a sound foundation for assessing, modelling and predicting the effects of anthropogenic and natural environmental changes on pelagic communities. At the same time, a long time-series constitutes a formidable asset for different kinds of research on specific questions that emerge from the observations, whereby the results of these complementary studies provide precious interpretative tools that augment the informative value of the data collected. In this paper, we review more than 140 studies that have been developed around a Mediterranean plankton time series gathered in the Gulf of Naples at the station LTER-MC since 1984. These studies have addressed different topics concerning marine plankton, which have included: i) seasonal patterns and trends; ii) taxonomic diversity, with a focus on key or harmful algal species and the discovery of many new taxa; iii) molecular diversity of selected species, groups of species or the whole planktonic community; iv) life cycles of several phyto- and zooplankton species; and v) interactions among species through trophic relationships, parasites and viruses. Overall, the products of this research demonstrate the great value of time series besides the record of fluctuations and trends, and highlight their primary role in the development of the scientific knowledge of plankton much beyond the local scale

Hybrid One-Dimensional CNN and DNN Model for Classification Epileptic Seizure

Epilepsy is a common chronic brain disease caused by abnormal neuronal activity and the occurrence of sudden or transient seizures. Electroencephalogram (EEG) is a non-invasive technique commonly used to identify epileptic brain activity. However, visual detection of the EEG is subjective, time consuming, and labour intensive for the neurologist. Therefore, we propose an automatic seizure detection using a combination of one-dimension convolution neural network (1D-CNN) with majority voting and deep neural network (DNN). EEG signals features are extracted using discrete Fourier transform (DFT) and discrete wavelet transform (DWT) which then these features will be selected with XGBoost to minimize features classified with CNN. The proposed method experimental results show that it can detect epilepsy from EEG signals perfectly with an accuracy of 100%. However, the proposed method only yielded classified EEG signals from the University of Bonn Dataset as its results

Annotated 18S and 28S rDNA reference sequences of taxa in the planktonic diatom family Chaetocerotaceae

The species-rich diatom family Chaetocerotaceae is common in the coastal marine phytoplankton worldwide where it is responsible for a substantial part of the primary production. Despite its relevance for the global cycling of carbon and silica, many species are still described only morphologically, and numerous specimens do not fit any described taxa. Nowadays, studies to assess plankton biodiversity deploy high throughput sequencing metabarcoding of the 18S rDNA V4 region, but to translate the gathered metabarcodes into biologically meaningful taxa, there is a need for reference barcodes. However, 18S reference barcodes for this important family are still relatively scarce. We provide 18S rDNA and partial 28S rDNA reference sequences of 443 morphologically characterized chaetocerotacean strains. We gathered 164 of the 216 18S sequences and 244 of the 413 28S sequences of strains from the Gulf of Naples, Atlantic France, and Chile. Inferred phylogenies showed 84 terminal taxa in seven principal clades. Two of these clades included terminal taxa whose rDNA sequences contained spliceosomal and Group IC1 introns. Regarding the commonly used metabarcode markers in planktonic diversity studies, all terminal taxa can be discriminated with the 18S V4 hypervariable region; its primers fit their targets in all but two species, and the V4-tree topology is similar to that of the 18S. Hence V4-metabarcodes of unknown Chaetocerotaceae are assignable to the family. Regarding the V9 hypervariable region, most terminal taxa can be discriminated, but several contain introns in their primer targets. Moreover, poor phylogenetic resolution of the V9 region affects placement of metabarcodes of putative but unknown chaetocerotacean taxa, and hence, uncertainty in taxonomic assignment, even of higher taxa.info:eu-repo/semantics/publishedVersio