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– Sem (scanning electron microscopy) of Pseudo-nitzschia species in nW mediterranean Sea. a and d, P. fraudulenta (St. 22, 4/07/05); B, e and F, P. multistriata (St. 15, 28/08/05); c and g, P. pungens (St. 11, 27/02/05).
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Potentially toxic species of the genus Pseudo-nitzschia were studied along the Spanish NW Mediterranean coast from January 2005 to May 2006. Observation in electron microscopy revealed the presence of Pseudo-nitzschia brasiliana, P. calliantha, P. delicatissima, P. fraudulenta, P. multistriata and P. pungens. Several strains were isolated from coas...
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В статье представлены результаты исследования таксономического состава и количества фитопланктона в акватории порта Туапсе и за его пределами в весенне-летний период 2019 г. В апреле 2019 г. обнаружено 43 вида фитопланктона, относящихся к 5 отделам. Средние по акватории порта величи́ны численности и биомассы составили 568 тыс. кл.·л−1 и 206 мг·м−3...
Pseudo-nitzschia is a species-rich genus with many species able to induce harmful algae blooms (HABs) associated with the toxin, domoic acid (DA), production. Despite their high diversity revealed by taxonomical studies, the composition and spatial–temporal dynamics of Pseudo-nitzschia species in marine ecological systems are often inadequately res...
A toxic Pseudo-nitzschia spp. bloom in the Todos Santos Bay area (31.8°N), Mexico, is described. This is the southernmost report of the presence of domoic acid (DA) in the California Current System and it is also the first report of the distribution of toxic Pseudo-nitzschia species and DA on the Baja California west coast. The maximum cell abundan...
In 1987, there was an episode of shellfish poisoning in Canada with human fatalities caused by the diatom Pseudo-nitzschia multiseries, which produced the toxin domoic acid. In order to examine whether domoic acid in this diatom serves as a grazing deterrent for copepods, we compared feeding rates, egg production rates, egg hatching success and mor...
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... Apparently, P. calliantha was more related to relatively high temperatures and low levels of SiO 3 2+ (Fig. 9a), which may explain why it dominated some of the southern stations (A09, B05, B09, C05, C09). This was consistent with the result that P. calliantha increased in cell density or bloomed when the temperature increased in summer or autumn in the north-western Mediterranean or in the coastal waters of the northern Adriatic Sea (Marić et al., 2011;Quijano-Scheggia et al., 2008). Similarly, Stonik et al. (2021) found that P. calliantha replaced P. multiseries as the major Pseudo-nitzschia taxa in the Sea of Japan when affected by global warming. ...
Pseudo-nitzschia is a cosmopolitan phytoplankton genus of which some species can form blooms and produce the neurotoxin domoic acid (DA). Identification of Pseudo-nitzschia is generally based on field material or strains followed by morphological and/or molecular characterization. However, this process is time-consuming and laborious, and can not obtain a relatively complete and reliable profile of the Pseudo-nitzschia community, because species with low abundance in the field or potentially unavailable for culturing may easily be overlooked. In the present study, specific ITS primer sets were designed and evaluated using in silico matching. The primer set ITS-84F/456R involving the complete ITS1 region was found optimal. Based on matching with a Pseudo-nitzschia ITS1 reference sequence database carefully-calibrated in this study, a metabarcoding approach using annotated amplicon sequence variants (ASV) was applied in the Taiwan Strait of the East China Sea during two cruises in the spring and summer of 2019. In total, 48 Pseudo-nitzschia species/phylotypes including 36 known and 12 novel were uncovered, and verified by haplotype networks, ITS2 secondary structure comparisons and divergence analyses. Correlation analyses revealed that temperature was a key factor affecting the seasonal variation of the Pseudo-nitzschia community. This study provides an overview of the Pseudo-nitzschia community in the Taiwan Strait, with new insights into the diversity. The developed metabarcoding approach may be used elsewhere as a standard reference for accurate annotation of Pseudo-nitzschia.
... Newly found species, P. brasiliana, P. galaxiae, P. hasleana, and P. linea, have already been reported in the Mediterranean Sea. Pseudo-nitzschia brasiliana and P. galaxiae are widely distributed in the Mediterranean Sea and were reported from Greece, Spain, Italy, France, Tunisia (only P. brasiliana), and Morocco (only P. galaxiae) [41,46,47,[50][51][52][53][54][55]. It is worth mentioning that P. brasiliana was considered a warm-water species [43]. ...
... It is worth mentioning that P. brasiliana was considered a warm-water species [43]. This is also supported by the findings in the Mediterranean Sea during the late summer to early autumn seasons [46,47,50]. In the present study, the occurrence of P. brasiliana was restricted to the period of low seawater temperatures. ...
Marine diatoms of the genus Pseudo-nitzschia are widespread and occur in various environments. About half of the species described today have been shown to be toxic, producing the potent neurotoxin, domoic acid. The Pseudo-nitzschia species are a common component of the Adriatic phytoplankton community and are occasionally predominant. In the present study, the composition of the Pseudo-nitzschia species was studied in four distinct aquaculture areas from February 2022 to February 2023. These are the first results of a comprehensive study of Pseudo-nitzschia diversity combining morphological and molecular analyses. The integrated approach resulted in the confirmation of Pseudo-nitzschia brasiliana, Pseudo-nitzschia hasleana, Pseudo-nitzschia galaxiae, and Pseudo-nitzschia linea. The species, P. galaxiae, was the most frequently occurring, P. linea was found in all investigated areas, while P. hasleana and P. brasiliana were rare, and their distribution was limited mainly to Kaštela Bay. The findings of P. brasiliana and P. hasleana represent the first confirmation for the Adriatic Sea, while P. galaxiae and P. linea have not been previously reported along the eastern Adriatic coast.
... Sonication was used to break the cells and the suspension was cleared by filtration through a 0.22 µm syringe filter. The HPLC was equipped with a reversephase column (Eclipse XDB C 8 ) and the detection was performed with spectral absorption Mass and molar pigment ratios from monospecific cultures obtained by HPLC and published in the literature (Rodríguez et al., 2006;van Leeuwe et al., 2014;Zapata et al., 2011;Latasa et al., 2004;Zapata et al., 2004;Brotas and Plante-Cuny, 2003;Schlüter et al., 2000;Moisan and Mitchell, 1999;Vaulot et al., 1994;Laza-Martinez et al., 2007;Liu et al., 2014;Zapata et al., 2012;Seoane et al., 2009;Antajan et al., 2004;Liu et al., 2011;Fagín et al., 2019;Clementson and Wojtasiewicz, 2019a;Quijano-Scheggia et al., 2008) were compiled and combined with our measurements to produce a harmonized dataset of pigmentation in cyanobacteria and microalgae. By harmonized we mean that the pigment resolving power of each method was taken in consideration together with the pigment distribution across pigmentation groups and that mass and molar ratios were inter-converted as necessary by using the molecular weight of each pigment . ...
Hydrologic optics and aquatic remote sensing are fields of applied optics that aim to retrieve information of state and process of aquatic systems from optical signals. Such an inference link depends on a rich set of paired optical and biogeochemical data, robust development and evaluation of algorithms and deep understanding of the underlying processes in order to support meaningful ecological interpretation. In this research we further explore the toolset available to apply remote sensing to water quality, by evaluating and proposing improvements for methods of field spectroscopy, describing a dataset with detailed compositional information covering a diverse range of environmental conditions in Belgian waters, and by providing algorithms to retrieve information of the phytoplankton assemblage for use with in situ optical instrumentation and remote sensors.
In Chapter 1 we provide an overview of the key concepts in hydrologic optics and aquatic remote sensing that provide the context for this study.
In Chapter 2 we provide a detailed evaluation of the uncertainty in downwelling irradiance estimations with diffuse reflectors, a topic overlooked despite large sets of data, particularly in inland waters, collected with this methodology. Our results help to shed light into uncertainty budgets of past measurements and provide basis for suggestion for an improved measurement protocol. Based on the magnitude of the uncertainty, we are also able to ascertain the suitability of this method for all uses of downwelling irradiance in hydrologic optics.
In Chapter 3 we provide another detailed evaluation related to errors in water-leaving radiance measurements with the on-water approach, a relatively recent method for field spectroscopy. We specifically evaluate the deployment setup used in this research, in order to provide corrections to our measurements. Additionally, we provide evaluations of the sensitivity of the error and simulations to parameters like backscattering ratio and the angular distribution of the downwelling radiance. We further provide evaluation of different deployment setups and suggest possible improvements for the method.
In Chapter 4 we describe the full set of paired optical and biogeochemical data collected in Belgian inland and coastal waters. Extensive evaluations are provided to assert data consistency as a proxy for its accuracy. Of particular interest is the pairing of inherent and apparent optical data with particle size distribution, mineral fraction and metabarcoding, providing detailed composition information that can be used for devolvement of hyperspectral algorithms. The data is made freely available in a stable repository.
In Chapter 5 we describe and validate a method to extract additional spectral information from a system of overlapping wavebands and apply this concept to the Operational Land Imager (OLI) onboard Landsat~8. We show that a virtual band, termed contra-band, with information on the yellow-orange spectra region covering the absorption peak of phycocyanin can be extracted from the panchromatic band of OLI. We provide extensive evaluations of the uncertainty and generality of the algorithm and of the independence of the retrieved information.
In Chapter 6 we revisit the problem of optical detection of Phaeocystis globosa blooms in the Belgian Coastal Zone (BCZ) by evaluating the origin of the signal detected by previously proposed hyperspectral algorithms. We show that the signal detected is not specific of Phaeocystis globosa even when considering the phytoplankton assemblage composition of the BCZ, due to synchronous phenology of other blooming species producing similar optical signals. We further uncover an apparent general pigmentation pattern associated with presence of chlorophyll c3. We conclude by providing a new algorithm to detect this pigmentation pattern and provide a regional ecological interpretation linked to harmful algal blooms (HABs).
The research in those chapters is extensively supported with additional information in the form of theory, data and analysis provided in various Appendices. Lastly, in Chapter 7 we provide a synthesis of this research, discussing the relevance of our findings in the scope of hydrologic optics and aquatic remote sensing.
... During the last two decades, the combination of ultrastructural characters obtained by scanning and transmission electron microscopy (SEM and TEM, respectively) along with molecular methods has led to the description of many new Pseudo-nitzschia species (Lundholm et al., 2003;Quijano-Scheggia et al., 2008;Lim et al. 2013, Dong et al., 2020Chen et al., 2021). The genus currently includes more than 58 described species (Chen et al., 2021), 29 of which are DA producers (Lundholm, 2022). ...
Species of the potentially toxic diatom genus Pseudo-nitzschia are common components of the phytoplankton
community in the fjords and channel systems of the Magallanes Subantarctic region. Despite Pseudo-nitzschia
species forming recurrent harmful algal blooms (HABs) in this region, Chilean monitoring programs have his-
torically simply grouped species of this genus into two groups (P. group seriata and P. group delicatissima) ac-
cording to basic cell morphology under light microscopy, or as Pseudo-nitzschia spp. Based on ultrastructural
features obtained from scanning electron microscopy (SEM), this study revealed more diversity within the genus
than previously thought, identifying six Pseudo-nitzschia species in the Magallanes Subantarctic region (48◦-56◦S)
from samples collected during a 11-year period (2006–2017). Most importantly, the study: 1) represent the first
report on diversity and distribution of Pseudo-nitzschia species in this Patagonian region; 2) expanded the known
distribution of P. australis and P. fraudulenta along the Chilean coast (down to 50◦ S); 3) confirmed previous
records of P. pungens and P. cf. delicatissima; and 4) formally confirm the presence of P. heimii and P. calliantha in
subantartic waters
... In the Mediterranean Sea, seasonal blooms of Pseudo-nitzschia spp. are frequently reported (e.g., Cerino et al., 2005;Quijano-Scheggia et al., 2008;Marić et al., 2011). However, impacts on health and economy by these diatoms are rare in the basin (Zingone et al., 2020). ...
Pseudo-nitzschia is a widespread genus of marine pennate diatoms comprising 58 species of which 28 can produce the neurotoxin domoic acid, causative of Amnesic Shellfish Poisoning (ASP). Species of the genus are found in both oceanic and coastal waters where they can form large blooms. The timing and magnitude of blooms is generally described based on water samples collected at the surface, while limited information is available on cell distribution within the water column. To address this knowledge gap, we investigated the vertical (0-50 m) distribution of Pseudo-nitzschia species identified in light microscopy using weekly samples collected in the Gulf of Naples (Italy) across an annual cycle (April 2006-April 2007). Physical variables and nutrient concentrations were also monitored. The genus is primarily abundant in surface waters, where spring blooms of P. cf. delicatissima and two morphotypes of P. galaxiae were related to the presence of a water layer with low salinity and high concentration of inorganic nutrients. Blooms of P. cf. pseudodelicatissima, P. allochrona and P. multistriata were recorded at surface during the summer-early autumn, when the water column was stratified and nutrient concentrations were low. Our observations confirmed the marked seasonality of Pseudo-nitzschia species described at our study site with light microscopy and molecular approaches, with species virtually absent from surface waters for long periods of the year. However, the high quantitative resolution applied in this study allowed to reveal low concentrations of Pseudo-nitzschia species/species complexes throughout the water column over the year. Since Pseudo-nitzschia do not produce benthic resting stages, their presence in deeper waters suggests that these species rely on rare overwintering cells that can function as bloom inocula.
... Mass and molar pigment ratios from monospecific cultures obtained by HPLC and published in the literature (Buma et al., 1991;Vaulot et al., 1994;Moisan and Mitchell, 1999;Schlüter et al., 2000;Brotas and Plante-Cuny, 2003;Antajan et al., 2004;Latasa et al., 2004;Zapata et al., 2004Zapata et al., , 2011Zapata et al., , 2012Rodríguez et al., 2006;Laza-Martinez et al., 2007;Quijano-Scheggia et al., 2008;Astoreca et al., 2009;Seoane et al., 2009;Liu et al., 2011Liu et al., , 2014van Leeuwe et al., 2014;Organelli et al., 2017;Clementson and Wojtasiewicz, 2019b;Fagín et al., 2019) were compiled and combined with our measurements to produce a harmonized dataset of pigmentation in cyanobacteria and microalgae. By harmonized we mean that the pigment resolving power of each method was taken in consideration together with the pigment distribution across pigmentation groups (Jeffrey et al., 2011) and that mass and molar ratios were inter-converted as necessary by using the molecular weight of each pigment (Egeland et al., 2011). ...
... The study of Antajan et al. (2004) was the first to demonstrate the high correlation between TChl c 3 and P. globosa in the BCZ, though the authors were careful to note that the pigmentation patterns of other major diatoms with similar bloom phenology, including Pseudo-nitzschia and Rhizosolenia, were not known. The studies of Quijano-Scheggia et al. (2008) and Zapata et al. (2011) on the pigmentation patterns of Pseudo-nitzschia species showed that P. delicatissima and P. pungens not only contain DVChl c 3 but also have a similar pigmentation signature to P. globosa. In particular, P. delicatissima can dominate the diatom biomass in the period of April-May in areas of the southern North Sea (Delegrange et al., 2018;Speeckaert et al., 2018) and its co-occurrence with P. globosa has been suggested to result from an ecological association where one of the species uses the other as substrate for growth. ...
Phaeocystis globosa is a nuisance haptophyte species that forms annual blooms in the southern North Sea and other coastal waters. At high biomass concentration, these are considered harmful algal blooms due to their deleterious impact on the local ecosystems and economy, and are considered an indicator for eutrophication. In the last two decades, methods have been developed for the optical detection and quantification of these blooms, with potential applications for autonomous in situ or remote observations. However, recent experimental evidence suggests that the interpretation of the optical signal and its exclusive association with P. globosa may not be accurate. In the North Sea, blooms of P. globosa are synchronous with those of the diatom Pseudo-nitzschia delicatissima, another harmful bloom-forming species with similar pigmentation and optical signature. Here we combine new and published measurements of pigmentation composition and inherent optical properties from pure cultures of several algal and cyanobacterial groups, together with environmental spectroscopy data, to identify the pigments generating the optical signals captured by two established algorithms. We further evaluate the association of those pigments and optical signals with P. globosa. We found that the interpretation of the pigment(s) generating the optical signals were incorrect and that previous methods are not specific to P. globosa, even in the context of the phytoplankton assemblage of the southern North Sea. Additionally, we found that the optical and pigment signatures of Phaeocystis species are part of a broad pigmentation trend across unrelated taxonomic groups related to chlorophyll c3 presence, with important consequences for the interpretation of pigment and optical data. We then develop and evaluate an algorithm to detect this pigmentation pattern with minimal influence of co-occurring species and elaborate general recommendations for the future development of algorithms.
... The morphological examination of Pseudo-nitzschia cells (Table S2, Supplementary Materials) from the obtained cultures agrees in length of apical axis with the description of strains of P. multistriata from China [43], Tunisia [44], Catalan Coast [45,46], Gulf of Naples [47,48] and the Western Adriatic Sea [49]. Similarly, the width of the transapical axis corresponds to descriptions of cells from Ria de Aveiro, Portugal [50], Tokyo bay [51], New Zealand [52], Mexico [53] and Uruguay [54]. ...
Citation: Tenorio, C.; Álvarez, G.; Quijano-Scheggia, S.; Perez-Alania, M.; Arakaki, N.; Araya, M.; Álvarez, F.; Blanco, J.; Uribe, E. First Report of Domoic Acid Production from Pseudo-nitzschia multistriata in Paracas Bay (Peru). Toxins 2021, 13, 408. https://doi. Abstract: The Peruvian sea is one of the most productive ecosystems in the world. Phytoplankton production provides food for fish, mammals, mollusks and birds. This trophic network is affected by the presence of toxic phytoplankton species. In July 2017, samples of phytoplankton were obtained from Paracas Bay, an important zone for scallop (Argopecten purpuratus) aquaculture in Peru. Morphological analysis revealed the presence of the genus Pseudo-nitzschia, which was isolated and cultivated in laboratory conditions. Subsequently, the monoclonal cultures were observed by scanning electron microscopy (SEM), and identified as P. multistriata, based on both the morphological characteristics, and internal transcribed spacers region (ITS2) sequence phylogenetic analysis. Toxin analysis using liquid chromatography (LC) with high-resolution mass spectrometry (HRMS) revealed the presence of domoic acid (DA) with an estimated amount of 0.004 to 0.010 pg cell −1. This is the first report of DA from the coastal waters of Peru and its detection in P. multistriata indicates that it is a potential risk. Based on our results, routine monitoring of this genus should be considered in order to ensure public health. Key Contribution: The presence of P. multistriata, domoic acid-producing species in the phytoplank-ton communities of Paracas Bay. Relevant information on the monitoring of harmful phytoplankton species along the Peruvian coast.
... Regarding other environmental parameters, Pseudo-nitzschia was negatively correlated with nitrate and orthosilicate concentrations as observed in the southwestern Mediterranean (Sahraoui et al., 2012). In contrast, Quijano-Scheggia et al. (2008a;2008b) found that high abundances of P. delicatissima were associated with a high concentration of nitrates while according to Macintyre et al. (2011) submarine groundwaters, rich in nitrate, are potential hot-spots for Pseudo-nitzschia blooms. ...
The aim of the present study isto characterise the diatom Pseudo-nitzschia community during a bloom period together with environmental conditions. High proliferation of Pseudo-nitzschia spp. was observed in September 2017 at the shellfish breeding area in the Krka River estuary (Central eastern Adriatic Sea). The peak of abundance (1.8 x 106 cells L-1) was recorded at 7 m depth, and the increased abundance persisted for four weeks.Morphological analyses of field samples based on scanning electron microscopy (SEM) revealed that Pseudo-nitzschia cf. arenysensis was prevailing (94%) in the Pseudo-nitzschia assemblage. Several strains were successfully isolated from net samples in order to better define morphological features and phylogenetic characterisation. The isolated Pseudo-nitzschia strains corresponded morphologically to the P. cf. arenysensis from the field samples, based on our SEM observations. Phylogenetic analysis demonstrated that the Croatian strains grouped with P. arenysensis using the ITS and LSU rDNA sequences. Spearman rank correlation showed that salinity was an important environmental factor affecting the vertical distribution of Pseudo-nitzschia spp. in this highly variable area. Availability of increased concentration of orthophosphates and ammonium and low Si: TIN ratio may have promoted the bloom of P. cf. arenysensis in the estuary.
... Pseudo-nitzschia pungens has been commonly recorded in the phytoplankton community of the Mediterranean Sea, although its geographical distribution is seemingly restricted to the northernmost areas of the basin in the NW [28,[32][33][34][35], as well as in NE Mediterranean Sea [29], and it is a quite recurrent species in the diatom community of the northern Adriatic Sea [30,[36][37][38]. Previous molecular studies carried out on the P. pungens from the northern Adriatic have highlighted that the Adriatic strain belonged to clade I [30]. ...
Pseudo-nitzschia pungens is a common component of the phytoplankton community of the northern Adriatic Sea. In this study, an in-depth morphological analysis of P. pungens was carried out in both cultured strains isolated in different periods and field samples, revealing a surprisingly wide variability in a number of details, with both the gross morphology and ultrastructural levels deviating from the nominal P. pungens. Colonies showed an overlap (from one-third to one-sixth) and a transapical axis (rarely reaching 3 µm), strongly differing from the original description of the species. Moreover, valves may be either symmetrical or slightly asymmetrical, with striae almost always biseriate but sometimes uniseriate or triseriate. Poroids' morphology in cingular bands was characterized by a wide variability (square, circular, or rectangular poroids without or with up to two hymen sectors), with several combination of them, even within the same cingular band. Phylogenetic analyses based on ITS rDNA showed that the P. pungens of the northern Adriatic Sea belonged to clade I. Domoic acid was not detected.
... Pseudo-nitzschia pseudodelicatissima/cuspidata were highly present in assemblage throughout the year, but prevailed during the winter. Previously, P. pseudodelicatissima/cuspidata was commonly found in Pseudo-nitzschia assemblage of the Central Adriatic Sea [9,25], but, contrary to our findings, in some Mediterranean areas it was scarce or not detected at all [14,[53][54][55]. ...
The Krka River estuary is a karstic, permanently stratified estuary due to the strong freshwater inflow. It is a special environment in which to study the phytoplankton community, especially because this area is an important aquaculture site. Among other potentially toxic phytoplankton species, the diatom genus Pseudo-nitzschia occurs frequently and is a potential source of domoic acid (DA), causing shellfish toxicity and human intoxication. The main objective was to examine the dynamics of the phytoplankton community and, in particular, the genus Pseudo-nitzschia in the upper part of the Krka estuary, through monthly sampling over two years. The phytoplankton community was analysed using light microscopy and scanning electron microscopy to determine the diversity of Pseudo-nitzschia species and characterise the environmental parameters associated with a high abundance of Pseudo-nitzschia species. Seven Pseudo-nitzschia species were identified in the investigation, with higher frequencies and abundances in the less variable layer, at a 7 m depth. Blooms of Pseudo-nitzschia were noted in the late summer/early autumn, dominated by P. delicatissima/arenysensis. Winter assemblages were characterised by P. pseudodelicatissima/cuspidata, P. calliantha, and P. subfraudulenta, and were associated with domoic acid occurrence in shellfish.
