Transition from a mixotrophic/heterotrophic protist community during the dark winter to a photoautotrophic spring community in surface waters of Disko Bay, Greenland.

Unicellular eukaryotic plankton communities (protists) are the major basis of the marine food web. The spring bloom is especially important, because of its high biomass. However, it is poorly described how the protist community composition in Arctic surface waters develops from winter to spring. We show that mixotrophic and parasitic organisms are prominent in the dark winter period. The transition period toward the spring bloom event was characterized by a high relative abundance of mixotrophic dinoflagellates, while centric diatoms and the haptophyte Phaeocystis pouchetii dominated the successive phototrophic spring bloom event during the study. The data shows a continuous community shift from winter to spring, and not just a dormant spring community waiting for the right environmental conditions. The spring bloom initiation commenced while sea ice was still scattering and absorbing the sunlight, inhibiting its penetration into the water column. The initial increase in fluorescence was detected relatively deep in the water column at ~55 m depth at the halocline, at which the photosynthetic cells accumulated, while a thick layer of snow and sea ice was still obstructing sunlight penetration of the surface water. This suggests that water column stratification and a complex interplay of abiotic factors eventually promote the spring bloom initiation.

A Pseudo-nitzschia metabarcoding approach with a calibrated ITS1 reference sequence database applied in the Taiwan Strait.

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.

Did algal toxin and Klebsiella infections cause the unexplained 2007 mass mortality event in Danish and Swedish marine mammals?

An unusual mass mortality event (MME) of harbour seals (Phoca vitulina) and harbour porpoises (Phocoena phocoena) occurred in Denmark and Sweden in June 2007. Prior to this incident, the region had experienced two MMEs in harbour seals caused by Phocine Distemper Virus (PDV) in 1988 and 2002. Although epidemiology and symptoms of the 2007 MME resembled PDV, none of the animals examined for PDV tested positive. Thus, it has been speculated that another - yet unknown - pathogen caused the June 2007 MME. To shed new light on the likely cause of death, we combine previously unpublished veterinary examinations of harbour seals with novel analyses of algal toxins and algal monitoring data. All harbour seals subject to pathological examination showed pneumonia, but were negative for PDV, influenza and coronavirus. Histological analyses revealed septicaemia in multiple animals, and six animals tested positive for Klebsiella pneumonia. Furthermore, we detected the algal Dinophysis toxin DTX-1b (1-115 ng g-1) in five seals subject to toxicology, representing the first time DTX-1b has been detected in marine vertebrates. However, no animals tested positive for both Klebsiella and toxins. Thus, while our relatively small sample size prevent firm conclusions on causative agents, we speculate that the unexplained MME may have been caused by a chance incidence of multiple pathogens acting in parallel in June 2007, including Dinophysis toxin and Klebsiella. Our study illustrates the complexity of wildlife MMEs and highlights the need for thorough sampling during and after MMEs, as well as additional research on and monitoring of DTX-1b and other algal toxins in the region.

Emerging phylogeographic perspective on the toxigenic diatom genus Pseudo-nitzschia in coastal northern European waters and gateways to eastern Arctic seas: Causes, ecological consequences and socio-economic impacts.

The diatom Pseudo-nitzschia H. Peragallo is perhaps the most intensively researched genus of marine pennate diatoms, with respect to species diversity, life history strategies, toxigenicity, and biogeographical distribution. The global magnitude and consequences of harmful algal blooms (HABs) of Pseudo-nitzschia are particularly significant because of the high socioeconomic impacts and environmental and human health risks associated with the production of the neurotoxin domoic acid (DA) among populations of many (although not all) species. This has led to enhanced monitoring and mitigation strategies for toxigenic Pseudo-nitzschia blooms and their toxins in recent years. Nevertheless, human adaptive actions based on future scenarios of bloom dynamics and proposed shifts in biogeographical distribution under climate-change regimes have not been implemented on a regional scale. In the CoCliME (Co-development of climate services for adaptation to changing marine ecosystems) program these issues were addressed with respect to past, current and anticipated future status of key HAB genera such as Pseudo-nitzschia and expected benefits of enhanced monitoring. Data on the distribution and frequency of Pseudo-nitzschia blooms in relation to DA occurrence and associated amnesic shellfish toxin (AST) events were evaluated in a contemporary and historical context over the past several decades from key northern CoCliME Case Study areas. The regional studies comprised the greater North Sea and adjacent Kattegat-Skagerrak and Norwegian Sea, eastern North Atlantic marginal seas and Arctic gateways, and the Baltic Sea. The first evidence of possible biogeographical expansion of Pseudo-nitzschia taxa into frontier eastern Arctic gateways was provided from DNA barcoding signatures. Key climate change indicators, such as salinity, temperature, and water-column stratification were identified as drivers of upwelling and advection related to the distribution of regional Pseudo-nitzschia blooms. The possible influence of changing variables on bloom dynamics, magnitude, frequency and spatial and temporal distribution were interpreted in the context of regional ocean climate models. These climate change indicators may play key roles in selecting for the occurrence and diversity of Pseudo-nitzschia species within the broader microeukaryote communities. Shifts to higher temperature and lower salinity regimes predicted for the southern North Sea indicate the potential for high-magnitude Pseudo-nitzschia blooms, currently absent from this area. Ecological and socioeconomic impacts of Pseudo-nitzschia blooms are evaluated with reference to effects on fisheries and mariculture resources and coastal ecosystem function. Where feasible, effective adaptation strategies are proposed herein as emerging climate services for the northern CoCLiME region.

Phytoplankton diversity explained by connectivity across a mesoscale frontal system in the open ocean.

Phytoplankton community composition is important in establishing ecosystem structure and function. Intuitively, we recognize that water movements must be important for modifying spatial gradients and plankton diversity. However, identifying boundaries and exchange between habitats in the open ocean is not straightforward. Here, we use the abundance of nine phytoplankton species closely sampled in a mesoscale frontal system in the northeastern North Sea as a proxy for community composition and explore the relationship between phytoplankton biogeography and transport patterns. Subsurface community distributions could be related to modeled patterns in water movement. A methodology for analyzing pelagic diversity that includes a representation of plankton community composition and an Eulerian connectivity tracer was developed, and the relative importance of connectivity and geographical distance for phytoplankton species composition analyzed. The connectivity tracer identifies timescales and dispersal barriers in the open ocean. Connectivity was found to be superior in explaining pelagic plankton diversity and found to be a prerequisite for understanding the pelagic phytoplankton composition. This approach is a valuable tool for establishing the link between ocean transports, ecosystem structure and biodiversity and for informing the placement of marine protected areas.

Gambierdiscus (Gonyaulacales, Dinophyceae) diversity in Vietnamese waters with description of G. vietnamensis sp. nov.

Viet Nam has a coastline of 3200 km with thousands of islands providing diverse habitats for benthic harmful algal species including species of Gambierdiscus. Some of these species produce ciguatera toxins, which may accumulate in large carnivore fish potentially posing major threats to public health. This study reports five species of Gambierdiscus from Vietnamese waters, notably G. australes, G. caribaeus, G. carpenteri, G. pacificus, and G. vietnamensis sp. nov. All species are identified morphologically by LM and SEM, and identifications are supported by molecular analyses of nuclear rDNA (D1-D3 and D8-D10 domains of LSU, SSU, and ITS1-5.8S-ITS2 region) based on cultured material collected during 2010-2021. Statistical analyses of morphometric measurements may be used to differentiate some species if a sufficiently large number of cells are examined. Gambierdiscus vietnamensis sp. nov. is morphologically similar to other strongly reticulated species, such as G. belizeanus and possibly G. pacificus; the latter species is morphologically indistinguishable from G. vietnamensis sp. nov., but they are genetically distinct, and molecular analysis is deemed necessary for proper identification of the new species. This study also revealed that strains denoted G. pacificus from Hainan Island (China) should be included in G. vietnamensis sp. nov.

On the origin and evolution of RNA editing in metazoans.

Extensive adenosine-to-inosine (A-to-I) editing of nuclear-transcribed mRNAs is the hallmark of metazoan transcriptional regulation. Here, by profiling the RNA editomes of 22 species that cover major groups of Holozoa, we provide substantial evidence supporting A-to-I mRNA editing as a regulatory innovation originating in the last common ancestor of extant metazoans. This ancient biochemistry process is preserved in most extant metazoan phyla and primarily targets endogenous double-stranded RNA (dsRNA) formed by evolutionarily young repeats. We also find intermolecular pairing of sense-antisense transcripts as an important mechanism for forming dsRNA substrates for A-to-I editing in some but not all lineages. Likewise, recoding editing is rarely shared across lineages but preferentially targets genes involved in neural and cytoskeleton systems in bilaterians. We conclude that metazoan A-to-I editing might first emerge as a safeguard mechanism against repeat-derived dsRNA and was later co-opted into diverse biological processes due to its mutagenic nature.

Costs and benefits of predator-induced defence in a toxic diatom.

Phytoplankton employ a variety of defence mechanisms against predation, including production of toxins. Domoic acid (DA) production by the diatom Pseudo-nitzschia spp. is induced by the presence of predators and is considered to provide defence benefits, but the evidence is circumstantial. We exposed eight different strains of P. seriata to chemical cues from copepods and examined the costs and the benefits of toxin production. The magnitude of the induced toxin response was highly variable among strains, while the costs in terms of growth reduction per DA cell quota were similar and the trade-off thus consistent. We found two components of the defence in induced cells: (i) a 'private good' in terms of elevated rejection of captured cells and (ii) a 'public good' facilitated by a reduction in copepod feeding activity. Induced cells were more frequently rejected by copepods and rejections were directly correlated with DA cell quota and independent of access to other food items. By contrast, the public-good effect was diminished by the presence of alternative prey suggesting that it does not play a major role in bloom formation and that its evolution is closely associated with the grazing-deterrent private good.

Matrisome alterations in obesity - Adipose tissue transcriptome study on monozygotic weight-discordant twins.

Adipose tissue is a central regulator of metabolic health and its failure in obesity is a major cause of weight associated comorbidities, such as type 2 diabetes. Many extracellular matrix proteins, represented by matrisome, play a critical role in balancing adipose tissue health and dysfunction. Extracellular matrix components, produced by different cell types of adipose tissue, can modulate adipocyte function, tissue remodeling during expansion, angiogenesis, and inflammation and also form fibrotic lesions in the tissue. In this study, we investigated changes in matrisome of whole adipose tissue and adipocytes in human obesity. We investigated further the networks and biological pathways of the genes related to the changes and their association to development of metabolic dysfunction linked to type 2 diabetes. We used transcriptome data and clinical metabolic parameters from a rare weight-discordant MZ twin cohort. The Heavy-Lean differential matrisome gene expression (Δmatrisome) and differential metabolic parameters reflect changes in adipose tissue upon weight gain and changes in whole body glucose, insulin metabolism, as well as lipid status. We report that obesity Δmatrisome shows high specificity with 130 and 71 of the 1068 matrisome genes showing altered expression in the adipose tissue and adipocytes of heavier co-twin, respectively. The Δmatrisome differs considerably between adipose tissue vs adipocytes which reflects inflammation of hypertrophic adipocytes and the remodeling activity of the rest of the tissue resident cells. The obesity Δmatrisome is discussed extensively in the light of existing evidence and novel significant associations to obesity are reported to matrisome genes; cathepsin A, cathepsin O, FAM20B and N-glycanase1.

Seasonal plankton succession is in accordance with phycotoxin occurrence in Disko Bay, West Greenland.

Harmful algal blooms (HABs) are occurring more frequently in the world's oceans, probably as a consequence of climate change. HABs have not been considered a serious concern in the Arctic, even though the Arctic warms faster than any other region. While phycotoxins and toxin-producing phytoplankton have been found in Arctic waters on several occasions, there is a lack of information on seasonal succession of species and whether the occurrence of harmful species correlates with the presence of their respective phycotoxins. Hence, there is no baseline to assess future changes of HABs in this area. Here, we investigated two periods, from winter to spring and from the spring bloom until summer, in Disko Bay, West Greenland and followed the succession of toxins and their producers using metabarcoding, as well as analyses of particulate and dissolved toxins. We observed a typical seasonal succession with a spring bloom dominated by diatoms, followed by dinoflagellates in summer, with the two most important potentially toxic taxa found being Pseudo-nitzschia spp. and Alexandrium ostenfeldii. The Pseudo-nitzschia spp. peak correlated with a clear increase in particulate domoic acid, reaching 0.05 pg/L. Presence of Alexandrium ostenfeldii could be linked to an increase in spirolides, up to 56.4 pg/L in the particulate phase. Generally, the majority of detected dissolved toxins followed the succession pattern of the particulate toxins with a delay in time. Our results further show that Arctic waters are a suitable habitat for various toxin producers and that the strong seasonality of this environment is reflected by changing abundances of different toxins that pose a potential threat to the ecosystem and its beneficiaries.

Chemical and morphological defenses of Pseudo-nitzschia multiseries in response to zooplankton grazing.

Pseudo-nitzschia species frequently blooms in coastal waters, and some species are able to produce the toxin domoic acid (DA), hereby causing harm to the marine ecosystem and humans. Laboratory studies were conducted to investigate the influence of different levels of grazing pressure on the morphological and chemical response (in terms of cellular DA production) of Pseudo-nitzschia. Subsequently, zooplankton grazer responses to these defenses were examined. The cellular DA content of P. multiseries ranged from 0.11-0.27 pg cell-1 without grazers, and increased up to 44% with the presence of grazers (Artemia nauplii) and with grazer concentration. Grazing also affected the density of P. multiseries chains and average chain length which became ~25% higher and ~8% longer, respectively, than without grazers. These effects could either be caused by size-dependent grazing or by grazer-cue-induced effects on chain formation. A negative correlation between cellular DA content in P. multiseries and clearance and/or ingestion rates of Artemia nauplii indicate that DA might have a negative effect on the grazing of Artemia nauplii. Such interaction might result in a decrease in grazing pressure on toxic blooming species, like P. multiseries, and hence potentially a prolonged bloom. This indicates that the interaction between toxic diatoms and grazers may have implications on aquatic food web structure and the progression of Pseudo-nitzschia blooms.

Diversity and emendation of the genus Planktoniella (Bacillariophyceae), with descriptions of P. tubulata sp. nov. and P. trifurcata sp. nov.

For the first time, LSU and SSU sequences were obtained from four species of the marine planktonic diatom Planktoniella. Samples were collected and cultured from Chinese coastal waters, and morphological observations were made using light and scanning electron microscopy. Combined morphological and DNA sequence data revealed two new species herein described as Planktoniella tubulata and Planktoniella trifurcata. Planktoniella tubulata is characterized by the prominent external tubes of two rimoportulae and the long external tubes of the marginal fultoportulae. The latter are organized regularly in a ring, externally on the mantle, and protrude parallel to the valvar plane. Planktoniella trifurcata is unique in having mucilaginous extensions that usually expand into three lobes, and external extensions of the marginal fultoportulae being either tubes or spines. In the phylogenetic analyses inferred from SSU and LSU sequences, the four analyzed Planktoniella taxa formed a well-supported monophyletic group. A suite of three characters, mucilage membranes or wings, two marginal rimoportulae, and mantle ribs are diagnostic for Planktoniella. Based on these detailed ultrastructural observations, the description of Planktoniella is emended.

Harmful algal blooms and their effects in coastal seas of Northern Europe.

Harmful algal blooms (HAB) are recurrent phenomena in northern Europe along the coasts of the Baltic Sea, Kattegat-Skagerrak, eastern North Sea, Norwegian Sea and the Barents Sea. These HABs have caused occasional massive losses for the aquaculture industry and have chronically affected socioeconomic interests in several ways. This status review gives an overview of historical HAB events and summarises reports to the Harmful Algae Event Database from 1986 to the end of year 2019 and observations made in long term monitoring programmes of potentially harmful phytoplankton and of phycotoxins in bivalve shellfish. Major HAB taxa causing fish mortalities in the region include blooms of the prymnesiophyte Chrysochromulina leadbeateri in northern Norway in 1991 and 2019, resulting in huge economic losses for fish farmers. A bloom of the prymesiophyte Prymnesium polylepis (syn. Chrysochromulina polylepis) in the Kattegat-Skagerrak in 1988 was ecosystem disruptive. Blooms of the prymnesiophyte Phaeocystis spp. have caused accumulations of foam on beaches in the southwestern North Sea and Wadden Sea coasts and shellfish mortality has been linked to their occurrence. Mortality of shellfish linked to HAB events has been observed in estuarine waters associated with influx of water from the southern North Sea. The first bloom of the dictyochophyte genus Pseudochattonella was observed in 1998, and since then such blooms have been observed in high cell densities in spring causing fish mortalities some years. Dinoflagellates, primarily Dinophysis spp., intermittently yield concentrations of Diarrhetic Shellfish Toxins (DST) in blue mussels, Mytilus edulis, above regulatory limits along the coasts of Norway, Denmark and the Swedish west coast. On average, DST levels in shellfish have decreased along the Swedish and Norwegian Skagerrak coasts since approximately 2006, coinciding with a decrease in the cell abundance of D. acuta. Among dinoflagellates, Alexandrium species are the major source of Paralytic Shellfish Toxins (PST) in the region. PST concentrations above regulatory levels were rare in the Skagerrak-Kattegat during the three decadal review period, but frequent and often abundant findings of Alexandrium resting cysts in surface sediments indicate a high potential risk for blooms. PST levels often above regulatory limits along the west coast of Norway are associated with A. catenella (ribotype Group 1) as the main toxin producer. Other Alexandrium species, such as A. ostenfeldii and A. minutum, are capable of producing PST among some populations but are usually not associated with PSP events in the region. The cell abundance of A. pseudogonyaulax, a producer of the ichthyotoxin goniodomin (GD), has increased in the Skagerrak-Kattegat since 2010, and may constitute an emerging threat. The dinoflagellate Azadinium spp. have been unequivocally linked to the presence of azaspiracid toxins (AZT) responsible for Azaspiracid Shellfish Poisoning (AZP) in northern Europe. These toxins were detected in bivalve shellfish at concentrations above regulatory limits for the first time in Norway in blue mussels in 2005 and in Sweden in blue mussels and oysters (Ostrea edulis and Crassostrea gigas) in 2018. Certain members of the diatom genus Pseudo-nitzschia produce the neurotoxin domoic acid and analogs known as Amnesic Shellfish Toxins (AST). Blooms of Pseudo-nitzschia were common in the North Sea and the Skagerrak-Kattegat, but levels of AST in bivalve shellfish were rarely above regulatory limits during the review period. Summer cyanobacteria blooms in the Baltic Sea are a concern mainly for tourism by causing massive fouling of bathing water and beaches. Some of the cyanobacteria produce toxins, e.g. Nodularia spumigena, producer of nodularin, which may be a human health problem and cause occasional dog mortalities. Coastal and shelf sea regions in northern Europe provide a key supply of seafood, socioeconomic well-being and ecosystem services. Increasing anthropogenic influence and climate change create environmental stressors causing shifts in the biogeography and intensity of HABs. Continued monitoring of HAB and phycotoxins and the operation of historical databases such as HAEDAT provide not only an ongoing status report but also provide a way to interpret causes and mechanisms of HABs.

Morphological and genetic analyses of Ostreopsis (Dinophyceae, Gonyaulacales, Ostreopsidaceae) species from Vietnamese waters with a re-description of the type species, O. siamensis.

Identification of species of the dinoflagellate genus Ostreopsis is difficult because several species have been poorly described, others misidentified in the literature, and the type species, O. siamensis, has not been described by contemporary taxonomic methods. In the present study, it is argued that Ostreopsis sp. 6 as described by previous authors is similar to the type species, and we offer an emended description of O. siamensis by LM, SEM, and molecular analyses of nuclear LSU and ITS rDNA based on material collected a few hundred kilometers from the type locality in the Gulf of Thailand and along the Vietnamese east coast. Ostreopsis siamensis is genetically different from the species reported as O. cf. siamensis in the literature and the latter should be described as a separate species. It is also concluded that with the poor knowledge of the morphological variability of many species of Ostreopsis, O. siamensis may not be distinguished from other similar-sized species by its morphological features, and hence molecular data are needed for reliable identification. The species Ostreopsis lenticularis and Ostreopsis cf. ovata were also found and described.

First Evidence of the Toxin Domoic Acid in Antarctic Diatom Species.

The Southern Ocean is one of the most productive ecosystems in the world. It is an area heavily dependent on marine primary production and serving as a feeding ground for numerous seabirds and marine mammals. Therefore, the phytoplankton composition and presence of toxic species are of crucial importance. Fifteen monoclonal strains of Pseudo-nitzschia subcurvata, a diatom species endemic to the Southern Ocean, were established, which were characterized by morphological and molecular data and then analysed for toxin content. The neurotoxins domoic acid and iso-domoic acid C were present in three of the strains, which is a finding that represents the first evidence of these toxins in strains from Antarctic waters. Toxic phytoplankton in Antarctic waters are still largely unexplored, and their effects on the ecosystem are not well understood. Considering P. subcurvata's prevalence throughout the Southern Ocean, these results highlight the need for further investigations of the harmful properties on the Antarctic phytoplankton community as well as the presence of the toxins in the Antarctic food web, especially in the light of a changing climate.

Limits to the cellular control of sequestered cryptophyte prey in the marine ciliate Mesodinium rubrum.

The marine ciliate Mesodinium rubrum is famous for its ability to acquire and exploit chloroplasts and other cell organelles from some cryptophyte algal species. We sequenced genomes and transcriptomes of free-swimming Teleaulax amphioxeia, as well as well-fed and starved M. rubrum in order to understand cellular processes upon sequestration under different prey and light conditions. From its prey, the ciliate acquires the ability to photosynthesize as well as the potential to metabolize several essential compounds including lysine, glycan, and vitamins that elucidate its specific prey dependency. M. rubrum does not express photosynthesis-related genes itself, but elicits considerable transcriptional control of the acquired cryptophyte organelles. This control is limited as light-dependent transcriptional changes found in free-swimming T. amphioxeia got lost after sequestration. We found strong transcriptional rewiring of the cryptophyte nucleus upon sequestration, where 35% of the T. amphioxeia genes were significantly differentially expressed within well-fed M. rubrum. Qualitatively, 68% of all genes expressed within well-fed M. rubrum originated from T. amphioxeia. Quantitatively, these genes contributed up to 48% to the global transcriptome in well-fed M. rubrum and down to 11% in starved M. rubrum. This tertiary endosymbiosis system functions for several weeks, when deprived of prey. After this point in time, the ciliate dies if not supplied with fresh prey cells. M. rubrum represents one evolutionary way of acquiring photosystems from its algal prey, and might represent a step on the evolutionary way towards a permanent tertiary endosymbiosis.

Two New and Nontoxigenic Pseudo-nitzschia species (Bacillariophyceae) from Chinese Southeast Coastal Waters.

To explore the species diversity and toxin profile of Pseudo-nitzschia, monoclonal strains were established from Chinese southeast coastal waters. The morphology was examined under light and transmission electron microscopy. The internal transcribed spacer region of ribosomal DNA was sequenced for phylogenetic analyses, and the secondary structure of ITS2 was predicted and compared among allied taxa. A combination of morphological and molecular data showed the presence of two new species, Pseudo-nitzschia hainanensis sp. nov. and Pseudo-nitzschia taiwanensis sp. nov. Pseudo-nitzschia hainanensis was characterized by a dumpy-lanceolate valve with slightly blunt apices and a central nodule, as well as striae comprising two rows of poroids. Pseudo-nitzschia taiwanensis was characterized by a slender-lanceolate valve, and striae comprising one row of split poroids. The poroid structure mainly comprised two sectors. Both taxa constituted their own monophyletic lineage in the phylogenetic analyses inferred from ITS2 rDNA and were well differentiated from other Pseudo-nitzschia species. Morphologically, P. hainanensis and P. taiwanensis could be assigned to the Pseudo-nitzschia delicatissima and the Pseudo-nitzschia pseudodelicatissima complex, respectively. Particulate domoic acid was measured using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), but no detectable pDA was found. With the description of the two new species, the species diversity of genus Pseudo-nitzschia reaches 58 worldwide, among which 31 have been recorded from Chinese coastal waters.

Occurrence of Pseudo-nitzschia species and associated domoic acid production along the Guangdong coast, South China Sea.

The diatom genus Pseudo-nitzschia, which has been associated with amnesic shellfish poisoning events globally, is also one of the key harmful microalga groups in Guangdong coastal waters, off the north coast of the South China Sea. In order to explore the diversity and toxigenic characteristics, Pseudo-nitzschia isolates were established. Based on a combination of morphological and molecular features, in total 26 different Pseudo-nitzschia taxa were identified, including two new species, P. uniseriata H.C. Dong & Yang Li and P. yuensis H.C. Dong & Yang Li. Morphologically, P. uniseriata is unique by having striae mainly comprising one row of poroids, which are simple without divided hymen internally, and each poroid containing one, seldom two sectors. Pseudo-nitzschia yuensis is characterized by having striae comprising one to two rows of poroids. In biseriate striae, the poroids are polygonal and irregularly distributed, and a discontinuous row of poroids may be present in the middle. In uniseriate striae, the poroids usually contain 1-5 sectors. Both taxa are well differentiated from other Pseudo-nitzschia species in phylogenetic analyses inferred from ITS2 sequence-structure information. Pseudo-nitzschia uniseriata is sister to P. lineola, whereas P. yuensis forms a group together with P. micropora and P. delicatissima. When comparing ITS2 secondary structure, two hemi-compensatory base change (HCBCs) are found between P. uniseriata and P. lineola. One compensatory base change (CBC) and four HCBCs are found between P. yuensis and P. delicatissima, and there is one CBC and five HCBCs between P. yuensis and P. micropora. The ability of cultured strains to produce particulate DA (pDA) revealed production of pDA in twenty-nine strains belonging to seven species: P. bipertita, P. caciantha, P. cuspidata, P. fraudulenta, P. fukuyoi, P. lundholmiae and P. multiseries. This is the first report of P. bipertita being toxic, with pDA content of 15.6 ± 2.1 fg cell-1. The presence of brine shrimps significantly increased pDA content in P. cuspidata, P. fukuyoi, P. lundholmiae and P. multiseries 1.4 to 7 times, and induced pDA production in P. fraudulenta from below detection limit to 17.5 ± 1.6 fg cell-1. The highest pDA concentration, 4830.5 ± 120.3 fg cell-1, was detected in P. multiseries, a level much lower than previous reports on P. multiseries from North America and Europe. Overall, the cellular toxin levels in Pseudo-nitzschia spp. were low in Guangdong coastal isolates.

Biomonitoring of Polycyclic Aromatic Hydrocarbon Deposition in Greenland Using Historical Moss Herbarium Specimens Shows a Decrease in Pollution During the 20th Century.

Although most point sources of persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbons (PAHs), are at lower latitudes, the Arctic region is contaminated. In particular, PAHs now dominate the POP body burden of the region's marine biota at the lower trophic levels. Greenlandic Inuits have the most elevated levels of POPs in their blood compared to any other population, due to their consumption of seal meat and other marine mammals. PAHs, the by-products of the incomplete combustion of petroleum products, are known carcinogens and have been shown to affect the immune system, reproduction, endocrine functions, and the nervous system. With industrial activities and climate change set to increase local PAH emissions, it is paramount to document changes in atmospheric PAH deposition to further investigate PAH exposure in the region and attribute contaminations to their sources. As a measure of atmospheric pollution, we sampled bryophyte herbarium specimens of three common and widespread species collected in Greenland between the 1920s and 1970s after which time new collections were not available. They were analyzed for 19 PAHs using GC-MS (gas chromatography mass spectrometry). The presence of more low-molecular-weight PAHs than high-molecular-weight PAHs is evidence that the PAH contamination in Greenland is due to long-range transport rather than originating from local sources. The results show peaks in PAH atmospheric deposition in the first part of the 19th century followed by a trend of decrease, which mirror global trends in atmospheric pollution known from those periods. PAHs associated with wood and fossil-fuel combustion decrease in the 1970s coinciding with the disappearance of charcoal pits and foundries in Europe and North America, and a shift away from domestic heating with wood during the 19th century. The results highlight the value of bryophytes as bioindicators to measure PAH atmospheric pollution as well as the unrealized potential of herbaria as historical records of environmental change.