Effect of temperature on growth and yessotoxin production of Protoceratium reticulatum and Lingulodinium polyedra (Dinophyceae) isolates from the Portuguese coast (NE Atlantic).

The dinoflagellates Protoceratium reticulatum and Lingulodinium polyedra are potential yessotoxin (YTX) producers, which have been associated with blooms responsible for economic, social, and ecological impacts around the world. They occur in Iberian waters, but in this region, little is known of their ecophysiology and toxin profiles. This study investigated the growth and toxin production of two strains of each species, from the Portuguese coast, at 15 °C, 19 °C, and 23 °C. Growth curves showed higher growth rates at 19 °C, for both species. YTX and three analogs (homo YTX; 45-OH YTX; 45-OH homo YTX) were investigated by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS), and the presence of other analogs was investigated by Liquid Chromatography-High-Resolution Mass Spectrometry (LC-HRMS). No evidence of toxin production was found in L. polyedra. By contrast, YTX and 45,55-diOH-YTX were detected in both strains of P. reticulatum. These results confirm P. reticulatum as a source of yessotoxins along the Portuguese coast and add to the observed high intraspecific variability on YTX production of both species, at a global scale.

New Vectors of TTX Analogues in the North Atlantic Coast: The Edible Crabs Afruca tangeri and Carcinus maenas.

Tetrodotoxin (TTX) and its analogues are naturally occurring toxins historically responsible for human poisoning fatalities in Eastern Asia. It is typically linked to the consumption of pufferfish and, to a lesser extent, marine gastropods and crabs. In the scope of a comprehensive project to understand the prevalence of emergent toxins in edible marine organisms, we report, for the first time, the detection of TTX analogues in the soft tissues of edible crabs, the European fiddler crab (Afruca tangeri) and green crab (Carcinus maenas), harvested in southern Portugal. No TTX was detected in the analyzed samples. However, three TTX analogues were detected-an unknown TTX epimer, deoxyTTX, and trideoxyTTX. These three analogues were found in the European fiddler crab while only trideoxyTTX was found in the green crab, suggesting that the accumulation of TTX analogues might be influenced by the crabs' different feeding ecology. These results highlight the need to widely monitor TTX and its analogues in edible marine species in order to provide adequate information to the European Food Safety Authority and to protect consumers.

Gymnodinium catenatum Paralytic Shellfish Toxin Production and Photobiological Responses under Marine Heat Waves.

Marine heatwaves (MHWs) have doubled in frequency since the 1980s and are projected to be exacerbated during this century. MHWs have been shown to trigger harmful algal blooms (HABs), with severe consequences to marine life and human populations. Within this context, this study aims to understand, for the first time, how MHWs impact key biological and toxicological parameters of the paralytic shellfish toxin (PST) producer Gymnodinium catenatum, a dinoflagellate inhabiting temperate and tropical coastal waters. Two MHW were simulated-category I (i.e., peak: 19.9 °C) and category IV (i.e., peak: 24.1 °C)-relative to the estimated baseline in the western coast of Portugal (18.5 °C). No significant changes in abundance, size, and photosynthetic efficiency were observed among treatments. On the other hand, chain-formation was significantly reduced under category IV MHW, as was PSP toxicity and production of some PST compounds. Overall, this suggests that G. catenatum may have a high tolerance to MHWs. Nevertheless, some sublethal effects may have occurred since chain-formation was affected, suggesting that these growth conditions may be sub-optimal for this population. Our study suggests that the increase in frequency, intensity, and duration of MHWs may lead to reduced severity of G. catenatum blooms.

Tissue accumulation of tetrodotoxin (TTX) and analogues in trumpet shell Charonia lampas.

Tetrodotoxin (TTX) is a potent neurotoxin responsible for a human intoxication event in Spain associated with the consumption of trumpet shell Charonia lampas. In Europe, TTX is not regulated or monitored, and there is little knowledge about its presence in seafood. Here, we investigated the tissue distribution of TTX and analogues in three specimens of trumpet shell C. lampas bought in a market in southern Portugal. Toxin concentration was above the EFSA recommended limit in the non-edible tissues of all specimens and within the limit in the edible tissues of two specimens. 4,9-AnhydroTTX and 13 additional TTX analogues were detected in tissues, the most abundant being anhydrotrideoxyTTX and trideoxyTTX. These results suggest that although thorough evisceration may lower the amount of TTX consumed, it may not be sufficient to ensure consumer safety. Regular monitoring of TTX and analogues in trumpet shell and other edible gastropods is therefore recommended to avoid poisoning incidents.

Chemical composition and species identification of microalgal biomass grown at pilot-scale with municipal wastewater and CO2 from flue gases.

The production potential of a locally isolated Chlorella vulgaris strain and a local green-algae consortium, used in municipal wastewater treatment combined with CO2 sequestration from flue gases, was evaluated for the first time by comparing the elemental and biochemical composition and heating value of the biomass produced. The microalgae were grown in outdoor pilot-scale ponds under subarctic summer conditions. The impact of cultivation in a greenhouse climate was also tested for the green-algae consortium; additionally, the variation in species composition over time in the three ponds was investigated. Our results showed that the biomass produced in the consortium/outdoor pond had the greatest potential for bioenergy production because both its carbohydrates and lipids contents were significantly higher than the biomasses from the consortium/greenhouse and C. vulgaris/outdoor ponds. Although greenhouse conditions significantly increased the consortium biomass's monounsaturated fatty acid content, which is ideal for biodiesel production, an undesirable increase in ash and chemical elements, as well as a reduction in heating value, were also observed. Thus, the placement of the pond inside a greenhouse did not improve the production potential of the green-algae consortium biomass in the current study infrastructure and climate conditions.

LC-HRMS Profiling of Paralytic Shellfish Toxins in Mytilus galloprovincialis after a Gymnodinium catenatum Bloom.

Saxitoxin and its more than 50 analogues are a group of naturally occurring neurotoxins collectively designated as paralytic shellfish toxins (PSTs). PSTs are toxic to humans and maximum legal limits in seafood have been implemented by regulatory authorities worldwide. In the European Union, monitoring of PSTs is performed using the AOAC Official Method 2005.06, based on liquid chromatography coupled with fluorescence detection (LC- FLD). However, this method has been suggested to not effectively detect the emerging C-11 hydroxyl (M-toxins) and benzoate (GC-toxins) analogues, with these analogues currently not being surveyed in monitoring programs. In this study, a liquid chromatography-high resolution mass spectrometry (LC-HRMS) method was used to search for these emerging PSTs in mussels, Mytilus galloprovincialis, contaminated following an intense Gymnodinium catenatum bloom in the Tagus estuary (Lisbon, Portugal). Five M-toxins (M1, M2, M6, dcM6, and dcM10), but no GC-toxins, were detected in the mussels' whole-soft body tissue. Moreover, the classical PSTs (C1 to C4, GTX 4 to GTX6, dcGTX1 to dcGTX4, dcSTX, dcNEO, and STX) were also found and comprised the largest fraction of the PSTs' profile. The presence of unregulated PSTs in edible mussel samples suggests potential seafood safety risks and urges further research to determine the frequency of these analogues in seafood and their contribution to toxicity.

Interspecific Interactions Drive Nonribosomal Peptide Production in Nodularia spumigena.

Nodularia spumigena is a bloom-forming cyanobacterium that produces several classes of nonribosomal peptides (NRPs) that are biologically active; however, the ecological roles of specific NRPs remain largely unknown. Here, we explored the involvement of NRPs produced by N. spumigena in interspecific interactions by coculturing the cyanobacterium and its algal competitors, the diatom Phaeodactylum tricornutum and the cryptomonad Rhodomonas salina, and measuring NRP levels and growth responses in all three species. Contrary to the expected growth suppression in the algae, it was N. spumigena that was adversely affected by the diatom, while the cryptomonad had no effect. Reciprocal effects of N. spumigena on the algae were manifested as the prolonged lag phase in R. salina and growth stimulation in P. tricornutum; however, these responses were largely attributed to elevated pH and not to specific NRPs. Nevertheless, the NRP levels in the cocultures were significantly higher than in the monocultures, with an up to 5-fold upregulation of cell-bound nodularins and exudation of nodularin and anabaenopeptin. Thus, chemically mediated interspecific interactions can promote NRP production and release by cyanobacteria, resulting in increased input of these compounds into the water. IMPORTANCE NRPs were involved in growth responses of both cyanobacteria and algae; however, the primary driver of the growth trajectories was high pH induced by N. spumigena. Thus, the pH-mediated inhibition of eukaryotic phytoplankton may be involved in the bloom formation of N. spumigena. We also report, for the first time, the reciprocal growth inhibition of N. spumigena by diatoms resistant to alkaline conditions. As all species in this study can co-occur in the Baltic Sea during summer, these findings are highly relevant for understanding ecological interactions in planktonic communities in this and other systems experiencing regular cyanobacteria blooms.

Quantitation Overcoming Matrix Effects of Lipophilic Toxins in Mytilus galloprovincialis by Liquid Chromatography-Full Scan High Resolution Mass Spectrometry Analysis (LC-HR-MS).

The analysis of marine lipophilic toxins in shellfish products still represents a challenging task due to the complexity and diversity of the sample matrix. Liquid chromatography coupled with mass spectrometry (LC-MS) is the technique of choice for accurate quantitative measurements in complex samples. By combining unambiguous identification with the high selectivity of tandem MS, it provides the required high sensitivity and specificity. However, LC-MS is prone to matrix effects (ME) that need to be evaluated during the development and validation of methods. Furthermore, the large sample-to-sample variability, even between samples of the same species and geographic origin, needs a procedure to evaluate and control ME continuously. Here, we analyzed the toxins okadaic acid (OA), dinophysistoxins (DTX-1 and DTX-2), pectenotoxin (PTX-2), yessotoxin (YTX) and azaspiracid-1 (AZA-1). Samples were mussels (Mytilus galloprovincialis), both fresh and processed, and a toxin-free mussel reference material. We developed an accurate mass-extracted ion chromatogram (AM-XIC) based quantitation method using an Orbitrap instrument, evaluated the ME for different types and extracts of mussel samples, characterized the main compounds co-eluting with the targeted molecules and quantified toxins in samples by following a standard addition method (SAM). An AM-XIC based quantitation of lipophilic toxins in mussel samples using high resolution and accuracy full scan profiles (LC-HR-MS) is a good alternative to multi reaction monitoring (MRM) for instruments with HR capabilities. ME depend on the starting sample matrix and the sample preparation. ME are particularly strong for OA and related toxins, showing values below 50% for fresh mussel samples. Results for other toxins (AZA-1, YTX and PTX-2) are between 75% and 110%. ME in unknown matrices can be evaluated by comparing their full scan LC-HR-MS profiles with those of known samples with known ME. ME can be corrected by following SAM with AM-XIC quantitation if necessary.

Competitive interactions as a mechanism for chemical diversity maintenance in Nodularia spumigena.

Nodularia spumigena is a bloom-forming diazotrophic cyanobacterium inhabiting brackish waters worldwide. This species produces non-ribosomal peptides (NRPs), including the hepatotoxin nodularin, often referred to as cyanotoxin. Several known classes of NRPs have various biological activities, although their modes of action are poorly understood. In the Baltic N. spumigena, there is a high NRP chemodiversity among strains, allowing their grouping in specific chemotypes and subgroups. Therefore, it is relevant to ask whether the NRP production is affected by intraspecific interactions between the co-existing strains. Using a novel approach that combines culture technique and liquid chromatography-tandem mass spectrometry for the NRP analysis, we examined N. spumigena strains under mono- and co-culture conditions. The test strains were selected to represent N. spumigena belonging to the same or different chemotype subgroups. In this setup, we observed physiological and metabolic responses in the test strains grown without cell contact. The changes in NRP levels to co-culture conditions were conserved within a chemotype subgroup but different between the subgroups. Our results suggest that intraspecific interactions may promote a chemical diversity in N. spumigena population, with higher NRP production compared to a single-strain population. Studying allelochemical signalling in this cyanobacterium is crucial for understanding toxicity mechanisms and plankton community interactions in the Baltic Sea and other aquatic systems experiencing regular blooms.

Fate of active pharmaceutical ingredients in a northern high-rate algal pond fed with municipal wastewater.

Active pharmaceutical ingredients (APIs) are vital to human health and welfare, but following therapeutic use, they may pose a potential ecological risk if discharged into the environment. Today's conventional municipal wastewater treatment plants are not designed to remove APIs specifically, and various techniques, preferably cost-effective and environmentally friendly, are being developed and evaluated. Microalgae-based treatment of wastewater is a sustainable and low-cost approach to remove nutrients and emerging contaminants. In this study, a North Sweden high-rate algal pond (HRAP) using municipal untreated wastewater as medium, was investigated in terms of API distribution and fate. Three six-day batches were prepared during 18 days and a total of 36 APIs were quantified within the HRAP of which 14 were removed from the aqueous phase above 50% and seven removed above 90% of their initial concentrations. Twelve APIs of a hydrophobic nature were mostly associated with the algal biomass that was harvested at the end of each batch. HRAPs treatment successfully removed 69% of studied APIs (25 of 36 studied) in six day time. The distribution of various APIs between the aqueous phase and biomass suggested that several removal mechanisms may occur, such as hydrophobicity driven removal, passive biosorption and active bioaccumulation.

Microalgal growth, nitrogen uptake and storage, and dissolved oxygen production in a polyculture based-open pond fed with municipal wastewater in northern Sweden.

Microalgal-based wastewater treatment and CO2 sequestration from flue gases with subsequent biomass production represent a low-cost, eco-friendly, and effective procedure of removing nutrients and other pollutants from wastewater and assists in the decrease of greenhouse gas emissions. Thus, it supports a circular economy model. This is based on the ability of microalgae to utilise inorganic nutrients, mainly nitrogen and phosphorous, as well as organic and inorganic carbon, for their growth, and simultaneously reduce these substances in the water. However, the production of microalgae biomass under outdoor cultivation is dependent on several abiotic and biotic factors, which impact its profitability and sustainability. Thus, this study's goal was to evaluate the factors affecting the production of microalgae biomass on pilot-scale open raceway ponds under Northern Sweden's summer conditions with the help of a mathematical model. For this purpose, a microalgae consortium and a monoculture of Chlorella vulgaris were used to inoculate outdoor open raceway ponds. In line with the literature, higher biomass concentrations and nutrient removals were observed in ponds inoculated with the microalgae consortium. Our model, based on Droop's concept of macronutrient quotas inside the cell, corresponded well to the experimental data and, thus, can successfully be applied to predict biomass production, nitrogen uptake and storage, and dissolved oxygen production in microalgae consortia.

Chemical profiling of the Arctic sea lettuce Ulva lactuca (Chlorophyta) mass-cultivated on land under controlled conditions for food applications.

The increasing use of seaweeds in European cuisine led to cultivation initiatives funded by the European Union. Ulva lactuca, commonly known as sea lettuce, is a fast growing seaweed in the North Atlantic that chefs are bringing into the local cuisine. Here, different strains of Arctic U. lactuca were mass-cultivated under controlled conditions for up to 10 months. We quantified various chemical constituents associated with both health benefits (carbohydrates, protein, fatty acids, minerals) and health risks (heavy metals). Chemical analyses showed that long-term cultivation provided biomass of consistently high food quality and nutritional value. Concentrations of macroelements (C, N, P, Ca, Na, K, Mg) and micronutrients (Fe, Zn, Co, Mn, I) were sufficient to contribute to daily dietary mineral intake. Heavy metals (As, Cd, Hg and Pb) were found at low levels to pose health risk. The nutritional value of Ulva in terms of carbohydrates, protein and fatty acids is comparable to some selected fruits, vegetables, nuts and grains.

Quantification and characterisation of fatty acid methyl esters in microalgae: Comparison of pretreatment and purification methods.

A systematic qualitative and quantitative analysis of fatty acid methyl esters (FAMEs) is crucial for microalgae species selection for biodiesel production. The aim of this study is to identify the best method to assess microalgae FAMEs composition and content. A single-step method, was tested with and without purification steps-that is, separation of lipid classes by thin-layer chromatography (TLC) or solid-phase extraction (SPE). The efficiency of a direct transesterification method was also evaluated. Additionally, the yield of the FAMEs and the profiles of the microalgae samples with different pretreatments (boiled in isopropanol, freezing, oven-dried and freeze-dried) were compared. The application of a purification step after lipid extraction proved to be essential for an accurate FAMEs characterisation. The purification methods, which included TLC and SPE, provided superior results compared to not purifying the samples. Freeze-dried microalgae produced the lowest FAMEs yield. However, FAMEs profiles were generally equivalent among the pretreatments.

Native (Ruditapes decussatus) and non-indigenous (R. philippinarum) shellfish species living in sympatry: Comparison of regulated and non-regulated biotoxins accumulation.

The native Ruditapes decussatus and the non-indigenous Ruditapes philippinarum are an important target of shellfish industries. The aim of this study was to compare an invader with a native species living in sympatry in the view of marine biotoxins accumulation. Samples were analysed for regulated and non-regulated biotoxins. The consistently occurrence of okadaic acid-group toxins and BMAA, may cause human health problems and economical losses. A strong positive relationship was observed between species, with significantly higher DSP toxicity in R. decussatus. Similar toxin profiles dominated by DTX3 in both species suggests similar metabolic pathways. Lower DSP toxicity in R. philippinarum may favour their cultivation, but a tendency for higher levels of the non-regulated BMAA was observed, indicating risks for consumers that are not monitored. This study highlights the need to better understand the physiological responses and adaptations allowing similar species exposed to the same conditions to present different toxicity levels.

The effect of exogenous ß-N-methylamino-l-alanine (BMAA) on the diatoms Phaeodactylum tricornutum and Thalassiosira weissflogii.

ß-N-methylamino-l-alanine (BMAA), a non-protein amino acid with neurodegenerative features, is known to be produced by cyanobacteria, diatoms and a dinoflagellate. BMAA research has intensified over the last decade, and knowledge has been gained about its bioaccumulation in aquatic and terrestrial ecosystems, toxic effects in model organisms and neurotoxicity in vivo and in vitro. Nevertheless, knowledge of the actual physiological role of BMAA in the producing species or of the ecological factors that regulate BMAA production is still lacking. A few studies propose that BMAA functions to signal nitrogen depletion in cyanobacteria. To investigate whether BMAA might have a similar role in diatoms, two diatom species - Phaeodactylum tricornutum and Thalassiosira weissflogii - were exposed to exogenous BMAA at environmental relevant concentrations, i.e. 0.005, 0.05 and 0.5µM. BMAA was taken up in a concentration dependent manner in both species in the BMAA free fraction and in the protein fraction of T. weissflogii. As a result of the treatments, the diatom cells at some of the time points and at some of the BMAA concentrations exhibited lower concentrations of chlorophyll a and protein, in comparison to controls. At the highest (0.5µM) concentration of BMAA, extracellular ammonia was found in the media of both species at all time points. These results suggest that BMAA interferes with nitrogen metabolism in diatoms, possibly by inhibiting ammonium assimilation via the GS/GOGAT pathway.

BMAA extraction of cyanobacteria samples: which method to choose?

ß-N-Methylamino-L-alanine (BMAA), a neurotoxin reportedly produced by cyanobacteria, diatoms and dinoflagellates, is proposed to be linked to the development of neurological diseases. BMAA has been found in aquatic and terrestrial ecosystems worldwide, both in its phytoplankton producers and in several invertebrate and vertebrate organisms that bioaccumulate it. LC-MS/MS is the most frequently used analytical technique in BMAA research due to its high selectivity, though consensus is lacking as to the best extraction method to apply. This study accordingly surveys the efficiency of three extraction methods regularly used in BMAA research to extract BMAA from cyanobacteria samples. The results obtained provide insights into possible reasons for the BMAA concentration discrepancies in previous publications. In addition and according to the method validation guidelines for analysing cyanotoxins, the TCA protein precipitation method, followed by AQC derivatization and LC-MS/MS analysis, is now validated for extracting protein-bound (after protein hydrolysis) and free BMAA from cyanobacteria matrix. BMAA biological variability was also tested through the extraction of diatom and cyanobacteria species, revealing a high variance in BMAA levels (0.0080-2.5797 µg g(-1) DW).

Biotransfer of ß-N-methylamino-L-alanine (BMAA) in a eutrophicated freshwater lake.

ß-N-Methylamino-L-alanine (BMAA), a neurotoxic non-protein amino acid, plays a significant role as an environmental risk factor in neurodegenerative diseases, such as amyotrophic lateral sclerosis. BMAA producers occur globally, colonizing almost all habitats and represent species from distinct phytoplanktonic groups, i.e., cyanobacteria, diatoms, and dinoflagellates. Bioaccumulation of BMAA in invertebrate and vertebrate organisms has also been registered around the globe. In the Baltic Sea, BMAA has been detected in several commercial fish species, raising the question of the bioaccumulation of BMAA in Swedish limnic systems. Here we find the presence of BMAA in water samples from Lake Finjasjön and identify its bioaccumulation patterns in both plankti-benthivorous and piscivorous fish, according to fish species, total weight, gender, and season of collection. For the first time, a large number of fish individuals were used in order to draw conclusions on BMAA bioaccumulation in a closed ecological community based on a statistical approach. We may, therefore, conclude that feeding patterns (plankti-benthivorous) and increased age of fish may lead to a higher tissue concentration of BMAA.

BMAA in shellfish from two Portuguese transitional water bodies suggests the marine dinoflagellate Gymnodinium catenatum as a potential BMAA source.

The neurotoxin ß-N-methylamino-l-alanine (BMAA) and its putative role in multiple neurodegenerative diseases have been intensely studied since 2005 when the toxin was discovered to be produced by worldwide-distributed cyanobacterial species inhabiting terrestrial, marine, brackish, and freshwater ecosystems. Recently, BMAA production was also associated with one eukaryotic group, namely, diatoms, raising questions about its production by other phytoplanktonic groups. To test for BMAA bioavailability in ecosystems where abundant phytoplanktonic blooms regularly occur, samples of filter-feeding shellfish were collected in two Portuguese transitional water bodies. BMAA content in cockles (Cerastoderma edule) collected weekly between September and November 2009 from Ria de Aveiro and at least once a month from May to November from Ria Formosa, fluctuated from 0.079±0.055 to 0.354±0.066µg/g DW and from below the limit of detection to 0.434±0.110µg/g DW, respectively. Simultaneously to BMAA occurrence in cockles, paralytic shellfish toxins were detected in shellfish as a result of Gymnodinium catenatum blooms indicating a possible link between this marine dinoflagellate and BMAA production. Moreover, considerable high BMAA levels, 0.457±0.186µg/g DW, were then determined in a laboratory grown culture of G. catenatum. This work reveals for the first time the presence of BMAA in shellfish from Atlantic transitional water bodies and consubstantiate evidences of G. catenatum as one of the main sources of BMAA in these ecosystems.

Diatoms: a novel source for the neurotoxin BMAA in aquatic environments.

Amyotrophic lateral sclerosis (ALS) or Lou Gehrig's disease is a neurological disorder linked to environmental exposure to a non-protein amino acid, ß-N-methylamino-L-alanine (BMAA). The only organisms reported to be BMAA-producing, are cyanobacteria--prokaryotic organisms. In this study, we demonstrate that diatoms--eukaryotic organisms--also produce BMAA. Ultra-high-performance liquid chromatography coupled with tandem mass spectrometry revealed the occurrence of BMAA in six investigated axenic diatom cultures. BMAA was also detected in planktonic field samples collected on the Swedish west coast that display an overrepresentation of diatoms relative to cyanobacteria. Given the ubiquity of diatoms in aquatic environments and their central role as primary producers and the main food items of zooplankton, the use of filter and suspension feeders as livestock fodder dramatically increases the risk of human exposure to BMAA-contaminated food.