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Dinoflagellate species that form some of the most frequent toxic blooms are also bioluminescent, yet the two traits are rarely linked when studying bloom development and persistence. P. bahamense is a toxic, bioluminescent dinoflagellate that previously bloomed in Florida with no known record of saxitoxin (STX) production. Over the past 20 years, STX was identified in P. bahamense populations. The goal of this study was to examine toxin dynamics and associated molecular mechanisms in spatially and temporally distinct P. bahamense populations from the Indian River Lagoon, FL. SxtA4 is a key gene required for toxin biosynthesis. SxtA4 genotype analysis was performed on individual cells from multiple sites. Cell abundance, toxin quota cell−1, and sxtA4 and RubisCo (rbcL) transcript abundance were also measured. There was a significant negative correlation between cell abundance and toxin quota cell−1. While the sxtA4+ genotype was dominant at all sites, its frequency varied, but it occurred at 90–100% in many samples. The underlying mechanism for toxin decrease with increased cell abundance remains unknown. However, a strong, statistically significant negative correlation was found between stxA4 transcripts and the sxtA4/rbcL ratio, suggesting cells make fewer sxtA4 transcripts as a bloom progresses. However, the influence of sxtA4− cells must also be considered. Future plans include bioluminescence measurements, normalized to a per cell basis, at sites when toxicity is measured along with concomitant quantification of sxtA4 gene and transcript copy numbers as a means to elucidate whether changes in bloom toxicity are driven more at the genetic (emergence of sxtA4− cells) or transcriptional (repression of sxtA4 in sxtA4+ cells) level. Based on the results of this study, a model is proposed that links the combined traits of toxicity and bioluminescence in P. bahamense bloom development. [ABSTRACT FROM AUTHOR]

Dinoflagellate species that form some of the most frequent toxic blooms are also bioluminescent, yet the two traits are rarely linked when studying bloom development and persistence. P. bahamense is a toxic, bioluminescent dinoflagellate that previously bloomed in Florida with no known record of saxitoxin (STX) production. Over the past 20 years, STX was identified in P. bahamense populations. The goal of this study was to examine toxin dynamics and associated molecular mechanisms in spatially and temporally distinct P. bahamense populations from the Indian River Lagoon, FL. SxtA4 is a key gene required for toxin biosynthesis. SxtA4 genotype analysis was performed on individual cells from multiple sites. Cell abundance, toxin quota cell−1, and sxtA4 and RubisCo (rbcL) transcript abundance were also measured. There was a significant negative correlation between cell abundance and toxin quota cell−1. While the sxtA4+ genotype was dominant at all sites, its frequency varied, but it occurred at 90–100% in many samples. The underlying mechanism for toxin decrease with increased cell abundance remains unknown. However, a strong, statistically significant negative correlation was found between stxA4 transcripts and the sxtA4/rbcL ratio, suggesting cells make fewer sxtA4 transcripts as a bloom progresses. However, the influence of sxtA4− cells must also be considered. Future plans include bioluminescence measurements, normalized to a per cell basis, at sites when toxicity is measured along with concomitant quantification of sxtA4 gene and transcript copy numbers as a means to elucidate whether changes in bloom toxicity are driven more at the genetic (emergence of sxtA4− cells) or transcriptional (repression of sxtA4 in sxtA4+ cells) level. Based on the results of this study, a model is proposed that links the combined traits of toxicity and bioluminescence in P. bahamense bloom development.

The saxitoxin-producing dinoflagellate, Pyrodinium bahamense, blooms most summers in Old Tampa Bay (OTB). It is a relatively slow growing alga yet forms high biomass blooms, suggesting contributions to biomass losses (e.g., grazing, transport) are low. Restoration of filterfeeding bivalves might mitigate bloom initiation, intensity, or duration if bivalves could effectively consume this alga. The effect of toxic Pyrodinium exposure on clearance rates of eastern oysters (Crassostrea virginica') was investigated in two laboratory trials: 1) oysters were exposed to toxic Pyrodinium for two hours at two ecologically relevant concentrations representing early to midbloom and peak bloom conditions and 2) oysters were fed for four days a diet of either pulsed exposure to Pyrodinium alone, Pyrodinium mixed with a nontoxic algal food source, or nontoxic algae alone. Oyster grazing on Pyrodinium was not significantly different when exposed to either low (~3 gg L-1 chlorophyll a) or high (~45 pg L-1 chlorophyll a) abundances of Pyrodinium. The oysters successfully consumed Pyrodinium after pulsed exposure for four days, with no difference in grazing over time. However, clearance rates were significantly lower in all treatments containing Pyrodinium (~500-1600 mL h-1 g-1) compared to the control treatment with only a nontoxic algal food source (--4400 mL IT1 g-1). Overall clearance rates of oysters after exposure to toxic Pyrodinium stayed high enough to suggest bivalve grazing could result in localized removal of Pyrodinium during blooms, but questions on potential effects of long-term exposure on grazing and health of oysters remain. [ABSTRACT FROM AUTHOR]

Pyrodinium bahamense blooms reaching and exceeding 105 cells L-1 occur nearly every summer in Tampa Bay, Florida, USA. These high biomass blooms can reduce light penetration, degrade water quality, and deplete dissolved oxygen. In addition, this alga produces potent neurotoxins (saxitoxins) that can accumulate in filter-feeding shellfish and cause paralytic shellfish poisoning in humans if contaminated shellfish are consumed. Variability in toxicity of two alternate life history stages (vegetative cells and resting cysts) of P. bahamense can have implications for resource management. Here we discuss the saxitoxin composition and concentration observed in vegetative cells and resting cysts of P. bahamense collected from Tampa Bay. Analysis of bloom samples and cysts collected from Tampa Bay confirmed the presence of three saxitoxin congeners: decarbamoylsaxitoxin (dcSTX), gonyautoxin 5 (GTX5), and saxitoxin (STX) and showed that in general, vegetative cells in this area may be more toxic than resting cysts. In samples collected on 10 days throughout a laboratory growth experiment on a single isolate, the average total cellular toxin was 0.2 ± 0.02 pmol cell-1. In contrast, the average total cellular toxin in vegetative cells from bloom samples collected from 9 locations during peak bloom was 0.02 ± 0.002 pmol cell-1 and the concentration in resting cyst from one sediment sample 0.003 pmol cyst-1. [ABSTRACT FROM AUTHOR]

The production of cysts by dinoflagellates can be part of the life cycle of some species, improving their survival under adverse environmental conditions; cyst germination may explain the recurrence of algal blooms in some cases. In order to evaluate the germination rates of Pyrodinium bahamense, its cysts were retrieved from surface sediments collected in San José Lagoon, SW Gulf of California, and germination assays were carried out through the cysts incubation under two contrasting light and nutrient concentration conditions. Also, to evaluate cysts viability, we isolated P. bahamense cysts and other dinoflagellate species from different depth layers of a 210Pb-dated sediment core (~100 years) to examine their germination for 20 days. Germination rates were higher under light (28–56%) than in darkness (23–34%); there were indications that the nutrient-enriched media was more effective in promoting germination than seawater. Furthermore, germination was observed in cysts isolated from all selected core depths, even those corresponding to ~100 years. These results demonstrate that cysts remain viable for long periods, and P. bahamense cysts germinate in any light and nutrient conditions. The results of this research provide relevant information to understand its physiology and complex population dynamics. This species should be closely monitored in the area in the context of climate change, as current natural conditions are likely to change. [ABSTRACT FROM AUTHOR]

Pyrodinium bahamense var compressum is a harmful dinoflagellate that produces saxitoxin, which causes paralytic shellfish poisoning (PSP) that is deadly to humans. A non-axenic culture of P. bahamense was established using f/2 media from samples collected from Sepanggar Bay, Kota Kinabalu, Sabah. Toxin analyses of cultures harvested on days 60, 120, 180, and 360 were performed using high-performance liquid chromatography with a fluorescence detector and compared with samples collected at the same location during the bloom in 2021. The highest cell toxin content was found in the bloom sample (86.2 fmole/ cell), and no toxin was detected in the culture 60 days old. In addition, cell toxin content for the P. bahamense culture was low (9.4-16.5 fmole/cell). Based on the toxin profile, P. bahamense comprises 84-98% of gonyautoxin 4. In summary, the current findings add to the existing knowledge of the toxin profiling of P. bahamense, a toxic, harmful algal bloom species, thus, leading to better toxin management. [ABSTRACT FROM AUTHOR]

In September and November 2016, eight marine sampling sites along the coast of the southeastern Gulf of Mexico were monitored for the presence of lipophilic and hydrophilic toxins. Water temperature, salinity, hydrogen potential, dissolved oxygen saturation, inorganic nutrients and phytoplankton abundance were also determined. Two samples filtered through glass fiber filters were used for the extraction and analysis of paralytic shellfish toxins (PSTs) by lateral flow immunochromatography (IFL), HPLC with post-column oxidation and fluorescent detection (FLD) and UHPLC coupled to tandem mass spectrometry (UHPLC-MS/MS). Elevated nutrient contents were associated with the sites of rainwater discharge or those near anthropogenic activities. A predominance of the dinoflagellate Pyrodinium bahamense was found with abundances of up to 104 cells L−1. Identification of the dinoflagellate was corroborated by light and scanning electron microscopy. Samples for toxins were positive by IFL, and the analogs NeoSTX and STX were identified and quantified by HPLC-FLD and UHPLC-MS/MS, with a total PST concentration of 6.5 pg cell−1. This study is the first report that confirms the presence of PSTs in P. bahamense in Mexican waters of the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Pelagic Sargassum beaching events are a global environmental issue that have caused increasing detrimental effects to coastal ecosystems since the 1970s. The 2015 pelagic Sargassum bloom in the Atlantic and the Caribbean caused significant impacts to coastal ecological communities in these areas. In enclosed systems, such as bays and lagoons, the Sargassum impacts could be particularly problematic due to the longer water residence times. An example of such an ecosystem is Laguna Grande bioluminescent lagoon, Puerto Rico. This lagoon slowly exchanges water with the ocean through a narrow channel (average about 5 m across), which results in the accumulation of the bioluminescent dinoflagellate Pyrodinium bahamense and other planktonic organisms. In this study we describe the 2015 pelagic Sargassum accumulation event in Laguna Grande, and report associated changes in the phytoplanktonic composition. Before this event, other studies conducted between 2003 and 2013 reported mean densities of P. bahamense ranging from 14,492 to 28,202 cells/L. However, the P. bahamense population was absent from the lagoon during the 2015 Sargassum influx. After the entrance of large quantities of pelagic Sargassum into the lagoon, accompanied with other marine algae and sea grasses, the macrophytes remained inside and began to decompose. Thirteen phytoplankton taxa not previously observed inside the lagoon were detected after the entrance of the macrophytes. We hypothesize that the changes in the phytoplanktonic composition in the lagoon were caused by altered water quality conditions following the entrance of the pelagic Sargassum and other macrophytes. [ABSTRACT FROM AUTHOR]

In September and November 2016, eight marine sampling sites along the coast of the southeastern Gulf of Mexico were monitored for the presence of lipophilic and hydrophilic toxins. Water temperature, salinity, hydrogen potential, dissolved oxygen saturation, inorganic nutrients and phytoplankton abundance were also determined. Two samples filtered through glass fiber filters were used for the extraction and analysis of paralytic shellfish toxins (PSTs) by lateral flow immunochromatography (IFL), HPLC with post-column oxidation and fluorescent detection (FLD) and UHPLC coupled to tandem mass spectrometry (UHPLC-MS/MS). Elevated nutrient contents were associated with the sites of rainwater discharge or those near anthropogenic activities. A predominance of the dinoflagellate Pyrodinium bahamense was found with abundances of up to 104 cells L−1. Identification of the dinoflagellate was corroborated by light and scanning electron microscopy. Samples for toxins were positive by IFL, and the analogs NeoSTX and STX were identified and quantified by HPLC-FLD and UHPLC-MS/MS, with a total PST concentration of 6.5 pg cell−1. This study is the first report that confirms the presence of PSTs in P. bahamense in Mexican waters of the Gulf of Mexico.

This paper examines the character of phytoplankton blooms in a restricted sub-tropical lagoon along the Atlantic coast of central Florida. The results of the 23-year study (1997–2020) provide evidence for multiple types of variability in bloom activity, including cyclical patterns, stochastic events, and most prominently a regime shift in composition and intensity. Cyclical patterns (e.g., El Niño/La Niña periods) and stochastic events (e.g., tropical storms) influenced rainfall levels, which in turn impacted nutrient concentrations in the water column and the timing and intensity of blooms. In 2011, a major change occurred in the character of blooms, with a dramatic increase in peak biomass levels of blooms and the appearance of new dominant taxa, including the brown tide species Aureoumbra lagunensis and other nanoplanktonic species. Results of quantitative analyses reveal system behavior indicative of a regime shift. The shift coincided with widespread losses of seagrass community and reduced drift algae biomass. A combination of exceptionally low water temperatures in the winters of 2009/2010 and 2010/2011, hypersaline conditions associated with drought conditions, and high light attenuation caused by blooms appear to have contributed to the widespread and protracted decline in seagrass and drift macroalgal communities in the lagoon, leading to shifts in distribution of internal and external nutrient sources toward phytoplankton.

Proteins, lipids, and carbohydrates from the harmful algal bloom (HAB)-causing organism Pyrodinium bahamense were characterized to obtain insights into the biochemical processes in this environmentally relevant dinoflagellate. Shotgun proteomics using label-free quantitation followed by proteome mapping using the P. bahamense transcriptome and translated protein databases of Marinovum algicola, Alexandrium sp., Cylindrospermopsis raciborskii, and Symbiodinium kawagutii for annotation enabled the characterization of the proteins in P. bahamense. The highest number of annotated hits were obtained from M. algicola and highlighted the contribution of microorganisms associated with P. bahamense. Proteins involved in dimethylsulfoniopropionate (DMSP) degradation such as propionyl CoA synthethase and acryloyl-CoA reductase were identified, suggesting the DMSP cleavage pathway as the preferred route in this dinoflagellate. Most of the annotated proteins were involved in amino acid biosynthesis and carbohydrate degradation and metabolism, indicating the active roles of these molecules in the vegetative stage of P. bahamense. This characterization provides baseline information on the cellular machinery and the molecular basis of the ecophysiology of P. bahamense.

Aim: A number of reports have implicated the role of the symbiotic bacterial communities associated with toxic dinoflagellates in the biosynthesis of saxitoxin during harmful algal blooms (HABs). However, the exact mechanisms by which the bacteria facilitate toxin production remain inconclusive. The toxic dinoflagellate, Pyrodinium bahamense var. compressum, is the causative organism responsible for paralytic shellfish poisoning in the coastal waters of Sabah, and it is caused by the consumption of filter-feeding shellfish contaminated with the neurotoxin, saxitoxin. The present study aimed at characterizing the species diversity of symbiotic bacteria occurring within a monoalgal culture of P. bahamense var. compressum. Methodology and results: The total bacterial DNA was amplified using paired-end 16S community sequencing on the Illumina platform, targeting the V3-V4 region of the 16S ribosomal RNA gene. Bacteria were classified into 20 classes, 43 orders, 60 families, and 105 genera. A total of 10 phyla were present, where the major phylum was Proteobacteria (69.5%). The major genera were Pseudoruegeria (32%), Roseibium (16%), Hyphomonas (16%), Phaeobacter (7%), Lutimaribacter (5%) and Methylophaga (5%). This study showed that the previous method of assessing microbial diversity occurring in P. bahamense var. compressum has underestimated the actual species diversity. Conclusion, significance and impact of study: The high-throughput sequencing of the 16S metagenomes revealed hitherto unreported bacterial taxa associated with P. bahamense var. compressum. The findings of the present work will pave the way for further studies aimed at isolating and characterizing symbiotic bacteria that are likely to be associated with the biosynthesis of toxins. [ABSTRACT FROM AUTHOR]

Associated and algicidal bacteria play roles in the succession and decline of phytoplankton blooms, including those of harmful algal bloom (HAB)-forming species. Limited studies on HAB-associated bacterial ecology have resulted in our incomplete understanding of HABs dynamics. Diverse phytoplankton-bacterial interactions have also led to studies on their potential as biocontrol tools for HABs mitigation. Here, we tested 48 cultivable pelagic bacteria from three HAB-affected areas in the Philippines (Bolinao, Sorsogon, and Matarinao) against non-axenic cultures of the toxic, thecate dinoflagellate Pyrodinium bahamense. Co-incubation with live cultures of these isolates exhibited varying levels of algicidal activities suggesting that it may not be a phylogenetically conserved property. Furthermore, majority of the isolates elicited activity against the thecate test species P. bahamense, which was not present in the area where the bacteria were isolated, implying non-specificity of action. Exposure to bacterial cells resulted in Pyrodinium pellicle cyst formation. Despite this, however, cell lysis and decline in total cell abundance were still observed, indicating strong algicidal potency of the isolates. In depth understanding of the interplay between environmental factors and algicidal bacteria-microalgal interactions may provide significant insights on the management of HABs. [ABSTRACT FROM AUTHOR]

Saxitoxin (STX) is a secondary metabolite and potent neurotoxin produced by several genera of harmful algal bloom (HAB) marine dinoflagellates. The basis for variability in STX production within natural bloom populations is undefined as both toxic and non-toxic strains (of the same species) have been isolated from the same geographic locations. Pyrodinium bahamense is a STX-producing bioluminescent dinoflagellate that blooms along the east coast of Florida as well as the bioluminescent bays in Puerto Rico (PR), though no toxicity reports exist for PR populations. The core genes in the dinoflagellate STX biosynthetic pathway have been identified, and the sxtA4 gene is essential for toxin production. Using sxtA4 as a molecular proxy for the genetic capacity of STX production, we examined sxtA4+ and sxtA4- genotype frequency at the single cell level in P. bahamense populations from different locations in the Indian River Lagoon (IRL), FL, and Mosquito Bay (MB), a bioluminescent bay in PR. Multiplex PCR was performed on individual cells with Pyrodinium-specific primers targeting the 18S rRNA gene and sxtA4. The results reveal that within discrete natural populations of P. bahamense, both sxtA4+ and sxtA4- genotypes occur, and the sxtA4+ genotype dominates. In the IRL, the frequency of the sxtA4+ genotype ranged from ca. 80–100%. In MB, sxtA4+ genotype frequency ranged from ca 40–66%. To assess the extent of sxtA4 variation within individual cells, sxtA4 amplicons from single cells representative of the different sampling sites were cloned and sequenced. Overall, two variants were consistently obtained, one of which is likely a pseudogene based on alignment with cDNA sequences. These are the first data demonstrating the existence of both genotypes in natural P. bahamense sub-populations, as well as sxtA4 presence in P. bahamense from PR. These results provide insights on underlying genetic factors influencing the potential for toxin variability among natural sub-populations of HAB species and highlight the need to study the genetic diversity within HAB sub-populations at a fine level in order to identify the molecular mechanisms driving HAB evolution.

In this review we summarize the current state of knowledge regarding taxonomy, bloom dynamics, toxicity, autoecology, and trophic interactions, of saxitoxin producing dinoflagellates in this region. The dinoflagellates Gymnodinium catenatum, Pyrodinium bahamense and several species of Alexandrium are saxitoxin producers, and have been responsible of paralytic shellfish poisoning in different regions of Latin America, causing intoxications and important fisheries losses. The species distribution differ; most harmful algal blooms of G. catenatum are from the northern region, however this species has also been reported in central and southern regions. Blooms of P. bahamense are mostly reported in North and Central America, while blooms of Alexandrium species are more common in South America, however this genus is widely spread in Latin America. Species and regional differences are contrasted, with the aim to contribute to future guidelines for an international scientific approach for research and monitoring activities that are needed to increase our understanding of paralytic toxin producing dinoflagellates in this region.

Pyrodinium bahamense produces saxitoxins and can cause paralytic shellfish poisoning (PSP). This species has caused more human illnesses and fatalities than any other toxic dinoflagellate in Mexico. The distribution of dinoflagellate cysts with their vegetative stage is broad, mainly along Mexican Pacific coasts from the central Gulf of California to Chiapas, as well as in the southern Gulf of Mexico and the Mexican Caribbean Sea on the Atlantic coast. In vitro germination of living cysts from the southern Gulf of California occurs under thermophilic (20–35°C) and euryhaline (20–35 ups) conditions. Blooms occurred typically during summer rainy season (June through September), inside of restricted shallow lagoons surrounded by mangrove forests. The data obtained so far on P. bahamense spatial and population variability in Mexican Pacific and the Gulf of Mexico, suggest a seasonal and latitudinal pattern. Also, in these regions, the abundance, seasonality, and species distribution tend to decrease from tropical to subtropical areas. The local strain toxicity has only been corroborated in one isolate from the southern Gulf of California, which exhibited a high saxitoxin concentration of 95 pg STX eq cell-1. PSP outbreaks linked with P. bahamense in the Gulf of Tehuantepec from 1989 to 2007, caused at least ∼200 human cases, with 15 fatalities. This mini-review ends with a viewpoint of management and research strategies to better understand the factors that play essential roles in the bloom dynamics and toxicity of this species.

Pyrodinium bahamense is a dinoflagellate of concern in subtropical and tropical coastal environments. To date, there is only a single published study on its fatty acids, but no published data on its sterol composition. Sterols, which are membrane‐reinforcing lipids in eukaryotes, display a great diversity of structures in dinoflagellates, with some serving as chemotaxonomic markers. We have examined the sterol compositions of two isolates of P. bahamense from Indian River Lagoon and Tampa Bay, Florida, and have found both to produce three sterols: cholesterol, dinosterol, and 4α‐methylgorgostanol. All three sterols are found in closely related, armored taxa. [ABSTRACT FROM AUTHOR]

Highlights • Developed a novel model integrating Pyrodinium , physical, and shellfish dynamics. • Model captured temporal variabilities of Pyrodinium cells and shellfish toxicities. • Even when cysts could excyst, Pyrodinium increased only when rainfall increased. • Pyrodinium decline was affected by shellfish grazing and cell mortality. • Role of cysts in shellfish toxicity could be important and needs to be examined. Abstract In contrast to temperate Harmful Algal Blooms (HABs), knowledge on the mechanisms driving tropical HABs are less well studied. The interaction of a seasonal temperature window, cysts (for certain species) and large-scale transport are some of the key processes in temperate HABs. In the Philippines, HABs occur not along long open coastlines, but in embayments that are highly influenced by run-off and stratification. These embayments are typically also the sites of cultured or wild harvest shellfish and other aquaculture activities. Sorsogon Bay in the northeastern Philippines has experienced prolonged shellfish-harvesting bans due to blooms by Pyrodinium bahamense var. compressum severely affecting the fisheries industry in this area, as well as leading to Paralytic Shellfish Poisoning illnesses and fatalities. A novel integrated model was developed that mechanistically captures the interactions between hydrodynamic conditions, nutrients, the life history (cells and cysts) of Pyrodinium , as well as the cultured shellfish within the bay and their ensuing toxicities due to ingestion of toxic Pyrodinium cells and cysts. This is the second model developed for HABs in the Philippines, and the first to integrate different components of Pyrodinium bloom dynamics. The model is modularly composed of a watershed nutrient and diffusion model, a 3D hydrodynamic model, a Pyrodinium population model and a shellfish toxin model. It was able to capture the observed temporal variations of Pyrodinium and shellfish toxicity. It was also able to represent some aspects of the spatial distribution in Sorsogon Bay though there were discrepancies. To explore the dynamics of blooms, the linkages between the bloom and decline of the Pyrodinium population with shellfish toxicity as affected by temperature, salinity and nutrients were investigated. Comparisons with field results showed the seasonality of blooms in Sorsogon Bay is driven by increased rainfall. The timing of these conditions is important in facilitating Pyrodinium excystment and reproduction. Model results showed as well the potential significance of shellfish grazing and dinoflagellate cell mortality in influencing the decline of the bloom, and toxicity levels. This approach is promising in helping to understand mechanisms for HABs more holistically, and the model can be further improved to provide more precise quantitative information. [ABSTRACT FROM AUTHOR]

Objetivo. Monitorear el dinoflagelado Pyrodinium bahamense y sus toxinas en ostión de roca Striostrea prismatica en Santiago Astata y en Puerto Escondido, Oaxaca, de septiembre de 2009 a junio de 2010. Material y métodos. Se analizó mensualmente la abundancia de Pyrodinium bahamense mediante el método de Sedgewick-Rafter y la concentración de toxinas paralizantes y perfil tóxico en tejido blando del molusco en muestras compuestas de cada zona por el método de cromatografía líquida de alta resolución. Resultados. Se encontró alta abundancia de Pyrodinium bahamense en Santiago Astata en diciembre, febrero, abril y junio, y en Puerto Escondido en abril y junio. Los niveles de toxinas paralizantes fueron superiores al límite permisible para consumo humano en Santiago Astata en noviembre, diciembre, enero, febrero y junio; en la zona de Puerto Escondido, en diciembre y junio. Conclusiones. Estos niveles de toxinas representaron riesgo para la salud pública en la zona de estudio.

We examined organic-walled dinoflagellate cysts from one 210Pb-dated sediment core and 39 surface sediment samples from the northern Gulf of Mexico to determine the relationship between nutrient enrichment and cyst assemblages in this region characterized by oxygen deficiency. The core spans from 1962 to 1997 and its sampling location is directly influenced by the Mississippi River plume. Surface sediments were collected in 2006, 2007, 2008, and 2014 and represent approximately 1 to 4 years of accumulation. A total of 57 cyst taxa were recorded, and four heterotrophic taxa in particular were found to increase in the top section (1986-1997) of the core—Brigantedinium spp., cysts of Archaeperidinium minutum, cysts of Polykrikos kofoidii, and Quinquecuspis concreta. These taxa show a similar increasing trend with variations in US fertilizer consumption and Mississippi River nitrate concentrations, both of which increased substantially in the 1970s and 1980s. The same four heterotrophic taxa dominated dinoflagellate cyst assemblages collected near the Mississippi River Bird’s Foot Delta where nutrient concentrations were higher, especially in 2014. We propose that these cyst taxa can be used as indicators of eutrophication in the Gulf of Mexico. A canonical correspondence analysis (CCA) supports this proposition. The CCA identified sea-surface nutrient concentrations, sea-surface temperature, and sea-surface salinity as the most important factors influencing the cyst assemblages. In addition, cysts produced by the potentially toxic dinoflagellates Pyrodinium bahamense and Lingulodinium polyedrum were documented, but did not appear to have increased over the past 50 years. [ABSTRACT FROM AUTHOR]

Cysts withstand hostile environmental conditions and are source of inoculum for recurrent blooms. In the Philippines, the first recorded bloom of the phytoplankton Pyrodinium bahamense was observed in Samar-Leyte areas, including Cancabato Bay in 1983. Since then, shellfish bans in these areas have been imposed periodically. Until the present however, there is no thorough cyst study done in this bay. This study has assessed the abundance and distribution of dinoflagellate cysts in the bay. Surface sediment samples collected and processed by palynological technique have revealed a total of 21 species of dinoflagellate cysts belonging to five groups: Gonyaulacoid, Protoperidinioid, Gymnodinioid, Calciodinellid, and Diplopsalid. Cysts have been detected in all stations, with cyst densities ranging from 1-80 cysts g-1 DW; and Operculodinium centrocarpum (Protoceratium reticulatum) dominated in four stations. Low levels of P. bahamense cysts, Polysphaeridium zoharyi, have been detected in 13 stations, the densest at 16 cysts g-1 DW. Concentrations of cysts that have been highest in the inner part of the bay could have been affected by several factors, including substrate type, bulk dry weight, and nitrogen content. This important stage of the lifecycle of dinoflagellates should be factored in future models to predict P. bahamense blooms in the bay. [ABSTRACT FROM AUTHOR]

Bioluminescent bays and lagoons are unique natural environments and popular tourist attractions. However, the bioluminescence in many of these water bodies has declined, principally due to anthropogenic activities. In the Caribbean, the bioluminescence in these bays and lagoons is mostly produced by the dinoflagellate Pyrodinium bahamense var. bahamense. Laguna Grande is one of the three year-round bioluminescent water bodies in Puerto Rico that are known to remain but P. bahamense var. bahamense density fluctuations have not been studied. In this study we describe water quality parameters and density fluctuations of the most common dinoflagellates in Laguna Grande, P. bahamense var. bahamense and Ceratium furca, over a three-year period. For this, three sampling stations were established in Laguna Grande from which water samples were collected in triplicate and analyzed for temperature, phosphates, nitrates, salinity, water transparency, fluorescence, and dinoflagellate densities, at the water surface and at 2m depth, from May 2003 to May 2006. The results showed a density fluctuation pattern for P. bahamense var. bahamense, where higher densities were observed mainly from April to September, and lower densities from October to February. Density fluctuations of C. furca were more erratic and a repetitive pattern was not observed. Densities of P. bahamense var. bahamense ranged from 0.48 to 90 978 cells/L and densities of C. furca ranged from 0 to 11 200 cells/L. The mean population density throughout the sampling period was significantly higher in P. bahamense var. bahamense (mean=18 958.5 cells/L) than in C. furca (mean=2 601.9 cells/L). Population densities of P. bahamense var. bahamense were negatively correlated with C. furca densities during the first year of sampling; however, they were positively correlated during the third year. Non-significant differences between surface and 2m depth samples were observed for temperature, phosphates, nitrates, salinity, fluorescence, and densities of P. bahamense var. bahamense and C. furca, suggesting a vertically mixed water column. Water transparency was positively correlated with salinity and negatively correlated with fluorescence. Fluorescence was negatively correlated with salinity. The mean population densities of P. bahamense var. bahamense and C. furca observed in this study were within the range of previous reports in other bioluminescent water bodies in Puerto Rico and Florida, USA. In order to conserve the continuous P. bahamense var. bahamense populations in Laguna Grande, as well as its bioluminescence, it is recommended to maintain the existing water flow levels in the 1.5km long inlet/outlet channel; to maintain unpolluted water quality parameters within the bay, the hydrographical basin and adjacent waters, and to preserve mangrove communities within the basin and adjacent areas. Results of this study may help to develop management plans aiming to conserve P. bahamense, its bioluminescence and the lagoon attraction.

In the past four decades, consistent and coordinated management actions led to the recovery of Tampa Bay, FL (USA) – an estuary that was declared dead in the 1970s. An exception to this success story is Old Tampa Bay, the northernmost subestuary of the system. Compared to the other bay segments, Old Tampa Bay is characterized by poorer water quality and spring and summer blooms of cyanobacteria, picoplankton, diatoms, and the saxitoxin-producing dinoflagellate Pyrodinium bahamense . Together, these blooms contribute to light attenuation and lagging recovery of seagrass beds. Yet, studies of phytoplankton dynamics within Old Tampa Bay have been limited – both in number and in their spatiotemporal resolution. In this study, we used field sampling and continuous monitoring to (1) characterize temporal and spatial variability in phytoplankton biomass and community composition and (2) identify key drivers of the different phytoplankton blooms in Old Tampa Bay. Overall, temporal variability in phytoplankton biomass (using chlorophyll a as a proxy) and community composition surpassed spatial variability of these parameters. We found a base community of small diatoms and flagellates, as well as certain dinoflagellates, that persisted year round in the system. Seasonally, freshwater runoff stimulated phytoplankton growth, specifically that of chlorophytes, cyanobacteria and other dinoflagellates -- consistent with predictions based on ecological theory. On shorter time scales, salinity, visibility, and freshwater inflows were important predictors of phytoplankton biomass. With respect to P. bahamense , environmental drivers including salinity, temperature and dissolved nutrient concentrations explained ∼24% of the variability in cell abundance, indicating missing explanatory parameters in our study for this taxon, such as cyst density and location of cyst beds. Spatially, we found differences in community trajectories across north–south and west–east gradients, with the northernmost sampling station being the most unique in the region. This work contributes to the knowledge of phytoplankton biomass and community composition in Tampa Bay by generating spatially and temporally rich phytoplankton community and environmental data for the Old Tampa Bay subestuary. Moreover, it enhances our understanding of bloom drivers and provides recommendations for ecosystem management. Specifically, our findings support continued nutrient reduction measures as a way to mitigate seasonal blooms of diatoms, cyanobacteria and chlorophytes, but not necessarily blooms of P. bahamense . Prediction and mitigation of P. bahamnese blooms should incorporate first order drivers such as cyst location and abundance. [ABSTRACT FROM AUTHOR]

Decreases in bioluminescence in Bahía Fosforescente have been associated with alternations between bioluminescent ( Pyrodinium bahamense ) and non-bioluminescent ( Ceratium furca) dinoflagellates, two potentially harmful algal bloom species (HABs). Until now, these changes in bioluminescence have never been quantified, and their relationship with seasonality remains unclear. This study quantified the bioluminescence potential (BP) in the bay with a high spatiotemporal resolution to evaluate the status of this phenomenon and to determine the link between seasonality on the BP and dinoflagellate composition. Biweekly measurements, from August 2012 to July 2013, were conducted at six stations with an Underwater Bioluminescent Assessment Tool. The highest BP were observed during the wet season and were correlated (Spearman rank correlation: r = 0.89, n = 64, p < 0.001) with high cell densities of P. bahamense . Ceratium furca cell densities surpassed those of P. bahamense during the dry season, with concomitant reductions in the BP. The presence of other potentially bioluminescent dinoflagellates, such as Protoperidinium spp . , during the latter season, with abundances higher than those of P. bahamense , suggests their contribution to the BP. It is suggested that environmental changes exerted by different meteorological conditions cause variations in the BP by modulating the dinoflagellate composition. Overall, a higher BP were observed in the northern area of the bay, suggesting that wind-driven currents promoted the accumulation of organisms in this region. This study underscores how weather, changes in the abundance of these two potentially HAB species, and the BP at Bahía Fosforescente are critically linked. [ABSTRACT FROM AUTHOR]

Harmful algal blooms of the dinoflagellate Pyrodinium bahamense have caused human and economic losses in the last decades. This study, for the first time, documents a bloom of P. bahamense in the Red Sea. The alga was recurrently present in a semi-enclosed lagoon throughout nearly 2 years of observations. The highest cell densities (10 4 –10 5 cells L −1 ) were recorded from September to beginning of December at temperatures and salinities of ∼26–32 °C and ∼41, respectively. The peak of the bloom was recorded mid-November, before a sharp decrease in cell numbers at the end of December. Minimum concentrations in summer were at ∼10 3 cells L −1 . A saxitoxin ELISA immunoassay of cultures and water samples confirmed the toxicity of the strain found in the Red Sea. Moreover, a gene expression analysis of the saxitoxin gene domain SxtA4 showed that transcript production peaked at the culmination of the bloom, suggesting a relation between transcript production, sudden cells increment-decline, and environmental factors. [ABSTRACT FROM AUTHOR]

Mangrove Lagoon, located on the island of St. Croix, US Virgin Islands (USVI), is one of few actively bioluminescent lagoons in a location experiencing significant anthropogenic impacts. The bioluminescence is due to an abundance of the dinoflagellate Pyrodinium bahamense in the water column. We recovered surface sediments and sediment cores from Mangrove Lagoon to analyze the spatial distribution and temporal variability of P. bahamense cysts in this system. Surface sediment P. bahamense cyst concentrations ranged from 0 to 466 cysts g dry sediment, with higher abundances associated with elevated surface water nutrient concentrations and a mixed terrestrial-marine organic matter source regime. In combination with available bioassay data, we hypothesize that phytoplankton utilize nutrients rapidly and subsequent decay of organic matter makes nutrients available for dinoflagellates at the sediment-water interface in the eastern and northern quadrants of the lagoon. However, the nutrients are rapidly exhausted during counterclockwise lagoon circulation resulting in the decline of primary productivity and dinoflagellate abundance in the western quadrants. Downcore profiles suggest that P. bahamense blooms have been occurring for decades, declining in recent years. No cysts were present in sediments predating dredging activities of the 1960s that created Mangrove Lagoon. Recent reductions in cyst abundance may be the result of limited primary productivity caused by restricted water exchange with Salt River Bay due to shallowing of a sill at the mouth of the lagoon. This research highlights the need for more comprehensive geochemical and fossil analyses to better understand long-term ecological variability and inform conservation efforts of these unique habitats. [ABSTRACT FROM AUTHOR]

Many aspects of the biology and ecology of the toxic dinoflagellate Pyrodinium bahamense var. compressum are still poorly understood. In this brief note, we present identification of its associated intracellular bacteria or endosymbionts via PCR cloning and 16s rRNA gene sequencing and their localization by confocal microscopy, a first for Pyrodinium. The most frequently observed species in the endosymbiotic microflora were from Roseobacter clade (Alphaproteobacteria, 68 %) and Gilvibacter sediminis (Flavobacteriaceae, 20 %). Roseobacter lineage, the most abundant taxa in this study, is known to be involved in dimethylsulfoniopropionate metabolism which is highly produced in dinoflagellates-a possible strong factor shaping the structure of the associated bacterial community. [ABSTRACT FROM AUTHOR]

Objective. Pyrodinium bahamense monitoring in water and their toxins in rock oyster Striostrea prismatica in Santiago Astata and Puerto Escondido Oaxaca was performed from September 2009 to July 2010. Materials and methods. Pyrodinium bahamense abundance in water, and concentration and toxic profile of paralytic shellfish toxins were analyzed monthly in soft tissue of mollusk in composite samples in high performance liquid chromatography. Results. High abundance of Pyrodinium bahamense was found in Santiago Astata on December, February, April and June; and in Puerto Escondido on April and June. The concentrations of the paralyzing toxin that exceeded the regulatory limit for human consumption of mollusks (800 µg STX eq. kg-1) were presented in Santiago Astata on November, December, January, February and June; and in Puerto Escondido on December and June. Conclusions. For several months there was risk to public health due to the presence of paralytic shellfish toxins above the regulatory limit in oysters from the study area. [ABSTRACT FROM AUTHOR]

Background: During an October 2005 algal bloom (i.e., a rapid increase or accumulation in the population of algae) off the coast of Nicaragua, 45 people developed symptoms of paralytic shellfish poisoning (PSP) and one person died. PSP in humans is caused by ingestion of saxitoxin, which is a neurotoxin often associated with shellfish contaminated by algal blooms. To explore the relationship between the algal bloom and human illnesses, we performed a case-control study of residents living in a coastal island. We administered a standardized clinical questionnaire, sampled locally harvested seafood and algae, and obtained urine samples for saxitoxin testing from symptomatic and asymptomatic persons. PSP case-patients were defined as island residents who developed at least one neurological symptom during the November 4-16 intoxication period. Seafood and algal samples were analyzed for saxitoxins using the receptor-binding assay and high-performance liquid chromatography. Two urine samples were analyzed for saxitoxins using a newly developed immunoassay. Findings: Three shellfish and two algal samples tested positive for saxitoxins. Ten (9%) of 107 participants developed neurological symptoms during the specified time period and five required hospitalization. While 6 (67%) of 9 possible case-patients and 21 (21%) of 98 controls had eaten fish (p=0.008), all case-patients and 17 (17%) of controls had eaten clams (P<0.0001). The saxitoxin concentration in the urine of a hospitalized case-patient was 21 ng saxitoxin/g creatinine compared to 0.16 ng saxitoxin/g creatinine in the single control patient's urine. Conclusions: These findings suggest that a bloom of saxitoxin-producing algae resulted in saxitoxin accumulation in local clams and was responsible for the PSP intoxication. [ABSTRACT FROM AUTHOR]

Pyrodinium bahamense (bioluminescent) and Ceratium furca (non-bioluminescent), two potentially harmful algal bloom species (HABs), are the most abundant dinoflagellates in the tropical bioluminescent bay Bahía Fosforescente. Reductions in bioluminescence have been attributed to fluctuations in their abundances. It is unclear how short-term changes in the environment influence these fluctuations and how seasonality regulates their presence and abundance. Thus, temperature, salinity, nutrient concentrations, rainfall, wind velocity and direction, and counts of both dinoflagellates were examined at six stations, during five consecutive days, and during two climate extremes (i.e., the wet and dry seasons). During the wet season, P. bahamense abundances surpassed those of C. furca, reaching bloom conditions. Positive correlations were found between P. bahamense abundance, temperature, and salinity. The higher phosphates and nitrites + nitrates concentrations (PO, 0.09-1.92 μmol L; N + N, 0.34-7.67 μmol L) recorded during this season and their negative correlations with P. bahamense cell densities suggest efficient nutrient uptake and indicate that watershed-derived nutrients were important for the formation of blooms. C. furca cell densities were higher during the dry season, when nutrient concentrations were low (PO, 0.17-0.5 μmol L; N + N, 0.2-1.23 μmol L). Physiological characteristics and adaptive strategies of C. furca, such as mixotrophy, osmotrophy, and luxury consumption, may explain the higher abundances of this species under low-nutrient conditions. The spatial distribution of both organisms was similar during both seasons with higher cell densities in the east/southeast regions of the bay. This study provides new insights on the ecology of Bahía Fosforescente that are important for its management and broadens the knowledge on the factors that regulate the presence and abundance of two potentially HABs species. [ABSTRACT FROM AUTHOR]

Pyrodinium bahamense var. compressum has been the primary organism responsible for the toxic red tide episodes which have been recurring in Manila Bay, Philippines since 1988. The life history of the species has been elucidated through encystment-excystment studies in vitro, from which its obligatory dormancy has been demonstrated. Cyst-mapping studies have shown that this life stage of the organism occurs relatively higher in the Bataan and Cavite areas where the greater number of red tide occurrences have also been reported. A cyst-based model has been developed as an initial step in understanding the role of physical processes in the development, occurrence/recurrence, and ultimately, advancement of Pyrodinium red tides in Manila Bay.To help mitigate or prevent the negative impacts of toxic red tides, particularly in Manila Bay, regular closure of shellfish harvest in areas affected by Pyrodinium bloom should be considered, based on long term monitoring and research data sets.

Pyrodinium bahamense is a meroplanktonic dinoflagellate that produces paralytic shellfish toxins that cause human poisoning along tropical and subtropical coasts. Cyst morphology, germination characteristics, and toxicity were investigated using samples from Isla San José in the Gulf of California. Morphology was observed through light and scanning electron microscopy. Germination was tested at different temperature (15°C-35°C) and salinity (15-35) conditions in different culture media (natural seawater, GSe, and f/2). To elucidate toxicity of vegetative cells grown from cyst germination, nine strains were subject to toxin analyses through fluorescence high-performance liquid chromatography. Morphological features and size of cysts generally agree with previous descriptions, particularly morphotypes found in the subtropical North Atlantic, where P. bahamense var. bahamense occurs. Cysts exhibit thermophilic and euryhaline characteristics. Highest germination occurred from 20°C to 35°C with the peak between 25°C and 30°C. Excystment occurred at salinities from 20 to 35. Germination occurred in the three culture media, but was highest in the optimal temperature range in the culture medium that included terrestrial soil extract and selenium. Only one strain exhibited toxicity with high saxitoxin concentration (95 pg STX eq cell-1). [ABSTRACT FROM AUTHOR]

Pellicle or temporary cysts ofPyrodinium bahamensevar.compressum(Böhm) Steidinger, Tester & F.J.R. Taylor and their role in bloom dynamics have not yet been adequately characterized and understood. We investigated the role of temperature- and nutrient-mediated stress as factors that could induce pellicle formation in batch cultures. Cellular features and their implications for temporary cyst viability were examined using confocal laser scanning microscopy (CLSM). Our data suggest that temperature change is one of the key factors influencing pellicle formation, preserving viability at low temperature (i.e. 13°C). Hypnocysts (resting cysts) were not observed. During pellicle formation, motile cells generally undergo ecdysis, extrusion of cytoplasmic materials and bacteria, compaction of the nucleus and non-motility. The outermost covering of the temporary cysts shows red autofluorescence and it contains lower concentrations of chlorophyll (chl)aand no detectable chlc.The nuclear region is surrounded by transitional red bodies and other unidentified cellular structures. Temporary cysts can immediately revert back to the motile state upon exposure to optimum conditions. This is accompanied by the expansion of the nuclear region, regeneration of the chloroplasts and enlargement of the cell. Developmental changes during reversal of temporary cysts to motile forms were also observed to cause breaks in the cell covering that could serve as sites for bacterial entry. Though observedin vitro, such behaviour may also be occurring in nature especially as a response to drastic short-lived environmental changes. This is the first detailed report on the characteristics of temporary cysts ofP. bahamensevar. compressum. [ABSTRACT FROM AUTHOR]

Bioluminescent bays and lagoons are unique natural environments and popular tourist attractions. However, the bioluminescence in many of these water bodies has declined, principally due to anthropogenic activities. In the Caribbean, the bioluminescence in these bays and lagoons is mostly produced by the dinoflagellate Pyrodinium bahamense var. bahamense. Laguna Grande is one of the three year-round bioluminescent water bodies in Puerto Rico that are known to remain but P. bahamense var. bahamense density fluctuations have not been studied. In this study we describe water quality parameters and density fluctuations of the most common dinoflagellates in Laguna Grande, P. bahamense var. bahamense and Ceratium furca, over a three-year period. For this, three sampling stations were established in Laguna Grande from which water samples were collected in triplicate and analyzed for temperature, phosphates, nitrates, salinity, water transparency, fluorescence, and dinoflagellate densities, at the water surface and at 2m depth, from May 2003 to May 2006. The results showed a density fluctuation pattern for P. bahamense var. bahamense, where higher densities were observed mainly from April to September, and lower densities from October to February. Density fluctuations of C. furca were more erratic and a repetitive pattern was not observed. Densities of P. bahamense var. bahamense ranged from 0.48 to 90 978 cells/L and densities of C. furca ranged from 0 to 11 200 cells/L. The mean population density throughout the sampling period was significantly higher in P. bahamense var. bahamense (mean=18 958.5 cells/L) than in C. furca (mean=2 601.9 cells/L). Population densities of P. bahamense var. bahamense were negatively correlated with C. furca densities during the first year of sampling; however, they were positively correlated during the third year. Non-significant differences between surface and 2m depth samples were observed for temperature, phosphates, nitrates, salinity, fluorescence, and densities of P. bahamense var. bahamense and C. furca, suggesting a vertically mixed water column. Water transparency was positively correlated with salinity and negatively correlated with fluorescence. Fluorescence was negatively correlated with salinity. The mean population densities of P. bahamense var. bahamense and C. furca observed in this study were within the range of previous reports in other bioluminescent water bodies in Puerto Rico and Florida, USA. In order to conserve the continuous P. bahamense var. bahamense populations in Laguna Grande, as well as its bioluminescence, it is recommended to maintain the existing water flow levels in the 1.5km long inlet/outlet channel; to maintain unpolluted water quality parameters within the bay, the hydrographical basin and adjacent waters, and to preserve mangrove communities within the basin and adjacent areas. Results of this study may help to develop management plans aiming to conserve P. bahamense, its bioluminescence and the lagoon attraction. [ABSTRACT FROM AUTHOR]

Blooms of the toxic alga, Pyrodinium bahamense var. compressum (Böhm), have become a problem in Malaysia over the past three decades. The alga is a causative agent of paralytic shellfish poisoning, a potentially fatal neurological disorder. Past research suggest that bacteria-algae association may play a direct or indirect role in toxin production. As such, ribosomal DNA-based restriction enzyme analysis for the identification of bacteria associated with Pyrodinium sps. was undertaken. A total of 16 bacterial isolates were successfully obtained from the clonal cultures of Pyrodinium sps. The diversity of the extracellular bacteria associated with Pyrodinium bahamense var. compressum was limited to the Phyla Proteobacteria and Actinobacteria. The major bacterial species identified included Alcanivorax spp. and Hyphomonas spp., whereas Kocuria spp., Nesterenkonia spp., Alteromonas spp., Roseobacter spp., Xanthomonas spp., and Acinetobacter spp. were identified as minor isolates. The identified bacterium Hyphomonas spp. exhibited high sequence identity with an unknown bacterium strain, SCRIPPS 739, in the GenBank database that is known to be associated with toxic and non-toxic dinoflagellates, Alexandrium spp. and Scrippsiella trochoidea, respectively. [ABSTRACT FROM AUTHOR]

We examined the environmental and biological factors related to blooms of the toxic dinoflagellate Pyrodinium bahamense in three shallow, restricted subtropical lagoons in the Gulf of California during the rainy summer. In the San José, Yavaros, and El Colorado lagoons, the vegetative stage peaked at 63, 108, and 151 (×103 cells l-1), respectively. At San José, production of cysts peaked at 9.7×103 g-1 of dry sediment mass as the bloom declined. Large diatoms predominated, with P. bahamense the most common dinoflagellate during the blooms. Abundance of P. bahamense at San José was positively correlated with salinity (r=0.50, p=0.0003), seawater temperature (r=0.44, p=0.005), silicates (r=0.45, p=0.003), and ammonium (r=0.32, p=0.005), and negatively correlated with dissolved oxygen (r=-0.34, p<0.0001). No such correlations were found at El Colorado and Yavaros. The environmental window that favors development of blooms is restricted to the summer and is influenced by seawater temperature, salinity, and relative concentrations of ammonium and phosphates that, in turn, depend on rainfall and runoff, which is greater on the eastern side of the Gulf where seawater quality is degraded. [ABSTRACT FROM AUTHOR]