Bahamense Var Research Articles

Harmful blooms caused by dinoflagellates in the Pacific of Guatemala (2019–2022)

Plankton studies in Guatemala are associated with the history of harmful algal blooms (HAB). An important event was observed in 1987, with 193 human poisonings due to shellfish consumption, of which 22 were lethal. The causative organism was Pyrodinium bahamense var. compressum. This species was reported again in November 2019 in the coastal Guatemalan Pacific. The species reached an abundance of 1 × 104 cells/L. In September 2020, the abundance of the Margalefidinium polykrikoides vegetative stage reached 1.24 × 106 cells/L, and its cysts 1.5 × 106 cells/L. Noctiluca scintillans proliferated (the first quantitatively estimated bloom of this species in Guatemala) in November 2020 and March 2021 (up to 1.2 × 106 cells/L). From January to December 2021, monthly monitoring was carried out in front of the Port of Quetzal at three sites (bottle and 25 μm mesh net samples). In April 2022, 11 cases of humans presenting symptoms of paralytic shellfish poisoning (PSP) were recorded in the western sector of the Guatemalan Pacific, in particular, in the municipality of Tiquisate in the department of Escuintla. From May 3 to 27, 2022, a HAB event caused the death of 4 and the poisoning of 34 humans in the departments near Mexico: Retalhuleu (Champerico), San Marcos (Tilapa) and Escuintla (Tiquisate, Buena Vista and Iztapa). The maximum saxitoxin (STX) concentration was determined in Retalhuleu (14,099 MU/100 g); until 7 July 2022, STX continued to be detected in Tilapa and Tiquisate (1,021 MU/100 g). The P. bahamense cells were observed in the stomach contents of the clam Tagelus sp. (Bivalvia: Solecurtidae).

Comprehensive analysis of harmful algal blooms in indonesia: from occurrence to impact

The occurrence and frequency of harmful algal blooms have become a significant problem in Indonesia's coastal waters since 1991. This article aims to thoroughly analyze the diversity of algal species involved in these harmful algal blooms (HABs). It highlights that some algae, such as toxic species, can produce dangerous toxins, while others, such as non-toxic algae, remain harmless. This article reviews research studies that describe the occurrence, frequency, and causative types of bloom events in several contaminated coastal regions of Indonesia. The blooms had many consequences for fisheries, the aquatic environment, the economy, and public health. Among the identified species, Pyrodinium bahamense var. compressum is known for its high toxicity. The most common taxa contributing to bloom tragedy are Chaetoceros, Noctiluca, and Skeletonema. The study recognizes that human-induced nutrient enrichment is a major and significant factor in triggering the bloom phenomena. The paper recommends various management strategies and further research initiatives to prevent and reduce the impacts of HABs in Indonesia.

Amplification of Genes Associated with Saxitoxin Biosynthesis in Bacteria Associated with Pyrodinium bahamense var. compressum Using Primers Designed from Other Saxitoxin-Producing Organisms

Pyrodinium bahamense var. compressum, the primary producer of saxitoxin (STX) in tropical water, poses a palpable threat to public health and safety. Seafood and aquaculture products contaminated with lethal concentrations of the principal neurotoxin, saxitoxin, have been implicated in mortality and morbidity. Previous research revealed that the relationship between bacteria and algae may contribute directly or indirectly to the synthesis of saxitoxin. This study investigates the potential relationship between the dinoflagellate and its associated bacteria; hence the initial step is to determine whether the genes responsible for the STX production in P. bahamense can be found in the associated bacteria. A total of six bacterial species associated with P. bahamense were successfully identified in a previous study. The presence of the sxt genes in the associated bacterial genome was determined using primers that have previously been utilized in other saxitoxin-producing species, such as in dinoflagellates (Alexandrium fundyense) and cyanobacteria (Anabaena and Aphanizomenon gracile). This study showed that the utilized primers were unsuitable as the primers produced non-specific amplification in the bacterial genome. We suggest that specific primers targeting the sxt homolog genes in bacterial species should be designed to obtain the desired genes from the associated bacteria in a future study.

Paralytic Shellfish Profiles Produced by the Toxic Dinoflagellate Pyrodinium bahamense from Sepanggar Bay, Malaysia

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.

CHARACTERIZATION OF THE SAXITOXIN BIOSYNTHETIC STARTING GENE, sxtA, IN THE TOXIC DINOFLAGELLATE, Pyrodinium bahamense var. compressum

Pyrodinium bahamense var. compressum, a saxitoxin-producing dinoflagellate, frequently blooms on the west coast of Sabah. According to previous studies, saxitoxin from cyanobacteria and dinoflagellates is manufactured from similar precursors (three arginines, one methionine via S-adenosylmethionine and one acetate) through identical biochemical pathways. The saxitoxin biosynthetic starting gene, sxtA is essential for synthesizing the final compound. The genes associated with saxitoxin synthesis in Alexandrium spp. and cyanobacteria have been previously identified; in spite of this, limited information is known about P. bahamense var. compressum, the principal tropical saxitoxin-producing dinoflagellate. In this study, the exclusive starting gene for saxitoxin biosynthesis, sxtA, specifically the SAM-dependent methyltransferase, sxtA1 and the class II aminotransferase coding gene, sxtA4 of P. bahamense was studied. Comparative sequence analysis revealed that sxtA1 and sxtA4 genes in P. bahamense exhibited high sequence similarity with other toxic dinoflagellates such as Alexandrium fundyense and Alexandrium tamarense. This study provides a genetic insight into saxitoxin biosynthesis in P. bahamense, which will be helpful in future investigations such as the development of genetic markers to study the expression of the sxtA gene and the identification of potential molecular targets for bloom characterization.

Bacterial community associated with Pyrodinium bahamense var. compressum during late exponential growth phase based on 16S rRNA gene sequence analysis

Bacterial community associated with Pyrodinium bahamense var. compressum during late exponential growth phase based on 16S rRNA gene sequence analysis

A metagenomic study of bacterial communities associated with the saxitoxin producing dinoflagellate, Pyrodinium bahamense var. compressum

A metagenomic study of bacterial communities associated with the saxitoxin producing dinoflagellate, Pyrodinium bahamense var. compressum

Monsoonal variation of the marine phytoplankton community in Kota Kinabalu, Sabah

Monsoon-driven changes of environmental factors have been reported to be significantly variable and affects the phytoplankton community in tropical waters. This study examined the monsoonal changes of environmental parameters and the coastal phytoplankton community, including potential harmful algal bloom species, in the waters of Kota Kinabalu, Sabah, Malaysia. Bi-weekly observations were conducted from August 2017 to January 2019, covering the Southwest Monsoon (SWM), Northeast Monsoon (NEM), and inter-monsoon periods (IMPs). Sea surface temperature, salinity, and daily average photosynthetic active radiation (PAR) were significantly different between the SWM and the NEM. Total phytoplankton densities were significantly higher in the SWM with median cell densities of 1.12 × 104 cells L−1 compared to the NEM with 3.98 × 103 cells L−1. Nutrient measurements indicated that the waters were mesotrophic, with low phosphate (P) levels (<0.3 μM-P on average). N:P ratios were often above the Redfield ratio (16N:1P), while high Si:N (>1) and Si:P ratios (>16Si:1P) indicated that silicate was not limiting, a condition favourable for diatom growth. Phytoplankton dynamics shifted from a dinoflagellate-dominant community (Protoperidinium spp. and Prorocentrum spp.) to a diatom-dominant community (Leptocylindrus spp. and Dactyliosolen spp.) during the NEM, which was preceded by a peak in silicate and nitrate. Later, Chaetoceros spp. became dominant during the second SWM. The presence of intermittent increases in Margalefidinium polykrikoides and Pyrodinium bahamense var. compressum cell densities may trigger future blooms in these waters. Canonical Correspondence Analysis suggests that the dinoflagellate-dominant community was driven by changes in PAR and Si:N while changes in N:P and salinity shaped the diatom-dominant community. The shifts of the phytoplankton community composition in relation to the different monsoonal periods suggests that the monsoons function as environmental drivers which structure the phytoplankton community of this coastal ecosystem.

Co-ocurrence of two toxic dinoflagellates in Acapulco Bay, Guerrero, Mexico: an opportunity to quantify their biology and ecology

Abstract:Background and Aims: Harmful Algal Blooms (HAB) commonly occur in the Mexican Pacific, being important HABs of Gymnodinium catenatum (Gc) and of Pyrodinium bahamense var. compressum (Pbc) for being saxitoxin-producing dinoflagellates that cause paralytic shellfish poisoning. The latter is a taxon that sporadically occurs in the tropical Mexican Pacific. This study describes the behavior of both taxa throughout the annual cycle and analyzes their morphology, abundance, distribution, and their bloom dynamics, in relation to environmental and climatological parameters.Methods: Phytoplankton collections were made ten times from October 2009 to January 2011 within Acapulco Bay and its surroundings, together with measurements of physicochemical parameters. Climatic data were obtained from Acapulco weather station. Abundance of phytoplankton was evaluated with the Utermöhl method. Statistical analyses were carried out to investigate the relationship of Gc and Pbc abundances with environmental and climatic parameters. Key results: Gc was present throughout the year 2010 in low densities and in November 2010 it reached a maximum of 189×103 cells l-1, associated with several species of diatoms and dinoflagellates, including Pbc. Gc bloom coincided with decrease in ammonium and decrease in water temperature with respect to the average. Pyrodinium bahamense morphometry from Acapulco corresponds to var. compressum. Pbc formed an intense HAB in July 2010 (reaching a maximum abundance of 773×103 cells l-1), causing significant toxicity and had an upturn in November. Conclusions: Pbc HABs in Acapulco require the occurrence of a previous HAB in the central Pacific or Gulf of Tehuantepec, Mexico, horizontal transportation of their cysts, as well as high water temperature conditions, abundant rainfall that increased the concentration of phosphates, which is propitiated in the periods of transition El Niñoˮ-La Niñaˮ events. Gc HABs in Acapulco are related to “La Niña” events, with an abrupt change in water temperature and an increase in nitrogenous forms.Key words: ENSO, Gymnodinium catentum, HAB, Mexican tropical Pacific, morphometry, Pyrodinium bahamense var. compressum. Resumen:Antecedentes y Objetivos: Los florecimientos algales nocivos (FAN) ocurren comúnmente en el Pacífico mexicano, siendo importantes los de Gymnodinium catenatum (Gc) y Pyrodinium bahamense var. compressum (Pbc), dinoflagelados productores de saxitoxina que causan envenenamiento paralítico por mariscos. Pbc se presenta esporádicamente en el Pacifico tropical mexicano. El estudio describe el comportamiento de ambos taxa en un ciclo anual y analiza su morfología, abundancia, distribución y dinámica del FAN en relación con parámetros ambientales y climatológicos. Métodos: Se realizaron diez recolectas de fitoplancton (octubre 2009-enero 2011) en la Bahía de Acapulco y zona costera adyacente, y mediciones de parámetros fisicoquímicos. Los datos climáticos se obtuvieron de la estación meteorológica de Acapulco. La abundancia del fitoplancton se evaluó con el método de Utermöhl. Se realizaron análisis estadísticos para investigar la relación de las abundancias de Gc y Pbc con parámetros ambientales y climáticos. Resultados clave: Gc estuvo presente durante todo el año 2010 con densidades bajas; en noviembre de 2010 alcanzó un máximo de 189×103 células l-1, asociado con especies de diatomeas y dinoflagelados, incluyendo Pbc. El florecimiento de Gc coincidió con disminución de amonio y disminución de temperatura del agua con respecto al promedio. La morfometría de Pb de Acapulco correspondió con la var. compressum. Pbc formó un intenso FAN en julio de 2010 (abundancia máxima de 773×103 células l-1), causando una toxicidad significativa y tuvo un repunte en noviembre. Conclusiones: Los FAN de Pbc en Acapulco requieren un FAN previo en el Pacífico central o en el Golfo de Tehuantepec, transporte horizontal de sus quistes, alta temperatura del agua y abundante precipitación que aumente la concentración de fosfatos; condiciones que se propician en los períodos de transición”El Niño”-La Niña”. Los FAN de Gc en Acapulco están relacionados con eventos “La Niña”, siendo importantes el cambio abrupto de temperatura del agua y el aumento de formas nitrogenadas.Palabras clave: ENSO, FAN, Gymnodinium catentum, morfometría, Pacífico tropical mexicano, Pyrodinium bahamense var. compressum.

Planktonic algal blooms from 2000 to 2015 in Acapulco Bay, Guerrero, Mexico

Background and Aims: Harmful algal blooms (HABs) affect the marine ecosystem in multiple ways. The objective was to document the species that produced blooms in Acapulco Bay over a 15-year period (2000-2015) and analyze the presence of these events with El Niño-Southern Oscillation (ENSO).Methods: Thirty-five collections, made during the years 2000, 2002-2004, 2006-2011, 2013-2015, were undertaken with phytoplankton nets and Van Dorn bottle, yielding 526 samples, of which 423 were quantified using the Utermöhl method. The relationship of HAB with ENSO was made with standardized values of Multivariate ENSO Index (MEI) and the significance was evaluated with the method quadrant sums of Olmstead-Tukey.Key results: Using data of cell density and high relative abundance (&gt;60%), 53 blooms were recorded, most of them occurring during the rainy season (June-October) and dry-cold season (November-March), plus 37 blooms reported by other authors. These 90 blooms were composed of 40 taxa: 21 diatoms and 19 dinoflagellates, the former mostly innocuous. Sixty-seven blooms had species reported as noxious, of which 11 species commonly produce toxic HAB. Toxic taxa are Pseudo-nitzschia spp. (four taxa), and seven dinoflagellates.Conclusions: Abundance analyses of Pyrodinium bahamense var. compressum and Gymnodinium catenatum against values of MEI showed a clear tendency to produce HAB in La Niña conditions. Both taxa, producers of saxitoxins, cause paralytic shellfish poisoning (PSP) and coexist in Acapulco; therefore, they present a risk to human health. Another noxious 52 taxa found in Acapulco were currently considered potential HABs, because they have been recorded at low densities. Given the sharp differences in density values of bloom-forming species found in this work compared to those reported by other authors on similar dates, it is important to perform calibration tests to rule out possible errors in cell counts.

Insights into the dynamics of harmful algal blooms in a tropical estuary through an integrated hydrodynamic-Pyrodinium-shellfish model

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.

Increase in Dissolved Silica of Rivers Due to a Volcanic Eruption in an Estuarine Bay (Sorsogon Bay, Philippines)

Mount Bulusan, the Philippines’ fourth most active volcano, erupted in February 21, 2011, sending volcanic ash and pyroclastic materials to its surrounding rivers. The waters drained into the estuary of harmful algal blooms plagued Sorsogon Bay. We aim to determine the impact of the 2011 volcanic eruption and the preceding volcanic ash emissions to the dissolved silica concentration of rivers draining the flanks of Mt. Bulusan and its possible implications to the phytoplankton assemblage of the bay. Six river water sampling periods from August 2010 to October 2012 overlapped with Mt. Bulusan’s active phase of volcanism. Our data shows that mean river silica from pre-eruption levels of ~ 500 μM increased by more than 200% during and post-eruption. Highest Si concentration of 2270 μM was measured from Cadacan River in August 2011. Here, we argue that the sustained general increase of dissolved silica is due to the silica-containing materials from Mt. Bulusan’s eruption and that their concentration in river waters is also a function of watershed lithology and precipitation. Increase in dissolved silica and other nutrients caused a shift to diatom domination and, possibly, termination of Pyrodinium bahamense var. compressum blooms. Silica load increase in embayments is a natural process that controls the dominance of algae. Our study also highlights the importance of Philippine rivers to the global ocean silica budget as a function of high precipitation, tectonics in general, and volcanism in particular.

Bioluminescence in Dinoflagellates: Evidence that the Adaptive Value of Bioluminescence in Dinoflagellates is Concentration Dependent.

Three major hypotheses have been proposed to explain why dinoflagellate bioluminescence deters copepod grazing: startle response, aposematic warning, and burglar alarm. These hypotheses propose dinoflagellate bioluminescence (A) startles predatory copepods, (B) warns potential predators of toxicity, and (C) draws the attention of higher order visual predators to the copepod's location. While the burglar alarm is the most commonly accepted hypothesis, it requires a high concentration of bioluminescent dinoflagellates to be effective, meaning the bioluminescence selective advantage at lower, more commonly observed, dinoflagellate concentrations may result from another function (e.g. startle response or aposematic warning). Therefore, a series of experiments was conducted to evaluate copepod grazing (Acartia tonsa) on bioluminescent dinoflagellates (during bioluminescent and nonbioluminescent phases, corresponding to night and day, respectively) at different concentrations (10, 1000, and 3000 cells mL-1 ), on toxic (Pyrodinium bahamense var. bahamense) and nontoxic (Lingulodinium polyedrum) bioluminescent dinoflagellates, and in the presence of nonluminescent diatoms (Thalassiosira eccentrica). Changes in copepod ingestion rates, clearance rates, and feeding preferences as a result of these experimental factors, particularly during the mixed trails with nonluminescent diatoms, indicate there is a concentration threshold at which the burglar alarm becomes effective and below which dinoflagellate bioluminescence functions as an aposematic warning.

Size-dependent changes in toxicity of Perna viridis mussels exposed to natural populations of Pyrodinium bahamense var. compressum

The mussel Perna viridisis used in the Philippine saxitoxin monitoring program as an indicator organism for the presence of saxitoxin in shellfish in an effort to assess concentration beyond a level considered safe for public consumption. Saxitoxin bioaccumulates in mussels through ingestion of saxitoxin-producing algae Pyrodinium bahamense var. compressum(Pbc). This study focuses on the relationship between mussel length and mussel toxicity in mussels exposed to a natural bloom of Pbc. Mussel toxicity was assessed weekly in a 134-day sampling period using Receptor Binding Assay (RBA). Smaller mussels are more toxic than larger mussels at low Pbc cell density (≈102 cells/L) and the reverse is true at higher Pbc cell density (≈5×103 cells/L). These results can be useful in developing strategies for the collection of mussel samples in a toxic algal bloom monitoring program.

Potential DMSP-degrading Roseobacter clade dominates endosymbiotic microflora of Pyrodinium bahamense var. compressum (Dinophyceae) in vitro.

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.

Lethal paralytic shellfish poisoning from consumption of green mussel broth, Western Samar, Philippines, August 2013.

In July 2013, the Philippines' Event-Based Surveillance & Response Unit received a paralytic shellfish poisoning (PSP) report from Tarangnan, Western Samar. A team from the Department of Health conducted an outbreak investigation to identify the implicated source and risk factors in coastal villages known for green mussel production and exportation. A case was defined as a previously well individual from Tarangan, Western Samar who developed gastrointestinal symptoms and any motor and/or sensory symptoms after consumption of shellfish from 29 June to 4 July 2013 in the absence of any known cause. The team reviewed medical records, conducted active case finding and a case-control study. Relatives of cases who died were interviewed. Sera and urine specimens, green mussel and seawater samples were tested for saxitoxin levels using high performance liquid chromatography. Thirty-one cases and two deaths were identified. Consumption of > 1 cup of green mussel broth was associated with being a case. Seawater sample was positive for Pyrodinium bahamense var. compressum and green mussel samples were positive for saxitoxin. Inspection revealed villagers practice open defecation and improper garbage disposal. This PSP outbreak was caused by the consumption of the green mussel broth contaminated by saxitoxin. As a result of this outbreak, dinoflagellate and saxitoxin surveillance was established, and since the outbreak, there have been no harmful algal blooms event or PSP case reported since. A "Save Cambatutay Bay" movement, focusing on proper waste disposal practice and clean-up drives has been mobilized.

PUBLIC AWARENESS ON HARMFUL ALGAL BLOOM (HAB) IN LAMPUNG BAY

Harmful algal blooms (HABs) cause various problems, such as water quality degradation, fauna mass mortality and impairment of human health. Water quality monitoring in Lampung Bay has been conducted by Lampung Marine Aquaculture Office (BBL) of the Ministry of Marine Affairs and Fisheries since 1994. Occurrence of Pyrodinium bahamense var. compressum (Pbc), a causative organism of paralytic shellfish poisoning (PSP), has been recorded but threats caused by HABs have never been reported. A study aimed to know the level of public knowledge and awareness about HABs in Lampung Bay has been conducted. The components of group respondents consisted oflocal governments, academics and coastal communities. Awareness from each component was examined includinggeneral HAB knowledge, HAB impact to the community, HAB occurence and local knowledge of HAB. Data of HAB knowledge were collected through questionnaire and focus group discussion. The result showed that 40.5% of respondents had knowledge of HABs phenomena and 51.3% respondents only know signs or indicators of HAB occurrence, while only 1.4% respondents had knowledge of local HAB occurences. The direct impact of HABs to the community was not commonly known by the respondents. Only a few cases of poisoning after eating seafood were reported. It can be concluded that there was lack of public knowledge and awareness on HABs in LampungBay. Intensive public awareness programs about HABs should be conducted in order to reduce risk towards HABs in Lampung Bay.

RECENT BLOOMING OF PYRODINIUM BAHAMENSE VAR. COMPRESSUM IN AMBON BAY, EASTERN INDONESIA

In Indonesia, Pyrodinium bahamense var. compressum was first recorded in Kao Bay in 1994. In 1996 the illness of more than 30 people and the death of 3 children after consuming shellfish from Ambon Bay was reported. Until the shellfish poisoning cases was reported, occurrences and blooms of P. bahamense, neither its toxic events had never been known in Ambon Bay. It has generated monitoring on the species occurrence which has been carried out since 2008. The bloom of P. bahamense was detected in July 2012. During the bloom event, concentrationsof phosphate, nitrate and dissolved oxygen were measured. Vertical profiles of temperature, salinity, turbidity and chlorophyll a were also measured during the red tide. Cells of P. bahamense, the PSP responsible species, were recorded abundant up to 2,496 cells/ml when red-brown water discoloration was observed in Ambon Bay. After the toxic red tide, human illness of 7 people due to shellfish consumption was also reported. In addition, the bloom event has damaged aquaculture products, due to mass mortality of cultured fish in inner Ambon Bay.

Cyst morphology, germination characteristics, and potential toxicity of Pyrodinium bahamense in the Gulf of California

Abstract 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).

Development, morphological characteristics and viability of temporary cysts of Pyrodinium bahamense var. compressum (Dinophyceae) in vitro

Pellicle or temporary cysts of Pyrodinium bahamense var. 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) a and no detectable chl c. 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 observed in 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 of P. bahamense var. compressum.