Toxic Alexandrium Tamarense Research Articles

Foraging response and acclimation of ambush feeding and feeding‐current feeding copepods to toxic dinoflagellates

AbstractCopepods exposed to toxic algae in “black box” incubation experiments show highly varied responses, but the mechanisms cannot be revealed from such experiments and the implications to copepod and phytoplankton population dynamics consequently not evaluated. Here, we use direct video observations to examine the response and temporal acclimation (5 d) of two copepods with different foraging behaviors to toxic dinoflagellates. Feeding‐current feeding Temora longicornis and ambush feeding Acartia tonsa were offered three strains of toxic Alexandrium tamarense and a nontoxic control Protoceratium reticulatum. We hypothesize (1) that ambush feeders are less affected by toxic algae than feeding‐current feeders, (2) that copepods acclimate to the toxic algae, and (3) that phytoplankton cells previously exposed to copepod cues elicit stronger responses. Both copepod species consumed the toxic algae at a reduced rate and there was no difference in their net‐response, but the mechanisms differed. T. longicornis responded in strain‐specific ways by reducing its feeding activity, by rejecting captured algae, or by regurgitating consumed cells. A. tonsa reduced its consumption rate, jump frequency, and jump distance on all strains of the toxic dinoflagellate, and most so on copepod‐cue induced cells. There was limited acclimation to algal toxins, although some behavioral responses relaxed or intensified during the first one to several days. Mortality rates were low and the various responses, thus, all allow the copepods to survive harmful algal blooms. However, the implications to algal population dynamics are species/strains specific, with only prey selection providing the toxic algae with a competitive advantage.

Evidence of increased toxic Alexandrium tamarense dinoflagellate blooms in the eastern Bering Sea in the summers of 2004 and 2005.

The eastern Bering Sea has a vast continental shelf, which contains various endangered marine mammals and large fishery resources. Recently, high numbers of toxic A. tamarense resting cysts were found in the bottom sediment surface of the eastern Bering Sea shelf, suggesting that the blooms have recently occurred. However, little is known about the presence of A. tamarense vegetative cells in the eastern Bering Sea. This study's goals were to detect the occurrence of A. tamarense vegetative cells on the eastern Bering Sea shelf and to find a relationship between environmental factors and their presence. Inter-annual field surveys were conducted to detect A. tamarense cells and environmental factors, such as nutrients, salinity, chlorophyll a, and water temperature, along a transect line on the eastern Bering Sea shelf during the summers of 2004, 2005, 2006, 2009, 2012, and 2013. A. tamarense vegetative cells were detected during every sampling year, and their quantities varied greatly from year to year. The maximum cell densities of A. tamarense observed during the summers of 2004 and 2005 were much higher than the Paralytic shellfish poisoning warning levels, which are greater than 100–1,000 cells L-1, in other subarctic areas. Lower quantities of the species occurred during the summers of 2009, 2012, and 2013. A significant positive correlation between A. tamarense quantity and water temperature and significant negative correlations between A. tamarense quantity and nutrient concentrations (of phosphate, silicate, and nitrite and nitrate) were detected in every sampling period. The surface- and bottom-water temperatures varied significantly from year to year, suggesting that water temperatures, which have been known to affect the cell growth and cyst germination of A. tamarense, might have affected the cells' quantities in the eastern Bering Sea each summer. Thus, an increase in the Bering Sea shelf's water temperature during the summer will increase the frequency and scale of toxic blooms and the toxin contamination of plankton feeders. This poses serious threats to humans and the marine ecosystem.

Possible spreading of toxic Alexandrium tamarense blooms on the Chukchi Sea shelf with the inflow of Pacific summer water due to climatic warming

A high abundance of resting cysts of the toxic dinoflagellate Alexandrium tamarense was recently reported in the vast continental shelf of the Chukchi Sea in the Arctic Ocean, suggesting that the species is widespread in the shelf. Nevertheless, little is known about the occurrence of A. tamarense vegetative cells in the water column of the arctic. Sea ice reduction and the inflow of Pacific summer water (PSW) through the Bering Strait have recently increased owing to warming in the shelf. To determine the spatial and temporal distributions of A. tamarense in the Chukchi Sea shelf and their relationship to the inflow of PSW, field samplings were conducted in the Chukchi Sea and north Bering Sea shelves three times during the summer of 2013 from July to October. Vegetative cells of A. tamarense was detected in both shelves at all sampling periods with a maximum density of 3.55×103 cells L−1. This species was also observed at the station at 73°N, indicating the northernmost record of this species to date. The center of the A. tamarense distribution was between the north Bering and south Chukchi Sea shelf during the first collection period, and spread to the north Chukchi Sea shelf during the second and third collection periods. The species occurrences were mainly observed at stations affected by the PSW, especially Bering shelf water. Water structure of PSW was characterized by warmer surface and bottom water temperatures, and increased temperatures may have promoted the cell growth and cyst germination of A. tamarense. Therefore, it is suggested that an increase in the PSW inflow owing to warming promotes toxic A. tamarense occurrences on the Chukchi Sea shelf.

Towards molecular, physiological, and biochemical understanding of photosynthetic inhibition and oxidative stress in the toxic Alexandrium tamarense induced by a marine bacterium

Alexandrium tamarense is a notorious harmful algal bloom species, which is associated with the largest number of paralytic shellfish poisoning cases, causing devastating economic losses and health hazards. The marine bacterium Mangrovimonas yunxiaonensis strain LY01 showed high algicidal effects on A. tamarense. A. tamarense was also susceptible to the supernatant of LY01 as revealed by algicidal activity assay, but washed bacterial cells did not show algicidal activity towards A. tamarense. In this study, we investigated the algicidal effect of the supernatant on growth, photosynthesis and the antioxidative response of A. tamarense. The results indicated that under the algicidal effect of the supernatant, the contents of cellular pigments including chlorophyll a and carotenoids were significantly decreased, and the decline of the maximum quantum yield and relative electron transport rate values suggested that photosynthetic inhibition occurred in the photosystem II system. The content of reactive oxygen species (ROS) increased after 0.5 h exposure, and the surplus ROS induced lipid peroxidation, the destruction of cellular membrane integrity and decreased cellular protein and carbohydrate contents in the algal cells. At the same time, the supernatant also induced the responses of antioxidant enzymes and non-enzymatic antioxidant. The transcription of photosynthesis- and respiration-related genes were significantly inhibited during the exposure procedure, which obstructed photosynthetic efficiency and capacity and disturbed the respiratory system, thereby increasing ROS production again. All these results elaborate clearly the entire procedure by which cellular physiological levels respond to the algicidal bacterium and may contribute to a better understanding of the bacterial control of A. tamarense.

Differential effects of ocean acidification on carbon acquisition in two bloom-forming dinoflagellate species.

Dinoflagellates represent a cosmopolitan group of phytoplankton with the ability to form harmful algal blooms. Featuring a Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) with very low CO2 affinities, photosynthesis of this group may be particularly prone to carbon limitation and thus benefit from rising atmospheric CO2 partial pressure (pCO2) under ocean acidification (OA). Here, we investigated the consequences of OA on two bloom-forming dinoflagellate species, the calcareous Scrippsiella trochoidea and the toxic Alexandrium tamarense. Using dilute batch incubations, we assessed growth characteristics over a range of pCO2 (i.e. 180–1200 µatm). To understand the underlying physiology, several aspects of inorganic carbon acquisition were investigated by membrane-inlet mass spectrometry. Our results show that both species kept growth rates constant over the tested pCO2 range, but we observed a number of species-specific responses. For instance, biomass production and cell size decreased in S. trochoidea, while A. tamarense was not responsive to OA in these measures. In terms of oxygen fluxes, rates of photosynthesis and respiration remained unaltered in S. trochoidea whereas respiration increased in A. tamarense under OA. Both species featured efficient carbon concentrating mechanisms (CCMs) with a CO2-dependent contribution of HCO3− uptake. In S. trochoidea, the CCM was further facilitated by exceptionally high and CO2-independent carbonic anhydrase activity. Comparing both species, a general trade-off between maximum rates of photosynthesis and respective affinities is indicated. In conclusion, our results demonstrate effective CCMs in both species, yet very different strategies to adjust their carbon acquisition. This regulation in CCMs enables both species to maintain growth over a wide range of ecologically relevant pCO2.

Abundance and distribution of toxic Alexandrium tamarense resting cysts in the sediments of the Chukchi Sea and the eastern Bering Sea

Abundance and distribution of the toxic dinoflagellate Alexandrium tamarense species complex resting cyst were investigated in the eastern Bering Sea and the Chukchi Sea for the first time. Sediment samples (top 0–3cm depth) were collected from the continental shelf of the eastern Bering Sea (17 stations) and the Chukchi Sea (13 stations) together with a long core sample (top 0–21cm depth) from one station in the Chukchi Sea during 2009–2012. The cysts were enumerated using the primuline staining method. Species identification of the cysts was carried out with multiplex PCR assay and the plate morphology of vegetative cells germinated from cysts in the both areas. Alexandrium cysts were widely detected in the both areas, ranging from not detected (<1cystscm−3) to 835cystscm−3 wet sediment in the eastern Bering Sea and from not detected (<1cystscm−3) to 10,600cystscm−3 in the Chukchi Sea, and all isolated cysts were genetically and morphologically identified as the North American clade A. tamarense. Their cysts were mainly distributed in the shallow continental shelf where the water depth was less than 100m in both areas. The cysts were detected from the deep layer (18–21cm depth of sediment core) of the long core sample. The present study confirmed the abundant existence of A. tamarense with wide range of distribution in these areas. This fact suggests that A. tamarense vegetative cells have appeared in the water column in the both areas. Furthermore, these abundant cyst depositions indicate that this species originally distributed in the Arctic and subarctic regions and well adapted to the environments in the marginal ice zone.

Molecular detection and species identification of Alexandrium (Dinophyceae) causing harmful algal blooms along the Chilean coastline

On the basis of morphological evidence, the species involved in South American Pacific coast harmful algal blooms (HABs) has been traditionally recognized as Alexandrium catenella (Dinophyceae). However, these observations have not been confirmed using evidence based on genomic sequence variability. Our principal objective was to accurately determine the species of Alexandrium involved in local HABs in order to implement a real-time polymerase chain reaction (PCR) assay for its rapid and easy detection on filter-feeding shellfish, such as mussels. For species-specific determination, the intergenic spacer 1 (ITS1), 5.8S subunit, ITS2 and the hypervariable genomic regions D1-D5 of the large ribosomal subunit of local strains were sequenced and compared with two data sets of other Alexandrium sequences. Species-specific primers were used to amplify signature sequences within the genomic DNA of the studied species by conventional and real-time PCR. Phylogenetic analysis determined that the Chilean strain falls into Group I of the tamarensis complex. Our results support the allocation of the Chilean Alexandrium species as a toxic Alexandrium tamarense rather than A. catenella, as currently defined. Once local species were determined to belong to Group I of the tamarensis complex, a highly sensitive and accurate real-time PCR procedure was developed to detect dinoflagellate presence in Mytilus spp. (Bivalvia) samples after being fed (challenged) in vitro with the Chilean Alexandrium strain. The results show that real-time PCR is useful to detect Alexandrium intake in filter-feeding molluscs. It has been shown that the classification of local Alexandrium using morphological evidence is not very accurate. Molecular methods enabled the HAB dinoflagellate species of the Chilean coast to be assigned as A. tamarense rather than A. catenella. Real-time PCR analysis based on A. tamarense primers allowed the detection of dinoflagellate DNA in Mytilus spp. samples exposed to this alga. Through the specific assignment of dinoflagellate species involved in HABs, more reliable preventive policies can be implemented.

Effects of toxic Alexandrium tamarense on behavior, hemocyte responses and development of brown ring disease in Manila clams

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 430:35-48 (2011) - DOI: https://doi.org/10.3354/meps09111 Effects of toxic Alexandrium tamarense on behavior, hemocyte responses and development of brown ring disease in Manila clams V. M. Bricelj1,*, Susan E. Ford2, Christophe Lambert3, Annaick Barbou3, Christine Paillard3 1Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey 08901, USA 2Haskin Shellfish Research Laboratory, Rutgers University, Port Norris, New Jersey 08349, USA 3Institut Universitaire Européen de la Mer, LEMAR, Technopôle Brest Iroise, 29280 Plouzané, France *Email: mbricelj@marine.rutgers.edu ABSTRACT: In this study of short-term exposure of Ruditapes philippinarum from Brittany, France, to an Alexandrium tamarense isolate that produces high concentrations of paralytic shellfish toxins (PSTs), the effects of the isolate on clam fitness, toxin uptake, and the response of hemocytes (responsible for internal defense in bivalves) were examined. Adults exhibited individual variability in ­resistance to the effects of PSTs, measured by their burrowing capacity. If genetically based, this may (1) indicate that resistance is under natural selection and (2) provide a new model to advance our understanding of the molecular basis for PST resistance in bivalves, so far determined only in Mya arenaria. Juvenile clams were more vulnerable to PSTs than adults, experiencing 100% burrowing incapacitation within 1 d of exposure to A. tamarense. They also experienced growth suppression and high mortalities following 4 d of toxification. Juveniles challenged with Vibrio tapetis, the cause of brown ring disease (BRD), and exposed to A. tamarense, developed significantly fewer BRD symptoms relative to controls fed non-toxic algae, but suffered higher mortality. Adult clams exposed to A. tamarense showed a significant increase in hemocyte concentrations and a small, but significant, decrease in phagocytic activity, and no effect on hemocyte viability or other functional parameters. We speculate that the inhibitory effects on BRD progression may be attributable to toxicity of PSTs to V. tapetis, inability of juveniles to activate the shell conchiolin-deposition response, and/or an overall increase in phagocytic cells induced by A. tamarense. Harmful algae and pathogens may thus ­interact and modulate the effects of disease in bivalve populations. KEY WORDS: Ruditapes philippinarum · Paralytic shellfish toxins · Vibrio · Burrowing · Hemocytes Full text in pdf format PreviousNextCite this article as: Bricelj VM, Ford SE, Lambert C, Barbou A, Paillard C (2011) Effects of toxic Alexandrium tamarense on behavior, hemocyte responses and development of brown ring disease in Manila clams. Mar Ecol Prog Ser 430:35-48. https://doi.org/10.3354/meps09111 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 430. Online publication date: May 26, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Evidence of selection for resistance to paralytic shellfish toxins during the early life history of soft‐shell clam, Mya arenaria, populations

This study identifies early, postmetamorphic soft‐shell clams, Mya arenaria, as the life‐history stage most susceptible to effects of blooms of paralytic shellfish poisoning (PSP) toxin–producing Alexandrium spp. Laboratory experiments used progeny from predominantly susceptible (naϊve) or resistant (annually exposed) NW Atlantic populations. Growth and survival of toxified veliger larvae did not differ from those fed nontoxic algae. In contrast, postlarvae (4–12‐mm shell length) from both populations exposed to a highly toxic Alexandrium tamarense isolate (~ 100 cells mL−1, 64–69 pg saxitoxin equivalents [STXeq] cell−1) suffered burrowing incapacitation, toxin accumulation, and mortalities within 1 week of toxin exposure. These effects were greater and occurred sooner in the naϊve population. Short‐term toxification in the laboratory caused a significant shift in the genotypic composition of this population, determined with a molecular marker for sodium‐channel resistance. Clams with the sensitive genotype were selectively eliminated relative to resistant or heterozygote clams. Ingestion of toxic cells (too large for larval capture) is thus required to elicit toxic effects. Exposure to mixed, toxic, and nontoxic algal suspensions demonstrated that adverse effects to fitness (survival and growth) were dose‐dependent, occurring only at ≥ 50 cells mL−1 of the isolate used (PR18b). Paralysis and thus increased predatory risk occurred even at 10 cells mL−1. Postlarvae &lt; 12 mm, which can co‐occur with red tides throughout the Atlantic range of M. arenaria, were more susceptible to PSP than large (&gt; 30 mm) juveniles. Natural selection for resistance in Atlantic populations will thus vary latitudinally with the timing, duration, and intensity of toxic blooms.

Wind-driven river plume dynamics and toxic Alexandrium tamarense blooms in the St. Lawrence estuary (Canada): A modeling study

In the lower St. Lawrence estuary (LSLE, eastern Canada), blooms of the toxic dinoflagellate Alexandrium tamarense are a recurrent phenomenon, resulting in paralytic shellfish poisoning outbreaks every summer. A first coupled physical–biological model of A. tamarense blooms was developed for this system in order to explore the interactions between cyst germination, cellular growth and water circulation and to identify the effect of physical processes on bloom development and transport across the estuary. The simulated summer (1998) was characterized by an A. tamarense red tide with concentrations reaching 2.3 × 10 6 cells L −1 along the south shore of the LSLE. The biological model was built with previously observed A. tamarense cyst distribution, cyst germination rate and timing, and A. tamarense growth limitation by temperature and salinity. The coupled model successfully reproduced the timing of the A. tamarense bloom in 1998, its coincidence with the combined plumes from the Manicouagan and Aux-Outardes (M-O) rivers on the north shore of the estuary, and the temporal variations in the north-south gradients in cell concentrations. The simulation results reveal that the interaction between cyst germination and the estuarine circulation generates a preferential inoculation of the surface waters of the M-O river plume with newly germinated cells which could partly explain the coincidence of the blooms with the freshwater plume. Furthermore, the results suggest that the spatio-temporal evolution of the bloom is dominated by alternating periods of retention and advection of the M-O plume: east or north-east winds favor the retention of the plume close to the north shore while west or north-west winds result in its advection toward the south shore. The response of the simulated freshwater plume to fluctuating wind forcing controls the delivery of the A. tamarense bloom from the northern part of the estuary to the south shore. In addition, our results suggest that a long residence time of the M-O plume and associated A. tamarense population in the LSLE during the summer 1998 contributed to the development of the red tide. We thus hypothesize that the wind-driven dynamics of the M-O plume could partly determine the success of A. tamarense blooms in the LSLE by influencing the residence time of the blooms and water column stability, which in turn affects A. tamarense vertical migrations and growth.

독성 Alexandrium tamarense를 섭취한 담치류 4종의 마비성패독 축적

Cultured cells of the toxic Alexandrium tamarense were fed to four mussel species, Mytilus coruscus, M. edulis, M. galloprovincialis and Septifer vulgatus, to examine the interspecies and interlocality differences in the ability to accumulate paralytic shellfish poisoning (PSP) toxins. Toxin content of A. tamarense cells varied during culture period. In contrast, toxin composition in the cell (C1,2, GTX1-4 and neoSTX) was constantly stable. In feeding experiment, the four mussel species collected from Geoje intoxicated after uptake of A. tamarense. Toxin content (<TEX>$average{\pm}SD\;{\mu}g$</TEX> STXeq/100 g) of M. coruscus, M. edulis, M. galloprovincialis and Septifer vulgatus were <TEX>$1,660{\pm}79,\;3,914{\pm}2,242,\;5,626{\pm}1,620\;and\;958{\pm}163$</TEX>, respectively. Toxin profiles included C1,2, GTX1,4 and neoSTX as the major components, and dcGTX2,3, GTX2,3, neoSTX and STX as the minor ones. Toxin accumulation of three mussel species collected from Pohang, Geoje and Anmyon-do showed interspecies and interlocality differences. Toxin content (<TEX>$average{\pm}SD\;{\mu}g$</TEX> STXeq/100 g) were <TEX>$91{\pm}4,\;151{\pm}14,\;39{\pm}3$</TEX> in M coruscus, <TEX>$189{\pm}1,\;231{\pm}11,\;206{\pm}15$</TEX> in M edu/is and <TEX>$214{\pm}28,\;326{\pm}30,\;291{\pm}26$</TEX> in M. galloprovincialis in order of Anmyon-do, Geoje and Pohang.

Erratum to: Bacterial diversity in toxic Alexandrium tamarense blooms off the Orkney Isles and the Firth of Forth

Erratum to: Bacterial diversity in toxic Alexandrium tamarense blooms off the Orkney Isles and the Firth of Forth

Erratum to Bacterial diversity in toxic Alexandrium tamarense blooms off the Orkney Isles and the Firth of Forth

The genetic diversity of the bacterial community associated with Alexandrium tamarense blooms was studied in blooms of the toxic dinoflagellates in the waters around the Orkney Isles and the Firth of Forth (Scotland). For toxin and molecular analysis of the bacterial communities associated with the toxic bloom, water samples were taken in 1998 and 1999 from A. tamarense blooms. The bacterial community structure, as determined by DGGE (denaturing gradient gel electrophoresis) showed clear differences between all three investigated size fractions (dinoflagellate-associated bacteria, attached bacteria and free-living bacteria), with high diversity within each sample. DNA sequence analysis of the dominant and most frequent DGGE bands revealed the dominance of α Proteobacteria, mainly of the Roseobacter clade, with similarities of 91–99%. Moreover, DGGE bands occurring at the same position in the gel throughout in most samples corroborate the presence of several specific α Proteobacteria of the Roseobacter clade. Overall, 500 bacteria were isolated from the bloom and partly phylogenetically analysed. They were members of two prokaryotic phyla, the Proteobacteria and the Bacteroidetes, related to Proteobacteria of the α and γ subdivisions (Alteromonas, Pseudoalteromonas and Colwellia). All bacteria were tested for the production of sodium channel blocking (SCB) toxins using mouse neuroblastoma assay. No production of SCB toxins was found and high performance liquid chromatography (HPLC) analysis confirmed these results. The content of total paralytic shellfish poisoning (PSP) toxin in the water samples, as measured within the toxic dinoflagellate blooms using HPLC, ranged from 53 to 2191 ng PSP l−1 in 1998 and from 0 to 478 ng PSP l−1 in 1999. Changes in PSP toxin content were not accompanied by changes of DGGE band patterns. We therefore presume that the bacterial groups identified in this study were not exclusively associated with toxic A. tamarense, but were generally associated with the phytoplankton.