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Harmful algal blooms (HABs) present a potential danger for human health and commercial activities, especially in coastal regions. Observing systems increasingly rely on remote sensors to monitor and possibly predict the locations and intensity of such blooms. Here we present a novel approach for detecting HABs of Alexandrium fundyense in the Bay of Fundy, Canada. A . fundyense is considered toxic for individuals who consume shellfish when cell abundances adjacent to shellfish harvesting areas are as low as 200 cells·L −1 , making it difficult to use direct remote sensing techniques to assess the threat in the early stages of the development of the bloom. Using in situ A . fundyense cell abundance measurements, together with satellite observations of sea-surface temperature and the occurrence of diatom-dominated phytoplankton populations, a warning system was developed based on three levels of alerts: green (low abundance of A . fundyense ), orange (possible threat of A . fundyense ) and red (high probability of A . fundyense concentrations that would result in shellfish toxicity above safe levels for human consumption). Combined information on diatom phenology and variations in sea-surface temperature are key to the timing of A . fundyense blooms: our data reveal that the termination of the diatom spring bloom, associated with the warming of the water, can trigger an increase in A . fundyense cell abundance. The objective criteria for a HAB warning system was developed and tested in the Bay of Fundy using two different datasets: one to develop the algorithm (data collected between 1998 and 2007) and one to assess its performance (data collected in 2011). The warning system is based on the cautionary principle that a false negative (warning not issued when it should have been) is far more serious than a false positive (warning issued when it should not have been). The overall success of the algorithm when tested on the validation dataset is about 70% using a threshold of 150 A . fundyense cells·L −1 , with a low occurrence of false negative red alerts (<8%). The satellite-data-based warning can be used to optimize an in situ monitoring system, which can be designed to be more intensive when the warning status is orange or red. This study demonstrates that combined satellite information on phytoplankton phenology and sea-surface temperature can help predict low abundances of toxic A . fundyense cells. It also highlights the importance of an integrated approach combining satellite and in situ observations to monitor HABs. [ABSTRACT FROM AUTHOR]

Chilean waters are often affected by Alexandrium catenella , one of the leading organisms behind Harmful Algae Blooms (HABs). Genetic variability for this species are commonly carried out from cultured samples, approach that may not accurately quantify genetic variability of this organism in the water column. In this study, genetic variability of A. catenella was determined by sequencing the rDNA region, in water samples from the Canal Puyuhuapi (South Austral Ecosystem of Chile). A. catenella was detected in 8,8% of samples analysed. All sequences obtained were A. catenella (Tamara complex group I), with three highly frequent haplotypes (34%), and twenty new haplotypes. These haplotypes increase the genetic variability from 2.8% to 3.14% in this area. Through this new method, genetic determination of A. catenella can accurately be monitored and ecological studies of this species can be implemented. [ABSTRACT FROM AUTHOR]

Abundant cyst distributions of the toxic dinoflagellate Alexandrium fundyense (previous A. tamarense north American clade) were recently observed on the north Chukchi Sea shelf and on the eastern Bering Sea shelf, suggesting that A. fundyense is both highly adapted to the local environments in the high latitude areas and might cause toxin contamination of plankton feeders. However, little is known about the physiological characteristics and toxin profiles of A. fundyense in these areas, which are characterized by low water temperatures, weak sunlight, and more or less permanent ice cover during winter. To clarify the physiological characteristics of A. fundyense , the effects of water temperature and light intensity on the vegetative growth and toxin profiles of this species were examined using A. fundyense strains isolated from one sediment sample collected from each area. Using the same sediments samples, seasonal changes of the cyst germination in different water temperatures were investigated. Vegetative cells grew at temperatures as low as 5 °C and survived at 1 °C under relatively low light intensity. They also grew at moderate water temperatures (10–15 °C). Their cysts could germinate at low temperatures (1 °C) and have an endogenous dormancy period from late summer to early spring, and warmer water temperatures (5–15 °C) increased germination success. These physiological characteristics suggest that A. fundyense in the Chukchi Sea and eastern Bering Sea is adapted to the environments of high latitude areas. In addition, the results suggest that in the study areas A. fundyense has the potential to germinate and grow when water temperatures increase. Cellular toxin amounts of A. fundyense strains from the eastern Bering Sea and Chukchi Sea were ranged from 7.2 to 38.2 fmol cell −1 . These toxin amounts are comparable with A. fundyense strains isolated from other areas where PSP toxin contamination of bivalves occurs. The dominant toxin of the strains isolated from the Chukchi Sea was saxitoxin, while most A. fundyense strains from the eastern Bering Sea are dominated by the C2 toxin. Toxin profiles similar to those detected in Chukchi Sea have not been reported by any previous research. The dominance of a highly toxic PST variant in Chukchi A. fundyense suggests that presence of the species at low cell concentrations may cause toxin contamination of predators. This study revealed that abundant A. fundyense cysts deposited on the eastern Bering Sea and Chukchi Sea shelves potentially germinate and grow with PSP toxin contents in the local environments. In conclusion, a high risk of PSP occurrences exists on the eastern Bering Sea and Chukchi Sea shelves. [ABSTRACT FROM AUTHOR]

While cyst germination may be an important factor for the initiation of harmful/toxic blooms, assessments of the fluctuation in phytoplankton cyst germination, from bottom sediments to water columns, are rare in situ due to lack of technology that can detect germinated cells in natural bottom sediments. This study introduces a simple mesocosm method, modeled after previous in situ methods, to measure the germination of plankton resting stage cells. Using this method, seasonal changes in germination fluxes of toxic dinoflagellates resting cysts, specifically Alexandrium fundyense ( A. tamarense species complex Group I) and A. pacificum ( A. tamarense species complex Group IV), were investigated at a fixed station in Kesennuma Bay, northeast Japan, from April 2014 to April 2015. This investigation was conducted in addition to the typical samplings of seawater and bottom sediments to detect the dinoflagellates vegetative cells and resting cysts. Bloom occurrences of A. fundyense were observed June 2014 and February 2015 with maximum cell densities reaching 3.6 × 10 6 cells m −2 and 1.4 × 10 7 cells m −2 , respectively. The maximum germination fluxes of A. fundyense cysts occurred in April 2014 and December 2014 and were 9.3 × 10 3 cells m −2 day −1 and 1.4 × 10 4 cells m −2 day −1 , respectively. For A. pacificum , the highest cell density was 7.3 × 10 7 cells m −2 during the month of August, and the maximum germination fluxes occurred in July and August, reaching 5.8 × 10 2 cells m −2 day −1 . Thus, this study revealed the seasonal dynamics of A. fundyense and A. pacificum cyst germination and their bloom occurrences in the water column. Blooms occurred one to two months after peak germination, which strongly suggests that both the formation of the initial population by cyst germination and its continuous growth in the water column most likely contributed to toxic bloom occurrences of A. fundyense and A. pacificum in the bay. [ABSTRACT FROM AUTHOR]

Alexandrium fundyense is a toxic marine dinoflagellate responsible for 'red tide' events in temperate and sub-arctic waters worldwide. In the Gulf of Maine (GOM) and Bay of Fundy in the Northwest Atlantic, blooms of A. fundyense recur annually and are associated with major health and ecosystem impacts. In this region, microsatellite markers have been used to investigate genetic structure and gene flow; however, the loci currently available for this species were isolated from populations from Japan and the North Sea, and only a subset is suitable for the analysis of A. fundyense populations in the Northwest Atlantic. To facilitate future studies of A. fundyense blooms, both in this region and globally, we isolated and characterized 17 polymorphic microsatellite loci from 31 isolates collected from the GOM and from the Nauset Marsh System, an estuary on Cape Cod, Massachusetts, USA. These loci yielded between two and 15 alleles per locus, with an average of 7.1. Gene diversities ranged from 0.297 to 0.952. We then analyzed these same 31 isolates using previously published markers for comparison. We determined the new markers are sufficiently variable and better suited for the investigation of genetic structure, bloom dynamics, and diversity in the Northwest Atlantic. [ABSTRACT FROM AUTHOR]

Understanding interactions between harmful algal bloom (HAB) species and their grazers is essential for determining mechanisms of bloom proliferation and termination. We exposed the common calanoid copepod, Temora longicornis to the HAB species Alexandrium fundyense and examined effects on copepod survival, ingestion, egg production and swimming behaviour. A. fundyense was readily ingested by T. longicornis and significantly altered copepod swimming behaviour without affecting copepod survival or fitness. A. fundyense caused T. longicornis to increase their swimming speed, and the straightness of their path long after the copepods had been removed from the A. fundyense treatment. Models suggest that these changes could lead to a 25-56% increase in encounter frequency between copepods and their predators. This work highlights the need to determine how ingesting HAB species alters grazer behaviour as this can have significant impacts on the fate of HAB toxins in marine systems. [ABSTRACT FROM AUTHOR]

The dinoflagellate Alexandrium produces paralytic shellfish poisoning toxins. The genus is globally distributed, with Scottish waters being of particular interest due to the co-occurrence of different species and strains. In Scottish waters, Alexandrium was historically thought to be dominated by the highly toxic (Group I) Alexandrium fundyense . However, the morphologically indistinguishable (Group III) Alexandrium tamarense has recently also been found to co-occur, raising important questions in relation to Alexandrium biogeography. To begin to address these, we investigated Alexandrium growth, yield and toxin production in a range of temperature conditions characteristics of present and potential future conditions, using a recently developed flow cytometry method that allowed, for the first time, simultaneous enumeration of the cryptic species in co-culture. Experiments were undertaken in a range of temperatures (12, 15, 18 and 21 °C) in the phosphate (P) limiting conditions that promotes A. fundyense toxicity. Cell/biomass yield was greater for A. tamarense at all temperatures, with observed growth rates varying with temperature. Growth rather and yield were different in mono- and co-culture with the outcome of these interactions also being temperature dependent. For toxic A. fundyense , GTX-3, STX and NEO were the dominant analogues, but total toxicity, toxicity per cell and the number of, and relative proportion of, toxin analogues changed in relation to the onset of P limitation and also as a function of temperature, with the highest toxin concentrations per cell being observed at 12 °C. Toxin concentrations were approximately double in P limited stationary phase compared to exponential growth. Toxin concentrations were lower in the co-cultures, indicating inhibition of production in the presence of non-toxic A. tamarense . The strong performance of A. tamarense is in co-culture at odds with the historical understanding that Scottish waters were dominated by A. fundyense and indicates that changes in water temperatures, and also potentially alleopathic interactions, will influence Alexandrium populations and hence the PSP toxicity threat to humans from shellfish. [ABSTRACT FROM AUTHOR]

Inshore and offshore waters of the Gulf of Maine (USA) have spring/summer harmful algal blooms (HABs) of the toxic dinoflagellate Alexandrium fundyense , which is responsible for paralytic shellfish poisoning (PSP) in humans. The calanoid copepod Calanus finmarchicus co-occurs with A. fundyense during the seasonal blooms. At that time, C. finmarchicus population abundances are high, dominated by immature copepods preparing for diapause, and by actively-reproducing adults. High survival has been reported for copepods exposed to toxic A. fundyense , but little is known about possible sublethal effects. In this study, C. finmarchicus adult females were fed either a control diet of non-toxic Rhodomonas spp. or one of two diets containing either low dose (LD) or high dose (HD) levels (50 and 200 cells mL −1 , respectively) of toxic A. fundyense for a total of 7 days in two independent experiments. As expected, ingestion of the dinoflagellate had no effect on copepod survival and grazing activity. However, significant reductions of egg production and egg viability were observed in C. finmarchicus females fed on either experimental diet . After the 7-day experiment, total nauplius production by females on the LD and HD diets was reduced by 35% to 75% compared to the control females. These results suggest that blooms of A. fundyense in the Gulf of Maine may be an environmental challenge for C. finmarchicus populations, with a potential negative effect on copepod recruitment. [ABSTRACT FROM AUTHOR]

Members of the Amoebophrya ceratii complex are endoparasitic dinoflagellates that parasitize a number of their dinoflagellate relatives, including toxic and/or harmful algal bloom-forming species. Despite many studies on the occurrence, prevalence, biology and molecular phylogeny of Amoebophrya spp., little attention has been given to toxin dynamics of host population following parasitism. Using Amoebophrya sp. infecting the paralytic shellfish toxin (PSP)-producing dinoflagellate Alexandrium fundyense , we addressed the following questions: (1) does parasitism by Amoebophrya sp. alter toxin content and toxin profiles of the dinoflagellate A. fundyense over the infection cycle? and (2) do parasite dinospores produced at the end of the infection cycle retain host toxins and thus potentially act as a vector to convey PSP toxin through the marine microbial food-web? Toxin time-course experiments showed that the PSP toxin contents did not vary significantly over the infection cycle, but mean toxin content for infected cultures was significantly higher than that for uninfected cultures. Host toxins were not detected in the free-living, dinospore stage of the parasite. Therefore, our results indicate that Amoebophrya sp. does not function as a vector for transferring PSP toxins to higher trophic levels. Rather, Amoebophrya infections appear to play an important role in maintaining healthy ecosystems by transforming potent toxins-producing dinoflagellates into non-toxic dinospores, representing “edible food” for consumers of the marine microbial food-web during toxic algal bloom event. [ABSTRACT FROM AUTHOR]

A highly resolved, 3D model of hydrodynamics and Alexandrium fundyense in an estuarine embayment has been developed to investigate the physical and biological controls on a recurrent harmful algal bloom. Nauset estuary on Cape Cod (MA, USA) consists of three salt ponds connected to the ocean through a shallow marsh and network of tidal channels. The model is evaluated using quantitative skill metrics against observations of physical and biological conditions during three spring blooms. The A. fundyense model is based on prior model applications for the nearby Gulf of Maine, but notable modifications were made to be consistent with the Nauset observations. The dominant factors controlling the A. fundyense bloom in Nauset were the water temperature, which regulates organism growth rates, and the efficient retention of cells due to bathymetric constraints, stratification, and cell behavior (diel vertical migration). Spring-neap variability in exchange altered residence times, but for cell retention to be substantially longer than the cell doubling time, it required both active vertical migration and stratification that inhibited mixing of cells into the surface layer by wind and tidal currents. Unlike in the Gulf of Maine, the model results were relatively insensitive to cyst distributions or germination rates. Instead, in Nauset, high apparent rates of vegetative cell division by retained populations dictated bloom development. Cyst germination occurred earlier in the year than in the Gulf of Maine, suggesting that Nauset cysts have different controls on germination timing. The model results were relatively insensitive to nutrient concentrations, due to eutrophic conditions in the highly impacted estuary or due to limitations in the spatial and temporal resolution of nutrient sampling. Cell loss rates were inferred to be extremely low during the growth phase of the bloom but increased rapidly during the final phase due to processes that remain uncertain. The validated model allows a quantitative assessment of the factors that contribute to the development of a recurrent harmful algal bloom and provides a framework for assessing similarly impacted coastal systems. [ABSTRACT FROM AUTHOR]

Embayments and salt ponds along the coast of Massachusetts can host localized blooms of the toxic dinoflagellate Alexandrium fundyense . One such system, exhibiting a long history of toxicity and annual closures of shellfish beds, is the Nauset Marsh System (NMS) on Cape Cod. In order to measure net growth rates of natural A. fundyense populations in the NMS during spring 2012, incubation experiments were conducted on seawater samples from two salt ponds within the NMS (Salt Pond and Mill Pond). Seawater samples containing natural populations of grazers and A. fundyense were incubated at ambient temperatures. Concentrations of A. fundyense after incubations were compared to initial abundances to determine net increases from population growth, or decreases presumed to be primarily due to grazing losses. Abundances of both microzooplankton (ciliates, rotifers, copepod nauplii and heterotrophic dinoflagellates) and mesozooplankton (copepodites and adult copepods, marine cladocerans, and meroplankton) grazers were also determined. This study documented net growth rates that were highly variable throughout the bloom, calculated from weekly bloom cell counts from the start of sampling to bloom peak in both ponds (Mill Pond range = 0.12–0.46 d −1 ; Salt Pond range = −0.02 to 0.44 d −1 ). Microzooplankton grazers that were observed with ingested A. fundyense cells included polychaete larvae, rotifers, tintinnids, and heterotrophic dinoflagellates of the genera Polykrikos and Gymnodinium . Significant A. fundyense net growth was observed in two incubation experiments, and only a single experiment exhibited significant population losses. For the majority of experiments, due to high variability in data, net changes in A. fundyense abundance were not significant after the 24-h incubations. However, experimental net growth rates through bloom peak were not statistically distinguishable from estimated long-term average net growth rates of natural populations in each pond (Mill Pond = 0.27 d −1 and Salt Pond = 0.20 d −1 ), which led to peak bloom concentrations on the order of 10 6 cells l −1 in both ponds. Experimental net growth rates from the incubations underestimated the observed natural net growth rates at several time intervals prior to bloom peak, which may indicate that natural populations experienced additional sources of vegetative cells or periods of reduced losses that the 24-h incubation experiments did not capture, or that the experimental procedure introduced containment artifacts. [ABSTRACT FROM AUTHOR]

Effects of experimental exposure to Alexandrium fundyense , a Paralytic Shellfish Toxin (PST) producer known to affect bivalve physiological condition, upon eastern oysters, Crassostrea virginica with a variable natural infestation of the digenetic trematode Bucephalus sp. were determined. After a three-week exposure to cultured A. fundyense or to a control algal treatment with a non-toxic dinoflagellate, adult oysters were assessed for a suite of variables: histopathological condition, hematological variables (total and differential hemocyte counts, morphology), hemocyte functions (Reactive Oxygen Species (ROS) production and mitochondrial membrane potential), and expression in gills of genes involved in immune responses and cellular protection (MnSOD, CAT, GPX, MT-IV, galectin CvGal) or suspected to be (Dominin, Segon). By comparing individual oysters infested heavily with Bucephalus sp. and uninfested individuals, we found altered gonad and digestive gland tissue and an inflammatory response (increased hemocyte concentration in circulating hemolymph and hemocyte infiltrations in tissues) associated with trematode infestation. Exposure to A. fundyense led to a higher weighted prevalence of infection by the protozoan parasite Perkinsus marinus , responsible for Dermo disease. Additionally, exposure to A. fundyense in trematode-infested oysters was associated with the highest prevalence of P. marinus infection. These observations suggest that the development of P. marinus infection was advanced by A. fundyense exposure, and that, in trematode-infested oysters, P. marinus risk of infection was higher when exposed to A. fundyense . These effects were associated with suppression of the inflammatory response to trematode infestation by A. fundyense exposure. Additionally, the combination of trematode infestation and A. fundyense exposure caused degeneration of adductor muscle fibers, suggesting alteration of valve movements and catch state, which could increase susceptibility to predation. Altogether, these results suggest that exposure of trematode-infested oysters to A. fundyense can lead to overall physiological weakness that decrease oyster defense mechanisms. [ABSTRACT FROM AUTHOR]

The globally increasing trend of harmful algal blooms (HAB) is often attributed to coastal eutrophication and climate change, but the physiological processes at play during a bloom are poorly understood due to lack of in situ measurements of these processes or their corresponding molecular machinery. Here we employed a dinoflagellate spliced leader-based 454-pyrosequencing technique to generate time-serial expressed sequence tags (EST) throughout a diel cycle during an Alexandrium fundyense bloom in Long Island Sound. Assembly of the reads yielded 87,273 dinoflagellate genes. To facilitate mapping of these data to species and comparing of gene expression dynamics between natural bloom and laboratory culture conditions, similar diel EST sets were sequenced for A. fundyense strain CCMP1719, which achieved 31,451 genes. The assembled metatranscriptome reveals a metabolically active A. fundyense population. Relative to the laboratory culture, the natural bloom expressed more abundantly genes related to nitrogen (N)-scavenging, CO 2 -concentrating and saxitoxin production. Most strikingly, the data showed a versatility to exploit various sources of N (cyanate, urea, nitrate/nitrite, and ammonium), likely conferring competitive advantages in A. fundyense for bloom formation or maintenance. The dataset also led to the first characterization of Ni-containing superoxide dismutases (NiSODs) in dinoflagellates with mitochondrial targeting signal identified, which along with other types of SOD found indicated diverse SODs being expressed in the A. fundyense bloom. Our results also demonstrate that metatranscriptomics is an effective approach to unraveling physiological processes conducive to HAB outbreaks. [ABSTRACT FROM AUTHOR]

The Alexandrium tamarense species complex is one of the most studied marine dinoflagellate groups due to its ecological, toxicological and economic importance. Several members of this complex produce saxitoxin and its congeners - potent neurotoxins that cause paralytic shellfish poisoning. Isolates from this complex are assigned to A. tamarense , A. fundyense , or A. catenella based on two main morphological characters: the ability to form chains and the presence/absence of a ventral pore between Plates 1′ and 4′. However, studies have shown that these characters are not consistent and/or distinctive. Further, phylogenies based on multiple regions in the rDNA operon indicate that the sequences from morphologically indistinguishable isolates partition into five clades. These clades were initially named based on their presumed geographic distribution, but recently were renamed as Groups I-V following the discovery of sympatry among some groups. In this study we present data on morphology, ITS/5.8S genetic distances, ITS2 compensatory base changes, mating incompatibilities, toxicity, the sxtA toxin synthesis gene, and rDNA phylogenies. All results were consistent with each group representing a distinct cryptic species. Accordingly, the groups were assigned species names as follows: Group I, A. fundyense; Group II, A. mediterraneum; Group III, A. tamarense ; Group IV, A. pacificum; Group V, A. australiense . [ABSTRACT FROM AUTHOR]

Abstract: Development of forecasting systems for harmful algal blooms (HABs) has been a long-standing research and management goal. Significant progress has been made in the Gulf of Maine, where seasonal bloom forecasts are now being issued annually using Alexandrium fundyense cyst abundance maps and a population dynamics model developed for that organism. Thus far, these forecasts have used terms such as “significant”, “moderately large” or “moderate” to convey the extent of forecasted paralytic shellfish poisoning (PSP) outbreaks. In this study, historical shellfish harvesting closure data along the coast of the Gulf of Maine were used to derive a series of bloom severity levels that are analogous to those used to define major storms like hurricanes or tornados. Thirty-four years of PSP-related shellfish closure data for Maine, Massachusetts and New Hampshire were collected and mapped to depict the extent of coastline closure in each year. Due to fractal considerations, different methods were explored for measuring length of coastline closed. Ultimately, a simple procedure was developed using arbitrary straight-line segments to represent specific sections of the coastline. This method was consistently applied to each year’s PSP toxicity closure map to calculate the total length of coastline closed. Maps were then clustered together statistically to yield distinct groups of years with similar characteristics. A series of categories or levels was defined (“Level 1: Limited”, “Level 2: Moderate”, and “Level 3: Extensive”) each with an associated range of expected coastline closed, which can now be used instead of vague descriptors in future forecasts. This will provide scientifically consistent and simply defined information to the public as well as resource managers who make decisions on the basis of the forecasts. [Copyright &y& Elsevier]

Abstract: A major goal in harmful algal bloom (HAB) research has been to identify mechanisms underlying interannual variability in bloom magnitude and impact. Here the focus is on variability in Alexandrium fundyense blooms and paralytic shellfish poisoning (PSP) toxicity in Maine, USA, over 34 years (1978–2011). The Maine coastline was divided into two regions – eastern and western Maine, and within those two regions, three measures of PSP toxicity (the percent of stations showing detectable toxicity over the year, the cumulative amount of toxicity per station measured in all shellfish (mussel) samples during that year, and the duration of measurable toxicity) were examined for each year in the time series. These metrics were combined into a simple HAB Index that provides a single measure of annual toxin severity across each region. The three toxin metrics, as well as the HAB Index that integrates them, reveal significant variability in overall toxicity between individual years as well as long-term, decadal patterns or regimes. Based on different conceptual models of the system, we considered three trend formulations to characterize the long-term patterns in the Index – a three-phase (mean-shift) model, a linear two-phase model, and a pulse-decline model. The first represents a “regime shift” or multiple equilibria formulation as might occur with alternating periods of sustained high and low cyst abundance or favorable and unfavorable growth conditions, the second depicts a scenario of more gradual transitions in cyst abundance or growth conditions of vegetative cells, and the third characterizes a ”sawtooth” pattern in which upward shifts in toxicity are associated with major cyst recruitment events, followed by a gradual but continuous decline until the next pulse. The fitted models were compared using both residual sum of squares and Akaike's Information Criterion. There were some differences between model fits, but none consistently gave a better fit than the others. This statistical underpinning can guide efforts to identify physical and/or biological mechanisms underlying the patterns revealed by the HAB Index. Although A. fundyense cyst survey data (limited to 9 years) do not span the entire interval of the shellfish toxicity records, this analysis leads us to hypothesize that major changes in the abundance of A. fundyense cysts may be a primary factor contributing to the decadal trends in shellfish toxicity in this region. The HAB Index approach taken here is simple but represents a novel and potentially useful tool for resource managers in many areas of the world subject to toxic HABs. [Copyright &y& Elsevier]

Abstract: We report here the results of ten oceanographic survey cruises carried out in the Gulf of Maine–Georges Bank region of the Northwest Atlantic during the late spring to summer period in 2007, 2008 and 2010, for which we examine and characterize relationships among dissolved inorganic nutrient fields, water mass dynamics and cell densities of the toxic dinoflagellate Alexandrium fundyense. Nutrients are supplied to continental shelf waters of the Gulf of Maine–Georges Bank region by inflows of deep offshore water masses; once in the Gulf they are transported with the residual circulation and mix with surface waters, both in the Gulf and on the Bank. Those fluxes of offshore water masses and their nutrient loads are the major source of nutrients for phytoplankton production in the region, including annual blooms of A. fundyense in the Gulf and on Georges Bank. This much is already known. We suggest here that the locations and magnitude of A. fundyense blooms are controlled in part by variable nutrient fluxes to the interior Gulf of Maine from offshore, and, those interior Gulf of Maine waters are, in turn, the main nutrient source to Georges Bank, which are brought onto the Bank by tidal pumping on the Northern Flank. We present evidence that nitrate is the initial form of nitrogenous nutrient for A. fundyense blooms, but it is quickly depleted to limiting concentrations of less than 0.5µM, at which time continued growth and maintenance of the population is likely fueled by recycled ammonium. We also show that phosphate may be the limiting nutrient over much of Georges Bank in summer, allowing recycled ammonium concentrations to increase. Our temperature–salinity analyses reveal spatial and temporal (seasonal and interannual) variability in the relative proportions of two deep source waters that enter the Gulf of Maine at depth through the Northeast Channel: Warm Slope Water (WSW) and Labrador Slope Water (LSW). Those two source waters are known to vary in their nutrient loads, with nitrate concentrations about 50% higher in WSW than LSW, for example, and as such the proportions of these two water masses to one another are important determinants of the overall nutrient loads in the interior Gulf. In addition to these deep slope water fluxes, we show evidence here of episodic fluxes of relatively fresh and low-nutrient shelf waters from the Nova Scotian Shelf, which enter the Gulf in pulses at depths between the surface and approximately 150m, displacing deep slope waters, and consequently they significantly dilute the Gulf's interior waters, reducing nutrient concentrations and, in turn, affect the magnitude of A. fundyense blooms. [Copyright &y& Elsevier]

Abstract: Measurements of the DNA content of different protist populations can shed light on a variety of processes, including cell division, sex, prey ingestion, and parasite invasion. Here, we modified an Imaging FlowCytobot (IFCB), a custom-built flow cytometer that records images of microplankton, to measure the DNA content of large dinoflagellates and other high-DNA content species. The IFCB was also configured to measure fluorescence from Cy3-labeled rRNA probes, aiding the identification of Alexandrium fundyense (syn. A. tamarense Group I), a photosynthetic dinoflagellate that causes paralytic shellfish poisoning (PSP). The modified IFCB was used to analyze samples from the development, peak and termination phases of an inshore A. fundyense bloom (Salt Pond, Eastham, MA, USA), and from a rare A. fundyense ‘red tide’ that occurred in the western Gulf of Maine, offshore of Portsmouth, NH (USA). Diploid or G2 phase (‘2C’) A. fundyense cells were frequently enriched at the near-surface, suggesting an important role for aggregation at the air-sea interface during sexual events. Also, our analysis showed that large proportions of A. fundyense cells in both the Salt Pond and red tide blooms were planozygotes during bloom decline, highlighting the importance of sexual fusion to bloom termination. At Salt Pond, bloom decline also coincided with a dramatic rise in infections by the parasite genus Amoebophrya. The samples that were most heavily infected contained many large cells with higher DNA-associated fluorescence than 2C vegetative cells, but these cells' nuclei were also frequently consumed by Amoebophrya trophonts. Neither large cell size nor increased DNA-associated fluorescence could be replicated by infecting an A. fundyense culture of vegetative cells. Therefore, we attribute these characteristics of the large Salt Pond cells to planozygote maturation rather than Amoebophrya infection, though an interaction between infection and planozygote maturation may also have contributed. The modified IFCB is a valuable tool for exploring the conditions that promote sexual transitions by dinoflagellate blooms but care is needed when interpreting results from samples in which parasitism is prevalent. [Copyright &y& Elsevier]

Abstract: Like many other dinoflagellate species, Alexandrium fundyense possesses a benthic resting cyst which enables long-term persistence and annual blooms of this species in the Gulf of Maine. The size and extent of these harmful algal blooms are associated with high cyst concentrations in the top 1cm of sediment. Despite the importance of this resting stage in the life history of A. fundyense, little work has been done on bioturbation of cysts in the deep-water cyst beds of the western Gulf of Maine. Our work intensively examined one site within a major regional “seedbed” from February 2003 until August 2005, a time span that included an extraordinarily large bloom of A. fundyense in 2005. Over the course of 2 years we collected samples for benthic infauna and cyst profiles down to a depth of 30cm. We also measured sediment porosity, organic carbon, 210Pb, and porewater dissolved oxygen. On several dates we measured depth profiles of cyst autofluorescence. Profiles of cysts revealed large subsurface maxima peaking between 10 and 15cm depth with cyst concentrations declining strongly toward the sediment surface. On one sampling date (August 2004) we observed a cyst concentration peak at the sediment surface. Using these data we constructed a mechanistic model of cyst bioturbation, mortality, germination, and deposition. Modeled bioturbation was calibrated using 210Pb and modeled cyst profiles were compared to measured profiles. Model runs with constant and interannually-varying rates of cyst deposition produced similar time-averaged cyst profiles. Results indicate that the deeper portions of cyst profiles are determined primarily by bioturbation, germination and cyst mortality and less so by interannual variation in cyst depositional history. This is due to the relatively low sedimentation rate at the study site compared to the rate of bioturbation, and the fact that the number of cysts deposited each year tends to be a small fraction of the total inventory. Seasonal and interannual variation in cyst deposition strongly influenced concentrations of cysts in the top few millimeters of the sediment, however. When cyst deposition rates are low, bioturbation and germination are sufficient to rapidly deplete cysts in this surface layer, leaving relatively few cysts within the sediment depth range that allows germination. But, bioturbation is not rapid enough to homogenize surface sediments within one year. As a result, cyst deposition results in a concentration peak at the sediment surface that persists to fuel germination the following year. Because of this phenomenon, the model predicted that years with high rates of germination follow years with large levels of cyst deposition. Over longer time scales, bioturbation transports cysts from the sediment surface to depth, which, along with germination, creates a persistent subsurface maximum in cyst concentration. Bioturbation also serves to maintain persistence of A. fundyense by transporting older cysts from these deeper layers to the sediment surface where they can germinate. Since high concentrations of cysts near the sediment surface indicate large numbers of cysts deposited during the previous year, if enhanced germination leads to large blooms of A. fundyense, these blooms are predicted to occur in years following large cyst deposition events. [Copyright &y& Elsevier]

Abstract: Both observations and models suggest that large-scale coastal blooms of Alexandrium fundyense in the Gulf of Maine are seeded by deep-bottom cyst accumulation zones (“seed beds”) where cysts germinate from the sediment surface or the overlying near-bottom nepheloid layers at water depths exceeding 100m. The germling cells and their vegetative progeny are assumed to be subject to mortality while in complete darkness, as they swim to illuminated surface waters. To test the validity of this assumption we conducted laboratory investigations of cyst viability and the survival of the germling cells and their vegetative progeny during prolonged exposure to darkness at a temperature of 6°C, simulating the conditions in deep Gulf of Maine waters. We isolated cysts from bottom sediments collected in the Gulf of Maine under low red light and incubated them in 96-well tissue culture-plates in culture medium under a 10:14h light:dark cycle and under complete darkness. Cyst viability was high, with excystment frequency reaching 90% in the illuminated treatment after 30 days and in the dark treatment after 50 days. Average germination rates were 0.062 and 0.038d−1 for light and dark treatments, respectively. The dark treatment showed an approximately 2-week time lag in maximum germination rates compared to the light treatment. Survival of germlings was considerably lower in the dark treatment. In the light treatments, 47% of germinated cysts produced germlings that were able to survive for 7 days and produce vegetative progeny, i.e., there were live cells in the well along with an empty cyst at least once during the experiment. In the dark treatments 12% of the cysts produced germlings that were able to survive for the same length of time. When dark treatments are scaled to take into account non-darkness related mortality, approximately 28% of the cysts produced germlings that were able to survive for at least 7 days. Even though cysts are able to germinate in darkness, the lack of illumination considerably reduces survival rate of germling cells. In addition to viability of cysts in surface sediments and the near-bottom nepheloid layer, survivability of germling cells and their vegetative progeny at aphotic depths is an important consideration in assessing the quantitative role of deep-coastal cyst seed beds in bloom formation. [Copyright &y& Elsevier]

Abstract: The life cycle of Alexandrium fundyense in the Gulf of Maine includes a dormant cyst stage that spends the winter predominantly in the bottom sediment. Wave-current bottom stress caused by storms and tides induces resuspension of cyst-containing sediment during winter and spring. Resuspended sediment could be transported by water flow to different locations in the Gulf and the redistribution of sediment containing A. fundyense cysts could alter the spatial and temporal manifestation of its spring bloom. The present study evaluates model near-bottom flow during storms, when sediment resuspension and redistribution are most likely to occur, between October and May when A. fundyense cells are predominantly in cyst form. Simulated water column sediment (mud) concentrations from representative locations of the Gulf are used to initialize particle tracking simulations for the period October 2010–May 2011. Particles are tracked in full three-dimensional model solutions including a sinking velocity characteristic of cyst and aggregated mud settling (0.1mms−1). Although most of the material was redeposited near the source areas, small percentages of total resuspended sediment from some locations in the western (~4%) and eastern (2%) Maine shelf and the Bay of Fundy (1%) traveled distances longer than 100km before resettling. The redistribution changed seasonally and was sensitive to the prescribed sinking rate. Estimates of the amount of cysts redistributed with the sediment were small compared to the inventory of cysts in the upper few centimeters of sediment but could potentially have more relevance immediately after deposition. [Copyright &y& Elsevier]

Abstract: Cysts of Alexandrium fundyense, a dinoflagellate that causes toxic algal blooms in the Gulf of Maine, spend the winter as dormant cells in the upper layer of bottom sediment or the bottom nepheloid layer and germinate in spring to initiate new blooms. Erosion measurements were made on sediment cores collected at seven stations in the Gulf of Maine in the autumn of 2011 to explore if resuspension (by waves and currents) could change the distribution of over-wintering cysts from patterns observed in the previous autumn; or if resuspension could contribute cysts to the water column during spring when cysts are viable. The mass of sediment eroded from the core surface at 0.4Pa ranged from 0.05kgm−2 near Grand Manan Island, to 0.35kgm−2 in northern Wilkinson Basin. The depth of sediment eroded ranged from about 0.05mm at a station with sandy sediment at 70m water depth on the western Maine shelf, to about 1.2mm in clayey–silt sediment at 250m water depth in northern Wilkinson Basin. The sediment erodibility measurements were used in a sediment-transport model forced with modeled waves and currents for the period October 1, 2010 to May 31, 2011 to predict resuspension and bed erosion. The simulated spatial distribution and variation of bottom shear stress was controlled by the strength of the semi-diurnal tidal currents, which decrease from east to west along the Maine coast, and oscillatory wave-induced currents, which are strongest in shallow water. Simulations showed occasional sediment resuspension along the central and western Maine coast associated with storms, steady resuspension on the eastern Maine shelf and in the Bay of Fundy associated with tidal currents, no resuspension in northern Wilkinson Basin, and very small resuspension in western Jordan Basin. The sediment response in the model depended primarily on the profile of sediment erodibility, strength and time history of bottom stress, consolidation time scale, and the current in the water column. Based on analysis of wave data from offshore buoys from 1996 to 2012, the number of wave events inducing a bottom shear stress large enough to resuspend sediment at 80m ranged from 0 to 2 in spring (April and May) and 0 to 10 in winter (October through March). Wave-induced resuspension is unlikely in water greater than about 100m deep. The observations and model results suggest that a millimeter or so of sediment and associated cysts may be mobilized in both winter and spring, and that the frequency of resuspension will vary interannually. Depending on cyst concentration in the sediment and the vertical distribution in the water column, these events could result in a concentration in the water column of at least 104 cystsm−3. In some years, resuspension events could episodically introduce cysts into the water column in spring, where germination is likely to be facilitated at the time of bloom formation. An assessment of the quantitative effects of cyst resuspension on bloom dynamics in any particular year requires more detailed investigation. [Copyright &y& Elsevier]

Abstract: Cysts residing in benthic nepheloid layers (BNLs) documented in the Gulf of Maine have been proposed as a possible source of inoculum for annual blooms of a toxic dinoflagellate in the region. Herein we present a spatially extensive data set of the distribution and thickness of benthic nepheloid layers in the Gulf of Maine and the abundance and inventories of suspended Alexandrium fundyense cysts within these near-bottom layers. BNLs are pervasive throughout the gulf and adjacent Bay of Fundy with maximum layer thicknesses of 50–60m observed. Mean BNL thickness is 30m in the eastern gulf and Bay of Fundy, and 20m in the western gulf. Cyst densities in the near-bottom particle resuspension layers varied by three orders of magnitude across the gulf with maxima of 105 cystsm−3. An important interconnection of elevated BNL cyst densities is observed between the Bay of Fundy, the Maine Coastal Current and the south-central region of the gulf. BNL cyst inventories estimated for the eastern and western gulf are each on the order of 1015 cysts, whereas the BNL inventory in the Bay of Fundy is on the order of 1016. Although BNL cyst inventories in the eastern and western gulf are 1–2 orders of magnitude smaller than the abundance of cysts in the upper 1cm of sediment in those regions, BNL and sediment-bound cyst inventories are comparable in the Bay of Fundy. The existence of widespread BNLs containing substantial cyst inventories indicates that these near-bottom layers represent an important source of germinating A. fundyense cysts in the region. [Copyright &y& Elsevier]

Abstract: Sediment and water samples were collected for Alexandrium fundyense spatial and temporal distribution and abundance at more than 120 locations throughout the Bay of Fundy during the summers and winters of 1980–1984. These broad surveys have been repeated at various times through the past 30 years, with more regular sampling since 2004. In addition, A. fundyense abundance has been monitored at several locations within the Bay of Fundy at weekly intervals from April to November and monthly during the remaining months since 1988. Paralytic Shellfish Poisoning (PSP) toxins in shellfish (notably Mya arenaria) have also been monitored at multiple locations in the Bay of Fundy since 1943. The datasets were examined to determine relationships and roles between overwintering resting cysts, bloom initiation, bloom decline, motile cell dispersal and A. fundyense motile populations and resulting shellfish toxicity since 1980. Cysts are widely dispersed throughout the Bay of Fundy in the offshore, inshore and intertidal zones with the largest deposits located in the offshore in silt/clay sediments to the east and north of Grand Manan Island at depths of 60–180m. Results show that there is a constant stable source of cysts in the Bay of Fundy with highest concentrations of cysts (9780cystscm−3) observed in 2010 and highest concentrations of A. fundyense motile cells (18×106 cellsL−1) observed in 1980. Interannual changes in abundance in A. fundyense populations, resting cysts and the temporal trends in M. arenaria toxicity are discussed. Results show that there was no relationship between the abundance of overwintering cysts and the magnitude of A. fundyense blooms. The offshore seed beds appear to be relatively constant in cyst density among most years and serve as an important source for the motile cells that lead to initiation of major blooms and resulting shellfish toxicity throughout the Bay of Fundy. [Copyright &y& Elsevier]

Abstract: Here we document Alexandrium fundyense cyst abundance and distribution patterns over nine years (1997 and 2004–2011) in the coastal waters of the Gulf of Maine (GOM) and identify linkages between those patterns and several metrics of the severity or magnitude of blooms occurring before and after each autumn cyst survey. We also explore the relative utility of two measures of cyst abundance and demonstrate that GOM cyst counts can be normalized to sediment volume, revealing meaningful patterns equivalent to those determined with dry weight normalization. Cyst concentrations were highly variable spatially. Two distinct seedbeds (defined here as accumulation zones with>300cystscm−3) are evident, one in the Bay of Fundy (BOF) and one in mid-coast Maine. Overall, seedbed locations remained relatively constant through time, but their area varied 3–4 fold, and total cyst abundance more than 10 fold among years. A major expansion of the mid-coast Maine seedbed occurred in 2009 following an unusually intense A. fundyense bloom with visible red-water conditions, but that feature disappeared by late 2010. The regional system thus has only two seedbeds with the bathymetry, sediment characteristics, currents, biology, and environmental conditions necessary to persist for decades or longer. Strong positive correlations were confirmed between the abundance of cysts in both the 0–1 and the 0–3cm layers of sediments in autumn and geographic measures of the extent of the bloom that occurred the next year (i.e., cysts→blooms), such as the length of coastline closed due to shellfish toxicity or the southernmost latitude of shellfish closures. In general, these metrics of bloom geographic extent did not correlate with the number of cysts in sediments following the blooms (blooms→cysts). There are, however, significant positive correlations between 0–3cm cyst abundances and metrics of the preceding bloom that are indicative of bloom intensity or vegetative cell abundance (e.g., cumulative shellfish toxicity, duration of detectable toxicity in shellfish, and bloom termination date). These data suggest that it may be possible to use cyst abundance to empirically forecast the geographic extent of the forthcoming bloom and, conversely, to use other metrics from bloom and toxicity events to forecast the size of the subsequent cyst population as the inoculum for the next year's bloom. This is an important step towards understanding the excystment/encystment cycle in A. fundyense bloom dynamics while also augmenting our predictive capability for this HAB-forming species in the GOM. [Copyright &y& Elsevier]

Highlights: [•] Alexandrium tamarense and Alexandrium fundyense from Narragansett Bay, RI, USA are identified via thecal plate morphology and molecular analysis. [•] A suite of toxins (C1/2, B1 (GTX-5), STX, GTX-2/3. Neo, and GTX-1/4) are identified in both A. tamarense (6.31fmolcell−1 STX equivalent) and A. fundyense (9.56fmolcell−1 STX equivalent) isolated from Narragansett Bay. [•] First report of regular appearance of the A. fundyense/A. tamarense species complex in Narragansett Bay. [Copyright &y& Elsevier]

Abstract: Different life stages of Alexandrium fundyense have different swimming behavior; gametes often are said to “swarm” or “dance” before mating. This behavior was studied, and quantitative measures of these motility patterns in two-dimensions were generated using motion-analysis software applied to video records of individual-cell movements. Behavior, swimming patterns, and growth were studied in two strains of A. fundyense and compared in encystment medium and growth medium. Vegetative cells swam straight, rotating around the apical axis until they hit something and then swam straight in a different direction. Gamete swimming behavior was slower and characterized by frequent direction changes and circular motion. Gametes contacted other cells frequently (>5cellcontactsmin−1 cell−1). Zygotes swam slowly when newly formed and later became nearly immobile; these cells continued to contact other cells and also surfaces. The results are in accordance with field observations of long swimming distances for vegetative cells, accumulation in thin layers of gametes, and sinking of developing resting cysts attached to marine snow for zygotes. [Copyright &y& Elsevier]

Abstract: Different life stages of two mating-compatible clones of the paralytic shellfish toxin (PST)-producing dinoflagellate Alexandrium fundyense Balech were separated using a combination of techniques; culturing and sampling methods were used to separate vegetative cells and gametes, and sorting flow cytometry was used to separate zygotes. PST profiles were significantly different between life stages; the two gonyautoxins GTX1 and 2 were present in vegetative and senescent cells, but disappeared from gametes and zygotes. Toxin-profile changes were shown to occur very quickly in both strains when pellicle cyst formation was induced by shaking (four minutes) followed by rinsing on a screen. These pellicle cysts produced from exponentially-growing, vegetative cells lost GTX1 and 2 completely. Rapid toxin epimerization of GTX1 to GTX4 and GTX2 to GTX3 is one possible explanation, although the biological advantage of this remains unclear. Another possible explanation is that during the mating phase of a bloom or when cells are disturbed, GTX1 and GTX2 are released into the surrounding water. It may be advantageous for a dinoflagellate bloom to be surrounded by free toxins in the water. [Copyright &y& Elsevier]

Invasive species have become an increasingly greater concern for the ecological health of coastal ecosystems, yet vectors of these introductions often are unclear. This project evaluated the potential for the brown seaweed Ascophyllum nodosum ecad scorpiodes (Hauck) Reinke, packaged with bait worms ( Nereis virens) harvested from the coast of Maine (USA), as a vector of invasive marine fauna and flora. Often, the seaweed and contents of the bait boxes are discarded into the water by recreational fishermen after using the bait worms, and any included non-native species may then be introduced. Bait boxes were purchased from several commercial vendors in Connecticut and New York over a two-year period. Subsamples of the seaweed were placed in laboratory culture and the growth of associated macro- and microalgae was monitored. Marine invertebrate species present in the samples were also identified and quantified. Results indicated 13 species of macroalgae and 23 species of invertebrates were associated with baitboxes. Among the highly diverse microbial assemblage detected, two species of potentially toxic marine microalgae, Alexandrium fundyense Balech and Pseudonitzschia multiseries (Hasle) Hasle, were found both prior to and after incubation at various temperatures, indicating these harmful algae are brought to and can survive in receiving waters. These findings highlight the need to consider alternative choices of bait box packaging materials or appropriate disposal methods of the seaweed in order to minimize the transport of species which are not native to the receiving coastal waters. [ABSTRACT FROM AUTHOR]

Abstract: Paralytic Shellfish Poisoning (PSP) toxins are annually recurrent along the Massachusetts coastline (USA), which includes many small embayments and salt ponds. Among these is the Nauset Marsh System (NMS), which has a long history of PSP toxicity. Little is known, however, about the bloom dynamics of the causative organism Alexandrium fundyense within that economically and socially important system. The overall goal of this work was to characterize the distribution and dynamics of A. fundyense blooms within the NMS and adjacent coastal waters by documenting the distribution and abundance of resting cysts and vegetative cells. Cysts were found predominantly in three drowned kettle holes or salt ponds at the distal ends of the NMS – Salt Pond, Mill Pond, and Town Cove. The central region of the NMS had a much lower concentration of cysts. Two types of A. fundyense blooms were observed. One originated entirely within the estuary, seeded by cysts in the three seedbeds. These blooms developed independently of each other and of the A. fundyense population observed in adjacent coastal waters outside the NMS. The temporal development of the blooms was different in the three salt ponds, with initiation differing by as much as 30 days. These differences do not appear to reflect the initial cyst abundances in these locations, and may simply result from higher cell retention and higher nutrient concentrations in Mill Pond, the first site to bloom. Germination of cysts accounted for a small percentage of the peak cell densities in the ponds, so population size was influenced more by the factors affecting growth than by cyst abundance. Subsurface cell aggregation (surface avoidance) limited advection of the vegetative A. fundyense cells out of the salt ponds through the shallow inlet channels. Thus, the upper reaches of the NMS are at the greatest risk for PSP since the highest cyst abundances and cell concentrations were found there. After these localized blooms in the salt ponds peaked and declined, a second, late season bloom occurred within the central portions of the NMS. The timing of this second bloom relative to those within the salt ponds and the coastal circulation patterns at that time strongly suggest that those cells originated from a regional A. fundyense bloom in the Gulf of Maine, delivered to the central marsh from coastal waters outside the NMS through Nauset Inlet. These results will guide policy decisions about water quality as well as shellfish monitoring and utilization within the NMS and highlight the potential for “surgical” closures of shellfish during PSP events, leaving some areas open for harvesting while others are closed. [Copyright &y& Elsevier]

Abstract: Observations and numerical modeling indicate that a mesoscale anti-cyclonic eddy formed south of Cape Ann at the northern entrance of Massachusetts Bay (MB) during May 2005, when large river discharges in the western Gulf of Maine and two strong Nor''easters passing through the regions led to an unprecedented toxic Alexandrium fundyense bloom (red tide). Both model results and field measurements suggest that the western Maine Coastal Current separated from Cape Ann around May 7–8, and the eddy formed on around May 10. The eddy was trapped at the formation location for about a week before detaching from the coastline and moving slowly southward on May 17. Both model results and theoretical analysis suggest that the separation of the coastal current from the coast and subsequent eddy formation were initiated at the subsurface by an adverse pressure gradient between Cape Ann and MB due to the higher sea level set up by onshore Ekman transport and higher density in downstream MB. After the formation, the eddy was maintained by the input of vorticity transported by the coastal current from the north, and local vorticity generation around the cape by the horizontal gradients of wind-driven currents, bottom stress, and water density induced by the Merrimack River plume. Observations and model results indicate that the anti-cyclonic eddy significantly changed the pathway of nutrient and biota transport into the coastal areas and enhanced phytoplankton including Alexandrium abundances around the perimeter of the eddy and in the western coast of MB. [Copyright &y& Elsevier]

Abstract: Nutritional insufficiency and toxicity are deleterious effects of phytoplankton on grazers. We hypothesize that toxic food is likely to have stronger evolutionary selective effects on grazers than nutritionally insufficient food. We explore this hypothesis in comparative studies of egg production and egg hatching of the copepod Acartia hudsonica challenged with both a toxic and a nutritionally insufficient alga. Experiments lasting 6 days, in which mixtures of different proportions of the suspect and a control alga were offered as food to female copepods, showed that the dinoflagellate Alexandrium fundyense, which bears paralytic shellfish toxins, was toxic to A. hudsonica. In contrast, the diatom Phaeodactylum tricornutum was nutritionally insufficient to A. hudsonica. In another set of experiments, the effects of A. fundyense and P. tricornutum, respectively, as sole foods on egg production and egg hatching success of two geographically separated populations (Maine and Connecticut) of the copepod A. hudsonica were examined in common-environment experiments, after being raised under identical conditions for two generations. The location in Maine regularly experiences toxic blooms of Alexandrium sp. whereas the location in Connecticut does not. During a 6-day period, A. fundyense reduced the egg production rates of the Connecticut copepod population, but not of the Maine population. In contrast, the diatom P. tricornutum reduced the egg production of both populations. These results of this study are consistent with the hypothesis of local adaptation to toxic food, but not to nutritionally insufficient food. [Copyright &y& Elsevier]

Abstract: Exposure of exponentially growing cells of a toxigenic dinoflagellate strain, Alexandrium fundyense, to ammonium chloride concentrations comparable to levels of ammonia observed in Bay of Fundy waters induced formation in a few days of large numbers of double-walled, circular cysts (termed forced cysts). The A. fundyense forced cysts were distinctly different from the asexual pellicle cysts, and the sexual resting cysts (hypnocysts) described by . The circular shape of these forced cysts and their relatively rapid formation suggest that they were not products of fusion while their resistance to adverse conditions and, when returned to optimal conditions, their subsequent rapid germination to form viable cultures within 14 days, point to an important long-term survival role in response to rapidly changing nutritional and environmental circumstances as well as in the waxing and waning of local toxic dinoflagellate blooms. The relative ease of producing the forced cysts and their fairly rapid germination suggest that these cysts could be suitable vehicles for investigations of the physiology and biochemistry of encystment and excystment in the species producing them. Chemical analyses of forced cysts harvested from cultures of this A. fundyense strain showed large variabilities in selected storage products: iron ranged from 0.03pg to 17.40pg Fe/cyst corresponding to 0.04–61.25% of the cyst dry weight; nitrogen levels ranged from 109pg to 3183pg/cyst and phosphorus ranged from 0.55pg to 5.70pg/cyst. Total paralytic shellfish poisons for these A. fundyense cysts consisted of the same toxins apparent in the vegetative cells, i.e. C1C2 toxins, GTX 2/3, saxitoxin and neosaxitoxin, and ranged from 4.4fmol to 333fmol/fg cyst dry wt. [Copyright &y& Elsevier]

Abstract: In common-environment experiments, we measured the uptake, accumulation, retention, transformation and depuration of paralytic shellfish toxins (PSTs) of the dinoflagellate Alexandrium fundyense in adult females of two geographically separated populations (Maine and New Jersey, USA) of the copepod Acartia hudsonica. These populations were previously shown to differ in their history of exposure to Alexandrium blooms, and in their degree of adaptation to this dinoflagellate. Toxin accumulation was measured at several times in incubations lasting up to 72h. Toxin depuration was assessed after a 60h incubation of females with toxic A. fundyense and subsequent 60h incubation in a sole diet of the non-toxic green flagellate Tetraselmis sp. As previously observed, the Maine population had significantly higher toxin ingestion rates. By contrast, both toxin accumulation (up to ∼2.5ng STX eq. female−1) and the depuration rate (∼0.73d−1) were not significantly different between populations. Hence, faster depuration is ruled out as a tolerance mechanism in the Maine population. Some toxin transformation during both accumulation and depuration was evident in both populations. However, differential toxin transformation does not appear to be a tolerance mechanism either. In contrast to these results, toxin retention (ratio of accumulation/cumulative ingestion) was significantly lower in the Maine population. The retentions of gonyautoxin 3 (GTX3) and of two of the most potent toxins, neosaxitoxin (NEO) and saxitoxin (STX), were also significantly lower in that population. At steady state, toxin absorption efficiency was estimated to be 6% for the Maine population and 9% for the New Jersey population. These results suggest that lower toxin absorption is a possible tolerance mechanism for the Maine population. The results of the present study also suggest that copepod adaptation to toxic dinoflagellates does not necessarily lead to higher toxin transfer up the food web. [Copyright &y& Elsevier]

Abstract: Phytoplankton blooms in the Bay of Fundy have been implicated in the deaths of farmed Atlantic salmon (Salmo salar). To establish whether or not elevated concentrations of some phytoplankton species can cause harmful effects or mortality, monocultures of three species, Alexandrium fundyense, Ditylum brightwellii, and Chaetoceros socialis were grown in large quantities. Atlantic salmon smolts were exposed to a range of concentrations of each of these cultures for 24h and, when mortality occurred, an LC50 was calculated (cells DEL id="del2" orig="•"; L−1). Eucampia zodiacus was collected by plankton tow and used in bioassays as well. Exposure of Atlantic salmon to D. brightwellii, C. socialis or E. zodiacus at concentrations as high as 1.0×106 cells L−1, 4.0×106 cells L−1 or 9.0×105 cells L−1, respectively resulted in no apparent deleterious effect. These concentrations are equal to or greater than concentrations of these species observed in the field. A. fundyense was the only species of the 4 examined that was shown to be lethal to Atlantic salmon smolts. The 6h LC50 was estimated as 7.24×105 cells L−1 and the 24h LC50 was estimated as 6.14×105 cells L−1 indicating effects occur quickly and longer exposures do not change the LC50 estimates significantly. The LC50 concentrations represent cell counts similar to those observed in the field. The no observable (lethal) effect level for A. fundyense and Atlantic salmon is estimated as approximately 2.0×105 cells L−1 over 6h and 1.0×105 cells L−1 over 24h. Cell counts do not reflect the toxicity of individual cultures but may be valuable for aquaculture site management. Chemical analyses of the cultured A. fundyense cells in this study show a mean concentration of 33pg saxitoxin equivalents ⋅ cell−1. [Copyright &y& Elsevier]

Abstract: Shipboard grazing experiments were conducted in the Gulf of Maine and on Georges Bank during of June 2006 to estimate zooplankton community grazing impact on a natural bloom of the toxic dinoflagellate Alexandrium fundyense. Surface seawater samples containing natural populations of grazers and A. fundyense from 23 stations were incubated at ambient temperatures. Concentrations of A. fundyense after incubations were compared to those at the start of each experiment to determine net increases due to population growth, or decreases presumed to be primarily due to grazing losses. Abundances of both microzooplankton (tintinnids, oligotrich ciliates, rotifers, copepod nauplii and heterotrophic dinoflagellates) and mesozooplankton (copepod nauplii, copepodites and adult copepods, rotifers, marine cladocerans, and meroplankton) grazers in experimental aliquots were also determined. The total zooplankton community had minimal grazing impact on natural populations of A. fundyense at most stations. At 70% of the stations where grazing experiments were performed, there were no significant differences in initial and final concentrations of A. fundyense. This indicated that growth of, and grazing on A. fundyense were in approximate balance. At 2 stations, which had the highest A. fundyense abundances of the cruise (>104 cellsl−1), % of the A. fundyense population grazed per day was significantly negative, indicating that net population growth of A. fundyense exceeded grazing losses. At 5 stations, which had low concentrations of A. fundyense (102–103 cellsl−1), % of the A. fundyense population grazed per day was significantly positive, indicating that losses of A. fundyense due to grazing exceeded net population growth. For stations with significant differences between Initial and Grazed concentrations of A. fundyense, grazing had the greatest impact at lower concentrations of A. fundyense, and grazing impact by the larger mesozooplankton was inversely related to zooplankton abundance. There was no relationship between microzooplankton abundance and grazing impact on A. fundyense. Grazing exceeded growth only where A. fundyense abundance was low, and growth exceeded grazing only where A. fundyense abundance was high. The inverse relationship between grazing impact and A. fundyense abundance implies that grazing may be capable of retarding bloom development at low concentrations typical of the early stages of a bloom, but at higher concentrations once a bloom becomes established, either grazing maintains a balance with A. fundyense growth, or growth exceeds grazing losses at highest concentrations. [Copyright &y& Elsevier]

Abstract: A monitoring program was initiated in May 1987 to study phytoplankton populations in the Bay of Fundy, southwest New Brunswick, eastern Canada. Samples are collected for phytoplankton distribution and abundance at five locations in the Bay of Fundy. Other parameters measured include plant nutrients (ammonia, nitrite, nitrate, phosphate and silicate), Secchi depth, and depth profiles for fluorescence, oxygen, temperature and salinity. Alexandrium fundyense abundance from the 5 sites and between years is compared to physical and chemical properties of seawater using principle component analyses (PCA) to identify factors showing the greatest amount of variance in temporal and spatial distribution patterns. Analysis of A. fundyense abundance over the 19-year period 1987–2005 indicates that cell abundance from one year does not reflect the following year''s phytoplankton concentration, and nitrate values and cell densities appear to have a negative relationship. A further comparison between the 2 years 2004 and 2005 (years with very different intensities of A. fundyense maximum cell concentrations) further supported these findings. Preliminary analyses indicate that many species abundances and intensities appear to be more climate or weather related than nutrient flux related. Examination of relationships between harmful algal bloom (HAB) cell density, nutrients and environmental variables indicates that there is no evidence that HABs are linked to eutrophication processes at the temporal and spatial scales of the study. [Copyright &y& Elsevier]

Abstract: Mussels (Mytilus edulis) were exposed to cultures of the toxic dinoflagellate Alexandrium fundyense or the non-toxic alga Rhodomonas sp. to evaluate the effects of the harmful alga on the mussels and to study recovery after discontinuation of the A. fundyense exposure. Mussels were exposed for 9 days to the different algae and then all were fed Rhodomonas sp. for 6 more days. Samples of hemolymph for hemocyte analyses and tissues for histology were collected before the exposure and periodically during exposure and recovery periods. Mussels filtered and ingested both microalgal cultures, producing fecal pellets containing degraded, partially degraded, and intact cells of both algae. Mussels exposed to A. fundyense had an inflammatory response consisting of degranulation and diapedesis of hemocytes into the alimentary canal and, as the exposure continued, hemocyte migration into the connective tissue between the gonadal follicles. Evidence of lipid peroxidation, similar to the detoxification pathway described for various xenobiotics, was found; insoluble lipofuchsin granules formed (ceroidosis), and hemocytes carried the granules to the alimentary canal, thus eliminating putative dinoflagellate toxins in feces. As the number of circulating hemocytes in A. fundyense-exposed mussels became depleted, mussels were immunocompromised, and pathological changes followed, i.e., increased prevalences of ceroidosis and trematodes after 9 days of exposure. Moreover, the total number of pathological changes increased from the beginning of the exposure until the last day (day 9). After 6 days of the exposure, mussels in one of the three tanks exposed to A. fundyense mass spawned; these mussels showed more severe effects of the toxic algae than non-spawning mussels exposed to A. fundyense. No significant differences were found between the two treatments during the recovery period, indicating rapid homeostatic processes in tissues and circulating hemocytes. [Copyright &y& Elsevier]

Sublethal behavioural effects of exposure to paralytic shellfish toxins (PST; saxitoxin and its derivatives) from the toxic dinoflagellate Alexandrium fundyense were investigated in newly settled winter flounder Pseudopleuronectes americanus, larval sheepshead minnow Cyprinodon variegatus and larval mummichog Fundulus heteroclitus through an A. fundyense–copepod–fish food chain. Consumption of as few as six to 12 toxin-containing copepods was lethal to the fishes. After consuming fewer toxin-containing copepods, all three fish species exhibited sublethal effects from vector-mediated exposure. Prey-capture ability of mummichogs was reduced in larvae that had consumed toxic copepods, Coullana canadensis. After consuming toxic C. canadensis or mixed copepods, mummichog larvae had reduced swimming performance. Swimming activity was also significantly reduced in winter flounder after consuming toxic copepods, including time spent in motion and distance travelled. Prey capture and predator avoidance were reduced in first-feeding sheepshead minnow larvae that had consumed toxic dinoflagellate cells. Adverse effects on prey capture or predator avoidance may reduce larval survival and facilitate the transmission of PST through the food web. This study provides baseline information on sublethal effects of PST exposure on fishes using a novel food-chain approach with zooplankton as vectors. [ABSTRACT FROM AUTHOR]

Abstract: Substantial mortalities of Atlantic salmon (Salmo salar) at two aquaculture sites in Long Island Sound, off Grand Manan Island, Bay of Fundy (BoF) (New Brunswick, Canada) in September 2003, were associated with a bloom of Alexandrium fundyense (>3×105 cellsL−1), a dinoflagellate alga that produces toxins which cause paralytic shellfish poisoning (PSP). Cells of A. fundyense collected from surface waters while fish were dying had total paralytic shellfish (PS) toxin concentrations of 70.6pgSTXequiv. (saxitoxin equivalents)cell−1 and PS toxin profiles rich in carbamate toxins (78.2%). The zooplankton sampled contained PS toxins (63.1pgSTXequiv.g−1 wet wt) and the toxin profile matched that of A. fundyense cells. Mean PS toxin levels were low (<4μgSTXequiv.100g−1 wet wt) in stomach, gill and muscle tissues of moribund salmon, suggesting that PS toxins are very lethal to salmon. The PS toxin concentrations in blue mussels (Mytilus edulis) growing on the salmon cages (37; 526μgSTXequiv.100g−1 wet wt) were the highest recorded to date from this region. Their PS toxin profiles showed enhanced carbamate contents (85.5%) compared with that found in A. fundyense. Blue mussels collected from an adjacent Canadian Food Inspection Agency (CFIA) monitoring site in Grand Manan had PS toxin concentrations of 4214 and 150μgSTXequiv.100g−1 wet wt in late September and December, respectively, well above the regulatory limit (RL), and horse mussels (Modiolus modiolus) collected in late September had PS toxin concentrations of 2357μgSTXequiv.100g−1 wet wt. Detoxification under laboratory conditions suggested that blue mussels may require up to 19 weeks for elimination below RL when they accumulate these high concentrations of PS toxins. This depuration period may be shorter in the field. PS toxin levels above RL were detected in hepatopancreatic tissues of lobster (Homarus americanus), with lower levels (<16μgSTXequiv.100g−1 wet wt) in tail muscle and gills. These results illustrate the movement of PS toxins through the marine food chain following an A. fundyense bloom in the BoF, and support earlier studies suggesting that kills from the region of zooplanktivorous fish, such as herring (Clupea harengus harengus), can be attributed to blooms of A. fundyense. This is the first reported incident of PSP associated with mortalities of caged Atlantic salmon in the BoF. Analyses of muscle tissues and viscera from the affected salmon indicated that any portion would not be a health hazard if consumed. [Copyright &y& Elsevier]

Abstract: A workshop with the aim to compare classical and molecular techniques for phytoplankton enumeration took place at Kristineberg Marine Research Station, Sweden, in August 2005. Seventeen different techniques – nine classical microscopic-based and eight molecular methods – were compared. Alexandrium fundyense was the target organism in four experiments. Experiment 1 was designed to determine the range of cell densities over which the methods were applicable. Experiment 2 tested the species specificity of the methods by adding Alexandrium ostenfeldii, to samples containing A. fundyense. Experiments 3 and 4 tested the ability of the methods to detect the target organism within a natural phytoplankton community. Most of the methods could detect cells at the lowest concentration tested, 100cellsL−1, but the variance was high for methods using small volumes, such as counting chambers and slides. In general, the precision and reproducibility of the investigated methods increased with increased target cell concentration. Particularly molecular methods were exceptions in that their relative standard deviation did not vary with target cell concentration. Only two of the microscopic methods and three of the molecular methods had a significant linear relationship between their cell count estimates and the A. fundyense concentration in experiment 2, where the objective was to discriminate that species from a morphologically similar and genetically closely related species. None of the investigated methods were affected by the addition of a natural plankton community background matrix in experiment 3. The results of this study are discussed in the context of previous intercomparisons and the difficulties in defining the absolute, true target cell concentration. [Copyright &y& Elsevier]

Abstract: In laboratory experiments, oysters (Crassostrea virginica) were fed Alexandrium fundyense (strain CB501) vegetative cells or resting cysts (from strains CB501 and GMT25) produced from laboratory cultures. The toxicity per cyst was 1.7pgSTXequiv/cyst and for vegetative cells 3.9pgSTXequiv/cell. The toxic, resting cysts and vegetative cells were removed from suspension in the experimental containers within about 4h. Oysters fed toxic vegetative cells digested 72% of cells ingested, and 28% survived gut passage by forming temporary cysts. Toxin levels of oysters fed vegetative cells averaged 27μgSTXequiv/100g meat. Resting cysts added to the experimental containers adhered to the walls so that only 40% of the cysts added were available to the oysters during the experiment. Of the cysts that were ingested, approximately 59% were digested, and oysters accumulated toxins (an average of 1.2μgSTXequiv/100g meat), showing that consumption of resting cysts can cause toxicity in oysters. Direct consumption of resting cysts, thus, may explain shellfish toxicity in areas without known blooms, but with toxic resting cysts in the sediment. These results suggest a possible role of toxic cysts in mediating time-lags between surface blooms and appearance of toxicity in benthic grazers, and the possible role of benthic grazers in controlling seed populations, except in anoxic areas, which can serve as cyst “refuges” from grazing mortality. [Copyright &y& Elsevier]

Abstract: We exposed green-lipped mussels Perna viridis and black sea breams Acanthopagrus schlegeli to toxic dinoflagellates Alexandrium fundyense to evaluate the accumulation, distribution, transformation, and elimination of paralytic shellfish toxins (PSTs) in a controlled environmental condition. The mussels were fed A. fundyense for 7 days followed by 3 weeks of depuration, and the fish were fed toxic clams (pre-exposed to the dinoflagellates) for 5 days followed by 2 weeks of depuration. The toxin content and the compartmental distribution of PSTs were monitored throughout the experiments by high-performance liquid chromatography with post-column fluorescence derivatization (HPLC-FLD). This is the first report to assess the biokinetics of PSTs in marine fish under dietary exposure. The hepatopancreas in the mussels and the viscera in the fish accumulated most of the PSTs. Differential elimination of each toxin was observed in the mussels. The C2 toxins were eliminated rapidly in all organs; except in hepatopancreas, the more potent toxins such as GTX4, were eliminated slower during the depuration period. The relative proportions of various PSTs in the mussels changed over time, suggesting toxin-specific uptake and elimination rates, or biotransformation preferences between toxins. In the fish, the ratio of C1/C2 was 3.0 times (p <0.01) higher when compared to the clam tissues, indicating that conversion from C2 to C1 might have occurred when the toxin was transferred from the clams to the fish. In summary, species differences in uptake, distribution and elimination of PSTs were observed between mussels and fish, and this may influence trophic transfer of algal toxins in marine organisms. [Copyright &y& Elsevier]