Dinophysis Acuminata Research Articles

인천항 내, 외에서 식물플랑크톤 위해종의 분포특성

인천항에서 선박평형수 배출수에 기인한 외래종을 고려한 항만환경 관리수준 설정을 위해 식물플랑크톤의 잠재적 위해종 출현 특성과 관련된 환경영향 요인을 2007년 2월부터 2009년 11월까지 인천항 내측 및 외측에서 계절조사를 수행하였다. 조사결과, 한국 주변해역에서 출현한 바 있는 식물플랑크톤 62종이 관찰되었고, 그 중에 적조원인종 13종과 독소생산종 7종의 잠재적 위해종이 관찰되었다. 잠재적 위해종은 여름철과 겨울철에 인천항 외측에서 더 다양하게 출현하였다. 봄과 겨울철에는 적조원인종인 Skeletonema spp., Thalassiosira nordenskioldii, Paralia sulcata가 항만 내측 (평균 72.4%) 및 외측(평균 77.6%)에서 모두 우점 하였고, 수소이온과 부유물질의 농도와 양의 상관관계를 나타냈다(p<0.05). 여름철에는 인천항 내측에서 적조원인종(Skeletonema spp.) 및 독소생산종(Alexandrium catanella, A. tamarense, Dinophysis acuminata, Pseudo-nitzschia spp.)이 혼합 우점 (평균 74.2%) 하였으나, 외측에서는 Skeletonema spp.와 P. sulcata가 우점 (평균 67.2%)하였다. 연구기간 동안 출현한 독소생산종 들은 용존 무기질산염, 규산염, 인산염 및 화학적 산소요구량과 양의 상관관계를 나타냈다(p<0.05). 식물플랑크톤 엽록소-a 농도는 봄과 여름 및 가을철에 인천항 외측에서 각각 평균 <TEX>$3.05{\mu}g/L$</TEX>, <TEX>$1.49{\mu}g/L$</TEX>, <TEX>$5.46{\mu}g/L$</TEX>로 내측보다 3-5배 높은 농도가 높았고, 겨울철에는 내측 (평균 <TEX>$0.94{\mu}g/L$</TEX>) 및 외측 (평균 <TEX>$0.95{\mu}g/L$</TEX>) 간 농도 차이가 없었다. 요약하면, 인천항 외측은 다양한 적조원인종이 우점하며 엽록소-a 농도가 높았으나, 항만 내측은 여름철 독소생산종의 출현 종수가 높게 나타났고, 외측에 비해 엽록소-a 농도가 낮았다. 각 위해종들의 대 발생 가능성은 영양염, 화학적 산소요구량 및 부유물질의 농도와 비례한 것으로 나타나, 항만 내, 외측의 환경특성을 고려한 잠재적 위해종 관리가 요구된다. This study examined the occurring pattern of potential risky species and the related abiotic factors for port-specific environmental management considering the control of ballast water-induced foreign species at Incheon seaport. From a total of 62 species observed during the study, 13 red-tide and 7 toxic phytoplankton, normally occurring species in Korean waters, occurred from the seasonal investigation at the inner and outer sites of the Incheon seaport from 2007 to 2009. The number of potential risky phytoplankton was relatively high at the outer site of the port during summer and winter. Red-tide species, such as Skeletonema spp., Thalassiosira nordenskioldii, and Paralia sulcata, dominated the total standing crops at the inner site (avg. 72.4%) and outer site (avg. 77.6%) in spring and summer, being positively correlated with the concentrations of total suspended solids (TSS) and pH (p<0.05). In summer, the red-tide species (Skeletonema spp.) and toxic species (Alexandrium catenella, A. tamarense, Dinophysis acuminata and Pseudo-nitzschia spp.) co-dominated (avg. 74.2%) at the inner site, while Skeletonema spp. and P. sulcata predominated (avg. 67.2%) at the outer site. During the study periods, the toxic species were significantly and positively correlated with the chemical oxygen demand (COD), dissolved inorganic nitrogen, silicate and phosphate (p < 0.05). The chlorophyll-a (chl-a) concentration of phytoplankton at the outer site ranged from 1.49 to <TEX>$5.46{\mu}g/L$</TEX> on average, which was 3-5 times higher than that at the inner site in spring, summer and autumn, whereas there was no difference in the concentration between inner (avg. <TEX>$0.94{\mu}g/L$</TEX>) and outer (avg. <TEX>$0.95{\mu}g/L$</TEX>) sites in winter. In summary, diverse red-tide species dominated and a relatively high chl-a concentration existed at the outer site, whereas a relatively high number of toxic species and low chl-a concentration was observed at the inner site in summer. The potential risky species can outbreak in association with the concentration of nutrients, COD and TSS, suggesting that distinctive management of potential risky species is needed considering the environmental characteristics of Incheon seaport.

Acuminolide A: Structure and Bioactivity of a New Polyether Macrolide from Dinoflagellate Dinophysis acuminata

Acuminolide A (1), along with pectenotoxin II (PTX-2), dinophysistoxin I (DTX-1), okadaic acid (OA), and 7-epi-PTX-2 seco acid, was isolated from a large-scale cultivation of the dinoflagellate Dinophysis acuminata. The new 33-membered macrolide 1 was characterized by detailed analysis of 2D NMR and MS data. Its relative stereochemistry was elucidated on the basis of ROESY correlations and J-based analysis. In contrast to the other well-known toxins that were isolated, 1 showed no cytotoxicity against four cancer cell lines but caused potent stimulation of actomyosin ATPase activity.

Diversity and plastid types in Dinophysis acuminata complex (Dinophyceae) in Scottish waters

Dinophysis acuminata produces lipophilic shellfish toxins (LSTs) that have economic and ecological impact on marine invertebrates in NE Atlantic where aquaculture farming is prevalent. Identification of D. acuminata can be complex. Cells exhibit a variety of morphotypes that overlap between species making identification using routine light microscopy difficult. These cells are mixotrophic and their population size is influenced by hydrographic conditions and prey populations. Dinophysis cells are able to acquire and temporarily keep prey plastids from a variety of photosynthetic unicellular sources. The Dinophysis community in Scottish waters tend to be dominated by cells with morphologies that appear to be variants of D. acuminata/norvegica complex particularly during late spring/early summer. To determine the identity of these morphotypes, DNA barcoding was performed on 32 single cell isolates from sites around the Scottish coast using the ribosomal internal transcribed spacer 1 (ITS1) and a partial cytochrome oxidase I (COI) fragment on the same single cells. Although the cells exhibited a variety of morphotypes, most were restricted to one cluster containing D. acuminata and three grouped with Dinophysis ovum. This is the first molecular confirmation of the presence of D. ovum in Scottish waters. Two isolates showed considerable divergence – one was unidentifiable from the public databases, whilst the other matched a Dinophysis cf. acuta isolate from Canada. To investigate prey plastids, molecular analysis of these Dinophysis single cells was conducted with a partial fragment of the plastid ribosomal marker (16S). Most cells harboured plastids from the cryptophyte Teleaulax – the most commonly reported plastid type, however one cell harboured a Rhodomonas/Storeatula derived plastid. This finding increases the range and variety of cryptophyte plastids found in Dinophysis and increases the range of prey-types.

First evidence of cell deformation occurrence during a Dinophysis bloom along the shores of the Gulf of Tunis (SW Mediterranean Sea)

Never before observed or cited in Dinophysis studies, deformations in Dinophysis acuminata and Dinophysis sacculus are reported throughout their cellular division phases (cytokinesis, and sulcal list regeneration) in 5 in situ cell cycle studies in the Punic harbors of Carthage (northern Tunisia). Two types of deformation were observed: invaginations in the ventral and dorsal margin and protuberances at the base of the left sulcal list. No virus or bacteria were detected with Syber green stain. In situ division rates (μ) varied among seasons and stations for the same species. D. acuminata exhibited moderate (0.22day−1) to high (0.68day−1) μ rates which were however very low (0.02–0.17day−1) for D. sacculus in autumn and moderate (0.21–0.35day−1) in late spring. In 2009 the seasonal distribution of Dinophysis indicates maximum Dinophysis cf. ovum abundance in March and a high number of D. acuminata in early June, while in 2010 maximum abundance of the same species was found in mid-June.Molecular and genetic studies and staining with specific fluorescent strains should be addressed to hopefully explain these Dinophysis cell deformations during their in situ division.

Diarrheic toxins in field-sampled and cultivated Dinophysis spp. cells from southern Brazil

In southern Brazil, mixotrophic dinoflagellates belonging to the Dinophysis acuminata complex have recently been involved in diarrheic shellfish poisoning episodes through the production of lipophilic toxins such as okadaic acid (OA) and dinophysistoxin-1 (DTX-1). The present investigation used a combination of laboratory cultures and field surveys at three large estuarine systems in that region to examine toxin retention in Dinophysis spp. cells under optimum or growth-limiting conditions. This study represents the first successful culture of a Dinophysis isolate from the Atlantic South America region. Starved D. acuminata complex cells reached 5.6-fold higher cellular OA quotas (up to 18 pg cell−1) than Mesodinium rubrum-fed cultures 20 days after inoculation in the laboratory. Moreover, in field samples, light-limited cells at the bottom of a stratified water column were less abundant, yet 6.6- to 11-fold more toxic (up to 26.4 pg OA and 1.7 pg DTX-1 cell−1) than those located at the illuminated surface. This phenomenon of toxin retention by slow-dividing cells may partially explain the enormous variation in cell toxin quota found within Dinophysis spp. populations from a single location, and it may have serious implications for cell count-based monitoring program in bivalve aquaculture areas. In fact, only low to moderate OA levels were detected in the digestive glands of oysters Crassostrea spp. (up to 17.8 ng g−1) and the guts and livers of filter-feeding fish (44.7 ng g−1) during the present study, despite the relatively high Dinophysis cell densities (up to 19,500 cells L−1) found in the field.

Red tides in Masan Bay, Korea in 2004–2005: II. Daily variations in the abundance of heterotrophic protists and their grazing impact on red-tide organisms

To investigate the role of heterotrophic protists in the dynamics of red tides in Masan Bay, Korea, we measured the abundance of heterotrophic dinoflagellates, ciliates, and heterotrophic nanoflagellates in daily samples collected from June 2004 to May 2005. The abundance of heterotrophic dinoflagellates, tintinnid ciliates, naked ciliates, and heterotrophic nanoflagellates were high when red tides occurred, with maximum biomass of 1916, 1263, 1013, and 141ng Cml−1, respectively. The HTDs Gyrodinium dominans/Gyrodinium moestrupii, Gyrodinium glaucum, Protoperidinium bipes, and Pfiesteria-like dinoflagellates (PLDs) as well as naked ciliates (≤50μm) were present nearly all year and their maximum biomass was 235, 48, 298, 1020, and 1013ng Cml−1, respectively. PLDs were the most abundant taxa during red tides dominated by Akashiwo sanguinea, Heterocapsa rotundata, summer populations of Prorocentrum minimum, Heterosigma akashiwo, Eutreptiella gymnastica, and cryptophytes, while G. dominans/G. moestrupii were most abundant during red tides dominated by Ceratium furca and Dinophysis acuminata. Naked ciliates were most abundant during red tides dominated by Cochlodinium polykrikoides, Prorocentrum triestinum, and winter populations of P. minimum. The maximum calculated grazing coefficients for each dominant heterotrophic protistan grazer on their respective co-occurring red-tide organisms in Masan Bay ranged from 0.0 to 6.8h−1. The results of the present study suggest that populations of certain heterotrophic protistan grazers may have considerable potential grazing impact on populations of red-tide organisms in Masan Bay.

The red-tide ciliate Mesodinium rubrum in Korean coastal waters

Mesodinium rubrum is a cosmopolitan red tide ciliate and also an obligate mixotroph requiring cryptophycean prey to sustain photosynthesis and growth. Bloom formation by M. rubrum has been recorded in Korea since early 1980s. As part of these records, 40 cases of M. rubrum outbreaks in Korean coastal waters during last three decades were archived in Red Tide Monitoring Dataset of the National Fisheries Research and Development Institute of Korea. Distribution and ecology of Korean M. rubrum populations were first reported in an article about the red tide occurrence and species succession in Jinhae Bay (Park et al., 1988). The first ever temperate strain of M. rubrum was established from Gomso Bay, Korea in 2002 (Yih et al., 2004a), which was followed by a series of research on the biological and ecophysiological characteristics of the ciliate strain MR-MAL01 and then by the first successful cultivation of a DSP dinoflagellate, Dinophysis acuminata strain DA-MAL01 in 2006. Here, we summarize occurrence of M. rubrum in Korean coastal waters encompassing from the national wide long-term monitoring program to the spatiotemporally fine-scaled regional studies. In parallel, we review previous ecophysiological researches using Korean M. rubrum cultures and finally added our perspectives on the future directions of M. rubrum research in Korea.

First report of the toxin profile of Dinophysis sacculus Stein from LC–MS analysis of laboratory cultures

Dinophysis sacculus is associated with DSP outbreaks especially in the Mediterranean Sea and is supposed to be mildly toxic based on few toxin results from field samples. First report of LC–MS analysis of D. sacculus cultures from Galicia (NW Spain) showed moderate amounts of OA (7.8 pg cell−1) comparable to those found in Dinophysis acuminata from the same region, PTX2 (13.2 pg cell−1) and trace amounts of DTX1 (0.8 pg OA equiv. cell−1). The contribution of D. sacculus to DSP outbreaks in the Galician Northern Rías should not be underestimated.

Evaluation of Passive Samplers as a Monitoring Tool for Early Warning of Dinophysis Toxins in Shellfish

From June 2006 to January 2007 passive samplers (solid phase adsorbing toxin tracking, SPATT) were tested as a monitoring tool with weekly monitoring of phytoplankton and toxin content (liquid chromatography–mass spectrometry, LC-MS) in picked cells of Dinophysis and plankton concentrates. Successive blooms of Dinophysis acuminata, D. acuta and D. caudata in 2006 caused a long mussel harvesting closure (4.5 months) in the Galician Rías (NW Spain) and a record (up to 9246 ng·g resin-week−1) accumulation of toxins in SPATT discs. Best fit of a toxin accumulation model was between toxin accumulation in SPATT and the product of cell densities by a constant value, for each species of Dinophysis, of toxin content (average) in picked cells. Detection of Dinophysis populations provided earlier warning of oncoming diarrhetic shellfish poisoning (DSP) outbreaks than the SPATT, which at times overestimated the expected toxin levels in shellfish because: (i) SPATT accumulated toxins did not include biotransformation and depuration loss terms and (ii) accumulation of toxins not available to mussels continued for weeks after Dinophysis cells were undetectable and mussels were toxin-free. SPATT may be a valuable environmental monitoring and research tool for toxin dynamics, in particular in areas with no aquaculture, but does not provide a practical gain for early warning of DSP outbreaks.

Are the mitochondrial cox1 and cob genes suitable markers for species of Dinophysis Ehrenberg?

The identification of Dinophysis species with similar morphology but different toxic (Diarrhetic Shellfish Poisoning, DSP) potential is a crucial task in harmful algae monitoring programmes. The taxonomic assignment of Dinophysis species using molecular markers is a difficult task due to extremely low interspecific variability within their nuclear ribosomal genes and intergenic regions. Mitochondrial cox1 gene has been proposed as a better specific marker for Dinophysis species based on its higher resolution for two morphologically related species (Dinophysis acuminata and Dinophysis ovum) of the “Dinophysis acuminata complex”. In this study, the potential of two mitochondrial genes (mt cox1 and cob) to discriminate among six Dinophysis species (field isolates and cultures) associated with DSP events was explored. Neither mt cox1 nor cob genes provided enough resolution for all species of Dinophysis. The cob gene showed very poor resolution and grouped all Dinophysis spp. in a common clade. In contrast, the cox1 phylogeny distinguished 5 clades in the Dinophysiales – the “acuminata complex”, the “caudata group”, “acuta+norvegica” and Phalacromaspp. However, within the “D. acuminata complex” mtcox1 is so far the unique marker that differentiates D. acuminata from other species: isolates of D. ovum and Dinophysis sacculus had almost identical sequences (only four mismatches), but they were well separated from D. acuminata. D. acuminata and Dinophysis skagii (considered a life cycle stage of the former) showed identical cox1 sequences. Probes towards this gene can be useful in Mediterranean and Western Iberia sites where the co-occurrence of close morphotypes of D. acuminata and D. sacculus pose a problem for monitoring analyses. This is the first report on cultures of D. sacculus and its phylogenetic relation with other species of the D. acuminata complex.

Bimodal distribution patterns of motile phytoplankton in relation to physical processes and stratification (Gulf of Finland, Baltic Sea)

The dynamics and vertical distribution patterns of chlorophyll a and motile phytoplankton species in relation to the vertical stratification and its spatial and temporal variations were analyzed on the basis of observational data collected in the Gulf of Finland in July 2010. Bimodal vertical distribution of phytoplankton characterized by a thick maximum in the upper 10m layer and a thin maximum in the deeper part of the thermocline, where the chlorophyll a fluorescence values often exceeded those in the upper layer, was observed in the areas of locally weaker stratification at the mesoscale in the second half of July. We suggest that the observed bimodal distribution pattern was a result of the downward migration of phytoplankton through the thermocline at night and asynchronous upward movement of cells with a migration cycle longer than 24h. The main species found in the sub-surface maxima were the dinoflagellates Heterocapsa triquetra and occasionally Dinophysis acuminata. Biomass of H. triquetra increased in the surface layer concurrently with the appearance of sub-surface biomass maxima under conditions of relatively high horizontal variability of vertical stratification at the mesoscale. It supports our suggestion that the mesoscale dynamics favors successful vertical migration of this species between the surface layer and deep nitrate reserves. Sub-surface maxima of phytoplankton biomass, as well as vertical migration, leading to selective transport of nutrients, have to be taken into account in the regional ecosystem models, both to forecast phytoplankton blooms and describe more precisely the seasonal dynamics of nutrients and phytoplankton primary production in the stratified estuaries.

A Dinoflagellate Amylax triacantha with Plastids of the Cryptophyte Origin: Phylogeny, Feeding Mechanism, and Growth and Grazing Responses

The gonyaulacalean dinoflagellates Amylax spp. were recently found to contain plastids of the cryptophyte origin, more specifically of Teleaulax amphioxeia. However, not only how the dinoflagellates get the plastids of the cryptophyte origin is unknown but also their ecophysiology, including growth and feeding responses as functions of both light and prey concentration, remain unknown. Here, we report the establishment of Amylax triacantha in culture, its feeding mechanism, and its growth rate using the ciliate prey Mesodinium rubrum (= Myrionecta rubra) in light and dark, and growth and grazing responses to prey concentration and light intensity. The strain established in culture in this study was assigned to A. triacantha, based on morphological characteristics (particularly, a prominent apical horn and three antapical spines) and nuclear SSU and LSU rDNA sequences. Amylax triacantha grew well in laboratory culture when supplied with the marine mixotrophic ciliate M. rubrum as prey, reaching densities of over 7.5×10(3) cells/ml. Amylax triacantha captured its prey using a tow filament, and then ingested the whole prey by direct engulfment through the sulcus. The dinoflagellate was able to grow heterotrophically in the dark, but the growth rate was approximately two times lower than in the light. Although mixotrophic growth rates of A. triacantha increased sharply with mean prey concentrations, with maximum growth rate being 0.68/d, phototrophic growth (i.e. growth in the absence of prey) was -0.08/d. The maximum ingestion rate was 2.54ng C/Amylax/d (5.9cells/Amylax/d). Growth rate also increased with increasing light intensity, but the effect was evident only when prey was supplied. Increased growth with increasing light intensity was accompanied by a corresponding increase in ingestion. In mixed cultures of two predators, A. triacantha and Dinophysis acuminata, with M. rubrum as prey, A. triacantha outgrew D. acuminata due to its approximately three times higher growth rate, suggesting that it can outcompete D. acuminata. Our results would help better understand the ecophysiology of dinoflagellates retaining foreign plastids.

The emergence of Dinophysis acuminata blooms and DSP toxins in shellfish in New York waters

The dynamics of Dinophysis acuminata and its associated diarrhetic shellfish poisoning (DSP) toxins, okadaic acid (OA) and dinophysistoxin-1 (DTX1) as well as pectenotoxins (PTXs), were investigated within plankton and shellfish in Northport Bay, NY, USA, over a four year period (2008–2011). Over the course of the study, Dinophysis bloom densities ranged from ~104 to 106cellsL−1 and exceeded 106L−1 in 2011 when levels of total OA, total DTX1, and PTX in the water column were 188, 86, and 2900pgmL−1, respectively, with the majority of the DSP toxins present as esters. These cell densities exceed – by two orders of magnitude – those previously reported within thousands of samples collected from NY waters from 1971 to 1986. The bloom species was positively identified as D. acuminata via scanning electron microscopy and genetic sequencing (cox1 gene). The cox1 gene sequence from the D. acuminata populations in Northport Bay was 100% identical to D. acuminata from Narragansett Bay, RI, USA and formed a strongly supported phylogenetic cluster (posterior probability=1) that included D. acuminata and Dinophysis ovum from systems along the North Atlantic Ocean. Shellfish collected from Northport Bay during the 2011 bloom had DSP toxin levels (1245ngg−1 total OA congeners) far exceeding the USFDA action level (160ngg−1 total OA of shellfish tissue) representing the first such occurrence on the East Coast of the U.S. D. acuminata blooms co-occurred with paralytic shellfish poisoning (PSP) causing blooms of Alexandrium fundyense during late spring each year of the study. D. acuminata cell abundances were significantly correlated with levels of total phytoplankton biomass and Mesodinium spp., suggesting food web interactions may influence the dynamics of these blooms. Given that little is known regarding the combined effects of DSP and PSP toxins on human health and the concurrent accumulation and depuration of these toxins in shellfish, these blooms represent a novel managerial challenge.

The growth season of Dinophysis acuminata in an upwelling system embayment: A conceptual model based on in situ measurements

The distribution and physiological condition of the DSP-toxin producer Dinophysis acuminata, its relation with accompanying microplankton populations and coupling with upwelling events are described based on weekly sampling at a fixed station in Ría de Pontevedra, Galician Rías Baixas, NW Spain between March and December 2007. D. acuminata was detected from 18 June to 01 October. The appearance of D. acuminata in the Ría coincided with an upwelling-relaxation event and a short-lived maximum (up to 27000cellsL−1) of its potential prey, the phototrophic ciliate Mesodinium cf rubrum. An increase in the proportion of vacuolated Dinophysis cells (72%) observed one week later suggests that the bloom was triggered by heterotrophic feeding on a co-occurring peak of Mesodinium coupled with advection of Dinophysis cells into the ría. Elevated frequencies of cells with starch and vacuoles were closely associated with the presence of M. cf rubrum during the entire bloom season. However, peaks in the frequency of vacuolated cells were only recorded on a few occasions, suggesting that D. acuminata is prey-limited most of the time but does not require a constant supply of prey for long term survival. Infection of D. acuminata by the parasite dinoflagellate Amoebophrya sp., a potential loss factor in the population dynamics of dinoflagellate populations, was observed (1–17% prevalence) immediately prior to the decline of the bloom. A conceptual model is presented of the mechanisms by which D. acuminata blooms develop in a ría influenced by upwelling which utilizes a combination of physics (upwelling-promoted shoreward transport of Dinophysis inoculum) and the match–mismatch of predator–prey (Dinophysis and Mesodinium) populations.

항만 환경에서 식물플랑크톤 잠재적 위해종의 분포

Abstract This study aimed to understand relationship between potential risky species and environmental factors at ports in Korea. During the study periods, 25 potential risky species (red tide and toxic species) representing 20 red-tide species, 5 toxic species were observed in the all ports. Skeletonema costatum (red-tide species) was predominated in all study area. This species showed positive correlation with pH, while negative correlation with dissolved oxygen ( p <0.05) at Busan port. Also, this species showed positive correlation with total suspended solids and pH ( p <0.05) at Ulsan port. However, Sk. costatum showed positive correlation with nitrate at Incheon port ( p <0.01). Pseudo-nitzschia spp. producing amnesic shellfish poison (domoic acid) showed positive correlation withnitrate and silicate in all study areas ( p <0.05). Alexandrium spp. (paralytic shellfish poison) and Dinophysis acuminata (diarrhetic shellfish poison) were affected by chemical oxygen demand (

Seasonal variability of Dinophysis spp. and Protoceratium reticulatum associated to lipophilic shellfish toxins in a strongly stratified Chilean fjord

The fine scale vertical distribution of Dinophysis spp. and Protoceratium reticulatum (potential producers of lipophilic shellfish toxins, LSTs) and its relation with LSTs in shellfish was studied in Reloncaví fjord, a strongly stratified system in Southern Chile. Samples were taken over two years from late spring to early autumn (2007–2008 period) and from early spring to late summer (2008–2009 period). Dinophysis spp., in particular Dinophysis acuminata, were always detected, often forming thin layers in the region of the salinity driven pycnocline, with cell maxima for D. acuminata of 28.5×103cellsL−1 in March 2008 and 17.1×103cellsL−1 in November 2008. During the 2008–2009 sampling period, blooms of D. acuminata co-occurred with high densities of cryptophyceans and the ciliate Mesodinium spp. The highest levels of pectenotoxin-2 (PTX-2; 2.2ng L−1) were found in the plankton in February 2009, associated with moderate densities of D. acuminata, Dinophysis tripos and Dinophysis subcircularis (0.1–0.6×103cellsL−1). However, only trace levels of PTX-2 were observed in bivalves at that time. Dinophysistoxin (DTX-1 and DTX-3) levels in bivalves and densities of Dinophysis spp. were not well correlated. Low DTX levels in bivalves observed during a major bloom of D. acuminata in March 2008 suggested that there is a large seasonal intraspecific variability in toxin content of Dinophysis spp. driven by changes in population structure associated with distinct LST toxin profiles in Reloncaví fjord during the study period. A heterogeneous vertical distribution was also observed for P. reticulatum, whose presence was restricted to summer months. A bloom of this species of 2.2×103cellsL−1 at 14m depth in February 2009 was positively correlated with high concentrations of yessotoxins in bivalves (51–496ngg−1) and plankton samples (3.2ngL−1). Our results suggest that a review of monitoring strategies for Dinophysis spp. in strongly stratified fjord systems should be carried out. They also indicate that early warning of LST events based on Dinophysis cell numbers are not reliable for seafood control.

Successful cultivation of the toxic dinoflagellate Dinophysis tripos (Dinophyceae)

Since Park et al. (2006) succeeded in cultivating the toxic dinoflagellate Dinophysis acuminata and maintaining them by feeding them the ciliate Myrionecta rubra grown with a cryptophyte Teleaulax sp., the present study is the fifth report of propagation of a Dinophysis species (Dinophysis tripos) under laboratory conditions and describes the maintenance of clonal strains kept at relatively high abundance (>2,000 cells mL-1) for a relatively long period (>6 months) when fed on M. rubra with the addition of Teleaulax amphioxeia. Dinophysis tripos grew at a growth rate of 0.54 divisions day-1, reaching a maximum concentration of ca. 2,200 cells mL-1 during the first 14-day growth experiment. At the end of the incubations, the total amounts of pectenotoxin-2 and dinophysistoxin-1 in the D. tripos culture reached up to 2,780±216 (mean±SD) and 1.8±3.2 ng mL-1, respectively, therefore, we confirmed active toxin production. However okadaic acid (OA) was not detected from this culture before or after the incubation. These data clearly indicate that D. tripos needs to feed on their ciliate prey to actively produce the toxins.

Molecular probes and microarrays for the detection of toxic algae in the genera Dinophysis and Phalacroma (Dinophyta)

Dinophysis and Phalacroma species containing diarrheic shellfish toxins and pectenotoxins occur in coastal temperate waters all year round and prevent the harvesting of mussels during several months each year in regions in Europe, Chile, Japan, and New Zealand. Toxicity varies among morphologically similar species, and a precise identification is needed for early warning systems. Molecular techniques using ribosomal DNA sequences offer a means to identify and detect precisely the potentially toxic species. We designed molecular probes targeting the 18S rDNA at the family and genus levels for Dinophysis and Phalacroma and at the species level for Dinophysis acuminata, Dinophysis acuta, and Dinophysis norvegica, the most commonly occurring, potentially toxic species of these genera in Western European waters. Dot blot hybridizations with polymerase chain reaction (PCR)-amplified rDNA from 17 microalgae were used to demonstrate probe specificity. The probes were modified along with other published fluorescence in situ hybridization and PCR probes and tested for a microarray platform within the MIDTAL project (http://www.midtal.com). The microarray was applied to field samples from Norway and Spain and compared to microscopic cell counts. These probes may be useful for early warning systems and monitoring and can also be used in population dynamic studies to distinguish species and life cycle stages, such as cysts, and their distribution in time and space.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-012-1403-1) contains supplementary material, which is available to authorized users.

Effects of light and food availability on toxin production, growth and photosynthesis in Dinophysis acuminata

Diarrhetic shellfish poisoning (DSP) toxins constitute a severe health risk to shellfish consumers and a serious economic risk to the shellfish industry. The most prominent producers of DSP toxins are the mixotrophic dinoflagellates Dinophysis spp., which rely on chloroplasts from their prey, the ciliate Mesodinium rubrum; i.e. they are kleptoplastidic. Studies based on field col- lected material have indicated that cellular toxin contents in Dinophysis spp. vary intraspecifically by several orders of magnitude, but the regulating factors of cellular toxin contents are still poorly understood. We isolated 7 strains of D. acuminata, all of which produced pectenotoxin-2 (PTX-2) in the range of 12.7 to 35.6 pg cell �1 when supplied with abundant nutrients, light and food. One strain was selected for detailed studies on the effects of irradiance and food availability on pho- toacclimation, photosynthesis, growth and toxin production. Photoacclimation was detected for the first time in this genus, indicating some genetic control of sequestered chloroplasts. Growth and photosynthesis increased 4-fold with irradiances from 7 to 130 µmol photons m �2 s �1 after a minimum of 2 wk under ample food conditions. Despite this, cellular PTX-2 content increased only slightly from (mean ±SE) 4.6 ± 0.3 to 7.8 ± 1.1 pg PTX-2 cell �1 . Toxin production continued for up to 30 d after food was depleted, leading to a build-up of toxin in D. acuminata cells to 24.7 ± 1.7 pg PTX-2 cell �1 . Thus, we demonstrate that PTX-2 content is not directly coupled to irradiance and that PTX-2 production is not directly associated with ingestion of ciliate prey. Intraspecific varia- tions in toxicity are instead most likely governed primarily by growth phase and genetic differ- ences between different populations of Dinophysis spp.

The risk of harmful algal blooms (HABs) in the oyster-growing estuaries of New South Wales, Australia

The spatial and temporal variability of potentially harmful phytoplankton was examined in the oyster-growing estuaries of New South Wales. Forty-five taxa from 31 estuaries were identified from 2005 to 2009. Harmful species richness was latitudinally graded for rivers, with increasing number of taxa southward. There were significant differences (within an estuary) in harmful species abundance and richness for 11 of 21 estuaries tested. Where differences were observed, these were predominately due to species belonging to the Pseudo-nitzschia delicatissima group, Dinophysis acuminata, Dictyocha octonaria and Prorocentrum cordatum with a consistent upstream versus downstream pattern emerging. Temporal (seasonal or interannual) patterns in harmful phytoplankton within and among estuaries were highly variable. Examination of harmful phytoplankton in relation to recognised estuary disturbance measures revealed species abundance correlated to estuary modification levels and flushing time, with modified, slow flushing estuaries having higher abundance. Harmful species richness correlated with bioregion, estuary modification levels and estuary class, with southern, unmodified lakes demonstrating greater species density. Predicting how these risk taxa and risk zones may change with further estuary disturbance and projected climate warming will require more focused, smaller scale studies aimed at a deeper understanding of species-specific ecology and bloom mechanisms. Coupled with this consideration, there is an imperative for further taxonomic, ecological and toxicological investigations into poorly understood taxa (e.g. Pseudo-nitzschia).