Enzymatic digestive activity and absorption efficiency in Tagelus dombeii upon Alexandrium catenella exposure

We analyzed absorption efficiency (AE) and digestive enzyme activity (amylase, cellulase complex, and laminarinase) of the infaunal bivalve Tagelus dombeii originating from two geographic sites, Corral-Valdivia and Melinka-Aysén, which have different long-term paralytic shellfish poisoning (PSP) exposure rates. We report the effects of past feeding history (origin) on T. dombeii exposed to a mixed diet containing the toxic dinoflagellate Alexandrium catenella and another dinoflagellate-free control diet over a 12-day period in the laboratory. Absorption efficiency values of T. dombeii individuals that experienced PSP exposure in their habitat (Melinka-Aysén) remained unchanged during exposure to toxic food in the laboratory. In contrast, T. dombeii from a non-PSP exposure field site (Corral-Valdivia) showed a significant reduction in AE with toxic exposure time. This study established that the amylase and cellulase complexes were the most important enzymes in the digestive glands of Tagelus from both sites. The temporal evolution of enzymatic activity under toxic diet was fitted to exponential (amylase and cellulase) and to a logarithmic (laminarinase) models. In all fits, we found significant effect of origin in the model parameters. At the beginning of the experiment, higher enzymatic activity was observed for clams from Corral-Valdivia. The amylase activity decreased with time exposure for individuals from Corral and increased for individuals from Melinka. Cellulase activity did not vary over time for clams from Corral, but increased for individuals from Melinka and laminarinase activity decreased over time for individuals from Corral and remained unchanged over time for Melinka. A feeding history of exposure to the dinoflagellate A. catenella was reflected in the digestive responses of both T. dombeii populations.     

Feeding and intoxication–detoxification dynamics in two populations of the mussel Mytilus chilensis (Hupé, 1854) with different histories of exposure to paralytic shellfish poisoning (PSP)

Individuals of Mytilus chilensis with different histories of exposure to paralytic shellfish poisoning (PSP) were exposed to a diet containing the dinoflagellate Alexandrium catenella. Feeding and intoxication–detoxification dynamics were evaluated over a period of 12–16?days. Feeding activity was reduced during the first days of exposure, followed by a period of recovery from day 5 to the end of the experiment. Mussels from Corral population (no history of PSP exposure) exceeded the concentration of 80?μg STX eq. 100?g^?1 tissue, although filtration activity was significantly lower compared with individuals from Melinka (frequent PSP exposure). The higher feeding activity and the lower degree of toxin accumulation in the Melinka population appear be associated with frequent exposure to PSP in the natural environment. The use of A. catenella as food resource and the capacity of a rapid intoxication of both populations showed that M. chilensis is an adequate indicator for early detection of PSP.     

Contrasting Physiological Responses of Two Populations of the Razor Clam Tagelus dombeii with Different Histories of Exposure to Paralytic Shellfish Poisoning (PSP)

This study describes the physiological performance of two populations of the razor clam Tagelus dombeii from two geographic areas with different histories of exposure to paralytic shellfish poisoning (PSP) linked to the toxic dinoflagellate Alexandrium catenella. Clams from Melinka-Aysén, which are frequently exposed to PSP, were not affected by the presence of toxins in the diet. However, clams from Corral-Valdivia, which have never been exposed to PSP, exhibited significantly reduced filtration activity and absorption, affecting the energy allocated to scope for growth (SFG). Ammonia excretion and oxygen uptake were not affected significantly by the presence of A. catenella in the diet. Measurements of energy acquisition and expenditure were performed during a 12-day intoxication period. According to three-way repeated measure ANOVAs, the origin of the clams had a highly significant effect on all physiological variables, and the interaction between diet and origin was significant for the clearance and absorption rates and for the scope for growth. The scope for growth index showed similar positive values for both the toxic and non-toxic individuals from the Melinka-Aysén population. However, it was significantly reduced in individuals from Corral-Valdivia when exposed to the diet containing A. catenella. The absence of differences between the physiological response of the toxic and non-toxic clams from Melinka-Aysén may be related to the frequent presence of A. catenella in the environment, indicating that this bivalve does not suffer negative consequences from PSP. By contrast, A. catenella has a negative effect on the physiological performance, primarily on the energy gained from the environment, on T. dombeii from Corral-Valdivia. This study supports the hypothesis that the history of PSP exposure plays an important role in the physiological performance and fitness of filter feeding bivalves.     

The growth,toxicity and genetic characterization of seven strains of Alexandrium catenella (Whedon and Kofoid) Balech 1985 (Dinophyceae) isolated during the 2009 summer outbreak in southern Chile

The dinoflagellate Alexandrium catenella causes recurrent harmful algal blooms in southern Chile. This species belongs to the “Alexandrium tamarense/catenella/fundyense species complex” (the “tamarensis complex”), defined by morphological attributes. Ribosomal sequences serve to differentiate five evolutionary lineages (clades) in this species complex. These distinctions reflect the geographic distribution and toxicity of the populations rather than their morphological designations. Despite the social and economic impact that harmful blooms produce in Chile, few strains of A. catenella have been isolated. Moreover, physiological and/or genetic studies of the group are scarce. The aim of this work was to examine possible physiological and genetic variability among populations of A. catenella having different geographical origins but isolated from the same toxic event. Seven strains of A. catenella were isolated and established from phytoplankton samples collected in the Aysén and Los Lagos regions of southern Chile during a recent outbreak (February–March 2009). Growth, toxicity, and ITS sequences were compared among these strains. All the strains included in this study were grouped with strains belonging to the previously described “North America” clade. The genetic diversity detected among Chilean strains was 3%, a much higher value than those reported for comparisons among strains from other parts of the world. In addition, a remarkable variability of growth parameters and toxicity was detected among strains. Strain PFB45 showed the highest PSP toxin content, whereas strain PFB41 had the lowest value of this parameter but had the highest maximum cell density. In strains PFB38, PFB42, and PFB37, more than 98% of the total PSP toxin content occurred in the form of gonyautoxins (primarily GTX-4,1 and GTX-3,2). In strains PFB39, PFB36, and PFB45, neoSTX, and STX toxins were detected. These results demonstrated remarkable variability at the genetic and physiological level among strains of A. catenella isolated from the same outbreak. No correlations were found between the phenotypic traits (growth and toxicity) and the genetic affiliation of the strains studied.     

Das Farbkleid von Rhinoderma darwini D. & B., seine Zeichnungsmuster und Variabilität

Se describen a base de 198 ejemplares de Rhinoderma darwini los patrones de colores de tres variedades: unicolor (47%), angulata (49%) y lateralis (4%). Los sapitos son colectados entre Concepción y Aysén, de los cuales la mayoría pertenece a diferentes habitates en la província de Valdivia. Los colores congénitos de la especie son: negro, bianco, café y verde. La tonalidad de los colores de la piel, café y verde, en las partes dorsales y laterales se adaptan de acuerdo al ambiente del animal. Esta adaptación es solamente posible entre un oscurecimiento y aclaramiento del color básico. Es dudoso, si esta adaptación significa una protección efectiva y si Rhinoderma busca un biotopo que corresponda a su patron. Se discute la posibilidad, que Rhinoderma no esté some‐tido a una gran presión selectiva.     

Toxin profile of Alexandrium catenella from the Chilean coast as determined by liquid chromatography with fluorescence detection and liquid chromatography coupled with tandem mass spectrometry

The profile of tetrahydropurine neurotoxins associated with paralytic shellfish poisoning (PSP) was determined from a Chilean strain of the marine dinoflagellate Alexandrium catenella. The toxin composition was compared with that of toxic shellfish, presumably contaminated by natural blooms of A. catenella from the same region in southern Chile. Ion pair-liquid chromatography with post-column derivatization and fluorescence detection (LC-FD) was employed for relative quantitative analysis of the toxin components, whereas unambiguous identification of the toxins was confirmed by tandem mass spectrometry (LC–MS/MS). In the dinoflagellate strain from Chile, the N-sulfocarbamoyl derivatives (C1/C2, B1) and the carbamoyl gonyautoxins GTX1/GTX4 comprise >90% of the total PSP toxin content on a molar basis. This toxin composition is consistent with that determined for A. catenella populations from the Pacific coast in the northern hemisphere. The characteristic toxin profile is also reflected in the shellfish, but with evidence of epimerization and metabolic transformations of C1 and C2 to GTX2 and GTX3, respectively. This work represents the first unequivocal identification and confirmation of such PSP toxin components from the Chilean coast.     

Quantification methods for Alexandrium catenella, a toxic dinoflagellate: Comparison of competitive enzyme-linked immunosorbent assay and sandwich hybridization integrated with a nuclease protection assay

Alexandrium catenella (Whedon et Kofoid) Balech, a toxic dinoflagellate, is a bloom-forming planktonic species in cold water coastal regions. It produces strong paralytic shellfish poisoning (PSP) toxins which are transmitted via tainted shellfish. These toxins can affect humans, other mammals, fish and birds. In this study, polyclonal antiserum against A. catenella was produced, and a competitive enzyme-linked immunosorbent assay (cELISA) was developed to detect A. catenella. The antiserum against A. catenella showed good specificity, the linear detection range was relatively large, between 38 and 600,000 cells. In addition, specific probes were designed to target the small subunit ribosomal RNA (SSU rRNA) of A. catenella, and quantitative sandwich hybridization integrated with a nuclease protection assay (NPA-SH) was established in order to identify and quantify A. catenella. The NPA-SH assay did not show good specificity as well as cELISA, by which A. catenella and A. tamarense could not be distinguished. Samples in different cell growth phases were analyzed with cELISA and NPA-SH. The results showed that the cell concentration calculated by cELISA was very similar with microscopy, while that of NPA-SH was sometimes higher than that of microscopy, especially in log phase. Comparing the two methods, both assays allow rapid identification of A. catenella without time-consuming microscopy when multiple sites need to be considered in routine monitoring. Meanwhile, cELISA was more specific and accurate in detection of A. catenella than NPA-SH.     

Application of real-time PCR assay for detection and quantification of Alexandrium tamarense and Alexandrium catenella cysts from marine sediments

The dinoflagellates Alexandrium tamarense (Lebor) Balech and Alexandrium catenella (Whedon and Kofoid) Balech (Dinophyceae) are believed to be the main species responsible for paralytic shellfish poisoning (PSP) all over the world. It is necessary to identify A. tamarense and A. catenella cysts and to monitor their distribution in sediment in order to minimize the damages caused by PSP to the economy and food quality because cysts are the seed population for blooms caused by motile vegetative cells. In this study, we developed an efficient DNA extraction method from the natural cysts present in marine sediments after they were size fractionated with a plankton net (mesh size of 20–150 μm). The 10–3000 cysts were added to the sediments collected from the Ariake Sea, and for which the primuline-staining method did not reveal any cysts. DNA was then extracted from each sample, and linear standard curves for A. tamarense and A. catenella cysts were obtained from the correlation between the Ct values by real-time PCR and the log of the initial densities of cysts. We monitored the A. tamarense and A. catenella cyst densities in the environmental samples. This assay was demonstrated to be a powerful tool for the identification, detection, and quantification of the cysts of the toxic dinoflagellates.     

Effects of the toxic dinoflagellate Alexandrium catenella on histopathogical and escape responses of the Northern scallop Argopecten purpuratus

Juvenile Northern scallops Argopecten purpuratus were exposed to cultures of the paralytic shellfish toxin (PST) producing dinoflagellate, Alexandrium catenella, or a non-toxic microalga as a control, T-iso. After 3 and 6 days of exposure to either A. catenella or T-iso, scallops were stimulated to elicit an escape response by exposing them to the predatory sea star Meyenaster gelatinosus. We monitored the escape response of the scallops in terms of reaction time after first contact with the sea star, number of claps (burst of rapid valve closures) until exhaustion, clapping time, clapping rate, the time scallops spent closed when exhausted, and recovery from the initial number of claps, clapping time and clapping rate. Additionally, histopathological and stress responses (through heat-shock protein [hsp70] induction), as well as accumulation of Paralytic Shellfish Poisoning (PSP) toxins, were monitored on scallops after 3 and 6 days of exposure to A. catenella. After 6 days of exposure, scallops exposed to A. catenella accumulated PSTs and reacted more rapidly with a higher clapping rate, however the duration of their escape response was shorter than controls, when exposed to M. gelatinosus. Additionally, scallops exposed to A. catenella showed histopathological features, especially after 6 days of exposure, including increased melanization of the tissues and myopathy, with high levels of degeneration of the muscle fibers. A six-day exposure to A. catenella also caused an increase in prevalence of rickettsiales-like organisms within scallop tissues. This study suggests that PST accumulation can affect the interaction between the Northern scallop and both pathogens and predators, potentially increasing their susceptibility to either of them.     

Role of resting cysts in Chilean Alexandrium catenella dinoflagellate blooms revisited

The detection of sparse Alexandrium catenella-resting cysts in sediments of southern Chilean fjords has cast doubts on their importance in the recurrence of massive toxic dinoflagellate blooms in the region. The role of resting cysts and the existence of different regional Chilean populations was studied by culturing and genetic approaches to define: (1) cyst production; (2) dormancy period; (3) excystment success; (4) offspring viability and (5) strain mating compatibility. This study newly revealed a short cyst dormancy (minimum 69 days), the role of key abiotic factors (in decreasing order salinity, irradiance, temperature and nutrients) controlling cyst germination (max. 60%) and germling growth rates (up to 0.36–0.52 div. day⁻¹). Amplified fragment length polymorphism (AFLP) characterization showed significant differences in genetic distances (GD) among A. catenella populations that were primarily determined by the geographical origin of isolates and most likely driven by oceanographic dispersal barriers. A complex heterothallic mating system pointed to variable reproductive compatibility (RCs) among Chilean strains that was high among northern (Los Lagos/North Aysén) and southern populations (Magallanes), but limited among the genetically differentiated central (South Aysén) populations. Field cyst surveys after a massive 2009 bloom event revealed the existence of exceptional high cyst densities in particular areas of the fjords (max. 14.627 cysts cm⁻³), which contrast with low cyst concentrations (<221.3 cysts cm⁻³) detected by previous oceanographic campaigns. In conclusion, the present study suggests that A. catenella resting cysts play a more important role in the success of this species in Chilean fjords than previously thought. Results from in vitro experiments suggest that pelagic–benthic processes can maintain year-round low vegetative cell concentrations in the water column, but also can explain the detection of high cysts aggregations after the 2009-bloom event. Regional drivers that lead to massive outbreaks, however, are still unknown but potential scenarios are discussed.     

A temporal and spatial study of genetic structure in four species of bladed Bangiales (Rhodophyta) from the southeastern Pacific coast of Chile

The coastline is a heterogeneous and highly dynamic environment influenced by abiotic and biotic variables affecting the temporal stability of genetic diversity and structure of marine organisms. The aim of this study was to determine how much the genetic structure of four species of marine Bangiales vary in time and space. Partial sequences of the cytochrome oxidase I (COI) gene obtained from two Pyropia (Py. sp. CHJ and Py. orbicularis) and two Porphyra (P. mumfordii and P. sp. FIH) species were used to compare the effect of the 40° S/41° S biogeographic break (spatial-regional scale) and the one of the Valdivia River discharges (spatial-local scale) and determine their temporal stability. Four seasonal samplings were taken during 1 year at five sites, one site located in Melinka (Magallanes province) and four sites along the coast of Valdivia (Intermediate area), on both sides of the river mouth. Results showed a strong genetic spatial structure at regional scale (ΦST > 0.4) in Py. sp. CHJ, Py. orbicularis, and P. mumfordii, congruent with the 41° S/42° S biogeographic break. A potential barrier to gene flow, related to the Valdivia River discharge, was detected only in P. mumfordii. In P. sp. FIH, spatial genetic structure was not detected at any scale. The genetic structure of all four species is stable throughout the year. The potential effect of main currents and river discharge in limiting the transport of Bangiales spores are discussed. We propose that both a restricted propagule dispersal and the formation potential for persistent banks of microscopic stages could lead to a temporally stable spatial partitioning of genetic variation in bladed Bangiales.     

Giant Cocoon Formation in the Silkworm,Bombyx mori L., Topically Treated with Methyleneclioxyphenyl Derivatives

To analyze the genetic system of paralytic shellfish poisoning (PSP) toxin production in the dinoflagellate Alexandrium catenella, we examined toxin compositions and mating type of Fl progenies from crosses between algal strains having different toxin compositions. In all strains used, the mole percentage of their toxin composition did not significantly change in any growth phase, although total toxin levels increased rapidly in the early to middle exponential growth phase and then decreased by 95% in the stationary phase. One parental strain produced gonyautoxin (GTX) 4, and C4, while the other produced neosaxitoxin (neoSTX) and saxitoxin (STX) during all growth phases. Fl progenies showed one parental toxin composition and segregated independently with the mating type. These data suggest that A. catenella is a toxin producer and that Mendelian inheritance of toxin profiles occurs in the heterothallic dinoflagellate A. catenella.     

A redescription of the large geophilid centipede Chilenophilus corralinus (Attems, 1903) (Myriapoda: Chilopoda: Geophilomorpha), with new distribution records from southern Chile

The little known geophilomorph centipede Chilenophilus corralinus (Attems, 1903) (Myriapoda: Chilopoda, Geophilidae), a large geophilid species from South America is herein redescribed and illustrated based on new specimens collected in the Andes of Southern Chile. New morphological features of specific value are also given for the taxon. Chilenophilus corralinus is reported for the first time from the following Chilean localities: Region XIV (de Los Ríos region): Valdivia province: Pirihueico; camping “La Herradura”; Mafil. Region X (de Los Lagos region): Chiloé province: Chiloé Island. Llanquihue province: Parque Nacional Alerce Andino. Palena province: Hualaihué; Chaitén; Palena; Futaleufú.     

Rapid detection of natural cells of Alexandrium tamarense and A. catenella (Dinophyceae) by fluorescence in situ hybridization

The marine toxic dinoflagellates Alexandrium tamarense (Lebor) Balech and A. catenella (Whedon and Kofoid) Taylor that cause paralytic shellfish poisoning (PSP) are identified on the basis of morphological features in routine monitoring. Rapid and simple identification is, however, often difficult because of the morphological similarity. Fluorescent in situ hybridization (FISH) using ribosomal RNA (rRNA)-targeted probes has been studied as a method of easily identifying and enumerating species responsible for harmful algal blooms (HABs). Its application to monitoring natural populations of HAB species, however, is limited. Here, we applied the FISH method to identify and enumerate cells of A. tamarense and A. catenella in natural plankton assemblages collected from Japanese coastal waters. A. tamarense-specific (Atm1) and A. catenella-specific (Act1) probes were established based on the D2 region of the large-subunit ribosomal RNA gene (28S rDNA). With these two probes, natural cells of A. tamarense or A. catenella in field samples could easily be identified when the following three conditions were met. First, cells should be concentrated by filtration, not centrifugation, in order to avoid the loss of cells. Second, autofluorescence should be minimized; acetone was an effective decolorization reagent. Third, samples should be stored at −20 or −80 °C for long-term preservation. The results indicate that FISH is a useful tool for the rapid identification of toxic Alexandrium spp. and can facilitate the analysis of numerous natural samples.     

A shift in the dominant toxin-producing algal species in central California alters phycotoxins in food webs

In California, the toxic algal species of primary concern are the dinoflagellate Alexandrium catenella and members of the pennate diatom genus Pseudo-nitzschia, both producers of potent neurotoxins that are capable of sickening and killing marine life and humans. During the summer of 2004 in Monterey Bay, we observed a change in the taxonomic structure of the phytoplankton community—the typically diatom-dominated community shifted to a red tide, dinoflagellate-dominated community. Here we use a 6-year time series (2000–2006) to show how the abundance of the dominant harmful algal bloom (HAB) species in the Bay up to that point, Pseudo-nitzschia, significantly declined during the dinoflagellate-dominated interval, while two genera of toxic dinoflagellates, Alexandrium and Dinophysis, became the predominant toxin producers. This change represents a shift from a genus of toxin producers that typically dominates the community during a toxic bloom, to HAB taxa that are generally only minor components of the community in a toxic event. This change in the local HAB species was also reflected in the toxins present in higher trophic levels. Despite the small contribution of A. catenella to the overall phytoplankton community, the increase in the presence of this species in Monterey Bay was associated with an increase in the presence of paralytic shellfish poisoning (PSP) toxins in sentinel shellfish and clupeoid fish. This report provides the first evidence that PSP toxins are present in California's pelagic food web, as PSP toxins were detected in both northern anchovies (Engraulis mordax) and Pacific sardines (Sardinops sagax). Another interesting observation from our data is the co-occurrence of DA and PSP toxins in both planktivorous fish and sentinel shellfish. We also provide evidence, based on the statewide biotoxin monitoring program, that this increase in the frequency and abundance of PSP events related to A. catenella occurred not just in Monterey Bay, but also in other coastal regions of California. Our results demonstrate that changes in the taxonomic structure of the phytoplankton community influences the nature of the algal toxins that move through local food webs and also emphasizes the importance of monitoring for the full suite of toxic algae, rather than just one genus or species.     

Which species,Alexandrium catenella (Group I) or A. pacificum (Group IV), is really responsible for past paralytic shellfish poisoning outbreaks in Jinhae-Masan Bay,Korea?

Paralytic shellfish poisoning (PSP) caused the deaths of four people in coastal area of Korea, mainly Jinhae-Masan Bay and adjacent areas, in April 1986 and in 1996. The PSP outbreaks were caused by the consumption of mussels, Mytilus edulis. The organism that caused PSP was identified, from morphological data only, as Alexandrium tamarense which is recently renamed as A. catenella, however recent studies have shown that the morphological diagnostic characteristics used to identify Alexandrium species have uncertainties and molecular tools and other criteria should be considered as well. The organism that caused past PSP outbreaks and incidents in Korea therefore need to be carefully reconsidered. The aim of this study was to re-evaluate the species really responsible for past outbreaks of PSP in Jinhae-Masan Bay, Korea. The temporal production and fluxes of the resting cysts of Alexandrium species were investigated for one year (from March 2011 to February 2012) using a sediment trap, and the morphology and phylogeny of vegetative cells germinated from the resting cysts were analysed. The production of Alexandrium species peaked in August and November, when temporal discrepancies were found in the water temperature (22.4 and 22.7 °C in August, 19.1 and 19.6 °C in November) and salinity (29.5 and 26.1 psu in August, 30.5 and 31.8 psu in November). The morphological data revealed that Alexandrium species germinated from resting cysts collected in August have a ventral pore on the 1′ plate, whereas the 1′ plate in Alexandrium species germinated from resting cysts collected in November lacks a ventral pore. Molecular phylogenetic data for the vegetative cells from the germination experiments allowed the August and November peaks to be assigned to Alexandrium catenella (Group I) and A. pacificum (Group IV), respectively. This indicates that the production of resting cysts of A. catenella can be enhanced by relatively high water temperature. This result is not consistent with those of previous studies that A. catenella responsible for PSP outbreaks was found at relatively low water temperature. In addition, large subunit ribosomal sequences data revealed that A. pacificum isolates from Korea were closely related to those from Australia, Japan and New Zealand where the PSP toxicity of shellfish and blooms occurred in the 1990s, indicating that the introduction of toxic dinoflagellates were related to ballast water from bulk-cargo shipping. Based on these results, we concluded that past PSP outbreaks in Jinhae-Masan Bay of Korea could have been caused by A. pacificum rather than by A. catenella.     

Community structure of the macroinfauna inhabiting tidal flats characterized by the presence of different species of burrowing bivalves in Southern Chile

Several species of bivalves coexist at the lower intertidal of large tidal flats located in the enclosed or inland coast of the northern area of the Nord-Patagonic archipelagos on the Chilean coast (ca. 40–42°S): Tagelus dombeii (Lamarck), Mulinia edulis (King & Broderip), Venus antiqua King & Broderip, Semele solida (Gray), Gari solida (Gray) and Diplodonta insconspicua Philippi. To explore possible spatial variation in the community structure of the macroinfauna inhabiting sediments with different assemblages of these bivalves, seasonal sampling was carried out during 2003–2004 at two tidal flats of that area. Higher species richness and specimen densities of the macroinfauna occurred in sediments with the higher densities of bivalves, especially in sediments where the deep burrower T. dombeii reaches its greatest abundances. Our results suggest that, apart from presence of bivalves, the burrowing depth of these organisms is also important in promoting the abundance of macroinfauna. Our results are in contrast with earlier conceptualizations for community organization of the soft bottom macroinfauna inhabiting intertidal flats, related to biological interactions occurring among different phyletic groups, such as that arguing that suspension feeding bivalves (such as T. dombeii and V. antiqua) will negatively affect the recruitment of species with planktonic larvae, by filtering them before they become established in the substrate. Thus, it is concluded that beneficial effects of bivalve bioturbation overcome that negative effects on the macroinfauna, although detrimental effects may well occur at bivalve densities higher than those studied here. Electronic supplementary material Supplementary material is available for this article at and accessible for authorised users     

Large subunit rDNA sequences from Alexandrium catenella strains isolated during harmful algal blooms in Hong Kong

The partial sequences of the large subunit (24S) ribosomal RNA gene(LsurRNA) of three Alexandrium catenella strains isolatedduring the 1998 and 1989 red tide incidents in Hong Kong were compared,togetherwith the sequences of other Asian A. catenella speciescomplex. The sequences of two A. catenella strainsisolatedin 1998 were identical, despite being isolated at different time (March andApril) and different locations (eastern and southern Hong Kong). In cladisticanalysis, the two A. catenella HK98A & B strains, theA. catenella HK1989 strain, the Chinese strain clade andtheKorean/Japanese A. catenella form a clade distinct fromother A. catenella strains. Interestingly, the twoA. catenella HK98A & B strains only form a clade withtheA. catenella HK1989 strain/ChineseA. catenella (CCMP1493) with low bootstrap values (49%).     

Species diversity and abundance of dinoflagellate resting cysts seven months after a bloom of Alexandrium catenella in two contrasting coastal systems of the Chilean Inland Sea

In Chile, 90% of the fish farms and major natural shellfish beds are located in the region surrounding the Inland Sea, where over the last few decades harmful phytoplankton blooms have often been observed. The onset and recurrence of bloom events are often related to the resuspension and germination of resting cysts that have accumulated in the sediments. The degree of cyst settling, accumulation and germination is highly variable between areas and depends on physical and environmental factors. To learn how differences in oceanographic exposure, amount of river runoff and bathymetry affect dinoflagellate cyst deposition, we examined the diversity and abundance of dinoflagellate resting cysts from two hydrographically contrasting coastal areas (oceanic Guaitecas Archipelago and estuarine Pitipalena Fjord) of the Chilean Inland Sea in September 2006, seven months after a bloom of Alexandrium catenella, a producer of paralytic shellfish toxin. Cyst species diversity consisted of 18 taxa, including A. catenella and the noxious species Protoceratium reticulatum, both of which have caused blooms in the study area. Our results revealed significant differences between the two study sites in terms of the abundance and diversity of resting cysts, suggesting that in the specific case of A. catenella, only Guaitecas stations have potential for cyst accumulation and successful growth of cells. However, there was no evidence of long-term resting cyst beds of A. catenella at either study site.