A recently published study analyzed the phylogenetic relationship between the genera Centrodinium and Alexandrium, confirming an earlier publication showing the genus Alexandrium as paraphyletic. This most recent manuscript retained the genus Alexandrium, introduced a new genus Episemicolon, resurrected two genera, Gessnerium and Protogonyaulax, and stated that: "The polyphyly [sic] of Alexandrium is solved with the split into four genera". However, these reintroduced taxa were not based on monophyletic groups. Therefore this work, if accepted, would result in replacing a single paraphyletic taxon with several non-monophyletic ones. The morphological data presented for genus characterization also do not convincingly support taxa delimitations. The combination of weak molecular phylogenetics and the lack of diagnostic traits (i.e., autapomorphies) render the applicability of the concept of limited use. The proposal to split the genus Alexandrium on the basis of our current knowledge is rejected herein. The aim here is not to present an alternative analysis and revision, but to maintain Alexandrium. A better constructed and more phylogenetically accurate revision can and should wait until more complete evidence becomes available and there is a strong reason to revise the genus Alexandrium. The reasons are explained in detail by a review of the available molecular and morphological data for species of the genera Alexandrium and Centrodinium. In addition, cyst morphology and chemotaxonomy are discussed, and the need for integrative taxonomy is highlighted.
Multiple dinoflagellate species from the genus Karlodinium have been well known to form massive and toxic blooms that consequently cause fish kills in many coastal waters around the world. Karlodinium australe is a mixotrophic and potentially ichthyotoxic species associated with fish kills. Here, we investigated phagotrophy of K. australe (isolate KaJb05) established from a bloom event in the West Johor Strait, Malaysia, using several prey species (phytoplankton, zooplankton, and larval fish). The results showed that K. australe ingested relatively small prey cells of co-occurring microalgae by direct engulfment, while it fed on larger prey cells of microalgae by tube feeding. The results of animal exposure bioassays using rotifer (Brachionus plicatilis), brine shrimp (Artemia salina), and larval fish (Oryzias melastigma) demonstrated that phagotrophy (in terms of the trophic mode of the dinoflagellate), or micropredation (in terms of the mechanism of lethal effects on prey), played a more important role than the toxicity did in causing the lethal effects of K. australe on these aquatic animals under low cell densities of K. australe, while the mortalities of animals observed in the exposure to cell lysates of K. australe were solely caused by the toxicity. A comparison of the lethal effects between K. australe and K. veneficum revealed that the lethal effect of K. australe on rotifers was much stronger than that of K. veneficum at all cell densities applied in the experiments and the more "aggressive" micropredation of K. australe is suggested to explain the difference in lethal effect between K. austale and K. veneficum. Our results may explain why K. australe exhibited fish killings during moderate blooms at cell densities < 2.34 × 106 cells L-1, whereas K. veneficum was observed to cause massive fish kills only if the cell density was above 107 cells L-1. We believe these findings provide new insights into the ecological consequences of phagotrophy exhibited in some mixotrophic and harmful algae such as species of Karlodinium and of HAB events in general.
Coastal ecosystems are often subjected to anthropogenic disturbances that lead to water quality deterioration and an increase in harmful algal bloom (HAB) events. Using the next-generation molecular tool of 18S rDNA metabarcoding, we examined the community assemblages of HAB species in the Johor Strait, Malaysia between May 2018 and September 2019, covering 19 stations across the strait. The molecular operational taxonomic units (OTUs) of HAB taxa retrieved from the dataset (n = 194) revealed a much higher number of HAB taxa (26 OTUs) than before, with 12 taxa belong to new records in the strait. As revealed in the findings of this study, the diversity and community structure of HAB taxa varied significantly over time and space. The most common and abundant HAB taxa in the strait (frequency of occurrence >70%) comprised Heterosigma akashiwo, Fibrocapsa japonica, Pseudo-nitzschia pungens, Dinophysis spp., Gymnodinium catenatum, Alexandrium leei, and A. tamiyavanichii. Also, our results demonstrated that the HAB community assemblages in the strait were dependent on the interplay of environmental variables that influence by the monsoonal effects. Different HAB taxa, constitute various functional types, occupied and prevailed in different environmental niches across space and time, leading to diverse community assemblages and population density. This study adds to the current understandings of HAB dynamics and provides a robust overview of temporal-spatial changes in HAB community assemblages along the environmental gradients in a tropical eutrophic coastal ecosystem.
The Johor Strait has experienced rapid development of various human activities and served as the main marine aquaculture area for the two countries that bordered the strait. Several fish kill incidents in 2014 and 2015 have been confirmed, attributed to the algal blooms of ichthyotoxic dinoflagellates; however, the cause of fish kill events after 2016 was not clarified and the causative organisms remained unknown. To clarify the potential cause of fish kills along the Johor Strait, a 1-year field investigation was conducted with monthly sampling between May 2018 and April 2019. Monthly vertical profiles of physical water parameters (temperature, salinity, and dissolved oxygen levels) were measured in situ at different depths (subsurface, 1 m, 5 m, and 8 m) depending on the ambient depth of the water column at the sampling stations. The spatial-temporal variability of macronutrients and chlorophyll a content was analyzed. Our results showed that high chlorophyll a concentration (up to 48.8 μg/L) and high biomass blooms of Skeletonema, Chaetoceros, Rhizosolenia, and Thalassiosira were observed seasonally at the inner part of the strait. A hypoxic to anoxic dead zone, with the dissolved oxygen levels ranging from 0.19 to 1.7 mg/L, was identified in the inner Johor Strait, covering an estimated area of 10.3 km2. The occurrence of high biomass diatom blooms and formation of the hypoxic-anoxic zone along the inner part Johor Strait were likely the culprits of some fish kill incidents after 2016.
In the Southeast Asian region, the Philippines and Malaysia are two of the most affected by Harmful Algal Blooms (HABs). Using long-term observations of HAB events, we determined if these are increasing in frequency and duration, and expanding across space in each country. Blooms of Paralytic Shellfish Toxin (PST)-producing species in the Philippines did increase in frequency and duration during the early to mid-1990s, but have stabilized since then. However, the number of sites affected by these blooms continue to expand though at a slower rate than in the 1990s. Furthermore, the type of HABs and causative species have diversified for both toxic blooms and fish kill events. In contrast, Malaysia showed no increasing trend in the frequency of toxic blooms over the past three decades since Pyrodinium bahamense was reported in 1976. However, similar to the Philippines, other PST producers such as Alexandrium minutum and Alexandrium tamiyavanichii have become a concern. No amnesic shellfish poisoning (ASP) has been confirmed in either Philippines or Malaysia thus far, while ciguatera fish poisoning cases are known from the Philippines and Malaysia but the causative organisms remain poorly studied. Since the 1990s and early 2000s, recognition of the distribution of other PST-producing species such as species of Alexandrium and Gymnodinium catenatum in Southeast Asia has grown, though there has been no significant expansion in the known distributions within the last decade. A major more recent problem in the two countries and for Southeast Asia in general are the frequent fish-killing algal blooms of various species such as Prorocentrum cordatum, Margalefidinium polykrikoides, Chattonella spp., and unarmored dinoflagellates (e.g., Karlodinium australe and Takayama sp.). These new sites affected and the increase in types of HABs and causative species could be attributed to various factors such as introduction through mariculture and eutrophication, and partly because of increased scientific awareness. These connections still need to be more concretely investigated. The link to the El Niño Southern Oscillation (ENSO) should also be better understood if we want to discern how climate change plays a role in these patterns of HAB occurrences.
The genus Gymnodinium includes many morphologically similar species, but molecular phylogenies show that it is polyphyletic. Eight strains of Gymnodinium impudicum, Gymnodinium dorsalisulcum and a novel Gymnodinium-like species from Chinese and Malaysian waters and the Mediterranean Sea were established. All of these strains were examined with light microscopy, scanning electron microscopy and transmission electron microscopy. SSU, LSU and internal transcribed spacers rDNA sequences were obtained. A new genus, Wangodinium, was erected to incorporate strains with a loop-shaped apical structure complex (ASC) comprising two rows of amphiesmal vesicles, here referred to as a new type of ASC. The chloroplasts of Wangodinium sinense are enveloped by two membranes. Pigment analysis shows that peridinin is the main accessory pigment in W. sinense. Wangodinium differs from other genera mainly in its unique ASC, and additionally differs from Gymnodinium in the absence of nuclear chambers, and from Lepidodinium in the absence of Chl b and nuclear chambers. New morphological information was provided for G. dorsalisulcum and G. impudicum, e.g., a short sulcal intrusion in G. dorsalisulcum; nuclear chambers in G. impudicum and G. dorsalisulcum; and a chloroplast enveloped by two membranes in G. impudicum. Molecular phylogeny was inferred using maximum likelihood and Bayesian inference with independent SSU and LSU rDNA sequences. Our results support the classification of Wangodinium within the Gymnodiniales sensu stricto clade and it is close to Lepidodinium. Our results also support the close relationship among G. dorsalisulcum, G. impudicum, and Barrufeta. Further research is needed to assign these Gymnodinium species to Barrufeta or to erect new genera.
A new species of toxic benthic dinoflagellate is described based on laboratory cultures isolated from two locations from Brazil, Rio de Janeiro and Bahia. The morphology was studied with SEM and LM. Cells are elliptical in right thecal view and flat. They are 37-44μm long and 29-36μm wide. The right thecal plate has a V shaped indentation where six platelets can be identified. The thecal surface of both thecal plates is smooth and has round or kidney shaped and uniformly distributed pores except in the central area of the cell, and a line of marginal pores. Some cells present an elongated depression on the central area of the apical part of the right thecal plate. Prorocentrum caipirignum is similar to Prorocentrum lima in its morphology, but can be differentiated by the general cell shape, being elliptical while P. lima is ovoid. In the phylogenetic trees based on ITS and LSU rDNA sequences, the P. caipirignum clade appears close to the clades of P. lima and Prorocentrum hoffmannianum. The Brazilian strains of P. caipirignum formed a clade with strains from Cuba, Hainan Island and Malaysia and it is therefore likely that this new species has a broad tropical distribution. Prorocentrum caipirignum is a toxic species that produces okadaic acid and the fast acting toxin prorocentrolide.
Coral reefs are some of the most important and ecologically diverse marine environments. At the base of the reef ecosystem are dinoflagellate algae, which live symbiotically within coral cells. Efforts to understand the relationship between alga and coral have been greatly hampered by the lack of an appropriate dinoflagellate genetic transformation technology. By making use of the plasmid-like fragmented chloroplast genome, we have introduced novel genetic material into the dinoflagellate chloroplast genome. We have shown that the introduced genes are expressed and confer the expected phenotypes. Genetically modified cultures have been grown for 1 year with subculturing, maintaining the introduced genes and phenotypes. This indicates that cells continue to divide after transformation and that the transformation is stable. This is the first report of stable chloroplast transformation in dinoflagellate algae.
Matched MeSH terms: Dinoflagellida/genetics*; Dinoflagellida/growth & development
The dinoflagellate genus Alexandrium has been well known for causing paralytic shellfish poisoning (PSP) worldwide. Several non-PSP toxin-producing species, however, have shown to exhibit fish-killing toxicity. Here, we report the allelopathic activity of Alexandrium leei from Malaysia to other algal species, and its toxicity to finfish and zooplankton, via laboratory bioassays. Thirteen microalgal species that co-cultured with Al. leei revealed large variability in the allelopathic effects of Al. leei on the test algae, with the growth inhibition rates ranging from 0 to 100%. The negative allelopathic effects of Al. leei on microalgae included loss of flagella and thus the motility, damages of chain structure, deformation in cell morphology, and eventually cell lysis. The finfish experienced 100% mortality within 24 h exposed to the live culture (2000-6710 cells·mL-1), while the rotifer and brine shrimp exhibited 96-100% and 90-100% mortalities within 48 h when exposed to 500-6000 cells·mL-1 of Al. leei. The mortality of the test animals depended on the Al. leei cell density exposed, leading to a linear relationship between mortality and cell density for the finfish, and a logarithmic relationship for the two zooplankters. When exposed to the treatments using Al. leei whole live culture, cell-free culture medium, extract of algal cells in the f/2-Si medium, extract of methanol, and the re-suspended freeze-and-thaw algal cells, the test organisms (Ak. sanguinea and rotifers) all died at the cell density of 8100 cells·mL-1 within 24 h. Toxin analyses by HILIC-ESI-TOF/MS and LC-ESI-MS/MS demonstrated that Al. leei did not produce PSP-toxins and 13-desmethyl spirolide C. Overall, our findings demonstrated potent allelopathy and toxicity of Al. leei, which do not only pose threats to the aquaculture industry, fisheries, and marine ecosystems but may also play a part role in the population dynamics and bloom formation of this species.
Corals show spatial acclimatisation to local environment conditions. However, the various cellular mechanisms involved in local acclimatisation and variable bleaching patterns in corals remain to be thoroughly understood. In this study, the modulation of a protein implicated in cellular heat stress tolerance, the heat shock protein 70, was compared at both gene (hsp70) and protein (Hsp70) expression level in bleaching tolerant near-coast Acropora muricata colonies and bleaching susceptible reef colonies, in the lagoon of Belle Mare (Mauritius). The relative Hsp70 levels varied significantly between colonies from the two different locations, colonies having different health conditions and the year of collection. Before the bleaching event of 2016, near-coast colonies had higher basal levels of both Hsp70 gene and protein compared to reef colonies. During the bleaching event, the near-coast colonies did not bleach and had significantly higher relative levels of both Hsp70 gene and protein compared to bleached reef colonies. No significant genetic differentiation between the two studied coral populations was observed and all the colonies analysed were associated with Symbiodiniaceae of the genus Symbiodinium (Clade A) irrespective of location and sampling period. These findings provide further evidence of the involvement of Hsp70 in conferring bleaching tolerance to corals. Moreover, the consistent expression differences of Hsp70 gene and protein between the near-coast and reef coral populations in a natural setting indicate that the modulation of this Hsp is involved in local acclimatisation of corals to their environments.
Coastal eutrophication is one of the pivotal factors driving occurrence of harmful algal blooms (HABs), whose underlying mechanism remained unclear. To better understand the nutrient regime triggering HABs and their formation process, the phytoplankton composition and its response to varying nitrogen (N) and phosphorus (P), physio-chemical parameters in water and sediment in Johor Strait in March 2019 were analyzed. Surface and sub-surface HABs were observed with the main causative species of Skeletonema, Chaetoceros and Karlodinium. The ecophysiological responses of Skeletonema to the low ambient N/P ratio such as secreting alkaline phosphatase, regulating cell morphology (volume; surface area/volume ratio) might play an important role in dominating the community. Anaerobic sediment iron-bound P release and simultaneous N removal by denitrification and anammox, shaped the stoichiometry of N and P in water column. The decrease of N/P ratio might shift the phytoplankton community into the dominance of HABs causative diatoms and dinoflagellates.
Recent molecular phylogenetic studies of Gambierdiscus species flagged several new species and genotypes, thus leading to revitalizing its systematics. The inter-relationships of clades revealed by the primary sequence information of nuclear ribosomal genes (rDNA), however, can sometimes be equivocal, and therefore, in this study, the taxonomic status of a ribotype, Gambierdiscus sp. type 6, was evaluated using specimens collected from the original locality, Marakei Island, Republic of Kiribati; and specimens found in Rawa Island, Peninsular Malaysia, were further used for comparison. Morphologically, the ribotype cells resembled G. scabrosus, G. belizeanus, G. balechii, G. cheloniae and G. lapillus in thecal ornamentation, where the thecal surfaces are reticulate-foveated, but differed from G. scabrosus by its hatchet-shaped Plate 2', and G. belizeanus by the asymmetrical Plate 3'. To identify the phylogenetic relationship of this ribotype, a large dataset of the large subunit (LSU) and small subunit (SSU) rDNAs were compiled, and performed comprehensive analyses, using Bayesian-inference, maximum-parsimony, and maximum-likelihood, for the latter two incorporating the sequence-structure information of the SSU rDNA. Both the LSU and SSU rDNA phylogenetic trees displayed an identical topology and supported the hypothesis that the relationship between Gambierdiscus sp. type 6 and G. balechii was monophyletic. As a result, the taxonomic status of Gambierdiscus sp. type 6 was revised, and assigned as Gambierdiscus balechii. Toxicity analysis using neuroblastoma N2A assay confirmed that the Central Pacific strains were toxic, ranging from 1.1 to 19.9 fg P-CTX-1 eq cell-1, but no toxicity was detected in a Western Pacific strain. This suggested that the species might be one of the species contributing to the high incidence rate of ciguatera fish poisoning in Marakei Island.
Strains of a dinoflagellate from the Salton Sea, previously identified as Protoceratium reticulatum and yessotoxin producing, have been reexamined morphologically and genetically and Pentaplacodinium saltonense n. gen. et sp. is erected to accommodate this species. Pentaplacodinium saltonense differs from Protoceratium reticulatum (Claparède et Lachmann 1859) Bütschli 1885 in the number of precingular plates (five vs. six), cingular displacement (two widths vs. one), and distinct cyst morphology. Incubation experiments (excystment and encystment) show that the resting cyst of Pentaplacodinium saltonense is morphologically most similar to the cyst-defined species Operculodinium israelianum (Rossignol, 1962) Wall (1967) and O. psilatum Wall (1967). Collections of comparative material from around the globe (including Protoceratium reticulatum and the genus Ceratocorys) and single cell PCR were used to clarify molecular phylogenies. Variable regions in the LSU (three new sequences), SSU (12 new sequences) and intergenic ITS 1-2 (14 new sequences) were obtained. These show that Pentaplacodinium saltonense and Protoceratium reticulatum form two distinct clades. Pentaplacodinium saltonense forms a monophyletic clade with several unidentified strains from Malaysia. LSU and SSU rDNA sequences of three species of Ceratocorys (C. armata, C. gourreti, C. horrida) from the Mediterranean and several other unidentified strains from Malaysia form a well-supported sister clade. The unique phylogenetic position of an unidentified strain from Hawaii is also documented and requires further examination. In addition, based on the V9 SSU topology (bootstrap values >80%), specimens from Elands Bay (South Africa), originally described as Gonyaulax grindleyi by Reinecke (1967), cluster with Protoceratium reticulatum. The known range of Pentaplacodinium saltonense is tropical to subtropical, and its cyst is recorded as a fossil in upper Cenozoic sediments. Protoceratium reticulatum and Pentaplacodinium saltonense seem to inhabit different niches: motile stages of these dinoflagellates have not been found in the same plankton sample.
Microplanktonic red tide blooms (dominated by dinoflagellates) were observed in brackish water fish ponds of Terengganu between March 1992 to January 1993. The first short-lived bloom (2-3 days) occurred in October 1992 while the second long-lived bloom (6-7 days) occurred in January 1993. The dominant dinoflagellate species comprised of Peridinium quinquecorne (> 90% total cell count) with considerable proportion of Protoperidinium excentricum. Ciliophora consisting of Tintinopsis sp. and Favella sp. were also present during the bloom period. The total ash, chlorophyll, phaeopigment, lipid and fatty acid content of the microplankton were studied. Considerable amounts (6-11% of the total fatty acid) of the polyunsaturated fatty acid 18:3w3 (linolenic acid) were present in the microplankton. However, high amounts of 20:5w3 (eicosapentanoic acid) and 22:6w3 (docosahexaenoic acid) were present with variable but usually high amounts of 22:4w6 and 22:5w6 acids. The latter microplankton bloom contained higher amounts of 20:5w3 and 22:6w3 acids than the earlier bloom. Lipid content were three to five times higher than chlorophyll a. There was an increase with successive day after bloom outbreak in the relative proportion of total C18, C20, and C22 fatty acid components. The algae microplankton contained the w3-polyunsaturated fatty acids (PUFAs) probably needed for the growth and survival rate of grazing pond animals.
In 2015, a remarkably high density bloom of Alexandrium minutum occurred in Sungai Geting, a semi-enclosed lagoon situated in the northeast of Peninsular Malaysia, causing severe discoloration and contaminated the benthic clams (Polymesoda). Plankton and water samples were collected to investigate the mechanisms of bloom development of this toxic species. Analysis of bloom samples using flow cytometry indicated that the bloom was initiated by the process of active excystment, as planomycetes (>4C cells) were observed in the early stage of the bloom. Increase in planozygotes (2C cells) was evident during the middle stage of the bloom, coinciding with an abrupt decrease in salinity and increase of temperature. The bloom was sustained through the combination of binary division of vegetative cells, division of planozygotes, and cyst germination through continuous excystment. Nutrient depletion followed by precipitation subsequently caused the bloom to terminate. This study provides the first continuous record of in situ life-cycle stages of a natural bloom population of A. minutum through a complete bloom cycle. The event has provided a fundamental understanding of the pelagic life-cycle stages of this tropical dinoflagellate, and demonstrated a unique bloom development characteristic shared among toxic Alexandrium species in coastal embayments.
Pyrodinium bahamense (var. compressum) has been the only dinoflagellate species that has caused major public health and economic problems in the Southeast Asian region for more than 2 decades now. It produces saxitoxin, a suite of toxins that cause Paralytic Shellfish Poisoning (PSP). A serious toxicological problem affecting many countries of the world, mild cases of this poisoning can occur within 30 minutes while in extreme cases, death through respiratory paralysis may occur within 2-24 hrs of ingestion of intoxicated shellfish. Blooms of the organism have been reported in Malaysia, Brunei Darussalam, the Philippines and Indonesia. The ASEAN-Canada Red Tide Network has recorded 31 blooms of the organism in 26 areas since 1976 when it first occurred in Sabah, Malaysia. As of 1999, the most hard hit country has been the Philippines which has the greatest number of areas affected (18) and highest number of Paralytic Shellfish Poisoning (PSP) cases (about 1995). Malaysia has reported a total of 609 PSP cases and 44 deaths while Brunei has recorded 14 PSP cases and no fatalities. Indonesia, on the other hand has a record of 427 PSP cases and 17 deaths. Studies on ecological/environmental impacts of these blooms have not been done in the region. Estimates of economic impacts have shown that the loss could be up to USD 300,000 day-1. Most of the data and information useful for understanding Pyrodinium bloom dynamics have come from harmful/toxic algal monitoring and research that have developed to different degrees in the various countries in the region affected by the organism's bloom. Regional collaborative research and monitoring efforts can help harmonize local data sets and ensure their quality and availability for comparative analysis and modeling. Temporal patterns of the blooms at local and regional scales and possible signals and trends in the occurrence/recurrence and spread of Pyrodinium blooms could be investigated. Existing descriptive and simple predictive models of Pyrodinium blooms can be improved and refined to help in the management of the wild harvest and aquaculture of shellfish in a region where the people are dependent on these resources for their daily food sustainance and livelihood.
Toxin production of a Malaysian isolate of the toxic red tide dinoflagellate Pyrodinium bahamense var. compressum was investigated at various stages of the batch culture growth cycle and under growth conditions affected by temperature, salinity, and light intensity variations. In all the experiments conducted, only 5 toxins were ever detected. Neosaxitoxin (NEO) and gonyautoxin V (GTX5) made up 80 mole percent or more of the cellular toxin content and saxitoxin (STX), GTX6 and decarbamoylsaxitoxin (dcSTX) made up the remainder. No gonyautoxins I-IV or C toxins were ever detected. In nutrient-replete batch cultures, toxin content rapidly peaked during early exponential phase and just as rapidly declined prior to the onset of plateau phase. Temperature had a marked effect on toxin content, which increased 3-fold as the temperature decreased from the optimum of 28 degrees C to 22 degrees C. Toxin content was constant at salinities of 24% or higher, but increased 3-fold at 20%. Toxin content decreased 2-fold and chlorophyll content increased 3-fold when light intensity was reduced from 90 to 15 microE m-2 s-1. This accompanied a 30% decrease in growth rate. Toxin composition (mole % individual toxin cell-1) remained constant throughout the course of the nutrient-replete culture and during growth at various salinities, but varied significantly with temperature and light intensity changes. At 22 degrees C, GTX5 was 25 mole % and NEO was 65 mole %, while at 34 degrees C, GTX5 increased to 55 mole % and NEO decreased proportionally to 40 mole %. When light intensity was reduced from 90 to 15 microE m-2 s-1, NEO decreased from 55 to 38 mole %, while GTX5 increased from 40 to 58 mole %. These data suggest that low light and high temperature both somehow enhance sulfo-transferase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Gymnodinium catenatum is a cosmopolitan, bloom-forming dinoflagellate known to produce a suite of potent paralytic shellfish poisoning (PSP) toxins. Here, we revisit two major blooms of G. catenatum along the Fujianese Coast, China, in 2017 and 2018. The impact area of the 2017 bloom was larger than that of the 2018 event. Field sampling and remote satellite sensing revealed that alongshore transport driven by the southwest wind, as well as physical accumulation driven by the northeast wind, played important roles in the development and distribution of the two bloom events. The relationship between wind-induced hydrodynamic conditions and the unprecedented HAB events established in this study adds greatly to our understanding of algal bloom dynamics along the Fujianese coast. These results improve our ability to detect, track, and forecast G. catenatum blooms, thereby potentially minimizing the negative impacts of future HAB events.
Enhancing the resilience of corals to rising temperatures is now a matter of urgency, leading to growing efforts to explore the use of heat tolerant symbiont species to improve their thermal resilience. The notion that adaptive traits can be retained by transferring the symbionts alone, however, challenges the holobiont concept, a fundamental paradigm in coral research. Holobiont traits are products of a specific community (holobiont) and all its co-evolutionary and local adaptations, which might limit the retention or transference of holobiont traits by exchanging only one partner. Here, we evaluate how interchanging partners affect the short- and long-term performance of holobionts under heat stress using clonal lineages of the cnidarian model system Aiptasia (host and Symbiodiniaceae strains) originating from distinct thermal environments. Our results show that holobionts from more thermally variable environments have higher plasticity to heat stress, but this resilience could not be transferred to other host genotypes through the exchange of symbionts. Importantly, our findings highlight the role of the host in determining holobiont productivity in response to thermal stress and indicate that local adaptations of holobionts will likely limit the efficacy of interchanging unfamiliar compartments to enhance thermal tolerance.
Protein phosphatase inhibition assay (PPIA), Neuroblastoma cell-based assay (Neuro-2a CBA) and LC-MS/MS analysis revealed for the first time the production of okadaic acid (OA) by a Prorocentrum rhathymum strain. Low amounts of OA were detected by LC-MS/MS analysis. Inhibition of PP2A activity and a weak toxicity to the Neuro-2a CBA were also observed.