Karlodinium elegans sp. nov. (Gymnodiniales, Dinophyceae), a novel species isolated from the East China Sea in a dinofl agellate bloom

Abstract On May 24–29,2019,a harmful algal bloom occurred in Pingtan coastal areas,Fujian,southeast China,and caused mass mortality of cage-cultured fi sh.Two clonal cultures of an unknown naked dinofl agellate were set up from seawater samples taken during the bloom.The cultures were examined for morphological features,ultrastructure characters,photosynthetic pigments,the large subunit(LSU)of the rRNA gene,and the internal transcribed spacer(ITS)sequences,as well as acute toxicity analysis.The cell was unarmored,small-sized,and ovoid,and was characterized by elaborate striations on the epicone and hypocone.The nucleus was large,ellipsoid to oval or kidney-shaped,and centrally located in the cell.A long linear apical groove originated above the sulcus in the ventral epicone and extended to the dorsal side.An elongate,slit-like“ventral pore”was located on the left of the epicone,well away from the apical groove.The chloroplasts were yellowish brown,numerous,band like,and irregularly distributed in the cell periphery.Fucoxanthin was the main accessory pigment composition.Phylogeny topology reconstructed on partial LSU rDNA showed that the unknown dinofl agellate branched as a sister species to Karlodinium sp.(strain IFR981&IFR797,from France)and Karlodinium corrugatum(strain KDGSO08,from Australia),with genetic divergences of 0.6%and 3.3%,respectively.Based on the morphological and molecular phylogenetic analysis,we describe the novel dinofl agellate as Karlodinium elegans sp.nov.A toxicity assay revealed that the clonal culture of K.elegans(strain PTB601)had no adverse eff ect on brine shrimp(Artemia salina)and marine medaka(Oryzias melastigma),indicating it may not be a toxic species.

Quantitative proteomics provides insight into the response of the marine dinoflagellate Prorocentrum donghaiense to changes in ambient phosphorus

Dinofl agellates are the major causative agents of harmful algal blooms in the global ocean and they usually form blooms under conditions of very low dissolved inorganic phosphorus(DIP).However,the mechanisms underpinning the dinofl agellate blooms remain unclear.Here,we quantitatively compared protein expression profi les of a marine dinofl agellate,Prorocentrum donghaiense,grown in inorganic P-replete,P-defi cient,and DIP-and dissolved organic phosphorus(DOP)-resupplied conditions by employing a Tandem Mass Tag(TMT)-based quantitative proteomic approach.Proteins involved in intracellular P reallocation,organic P,and non-P lipid utilization were up-regulated under the P-defi cient condition,while inorganic phosphate transporters varied insignifi cantly.In response to the P resupplementation,nitrogen metabolism,ribosome,porphyrin,and chlorophyll metabolism were up-regulated,while lysosome,and starch and sucrose metabolism were down-regulated.Notably,photosynthesis was up-regulated and secondary metabolism was down-regulated only in the DIP-resupplied cells,whereas amino acid metabolism and vitamin B6 metabolism were up-regulated in the DOP-resupplied cells,indicating diff erential response mechanisms of P.donghaiense to DIP or DOP resupplementation.Our results indicated that P.donghaiense initiated multiple strategies in response to an ambient inorganic P-defi ciency,and its efficient DOP assimilation by providing both P and carbon sources might be a key factor driving bloom formations of P.donghaiense in a low DIP environment.

Characterization of Amphidinium(Amphidiniales,Dinophyceae)species from the China Sea based on morphological,molecular,and pigment data

Amphidinium species are amongst the most abundant benthic dinoflagellates in marine intertidal sandy ecosystems.Some of them are able to produce a variety of bioactive compounds that can have both harmful effects and pharmaceutical potentials.The diversity of Amphidinium in shallow waters along the Chinese coast was investigated by isolating single cells from sand,coral,and macroalgal samples collected from 2012 to 2020.Their morphologies were subjected to examination using light microscopy(LM)and scanning electron microscopy(SEM).A total of 74 Amphidinium strains were morphologically identified,belonging to 11 species:A.carterae,A.gibbosum,A.operculatum,A.massartii,A.cf.massartii,A.fijiensis,A.pseudomassartii,A.steinii,A.thermaeum,A.theodori,A.tomasii,as well as an undefined species.The last seven species have not been previously reported in Chinese waters.Amphidinium carterae subcladesⅠ,Ⅱ,andⅣwere found in the South China Sea,while subcladeⅢwas only found in the Yellow Sea.Threadlike body scales were observed on the surface of subcladesⅢ and Ⅳ,supporting the idea that A.carterae might contain several different species.Large subunit ribosomal RNA(LSU rRNA)sequencesbased phylogeny revealed two groups(GroupsⅠandⅡ)within Amphidinium,which is consistent with the relative position of sulcus(in touch with cingulum or not).In addition,large differences in morphology and molecular phylogeny between A.operculatum(the type species of Amphidinium)and other species,suggest that a subdivision of Amphidinium might be needed.The pigment profiles of all available strains were analyzed by high performance liquid chromatography(HPLC).Eleven pigments,including peridinin,diadinoxanthin,diatoxanthin,pheophorbide(and pheophorbide a),antheraxanthin,β-carotene,and four different chlorophylls were detected.The high pheophorbide/pheophorbide a ratio in Amphidinium implies that it may be a good candidate as a natural source of photosensitizers,a well-known anticancer drug.

Identification of dissolved and particulate carbonyl compounds produced by marine harmful algal bloom species

Carbonyl compounds, especially polyunsaturated aldehydes (PUAs), are increasingly reported as teratogenic to grazers and deleterious to phytoplankton. While PUAs have been considered to be mainly produced by diatoms after cell wounding, little is known about whether microalgae other than diatoms, particularly harmful algal bloom (HAB)-forming species, produce carbonyl compounds. In this study, we analyzed the carbonyl compounds from eight common HAB-forming species ( Akashiwo sanguinea , Karenia mikimotoi , Karlodinium venefi cum , Margalefi dinium polykrikoides , Prorocentrum donghaiense , P . minimum , Scrippsiella trochoidea , and Heterosigma akashiwo ) using gas chromatography-mass spectrometry in full scan and selected ion monitoring (SIM) modes. Our results show a ubiquitous presence of carbonyl compounds in both dissolved and particulate forms in all species we examined. In the full scan mode, 133 chromatographic peaks were detected from 51 samples altogether. Both the varieties of carbonyl compounds and their quantities were algal species dependent, although most of the carbonyl compounds could not be fully identifi ed according to the mass spectral database only due to the unavailability of enough standards for all analytes. Aided with nine standards in SIM mode, we further identifi ed and quantifi ed all nine aldehydes (2-methyl-2-pentenal, trans-2-nonenal, cis-6-nonenal, 2,6-dimethyl-5-heptenal, trans-2-hexenal, trans-2- decenal, 2,4-heptadienal, trans-trans-2,4-octadienal, and trans-trans-2,4-decadienal). Four of these nine aldehydes were detected in particulate form, which confi rmed that trans-2-nonenal could be produced by K . mikimotoi , Karl . venefi cum , P . donghaiense , P . minimum , S . trochoidea , and H . akashiwo , 2,4-heptadienal and trans-trans-2,4-decadienal by A . sanguinea , M . polykrikoides , and S . trochoidea , and trans, trans-2,4- octadienal by S . trochoidea , respectively. We proved that some dinofl agellate and raphidophyte species could contribute to the pool of carbonyl compounds including PUAs in a marine ecosystem. Some carbonyl compounds, particularly those in high cell quota and/or dissolved concentration, may be related to fi shkilling or allelopathy which needs further identifi cation and quantifi cation.

Taxonomy and toxin profi le of harmful benthic Prorocentrum(Dinophyceae)species from the Xisha Islands,South China Sea

Some benthic Prorocentrum can produce okadaic acid(OA)and dinophysistoxins(DTXs)that cause diarrheic shellfish poisoning(DSP)in humans.The diversity and toxin profi les(OA and DTXs)of benthic Prorocentrum were investigated in the Xisha Islands,South China Sea.The benthic Prorocentrum was identified by both morphological features and molecular phylogenies.Morphologies were examined by light,fluorescence,and scanning electron microscopy,and phylogenetic analyses were based on partial large subunit(LSU)rDNA and ITS1-5.8S-ITS2(ITS)region.Seven Prorocentrum species including P.borbonicum,P.caipirignum,P.concavum,P.elegans,P.cf.emarginatum,P.lima complex,and P.rhathymum were identified in Xisha Islands.Among them,P.borbonicum and P.elegans were recorded in Chinese waters for the first time.OA and DTXs contents of seven benthic Prorocentrum species were evaluated based on liquid chromatography-tandem mass spectrometry(LC-MS/MS).All Xisha Islands strains of P.lima complex produced OA at contents ranging from 1663 to 3816 fg/cell.P.caipirignum also generated OA at 407 fg/cell,but other five species had no detectable toxins.Besides,interestingly,two strains of P.lima complex produced DTX-1 only(74 and 183 fg/cell)and another two strains generated an isomer of OA and DTX-2.Our findings provided insight into the biodiversity of benthic Prorocentrum in the Xisha Islands and pointed out the potential risk of DSP in this area.