Heterosigma akashiwo in Patagonian Fjords: Genetics, Growth, Pigment Signature and Role of PUFA and ROS in Ichthyotoxicity

Heterosigma akashiwo is the only raphidophyte described for Chilean waters. A recent 2021 fish-killing bloom event of this raphidophyte ignited scientific research, but the ichthyotoxic mechanism and environmental conditions that promote its growth are still unclear. This is the first study confirming the occurrence of H. akashiwo in Chilean waters on the basis of the region D1/D2 of the 28S ribosomal gene. The pigment signature of the CREAN_HA03 strain revealed chlorophyll-a, fucoxanthin, and violaxanthin as the most abundant pigments, but profiles were variable depending on culture and field conditions. A factorial temperature–salinity growth experiment showed a maximal growth rate of 0.48 d−1 at 17 °C and 35 in salinity, but reached a maximal cell abundance of ~50,000 cells mL−1 at 12 °C and 25 in salinity. The fatty acid profile included high levels of saturated (16:0) and polyunsaturated (18:4 ω3; 20:5 ω3) fatty acids, but superoxide production in this strain was low (~0.3 pmol O2– cell−1 h−1). The RTgill-W1 bioassay showed that the H. akashiwo strain was cytotoxic only at high cell concentrations (>47,000 cells mL−1) and after cell rupture. In conclusion, salmon mortality during H. akashiwo bloom events in Patagonian fjords is likely explained by the high production of long-chain PUFAs at high cell densities, but only in the presence of high ROS production.

[1]  Gonzalo Álvarez,et al.  Interactive effects of temperature and salinity on the growth and cytotoxicity of the fish-killing microalgal species Heterosigma akashiwo and Pseudochattonella verruculosa. , 2021, Marine pollution bulletin.

[2]  Ingrid Inostroza,et al.  Comparison of a Chilean strain of the ichthyotoxic phytoflagellate Heterosigma akashiwo (Raphidophyceae) with strains from France, Spain and New Zealand , 2021, Phycologia.

[3]  Valeria Villanova,et al.  Mixotrophy in diatoms: molecular mechanism and industrial potential. , 2021, Physiologia plantarum.

[4]  E. Spijkerman,et al.  Phytoplankton Community Responses to Interactions Between Light Intensity, Light Variations, and Phosphorus Supply , 2020, Frontiers in Environmental Science.

[5]  G. Hallegraeff,et al.  Unraveling the Karenia selliformis complex with the description of a non-gymnodimine producing Patagonian phylotype. , 2020, Harmful algae.

[6]  J. Mardones Screening of Chilean fish-killing microalgae using a gill cell-based assay , 2020 .

[7]  E. Jacob‐Lopes,et al.  Pigments from Microalgae Handbook , 2020 .

[8]  B. Krock,et al.  Production of extracts with anaesthetic activity from the culture of Heterosigma akashiwo in pilot-scale photobioreactors , 2020 .

[9]  M. Menezes,et al.  Morphological and genetic characterization of bloom‐forming Raphidophyceae from Brazilian coast , 2019, Phycological Research.

[10]  J. Gallardo-Rodríguez,et al.  Study of the ichthyotoxic microalga Heterosigma akashiwo by transcriptional activation of sublethal marker Hsp70b in Transwell co-culture assays , 2018, PloS one.

[11]  Kirsty F. Smith,et al.  New insights into the morphology and phylogeny of Heterosigma akashiwo (Raphidophyceae), with the description of Heterosigma minor sp. nov. , 2016 .

[12]  G. Hallegraeff,et al.  Fish gill damage by the dinoflagellate Alexandrium catenella from Chilean fjords: synergistic action of ROS and PUFA , 2015 .

[13]  J. Garrido,et al.  Phytoplankton pigment biomarkers: HPLC separation using a pentafluorophenyloctadecyl silica column , 2015 .

[14]  G. Hallegraeff,et al.  Progress in Understanding Algal Bloom-Mediated Fish Kills: The Role of Superoxide Radicals, Phycotoxins and Fatty Acids , 2015, PloS one.

[15]  J. Fuentealba,et al.  Neurotoxin-like compounds from the ichthyotoxic red tide alga Heterosigma akashiwo induce a TTX-like synaptic silencing in mammalian neurons , 2015 .

[16]  M. Menezes,et al.  Recurrent blooms of Heterosigma akashiwo (Raphidophyceae) in the Piraquê Channel, Rodrigo de Freitas Lagoon, southeast Brazil. , 2014, Brazilian journal of biology = Revista brasleira de biologia.

[17]  Elizabeth L. Harvey,et al.  Broad Salinity Tolerance as a Refuge from Predation in the Harmful Raphidophyte Alga Heterosigma akashiwo (Raphidophyceae) , 2013, Journal of phycology.

[18]  E. Orive,et al.  Tolerance to high irradiance levels as a determinant of the bloom-forming Heterosigma akashiwo success in estuarine waters in summer , 2012 .

[19]  I. Creed,et al.  Sinking of Heterosigma akashiwo results in increased toxicity of this harmful algal bloom species , 2012 .

[20]  G. Hallegraeff,et al.  Novel application of a fish gill cell line assay to assess ichthyotoxicity of harmful marine microalgae , 2011 .

[21]  H. Jeong Mixotrophy in Red Tide Algae Raphidophytes 1 , 2011, The Journal of eukaryotic microbiology.

[22]  K. Coyne,et al.  INTERSTRAIN VARIABILITY IN PHYSIOLOGY AND GENETICS OF HETEROSIGMA AKASHIWO (RAPHIDOPHYCEAE) FROM THE WEST COAST OF NORTH AMERICA 1 , 2011, Journal of phycology.

[23]  E. Orive,et al.  Growth response of six strains of Heterosigma akashiwo to varying temperature, salinity and irradiance conditions , 2010 .

[24]  O. Gascuel,et al.  New algorithms and methods to estimate maximum-likelihood phylogenies: assessing the performance of PhyML 3.0. , 2010, Systematic biology.

[25]  T. Waite,et al.  New method for the determination of extracellular production of superoxide by marine phytoplankton using the chemiluminescence probes MCLA and red‐CLA , 2009 .

[26]  I. Jenkinson,et al.  Extracellular polysaccharide-protein complexes of a harmful alga mediate the allelopathic control it exerts within the phytoplankton community , 2009, The ISME Journal.

[27]  D. Posada jModelTest: phylogenetic model averaging. , 2008, Molecular biology and evolution.

[28]  G. Hallegraeff,et al.  LIPID, FATTY ACID, AND STEROL COMPOSITION OF EIGHT SPECIES OF KARENIACEAE (DINOPHYTA): CHEMOTAXONOMY AND PUTATIVE LIPID PHYCOTOXINS 1 , 2007 .

[29]  T. Tengs,et al.  RAPHIDOPHYCEAE [CHADEFAUD EX SILVA] SYSTEMATICS AND RAPID IDENTIFICATION: SEQUENCE ANALYSES AND REAL‐TIME PCR ASSAYS 1 , 2006, Journal of phycology.

[30]  H. Jeong,et al.  Bacterivory by co-occurring red-tide algae, heterotrophic nanoflagellates, and ciliates , 2006 .

[31]  O. Gascuel,et al.  Approximate likelihood-ratio test for branches: A fast, accurate, and powerful alternative. , 2006, Systematic biology.

[32]  G. Hallegraeff,et al.  Ichthyotoxicity of Chattonella marina (Raphidophyceae) to damselfish (Acanthochromis polycanthus): the synergistic role of reactive oxygen species and free fatty acids , 2003 .

[33]  K. Jakobsen,et al.  GENETIC VARIABILITY AND MOLECULAR PHYLOGENY OF DINOPHYSIS SPECIES (DINOPHYCEAE) FROM NORWEGIAN WATERS INFERRED FROM SINGLE CELL ANALYSES OF rDNA 1 , 2003 .

[34]  G. Hallegraeff,et al.  Taxonomy of harmful marine raphidophytes , 2003 .

[35]  K. Jakobsen,et al.  GENETIC VARIABILITY AND MOLECULAR PHYLOGENY OF DINOPHYSIS SPECIES ( DINOPHYCEAE ) FROM NORWEGIAN WATERS INFERRED FROM SINGLE CELL ANALYSES OF rDNA , 2003 .

[36]  L. Connell Nuclear ITS region of the alga Heterosigma akashiwo (Chromophyta: Raphidophyceae) is identical in isolates from Atlantic and Pacific basins , 2000 .

[37]  I. Imai,et al.  Importance of cysts in the population dynamics of the red tide flagellate Heterosigma akashiwo (Raphidophyceae) , 1999 .

[38]  W. W. Adams,et al.  Ecophysiology of the Xanthophyll Cycle , 1999 .

[39]  K. Nagasaki,et al.  Cyst formation in the red tide flagellate Heterosigma akashiwo (Raphidophyceae) , 1996 .

[40]  Ross Ihaka,et al.  Gentleman R: R: A language for data analysis and graphics , 1996 .

[41]  D. Anderson,et al.  IDENTIFICATION OF GROUP‐ AND STRAIN‐SPECIFIC GENETIC MARKERS FOR GLOBALLY DISTRIBUTED ALEXANDRIUM (DINOPHYCEAE). II. SEQUENCE ANALYSIS OF A FRAGMENT OF THE LSU rRNA GENE 1 , 1994 .

[42]  S. J. Caldwell,et al.  Development of a cell line from primary cultures of rainbow trout, Oncorhynchus mykiss (Walbaum), gills , 1994 .

[43]  B Page,et al.  A new fluorometric assay for cytotoxicity measurements in-vitro. , 1993, International journal of oncology.

[44]  S. Yamochi Mechanisms for outbreak ofHeterosigma akashiwo red tide in Osaka Bay, Japan , 1984 .