Browsing by Author "Norambuena, Luis"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Diversity and toxicity of the planktonic diatom genus Pseudo-nitzschia from coastal and offshore waters of the Southeast Pacific, including Pseudo-nitzschia dampieri sp. nov.
    (2023) von Dassow, Peter; Mikhno, Marta; Percopo, Isabella; Orellana, Valentina Rubio; Aguilera, Victor; Alvarez, Gonzalo; Araya, Michael; Cornejo-Guzman, Sebastian; Llona, Tomas; Mardones, Jorge I.; Norambuena, Luis; Salas-Rojas, Victoria; Kooistra, Wiebe H. C. F.; Montresor, Marina; Sarno, Diana
    To expand knowledge of Pseudo-nitzschia species in the Southeast Pacific, we isolated specimens from coastal waters of central Chile (36 degrees S-30 degrees S), the Gulf of Corcovado, and the oceanic Robinson Crusoe Island (700 km offshore) and grew them into monoclonal strains. A total of 123 Pseudo-nitzschia strains were identified to 11 species based on sequencing of the ITS region of the nuclear rDNA and on ultrastructural and morphometric analyses of the frustule in selected representatives of each clade: P. australis, P. bucculenta, P. cf. chiniana, P. cf. decipiens, P. fraudulenta, P. hasleana, P. multistriata, P. plurisecta, P. cf. sabit, the new species P. dampieri sp. nov., and one undescribed species. Partial 18S and 28S rDNA sequences, including the hypervariable V4 and D1-D3 regions used for barcoding, were gathered from representative strains of each species to facilitate future metabarcoding studies. Results showed different levels of genetic, and at times ultrastructural, diversity among the above-mentioned entities, suggesting morphological variants (P. bucculenta), rapidly radiating complexes with ill-defined species boundaries (P. cf. decipiens and P. cf. sabit), and the presence of new species (P. dampieri sp. nov., Pseudo-nitzschia sp. 1, and probably P. cf. chiniana). Domoic acid (DA) was detected in 18 out of 82 strains tested, including those of P. australis, P. plurisecta, and P. multistriata. Toxicity varied among species mostly corresponding to expectations from previous reports, with the prominent exception of P. fraudulenta; DA was not detected in any of its 10 strains tested. In conclusion, a high diversity of Pseudo-nitzschia exists in Chilean waters, particularly offshore.
  • No Thumbnail Available
    Item
    Heterosigma akashiwo in Patagonian Fjords: Genetics, Growth, Pigment Signature and Role of PUFA and ROS in Ichthyotoxicity
    (2022) Flores-Lenero, Ana; Vargas-Torres, Valentina; Paredes-Mella, Javier; Norambuena, Luis; Fuenzalida, Gonzalo; Lee-Chang, Kim; Mardones, Jorge, I
    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 degrees C and 35 in salinity, but reached a maximal cell abundance of similar to 50,000 cells mL(-1) at 12 degrees C and 25 in salinity. The fatty acid profile included high levels of saturated (16:0) and polyunsaturated (18:4 omega 3; 20:5 omega 3) fatty acids, but superoxide production in this strain was low (similar to 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.