Morphological, molecular, and toxin analysis of field populations of Alexandrium genus from the Argentine Sea

Abstract

In the Argentine Sea, blooms of toxigenic dinoflagellates of the Alexandrium tamarense species complex have led to fish and bird mortalities and human deaths as a consequence of paralytic shellfish poisoning (PSP). Yet little is known about the occurrence of other toxigenic species of the genus Alexandrium, or of their toxin composition beyond coastal waters. The distribution of Alexandrium species and related toxins in the Argentine Sea was determined by sampling surface waters on an oceanographic expedition during austral spring from ~39°S to 48°S. Light microscope and SEM analysis for species identification and enumeration was supplemented by confirmatory PCR analysis from field samples. The most frequent Alexandrium taxon identified by microscopy corresponded to the classical description of A. tamarense. Only weak signals of Group I from the A. tamarense species complex were detected by PCR of bulk field samples, but phylogenetic reconstruction of rDNA sequences from single cells from one station assigned them to ribotype Group I (Alexandrium catenella). PCR probes for Alexandrium minutum and Alexandrium ostenfeldii yielded a positive signal, although A. minutum morphology did not completely match the classical description. Analysis of PSP toxin composition of plankton samples revealed toxin profiles dominated by gonyautoxins (GTX1/4). The main toxic cyclic imine detected was 13-desMe-spirolide C and this supported the association with A. ostenfeldii in the field. This study represents the first integrated molecular, morphological and toxinological analysis of field populations of the genus Alexandrium in the Argentine Sea.

Occurrence of Marine Biotoxins and Shellfish Poisoning Events and Their Causative Organisms in Argentine Marine Waters

“…During the same survey, Alexandrium aff. minutum was detected in shelf waters south of the Province of Buenos Aires and east of Valdés Peninsula (40°-44°S; Fabro et al, 2017). Pyrodinium bahamense has not been found to occur in the Argentine Sea.…”

“…As GC toxin variability meanwhile has been proven to be much higher than the three tested variants, it cannot entirely be ruled out that G. catenatum populations in the Argentine Sea also produce benzoyl GC toxins, as reported for most other parts of the world. But it is noteworthy that eventually in planktonic field populations of the Argentine Sea, PSP profiles other than those of the well-characterized Argentinean A. catenella isolates were detected (Montoya et al, 2010;Fabro et al, 2017). This finding indicates that either PSP-producing species other than A. catenella are present or that other A. catenella strains exhibit different toxin profiles.…”

“…Though this species was also observed in the Beagle Channel, it was found not to produce PSP there (Almandoz et al, 2014). Very recently, however, A. ostenfeldii was associated with PSP toxins detected in San Matías and San Jorge Gulfs and in shelf waters close to Valdés Peninsula (42°-43°S; Fabro et al, 2017). During the same survey, Alexandrium aff.…”

“…The dominant PSP-producing species in the Argentine Sea is Alexandrium catenella, initially described as Gonyaulax excavata, later re-identified as Alexandrium tamarense, and very recently recognized as Alexandrium catenella following ribosomal phylogenetic studies (John et al, 2014;Prud'homme van Reine, 2017). Blooms of A. catenella have been detected frequently since 1980 and were recorded in a latitudinal gradient from the Province of Buenos Aires to the Beagle Channel in almost the entire coastal ecosystem ( Figure 3; Carreto et al, 1981;Esteves et al, 1992;Benavides et al, 1995;Akselman, 1996;Carreto et al, 1998;Gayoso and Fulco, 2006;Montoya et al, 2010;Krock et al, 2015a;Fabro et al, 2017;Montoya et al, 2018). Such blooms have been recorded annually through spring and summer seasons from South Patagonia all the way up to Uruguay Méndez et al, 2001).…”

“…Paralytic shellfish poisoning (PSP; Carreto et al, 1981Carreto et al, , 1986Carreto et al, , 1998Carreto et al, , 2007Esteves et al, 1992;Benavides et al, 1995;Akselman et al, 1998;Gayoso, 2001; Montoya et al, 2006Montoya et al, , 2018Santinelli et al, 1994aSantinelli et al, , 2002Cadaillón, 2012;Sunesen et al, 2014;Krock et al, 2015a), 3. Spiroimine shellfish poisoning (SSP) (Almandoz et al, 2014;Fabro et al, 2017), 4. Diarrhetic shellfish poisoning (DSP; Gayoso et al, 2002;Sar et al, 2010Sar et al, , 2012Montoya et al, 2011;Sunesen et al, 2014;Gracia Villalobos et al, 2015;Krock et al, 2015a;Turner and Goya, 2015;Akselman et al, 2015;Fabro et al, 2015Fabro et al, , 2016, and 5.…”