Molecular Identification and Toxin Analysis of Alexandrium spp. in the Beibu Gulf: First Report of Toxic A. tamiyavanichii in Chinese Coastal Waters

Abstract

The frequency of harmful algal blooms (HABs) has increased in China in recent years. Information about harmful dinoflagellates and paralytic shellfish toxins (PSTs) is still limited in China, especially in the Beibu Gulf, where PSTs in shellfish have exceeded food safety guidelines on multiple occasions. To explore the nature of the threat from PSTs in the region, eight Alexandrium strains were isolated from waters of the Beibu Gulf and examined using phylogenetic analyses of large subunit (LSU) rDNA, small subunit (SSU) rDNA, and internal transcribed spacer (ITS) sequences. Their toxin composition profiles were also determined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). All eight strains clustered in the phylogenetic tree with A. pseudogonyaulax, A. affine, and A. tamiyavanichii from other locations, forming three well-resolved groups. The intraspecific genetic distances of the three Alexandrium species were significantly smaller than interspecific genetic distances for Alexandrium species. Beibu Gulf isolates were therefore classified as A. pseudogonyaulax, A. affine, and A. tamiyavanichii. No PSTs were identified in A. pseudogonyaulax, but low levels of gonyautoxins (GTXs) 1 to 5, and saxitoxin (STX) were detected in A. tamiyavanichii (a total of 4.60 fmol/cell). The extremely low level of toxicity is inconsistent with PST detection above regulatory levels on multiple occasions within the Beibu Gulf, suggesting that higher toxicity strains may occur in those waters, but were unsampled. Other explanations including biotransformation of PSTs in shellfish and the presence of other PST-producing algae are also suggested. Understanding the toxicity and phylogeny of Alexandrium species provides foundational data for the protection of public health in the Beibu Gulf region and the mitigation of HAB events.

Combined Effects of Temperature and Toxic Algal Abundance on Paralytic Shellfish Toxic Accumulation, Tissue Distribution and Elimination Dynamics in Mussels Mytilus coruscus

“…This change in potency is advantageous to the mussels, as it results in a reduced total toxicity relative to molar concentration of toxin present. Different processes for toxin biotransformation include reduction, epimerization, oxidation, and desulfation [ 63 , 64 , 65 ]. The biotransformation potentially observed in this study resulted in the conversion to a less potent (C1+2) from a more potent (GTX1+4) form, which may be due to the epimerization process [ 66 ], and/or with the help of enzymes [ 67 ].…”

Alexandrium spp.: From Toxicity to Potential Biotechnological Benefits

“…Analgesia for 60 min was obtained with neosaxitoxin at 34 ± 2 micromol/L, saxitoxin at 58 ± 3 micromol/L, TTX at 92 ± 5 micromol/L, and decarbamoyl saxitoxin at 268 ± 8 micromol/L [89]. Wand et al in 2006 detected the presence of goyautoxins in ATGX02 strain of Alexandrium tamarense isolated near Weizhou Island in the Beibu Gulf [81], while Xu et al in 2021 found that Alexandrium tamiyavanichii isolated from Beibu Gulf waters in China produces low levels of saxitoxins and gonyautoxins [90]. The gonyautoxins are phycotoxins that act by reversibly blocking voltage-gated sodium channels at axonal levels.…”

Novel Non-paralytic Shellfish Toxin and Non-spirolide Toxicity to Finfish, Brine Shrimp, and Rotifer Observed in a Culture of the Dinoflagellate Alexandrium insuetum Isolated From the Coastal Water of China

“…In the coastal waters of China, about 11 Alexandrium species have been documented, including Alexandrium affine, Alexandrium andersonii, Alexandrium catenella, Alexandrium fraterculum, Alexandrium leei, Alexandrium minutum, Alexandrium ostenfeldii, Alexandrium pacificum, Alexandrium pseudogonyaulax, Alexandrium tamiyavanichii, and Alexandrium tamutum (Gu, 2011;Gu et al, 2013;Huang et al, 2021;Tang et al, 2021;Xu et al, 2021). In Chinese coastal waters, large-scale HABs caused by species of this genus have been reported frequently since 2000.…”