Diatom Nitzschia navis-varingica (Bacillariophyceae) and its domoic acid production from the mangrove environments of Malaysia

• Main Authors: Tan, Suhnih, Teng, Singtung, Lim, Hong Chang, Kotaki, Yuichi, Bates, Stephen S., Leaw, Chui Pin, Lim, Po Teen
• Format: Article
• Language: English
• Published: Elsevier B.V. 2016
• Subjects: GE Environmental Sciences
• Online Access: http://ir.unimas.my/id/eprint/15327/2/Diatom%20Nitzschia%20-%20Copy.pdf; http://ir.unimas.my/id/eprint/15327/; https://www.scopus.com/inward/record.uri?eid=2-s2.0-84997170458&doi=10.1016%2fj.hal.2016.11.003&partnerID=40&md5=3dfde25bfc92a6b88e627f441efb35db
• Institution: Universiti Malaysia Sarawak

The distribution of the toxic pennate diatom Nitzschia was investigated at four mangrove areas along the coastal brackish waters of Peninsular Malaysia. Eighty-two strains of N. navis-varingica were isolated and established, and their identity confirmed morphologically and molecularly. Frustule morphological characteristics of the strains examined are identical to previously identified N. navis-varingica, but with a sightly higher density of the number of areolae per 1 μm (4–7 areolae). Both LSU and ITS rDNAs phylogenetic trees clustered all strains in the N. navis-varingica clade, with high sequence homogeneity in the LSU rDNA (0–0.3%), while the intraspecific divergences in the ITS2 data set reached up to 7.4%. Domoic acid (DA) and its geometrical isomers, isodomoic A (IA) and isodomoic B (IB), were detected in cultures of N. navis-varingica by FMOC-LC-FLD, and subsequently confirmed by LC–MS/MS, with selected ion monitoring (SIM) and multiple reaction monitoring (MRM) runs. DA contents ranged between 0.37 and 11.06 pg cell−1. This study demonstrated that the toxigenic euryhaline diatom N. navis-varingica is widely distributed in Malaysian mangrove swamps, suggesting the risk of amnesic shellfish poisoning and the possibility of DA contamination in the mangrove-related fisheries products