Toxic HAB species from the Sea of Okhotsk detected by a metagenetic approach, seasonality and environmental drivers

Sirje Sildever; Yoko Kawakami; Nanako Kanno; Hiromi Kasai; Akihiro Shiomoto; Seiji Katakura; Satoshi Nagai

doi:10.1016/j.hal.2019.101631

Toxic HAB species from the Sea of Okhotsk detected by a metagenetic approach, seasonality and environmental drivers

Harmful Algae. 2019 Jul:87:101631. doi: 10.1016/j.hal.2019.101631. Epub 2019 Jun 18.

Authors

Sirje Sildever¹, Yoko Kawakami², Nanako Kanno¹, Hiromi Kasai³, Akihiro Shiomoto⁴, Seiji Katakura⁵, Satoshi Nagai⁶

Affiliations

¹ National Research Institute of Fisheries Science, Yokohama Kanagawa, 236-8648, Japan.
² AXIOHELIX Co. Ltd, Chiyoda-ku, Tokyo, 101-0024, Japan.
³ Hokkaido National Fisheries Research Institute, Kushiro, Hokkaido, 085-0802, Japan.
⁴ Tokyo University of Agriculture, Abashiri, Hokkaido, Japan.
⁵ City of Mombetsu, Mombetsu, Hokkaido, Japan.
⁶ National Research Institute of Fisheries Science, Yokohama Kanagawa, 236-8648, Japan. Electronic address: snagai@affrc.go.jp.

PMID: 31349888
DOI: 10.1016/j.hal.2019.101631

Abstract

During recent decades, the distribution of harmful algal bloom (HAB) species has expanded worldwide together with the increase of blooms and toxicity events. In this study, the presence of toxic HAB species in the Sea of Okhotsk was investigated based on metagenetic data collected during 6 years of weekly monitoring. Operational taxonomic units (OTUs) associated with the toxic HAB species were detected based on amplifying 18S V7-V9 and 28S D1 rRNA gene regions. In total, 43 unique OTUs associated with toxic HAB species were revealed, with 26 of those previously not reported from the Sea of Okhotsk. More OTUs belonging to dinoflagellates were detected by 18S, whereas a similar number of OTUs associated with dinoflagellates and diatoms were detected by targeting the 28S region. Species belonging to genera Alexandrium, Karenia and Karlodinium were mainly associated with OTUs under Dinophyceae, whereas Bacillariophyceae was represented by the species belonging to genus Pseudo-nitzschia. From the detected OTUs, 22 showed a clear seasonal pattern with the majority of those appearing during summer-autumn. For Alexandrium pacificum, Aureococcus anophagefferens, and Pseudo-nitzschia pungens, the seasonal pattern was detected based on both rRNA regions. Additionally, 14 OTUs were detected during all seasons and two OTUs appeared sporadically. OTUs associated with the toxic species had low relative read abundances, which together with other factors such as similar and variable morphology as well as usage of fixatives, may explain why those species have previously not been detected by light microscopy. Environmental parameters, especially water temperature, significantly (<0.05) influenced the variability in OTU relative abundances and displayed significant (<0.05) correlations with the unique OTUs. The results of this study demonstrate the usefulness of the metagenetic approach for phytoplankton monitoring, which is especially relevant for detecting toxic HAB species.

Keywords: Environmental parameters; Metagenetic approach; Phytoplankton; Sea of Okhotsk; Seasonality; Toxic HAB species.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Diatoms*
Dinoflagellida*
Environmental Monitoring
Harmful Algal Bloom
Phytoplankton