Haptophyte Diversity and Vertical Distribution Explored by 18S and 28S RibosomalRNAGene Metabarcoding and Scanning Electron Microscopy

Abstract

Haptophyta encompasses more than 300 species of mostly marine pico‐ and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte‐specific primers targeting the V4 region of the 18S, and the D1‐D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.

Phylogenetic diversity in freshwater‐dwelling Isochrysidales haptophytes with implications for alkenone production

“…In addition within Group I, we noted the presence of a distinct clade (PP = 1.0) that consisted of oligotypes from this study and previous sequences from Lakes Etang des Valles (“EV”) and Annecy in France (Simon et al., ). Our HSSU tree also showed robust support for recent shared ancestry of Groups I and III, which differs from previous studies that suggest more recent common ancestry between Groups I and II (Gran‐Stadniczeñko et al., ; Simon et al., ; Theroux et al., ).…”

“…Group II is found in a similarly broad range of environmental conditions: pH levels 7.3 to 10.5, salinities ranging from 0.05 to 270 g/L, and water temperatures from 8°C to 28°C (Chu et al., ; Liu et al., ; Longo et al., , ; Plancq et al., ; Randlett et al., ; Sun et al., ; Theroux et al., ; Toney et al., ). We observed high genetic diversity in both Groups I and II Isochyrsidales (Bendif et al., ; Edvardsen et al., ; Egge et al., ; Gran‐Stadniczeñko et al., ), but we see differing alkenone conservation between Group I and Group II (D'Andrea et al., ; Longo et al., , ; Randlett et al., ; Theroux et al., ; Toney et al., ; Zheng et al., ). In Group I, we see a conservation of tri‐unsaturated alkenone isomers (C 37:3b Me, C 38:3b Et, C 38:3b Me, C 39:3b Et; Longo et al., , ), whereas Group II culture studies point to the consistent absence of C 38 Me alkenones (Nakamura, Sawada, Araie, Suzuki, & Shiraiwa, ; Ono, Sawada, Shiraiwa, & Kubota, ; Rontani, Beker, & Volkman, ; Sun et al., ; Theroux et al., ; Zheng et al., ).…”

“…Our HSSU and HLSU results revealed another significant finding: Group I and III are more closely related than previous studies have demonstrated. Previous work reported that Groups I and II were more closely related (Gran‐Stadniczeñko et al., ; Simon et al., ; Theroux et al., ). This provides insight into why there is such conservation in the alkenones of Groups I and III in contrast to Group II.…”

“…The phylum Haptophyta and the order Isochrysidales are very diverse and occur in a range of environments (Bendif, Probert, Schroeder, & de Vargas, ; Edvardsen, Egge, & Vaulot, ; Egge et al., ; Gran‐Stadniczeñko, Šupraha, Egge, & Edvardsen, ; Liu et al., ); however, few studies have focused on the diversity of Group I Isochrysidales. Previous studies confirmed that multiple Group I operational taxonomic units (OTUs) occur in the same lake (D'Andrea et al., , ; Theroux et al., ), and a later study further recommended the establishment of a new clade within Isochrysidales called Group “EV” (Simon, López‐García, Moreira, & Jardillier, ).…”

Next‐Generation Sequencing to Identify Lacustrine Haptophytes in the Canadian Prairies: Significance for Temperature Proxy Applications

“…Although Sanger sequencing is commonly used in environmental genomic studies to identify haptophyte species in lacustrine environments (e.g., Araie et al, 2018;Coolen et al, 2004;D'Andrea et al, 2016;Theroux et al, 2010), we opted for next-generation sequencing (NGS). NGS has been previously employed when studying haptophytes, providing many novel insights into the taxonomy, phylogeny, diversity, and ecology of these algae (Egge et al, 2015;Endo et al, 2018;Gran-Stadniczeñko et al, 2017;Shalchian-Tabrizi et al, 2011;Theroux et al, 2012). Here we chose five Canadian prairie lakes from which distinct LCA profiles and 18S rRNA data were generated from sediment to identify the LCA-producer(s).…”