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To improve understanding of diversity, phylogeny and evolution in tintinnid ciliates, it is essential to link multiple molecular markers with properly identified and documented morphospecies. Accordingly, 54 tintinnid morphospecies/isolates mainly from the Yellow and East China Seas were collected and analysed. Using single‐cell approaches, sequences were obtained for three rDNA loci (18S, ITS1‐5.8S‐ITS2, D1‐D5 region of 28S). Twenty‐six tintinnid morphospecies (29 isolates) are documented by micrographs, measurements, morphologically described, and compared with the original species description. Three rDNA loci‐based phylogenetic analyses were then performed for these identified isolates. Sequences from 25 unidentified species/isolates were also included in the comparison of the three rDNA loci. Ribosomal DNA genes of the genus Leprotintinnus were analysed for the first time, showing that Leprotintinnus was closely related to Tintinnopsis radix and branched distinctly apart from the family Tintinnidiidae. Four novel clades (VI to IX) of the Tintinnopsis complex emerged in the 18S genealogies. Analyses of the relative variability in the ITS and 28S regions vs. the 18S rDNA showed that the ITS1‐5.8S‐ITS2 and ITS2 regions well co‐varied with the 18S rDNA when the variations of the latter were less than 3%, whereas at difference of less than 1%, no correlation was found between the compared loci. These findings highlight the difficulties in using variable locus‐based cut‐off divergences in circumscribing tintinnid morphospecies.

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Bacterial community structure on the surface of Ulva prolifera thalli and in seawater in an Ulva blooming region in Jiaozhou Bay was investigated by methods of denaturing gradient gel electrophoresis and 16S rDNA clone libraries. Statistical analysis on the clone libraries indicated that bacterial community structure presented no significant differences between two algal samples. Thallus-surface bacterial communities identified by 16S rDNA clone library were dominated by Alteromonadales, Flavobacteriales, and Rhodobacterales. Sequences affiliated with Gammaproteobacteria, Alphaproteobacteria and CFB were detected in all the four seawater samples. However, their different distribution frequencies among the four samples and the presence of some specific bacterial clusters in some samples indicated changes in the bacterial community composition over the course of the bloom. The dominant bacterial clades changed from Alteromonadales and Rickettsiales in A-SW, to Flavobacteriales and Alteromonadales in B-SW, to Alteromonadales and Campylobacterales in C-SW, and to Rickettsiales, Rhodobacterales and Flavobacteriales in D-SW. Some specific dominant bacterial assemblages were present in some seawater samples, such as Campylobacterales in C-SW and Actinobacteria in D-SW. Our results give an insight into the changes in the bacterial community composition in seawater in blooming region during the course of macroalgal Ulva bloom.

Tintinnids are planktonic ciliates that play an important role in marine ecosystem. According to their distribution in the world oceans, tintinnid genera were divided into several biogeographical types such as boreal, warm water, austral and neritic. Therefore, the oceanic tintinnid assemblage could be correspondingly divided into boreal assemblage, warm water assemblage and austral assemblage. The purpose of this study was to investigate the characteristics of boreal tintinnid assemblage in the Northwest Pacific and the Arctic, and to identify the connection between boreal tintinnid assemblage and neighboring assemblages. Surface water samples were collected along a transect from the East China Sea to the Chukchi Sea in summer 2014. According to the presence of boreal genera and warm water genera, three tintinnid assemblages (the East China Sea neritic assemblage, the Japan Sea warm water assemblage, and the boreal assemblage) were identified along the transect. The boreal assemblage extended from the Chukchi Sea to the waters north of the Sōya Strait. Densities peaks occurred at stations in the two branches of the Alaska Current and decreased both northward and southward. The densities were <10 ind./dm3 at most stations in Arctic region. The dominant genera (Acanthostomella, Codonellopsis, Parafavella, and Ptychocylis) accounted for 79.07±29.67% (n = 49) of the abundance in the boreal assemblage. The densities of the dominant genera covaried with strongly significant positive correlations. Tintinnids with lorica oral diameter of 22–26 μm and 38–42 μm were dominant and contributed 67.35% and 15.13%, respectively, to the total abundance in the boreal assemblage. The distribution and densities of tintinnids in the study area suggest that the Sōya Strait might be a geographical barrier for tintinnids expansion.

Magnetotactic bacteria (MTB) are distributed ubiquitously in sediments from coastal environments to the deep sea. The Pacific Manganese Nodule Province contains numerous polymetallic nodules mainly composed of manganese, iron, cobalt, copper and nickel. In the present study we used Illumina MiSeq sequencing technology to assess the communities of putative MTB in deep sea surface sediments at nine stations in the east Pacific Manganese Nodule Province. A total of 402 sequence reads from MTB were classified into six operational taxonomic units (OTUs). Among these, OTU113 and OTU759 were affiliated with the genus Magnetospira, OTU2224 and OTU2794 were affiliated with the genus Magnetococcus and Magnetovibrio, respectively, OTU3017 had no known genus affiliation, and OTU2556 was most similar to Candidatus Magnetananas. Interestingly, OTU759 was widely distributed, occurring at all study sites. Magnetism measurements revealed that all sediments were dominated by low coercivity, non-interacting single domain magnetic minerals. Transmission electron microscopy confirmed that the magnetic minerals were magnetosomes. Our data suggest that diverse putative MTB are widely distributed in deep sea surface sediments from the east Pacific Manganese Nodule Province.