Distribution and Phylogeny of Spicaticribra kingstoniiῌ rudis Species Complex

Abstract. Spicaticribra kingstonii was found in Ryumon reservoir (Kumamoto prefecture), Fukuji reservoir and Haneji reservoir (Okinawa prefecture) during the phytoplankton survey of 107 Japanese artificial reservoirs at 2009 and 2010. A similar species was found in Mae Jork Lung reservoir, Chiang Mai area, Thailand. It can be identified as Thalassiosira rudis by the pattern of central areolae and the position of rimoportulae. A new combination, Spicaticribra rudis comb. nov. was proposed for T. rudis. A strain of S. kingstonii was isolated from Haneji reservoir, and performed molecular analysis for SSU-ITS-LSU region and constructed phylogenetic tree. The phylogenetic tree shows that the root of S. kingstonii exists in the C. meneghiniana species complex, but the branch length is extremely long and the morphological similarity was so small. S. kingstonii is distributed in tropical to subtropical region, and its growth rate should be faster than those of species from cold regions. This could explain the extremely long branch length of S. kingstonii

Seven Epithemia taxa (Bacillariophyta) from Lake Akan (Japan) and their salinity tolerances

The ecologies (salinity tolerance) of many diatoms are largely unknown, despite their potential to contribute to more detailed paleoenvironmental reconstructions. This study therefore aimed to investigate the relationship between diatom species and salinity. We cultured seven cosmopolitan benthic diatom species obtained from Lake Akan, a freshwater inland lake in Japan: Epithemia adnata, E. frickei, E. gibba, E. operculata, E. sorex, E. sp. and E. turgida. Each species was cultured at eleven salinities between 0‰ and 50‰. Epithemia adnata, E. frickei and E. sorex had the highest growth rate at a salinity of 3‰, with no further increase observed above 25‰. However, E. gibba had the highest growth rate at a salinity of 5‰, with no increase at salinities ≥ 30‰. These results suggest that E. adnata, E. frickei, E. gibba, and E. sorex grow in freshwater to brackish-water environments. Epithemia operculata and E. sp. proliferated at all salinities, indicating that they can adapt to hypersaline environments. However, E. turgida did not survive in salinities >10‰, making it the species with the narrowest salinity tolerance range. These results provide new knowledge that improves the understanding of the ecology of these species in modern environments and offer insights into paleoenvironmental reconstructions through diatom analysis

Aulographis japonica sp. nov. (Phaeodaria, Aulacanthida, Aulacanthidae), an abundant zooplankton in the deep sea of the Sea of Japan

Zooplankton samples from the deep water of the Sea of Japan often contain yellowish semitransparent spheres (1.0–1.5 mm in diameter). We recognized these spheres as a single phaeodarian species (Cercozoa, Rhizaria) and described them as Aulographis japonica sp. nov. (family Aulacanthidae) in this paper. This species has a high abundance in the Japan Sea Proper Water (JSPW) and occasionally higher biomass than that of copepods. Molecular analysis based on 18S SSU rDNA revealed that Aulacantha scolymantha, which belongs to the same family as A. japonica, is closer to Aulosphaera trigonopa and Protocystis spp., which belong to different orders, than to the present species. The distribution of A. japonica is apparently restricted to low temperature water. Its biomass was the highest in the uppermost layer of JSPW, and this phaeodarian species was the second most important zooplankton below 250 m depth in terms of biomass among the total zooplankton groups. This is probably due to its generalist type of feeding. Considering its large biomass, A. japonica possibly plays an important role in matter cycles within the Sea of Japan

The seagrass Zostera marina harbors growth-inhibiting bacteria against the toxic dinoflagellate Alexandrium tamarense

Seagrasses are known to have allelopathic activity to reduce growth of phytoplankton. We found growth-inhibiting bacteria (strains E8 and E9) from Zostera marina possessing strong activity against the toxic dinoflagellate Alexandrium tamarense. Strain E9 markedly inhibited growth of A. tamarense even with initial inoculum size as small as 2.9 cells ml(-1). This bacterium also had growth-inhibiting effects on the red-tide raphidophytes Chattonella antiqua and Heterosigma akashiwo, the dinoflagellate Heterocapsa circularisquama, and the diatom Chaetoceros mitra. Small subunit (SSU) ribosomal DNA (rDNA) sequencing analysis demonstrated that the most probable affiliation of these strains was Flavobacteriaceae, and proved that another inhibitory bacterial strain (E8) was the same species as strain E9. Two other bacterial strains (E4-2 and E10), showing different colony color and isolated from the same seagrass sample, revealed no growth-inhibiting activity. Interestingly, strain E4-2 showed the same sequences as E8 and E9 (100 %), and strain E10 matched E8 and E9 with 99.80 % similarity. Growth-inhibiting bacteria against the toxic dinoflagellate Alexandrium tamarense associated with seagrass, such as Flavobacterium spp. E8 and E9, are able to repress shellfish poisoning besides the allelopathic activity of seagrass itself

Nitzschia taikiensis sp. nov. (Bacillariophyta) – a new brackish diatom from the Toberi River marsh in the eastern Hokkaido, Japan

Nitzschia taikiensis sp. nov. is a brackish diatom species found in the Toberi River marsh, eastern Hokkaido, Japan. This species has characteristics similar to Nitzschia subamphioxoides Hustedt, which was originally described by Hustedt in 1959. In the present study, we conducted a comparative morphological analysis of N. taikiensis and N. subamphioxoides. The obtained results showed that they are different species. Sampling sites of N. taikiensis were located in salt marsh environments with very low salinity (1-5‰), acidic pH (5.2-5.9) and high mud content (95.0-97.5%). Identification of this species was relatively easy based on LM and SEM image analysis of its frustule features, such as the external form and stria density. This species has not been previously reported in Japan, which could be attributed to the reduction or loss of Japanese freshwater and salt marsh environments in the coastal areas, resulting from urban and industrial development

Distribution of Growth-Inhibiting Bacteria against the Toxic Dinoflagellate Alexandrium catenella (Group I) in Akkeshi-Ko Estuary and Akkeshi Bay, Hokkaido, Japan

The distribution of growth-inhibiting bacteria (GIB) against the toxic dinoflagellate Alexandrium catenella (Group I) was investigated targeting seagrass leaves and surface waters at the seagrass bed of Akkeshi-ko Estuary and surface waters of nearshore and offshore points of Akkeshi Bay, Japan. Weekly samplings were conducted from April to June in 2011. GIBs were detected from surface of leaves of the seagrass Zostera marina in Akkeshi-ko Estuary (7.5 × 105–4.7 × 106 colony-forming units: CFU g−1 wet leaf) and seawater at the stations in Akkeshi Bay (6.7 × 100–1.1 × 103 CFU mL−1). Sequence analyses revealed that the same bacterial strains with the same 16S rRNA sequences were isolated from the surface biofilm of Z. marina and the seawater in the Akkeshi Bay. We therefore strongly suggested that seagrass beds are the source of algicidal and growth-inhibiting bacteria in coastal ecosystems. Cells of A.catenella were not detected from seawaters in Akkeshi-ko Estuary and the coastal point of Akkeshi Bay, but frequently detected at the offshore point of Akkeshi Bay. It is suggested that A.catenella populations were suppressed by abundant GIBs derived from the seagrass bed, leading to the less toxin contamination of bivalves in Akkeshi-ko Estuary

Salinity responses of benthic diatoms inhabiting tidal flats

<p>We performed culture experiments using intertidal benthic diatoms collected from a river mouth tidal flat (Fujimae Tidal Flats, Nagoya, Japan) to study their responses to salinity. The six species examined were <i>Navicula</i> aff. <i>erifuga, Karayevia amoena</i>, <i>Tryblionella apiculata</i>, <i>Planothidium delicatulum</i>, <i>Melosira moniliformis</i> var. <i>octogona,</i> and <i>Entomoneis japonica.</i> Clones were grown at ten salinity levels from 0 to 50 psu. Three species were unable to grow at low salinities (0 and 0.1 psu), but all were able to grow, though at a reduced rate, in hypersaline conditions (50 psu). All species had wider tolerance ranges than the salinity range of their original habitat (4–16 psu). Two species, <i>T. apiculata</i> and <i>K. amoena</i>, were essentially euryhaline, while the other four showed various constraints on their salinity response. Two species, <i>P. delicatulum</i> and <i>M. moniliformis</i> var. <i>octogona</i>, showed optimal growth outside the range of the salinities normally occurring in the environment from which they were isolated.</p