Yurika Ujiie

Kōchi University · Center for Advanced Marine Core Research

The increase discharge of titanium dioxide (TiO2) nanoparticles, derived from engineered material waste, exerts a detrimental impact on both the marine ecosystem and public health. The cytotoxicity of TiO2 nanoparticles on marine organisms should be imperatively understood to tackle the urgent concern for the well-being of marine life. Various conc...

Foraminifera, the most ancient known calcium carbonate-producing eukaryotes, are crucial players in global biogeochemical cycles and well-used environmental indicators in biogeosciences. However, little is known about their calcification mechanisms. This impedes understanding the organismal responses to ocean acidifi-cation, which alters marine cal...

Titanium dioxide nanoparticles (NPs) have numerous applications, and their demands have increased as an alternative for banned sunscreen filters. However, the underlying mechanisms of their toxicity, remain largely unknown. Here, we investigate the mechanism of TiO2 NP cytotoxicity and detoxification through time-course experiments (1, 6, and 24 h)...

Ocean acidification is now progressing, primarily due to the fact that the oceans have absorbed about 50% of the anthropogenic CO2 emitted since the industrial revolution. Many marine calcifying organisms, such as foraminifers and coccoliths, are known to build their shells using carbonate ions present in the seawaters surrounding them. Carbonate s...

The adverse effects of engineered nanomaterials (ENM) in marine environments have recently attracted great attention although their effects on marine benthic organisms such as foraminifera are still largely overlooked. Here we document the effects of three negatively charged ENM, different in size and composition, titanium dioxide (TiO2), polystyre...

Marine protists play an important role in oceanic ecosystems and biogeochemical cycles. However, the difficulties in culturing pelagic protists indicate that their ecology and behavior remain poorly understood; phylogeographic studies based on single-cell genetic analyses have often shown that they are highly divergent at the biological species lev...

Phylogenetic reconstruction (Bayesian analysis, 50% majority consensus tree) based on partial small subunit ribosomal DNA sequences (769 base pairs) derived from individual Globigerinoides ruber specimens. Sequences obtained in the present study are shown in bold. Open and solid columns indicate clades of the five genetic types. Numbers at each nod...

Changes in the sum of the length and breadth at the umbilical side of the shell in relation to shell weight in genetic types Ia, Ib, and IIa. Open circles correspond to type Ia, gray triangle to type Ib, and black squares to type IIa. Black solid, gray solid, and dashed lines are the regression lines of types Ia, Ib, and IIa, respectively. (PDF)

Single-cell genetic analysis is an essential method to investigate the biodiversity and evolutionary ecology of marine protists. In protist groups that do not reproduce under laboratory conditions, this approach provides the only means to directly associate molecular sequences with cell morphology. The resulting unambiguous taxonomic identification...

The North Pacific Subtropical Gyre (NPSG) has two important functions, i.e., one in ocean-heat transfer and another as a driving force for circulation of the surface and intermediate waters on the basin scale. In the present study, we describe records of the vertical thermal structures and distributions of water masses in the upper ocean of the sub...

Investigations of biodiversity, biogeography and ecological processes rely on the identification of "species" as biologically significant, natural units of evolution. In this context, morpho-taxonomy only provides an adequate level of resolution if reproductive isolation matches morphological divergence. In many groups of organisms, morphologically...

Ecological adaptation to environmental changes is a strong driver of evolution, enabling speciation of pelagic plankton in the open ocean without the presence of effective physical barriers to gene flow. The tropical ocean environment, which plays an important role in shaping marine biodiversity, has drastically and frequently changed since the Pli...

Bayesian phylogenies of the SSU rDNA (A) and LSU rDNA (B) sequences obtained for P. obliquiloculata and two outgroup species. Numbers and circles on the nodes are in the same manner with Fig 4. (EPS)

The provenance of hemipelagic sediments in the Shikoku Basin during late Cenozoic time was studied through the temporal variations in the Sr–Nd–Pb isotopic compositions of detrital sediments from Integrated Ocean Drilling Program Site C0011 from the late Miocene (7 Ma) to the present. Detrital sediments at Site C0011 are interpreted as a mixture of...

In an attempt to provide an integrative taxonomy in which we synthesize geographic, ecological and morphological differentiations that can occur among genuine (pseudo)cryptic species, we provide supplementary information about the species status of modern planktonic foraminiferal genetic types found within spinose morpho-species Globigerinoides sac...

The use of planktonic foraminifera in paleoceanography requires taxonomic consistency and precise assessment of the species biogeography. Yet, ribosomal small subunit (SSUr) DNA analyses have revealed that most of the modern morpho-species of planktonic foraminifera are composed of a complex of several distinct genetic types that may correspond to...

Genetic analyses of planktonic foraminifera have unveiled significant levels of cryptic diversity, thus calling into question the usefulness of the morphological species concept for paleoceanographic reconstructions. Here, we present single-specimen combined genetic and morphological analyses performed on living Truncorotalia truncatulinoides colle...

Many holoplanktons disperse passively without active habitat choice. Their morphology may vary over wide distribution ranges by phenotypic plasticity or allelic variation. Planktic foraminifera, which are unicellular holoplanktons and occur in every ocean, could be an excellent system to study diversity and evolution in cellular responses to the en...

Evolutionary processes in marine plankton have been assumed to be dependent on the oceanic circulation system, which transports plankton between populations in marine surface waters. Gene flow facilitated by oceanic currents along longitudinal gradients may efficiently impede genetic differentiation of pelagic populations in the absence of confound...

Collodaria are the only group of Radiolaria that has a colonial lifestyle. This group is potentially the most important plankton in the oligotrophic ocean because of its large biomass and the high primary productivity associated with the numerous symbionts inside a cell or colony. The evolution of Collodaria could thus be related to the changes in...

Photographs of specimens. Black bar is 30 µm. (a) Collozoum inerme OS293, (b) Collophidium ellipsoides VF167, (c) Sphaerozoum ovodimare GFColony6. (TIF)

Bayesian phylogeny of the SSU rDNA sequences obtained from the radiolarians. Four novel collodarian sequences and two environmental sequences (<3 µm) are shown in bold and light gray text, respectively. Order names are shown to the right of the balck bars. Numbers on nodes indicate posterior probabilities of the Bayesian method and bootstrap values...

Deglaciation process is one of the results that the tropical climate forcing impact on the global changes by its large heat capacity. However, the deglacial fluctuation has poorly been explored in the tropical Pacific area due to less resolution records from the marine deposits. The Okinawa region is available to represent the high-resolution paleo...

The coiling direction—sinistral (left-coiled) or dextral (right-coiled)—of planktonic foraminiferal shells is a classical proxy used to assess past environmental changes and to understand their evolutionary patterns. Globorotalia truncatulinoides is composed of five different genetic types (I to V), each with a specific biogeographic distribution....

Recent molecular studies show multiple cases of cryptic diversification in planktic foraminifera; however, the geographic distribution of the cryptic species is poorly known. Herein, we present the first insight into the cryptic diversity of planktic foraminifera from Northwest Pacific samples. We obtained 97 new SSU rDNA sequences representing 13...

Recent molecular studies show multiple cases of cryptic diversification in planktic foraminifera; however, the geographic distribution of the cryptic species is poorly known. Herein, we present the first insight into the cryptic diversity of planktic foraminifera from Northwest Pacific samples. We obtained 97 new SSU rDNA sequences representing 13...

One of the key hypotheses of paleoceanography is that planktonic foraminiferal morphospecies record reasonably stable and homogeneous oceanographic and climatic characteristics over their geographic and stratigraphic ranges. The discovery of numerous genetically-defined cryptic species challenges the morphospecies concept in planktonic foraminifera...

Gallitellia vivans (Cushman) is the only triserial coiling species among modern planktic foraminifera. Although previous studies suggested that G. vivans is a planktic species, it was unreported for a long time because of its small test and its low abundance in the water column and deep-sea sediments. Therefore, its distribution and ecology are poo...

Gallitellia vivans is the only Recent representative of the triserial planktonic foraminiferal family Guembelitriidae. The origin and evolution of this interesting albeit poorly known family are enigmatic. To elucidate the phylogenetic relationships between G. vivans and other planktonic foraminifera, we sequenced the small subunit ribosomal DNA (S...

The shifting coiling direction of the morphospecies Globorotalia truncatulinoides has been widely used to reconstruct the environmental change in Paleoceanography. This morphospecies, however, is composed of four genetic types (1 to 4) having biogeographic distribution. The genetic type 2 has only having both of left- and right- coiling forms and l...

The Mg/Ca ratio within foraminiferal calcareous tests (shells) is widely used to reconstruct past seawater temperature. However, recent studies reported that the organic components within a test affect the Mg/Ca distribution. In this study, we have measured the Mg/Ca, Sr/Ca, and Ba/Ca ratios within the planktonic foraminifera Pulleniatina obliquilo...

Two IMAGES cores MD98-2196 (the Okinawa Trough side) and MD01-2398 (the Ryukyu Trench side) present a 250 kyr precise record of the oceanic environment in the Ryukyu Arc region, where is a key area for the Kuroshio Current of the subtropical circulation in the North Pacific Ocean. Here we reconstruct the changes in the surface and intermediate wate...

Planktonic foraminifera, marine zooplankton with calcareous tests, are widely dispersed in all oceans. Because the diversity of these foraminifera is controlled by the environmental components (sea temperature, salinity, etc.), distinct species assemblages occur in several provinces from tropical to subpolar area dependent on circulation patterns o...

Turbidite is induced by various geologic events such as earthquake, flood, tsunami, and so on. Especially, seismo-turbidite (e.g. Inouchi et al., 1996) and flood induced turbidite (hyperpycnite: e.g. Mulder et al., 2003) occupy majority of reported turbidites, and are often used as indicators of earthquake and catastrophic river flow, respectively....

In the northwestern Pacific Ocean, the Kuroshio Current is a main component of subtropical circulation and heat transfer under the monsoon and ENSO system. The Ryukyu Arc region, especially the Okinawa Trough, is a key area for studying past variability of the Kuroshio since it is the area where the current becomes strong after diverging from the N...

The Kuroshio Current is the major western boundary current of the North Pacific Ocean and has had a large impact on surface water character and climate change in the northwestern Pacific region. The Kuroshio Current becomes a distinctive surface flow in the Ryukyu Arc region after diverging from the North Equatorial Current and passing through the...

The hugest marginal sea has been developed from the East China Sea in the NW Pacific Ocean. Especially, the Kuroshio Current flows as a main component of heat transfer in the NW Pacific Ocean and strongly affects climate changes of this region. The Okinawa Trough is a key area for studying past variability of the Kuroshio since it is the source are...

The Kuroshio Current as the western boundary current was effects on every character of surface water masses in the NW Pacific Ocean and on climate changes in the NW Pacific region. As it passes through the Okinawa Trough of the Ryukyu Arc region, the Kuroshio Current strengthens its nature after diverging from the North Equatorial Current (NEC), so...

Biogenic opal and ice-rafted detritus (IRD) data from sediments in the Okhotsk Sea and the neighboring North Pacific revealed the remarkable reduction in opal production and southward advancement of sea-ice covered area during the last glacial maximum, resulting also southward shift of high biological productive area in the northwestern North Pacif...

Detailed bathymetric survey revealed development of seven mud volcanoes in the Kumano Trough, central Nankai Trough. Three piston cores were collected from the three mud volcanoes (Kumano Knoll No. 3, 5, and 6), and one piston core was obtained from the basin floor of the Kumano Trough. We will report about the origin and history of the mud volcano...

Recent planktonic foraminifera were analyzed in 52 surface sediment samples collected from the Ryukyu Are region in the northwestern Pacific Ocean and adjacent East China Sea with the goals of establishing relationships between species distributions and oceanographic features with emphasis on the Kuroshio Current. Thirty-nine species of planktonic...

Two piston cores were collected from the cones of two mud volcanoes identified by a side-scan sonar survey east of Tanega-shima Island on the landward slope of the northern Ryukyu Trench to clarify the internal nature of the mud diapir. The upper part (Unit I) of both cores consists of normal hemipelagic sediments, whereas the lower portions (Unit...

The existence of a land bridge connecting the central-southern Ryukyu Arc to Taiwan during the last glacial stage (oxygen isotope stages 2 to 4) and its postglacial disappearance are demonstrated by variations in the planktic δ18O values and the frequency of Pulleniatina in 11 piston cores from the Okinawa Trough region. The upward increase in the...

article i nfo One of the key hypotheses of paleoceanography is that planktonic foraminiferal morphospecies record reasonably stable and homogeneous oceanographic and climatic characteristics over their geographic and stratigraphic ranges. The discovery of numerous genetically-defined cryptic species challenges the morphospecies concept in planktoni...