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Takata H.,Japan National Institute of Radiological Sciences | Takata H.,Marine Ecology Research Institute | Aono T.,Japan National Institute of Radiological Sciences | Tagami K.,Japan National Institute of Radiological Sciences | Uchida S.,Japan National Institute of Radiological Sciences
Estuarine, Coastal and Shelf Science | Year: 2012

Influence of dissolved organic matter (DOM) on particle-water interactions of trace metals (Co, Cu, and Cd) between particulate (>0.2 μm) and dissolved (≤0.2 μm) phases has been investigated along a salinity gradient using samples from the estuarine area of northern Sagami Bay, Japan. Partitioning experiments were performed by mixing riverine suspended particles with the mixtures of different proportions of river and marine end-members and determining concentrations of Co, Cu and Cd in particulate and dissolved phases. Concentrations and distribution coefficients (K ds) between particulate and dissolved phases of Co and Cu were dependent on the presence of DOM. The K ds of Co and Cu in the mixtures in the presence of DOM were lower than those in mixtures that had been ultraviolet-irradiated (UV-irradiated) (absence of DOM), throughout the salinity gradient. In addition, speciation calculations estimated that a greater fraction of Co and Cu in the dissolved phase was present in organic form throughout the salinity gradient, while the seawater ion concentrations and ligand competition (e.g., competition from Ca and Mg and formation of stable and soluble chloro-, sulphato-, and carbonato complexes) had a small effect on the speciation of Co. These results indicate that DOM may play an important role in controlling the speciation and the particle-water interactions of Co and Cu in the estuarine waters. As for Cd, the effect of DOM on the interactions of this metal was less intense than for Co and Cu. Seawater ions appeared to act as an important variable for controlling the particle-water interactions of Cd in the estuarine waters. © 2012 Elsevier Ltd. Source


Kato A.,Hiroshima University | Baba M.,Marine Ecology Research Institute | Suda S.,University of Ryukyus
Phycological Research | Year: 2013

The nongeniculate species Neogoniolithon brassica-florida (Harvey) Setchell et Mason is circumscribed as a polymorphic species with various gross morphologies due to it being synonymized with several previous species. However, small subunit rDNA and cox1 analyses showed that N.brassica-florida was polyphyletic, and strongly imply that crustose species lacking any protuberances such as Neogoniolithon fosliei (Heydrich) Setchell et Mason and species with protuberances or branches such as N.brassica-florida and N.frutescens (Foslie) Setchell et Mason should be treated as genetically different groups (species). Therefore, we propose the resurrection of N.frutescens. We also confirmed that N.trichotomum was distinguished from N.frutescens by slender uniform diameter branches, a conceptacle with a prominent ostiole, and large cox1 interspecific sequence differences. Male and female reproductive structures of N.trichotomum were illustrated for the first time. Neogoniolithon fosliei, was divided into three clades, each of which was recognized as a species complex based on interspecific level sequence differences within clade and morphological differences. Therefore, we treated the clade most similar to N.fosliei as N.fosliei complex (Clade B), and the other clades as respective complexes of N. cf. fosliei with yellow conceptacles (Clade A) or N. cf. fosliei with large conceptacles (Clade C). Of two species complexes (Clade A and B) were morphologically consistent with two entities of N.fosliei previously reported in the Ryukyu Islands, Japan, which is supported by their niche partitioning. DNA barcoding research of nongeniculate corallines can promote the finding of more reliable taxonomic characters and the understanding of their biological aspects. © 2013 Japanese Society of Phycology. Source


Suwa R.,Kyoto University | Suwa R.,Marine Ecology Research Institute | Kataoka C.,Toyo University | Kashiwada S.,Toyo University
Marine Environmental Research | Year: 2014

In this study, the effects of silver nanocolloids (SNCs) on the early life stages of the reef-building coral Acropora japonica were investigated. The tolerance of this species to SNC contamination was estimated by exposing gametes, larvae, and primary polyps to a range of SNC concentrations (0, 0.5, 5, 50, and 500 μg l-1). Pure SNCs were immediately ionized to Ag+ in seawater and concentrations of ≥50 μg l-1 SNC had a significant detrimental effect on fertilization, larval metamorphosis, and primary polyp growth. Exposure to 50 μg l-1 SNC did not significantly affect larval survival; however, the larvae were deformed and lost their ability to metamorphose. At the highest concentration (500 μg l-1 SNC), all gametes, larvae, and primary polyps died. These experiments provide the first data on the effects of silver-nanomaterial-contaminated seawater on cnidarians, and suggest that silver nanomaterials can influence the early development of corals through anthropogenic wastewater inputs. © 2014 Elsevier Ltd. Source


Yamamoto Y.,Hokkaido University | Yamamoto Y.,Marine Ecology Research Institute | Shibata H.,Hokkaido University | Ueda H.,Hokkaido University
Zoological Science | Year: 2013

Many attempts have been made to identify natal stream odors for salmon olfactory homing. It has recently been hypothesized that odors are dissolved free amino acids; however, it is unknown whether these odors change on a seasonal or annual basis. We analyzed dissolved free amino acid (DFAA) concentration and composition of water from the Teshio River in Hokkaido, Japan, where chum salmon (Oncorhynchus keta) returned for spawning, during juvenile downstream migration in spring and adult upstream migration in autumn with a 4-year difference. Among the 19 amino acids found in the Teshio River water, DFAA concentrations fluctuated largely, but 5-7 stable DFAA compositions (mole %) were found between the spring and autumn samples over a 4-year span. Two kinds of artificial stream water (ASW) were prepared using the same DFAA concentration in the Teshio River during the time of juvenile imprinting in spring (jASW) and adult homing in autumn (aASW), after a 4-year period. In behavioral experiments of upstream selective movement in a 2choice test tank, 4-year-old mature male chum salmon captured in the Teshio River showed significant preference for either jASW or aASW when compared to control water, but did not show any preference with respect to jASW or aASW. In electro-olfactogram experiments, adults were able to discriminate between jASW and aASW. Our findings demonstrate that the long-term stability of the DFAA compositions in natal streams may be crucial for olfactory homing in chum salmon. © 2013 Zoological Society of Japan. Source


Takata H.,Japan National Institute of Radiological Sciences | Takata H.,Marine Ecology Research Institute | Aono T.,Japan National Institute of Radiological Sciences | Uchida S.,Japan National Institute of Radiological Sciences
Estuarine, Coastal and Shelf Science | Year: 2012

Concentrations of the trace metals Co, Cu and Cd in dissolved (<0.2 μm) and particulate (>0.2 μm) phases in surface waters were determined to test whether DOC, which is an indicator of dissolved organic matter (DOM), and organic matter (OM) in suspended particulate matter (SPM) act as important estuarine variables controlling the distributions of these metals in the estuarine zone. Although the dissolved metals in the surface waters from the Sagami River to northern Sagami Bay had different behaviors in June, August, and November, 2008, concentrations of dissolved Co and Cu linearly correlated with DOC concentration, but with different slopes for fresh (salinity of ≤0.1) and estuarine (salinity of >0.1) waters. This difference in the water regime between those two metals and the DOC in Sagami Bay indicates that there are differences in composition between riverine and estuarine DOM, due to change of the composition by biogeochemical processes and the presence of additional sources, or that seawater cations are competing for binding sites of DOM during the estuarine mixing. As for particulate phase, there was no relationship between the concentrations of particulate metals and that of OM in SPM at low river flows (i.e., June and November surveys). It is thought that change of the OM composition by the additional SPM sources (anthropogenic discharge and resuspension from the seabed) contributes to the affinity of trace metals for sorption sites on the surfaces of the SPM, thereby making the evaluation of importance of OM in SPM difficult. On the other hand, at high river flow (August survey), riverine SPM significantly contributed to the estuarine SPM and it entered northern Sagami Bay with negligible composition change; however, there were weak correlation coefficients of particulate Co and Cd to OM in SPM, and there was no linear relationship between particulate Cu and OM in SPM. This can be attributed to the imbalanced competition between particle sorption and organic/inorganic complexation for Co and Cd, and prevention of particle sorption by binding Cu more strongly to dissolved organic ligands. © 2012 Elsevier Ltd. Source

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