Search

PAHs have high dissolved concentrations (Σ13PAHdiss) at the northern area off the Sakhalin Island (33-78 ng L−1) where oil and natural gas is extracted (Chizova et al.,2013). East Sakhalin Current (ESC) starting northern of the Sakhalin Island and reaching the southern Okhotsk Sea during autumn-winter, presents a latent risk of PAHs transboundary pollution. The southern Okhotsk Sea is also fed by Soya Warm Current (SWC, Summer) originating in the Sea of Japan. The seasonal interchange of SWC and ESC makes the area an excellent fishing ground, with 352,000 tons of scallops, crabs, salmon, and other major species of fish caught annually. 50+ seawater samples (~10 L) were collected from 2017 to 2022 with collaboration of the Japan Fisheries Research and Education Agency to evaluate the PAHs migration around southern Okhotsk Sea. Dissolved PAHs were concentrated, from pre-filtered (0.5 µm) samples, using C18 membranes and measured with a HPLC-fluorescence. Low-background γ-spectrometry of 234Th and 228Ra were measured at the Ogoya-Underground Laboratory, Kanazawa University using HPGe-detectors. 129I was measured using accelerator mass spectrometry at the University of Tsukuba. 234Th is constantly produced from 238U in seawater, thus the disbalance of the particle-reactive 234Th (t1/2=24.1 d) tells the scavenging due to new production. 228Ra (t1/2=5.75 y) is produced by the decay of 232Th, in the shallow continental shelves. 129I (t1/2=15.7x 106 y) is released from nuclear fuel reprocessing facilities and transported by the westerlies to the West-Pacific’s marginal seas. The Σ13PAHdiss averaged 2.59 (0.87−5.56) ng L−1. Using isomers ratios and statistical analyses, PAHs’ sources were inferred as primarily pyrogenic for all samples. Oceanographic structure was characterized by a coastal area [high salinity (>33.0 PSU), high 228Ra (0.80−1.90 mBq L−1) and low PAHs (−1)], dominated by the SWC and an offshore area [low salinity (228Ra (0.25−0.80 mBq L−1) and high PAHs (>2 ng L−1)], dominated by the ESC-influenced Okhotsk Sea Surface Water. Σ13PAHdiss were not necessarily low (1.71−5.15 ng L−1) at the endmember of SWC, and thus surface migration and isopycnal mixing does not fully explain PAHs distribution. 234Th/238U ratio was 0.65 at the endmember of SWC, 0.51 ± 0.03 in the offshore area, but only 0.36 ± 0.10 in the coastal area. Chlorophyll-a, PO43-, and SiO2 at the coastal (1.38 ± 0.76 mg m3, 0.07 ± 0.05 μM, 1.77 ± 0.65 μM, respectively) and offshore (0.61 ± 0.57 mg m3, 0.20 ± 0.08 μM, 3.64 ± 1.44 μM, respectively) areas also indicated higher primary productivity at the former, and thus scavenging of dissolved PAHs at the coastal area of southern Okhotsk Sea was nominated as a major geochemical process at the southern Okhotsk Sea. The high primary productivity and downward carbon export is key for the successful of scallop farming, but the co-scavenging of organic pollutants found by this study emphasizes the environmental risk that Sakhalin I, II present. 228Ra’s origins are multiple at the West-Pacific’s marginal seas, therefore a multiple-tracer assessment including the seaice’s role will be prepared when 129I analysis are completed.

The spatial distributions of

Radiocesium concentrations in marine biota in coastal areas of the Sea of Japan were ~0.005-0.02 Bq/kg-wet and ~0.01-0.18 Bq/kg-wet for

We examined the vertical 134Cs and 137Cs concentration profiles in the southwestern Okhotsk Sea in 2011, 2013, and 2017. In June 2011, atmospheric deposition-derived 134Cs from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) was detected at depths of 0–200 m (0.06–0.6 mBq/L). In July 2013, 134Cs detected at depths of 100–200 m (∼0.05 mBq/L) was ascribed to the transport of low-level 134Cs-contaminated water and/or the convection of radioactive depositions (

On March 11, 2011, a massive earthquake and the resultant gigantic tsunami struck the Tohoku area of Japan (the Great East Japan Earthquake) and damaged many fishing boats and fishing ports. The earthquake and the subsequent tsunami also seriously caused the damage to Fukushima Daiichi Nuclear Power Plant (FNPP). Consequently, large amounts of radioactive cesium (Cs) were released into the atmosphere and ocean and subsequently polluted fishery products of Fukushima and adjacent prefectures. The Fukushima Prefectural Federation of Fisheries Cooperative Association (Fukushima FCA) has voluntarily stopped the fishing operations off Fukushima Prefecture since March 2011 due to the influence by the FNPP accident. The concentration of radioactive Cs in seawater rapidly decreased by ocean processes, and accordingly the concentration in fishery products did reduce. From April to June 2011, the proportion of inspected specimens off Fukushima exceeding the Japanese regulatory limit was 57.1%, but it decreased and continued to be 0% after April 2015. In addition, most of fishing industries in Fukushima Prefecture have been already restored from the damage by the earthquake and its aftermath. The Fukushima FCA started the trial fishing operation from June 2012.

We developed a simple method for 40K removal by acidified water leaching combined with ammonium phosphomolybdate coprecipitation, for estimating low levels of radiocesium in Japanese flounder. 40K removal from ashed samples was approximately 98%, with the radiocesium yield of ~98%. The treatment reduced the γ-spectral baseline to ~1/5 at ground and ~3/100 at underground levels (1.04 and 0.11 cph/keV, respectively). Faint signal of 134Cs, which is embedded in the Compton continuum of 40K in an untreated sample, was detected.

Strontium-90 (90Sr) was released together with radioactive cesium (Cs) from the Fukushima Dai-ichi Nuclear Power Plant (FNPP) accident. Although the total amount of 90Sr released into the marine environment from the FNPP was estimated to be a factor of 100 lower than that of 137Cs, the public have been concerned about the safety of commercial species because of the tendency of accumulation in bones of organisms, its long physical half-life and less information about 90Sr concentrations in commercial species. In this study, we investigated the concentrations of 90Sr in marine fishes off Japan before and after the FNPP accident. Except for within a 20-km radius from the FNPP, 90Sr concentrations higher than the background level (

This study examined the spatial profiles of 134Cs concentrations in the Japan Sea (particularly in the northeastern area) in July 2017 and July 2018. We detected 134Cs in water samples above a depth of ~200 m (~0.3–1 mBq/L decay-corrected to the date of the Fukushima Dai-ichi Nuclear Power Plant accident), which predominantly reflected the mixing of 134Cs-contaminated Tsushima Warm Current (TWC) water within 4 years after 134Cs re-entry from the Pacific Ocean into the Japan Sea in 2013. Furthermore, 134Cs was only detected at depths of 300 m and 500 m (~0.2 mBq/L) in the northern Japan Basin, which corresponded to ~30% of the annual mean concentration levels in TWC water (0.75 mBq/L). Observed spatial variations in 134Cs concentrations were explained by the surface TWC circulation and subsequent convection processes.

Sediment samples were collected from 20 stations in the port areas around three cities (Jakarta, Bali and Manado) in Indonesia in 2011 and from 9 stations in the port areas in northern Kyushu, Japan in 2010. High concentrations of tributyltin (TBT) were found in sediments collected in front of the shipyard in Bitung port, Manado (4.25 μg/g wet weight) and in Benoa port, Bali (0.21 μg/g wet weight). High TBT concentra- tions were also detected in sediments from next to the shipyard in Hakata port (0.63 μg/g wet weight), Fukuoka, Japan. These results suggest that ports might be major sources of TBT pollution in Indonesia and Japan, even though TBT usage has been regulated in Japan since 1990.

Tributyltin-binding protein type 1 (TBT-bp1) is a member of the lipocalin family of proteins which bind to small hydrophobic molecules. In this study, we expressed a recombinant TBT-bp1 (rTBT-bp1, ca. 35kDa) in a baculovirus expression system and purified the protein from the hemolymph of silkworm larvae injected with recombinant baculovirus. After incubation of a mixture of rTBT-bp1 and TBT and its fractionation by means of gel filtration chromatography, TBT was detected in the elution peak of rTBT-bp1, confirming the binding potential of rTBT-bp1 for TBT. An assay of the ability of rTBT-bp1 or native TBT-bp1 (nTBT-bp1) to restore osteoblastic activity inhibited by TBT showed that co-treatment of the scales with rTBT-bp1 or nTBT-bp1 in combination with TBT restored osteoblastic activity in goldfish scales, whereas treatment with TBT alone significantly inhibited osteoblastic activity. These results suggest that TBT-bp1 as a lipocalin member might function to decrease the toxicity of TBT by binding to TBT.

We successfully purified Trub.TBT-bpα, a tributyltin (TBT) binding protein (bp) of the tiger puffer, Takifugu rubripes. Tiger puffer was injected intraperitoneally with TBT (1.0 mg/kg body weight) and Trub.TBT-bpα was purified from serum by ammonium sulfate fractionation, gel filtration chromatography and polyacrylamide gel electrophoresis. Gel electrophoresis revealed that the Trub.TBT-bpα has a molecular mass of approximately 48.5 kDa and contains at least 40% N-glycan. The deduced 212 amino acid sequence of the protein showed the highest identity (41%, 212 amino acid overlap and E-value: 9e−42) with TBTbinding protein type 1 (TBT-bp1) of Paralichthys olivaceus (Japanese flounder). Analysis of the gene structure of Trub.TBT-bpα suggests that this protein belongs to the lipocalin superfamily, which may be important in the accumulation and elimination of TBT. Phylogenetic analysis suggests that functionalization of TBT-bps has occurred during evolution, and that the functions of this group of proteins might be important for fish survival.

Following the oil spill accident of the Solar I tanker in 2006 off the coast of Guimaras Island in the Philippines, polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs in some aquatic organisms were investigated at Luzaran in Guimaras and Taklong Islands, which were heavily polluted with spilled oil, immediately and 1 month after the accident. The concentrations of total PAHs were 11.9-52.3 ng/g dry weight in fish. Meanwhile, total PAH concentrations in shellfish were 38.0-3,102 ng/g dry weight in Luzaran and 128-236 ng/g dry weight in Taklong. Pyrene, phenanthrene, and fluoranthene were dominant in most fish and chrysene in all shellfish. Significantly higher concentrations of all alkylated homologs were detected in shellfish than in fish. These differences had two possible causes, that is, the differences between fish and shellfish could be attributed to the uptake routes and/or their metabolizing abilities.

To clarify the level of contamination with radioactive cesium (radiocesium) discharged from Fukushima Dai-ichi Nuclear Power Plant (FDNPP), three fish species caught in the main harbor of FDNPP were subjected to γ-ray analysis. The concentration of radiocesium in muscle differed among individual fish, even those of similar size of the same species, and showed little relation to the standard length of fish. The maximum concentration of radiocesium (202 kBq/kg wet) was detected from fat greenling samples. A comparison to data from outside the port indicated that the level of radiocesium contamination inside the port was higher than that outside. We found that β-rays were emitted from otoliths of fishes caught in the port of FDNPP. β-ray intensities were correlated with the concentrations of radiocesium in muscles of the three fish species. In Japanese rockfish, the β-ray count rates from otoliths were significantly correlated with the concentration of radiocesium and (90)Sr in the whole body without internal organs of Japanese rockfish. However, no β-rays were detected from brown hakeling samples collected around FDNPP, suggesting that the detection of β-rays from otoliths may indicate living in the main harbor of FDNPP.

After the Fukushima Dai-ichi Nuclear Power Plant (FNPP) accident, which occurred in March of 2011, the National Research Institute of Fisheries Science (NRIFS) undertook emergent radioactivity monitoring of 63 samples of small epipelagic fishes (such as sardine and Japanese anchovy) collected by commercial fishery boats off the Kashima-Boso area (located to the south of the Fukushima coast) from 24 March 2011 to 21 March 2013. Fluctuations in the radiocesium concentration in fish muscles synchronized with the decreasing concentration from seawater near the fishing ground; the radiocesium concentration in fish muscles reached a maximum of 31 Bq/kg-wet in July 2011, after which it declined gradually. From 2012 to 2013, the radiocesium concentrations in fish muscles were low (0.58–0.63 Bq/kg-wet). Compared to the 137Cs concentration before the FNPP accident, 137Cs concentration in fish muscles in 2013 was still about 10 times higher, whereas it was about 4.5 times higher in seawater near the fishing ground in 2012.

Levels of radioactive cesium (radiocesium, 134Cs + 137Cs) detected in fish caught at the Fukushima Dai-ichi Nuclear Power Plant (FNPP) Port are summarized. The mean concentration of radiocesium in three fish species (fat greenling, Japanese rockfish, and spotbelly rockfish) was significantly different from that in other fish species studied (brown hakeling, black rockfish, Japanese black porgy, olive flounder, marbled flounder). The levels of radiocesium in fat greenling decreased gradually from 100 kBq/kg-wet in 2013 to several kBq/kg-wet in 2014. A migration of fat greenling into the FNPP Port was assumed to explain the fact that fish containing low radiocesium levels were caught at the port. A low but significant correlation between the total length of the fish and the radiocesium concentration in the muscles was observed in fat greenling caught at the FNPP Port.

The artificial radionuclides 131I, 134Cs, and 137Cs released from FNPP were detected in Japanese sardine (Sadinopes melanostictus) and Japanese anchovy (Engraulis japonicus) off the Kanto area of Japan. In the research period from 24 March 2011 to 13 July 2011, the maximum concentrations of 131I, 134Cs, and 137Cs were detected in the internal organs of Japanese anchovy collected on 24 March 2011. The concentration of 131I in the internal organs tended to be higher than that in muscle and the whole body, although no clear tendency was observed for 134Cs and 137Cs; it was thought that that was caused by 131I of the planktonic contents in the internal organs. These radionuclides detected in sardine and anchovy would be derived through the atmospheric pathway from FNPP to off the Kanto area, because these radionuclides were detected before the direct release of contaminated water into the ocean from FNPP.

This section introduces results of an investigation for radiocesium (134Cs and 137Cs) in sea sediment. The three-dimensional spatial distributions of radiocesium in sea sediment to a 14-cm core depth were surveyed from off the northern part of Ibaraki Prefecture to off Fukushima Prefecture with 5-min horizontal resolution in July 2012, approximately 16 months after the Fukushima Dai-ichi Nuclear Power Plant (FNPP) accident. A high concentration band was observed along the 100-m isobaths where the concentration of the 137Cs reached 1,240 Bq/kg-dry at the maximum and where vertical profiles of the concentration generally had an exponential-type decline with depth. The concentrations were very low at the area shallower than 100 m of depth north from the FNPP, where vertical concentration peaks often occurred in deeper layers. These horizontal and vertical distribution patterns are suggested to be mainly determined by the supplied amount of radiocesium from the radiocesium-contaminated bottom seawater and the ability of radiocesium adsorption as dependent on the grain size of the sediment.

Understanding the evolutionary mechanisms of toxin accumulation in pufferfishes has been long-standing problem in toxicology and evolutionary biology. Pufferfish saxitoxin and tetrodotoxin-binding protein (PSTBP) is involved in the transport and accumulation of tetrodotoxin and is one of the most intriguing proteins related to the toxicity of pufferfishes. PSTBPs are fusion proteins consisting of two tandem repeated tributyltin-binding protein type 2 (TBT-bp2) domains. In this study, we examined the evolutionary dynamics of TBT-bp2 and PSTBP genes to understand the evolution of toxin accumulation in pufferfishes. Database searches and/or PCR-based cDNA cloning in nine pufferfish species (6 toxic and 3 nontoxic) revealed that all species possessed one or more TBT-bp2 genes, but PSTBP genes were found only in 5 toxic species belonging to genus Takifugu. These toxic Takifugu species possessed two or three copies of PSTBP genes. Phylogenetic analysis of TBT-bp2 and PSTBP genes suggested that PSTBPs evolved in the common ancestor of Takifugu species by repeated duplications and fusions of TBT-bp2 genes. In addition, a detailed comparison of Takifugu TBT-bp2 and PSTBP gene sequences detected a signature of positive selection under the pressure of gene conversion. The complicated evolutionary dynamics of TBT-bp2 and PSTBP genes may reflect the diversity of toxicity in pufferfishes.

Contaminations in sediments by polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs were investigated at 44 sites in Osaka Bay, Japan. Concentrations of total PAHs and alkylated PAHs were in the range 6.40-7800 ng/g dry weights and 13.7-1700 ng/g dry weights, respectively. The PAH concentrations tended to be higher along the shoreline in the vicinities of big ports, industrialized areas, and densely populated regions such as the cities of Osaka and Kobe. The major sources appeared to be pyrogenic or both pyrogenic and petrogenic at most of the sites. PAH concentrations were remarkably high at a site near Kobe, where the concentrations of dibenzo(a,h)anthracene and benzo(g,h,i)perylene exceeded the effects-range-medium concentration and eight PAHs were above the corresponding effects-range-low concentrations. Those PAHs may have been derived from the great fire associated with the large earthquake in 1995.

We investigated levels of the pollutant tributyltin (TBT) in blood of pufferfishes (six species), Japanese sea perch, red sea bream, Japanese common goby, Japanese flounder, rockfish, conger eel, and sea mullet collected off the coast of northern Kyushu, Japan. We found considerable levels of TBT (1.4–190 ng/mL) accumulated in the blood of these fish. Blood TBT concentrations were 1.3–22.5 times liver concentrations and 4.9–78 times muscle concentrations, except in conger eel and mullet. We detected TBT (16–111 ng/mL-blood) in the plasma of the fine-patterned puffer (Takifugu poecilonotus) year-round, without any apparent seasonal trend. These results suggest that fish inhabiting coastal areas of Kyushu, Japan, continue to be contaminated with TBT.