Remarkable shifts in the megabenthic community structure over four decades in Tokyo Bay, Japan, in relation to environmental variations.

We investigated long-term changes in the megabenthic community in Tokyo Bay, Japan, using data from fisheries-independent trawl surveys conducted from 1977 to 2023. In addition, we examined the potential relationship between changes in biotic communities and environmental conditions. The total abundance and biomass exhibited an increasing trend until 1987, followed by a substantial decline from the late 1980s to the 1990s due to a decrease in small to medium-sized fish and crustacean species.

Monitoring the Health of Coastal Environments in the Pacific Region-A Review.

Coastal areas provide important ecological services to populations accessing, for example, tourism services, fisheries, minerals and petroleum. Coastal zones worldwide are exposed to multiple stressors that threaten the sustainability of receiving environments. Assessing the health of these valuable ecosystems remains a top priority for environmental managers to ensure the key stressor sources are identified and their impacts minimized.

Concomitant downregulation of neuropeptide genes in a marine snail with consecutive sexual maturation after a nuclear disaster in Japan.

Consecutive sexual maturation (CSM), an abnormal reproductive phenomenon of a marine snail, , has occurred since 2017 in the vicinity of the Fukushima Daiichi Nuclear Power Plant after the nuclear disaster there. We hypothesized that alterations in animal physiology mediated through genetic/epigenetic changes could sensitively reflect environmental pollution. Understanding the mechanism of this rapid biological response should enable us to quantitatively evaluate long-lasting effects of the nuclear disaster.

What Caused Declines in Intertidal Invertebrate Populations around Fukushima Daiichi Nuclear Power Plant after the 2011 Great East Japan Earthquake, Tsunami, and Nuclear Disaster?

We discuss possible causal factors for the decline in intertidal invertebrate populations around Fukushima Daiichi Nuclear Power Plant (FDNPP) after the 2011 Great East Japan Earthquake and subsequent tsunami and nuclear disaster on the basis of existing knowledge about the effects of radionuclides and ionizing radiation on aquatic organisms. We found a gap between effects observed in the laboratory and those observed in natural aquatic environments, and discuss possible reasons why. Considering the complexity of the environment, we conclude that it is critical to evaluate the effects of ionizing radiation combined with other biotic and abiotic environmental factors, together with the life-history traits of the species examined, for realistic assessment of population-level effects.

Assessing the impact of large-scale farmland abandonment on the habitat distributions of frog species after the Fukushima nuclear accident.

Rice paddies function as wetlands; therefore, abandoned paddy fields cause a loss of habitats for aquatic species, such as amphibians. Following the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, paddy fields around the plant were abandoned and rapidly dried. To identify the impact of large-scale abandonment of paddy fields on the habitats of frogs, we investigated changes in the distributions of four frogs that breed in paddy fields using niche modeling and field surveys.

Consecutive sexual maturation observed in a rock shell population in the vicinity of the Fukushima Daiichi Nuclear Power Plant, Japan.

In 2012, after the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) that followed the Tohoku earthquake and tsunami in March 2011, no rock shell (Thais clavigera; currently recognized as Reishia clavigera; Gastropoda, Neogastropoda, Muricidae) specimens were found near the plant from Hirono to Futaba Beach (a distance of approximately 30 km). In July 2016, however, rock shells were again found to inhabit the area. From April 2017 to May 2019, we collected rock shell specimens monthly at two sites near the FDNPP (Okuma and Tomioka) and at a reference site ~ 120 km south of the FDNPP (Hiraiso).

Changes in feeding habits of the starspotted smooth-hound, Mustelus manazo, in Tokyo Bay between periods with different stock size levels.

We investigated differences in the feeding habits of the starspotted smooth-hound, Mustelus manazo, in Tokyo Bay between the mid-1990s (low stock size) and the late 2000s (high stock size). The frequency of M. manazo with empty stomachs increased from 5.

Current status of the megabenthic community in coastal Fukushima Prefecture, Japan, in the wake of the Great East Japan Earthquake.

We conducted fisheries-independent bottom-trawl surveys along the coast of Fukushima, Japan, from 2013 to 2017 to study the megabenthic community structure after the 2011 earthquake, tsunami, and nuclear disaster. Although we observed no substantial changes in biodiversity, total abundance and biomass fluctuated among years, primarily because of temporary increases in the abundance or biomass of small shrimp and squid, or variations in abundance or biomass of mid-sized fishes (i.e.

Radiocesium in seawater, sediments, and marine megabenthic species in coastal waters off Fukushima in 2012-2016, after the 2011 nuclear disaster.

In bottom-sediment samples collected in 2012 from a coastal strip (∼30 km × 120 km) off the Fukushima Daiichi Nuclear Power Plant (FDNPP), radiocesium activity concentrations were generally higher south of the FDNPP, with high activity concentration patches in the north. In periodic surveys conducted at nearshore sites during 2012-2016, no clear temporal trends were observed in radiocesium activity concentrations in seawater or bottom sediment, and activity concentrations were higher in fish than in invertebrates. During 2012-2014, radiocesium activity concentrations tended to decrease in fish, but during 2012-2013 in the south, some increases were observed.

Characterization and comparison of transcriptional activities of the retinoid X receptors by various organotin compounds in three prosobranch gastropods; Thais clavigera, Nucella lapillus and Babylonia japonica.

Two cDNAs of RXR were isolated, for the first time, from the ivory shell, Babylonia japonica, and the transcriptional activities were tested in vitro to compare with other gastropod (Thais clavigera and Nucella lapillus) RXR isoforms. The transcriptional activities of all of these RXR isoforms were significantly induced by mammalian RXR agonist, 9-cis retinoic acid (9cRA). The transcriptional activity of T.

Ontogenetic and temperature-dependent changes in tolerance to hypoxia and hydrogen sulfide during the early life stages of the Manila clam Ruditapes philippinarum.

Wind-induced upwelling of hypoxic waters containing hydrogen sulfide (HS) sometimes causes mass mortalities of aquatic organisms inhabiting coastal areas, including the hypoxia-tolerant Manila clam Ruditapes philippinarum. We examined the tolerance of Manila clam to HS under controlled laboratory conditions. Larvae and juveniles obtained by artificial fertilization or from a wild population were exposed to normoxic or to hypoxic water with or without un-ionized HS (concentrations, 0.

Organotins and new antifouling biocides in water and sediments from three Korean Special Management Sea Areas following ten years of tributyltin regulation: Contamination profiles and risk assessment.

A simultaneous monitoring study on organotins (butyltins and phenyltins) and most frequently used alternative antifouling biocides (Irgarol 1051, Diuron, Sea-Nine 211 and M1) in water and sediments (n=44) collected from three Special Management Sea Areas operated by Korean government. The lower concentration of butyltins (BTs) than that of new antifouling biocides (NEW) was found in water but the significant greater concentration of BTs than that of NEW was still found in sediments. The tributyltin (TBT) levels in water exceeded the chronic criterion to protect seawater aquatic life at several sites.

Effect of water temperature on survival of early-life stages of marbled flounder Pseudopleuronectes yokohamae in Tokyo Bay, Japan.

We investigated factors that might have disturbed the stock recovery of marbled flounder in Tokyo Bay by focusing on the early life stages. Field surveys in Tokyo Bay from 2006 to 2011 revealed that mature adult biomass increased from 2006 to 2008 and decreased thereafter. Meanwhile, larval and juvenile densities were high in 2006 and 2008 but low in other years.

Decline in intertidal biota after the 2011 Great East Japan Earthquake and Tsunami and the Fukushima nuclear disaster: field observations.

In 2011, 2012, and 2013, in the intertidal zones of eastern Japan, we investigated the ecological effects of the severe accident at the Fukushima Daiichi Nuclear Power Plant that accompanied the 2011 Great East Japan Earthquake and Tsunami. The number of intertidal species decreased significantly with decreasing distance from the power plant, and no rock shell (Thais clavigera) specimens were collected near the plant, from Hirono to Futaba Beach (a distance of approximately 30 km) in 2012. The collection of rock shell specimens at many other sites hit by the tsunami suggests that the absence of rock shells around the plant in 2012 might have been caused by the nuclear accident in 2011.

Temporal trends for inflow of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) to Tokyo Bay, Japan, estimated by a receptor-oriented approach.

We estimated inflow rates of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) to Tokyo Bay, Japan, between February 2004 and February 2011 by a receptor-oriented approach based on quarterly samplings of the bay water. Temporal trends in these inflow rates are an important basis for evaluating changes in PFOS and PFOA emissions in the Tokyo Bay catchment basin. A mixing model estimated the average concentrations of these compounds in the freshwater inflow to the bay, which were then multiplied by estimated freshwater inflow rates to obtain the inflow rates of these compounds.

Assessment of radiocesium contamination in frogs 18 months after the Fukushima Daiichi nuclear disaster.

We investigated the accumulation of radionuclides in frogs inhabiting radioactively contaminated areas around Fukushima Daiichi Nuclear Power Plant (FDNPP) to search for possible adverse effects due to radionuclides. We collected 5 frog species and soil samples in areas within and outside a 20-km radius from FDNPP in August and September 2012 and determined their radiocesium concentrations ((134)Cs and (137)Cs). There was a positive correlation between radiocesium concentrations in the soil samples and frogs, and the highest concentration in frogs was 47,278.

Molecular cloning of precursors for TEP-1 and TEP-2: The GGNG peptide-related peptides of a prosobranch gastropod, Thais clavigera.

TEP (Thais excitatory peptide)-1 and TEP-2 are molluscan counterparts of annelidan GGNG-peptides, identified in a neogastropod, Thais clavigera (Morishita et al., 2006). We have cloned two cDNAs encoding TEP-1 and TEP-2 precursor protein, respectively, by the standard molecular cloning techniques.

Disturbance of recruitment success of mantis shrimp in Tokyo Bay associated with effects of hypoxia on the early life history.

We investigated effects of severe hypoxia (dissolved oxygen <1 ml l(-1)) on recruitment of mantis shrimp Oratosquilla oratoria in Tokyo Bay. Ten-year field surveys were conducted to examine quantitative relationships in annual mean densities of larvae and juveniles, and spatial distribution of juveniles and severe hypoxia. There was no significant correlation between annual mean densities of larvae and juveniles, suggesting that mortality during larval or juvenile stages varies among years, which might have regulated abundance of young-of-the-year juveniles.

Target and screening analysis of 940 micro-pollutants in sediments in Tokyo Bay, Japan.

Urban societies are using an increasingly diverse array of chemicals, many of which ultimately end up accumulating in urban harbors, where they can act as contaminants alone or as part of a mixture. In attempt to grasp a more complete picture of anthropogenic chemicals in an urban harbor, we analyzed 940 organic chemicals in sediments in Tokyo Bay, one of the most densely populated and modernized areas in the world. For the chemical analysis, we used targeted analytical methods using a GC-MS-MS and a GC-MS-SIM, and a screening analysis using an automated identification and quantification system with a GC-MS database.

Cloning and characterization of the retinoic acid receptor-like protein in the rock shell, Thais clavigera.

The organotin compounds have a high affinity for the retinoid X receptor (RXR), which is a transcriptional factor activated by retinoids that induce imposex in gastropods. However, the molecular mechanisms underlying the regulation of RXR and its related genes in gastropods remain unclear. We isolated a retinoic acid receptor (RAR)-like cDNA (TcRAR) in the rock shell, Thais clavigera, and examined the transcriptional activity of the TcRAR protein by using all-trans retinoic acid (ATRA).

Changes in growth and reproductive traits of dragonet Callionymus valenciennei in Tokyo Bay, concurrent with decrease in stock size.

We examined changes in the growth and reproductive traits of dragonet Callionymus valenciennei concurrent with decrease in stock size in Tokyo Bay. Stock size in mid 2000s decreased to 14% of that recorded in early 1990s. The minimum standard length at which dragonet attain gonadal maturation was smaller in 2000s (4.

Development of reproductive organs in the ivory shell Babylonia japonica: observations from wild populations and laboratory-reared juveniles.

We histologically examined normal differentiation and development of genital tract and gonad in the ivory shell Babylonia japonica (Buccinidae) to determine whether the formation of male-type genitalia in imposex-exhibiting females mimics the normal development of male genitalia in prosobranch gastropods. We used a wild-caught 2-year-old specimen and laboratory-reared juveniles aged 0-24 months. Gonad differentiation was unclear before age 14 months, but progressed after 16 months.

Transfer kinetics of perfluorooctane sulfonate from water and sediment to a marine benthic fish, the marbled flounder (Pseudopleuronectes yokohamae).

The authors investigated the kinetics of transfer of perfluorooctane sulfonate (PFOS) from water, suspended sediment, and bottom sediment to a marine benthic fish, the marbled flounder (Pseudopleuronectes yokohamae). Fish were exposed in 3 treatments to PFOS in combinations of these exposure media for 28 d and then depurated for 84 d. A major part (37-66%) of PFOS in the fish was in the carcass (i.

Upregulation of hypoxia-inducible factor (HIF)-1α and HIF-2α mRNA levels in dragonet Callionymus valenciennei exposed to environmental hypoxia in Tokyo Bay.

There is an urgent need to develop reliable biomarkers of environmental hypoxia exposure in marine organisms in order to assess the ecological impacts of the marked increase in coastal hypoxia worldwide. Full-length hypoxia-inducible factor HIF-1α and HIF-2α cDNAs were cloned and characterized from dragonet Callionymus valenciennei, a representative epibenthic teleost inhabiting hypoxic areas in Tokyo Bay, to evaluate the potential utility of their transcript levels as biomarkers of environmental hypoxia exposure. HIF-1α and HIF-2α transcript levels in the livers of dragonet collected from hypoxic sites in Tokyo Bay were increased several-fold over those collected from nonhypoxic areas.