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The pH of coastal seawater varies based on several local forcings, such as water circulation, terrestrial inputs, and biological processes, and these forcings can change along with global climate change. Understanding the mechanism of pH variation in each coastal area is thus important for a realistic future projection that considers changes in these forcings. From 2020 to 2021, we performed parallel year-round observations of pH and related ocean parameters at five stations around the Japanese coast (Miyako Bay, Shizugawa Bay, Kashiwazaki Coast, Hinase Archipelago, and Ohno Strait) to understand the characteristics of short-term pH variations and their forcings. Annual variability (~1 standard deviation) of pH and aragonite saturation state (Ωara) were 0.05–0.09 and 0.25–0.29, respectively, for three areas with low anthropogenic loadings (Miyako Bay, Kashiwazaki Coast, and Shizugawa Bay), while it increased to 0.16–0.21 and 0.52–0.58, respectively, in two areas with medium anthropogenic loadings (Hinase Archipelago and Ohno Strait in Seto Inland Sea). Statistical assessment of temporal variability at various timescales revealed that most of the annual variabilities in both pH and Ωara were derived by short-term variation at a timescale of < 10 days, rather than seasonal-scale variation. Our analyses further illustrated that most of the short-term pH variation was caused by biological processes, while both thermodynamic and biological processes equally contributed to the temporal variation in Ωara. The observed results showed that short-term acidification with Ωara < 1.5 occurred occasionally in Miyako and Shizugawa Bays, while it occurred frequently in the Hinase Archipelago and Ohno Strait. Most of such short-term acidified events were related to short-term low-salinity events. Our analyses showed that the amplitude of short-term pH variation was linearly correlated with that of short-term salinity variation, and its regression coefficient at the time of high freshwater input was positively correlated with the nutrient concentration of the main river that flows into the coastal area.

Chlorophyll a (Chl a) often exhibits a maximum concentration in the subsurface layer rather that at the surface. The depth of the Chl a maximum primarily depends on the balance between light penetration from the surface and the nutrient supply from the deep ocean. However, a global map of subsurface Chl a concentrations based on observations has not been presented yet. In this study, we integrate Chl a concentration data from recent biogeochemical floats and historical ship-based (and other) observations and present global maps of subsurface Chl a concentrations with related variables. The subsurface Chl a maximum was observed globally throughout the oceans: at depths greater than 80 m in the subtropics and tropics (30∘ S to 30∘ N); in the 40–80 m depth range in the tropics, in the Southern Ocean (south of 40∘ S), and at the midlatitudes (30–40∘ N/S) in the North Pacific; and at depths of less than 40 m in the northern subarctic (north of 40∘ N). The observed maxima all lie below the mixed-layer depth for the entire year in the subtropics and tropics and during summer in the midlatitudes and the northern subarctic. The depths of the subsurface Chl a maxima are greater than those of the photosynthetically active layer in the subtropics but shallower in the tropics and midlatitudes. In the subtropics, a seasonal increase in oxygen below the mixed layer implies substantial new biological production, which corresponds to 10 % of the net primary production in that region. During El Niño, subsurface Chl a concentrations are higher in the middle and eastern equatorial Pacific but lower to the west in comparison with La Niña, a pattern which is opposite to that on the surface. The spatiotemporal variability of the Chl a concentrations described here has implications to not only for the biogeochemical cycling in the ocean but also for understanding the thermal structure and dynamics of the ocean via absorption of shortwave radiation.

Coastal warming, acidification, and deoxygenation are progressing, primarily due to the increase in anthropogenic CO2. Coastal acidification has been reported to have effects that are expected to become more severe as acidification progresses, including inhibiting formation of the shells of calcifying organisms such as shellfish. However, compared to water temperature, an indicator of coastal warming, spatiotemporal variations in acidification and deoxygenation indicators such as pH, aragonite saturation state (Ωarag), and dissolved oxygen in coastal areas of Japan have not been observed and projected. Moreover, many species of shellfish are important fisheries resources, including Pacific oyster (Crassostrea gigas). Therefore, there is concern regarding the future combined impacts of coastal warming, acidification, and deoxygenation on Pacific oyster farming, necessitating evaluation of current and future impacts to facilitate mitigation measures. We deployed continuous monitoring systems for coastal warming, acidification, and deoxygenation in the Hinase area of Okayama Prefecture and Shizugawa Bay in Miyagi Prefecture, Japan. In Hinase, the Ωarag value was often lower than the critical level of acidification for Pacific oyster larvae, although no impact of acidification on larvae was identified by microscopy examination. Oyster larvae are anticipated to be affected more seriously by the combined impacts of coastal warming and acidification, with lower pH and Ωarag values and a prolonged spawning period, which may shorten the oyster shipping period and lower the quality of oysters. No significant future impact of surface-water deoxygenation on Pacific oysters was identified. To minimize the impacts of coastal warming and acidification on Pacific oyster and related local industries, cutting CO2 emissions is mandatory, but adaptation measures such as regulation of freshwater and organic matter inflow from rivers and changes in the form of oyster farming practiced locally might also be required.

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere in a changing climate is critical to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe and synthesise data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (EFOS) are based on energy statistics and cement production data, while emissions from land-use change (ELUC), mainly deforestation, are based on land-use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly, and its growth rate (GATM) is computed from the annual changes in concentration. The ocean CO2 sink (SOCEAN) is estimated with global ocean biogeochemistry models and observation-based data-products. The terrestrial CO2 sink (SLAND) is estimated with dynamic global vegetation models. The resulting carbon budget imbalance (BIM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ. For the year 2021, EFOS increased by 5.1 % relative to 2020, with fossil emissions at 10.1 ± 0.5 GtC yr-1 (9.9 ± 0.5 GtC yr-1 when the cement carbonation sink is included), ELUC was 1.1 ± 0.7 GtC yr-1, for a total anthropogenic CO2 emission of 11.1 ± 0.8 GtC yr-1 (40.8 ± 2.9 GtCO2). Also, for 2021, GATM was 5.2 ± 0.2 GtC yr-1 (2.5 ± 0.1 ppm yr-1), SOCEAN was 2.9 ± 0.4 GtC yr-1 and SLAND was 3.5 ± 0.9 GtC yr-1, with a BIM of -0.6 GtC yr-1 (i.e. total estimated sources too low or sinks too high). The global atmospheric CO2 concentration averaged over 2021 reached 414.71 ± 0.1 ppm. Preliminary data for 2022, suggest an increase in EFOS relative to 2021 of +1.1 % (0 % to 1.7 %) globally, and atmospheric CO2 concentration reaching 417.3 ppm, more than 50 % above pre-industrial level. Overall, the mean and trend in the components of the global carbon budget are consistently estimated over the period 1959–2021, but discrepancies of up to 1 GtC yr-1 persist for the representation of annual to semi-decadal variability in CO2 fluxes. Comparison of estimates from multiple approaches and observations shows: (1) a persistent large uncertainty in the estimate of land-use changes emissions, (2) a low agreement between the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) a discrepancy between the different methods on the strength of the ocean sink over the last decade. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding of the global carbon cycle compared with previous publications of this data set (Friedlingstein et al., 2022a; Friedlingstein et al., 2020; Friedlingstein et al., 2019; Le Quéré et al., 2018b, 2018a, 2016, 2015b, 2015a, 2014, 2013). The data presented in this work are available at https://doi.org/10.18160/GCP-2022 (Friedlingstein et al., 2022b).

While multiple studies have investigated oxygen decrease in Japan Sea Proper Water (JSPW; > 300 m in depth), oxygen variation in continental slope and shelf waters (−1) by the end of this century.

In recent decades, acidification of the open ocean has shown a consistent increase. However, analysis of long-term data in coastal seawater shows that the pH is highly variable because of coastal processes and anthropogenic carbon inputs. It is therefore important to understand how anthropogenic carbon inputs and other natural or anthropogenic factors influence the temporal trends in pH in coastal seawater. Using water quality data collected at 289 monitoring sites as part of the Water Pollution Control Program, we evaluated the long-term trends of the pHinsitu in Japanese coastal seawater at ambient temperature from 1978 to 2009. We found that the annual maximum pHinsitu, which generally represents the pH of surface waters in winter, had decreased at 75 % of the sites but had increased at the remaining sites. The temporal trend in the annual minimum pHinsitu, which generally represents the pH of subsurface water in summer, also showed a similar distribution, although it was relatively difficult to interpret the trends of annual minimum pHinsitu because the sampling depths differed between the stations. The annual maximum pHinsitu decreased at an average rate of −0.0024 yr−1, with relatively large deviations (0.0042 yr−1) from the average value. Detailed analysis suggested that the decrease in pH was caused partly by warming of winter surface waters in Japanese coastal seawater. The pH, when normalized to 25 ∘C, however, showed decreasing trends, suggesting that dissolved inorganic carbon from anthropogenic sources is increasing in Japanese coastal seawater.

Chlorophyll a (Chl-a) often retains its maximum concentration not at the surface but in the subsurface layer. The depth of the Chl-a maximum primarily depends on the balance between light penetration from the surface and nutrient supply from the deep ocean. However, a global map of subsurface Chl-a concentrations based on observations has not been presented yet. In this study, we integrate Chl-a concentration data not only from recent biogeochemical floats but also from historical ship-based and other observations, and present global maps of subsurface Chl-a concentration with related variables. The subsurface Chl-a maximum deeper than the mixed layer depth was stably observed in the subtropics and tropics (30° S to 30° N), only in summer in midlatitudes (30–40° N/S), and rarely at 45–60° S of the Southern Ocean and in the northern North Atlantic (north of 45° N). The depths of the subsurface Chl-a maxima are deeper than those of the euphotic layer in the subtropics and shallower in the tropics and midlatitudes. In the subtropics, seasonal oxygen increases below the mixed layer implied substantial biological new production, which corresponds to 10 % of the net primary production there. During El Niño, the subsurface Chl-a concentration in the equatorial Pacific is higher in the middle to the east and lower in the west than that during La Niña, which is opposite that on the surface. The spatiotemporal variability of the Chl-a concentration described here would be suggestive results not only for the biogeochemical cycle in the ocean but also for the thermal structure and the dynamics of the ocean via the absorption of shortwave radiation.

Isoscapes of stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in pelagic fish and squid were generated using 1967 measured values of forage fish and squid in the Northwest Pacific Ocean. We then used generalized additive models (GAMs) to assess the explanatory variables that best predicted regional fish and squid δ13C and δ15N values. A total of 522 squid and 1445 forage fish were analyzed for δ13C and δ15N. The explanatory variables/variates used in GAM analyses were geographical parameters (longitude and latitude), body mass, season, category of organism (fish or squid), and vertical habitat. The resulting isoscapes of δ13C showed higher values in the sub-tropical region and lower values in the sub-arctic region. The isoscape patterns of δ15N were more complex; higher values were found in both tropical and temperate regions, and lower values were observed in sub-tropical and sub-arctic regions. These heterogeneities in isoscapes of δ13C and δ15N in the Northwest Pacific could be caused by productivity dynamics, ocean currents and upwelling, and the degree of atmospheric fixation of carbon and nitrogen. These new isoscapes can be used in conjunction with predator δ13C and δ15N values to evaluate movements and trophic dynamics of predatory marine animals, including tunas, billfish, sharks, seabirds, and marine mammals, in the Northwestern Pacific Ocean.

IntroductionGiven an increasing use of dipeptidyl peptidase-4 (DPP-4) inhibitors to treat patients with type 2 diabetes mellitus in the real-world setting, we conducted a prospective observational study (Japan-based Clinical Research Network for Diabetes Registry: J-BRAND Registry) to elucidate the safety and efficacy profile of long-term usage of alogliptin.Research design and methodsWe registered 5969 patients from April 2012 through September 2014, who started receiving alogliptin (group A) or other classes of oral hypoglycemic agents (OHAs; group B), and were followed for 3 years at 239 sites nationwide. Safety was the primary outcome. Symptomatic hypoglycemia, pancreatitis, skin disorders of non-extrinsic origin, severe infections, and cancer were collected as major adverse events (AEs). Efficacy assessment was the secondary outcome and included changes in hemoglobin A1c (HbA1c), fasting blood glucose, fasting insulin and urinary albumin.ResultsOf the registered, 5150 (group A: 3395 and group B: 1755) and 5096 (3358 and 1738) were included for safety and efficacy analysis, respectively. Group A patients mostly (>90%) continued to use alogliptin. In group B, biguanides were the primary agents, while DPP-4 inhibitors were added in up to ~36% of patients. The overall incidence of AEs was similar between the two groups (42.7% vs 42.2%). Kaplan-Meier analysis revealed the incidence of cancer was significantly higher in group A than in group B (7.4% vs 4.8%, p=0.040), while no significant incidence difference was observed in the individual cancer. Multivariate Cox regression analysis revealed that the imbalanced patient distribution (more elderly patients in group A than in group B), but not alogliptin usage per se, contributed to cancer development. The incidence of other major AE categories was with no between-group difference. Between-group difference was not detected, either, in the incidence of microvascular and macrovascular complications. HbA1c and fasting glucose decreased significantly at the 0.5-year visit and nearly plateaued thereafter in both groups.ConclusionsAlogliptin as a representative of DPP-4 inhibitors was safe and durably efficacious when used alone or with other OHAs for patients with type 2 diabetes in the real world setting.

This study assessed the effects of constant and diurnally fluctuating pCO2 on development and shell formation of larval abalone Haliotis discus hannai. The larvae was exposed to different pCO2 conditions; constant [450, 800, or 1200 μatm in the first experiment (Exp. I), 450 or 780 μatm in the second experiment (Exp. II)] or diurnally fluctuating pCO2 (800 ± 400 or 1200 ± 400 μatm in Exp. I, 450 ± 80, 780 ± 200 or 780 ± 400 μatm in Exp. II). Mortality, malformation rates or shell length of larval abalone were not significantly different among the 450, 800, and 800 ± 400 μatm pCO2 treatments. Meanwhile, significantly higher malformation rates and smaller shells were detected in the 1200 and 1200 ± 400 μatm pCO2 treatments than in the 450 μatm pCO2 treatment. The negative impacts were greater in the 1200 ± 400 μatm than in the 1200 μatm. Shell length and malformation rate of larval abalone were related with aragonite saturation state (Ω-aragonite) in experimental seawater, and greatly changed around 1.1 of Ω-aragonite which corresponded to 1000–1300 μatm pCO2. These results indicate that there is a pCO2 threshold associated with Ω-aragonite in the seawater, and that pCO2 fluctuations produce additional negative impacts on abalone when above the threshold. Clear relationships were detected between abalone fitness and the integrated pCO2 value over the threshold, indicating that the effects of OA on development and shell formation of larval abalone can be determined by intensity and time of exposure to pCO2 over the threshold.

Marine cladocerans are secondary producers in marine neritic ecosystems. To investigate the population dynamics and species-specific habitats of marine cladocerans in the Sea of Japan, marine cladoceran abundance was evaluated in the southern Sea of Japan and the East China Sea-Kuroshio using three mesh-size (0.06, 0.10, and 0.33 mm) plankton nets at several depths (n = 4674) over two decades from 1997 to 2018. We observed seven out of eight species, including Penilia avirostris, Evadne nordmanni, E. spinifera, Pseudevadne tergestina, and Pleopis schmackeri, from > 10% of samples, and Pleopis polyphemoides and Podon leuckartii from

A continuous survey examined short-term variations in the zooplankton community and physical ocean environment from the northeastern Izu Islands to Boso Peninsula in Japan. High copepod abundance and small upwellings in the surface layer and salinity minimum layer in the subsurface were observed on the north side of coastal fronts in the westernmost transect, moving southward as the Kuroshio Current left the Boso Peninsula. Thus, the salinity minimum layer might be a key factor forming upwelling and the fronts, leading to large abundance of coastal copepods off the northeastern Izu Islands. A community structure analysis of calanoid copepods revealed an intermediate belt assemblage between coastal and offshore (Kuroshio) assemblages. Copepod abundance was remarkably low and Ctenocalanus vanus dominated (nearly 37%) in the intermediate belt zone, indicating that C. vanus has a relatively high tolerance to adverse environments for calanoid copepods. As the Kuroshio Current left the Boso Peninsula, the coastal assemblage expanded in the same direction, and the intermediate belt assemblage off the northeastern Izu Islands disappeared. The largest population of Calanus sinicus was found along the two western transects off the northeastern Izu Islands (>1000 m depth), which was assumed to be transported from Sagami Bay and advanced southwestward while growing from copepodite stages CIII to CV. Larvae of C. sinicus would be an important food for fish larvae in addition to Paracalanus parvus s.l., the numerically dominant species in the coastal assemblage, and C. vanus under the adverse conditions for coastal copepods.

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 (

In recent decades, acidification of the open ocean has shown consistent increases. However, analysis of long-term data in coastal waters shows that the pH is highly variable because of coastal processes and anthropogenic carbon inputs. It is therefore important to understand how anthropogenic carbon inputs and other natural or anthropogenic factors influence the temporal trends in pH in coastal waters. Using water quality data collected at 1481 monitoring sites as part of the Water Pollution Control Program, we determined the long-term trends in pH in Japanese coastal waters at ambient temperature from 1978 to 2009. We found that pH decreased (i.e., acidification) at between 70 % and 75 % of the sites and increased (i.e., basification) at between 25 % and 30 % of the sites. The rate of decrease varied seasonally and was, on average, −0.0014 yr−1 in summer and −0.0024 yr−1 in winter, but with relatively large deviations from these average values. While the overall trends reflect acidification, watershed processes might also have contributed to the large variations in pH in coastal waters. The seasonal variation in the average pH trends reflects variability in warming trends, while regional differences in pH trends are partly related to heterotrophic water processes induced by nutrient loadings.

A strong oxygen deficient layer is located in the upper layer of the tropical Pacific Ocean and at deeper depths in the North Pacific. Processes related to climate change (upper ocean warming, reduced ventilation) are expected to change ocean oxygen and nutrient inventories. In most ocean basins, a decrease in oxygen (‘deoxygenation’) and an increase of nutrients has been observed in subsurface layers. Deoxygenation trends are not linear and there could be other influences on oxygen and nutrient trends and variability. Here oxygen and nutrient time series since 1950 in the Pacific Ocean were investigated at 50 to 300 m depth, as this layer provides critical pelagic habitat for biological communities. In addition to trends related to ocean warming the oxygen and nutrient trends show a strong influence of the Pacific Decadal Oscillation (PDO) in the tropical and the eastern Pacific, and the North Pacific Gyre Oscillation (NPGO) especially in the North Pacific. In the Oyashio Region the PDO, the NPGO, the North Pacific Index (NPI) and a 18.6 year nodal tidal cycle overlay the long-term trend. In most regions oxygen increases and nutrients decrease in the 50 to 300 m layer during the negative PDO phase, with opposite trends during the positive PDO phase. The PDO index encapsulates the major mode of surface temperature variability in the Pacific and oxygen and nutrients trends throughout the basin can be described in the context of the PDO phases. An influence of the subtropical-tropical cell in the tropical Pacific cannot be proven with the available data. El Niño and La Niña years often influence the oxygen and nutrient distribution during the event in the eastern tropical Pacific, but do not have a multi-year influence on the trends.

The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "living data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here: doi:10.3334/CDIAC/OTG.SOCAT_V3_GRID.

We present the spatial distributions and temporal changes of the long-term variability of surface nutrient concentrations in the North Pacific by using nutrient samples collected by volunteer ships and research vessels from 1961 to 2012. Nutrient samples are optimally interpolated onto 1° × 1° monthly grid boxes. When the Pacific Decadal Oscillation is in its positive phase, nutrient concentrations in the western North Pacific are significantly higher than the climatological means, and those in the eastern North Pacific are significantly lower. When the North Pacific Gyre Oscillation is in its positive phase, nutrient concentrations in the subarctic are significantly higher than the climatological means. The trends of phosphate and silicate averaged over the North Pacific are −0.012 ± 0.005 µmol l−1 decade−1 and −0.38 ± 0.13 µmol l−1 decade−1, whereas the nitrate trend is not significant (0.01 ± 0.13 µmol l−1 decade−1).

We studied seasonal and regional change in vertical distribution and DVM patterns of four euphausiid species (Euphausia pacifica, Thysanoessa inspinata, Thysanoessa longipes, and Tessarabrachion oculatum) from two years of surveys using MOCNESS above 1500 m depth across a transect in 3 regions of the northwestern (NW) Pacific, off east of Japan; Oyashio, Kuroshio, and Oyashio–Kuroshio Mixed Water Regions (MWR). The four euphausiid species exhibited a regional change in vertical distribution, i.e., slightly deeper in the MWR and much deeper in the Kuroshio region than in the Oyashio region. They found in higher and wider temperature ranges in the MWR than in the Oyashio region, which demonstrated that the four species were able to adapt to different temperatures in different regions. In the MWR and Oyashio regions, E. pacifica is a surface migrant (differences between day and night mean median depths, D-N, were ca. 300 m) and T. oculatum is a moderate subsurface migrant that performs short DVM in the upper mesopelagic zone (D-N ca. 100 m). The other two morphologically similar Thysanoessa species (T. inspinata and T. longipes) segregated vertically between E. pacifica and T. oculatum at night in the Oyashio region, suggesting vertical habitat partitioning with the former two species but not with themselves. However, a seasonal pattern was observed in the vertical distribution and DVM of T. longipes in the Oyashio region. It behaves as a surface migrant in May, whereas most of individuals were found in the mesopelagic layer in September. In contrast, T. inspinata did not exhibit a clear DVM throughout the year (i.e., a moderate subsurface migrant). This seasonal difference might be a strategy to minimize competition between related species. Among the four species, only E. pacifica was found in higher temperatures at night than during the daytime, and the highest temperatures at the median depth varied among species (from 7.5 °C to 13.7 °C) although the lowest temperature did not vary greatly (from 1.0 °C to 1.8 °C), which indicates high temperatures act as a limiting factor as opposed to low temperatures. Furthermore, the integrated chlorophyll a values exhibited significant negative correlation with median depths of only E. pacifica at night. These results indicate a strategy which makes E. pacifica the dominant species in the area, that is, it has a trade-off of long migrations and a warmer environment that accelerates metabolism, in return for obtaining a food-rich environment.

To better understand habitats of larval Pacific bluefin tuna (PBT; Thunnus orientalis) in the nursery grounds, the vertical distribution of larval PBT was collected using a 1-m2 Tucker trawl and a 3.14-m2 ring net at depths of 0, 10, 20, and 30 m during the spawning seasons of 2016 and 2017. Most of the larvae in the Japan Sea (756 of 938 individuals) were collected from the surface layer using a ring net, while similar numbers were collected from 0 to 20 m depth in the Nansei area. The temperature at ≥20 m depths in the Japan Sea was cooler than the optima temperature, and the thermocline was steep at 10 m depth, and the cold subsurface water was suggested to make the PBT larvae aggregate near the surface. A weak ontogenetic and diel migration was observed; the body size at 10 m depth during the day and 0 m at night were significantly larger than those at 0 m during the day in the Japan Sea. These results suggested that some small larvae sink to 10 m and/or large larvae move to the surface at night. Our results showed that the larval PBT habitat is strongly controlled by water temperature, and that global warming would have a positive effect on PBT larvae in the Japan Sea, which was evidenced by the higher density of PBT larvae after 2010 compared to before 1990.

We used an eddy-permitting three-dimensional ocean ecosystem model and applied it in the western North Pacific to understand the seasonal variations and horizontal distributions of the air–sea CO2 flux and difference in the partial pressure between sea water and the atmosphere (∆pCO2). The high-resolution model reproduced the observed zonal belt of strong CO2 uptake in the mid-latitude (30–45°N) western North Pacific including the Kuroshio extension and mixed water regions, which was difficult to show in previous coarse-resolution models. The East Asian winter monsoon, an important phenomenon in the western North Pacific, affects the seasonal CO2 air–sea gas exchange with a high (low) gas transfer coefficient in winter (summer). In the subtropical region, ∆pCO2 is negative in winter and positive in summer as a result of the temperature effect. Combination of seasonal change in gas transfer coefficient with ∆pCO2 suppresses CO2 release in the subtropical region, and vice versa in the subarctic region (i.e., suppresses CO2 uptake). That is, the East Asian winter monsoon in the western North Pacific contributes to the reduction of the annual CO2 flux through the seasonal change in the gas transfer coefficient, leading to an overall annual CO2 uptake in the subtropical region and CO2 release in the subarctic region.

From April 2011 to January 2012, seasonal variation of the aragonite saturation state (Ωar) was observed for the first time in Tokyo Bay, in order to understand the current state of ocean acidification in a highly eutrophicated bay in Japan. Ωar in the bay ranged between 1.55 and 5.12, much greater than observed in offshore waters. At the surface, Ωar was high during summer as a result of photosynthesis with some conflicting effect of freshwater input. At the bottom, Ωar was low during summer due to remineralization of organic matter. Based on an assumption that our observations represent current conditions in Tokyo Bay, it is estimated that the emission of anthropogenic CO2 has already decreased Ωar by 0.6 since the preindustrial period and will further decrease by 1.0–1.6 by the end of this century if emission of CO2 is continued at a high level [representative concentration pathway (RCP) 8.5 scenario]. With other conditions remaining the same, bottom waters of the bay will reach seasonal aragonite undersaturation by 2060–2070. However, because coastal regions have a large interannual variability, we need further observations to evaluate our estimations and future predictions presented here. Nevertheless, it should be safe to say that the larger seasonal variation in Ω causes the Tokyo Bay to reach aragonite undersaturation earlier than offshore regions and such conditions have negative consequences on the variety of calcifying organisms living in Tokyo Bay. Ocean acidification could thus give an additional stress to the ecosystem of the bay, which is now suffering from eutrophication and hypoxia.

Levels of radiocesium (134Cs + 137Cs) contamination in lake water, bottom sediment, plankton, and fish were investigated in three geographically separated lakes in Fukushima Prefecture (Lake Hayama, Lake Akimoto, and Lake Tagokura) between June 2012 and November 2013. Levels of contamination differed among the three lakes, with the highest levels of each measured component in Lake Hayama, followed by Lake Akimoto, and the least contamination in Lake Tagokura. Among the lakes, the magnitude of contamination decreased with distance from the Fukushima Dai-ichi Nuclear Power Plant. Mean radiocesium concentrations were higher in piscivorous fish than in other fish, possibly reflecting differences in trophic level. The radiocesium concentrations in some fish species decreased significantly by 33–65 % during the period between 2012 and 2013. Radiocesium concentrations of the lake water, bottom sediment, plankton, and fish were significantly correlated with surface soil radiocesium content near lake sites.

Ayu Plecoglossus altivelis, a herbivorous fish, is an important fishery resource and key component of the foodweb in many Japanese streams. Radionuclide contamination of this species is likely transferred to higher trophic levels, include humans, in the food chain. After the Fukushima accident in March 2011, ayu were exposed to highly contaminated silt while feeding on algae attached to the riverbed stones. To understand the route by which herbivorous fish are exposed to radionuclides, the activity concentrations of sum of (134)Cs and (137)Cs (radiocesium) were analyzed in riverbed samples (algae and silt) and in the internal organs and the muscle of ayu in five river systems in the Fukushima Prefecture between summer 2011 and autumn 2013. Although there was a positive correlation between the radiocesium activity concentrations in the muscle and the internal organs of ayu, the median activity concentration in the muscle was much lower than those in the internal organs. The activity concentrations of radiocesium in the riverbed samples and the internal organs and the muscle of ayu were correlated with contamination levels in soil samples taken from the watershed upstream of the sample sites. The results of the generalized linear mixed models suggest that the activity concentrations in both the internal organs and the muscle of ayu declined over time. Additionally, the activity concentrations in the internal organs were correlated with those in the riverbed samples that were collected around the same time as the ayu. The activity concentrations in the muscle were correlated with ayu body size. Our results suggest that ayu ingest (134)Cs and (137)Cs while grazing silt and algae from the riverbed, and a part of the (134)Cs and (137)Cs is assimilated into the muscle of the fish.

Increase in seawater pCO2 and the corresponding decrease in pH caused by the increasing atmospheric CO2 concentration (i.e., ocean acidification) may affect organic matter production by phytoplankton communities. Organic matter production forms the basis of marine food webs and plays a crucial role in oceanic CO2 uptake through the biological carbon pump, and hence will potentially affect future marine ecosystem dynamics. However, responses of organic matter production in open ocean plankton ecosystems to CO2 increase have not been fully examined. We conducted on-deck microcosm experiments using high nutrient, low chlorophyll (HNLC) waters in the western subarctic Pacific and oceanic Bering Sea basin in summer 2008 and 2009, respectively, to examine the impacts of elevated CO2 on particulate and dissolved organic matter (i.e., POM and DOM, respectively) production. Iron deficient natural plankton communities were incubated for 7–14 days under multiple CO2 levels with and without iron enrichments (hereafter +Fe and −Fe treatments, respectively). By combining with our previous experiments at two sites, we created a comprehensive dataset on responses of organic matter production to CO2 increase during macronutrient replete conditions in HNLC waters. Significant differences in net particulate organic carbon production among CO2 treatments were observed only in the −Fe treatments, whereas that in net dissolved organic carbon production were mainly observed in the +Fe treatments, suggesting that CO2 may affect different processes depending on the Fe nutritional status. However, impacts of CO2 were not consistent among experiments and were much smaller than the consistent positive effects of Fe enrichment. In contrast, no significant differences among the CO2 treatments were observed for organic carbon partitioning into POM and DOM, and carbon to nitrogen ratio of net produced POM. We conclude that CO2 does not play a primary role, but could have secondary effects on controlling the organic matter production under macronutrient replete conditions in HNLC waters. On the other hand, in a nutrient-depleted, declining phase of the phytoplankton bloom induced by Fe enrichment, carbon overconsumption was found in an experiment with elevated CO2 conditions suggesting that CO2 impacts might become more significant in such environments.

The Fukushima Dai-ichi nuclear power plant (FNPP) accident that followed the Great East Japan Earthquake in 2011 resulted in the release of enormous quantities of anthropogenic radionuclides, especially radioactive cesium (134Cs and 137Cs) into the ocean off the east coast of Japan. FNPP-derived radioactive Cs may have consequently accumulated within marine food webs via seawater intake and predator–prey interactions. We provide evidence of the temporal variability in 134Cs and 137Cs concentrations in seawater and zooplankton samples collected in coastal waters off Joban-Sanriku, in Sendai Bay, and in the Oyashio region between June 2011 and December 2013. In Sendai Bay, seawater 134Cs and 137Cs concentrations exceeded 1 Bq/kg in June 2011 and rapidly decreased during the study period. 134Cs and 137Cs concentrations in zooplankton were also high in June 2011, up to 23 Bq/kg-wet and also decreased during the study period, although at a slower rate than seawater 134Cs and 137Cs concentrations. Regarding 137Cs concentrations, the difference in the rate of decrease between seawater and zooplankton resulted in a high apparent concentration ratio (aCR) for zooplankton. The observed relation between 137Cs in seawater and the aCR of zooplankton were good indicators of the progress of 137Cs contamination in zooplankton from the beginning of the FNPP accident to the restoration phase.

This study assessed the effects of constant and diurnally fluctuating pCO

Pacific bluefin tuna (Thunnus orientalis; PBFT) is a highly migratory species, with some individuals migrating between the western Pacific Ocean (WPO) and eastern Pacific Ocean (EPO). In this study, we used stable isotope analysis to identify PBFT that had recently undergone westward transoceanic migration on the Sea of Japan. A total of 155 PBFT individuals were examined. Their ages ranged from 2 to 17 years, with most individuals being 2–7 years of age. Individuals from each year class were classified as WPO residents or recent EPO migrants using cluster analysis of δ15N values. Individuals aged 2, 6, and over 7 years had unimodal distributions of δ15N values, while individuals aged 3, 4 and 5 years showed a bimodal distribution with high- and low-δ15N groups. Due to the overall higher baseline of δ15N values in the EPO, high δ15N individuals were considered to represent PBFT that had migrated from the EPO. Though individuals aged 6 and over 7 years showed unimodal distributions in the cluster analysis, discriminant analysis indicated that these PBFT also included some migrants from the EPO. We preliminary estimated the percentages of migrants and residents in the Sea of Japan. Such information can improve stock assessments models for PBFT and contribute to the sustainable stock management of this species.

We elucidated multiyear variations of sea surface dissolved inorganic carbon (DIC) concentrations in the North Pacific from 2002 to 2008 by using monthly DIC maps derived from partial pressure CO2 observations. The Pacific Decadal Oscillation (PDO) was related to an east-west seesaw pattern in the North Pacific DIC anomaly field. In the western North Pacific, DIC concentrations were relatively high from mid-2002 to mid-2005 and low after late 2007 compared with climatological values, and in the eastern North Pacific the opposite change was observed. Changes of the forcing factors associated with the PDO could explain the DIC east-west seesaw pattern: horizontal advection, freshwater fluxes and vertical mixing in most regions, CO2 fluxes south of 40°N, and biological production in the subarctic.

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates and consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuels and industry (EFF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (ELUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (GATM) is computed from the annual changes in concentration. The mean ocean CO2 sink (SOCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (SLAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models. We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as ±1σ, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006–2015), EFF was 9.3 ± 0.5 GtC yr−1, ELUC 1.0 ± 0.5 GtC yr−1, GATM 4.5 ± 0.1 GtC yr−1, SOCEAN 2.6 ± 0.5 GtC yr−1, and SLAND 3.1 ± 0.9 GtC yr−1. For year 2015 alone, the growth in EFF was approximately zero and emissions remained at 9.9 ± 0.5 GtC yr−1, showing a slowdown in growth of these emissions compared to the average growth of 1.8 % yr−1 that took place during 2006–2015. Also, for 2015, ELUC was 1.3 ± 0.5 GtC yr−1, GATM was 6.3 ± 0.2 GtC yr−1, SOCEAN was 3.0 ± 0.5 GtC yr−1, and SLAND was 1.9 ± 0.9 GtC yr−1. GATM was higher in 2015 compared to the past decade (2006–2015), reflecting a smaller SLAND for that year. The global atmospheric CO2 concentration reached 399.4 ± 0.1 ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in EFF with +0.2 % (range of −1.0 to +1.8 %) based on national emissions projections for China and USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. In spite of the low growth of EFF in 2016, the growth rate in atmospheric CO2 concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (SLAND) in response to El Niño conditions of 2015–2016. From this projection of EFF and assumed constant ELUC for 2016, cumulative emissions of CO2 will reach 565 ± 55 GtC (2075 ± 205 GtCO2) for 1870–2016, about 75 % from EFF and 25 % from ELUC. This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Quéré et al., 2015b, a, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2016).