Akira Hoshika's research while affiliated with National Institute of Advanced Industrial Science and Technology and other places

Publications (39)

Article
The drift numerical simulation model of the Seto Inland Sea with 0.5' mesh was constructed to search for problem of marine litter in the sea. The particles assumed to the floating litter were released from 13 rivers in these models and were traced for 30 days. As a result, the drift route, the arrival place, and the arrival time of the floating lit...
Article
Fly-ash particles comprising spheroidal carbonaceous particles (SCP) and inorganic ash spheres (IAS), produced from industrial fossil-fuel combustion, are found in lake sediments throughout the world where they provide an historical record of atmospheric pollutant deposition. These particles have been widely used to assess the temporal and spatial...
Article
Full-text available
The contribution of benthic microalgal production has been compared both within and outside a coastal eelgrass (Zostera marina L.) meadow. Carbon and nitrogen stable isotope ratios of suspended particulate organic matter (POM), epiphytic and epilithic organic matter (EOM), leaves of Z. marina (inside the meadow only) and two secondary consumer spec...
Article
Sedimental cores from the Gulf of Thailand were collected by core sampler for examination of δ13C and δ15N and organic carbon and nitrogen contents. The δ13C of surface (0–2 cm) sediments from the whole Gulf gave approximately the same value (−21‰) except only one station at the upper Gulf, with an enriched value of −18‰. The δ15N value of sediment...
Article
Benthic microalgal production has been clarified to be comparable to water column production in coastal shallow water ecosystems. The present study examined carbon transport pathways from microphytobenthos to predators in a food web of an exposed hard bottom shore in the Seto Inland Sea of Japan in winter, noting the intermediary role of suspension...
Article
Field surveys of the bottom turbid layer were undertaken from the Changjiang estuary to the mid-continental slope area in the East China Sea to study the bottom turbid layer formation process and ascertain the role of material transport. A dramatic development of bottom turbid layers in the continental shelf area of the East China Sea was observed...
Article
The relative importance of benthic and pelagic primary production for demersal fish and some invertebrates in the western Seto Inland Sea of Japan was examined using carbon and nitrogen stable isotope analyses. A few fishes, such as juvenile black rockfish Sebastes inermis and large Japanese anchovies Engraulis japonicus, had isotopic carbon signat...
Article
The relative importance of benthic and pelagic primary production for demersal fish and some invertebrates in the western Seto Inland Sea of Japan was examined Using carbon and nitrogen stable isotope analyses. A few fishes. such as juvenile black rockfish Sebastes inermis and large Japanese anchovies Engraulis japonicus, had isotopic carbon signat...
Article
The relative importance of benthic and pelagic primary production for demersal fish and some invertebrates in the western Seto Inland Sea of Japan was examined using carbon and nitrogen stable isotope analyses. A few fishes, such as juvenile black rockfish Sebastes inermis and large Japanese anchovies Engraulis japonicus, had isotopic carbon signat...
Article
大阪湾と紀伊水道における水質観測結果に基づいて, 大阪湾における懸濁・溶存態物質の収支をボックスモデルにより解析した。その結果, 夏季, 冬季ともに表層では懸濁物質(TSM), 懸濁態有機炭素(POC), 懸濁態有機窒素(PON)および懸濁態リン(PP)の生成量は分解を上回り, 中層と底層では分解が生成を上回っていた。表層におけるPOC, PONおよびPPの生成量の夏季と冬季の平均はそれぞれ1, 300, 175および27td-1であり, 河川等からの負荷量と比較してそれぞれ約10, 8および16倍大きい。表層で多量の懸濁態有機物が生成されるにもかかわらず, これらのうち約60%は大阪湾内で分解され, 湾外への流出は20~30%であった。一方, 溶存態無機窒素(DIN)と溶存態無機リン(DI...
Article
The distribution of carbon and nitrogen stable isotope ratios in macroalgae in Hiroshima Bay was examined seasonally from June, 1999 to June, 2000. A total of 52 species including 109 samples were collected from the eutrophic northern area and the mesotrophic central area of the bay. The macroalgae were mainly distributed from -23.0 to -11.0 ‰ in δ...
Article
Tomogashima Strait, which is an entrance of Osaka Bay, is a very important area for material transport because a large volume of pollutant-rich water in Osaka Bay is transported through this strait. We have investigated the cross sectional structures of current and material fluxes at Tomogashima Strait, Osaka Bay. Tidal current and residual flow pa...
Article
Carbon and nitrogen stable isotope ratios (13C and 15N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The 13C and 15N of surface sediments in the estuary of the Yodo River were less th...
Article
Trend of eutrophication and magnitude of marine-derived organic matter contributing to organic pollution were investigated in the Osaka Bay, Seto Inland Sea, which is semi-closed coastal bay surrounded by highly developed industrial areas and has been subjected to the effect of human activities. Average standing stocks of total nitrogen and total p...
Article
Conductivity-temperature-turbidity surveys were conducted along ten transects from 31.5° to around 27°N across the shelf edge zone in May 1995 (Leg 1; 10-16 May and Leg 2; 19-26 May). During Leg 1 survey, a well-developed turbid layer extended from the shelf to the shelf edge at the central transects located from 28° to 29°N. On the contrary, the d...
Article
In order to estimate the fluxes of total suspended matter (TSM), particulate organic carbon (POC), organic nitrogen (PON) and phosphorus (PP) transported through the boundary between the inner part and central part of Osaka Bay, temporal variations of current velocity and concentration of the TSM, POC, PON and PP were measured at three locations al...
Article
Seasonal variation in the transport of suspended matter across the East China Sea is investigated with the use of results of field observations and diagnostic numerical experiments. Suspended matter is transported from the shelf edge to the inner shelf in summer and from the inner shelf to the shelf edge in autumn and winter due to the vertical cir...
Article
As a method for collecting suspended substances and polluted sediment particles in sea water, the effectiveness of dredging a concave on the sea floor has been investigated by researchers. In this study, particulate materials were collected by using a polyvinylchloride cylindrical vessel (50cm in diameter, 70cm in depth) which was set on the sea fl...
Article
A metrologied survey and observation of the sedimentation distribution and the structure of the particulate matters (suspended particles) in the Osaka Bay has been made. Relatively high sedimentation rates were noticed around the central part of the bay rather than in the inner part of the bay where a large amount of the particulate matters are inc...
Article
The strong tidal current (tidal jet) in straits generates tidal vortices with a scale of several kilometers. The role of the vortices in material transport was investigated in the Neko Seto Sea, located in the western part of the Seto Inland Sea of Japan. A clockwise vortex with a diameter of about 0.8 km was observed in Nigata Bay (lying between t...
Article
The settling velocity of suspended particles in the bottom layers of Osaka Bay and Etauchi Bay was studied as a function of the particle diameter by using the developed in situ settling apparatus with a camera. In Osaka Bay, the settling velocity in winter varied in the range of 0.02 to 1.5 cm sec-1, depending upon the particle diameter, but not up...
Article
To discuss the geochemical and environmental behaviors of heavy metals in the Seto Inland Sea which is the largest semi-closed coastal sea in Japan, (1) distributions of heavy metals concerning pollution were examined and (2) mass balances of Zn and Cu were studied by applying a simple box model. Increase in heavy metal contents of core sediments a...
Article
The beam attenuation coefficient, organic carbon (POC) and organic nitrogen (PON) contents of suspended materials in Etauchi Bay, which has little inflow of river water as well as very weak tidal current (maximum speed: 6.5cmsec−1), were measured as a function of depth for all seasons to understand a seasonal variation of bottom turbidity layer. In...
Article
Iodide- and total-iodine (Iodide+iodate) in seawaters of Osaka Bay were determined by an electrolytic concentration on glassy carbon electrode and detection with a polished Ag3SI electrode. The standard deviation of this method was within about 2% The concentrations of iodide-iodine in seawaters of Osaka Bay were in the range from 0.10 to 0.30μM an...
Article
To discuss the geochemical and environmental behavior of heavy metals in the Seto Inland Sea, the largest semi-enclosed coastal sea in Japan, mass balances of Cu and Zn were studied by application of a simple box model using sedimentation rates and heavy metal contents of core sediments. In 1980, total sedimentary loads of Cu and Zn over the whole...
Conference Paper
A monitoring system of water quality in the benthic boundary layer has been designed and built to investigate process of oxygen consumption in bottom layer of the Seto Inland Sea. The system consists of three instruments. The first instrument has been developed to operate on the bottom floor and makes continuous measurement of the vertical distribu...
Article
The metal load into sediments and the change in the sedimentary environment of Osaka Bay in the Seto Inland Sea have been studied through geochemical analysis of core sediments, using both Pb-210 dating and a selective chemical leaching technique. Analytical results from a 6-m core of sediment show that copper and zinc pollution started in the late...
Article
Sedimentation rates in ten sediment cores from Hiroshima Bay in the Seto Inland Sea of Japan were determined with the |2210|0Pb technique, and heavy metals were analyzed. The sedimentation rates vary from 0.18 to 0.33 g cm|2-2|0 yr|2-1|0. The highest sedimentation rates were observed in the northern part of the bay at the mouth of Ota River, while...
Article
Sedimentation rates were determined with the210Pb technique in six sediment cores from Harima Nada (Harima Sound), Seto Inland Sea. The rate of deposition varies from 0.11 g cm–2y–1 in the northern part to 0.33 g cm–2 y–1 in the southern part of the basin. A marked increase in copper and zinc content was observed above a depth in the core correspon...
Article
Vertical and horizontal distributions of manganese in Harima Sound (Harima Nada, Seto Inland Sea) were measured in August and December 1979. High concentrations of dissolved and particulate manganese were found in bottom waters in August, suggesting that the bottom enrichment is probably due to the diffusion of dissolved manganese out of the sedime...
Article
Around the thermocline, difference in the depth of the maximum concentration between particulate manganese and iron was observed above the basin located at the south-western corner of the Beppu Bay, along with the remarkable difference in pH and Eh.
Article
From July to November, the thermocline which has strong temperature gradient (0.7‡C m−1) is formed in the bottom water of Beppu Bay, and it prevents the downward mixing of surface water. This has caused the bottom water of the basin to become depleted in oxygen, and in November the bottom water below about 60 m depth becomes anoxic. Accordingly man...
Article
This paper gives the results of determination of cadmium, lead and copper in interstitial water of the coastal sediment, Seto Inland Sea, Japan by using anodic stripping voltammetry. An aliquot of 4–5 ml interstitial water separated from 30–70 ml of sediment is used for the simultaneous determination of ionic cadmium, lead and copper. No significan...

Citations

... Similarly, Doiuchi et al. (2011) showed a similar trend between phytoplankton (223.3 to 219.7‰) and benthic algae (microalgae: 219.0 to 212.4‰; macroalgae: 220.1 to 211.3‰) for IA of the Kii Channel. Inshore anchovy could utilize larvae of benthic organisms such as bivalves and decapods more frequently than offshore anchovy (Takai et al., 2003;Tanaka et al., 2008). Elevated d 13 C values in IA might reflect a carbon source derived from benthic primary producers in addition to phytoplankton. ...
... In contrast to Tokyo Bay, we did not detect a positive correlation between the PFCA concentrations and the orgasmic matter concentration in the sediment from the Seto Inland Sea (r = 0.496, p < 0.06). However, we observed a significant positive correlation between the PFCA concentrations in the sediment samples and the sedimentation rates [25][26][27][28][29] near the sampling stations (r = 0.935, p < 0.00003; Fig. 4) except for Kii Channel (Stns. K-0 and K-1; because no sedimentation rate data were available, we could not evaluate the relationship at K-0 and K-1). ...
... All samples of sardine foods (Foods A-1 and A-2) had similar δ 15 N values (Table 1); this suggests that there were no significant isotopic differences between the two batches of food. Wild sardines feed on phytoplankton and zooplankton (Kawasaki and Kumagai 1984), which generally have lower δ 15 N values than consumer species (e.g., Takai and Mishima 2002;Aita et al. 2011). Therefore, the observed isotopic increase in sardine vertebral sections should correctly reflect the dietary shift from plankton to artificial diet, and this result suggests that sardine vertebrae record temporal isotopic chronologies. ...
... To validate this expectation, stable isotope ratios of stomach samples and field samples were compared statistically. Finally, we obtained data from prior studies for potential food sources (Takai et al. 2001, Hatase et al. 2002. ...
... The reported f of settling biogenic and lithogenics particles is~0.1 mm and~0.01 mm, respectively, based on in situ camera observations of settling particles (Tanimoto and Hoshika, 1994). ...
... This horizon is the same as that of the increase of TS content in core MOB2. Hoshika et al. (1988) reported temporal profiles of the Zn and Cu concentrations in two cores from the inner and central parts of Beppu Bay, respectively. According to that study, the Cu and Zn concentrations started to increase in the early 1920s. ...
... Unlike Fe, Mn fluxes measured in FCR, regardless of method, are comparable to fluxes measured in other studies (Table 2). Our Mn fluxes from chambers and mass balance are in the range reported by others (Belzile et al., 1996;Davison and Woof, 1984;Kawana et al., 1980;Sakata, 1985;Yagi, 1996); the only studies with substantially higher Mn fluxes were from Rostherne Mere, England (Davison and Woof, 1984) and Beppu Bay, Japan (Kawana et al., 1980). ...
... Ds(ƒÂC / ƒÂX) (1) where 0 is the porosity of the sediment, Ds is the diffusion coefficient, C is the phosphate concentration in the intersti-tial water, and X is the depth of the sediment. ...
... The DO consumption rates in Hiuchi-nada were from 0.032 to 0.040 g m -2 h -1 . Ochi and Takeoka (1986) and Hoshika et al. (1989) measured in situ DO consumption rates using a bell-jar type chamber in the eastern part of Hiuchi-nada. Their results were 0.02 and 0.03 g m -2 h -1 on average, respectively, which are slightly lower but still comparable to ours. ...
... This disagrees with the distribution pattern found in this study, and the observed fluxes were slightly higher than those in this study period in general; Iseki et al. (2003) reported that the maximum total dry mass fluxes were over 300 mg m –2 d –1 in January 1994 from an 810 m trap. Regarding the factors controlling particulate fluxes and their variations, Iseki et al. (2003) suggested that seasonal events, such as local climate and oceanographic conditions in shelf water, could have a significant influence on the strong seasonality and the seaward bottom flow might have caused the larger offshore transport of the particulate matter in the bottom turbid layer (Okamura et al., 1997; Hoshika et al., 2003). Using the results of field observations and diagnostic numerical experiments, Yanagi et al. (1996) reported that the seasonal variation in the vertical circulation pattern from 1993 to 1994 was mainly induced by the monsoon wind, influencing the transport of suspended matter across the shelf edge, and showed that suspended matter was transported from the shelf edge to the inner shelf in summer and from the inner shelf to the shelf edge in autumn and winter. ...