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This study examines long-term ocean pH data to evaluate ocean acidification (OA) trends at two coastal research institutions located on the Sea of Japan and the Pacific Ocean. These laboratories are located away from the influences of large rivers and major industrial activity. Measurements were performed daily for the past 30 years (1980s–2010s). The average annual ocean pH for both sites showed generally negative trends. These trends were – 0.0032 and – 0.0068 year–1(p

We evaluated the influence of radiocesium (137Cs) desorbed from riverine particles on the export flux of dissolved 137Cs from rivers to the marine environment, where it may accumulate and become concentrated in marine biota. The samples were collected from stations along the Abukuma (December 2013), Kuji (November 2013), Naka (November 2013), and Tone (October 2013) rivers, in the catchments of which large quantities of radionuclides from the Fukushima Dai-ichi Nuclear Power Plant (FNPP) accident were deposited. We estimated the extent of the desorbed fraction from riverine particles by conducting a particle–seawater partitioning and desorption experiment in which sieved particles ( 1000 Bq/kg-dry) to the marine environment, thereby increasing the contribution of desorption to the export flux of dissolved 137Cs. These results show that reactive particulate Cs (i.e., the desorbable fraction) must be taken into account when estimating the radiocesium fluxes from rivers to coastal regions near the FNPP.

The filtration rate and thermal effects on the rate were evaluated in various marine bivalves. 1) The filtration rates by a clam population (F, l · m-2 · h-1) estimated using the following equation were compared with Pseudocardium sachalinensis in Hamanaka Bay, Hokkaido and Ruditapes philippinarum in Banzu tidal flat, Tokyo Bay.F=Σmn=1fn · RT · RS · Pnwhere ; fn, filtration rate of a clam with Ln mm (mean shell length of divided size class) examined under the experimental conditions ; RT, correction coefficient for fn at field temperature T (°C) ; RS, correction coefficient for fn at field salinity S (psu), Pn ; clam density (no. · m-2) of 15 size classes in P. sachalinensis and 7 size classes in R. philippinarum ; m, number of size classes. Filtration rate and effects of body size, temperature and salinity on the filtration rate were examined using the clam collected from each study sites. Monthly changes of temperature, salinity and clam density were investigated in Hamanaka Bay, and were evaluated from analysis of available data in Tokyo Bay, 2) The individual filtration rate corrected for body size and temperature was compared between 4 bivalve species, P. sachalinensis, R. philippinarum, Mytilus galloprovincialis, and Perna viridis. 3) Thermal effects on the filtration rate were examined in 8 bivalve species, including Mactra chinensis, Meretrix lamarcki, M. lusoria, and Mytilus coruscus.Following are major findings ; 1) The contribution of the 2 year-old population to the eatimated filtration rate was dominant in P. sachalinensis (65%) and R. philippinarum (58-78%). Following contributions were for the 3 (19%), 4 (8%), 1 (5%), and over 5 year-old (3%) in P. sachalinensis and over 3 (14-22%), and 1 year-old (8-20%) in R. philippinarum. In the case of P. sachalinensis, a irregular occurrence of dominant year class may be major factor affecting on the filtration.2) The estimated filtration rates (l · indiv.-1 · h-1) of 30mm individual at 15°C were as follows : M. galloprovincialis (2.5), R. philippinarum (1.5), P. sachalinensis (1.3), and P. viridis (0.64).3) The temperature considered to be optimum for filtration was 20°C for P. sachalinensis, M. lamarcki and M. lusoria, 25°C for M. chinensis, R. philippinarum and M. galloprovincialis, 27.5°C for M. coruscus, and 32.5°C for P. viridis.

Assuming negligible production of pseudofaeces, the amount of food filtered by the clam is equal to the amount of food ingested. The ingestion rate estimated as nitrogen per 1 m2 per h (F) was given in the following equation : F=Σ7n=1(Fn·RT·Rs·Pn)·Nwhere ; Fn, filtration rate of a clam at L mm shell length at 15°C and 35 psu ; RT, correction coefficient for Fn at T °C ; Rs, correction coefficient for Fn at S psu ; Pn, clam density of 7 size classes and N, concentration of suspended particulate nitrogen (PN). L was given for the mean shell length of each size class. Filtration rate and effects of body size, temperature and salinity on the filtration rate were examined using the clam collected from Banzu tidal flat. Monthly changes of temperature, salinity, concentration of PN and clam density for the tidal flat were evaluated by analysis of available data. PN was calculated from Chl-a concentration and reported PN : Chl-a ratio.The estimated ingestion rate was maximum at 300 mg-N·m-2·h-1 in August, and minimum at 19 mg-N·m-2·h-1 in February. From analysis of the results, it is suggested that both temperature and PN concentration affect significantly the seasonal changes of the rate, however, salinity has no detectable effect on them in Banzu tidal flat.

Ozonation of seawater produces residual oxidants which do not occur in fresh water. Most of them are bromine compounds, such as HBrO. In this study, the acute toxicity of these ozone-produced oxidants (OPO) to eggs and larvae of Japanese whiting, Sillago japonica, was tested under static-flow conditions of water with a temperature of 21.6 ?? 23.1°C, salinity 33.4 ?? 34.4‰, and pH 8.2 ?? 8.3. In analysis of the results, initial OPO concentrations measured as total residual chlorine were given importance since OPO disappeared gradually through contact with eggs or larvae. Based on the initial OPO concentration and normal survival rate, LC50's were estimated as 0.18mgC1/l (after 38h) and 0.23mgC1/l (after 24h) for eggs and larvae, respectively. Eggs were found to delay hatching. Many eggs exposed to near sublethal OPO stayed unhatched beyond the expected hatching time. After that, the death of these eggs was observed.