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Ocean surface acidification due to increasing atmospheric CO2 concentration is currently attracting much attention. Coccolithophores distribute widely across the world's oceans and represent a carbon sink containing about 100 million tonnes of carbon. For this reason, there is concern about dissolution of their shells, which are made of calcium carbonate, due to decreasing pH. In this study, intracellular calcification, photosynthesis, and mass transport through biomembranes of Emiliania huxleyi were modelled numerically for understanding biological response in calcifying organisms. Unknown parameters were optimised by a generic algorithm to match existing experimental results. The model showed that the production of calcium carbonate rather than its dissolution is promoted under an acidified environment. Calcite remains at saturation levels in a coccolith even when it is below saturation levels in the external seawater. Furthermore, a coccolith can dissolve even in water where calcite saturation exceeds 1, because the saturation may be below the threshold level locally around the cell membrane. The present model also showed that the different calcification rates of E. huxleyi with respect to rising CO2 concentrations reported in the literature are due to differences in experimental conditions; in particular, how the CO2 concentration is matched. Lastly, the model was able to reproduce differences in calcification rates among coccolithophore species. The above biochemical-kinetic model was then incorporated into an ecosystem model, and the behaviour of coccolithophores in the ecosystem and the influence of increases in CO2 concentration on water quality were simulated and validated by comparison with existing experimental results. The model also suggests that increased CO2 concentration could lead to an increase in the biomass ratio of coccolithophores to diatoms at high CO2 concentrations, particularly in oligotrophic environments, and to a consequent decrease in pH due to calcium dissolution.

This study explored the physiological responses of the coral Pocillopora damicornis to high nitrate concentrations and thermal stresses. The expression of heat shock proteins Hsp60 and Hsp32, Symbiodiniaceae density, Chl a concentration, Fv/Fm, H2O2 scavenging, and caspase 3 activity varied during 60 h incubations at 28 °C or 32 °C, ambient or high nitrate (~10 μM) concentrations, and their combinations. In combined stresses, corals showed a rapid and high oxidation level negatively affecting the Symbiodiniaceae density and Chl a concentration at 12 h, followed by caspase 3 and Hsps upregulations that induced apoptosis, bleaching and tissue detachment. Corals under thermal stress showed the highest oxidation and upregulation of Hsps and caspase 3 resulting in coral discoloration. High nitrate treatment alone did not seriously affect the coral function. Results showed that combined stress treatment severely affected coral physiology and, judging from the condition of detached tissues, these corals might have lower chances to recover.

We describe a strategy to identify stress-responsive genes in corals by means of high-coverage cDNA expression profiling (HiCEP). In this study, the effects of thermal and chemical (DCMU and TBT-Cl) stresses on Acropora tenuis juvenile polyps were examined, and 19 genes were identified as stress-responsive genes. Of these, seven had sequences significantly similar to sequences of known proteins. We quantified the expression levels of these seven using real-time PCR. In corals, the genes encoding heat shock protein 90, calreticulin, methionine adenosyltransferase, and aquaglyceroporin showed differential stress-related expression patterns. In the endosymbiotic algae associated with the corals, genes coding for DnaJ-like protein and chloroplast light-harvesting protein were identified as stress-responsive genes. The only gene showing increased expression in response to all three stresses (thermal and both chemical stresses) was the coral gene coding for the oxidative stress-responsive protein, suggesting that oxidative stress generally occurs in each stress-exposed polyp.

We examined the production and partitioning of organic carbon under different inorganic nitrogen concentrations and phytoplankton composition by incubating unaltered seawater collected from 10, 100, 400 and 700 m depths off Suruga Bay, Japan. Particulate organic carbon (POC) accounted for 60–112% of net accumulated total organic carbon (TOC) during exponential growth and blooms of phytoplankton in all incubations regardless of the concentrations of nutrients and the forms of dissolved inorganic nitrogen (DIN) as well as the composition and size of phytoplankton. After the blooms of phytoplankton, microzooplankton (mainly ciliates) (>20 μm) increased rapidly in majority of incubations. This suggests that a large fraction of new production may also be transferred to higher trophic levels rather than immediately exported. After the depletion of initial DIN, accumulation of both POC and dissolved organic carbon (DOC) increased. DOC accounted for major fraction of TOC in most of the incubations. Continued accumulation of high C/N organic matter implies that recycling through the food web is not necessarily the dominant fate of organic carbon produced under low DIN condition but rather that a major fraction of the organic carbon is exported to deep water through sinking.

Methyl viologen (MV) causes severe oxidative stress by generating superoxide in the photosystem. The marine Chlamydomonas strain W80 is highly tolerant to MV (inhibitory concentration 50% [IC₅₀]=110 μM), and another marine Chlamydomonas strain HS5 shows also relatively a high tolerance (IC₅₀=12 μM). These two marine strains and a freshwater Chlamydomonas reinhardtii, which is highly sensitive to MV (IC₅₀=0.03 μM), were compared with respect to their reactive oxygen species (ROS) eliminating enzymes (superoxide dismutase, catalase, glutathione peroxidase, and ascorbate peroxidase), intracellular free amino acids, and antioxidant activities of the cell extracts. The marked difference between the marine Chlamydomonas strains and C. reinhardtii is the much higher (more than 5 fold) ascorbate peroxidase (APX) activity in the marine strains. The marine strains also kept the high APX activities (more than 100% of non-stressed condition) under the MV stressed condition, while the APX activity in C. reinhardtii was significantly decreased (36% of non-stressed condition) under the stressed condition, indicating that APX activity potentially contributes to the oxidative stress tolerance in Chlamydomonas. In addition, the levels of intracellular free proline, which is supposed to ameliorate oxidative stress, were several tens of times higher in the marine Chlamydomonas strains than in C. reinhardtii.

This ten-year study examined the morphological, physiological, and ecological characteristics of coral growth anomalies on Acropora cytherea on Amuro Island, Okinawa, Japan. The objectives of the study were to assess whether the growth anomalies, identified as diffuse disruptions on the skeleton: (i) were more prevalent on large colonies than on small colonies, (ii) were more common near the center of the colonies than peripherally, (iii) affected colony growth and mortality, and (iv) affected coral-colony fecundity and photosynthetic capacity. We hypothesized that the growth anomalies were signs of the onset of aging. The growth anomalies were more prevalent on colonies >2 m diameter, and were concentrated near the central (older) portions of the colonies. The growth anomalies were also associated with reduced productivity and dysfunctional gametogenesis. Still, the growth anomalies did not appear to affect colony survival. The contact experiments showed that the growth anomalies were not contagious, and were most likely a sign of aging that was exacerbated by thermal stress.

Studies in epipelagic waters report higher heterotrophic microbial biomass in the productive high latitudes than in the oligotrophic low latitudes; however, biogeographical data are scarce in the deep ocean. To examine the hypothesis that the observed latitudinal differences in heterotrophic microbial biomass in the epipelagic zone also occur at depth, abundance and biomass of heterotrophic prokaryotes, nanoflagellates (HNF), and ciliates were determined at depths of 5-5000 m in the central Pacific between August and September of 2005. Heterotrophic microbial biomass increased from the tropical to the subarctic region over the full water column, with latitudinal differences in prokaryotic biomass increasing from 2.3-fold in the epipelagic zone to 4.4-fold in the bathypelagic zone. However, the latitudinal difference in HNF and ciliate biomass decreased with depth. In the mesopelagic zone, the vertical attenuation rate of prokaryotic abundance, which was calculated as the linear regression slope of log-log plot of abundance versus depth, ranged from -0.55 to -1.26 and was more pronounced (steeper slope) in the lower latitudes. In contrast, the vertical attenuation rate of HNF in the mesopelagic zone (-1.06 to -1.27) did not differ with latitude. In the subarctic, the attenuation rate of HNF was 1.7 times steeper than for prokaryotes. These results suggest the accumulation of prokaryotes in the deep subarctic Pacific, possibly due to low grazing pressure. Although the vertical attenuation rate of ciliates was steepest in the bathypelagic zone, HNF abundance did not further decrease at depths below 1000 m, except for at 2000 m where HNF was lowest across the study area. Ciliate abundance ranged 0.3-0.8 cells l -1 at 4000 m, and were below the detection limit ( < 0.1 cells l -1 ) at 5000 m. To our knowledge, this study presents the first data for ciliates below 2000 m.

Sarcoidosis is a systemic granulomatous disease of unknown etiology. Propionibacterium acnes is the only microorganism so far isolated from sarcoid lesions. To examine whether P. acnes isolates from sarcoid tissues differ from those obtained from non-sarcoid tissues, we studied cell invasiveness, serotype, and polymorphisms of the P. acnes trigger factor protein and the two invasion-associated proteins (named PAmce and PAp60) in 35 P. acnes isolates from sarcoid lymph nodes and 127 isolates from non-sarcoid tissues. Most of the serotype I isolates (79/112; 71%), but none of the serotype II isolates (0/50) were cell-invasive. Two prominent types of trigger factors, one with and one without a 15 amino acid-residue deletion, corresponded to serotype II and serotype I, respectively. Non-invasive isolates had genomic mutations that caused more than one amino acid change in either the PAmce or PAp60 gene, with four exceptional isolates. P. acnes was finally classified into nine isotypes, and isolates obtained from sarcoid and non-sarcoid tissue did not differ. Although the finding did not link P. acnes to sarcoidosis, the present study clarified the cell invasiveness of P. acnes and the close correlation of cell invasiveness to the serotype and genotype of the two invasion-associated P. acnes genes.

Incubation of unaltered deep-sea water and grazing experiment of nano- and micro- protozooplankton during incubation of deep-sea water were carried out to quantitatively characterize the planktonic structures of lower-trophic organisms and clarify the trophic pathways and controlling mechanisms involved. Phytoplankton biomass increased to 637 mg as carbon weight in a 500-l tank on Day 7 and was dominant in the planktonic structure of lower-trophic organisms. Nitrates in the incubation water was depleted after Day 7 and phytoplankton biomass decreased rapidly. On the other hand, bacteria, heterotrophic nano-flagellates and ciliates increased toward the end of incubation and were dominant in the later days of incubation. In grazing experiments on microbial organisms, bacterivory is more important for the carbon pathway in microbial food webs than herbivory when phytoplankton biomass is less than that of bacteria (low P/B conditions), while herbivory is more important than bacterivory when phytoplankton biomass is more than that of bacteria (high P/B conditions). Deep-sea water exhibited high phytoplankton productivity due to inherent high nutrients values. After depletion of nutrients, phytoplankton decreased (due also to enhanced nano- and micro-zooplankton grazing) and microbial organisms dominated. Thus, nutrients in the incubation water control the planktonic structure of lower-trophic organisms.

Helicobacter pylori has been considered to be non-invasive and to rarely infiltrate the gastric mucosa, even though there is an active Th1 immune response in the lamina propria of the H. pylori-infected stomach. To elucidate whether H. pylori invades the lamina propria and translocates to the gastric lymph nodes, we examined H. pylori in formalin-fixed and paraffin-embedded tissue sections of stomach and gastric lymph nodes obtained from 51 cancer patients using real-time PCR and immunohistochemistry (IHC) with a novel anti-H. pylori monoclonal antibody that recognizes lipopolysaccharides. Fresh gastric lymph nodes were used to culture for H. pylori. In 46 patients with H. pylori in the stomach, the bacterium was found in the lymph nodes from 21 patients by culture, 37 patients by PCR, and 29 patients by IHC. H. pylori captured by macrophages was found in the lamina propria of 39 patients. In the lymph nodes, the bacterium was found in many macrophages and a few interdigitating dendritic cells at the paracortical areas. H. pylori was also found in the intracellular canaliculi of parietal cells in 21 patients, but intracytoplasmic invasion into gastric epithelial cells was not identified. When compared to the commercially available anti-H. pylori antibodies, the novel antibody showed the highest sensitivity to detect H. pylori-positive macrophages, whereas no difference was found for H. pylori in the mucous layer. The H. pylori-positive macrophages in the lamina propria correlated with chronic gastritis as well as translocation of such cells to the lymph nodes. These results suggest that H. pylori-induced gastric epithelial damage allows the bacteria to invade the lamina propria and translocate to the gastric lymph nodes, which may chronically stimulate the immune system. The bacteria captured by macrophages, whether remaining alive or not, may contribute to the induction and development of H. pylori-induced chronic gastritis.

Effects of nutrients on the size and composition of phytoplankton and the resulting changes in ecosystem structure were investigated using incubations of unaltered deep-sea waters from 400 m and 700 m depths of Suruga Bay Japan. This new approach allowed us to observe the succession of phytoplankton communities from conditions of high to low nitrogen availability and explore the effects of N source and availability on the composition and size of diatoms under low grazing pressure. Diatoms dominated the phytoplankton biomass throughout the duration of experiments in both incubations. However, among diatoms, the genus Thalassiosira dominated the abundance and biomass when nutrients were replete, and the genus Chaetoceros dominated the abundance and biomass when nitrate became depleted. Our results show that diatoms can dominate other phytoplankton groups not only under nutrient replete conditions, but also (particularly for Chaetoceros ) under low concentrations of recycled nitrogen if silica and phosphate are not deficient. Diatoms 15 μm dominated the biomass in the 400 m incubations during the formation of blooms under nitrate-replete conditions. After nitrate depletion, diatoms > 15 μm dominated the biomass in both incubations. Our results showed that availability of N determined the composition of diatoms if Si and P are not deficient. However, for size the results showed that N source and availability did not determine the size of phytoplankton. Our results also showed that the molar ratio of Si:N uptake was

We examined the flows of nitrogen in two batch incubations of plankton assemblages under controlled conditions, using mesopelagic seawater from different depths. Observations included concentrations of nutrients, organic matter (particulate and dissolved) and plankton (biomass by species). Because nitrogen flows were not observed directly (as is generally the case), we examined them using a multi-element ecosystem model developed to simulate these experiments. Dynamic changes in the observed bulk POC/PON ratio (C/N ratio of particulate organic matter, POM) were consistent with a quota model for phytoplankton. To relate these changes to the regeneration of nitrogen, we included such a quota model and all major planktonic groups observed. By assimilating the data (all observations of carbon and nitrogen concentrations, including living carbon biomasses) into the model using the Monte Carlo Markov Chain, we accurately simulated the changes in bulk POC/PON ratio and its difference between incubations. Changes in phytoplankton composition dominated the changes in bulk POC/PON ratio. Bacteria dominated the regeneration of nitrogen in both incubations, and changes in bacterial regeneration strongly affected the bulk POC/PON ratio. After nitrate depletion, gross nitrogen regeneration varied inversely with observed POC/PON ratio and was constrained by this ratio. Thus, we have demonstrated a powerful new approach to constraining the flows of nutrients through ecosystems. Our results suggest that simultaneous observations of POC and PON could place an additional constraint on the supply of inorganic nitrogen in models of the oligotrophic ocean.

Vertical and seasonal characteristics of biogenic silica (BSi) dissolution in seawater were investigated by multiple dissolution experiments using seawater collected from surface and mesopelagic layers in Suruga Bay during the period 2002–2004. The dissolution rate coefficients calculated based on temporal changes of BSi concentration varied with the season of sample collection. They ranged from 0.023–0.057 day − 1 for surface samples and 0.0018–0.0025 day − 1 for mesopelagic samples for temperatures approaching in situ conditions. Experiments at various temperatures confirmed that BSi dissolution depends on temperature in natural seawater. Dissolution rate coefficient (day − 1 ) of BSi correlated significantly with temperature (°C), and Q 10 was 2.6. Addition of bioavailable organic matter to low-bioactivity seawater enhanced the protease activity and abundance of bacteria, and increased BSi dissolution rate by a factor of 1.4–2.0. There is clear evidence that BSi dissolution is accelerated by bacterial activity and potentially limited by bioavailable organic matter in natural seawater. Dissolution rates and total decreases of BSi concentration were lower during experiments using mesopelagic samples than in those using surface samples. This suggests that dissolution of BSi varies with depth and that BSi in the mesopelagic water is more resistant to the dissolution than that in the surface water. This lower dissolution rate was caused by lower temperature and lower bacterial activity due to less bioavailable organic matter in mesopelagic water. Our results provide a mechanistic understanding of variations in silica cycling within the seasonally and vertically differing marine environment.

The concentration of dissolved organic carbon (DOC) was measured every few months from September 2000 through October 2001 at a coastal location in the center of Suruga Bay, Japan (34°51′N, 138°38′E). Water samples were collected three times per day (midday, night and predawn). DOC concentrations ranged from 91.3 to 45.2 μM C on the surface to 100 m depth. Diel variation in DOC concentrations, among the three sampling times, was greater in the upper 20 m, with a maximum difference of 21.7 μM C in July 2001, and reflected in diel DOC inventory variations from the surface to 50 m. Diel variations were controlled by both physical and biological factors. DOC concentrations were significantly correlated with potential density in the deeper layers (100–1000 m), indicating that the distribution of DOC concentrations in the deeper layer was mainly due to mixing. Most DOC concentrations in the upper layer (0–50 m) did not display the same relationship as in the deeper layer. Using the relationship with potential density at 100–1000 m, the DOC concentration in the upper layer, due simply to mixing, was calculated. The difference between the calculated and observed DOC was used to estimate biological contribution. The biological contributions to the DOC inventory in the upper layer (0–50 m) were found greatly in November 2000 and April 2001. This indicates that excess DOC accumulated, by biological processes, in the upper layer during these periods. In November 2000, the excess DOC in the inventory was constant throughout the sampling days (0.36–0.37 mol C m −2 ), whereas diel variations of DOC in the vertical profile were large and contrary to the variation between 10 and 20 m. This suggests that the excess DOC was contributed biologically during daytime in the uppermost layer and reached to the 50 m depth by deeper mixing. As a result, the inventory appeared to be stable over a day because of the compensating effects of DOC production and consumption throughout 50 m. In contrast, in spring and summer, there was a distinct diel inventory decrease in the nighttime, with apparent rates ranging from −0.61 to −0.35 μM C h −1 . It is probable that the DOC, which accumulated during the daytime, was mostly labile, with a turnover time of a few hours. The results indicate that the dynamics of diel DOC variations varied seasonally, and suggest that these variations need to be considered when estimating seasonal DOC pools in the coastal ocean.

Sulfonated polysulfone (SPS) was synthesized from polysulfone resin using sulfuric anhydride–triethyl phosphate complex. The SPS was dissolved in N-methyl-2-pyrrolidone (NMP) using LiNO3 as a swelling agent. The resultant SPS dope was casted on a glass plate. An optimum ratio of SPS, NMP and LiNO3 was 1:5:0.2 for making an UF membrane. The solvent was evaporated for 30 min, at 338 K, and an ultrafiltration membrane was obtained by gelation in an ice-cold bath. The ceramic/SPS composite membrane was prepared by the following original procedure. First, the pores of the ceramic support were plugged with chitosan suspension at a pH over 6. The SPS dope was thinly coated on the membrane surface, and then the membrane was gelled in an ice-cold bath under pH 6. The chitosan suspension plugged in the pores was removed because the chitosan became soluble under pH 6. Thus, the composite membrane having negatively charged layer was obtained without plugging the ceramic support pores. The composite membrane showed a high pure water flux of 39.5×10−6 m3 m−2 s−1 at an applied pressure of 100 kPa and a molecular weight cut-off of 20 000.

Separation of ingredients in bonito extract was studied by a composite UF membrane of ceramic/sulfonated polysulfone (SPS). The bonito extract mainly contained inosine-5′-monophosphate (IMP), glutamic acid as a tasty ingredient and hypoxanthine, histidine as a putrefaction ingredient. The composite membrane showed a high rejection against negatively charged IMP, but permeated non-charged hypoxanthine. This is because of the negatively charged repulsion between the membrane and the solute. The permeation of amino acid could be controlled using the difference in isoelectric points of amino acids themselves. When the amino acid solution was filtrated by the composite membrane at pH 7, glutamic acid was rejected and no histidine was rejected. The charges of composite membrane were found to have an effect on the separation of ingredients in bonito extract. The composite membrane was stable within a wide pH range from 3 to 9, and had a thermal durability under 353 K.

A new methodology is proposed for the evaluation of metabolic parameters in coral reef ecosystems using a simple model which combines the metabolic activity with a simplified water flow system. The concentration time profile resulting from running the model for DO are compared with continuously observed data taken at a site in Miyako Island and the metabolic rates are obtained by fitting the model to the data using a four parameter optimization routine. The model yields an excellent fit to the observed data (r > 0.9) using a set of easily obtained flow and tidal information. It is concluded thus that the factors governing concentration changes of biologically mediated substrates are sufficiently simulated in the model and mass fluxes can be predicted with accuracy between the coral reef ecosystem and its interfaces with the ocean and the atmosphere.

Biological studies were carried out in Bora Bay, Miyako Island, near Okinawa Japan, with the object to understand the structure and physiology of a coral reef ecosystem, with especial emphasis on the carbon cycle and CO2 fixation. Food web of the coral reef ecosystem at Bora Bay shows some remarkable patterns with cyanobacteria, epiphytic microalgae, sea weed and zooxanthellae as primary producers rather than phytoplankton. The importance of the microbial loop as an organic source and the rapid decomposition and recycling rates is another pattern to be considered.

Fluorescence and dissolved organic carbon (DOC) measurements of porewaters from the Santa Barbara Basin, the Guaymas Basin, and the upper sections of the Nankai Trough suggest that ultraviolet fluorescence ([lambda][sub ex] = 325 nm, [lambda][sub em] = 450 nm) may be used as a first order estimate of DOC in anoxic marine porewaters. The majority of porewater organic carbon appears to be fluorescent, while a constant [approximately]1 mM DOC, probably the low molecular weight compounds, is not fluorescent. These data are consistent with a model in which low molecular weight compounds dissolved in porewater act as the common intermediate between labile sedimentary organic matter and remineralization or polymerization products. Fluorescence may also be used to sensitively estimate benthic DOC fluxes to the overlying water column. Results from the Santa Barbara Basin, if representative of global anoxic oceanic regions, indicate that DOC release from anoxic sediments is not a major source of oceanic DOC when compared to internal recycling rates, but may be comparable to external input or permanent removal processes. 36 refs., 3 figs.

A direct comparison is presented here between dissolved organic carbon (DOC) analyses done with the historical routine wet chemical oxidation method (persulfate oxidation), the high temperature catalytic oxidation method of Sugimura and Suzuki (MRI instrument), and a commercial high temperature combustion analyzer (Shimadzu instrument). The sample set used for the comparison included stations in a tidal urban river, the salinity gradient of an estuary, and continental shelf and slope waters, including those to a depth of 2000 m. Both high temperature combustion methods measured considerably more DOC (1.5 to 3.5 times) in the coastal waters than did the conventional persulfate method. In the fresh water and estuary, the commercial instrument measured only slightly higher values than did the conventional method, while the MRI instrument measured almost twice the concentration. Throughout all the environments, the MRI instrument measured about twice the concentration measured by the commercial instrument. An inverse linear correlation can be demonstrated between DOC and apparent oxygen utilization with data from each of the methods, but it is argued that this does not necessarily imply ‘oceanographic consistency’.

The high-temperature catalytic oxidation (HTCO) method for the determination of dissolved organic carbon in seawater, reported by Sugimura and Suzuki (1988, Marine Chemistry, 24, 105–131) has been improved to provide more valid data on the levels of dissolved organic carbon (DOC). The improvements are as follows. (1) An open-close valve, made from an alloy of iron, molybdenum, nickel and chromium and without a silicone septum, is used as the injection port. (2) Copper oxide and sulfix (mixture of AgO and CoO) are packed with a 3% platinum (Pt) catalyst into the combustion tube for the complete elimination of halogenated and sulfur compounds. (3) The top of the catalyst is covered with Pt gauze to prevent the Pt catalyst from flying upwards. (4) A glass water-trap, containing phosphoric acid and silver nitrate in solution, is connected just below the outlet of the combustion tube. (5) A high-sensitivity, infra-red gas analyser (Beckman model 880) is used. The blank value for the system is checked using water prepared by passage through the improved HTCO system. The total blank value (system blank plus water blank) ranges from 15 to 30 μM C. Of the total blank volume, the blank value for the system which was examined using water collected from the HTCO system, was less than 3 μM C. The greatest contributions to the blank value in this machine are made by the organic matter originally present in deionized water. The oxidation efficiency of the catalyst with different levels of Pt was examined for measurements of DOC. Although there is little difference in detected concentrations of DOC from the surface to deep waters with levels of 1.5, 3 and 5% Pt in the catalyst, the alumina impregnated with higher levels of Pt is much better for the complete oxidation of the DOC in seawater. The size of the combustion tube, the quality of the catalyst and the uniform distribution of the furnace temperature are key elements in determining the oxidative capacity of the system. It is also important to prevent backflushing just after the injection of the sample and to prevent the catalyst from moving in the combustion tube for the accurate measurement of DOC in seawater.

A method is described for the rapid, precise determination of non-volatile dissolved organic carbon in seawater in concentrations between 0 and 2000 μM. The oxidation is carried out on a platinum catalyst at 680 °C under an oxygen atmosphere after the sample has been freed of inorganic carbon, and the concentration of the CO 2 generated is measured with a non-dispersive IR gas analyzer. The determination can be carried out on board ship with a precision of ±2% using a sample volume of 200 μl. The results obtained using this method are of a much higher value than those obtained using persulfate oxidation methods. The molecular weight dependency of the results clearly indiates that the above discrepancy is caused by the low oxidation efficiency of the persulfate oxidation method against high-polymer organic matter dissolved in seawater. The results reveal that the concentration of dissolved organic carbon in surface water is about 300 μM and decreases with depth. An examination of molecular weight distribution indicates that the concentration of high-polymer organic carbon decreases rapidly from surface to deeper layers, with molecular weight ranging from 1.8 x 10 3 to 6 x 10 4 Dalton. It is noted that there is an inverse correlation between the concentration of dissolved organic carbon and apparent oxygen utilization (AOU). Frozen or acidified preservation of unfiltered samples does not give reliable results. An essential requirement for dissolved carbon analysis is membrane filtration just after sampling and real-time analysis on board. Because of the well-defined principle of the oxidation process, its reliability, the ease of sample handling and of the analytical procedure on board or in the land laboratory, and the consistency of the oceanographic parameters, this method is much more suitable for the analysis of marine dissolved organic carbon than the methods used previously.

Dissolved and particulate forms of mercury in seawater were determined. To avoid errors due to adsorption, total mercury was collected on XAD-2 resin after converting inorganic mercury to oxinate immediately after sampling. The organic mercury was trapped directly on XAD-2 resin. Both total and organic mercury adsorbed on XAD-2 resin were finally reduced to metallic mercury, which was determined by the cold vapor AAS method. In the temperature zone in the western North Pacific, total mercury is 14 ng l−1 in surface waters and 6 ng l−1 between 500 and 5,000 m. Organic and particulate mercury are 7 ng l−1 in surface waters and 2 ng l−1 between 500 and 5,000 m. Particulate forms are 3 to 10% of the total. Organic mercury comprises one-third to a half of the total. The molecular weight of organic mercury compounds was determined to be about 9 × 103, indicating its proteinaceous nature.

A detailed examination of a high-temperature catalytic oxidation method for liquid samples in the analysis of total nitrogen dissolved in seawater is reported. The nitrogenous compounds in liquid samples are oxidized on a platinum catalyzer at 680°C under oxygen atmosphere and the generated NO 2 is absorbed into a chromogenic reagent, followed by a spectrophotometric determination. The results of this method are much higher than those of wet oxidation methods. Molecular size dependency of the results clearly indicates that the above discrepancy is caused by the low oxidation capacity of the wet oxidation method against high-polymer organic matter dissolved in seawater. The results revealed that the concentration of total nitrogen in seawater is nearly constant from surface to bottom, ranging from 30 to 40 μM 1 −1 , which organic nitrogen concentration higher in the surface layer, and a rapid decrease with depth. An examination of molecular size distribution indicates that the concentration of high-polymer organic nitrogen decreases rapidly from surface to deeper layers, with molecular sizes ranging from 5 × 10 3 to 3 × 10 4 . Because of the well-defined principle of the oxidation process, its reliability, ease of sample handling and of analytical procedure on board or in the land laboratory, the present method is much more suitable for the marine analytical chemistry of total and organic nitrogen than the other previous methods.