Measuring system of carbon dioxide concentration (pCO₂) in seawater is described. Newly developed instrument consists of an infrared gas analyzer (NDIR), an equilibrator, a carrier gas generator and a processing signal generator. The present instrument is designed to measure the carbon dioxide concentration of carrier gas which passed through the CO₂ equilibrator. The gas circuit of the NDIR is opened to the atmosphere to maintain the carrier gas line at a barometric pressure. Sample seawater of 150ml is enough to determine pCO₂. The present instrument can measure pCO₂ every 20min. The measuring error in pCO₂ is within 2ppmv (coefficient of variance: ca. 0.6%). This denotes that the present instrument is adequate to measure pCO₂ under field conditions.

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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 incessantly supplied from the Yodo River, one of the largest rivers in the Kansai District in Japan. From the estimation of mass balance for particulate matters in the bay, it is explained that 77% of the total yearly sedimental load is comprised of the particulate matters supplied by non-stationary phenomena including floods. It is imagined that the sedimentation rate is governed by such a large amount of the particulate matters and also imagined that the distribution of the sedimentation is likewise governed by an tidal current upon the behavior of river-forced estuarine plumes, which is remarkably different from a steady state tidal current. Very few difference of the organic carbons and heavy metal elements is exhibited in the total sedimental load in the central part of the bay or in the western seacoast district where the concentration of these elements is not so high and in the head of the bay where the concentration is very high. That is to say, it is indicated that these elements loaded in the bottom of the Osaka Bay spread in the whole area of the bay and are accumulated as sediments. With these facts, there is a possibility that erroneous judgment will be made when the transportation mechanism of the matters is considered. It is implied that the information concerning the sedimentation rate should concurrently be considered.

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In marine ecosystems, a substantial fraction of primary production passes through the dissolved organic matter (DOM) → bacteria → protozoa pathway. However, little is known about the mechanism (s) of the production of DOM. We examined whether or not heterotrophic flagellates release DOM. Our experiments revealed that flagellates release both monomeric labile DOM (e.g. dissolved free amino acids) and colloidal particles as a result of egestion of incompletely digested or unassimilated prey materials. "Micro fecal pellets" produced by flagellates appeared to be colloidal "liposomes" composed of prey bacterial membranes, flagellate digestive enzymes and probably other DOM from bacteria. We suggest that the release of DOM by flagellates has substantial implications for several important biogeochemical processes including ocean food webs, formation of refractory DOM, and sinking particle fluxes.

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