Kengo Kurata

Nutrients adsorption from seawater by new porous carrier made from zeolitized fly ash and slag.

This study investigated the adsorption and precipitation of phosphate by blast furnace slag (BFS) separately. In order to evaluate the adsorption capacity of BFS, BFS was treated before its use by acid. The authors aim to develop a new porous carrier to adsorb simultaneously ammonium and phosphate from seawater under eutrophic conditions. The current paper deals with a promising new approach to improve the utilization of some industrial solid wastes such as BFS and zeolite synthesized from fly ash [ZFA(Fe)] by their solidification to cylindrical porous carriers using a hydrothermal hot-pressing (HHP) method. Attempts to produce porous carriers using an arranged HHP method with different porosities (24%, 40% and 52% (v/v)) were carried out. Physical properties of carriers such as porosity, compressive strength and height have been investigated. Laboratory studies showed strong evidence that the porous carrier was very selective towards phosphate and ammonium. The results demonstrated the role of porosity in enhancing phosphate and ammonium adsorption by the increase of the surface area per weight. The estimates of the parameters and the correlation coefficients according to the Freundlich equations revealed that adsorption was related to the porosity of carriers and phosphate and ammonium were adsorbed well on the carriers having large porosity. The results suggested that developing carrier with high porosity was a promising way to enhance nutrients adsorption.

Relationship between macrobenthos and physical habitat characters in tidal flat in eastern Seto Inland Sea, Japan.

The investigations were carried out at 6 tidal flats located on the eastern part of the Seto Inland Sea, Japan. This study was focused on physical characteristics of sediments, namely as particle size of sediment and difference in elevation, and generalizes the relationship between sediments and macrobenthos. A total of 192 species were collected at 187 stations at 6 tidal flats. Physical characteristics of sediment were classified into 9 groups by cluster analysis in relation to sediment particle size and difference in elevation. Those groups had also significant difference in physical characteristics of sediments, and were characterized by some specific macrobenthos species. Distribution of macrobenthos can be explained by the classification of physical characteristics of sediment. These findings show the possibility to predict the variety of macrobenthos community using the physical characteristics of sediment.

Food habits of small fishes in a common reed Phragmites australis belt in Lake Shinji, Shimane, Japan

To clarify the feeding habits of reed fishes, the gut contents of 13 fish species collected in a Phragmites australis belt in Lake Shinji were examined. Six species showed ontogenetic and/or seasonal changes in food use patterns. Smaller individuals generally preyed on small planktonic items (e.g., calanoid and cyclopoid copepods) or small crustaceans (gammaridean amphipods), subsequently changing to other prey items (e.g., mysids and filamentous algae) with growth. The most important dietary items for the reed fish assemblage comprised planktonic copepods, gammaridean amphipods and mysids. However, the relative importance of these changed seasonally, gammaridean amphipods being the most important in autumn and winter, and planktonic copepods and mysids the most important in spring and in summer. Cluster analysis based on dietary overlaps showed that the reed fish assemblage comprised five feeding guilds (planktonic-copepod, mysid, gammaridean-amphipod, filamentous-algae, and detritus feeders). Of these, the three former guilds were the most abundantly represented, whereas detritivores were represented by a single species.

LIFE CYCLE AND PRODUCTION OF ASSIMINEA JAPONICA V. MARTENS AND ANGUSTASSIMINEA CASTANEA (WESTERLUND) AT A REED MARSH IN GAMO LAGOON, NORTHERN JAPAN (G ASTROPODA : ASSIMINEIDAE)

Abstract Population structures, life cycles, growth patterns, and secondary productions of two assimineids, Assiminea japonica and Angustassiminea castanea, were studied at Gamo salt marsh, northern Japan. Cohort analysis revealed a large variation in annual recruitment. It was also revealed that one cohort which had been recruited in a certain year occupied a large proportion of the whole population. Recruitment of A. japonica occurred from August to September whereas that of A. Castanea occurred from September to October. For A. japonica, individuals 1.5 years after recruitment seem to be mature and reproductive, and for A. castanea, individuals at least 1.7 years after recruitment seem to be mature and reproductive. It was estimated that A. japonica had a field longevity of 32–36 months and A. castanea could live for 55 months. Mean annual production of A. japonica (2.73 g AFDW·m-2·yr.-1) during two years was larger than that of A. castanea (0.42 g AFDW·m-2·yr.-1). Secondary production and P/B varied l...

Spatiotemporal changes in distributions of the two dominant bivalve species in an estuarine river connecting two brackish lakes, Japan

ABSTRACT Spatiotemporal changes in the biomass and abundance of the two dominant bivalve species Corbicula japonica and Arcuatula senhousia were investigated at 14 stations positioned along the Ohashi River from November 2005 to August 2007. Corbicula japonica predominantly inhabited the upstream section of the primary branch and Kensaki stream of the Ohashi River, whereas A. senhousia predominantly inhabited the downstream section of the Ohashi River. However, the distributions were highly variable among stations and seasons. Intrusions of saline water from Lake Nakaumi varied with astronomical and climatological factors, and consequently, the halocline of the Ohashi River is subject to spatiotemporal changes. Changes in distributions of C. japonica and A. senhousia occurred in relation to a flood event, indicating that environmental disturbances affect the distributions of the two bivalve species. Responses of the two species to continual saline water intrusion were also observed during the period of normal flow conditions. We suggest that the distribution of the two species is closely related to the dynamics of the ambient saline water, which is the most important factor correlated to changes in the distributions of C. japonica and A. senhousia in the Ohashi River.

Distribution of living (stained) benthic foraminifera (Protista) in the Ohashi River, southwest Japan: a clue to recent faunal change in the Lake Shinji-Nakaumi system.

The modern distribution of benthic foraminifera in the Ohashi River (southwest Japan) was compared with the prevalent types of bottom substrates. Bottom substrates in the upper ranges of the river were characterized by relatively coarse-grained sediment, low total organic carbon (TOC) and total sulfur (TS) contents, whereas those in the lower ranges were characterized by relatively fine-grained sediment, high TOC and TS contents. Two macrobenthic species, Corbicula japonica and Musculista senhousia, were associated with both the coarse- and fine-grained bottom substrate areas, respectively. Ammonia beccurii forma 1 was the dominant foraminiferal species in the Ohashi River and Haplophragmoides canariensis was common in the middle reaches of the river. Variable salinity and biological substrate disturbance, caused especially by M. senhousia, accounted for this foraminiferal distribution. A transition from the H. canariensis assemblage to the A. beccarii forma 1 assemblage has been found in the 20 th century sedimentary record not only in the Ohashi River but also in Lake Shinji. Although the habitat of H. canariensis has not been specified well in the Lake Shinji-Nakaumi system, our result of the modern distribution of benthic foraminifera in the Ohashi River suggests that the faunal transition in Lake Shinji can be explained by the replacement of the dominant foraminiferal species in the Ohashi River.