鹿児島湾に出現した多数のベニクラゲ (刺胞動物門, ヒドロ虫綱, 花クラゲ目) とその若返りについて

To test the influence of both civilization and volcanism on the chemical composition of ostracod carapaces, 32 well-preserved valves from Kagoshima Bay (Kyushu Island, South Japan) were analysed by means of spark source mass spectrometry. In Kagoshima Bay, the extent of pollution corresponds to human activities. Kagoshima Bay is also an area of important volcanic activity: emissions from Sakurajima volcano are very frequent. The species analysed were Argilloecia hanaii, Callistocythere undulatifacialis, Pontocythere subjaponica and Loxoconcha tosaensis. Twenty-three chemical elements were detected. Among them, 11 were always above the limit of detection: Al, B, Cl, F, Fe, K, Na, P, S, Si and Zn. The correlation between Zn and Fe was characteristic of the volcanic environment. Two discriminant analyses were performed using either the location area or the species as grouping variables. An association between Zn and S is possible; it could be related to volcanic activity. The chemical composition of carapaces is ascribed to taxonomic units rather than the environment.

Genetic effects of long-term stock enhancement programs

Decadal- to centennial-scale variability of sedimentary biogeochemical parameters in Kagoshima Bay, Japan, associated with climate and watershed changes

Mercury contents of samples of sea water and fish from Kagoshima Bay, sediments in rivers, and the surface soil from the area surrounding a waste incinerator in the city of Kagoshima were measured to search for the source of mercury in Kagoshima Bay. The results obtained were as follows: 1) Mercury contents of sea water samples at 26 stations in Kagoshima Bay ranged from 6.3 to 19.7 ng/l. When the 26 stations were classified into four areas, the entrance, the middle and the interior of the Bay, and the water around the Sakurajima area, mercury contents of the samples from the last area were significantly higher than either at the entrance or in the interior of the Bay. 2) Mercury contents in the cardinal fish, Apogon notatus, were significantly higher than those in either the dragonet, Callionymus lunatus, or the sillaginoid, Sillago japonica. Mercury contents of fish from the Ushine coast station, the innermost part of the Bay, were significantly higher than those from the other collecting stations. Moreover, significantly interactions between the species of fish and the sampling stations were detected, and mercury contents of cardinal fish from Ushine coast station were 6.7-fold higher than those from the sampling station at the mouth of the Shinkawa river. 3) River sediments obtained 1 km from the mouth of each river contained from 4 to 96 micrograms/kg of mercury. Mercury contents of the river sediments from the Wada river were higher than those from the other rivers examined.(ABSTRACT TRUNCATED AT 250 WORDS)

A total of 13,597 leiognathid larvae collected from 303 larval net collections in Kagoshima Bay during October 1983 and October 1990 were examined and sorted into three species. The larvae of Leiognathus rivulatus (12,677 specimens, 1.2-5.6 mm SL) and L. nuchalis (420 specimens, 1.1-4.4 mm SL) were distinguished from each other mainly by the following characters : in larvae less than about 3.0 mm SL, elongated (L. rivulatus) or dot- or wedge-shaped (L. nuchalis) melanophores along the ventral contour of the tail ; in larvae larger than about 3.0 mm SL, presence (L. nuchalis) or absence (L. rivulatus) of melanophores on the head above the eye. Larvae of the third species (500 specimens, 1.0-3.5 mm SL) were easily recognised by the presence of a melanophore at the symphysis of the lower jaw, being tentatively classified as L. elongatus owing to their morphological similarity to the genus Leiognathus and the common occurrence of adult L. elongatus in Kagoshima Bay.

Detection of localized methylmercury contamination by use of the mussel adductor muscle in Minamata Bay and Kagoshima Bay, Japan

Two procedures were used for the speciation of mercury in marine sediment. One procedure had been proposed for the differential determination of organic mercury, mercury (II) oxide and mercury (II) sulfide in sediments, based on their successive extraction, followed by a cold-vapor atomic absorption spectrometric determination. In this method, organic mercury was first extracted by shaking a sediment sample with chloroform. Another procedure had been proposed for the differential determination of inorganic and organic mercury in environmental and biological materials. In the latter procedure, mercury was first extracted by shaking a sample with 1 M hydrochloric acid containing 3% sodium chloride in the presence of copper (I) chloride. In order to separate organic mercury from inorganic mercury, the extract was shaken with chloroform to extract only organic mercury. In the current investigation, they were suggested that not only methylmercury, but also mercury bound with organic matter in the sediment, could be determined as organic mercury by the former procedure, and that the organic mercury determined by the latter procedure corresponded to methylmercury. These procedures were applied to the speciation of mercury in sediments from Minamata Bay and Kagoshima Bay. In sediments taken in the vicinity of submarine fumaroles in Kagoshima Bay, 7∼37% of the total mercury existed as organic mercury, which was considerably higher than 1∼4% in the Minamata Bay sediment.

Volcanic activity is one of the primary sources of arsenic in nature, and chemical forms of arsenic discharged by volcanic activity are inorganic. Kagoshima Bay has active submarine volcano located in the 200 m deep basin of its northern part. Since dissolved inorganic arsenic is more toxic than organic arsenic it is important to understand the dispersion of discharged arsenic in seawater. To estimate the influence of arsenic emitted from the bottom vents seasonal changes in As(III) and As(V) concentrations in seawater were studied. There are few studies on the impact of arsenic discharged by submarine volcanos in the inner bay. The total concentrations of As(III) and As(V) (T-As) in seawater at the background site in Kagoshima Bay was 1.71 ± 0.35 μg L−1 (av. ± s.d.), similar to the world average value of 1.7 μg L−1. The highest T-As value at the nearest point to the submarine volcano, 3.48 μg L−1, was observed in summer. Since the vertical mixing of seawater cannot occur in summer due to the formation of the thermocline, the deep water is strongly affected by volcanic activity. The increase in T-As was caused by the increase in As(III) concentration suggesting the discharge of As(III) from the vents.

A novel marine bacterial strain, designated JAM 119T, was isolated from a tubeworm trophosome in Kagoshima Bay, Japan. Cells were Gram-negative, rod-shaped, non-spore-forming aerobic chemoorganotrophs and motile by means of a single polar flagellum. The isolate grew optimally at 25-27 °C and in the presence of 3 % NaCl. The major respiratory quinone was Q-10. The predominant fatty acid was C18 : 1ω7c. Phosphatidylcholine, phosphatidylglycerol and an unidentified aminolipid were the major polar lipids. On the basis of 16S rRNA gene sequence analysis, the isolated strain was closely affiliated with members of the genus Planktotalea in the class Alphaproteobacteria, and the 16S rRNA gene sequence similarity of the new isolates with the closest related species, Planktotalea frisia SH6-1T, was 97.3 %. The DNA G+C content of the novel strain was 57.0 mol%. Based on differences in taxonomic characteristics, the isolated strain represents a novel species of the genus Planktotalea, for which the name Planktotalealamellibrachiae sp. nov. (type strain JAM 119T; JCM 31859T=DSMZ 104669T) is proposed.

Seasonal variation in mercury species in seawater of Kagoshima Bay, southern Kyushu, Japan: The impact of active submarine volcanos on the inner bay

A new species of the snapping shrimp genus Alpheus Fabricius, 1798, A. longipalma, is described and illustrated on the basis of material from Kagoshima Bay, Kyushu, Japan. It is referred to the A. brevirostris (Olivier, 1811) species group, and appears closest to A. macroskeles Alcock Anderson, 1894, known with certainty from the Bay of Bengal and Andaman Sea, and A. talismani Coutière, 1898 from the eastern Atlantic. The greatly elongate minor cheliped in males, being subequal to or longer than the major cheliped with proportionally shorter dactylus distinguish the new species from A. macroskeles. The less elongate antennular peduncle and better-developed, rounded distal lamella of the antennal scaphocerite differentiate the new species from A. talismani. All specimens of the new species were trawled from depths greater than 200 m.

To gauge the effectiveness of supplementing native populations of dolphinfish Coryphaena hippurus, we compared farm-raised and wild fish in terms of their horizontal and vertical movement patterns, habitat preferences and thermal niche using pop-up satellite archival tags (PSATs) deployed in two disparate locations: the sub-tropical southeastern coast of Taiwan (wild, n = 4), and temperate Kagoshima Bay, Japan (farm-raised, n = 3). Tagged fish were tracked for periods of 7–40 days, reached depths > 100 m, and experienced temperatures of 15–30 °C in Taiwan, and 20–23 °C in Kagoshima Bay. Fish tagged in Taiwan made primarily northward movements during early summer but changed to a southward course in early winter. In Kagoshima Bay, tagged fish undertook southward excursions along the coast and movements were confined to the bay. Dolphinfish spent > 50% of their time near the surface and made more extensive vertical movements during the night than during the day; vertical movements were largely confined to the mixed layer. Depth distributions appeared to be limited by a Δ6 °C change in temperature relative to sea surface temperature (i.e., > 90% of movements were within 6 °C of the warmest water available).

Temporal changes in the microplankton community due to Kuroshio branch current inflow

Sediments collected from Kagoshima Bay, Minamata Bay and Yatsushiro Sea were analyzed for organic mercury, mercury(II) oxide, mercury(II) sulfide and residual mercury through sequential extraction followed by cold vapor atomic absorption spectrometry. Results show that mercury(II) sulfide (38.4∼96.1%, geometric mean 71.4%) is the most prevalent mercury compound in the sediments followed by mercury(II) oxide (<0.9∼42.9%, geometric mean 5.65%). Organic mercury is present only in a very small quantity (0.21∼12.8%, geometric mean 2.55%). Residual mercury shows a wide range of content in the sediments (2.6∼44.3%, geometric mean 10.5%). The abnormally high mercury concentration observed in the sediment samples from Northern Kagoshima Bay is caused by the condensation of submarine fumarolic gases including elemental mercury and hydrogen sulfide, which are depositing in the surface sediments. This is in accord with the fact that mercury(II) sulfide is the most prevalent mercury compound there. Organic mercury content is high in the vicinity of the submarine fumarole, where mercury(II) sulfide content is very high.

The southern rough shrimp Trachysalambria curvirostris is a small-sized penaeid shrimp inhabiting coastal waters of the Indo-West Pacific and eastern Mediterranean Sea. It is commercially important as a target species mainly for small-scale bottom seiners and trawlers in Japan, Korea, China, and Taiwan. In Kagoshima Bay, southern Japan, this species is one of the most dominant species in the benthic community. The reproductive biology of T. curvirostris including ovarian maturation, size at sexual maturity, and spawning season was investigated in Kagoshima Bay. A total of 5,681 female specimens were collected during June 2002 through December 2005. Ovarian maturity stages were divided into three categories (undeveloped, developing, and early ripe or ripe) based on the visual observation of ovaries fixed with 10% formalin and oöcyte diameter. The size at sexual maturity was estimated to be 17.3 mm in carapace length. The gonadosomatic index (GSI) showed a significant increase with progressing ovarian maturity stage and most of the females with |${\rm GSI} \ge 6\%$| were found to be matured. Percentage occurrence of mature females and inseminated females showed similar seasonal trends and the spawning season was estimated to last from May to November, with a peak during June and July.