Ariake Sea Research Articles

Measurements of Turbulent Energy Dissipation Rate towards Better Understanding of Physical Processes in Coastal Seas : Case Study in Ariake Sea

Measurements of Turbulent Energy Dissipation Rate towards Better Understanding of Physical Processes in Coastal Seas : Case Study in Ariake Sea

北部有明海における出水に起因する塩淡成層の消長過程と乱流構造の関係についての現地調査

To understand difference of density stratification due to freshwater transport from rivers through flood events and tidal range (spring tide or neap tide), four time 25 hours continuous field measurement on tidal current, CTD, turbulence micro-structure, and suspended solid (SS) particle size property were conducted at a point in the northern Ariake Sea in summer and winter in 2014. From the results, the followings were clarified: 1) sub-tidal development and decay process of saline-freshwater stratification during flood season was clearly measured; 2) Turbulent energy dissipation rate was correlated to mean flow velocity in spring tide in winter only, but not in neap tide and in stratified spring tide; and 3) Tempo-vertical profiles of eddy viscosity and dissolved oxygen were related to condition of stratification.

A new species of the snapping shrimp genus Alpheus (Crustacea: Decapoda: Caridea: Alpheidae) from Japan, associated with the innkeeper worm Ikedosoma elegans (Annelida: Echiura: Echiuridae).

A new species of the snapping shrimp genus Alpheus Fabricius, 1798, Alpheus ikedosoma, is described and illustrated on the basis of material from Boso Peninsula and Ariake Sea, Japan. All examined specimens were extracted with the help of a bait suction pump from burrows of innkeeper worm (Annelida: Echiura), constructed on easily accessible intertidal sand beaches or sand flats. The host worm from Boso Peninsula was identified as Ikedosoma elegans (Ikeda, 1904) (Echiuridae). The new species is tentatively referred to the A. brevirostris (Olivier, 1811) species group, but it is characteristic in having several unusual features for the group, such as the very short rostrum without dorsal ridge, the absence of adrostral grooves on the carapace, the strongly reduced dorsolateral spines on the telson, the unarmed antennal basicerite, the non-elongate, almost glabrous major chela, and the lack of movable spines or spinules on ventromesial margin of each cheliped merus. The new species represents the sixth species of Alpheus associated with echiuran burrows.

Isahaya Bay, freshwater lake to an estuary again

The inner 1/3 of Isahaya Bay which is a tributary of Ariake Sea in Japan was shut off from the sea by a dike for the reclamation and disaster prevention in 1997. On the other hand, several environmental and fisheries problems occurred in Ariake Sea after 1990s. Some fishermen insisted that the major reason for the decrease of fishing must be the influence of the dike construction and filed lawsuits. Now the court decision is fixed and Japanese government must open the gates to reintroduce sea water into the reservoir. We made numerical simulations of currents, hydrography and sediment transport to assess the influences of the gate opening. To choose the environmentally wise procedure of gate opening, it is needed to reduce the erosion and deposition of bottom sediments caused by the enhanced tidal current and to minimize the occurrence of hypoxia in the reservoir.

Effects of temperature, salinity, and photosynthetic photon flux density on the growth of the harmful diatom Asteroplanus karianus in the Ariake Sea, Japan

Winter blooms of the diatom Asteroplanus karianus cause bleaching of cultivated Pyropia. We examined the effects of temperature, salinity, and photosynthetic photon flux density (PPFD) on the growth of A.karianus, using culture strains from the Ariake Sea. The maximum growth rate occurred at 20 °C and a salinity of 20, and growth rates at 15–25 °C and salinities of 15–33 were >70 % of this maximum. However, A. karianus could not survive at 30 °C. The threshold PPFD for growth was approximately 1 μmol photons m−2 s−1; this value was lower than that for other coastal diatoms. The half-saturation PPFD was 41.3 μmol photons m−2 s−1 at 15 °C and 30.5 μmol photons m−2 s−1 at 25 °C. The photosynthetic activity (Fv/Fm) of A. karianus was saturated at 50 μmol photons m−2 s−1, which is similar to or lower than surface PPFDs on cloudy days. We found that A. karianus is eurythermal and euryhaline and can photosynthesize and grow in very low light but not at high temperature. These physiological characteristics may partly explain why this diatom blooms in winter, when temperature and PPFD are at their lowest during the year in the Ariake Sea.

Chattonella (Raphidophyceae) bloom spatio-temporal variations in Tachibana Bay and the southern area of Ariake Sea, Japan: Interregional displacement patterns with Skeletonema (Bacillariophyceae)

In 2010, a massive bloom of the raphidophycean flagellate Chattonella occurred in the Ariake Sea and Tachibana Bay. Bloom dynamics and hydrographical conditions were examined by field survey. The development and decline of the bloom occurred three times in Tachibana Bay. First and third bloom developments synchronized with precipitation, and the second bloom developed in synchronization with a salinity decrease which occurred in relation to an increase of river discharge from the Chikugo River which takes several days to flow from the Ariake Sea. These results imply that the bloom was transported with the low salinity water from the Ariake Sea to Tachibana Bay. During blooms along the northern coast of Shimabara Peninsula, the predominant phytoplankton species changed from Chattonella to Skeletonema. Low salinity water intrusion induced an interregional difference of the Chattonella and Skeletonema bloom spatially-differentiated by the salinity in the Ariake Sea and Tachibana Bay.

Bias Correction in Typhoon and Storm Surge Projection Considering Characteristics of Global Climate Model MRI-AGCM3.2S

The typhoons that so often rage across Japan’s southwestern island, Kyushu, are expected to occur even oftener in the future due to global warming. Storm surge projections have been reported based on the super-high-resolution global climate model MRI-AGCM3.2S developed by Japan’s Meteorological Research Institute (MRI). AGCM3.2S overestimates typhoon strength around Japanese islands, however, and this could lead to exaggerated storm surge projection. We therefore evaluate a bias correction method of typhoon strength considering the typhoon characteristics of AGCM3.2 in estimating maximum storm surge anomaly on the Ariake Sea coast. Our results indicated the possibility of storm surge anomaly of 2.8 m, exceeding the current design storm surge anomaly of 2.36 m at the innermost Ariake Sea.

English

Intolerable sulfide emission was spotted at several areas in tidal flats of the Ariake Sea, Japan. Sulfide is naturally produced in tidal flats and rapidly oxidized by sulfur-oxidizing bacteria (SOB). This makes them important players in controlling released sulfide by sulfate-reducing bacteria. A part of SOB can grow heterotrophically and we isolated them from a conserved muddy tidal flat in the Midorikawa Estuary, Kumamoto. The obtained heterotrophs oxidized sulfur compounds in presence of organic carbon. Various metabolic pathways were detected among them during oxidation of thiosulfate and an isolate showed capability of sulfide oxidation. Phylogenetically, they were close-related to the genera Paracoccus, Bacillus, Dyella, and Pseudomonas. This suggested that the isolated SOB were affiliated to diverse classes and functioned diversely in oxidative side of the sulfur cycle. Additionally, population number of heterotrophic SOB was detected in high abundance, suggesting that they played a significant role in the sulfur cycle of the Midorikawa Tidal Flat.   Key words: Heterotrophic sulfur-oxidizing bacteria, isolation, tidal flat, thiosulfate, sulfide.&nbsp

The genetic divergence and genetic structure of two closely related fish species Lateolabrax maculatus and Lateolabrax japonicus in the Northwestern Pacific inferred from AFLP markers

Amplified fragment length polymorphism markers were used to estimate the genetic divergence and genetic structure of Lateolabrax maculatus, L. japonicus and their possible hybrid populations in the Northwestern Pacific. Ninety one individuals were sampled from nine localities including two putative hybrid samples across the distribution range of the two species. Five primer combinations generated a total of 423 loci among 91 individuals of L. maculatus and L. japonicus, 266 of which were polymorphic (62.88 %). The percentage of polymorphic loci in three populations of L. maculatus and five populations of L. japonicus ranged from 31.96 % (Beihai) to 37.94 % (Weihai), 31.05 % (Ishikawa) to 49.29 % (Yatsushiro Sea), respectively. The UPGMA tree constructed with individuals of both species indicated reciprocal monophyletic relationship between L. japonicus and L. maculatus. Hybrid individuals between the two species in Ariake Sea and Yatsushiro Sea were identified by UPGMA tree and principal component analysis (PCA). The sympatry of two clades in the Yatsushiro Sea gave the first evidence of possible reproductive isolation between hybrid and L. japonicus. AMOVA analysis and pairwise FST revealed significant genetic differentiation within both species, indicating limited dispersal ability in two species. Historical isolation coupled with low dispersal ability was responsible for the genetic divergence between species and significant genetic structure in the two species.

Spatiotemporal changes in meiofaunal composition on soft substrates in the semi-enclosed inner section of the northern Yatsushiro Sea

The Yatsushiro Sea is an inland sea in the southwestern part of Kyushu Island, covering an area of 1,200 km2, and is partly connected to the Ariake Sea to the north and the east China Sea to the south. The innermost part of the sea is semi-enclosed by the Shiranui reclaimed land, which was created in 1967. Coastal fishery operators in the region have suggested that fish stocks have declined due to the accumulation of ‘hedoro’ (sludge) on the sea floor, which increased after the land was reclaimed. This project analyzed spatiotemporal changes in the community structure of the meiofauna, which represent ideal organisms for environment assays and in the environmental factors in sediments at four fixed stations around the inner part of the northern Yatsushiro Sea over 3 years (May 2010–February 2013). The results confirm the site of local deposits in the narrow sub tidal section off the Shiranui reclaimed land, where rich organic matter has accumulated and highly sulfidic conditions above the standard criterion value for fisheries were present, along with clear and significant decreases in meiofaunal abundance during the summer. Multivariate analyses, however, did not reveal any strong association between the meiofaunal composition and any environmental factor in sediments, suggesting the organic and sulfidic conditions were not driving the temporal changes in meiofaunal structure in the area. Instead, the meiofaunal changes could be directly related to the low continuous decline in dissolved oxygen and salinity in the water on the sea floor in summer.

The possible physical barrier and coastal dispersal strategy for Japanese grenadier anchovy, Coilia nasus in the East China Sea and Yellow Sea: evidence from AFLP markers.

In order to ascertain the taxonomic status of the Ariake Sea population of Japanese grenadier anchovy, Coilia nasus, and assess the contemporary possible genetic barrier between the west and east coastal waters of the East China Sea, we used amplified fragment length polymorphism (AFLP) markers to detect the genetic structure of C. nasus, in the East China Sea and Yellow Sea. Eighty-one individuals of C. nasus were collected from five locations and 12 individuals of Coilia mystus were sampled from the Yangtze River Estuary. A total of 371 loci were detected by five primer combinations, 310 of which were polymorphic (83.56%). Analysis of molecular variation (AMOVA) and pairwise fixation index (FST) revealed significant genetic differentiation among five samples, indicating limited gene flow among populations. The dendrogram for populations by neighbor-joining (NJ) cluster analysis provided evidence of a clear relationship between genetic and geographic patterns, supporting significant genetic differentiation between China coastal populations and Ariake Sea populations. Compared to the genetic divergence between C. nasus and C. mystus, the level of genetic differentiation between China and the Ariake Sea populations of C. nasus is obvious below the species level, indicating isolated populations of C. nasus in the Ariake Sea. Isolation by distance analysis revealed that direct ocean distance with deep-water at the continental slope and high salinity between west and east coastal waters of the East China Sea served as major physical barrier to C. nasus, supporting the coastal dispersal pattern in this estuarine species, and rejecting offshore dispersal strategy.

1D deformation induced permeability and microstructural anisotropy of Ariake clays

The permeability behavior of Ariake clays has been investigated by constant rate of strain (CRS) consolidation tests with vertical or radial drainage. Three types of Ariake clays, namely undisturbed Ariake clay samples from the Saga plain, Japan (aged Ariake clay), clay deposit in shallow seabed of the Ariake Sea (young Ariake clay) and reconstituted Ariake clay samples using the soil sampled from the Saga plain, were tested. The test results indicate that the deduced permeability in the horizontal direction (<TEX>$k_h$</TEX>) is generally larger than that in the vertical direction (<TEX>$k_v$</TEX>). Under odometer condition, the permeability ratio (<TEX>$k_h/k_v$</TEX>) increases with the vertical strain. It is also found that the development of the permeability anisotropy is influenced by the inter-particle bonds and clay content of the sample. The aged Ariake clay has stronger initial inter-particle bonds than the young and reconstituted Ariake clays, resulting in slower increase of <TEX>$k_h/k_v$</TEX> with the vertical strain. The young Ariake clay has higher clay content than the reconstituted Ariake clay, resulting in higher values of <TEX>$k_h/k_v$</TEX>. The microstructure of the samples before and after the consolidation test has been examined qualitatively by scanning electron microscopy (SEM) image and semi-quantitatively by mercury intrusion porosimetry (MIP) tests. The SEM images indicate that there are more cut edges of platy clay particles on a vertical plane (with respect to the deposition direction) and there are more faces of platy clay particles on a horizontal plane. This tendency increases with the increase of one-dimensional (1D) deformation. MIP test results show that using a sample with a larger vertical surface area has a larger cumulative intruded pore volume, i.e., mercury can be intruded into the sample more easily from the horizontal direction (vertical plane) under the same pressure. Therefore, the permeability anisotropy of Ariake clays is the result of the anisotropic microstructure of the clay samples.

Management of the Oyster Fisheries in Japan's Ariake Sea and Maryland's Chesapeake Bay: A Comparison

An estuarine fi shery can provide high harvest productivity and economic profi t while supporting a traditional way of life in fi shing communities. Overfi shing may lead to environmental degradation and political confl icts that sometimes may collapse the fi shery. Consequently, appropriate management is required for social, environmental, and economic sustainability. To identify similarities and differences in managing two estuarine fi sheries for oysters (Suminoe oyster, Crassostrea ariakensis, and eastern oyster, Crassostrea virginica), we used interviews, fi eld observations, and literature research to compare the oyster industries in the Ariake Sea (Japan) and in Maryland’s Chesapeake Bay (USA) from historical, political, sociocultural, and environmental perspectives. These industries have different historical, political, and sociocultural backgrounds. However, the two regions have lost most of their oyster resources due mainly to environmental degradation and failure of environmental management, coupled with overfi shing and disease in Maryland. The situation in Maryland has also been affected by resistance of the oystering communities to aquaculture. In the Ariake region, fi shermen are more amenable to aquaculture but resistant to allowing new participants into the fi shery. Based on our fi ndings, we propose that an estuarine fi shery management plan should include understanding the history of traditional practices and encouraging cooperation among representatives of industry, politics, and science. Introduction Estuarine fi sheries can provide high harvest productivity and economic profi t while supporting customary values and longstanding sociocultural practices (i.e., systems of thoughts and behaviors shared by a group). Often, harvesting, processing, and shipping occur close to fi shermen’s homes, thereby forming resource-oriented communities with a long history of fi shing. Such a history can play an important role in developing sociocultural norms accepted by the community (Acheson, 1981; Paolisso and Dery, 2010). While capture fi sheries’ production in marine regions worldwide has stabilized in recent decades, the marine aquaculture sector has grown (FAO, 2012), producing ~18 million metric tons (t) of fi nfi sh and shellfi sh in 2011. Oysters are a large part of the shellfi sh component of aquaculture. We compared two depleted fi sheries for oysters (Suminoe oyster, Crassostrea ariakensis, and eastern oyster, Crassostrea virginica) with different sociocultural backgrounds to determine similarities and differences in their management. We hypothesized that there are common problems, and perhaps solutions, that the industries face in spite of different fi shing practices, history, traditional backgrounds, and legal structures. One industry studied is in the Ariake Sea, a fi shing region in western Japan with a long history of governmentencouraged aquaculture. The other is the Maryland part of Chesapeake Bay where the idea of private aquaculture is becoming accepted by some (but not all) fi shermen after a long history of resistance. In addition to examining fi shing practices, we considered attitudes towards cooperation on the part of fi shermen (Paolisso and Dery,

Assessment of the Water Quality in the Ariake Sea Using Principal Component Analysis

The aim of this study is to investigate the condition of the Ariake Sea, Japan, which has been suffering from severe environmental issues for the past few decades. Water quality data have been generated from several points in this area for over 30 years by the Fukuoka, Saga, Kumamoto, and Nagasaki prefectures. In order to understand the characteristics of this sea, principal component analysis (PCA) was utilized using 11 water quality parameters; transparency, temperature, salinity, dissolved oxygen (DO), chemical oxygen demand (COD), dissolved inorganic nitrogen (DIN), ammonium-nitrogen (NH4+-N), nitrate-nitrogen (NO3--N), nitrite-nitrogen (NO2--N), phosphate-phosphorus, (PO43--P) and silica. PCA conveyed the amount of nutrients originating from the river, the organic pollution level, and seasonal changes. Subsequently, principal component scores were calculated for each point. It was concluded that the Ariake Sea environment has been affected by two main factors, which are the nutrients from the Chikugo River and anticlockwise tidal residual flow. These two factors must be considered for the environmental restoration of the Ariake Sea.

Environmental Factors Influencing Fish Species Distribution in Irrigation Channels around Ariake Sea, Kyushu, Japan

Freshwater ecosystems have suffered a long history of anthropogenic disturbances that are responsible for declining fish populations. Fish populations in irrigation channels, in particular, still remain unprotected and relatively unstudied. This study looked to investigate what environmental variables and anthropogenic disturbances had the greatest influence on fish species distribution in irrigation channels. Fish sampling and environmental data collection was conducted throughout six municipalities, spanning 43 sites, in southern Fukuoka, Kyushu, Japan. A total of 37 fish species and 17 environmental variables were statistically analyzed using detrended correspondence analysis (DCA) and receiver operating characteristic (ROC) curve analysis. DCA results showed that channel width, channel substrate and submerged plants had a statistical correlation with fish species distribution. We believe proper management of irrigation channel substrate conditions and macrophyte cover will go a long way in supporting fish species biodiversity and reducing pressure from invasive species. ROC curve analysis revealed a disparity in the environmental preferences of endangered and invasive species. This result suggests that the distribution of endangered species in irrigation channels may be heavily influenced by invasive species. Further research must be done before drafting an effective management solution

Inhibition Effect of Oyster Reef on Occurrence of Hypoxia in Ariake Sea

Inhibition Effect of Oyster Reef on Occurrence of Hypoxia in Ariake Sea

Method for Surface Reflectance Estimation with MODIS by Means of Bi-Section between MODIS and Estimated Radiance as well as Atmospheric Correction with Skyradiometer

Method for surface reflectance estimation with MODIS by means of bi-section algorithm between MODIS and estimated radiance is proposed together with atmospheric correction with sky-radiometer data. Surface reflectance is one of MODIS products and is need to be improved its estimation accuracy. In particular the location near the skyradiometer or aeronet sites of which solar direct, aureole and diffuse radiance are measured, it is possible to improve the estimation accuracy of surface reflectance. The experiment is conducted at the skyradiometer site which is situated at Saga University. There is Ariake Sea near the Saga University. It is rather difficult to estimate surface reflectance of the sea surface because the reflectance is too low in comparison to that of land surface. In order to improve surface reflectance estimation accuracy, atmospheric correction is mandated. Atmospheric correction method is also proposed by using skyradiometer data. Through the experiment, it is found that these surface reflectance estimation and atmospheric correction methods are validated.

Numerical Analysis for Effective Transplant and Seabed Restoration for Recovery of Pen shell Resources in the Ariake Sea, Japan

Numerical Analysis for Effective Transplant and Seabed Restoration for Recovery of Pen shell Resources in the Ariake Sea, Japan

Trend Analysis of Relatively Large Diatoms Which Appear in the Intensive Study Area of the Ariake Sea, Japan in Winter (2011-2015) based on Remote Sensing Satellite Data

Behavior of relatively large size of diatoms which appear in the Ariake Sea areas, Japan in winter based on remote sensing satellite data is clarified. Through experiments with Terra and AQUA MODIS data derived chlorophyll-a concentration and truth data of chlorophyll-a concentration together with meteorological data and tidal data which are acquired for 5 years (winter 2011 to winter 2015), it is found that strong correlation between the chlorophyll-a concentration and tidal height changes. Also it is found that the relations between ocean wind speed and chlorophyll-a concentration. Meanwhile, there is a relatively high correlation between sunshine duration a day and chlorophyll-a concentration.

Locality of Chlorophyll-A Distribution in the Intensive Study Area of the Ariake Sea, Japan in Winter Seasons based on Remote Sensing Satellite Data

Mechanism of chlorophyll-a appearance and its locality in the intensive study area of the Ariake Sea, Japan in winter seasons is clarified by using remote sensing satellite data. Through experiments with Terra and AQUA MODIS data derived chlorophyll-a concentration and truth data of chlorophyll-a concentration together with meteorological data and tidal data which are acquired for 6 years (winter 2010 to winter 2015), it is found that strong correlation between the chlorophyll-a concentration and tidal height changes. Also it is found that the relations between ocean wind speed and chlorophyll-a concentration. Meanwhile, there is a relatively high correlation between sunshine duration a day and chlorophyll-a concentration. Furthermore, it is found that there are different sources of chlorophyll-a in the three different sea areas of Ariake Sea area in the back, Isahaya bay area, and Kumamoto offshore area.