Uraga Channel Research Articles

Eutrophication trends in the coastal region of the Great Tokyo area based on long-term trends of Secchi depth.

The coastal ocean's environment has changed owing to human activity, with eutrophication becoming a global concern. However, oligotrophication occurs locally and decreases fish production. Historically, the Secchi depth has been used as an index of primary productivity. We analyzed the results of over-a-half-century routine observations conducted in Sagami Bay and Tokyo Bay to verify the eutrophication/oligotrophication trend based on Secchi depth observations in a temperate coastal region near the Greater Tokyo area, which is highly affected by human activities. Data recorded in the Kanagawa Prefecture from 1963 to 2018 were used in this study. After quality control, the observation area was divided into Tokyo Bay, the Uraga Channel (outer part of Tokyo Bay), Sagami Bay (northern part), and Sagami Nada (southern part of Sagami Bay) based on temperature and salinity at a depth of 10 m. Because the environmental parameters showed autocorrelation, time-series and correlation analyses were conducted using generalized least squares (GLS) models with a Prais-Winsten estimator. The Secchi depth was the shallowest in Tokyo Bay, followed by the Uraga Channel, Sagami Bay, and Sagami Nada, and was deep in winter (December and January), and shallow in summer (July) in all regions. The correlated analyses using the GLS model indicated that the shallowing of Secchi depth was significantly associated with decreases in temperature, salinity, and phosphate concentration. However, time-series analyses using GLS models indicated that the Secchi depth was significantly shallower, except in Tokyo Bay, where the surface temperature was significantly warming and the surface phosphate and nitrite concentrations decreased everywhere. A significant shallowing trend of the Secchi depth was mostly observed during the light-limiting season (January-March). Correlation analyses suggested the importance of horizontal advective transport, particularly from Tokyo Bay, which has cold and less saline eutrophic water. However, long-term shallowing of the Secchi depth was associated with warming, and changes in salinity were not significant in most months when the Secchi depth trend was significant. Thus, horizontal advection is not the primary cause of long-term eutrophication. Because the eutrophication trend was primarily observed in winter, when light is the major limiting factor of primary production, we concluded that warming provides a better photoenvironment for phytoplankton growth and induces eutrophication. As a decline in anthropogenic nutrient input after 1990s was reported in the investigated area, the long-term eutrophication trend was most likely caused due to global warming, which is another alarming impact resulting from human activities.

Temporal variation of particulate organic carbon flux at the mouth of Tokyo Bay.

A sediment trap experiment was conducted at a depth of 750 m at the mouth of Tokyo Bay to clarify the quantity and transport process of particles from the bay to the open ocean. The high total mass flux (8.7 ± 4.5 g m–2 d–1) suggests that the particles not only originate in the surface layer right above the trap, but are also focused in Uraga Channel and discharged into the bay mouth. The organic carbon and nitrogen isotope ratios (δ13Corg, δ15N) of the trapped particles were like those of the surface sediment in the bay, that is, a mixture of particles in rivers and suspended particles in the surface layer of the bay. Compared with the results of the experiment conducted in 1995–2002, the average total mass flux was reduced by 70% and organic carbon content was reduced by 50%. The δ13Corg values of trapped particles were also lower than those observed in the previous experiment, indicating a lower contribution from surface-suspended particles with high δ13Corg values in the bay. These results could partly reflect a decrease of the concentration of the suspended particulate carbon in the bay by half over 20 years. Another factor contributing to the decrease of the flux at the bay mouth would be that the intrusion of Kuroshio coastal water into the bay, which pushes particles out to the bay mouth, has not occurred in recent years.

A new species of the squat lobster genus Uroptychodes Baba, 2004 (Decapoda: Anomura: Chirostylidae) from Japan.

A new species of the chirostylid squat lobster genus Uroptychodes Baba, 2004, U. fuscilineatus, is described and illustrated on the basis of a single ovigerous female from the Uraga Channel, central Japan, at depth of 250 m. The new species appears most similar to U. spinimarginatus (Henderson, 1885) and U. yapensis Dong, Gan Li, 2021 among the 13 known congeners, but is notable in the pereopod 2 not being definitely more slender than the pereopods 3 and 4 and the remarkably spinose pereopods 14. A possible association of the new species with crinoid is suggested. An updated identification key to species of Uroptychodes is presented.

Anthropogenic Osmium in Macroalgae from Tokyo Bay Reveals Widespread Contamination from Municipal Solid Waste.

Human activity is influencing the global osmium cycle, driving the Os isotopic composition (187Os/188Os) of the hydrosphere and associated sedimentary material to lower values. Here, we present the Re and Os abundance and isotope systematics of macroalgae, a proxy for seawater, from Tokyo Bay to elucidate the potential sources of anthropogenic Os to the Pacific Ocean. Macroalgae from the Uraga Channel, which connects Tokyo Bay to the Pacific Ocean, record relatively low Os abundances (∼10.1 pg/g) and an 187Os/188Os of ∼0.9, indicative of surface ocean seawater. Contrastingly, macroalgae within the bay closest to central Tokyo record the highest Os abundances (∼22.8 pg/g) and lowest 187Os/188Os values (∼0.47), suggesting contamination from human activity. To determine the source of anthropogenic Os, we have developed the first Os emission inventory, based on the East Asian Air Pollutant Emission Grid database (EAGrid2010). The close relationship (R2 = 0.67 and p-value = <0.05) between Os inventories and macroalgal data suggests that municipal solid waste incinerators (MSWIs) are the dominant source of Os to Tokyo Bay. Projections for Japan estimate that 26-18+38 ng Os/m2/yr is released from MSWI smokestacks, leading to a concentration in precipitation of 26-18+38 fg/g, identifying MSWIs as a major contributor of anthropogenic Os to the hydrological cycle.

Development of ship behavior prediction model by using Recurrent Neural Network

It is necessary to develop a system that reduces the load on the marine traffic control because its work is manual and heavy. In this study, we created a ship behavior prediction model using Recurrent Neural Network (RNN) to explore the possibility of marine traffic control and ship maneuvering support by machine learning. Specifically, we predicted the position and course of a ship that would go through the bend of the Uraga Channel from 5 items (length, width, course, speed and position) and displayed on a map. It shows that the effectiveness of ship behavior prediction by machine learning has been confirmed.

Nippoparasitus unoashicola, a new genus and species of philoblennid copepod (Cyclopoida) parasitic on the Pacific sugar limpet, Patelloida saccharina (Linnaeus, 1758) (Patellogastropoda: Lottiidae) from the intertidal zone of eastern Japan.

Nippoparasitus unoashicola, a new genus and species of mesoparasitic copepod, is described based on specimens of both sexes collected from the mantle cavity of the Pacific sugar limpet, Patelloida saccharina (Linnaeus, 1758) (Patellogastropoda: Lottiidae), in the intertidal zone of the Uraga Channel (North Pacific Ocean), Japan. Nippoparasitus gen. nov. differs from other philoblennid genera by two unique characters: the labium is bloated and branched into multiple digitate lobes in female, and the antenna has three claw-like spines on the terminal segment. Nippoparasitus is probably closely related to Myzotheridion Laubier & Bouchet, 1976 with which it shares a series of processes on the terminal segment of the maxilla.

東京湾・浦賀水道海上の航路における3G電波強度調査

A small vessel like a fishing vessels and pleasure boats account most of the marine accidents with the fatality or missing person in these five years. For preventing such a marine accidents, it is important to make a contact immediately to stop such accident. Current major way of accident notification is by using AIS or Satellite communication based system. Although these ways are useful for marine accident detecting, it is not mandatory to equip those systems to a small vessel. Furthermore, current systems are expensive for a small vessel.In this study, we focused on that 3G radio communication having possibilities to be available in coastal waters of Tokyo, measured 3G radio field intensity by developed measurement system in Tokyo Bay and Uraga Channel. From the results of the measurement experiment, we showed the 3G radio can receive on the sea of around 5km from the land and near the sea surface. The realization of new marine accidents prevention system can be expected by utilizing the 3G communications in coastal waters of Japan We described the design of the system that takes into account the characteristics of 3G communications on the sea.

Towards the development of intelligent navigation support systems for group shipping and global marine traffic control

Computerised navigation is a developing technology in a branch of autonomous and intelligent engineering systems. It aims to enhance safety and security at sea and to improve the reliability of ship-to-ship operations and global marine traffic control. A recently standardised automatic identification system (AIS) takes full advantage of GPS-based real-time positioning and timing information of ships. The use of the AIS is steadily growing to meet the needs of the merchant shipping and fishing industries. Nevertheless, a significant decrease in the number of ship accidents and hazardous incidents in open waterways has yet to occur. The work gathered in this paper is to establish a proactive means to prevent marine accidents by the use of the full potential of the AIS. Specifically, this paper describes the development of an AIS synthesis-capable navigation support system enhanced with a degree of intelligence built from a physical model suitable to capture the dynamics of group-based navigation of ocean-going vessels. The system envisioned is to provide adequate decision-making support for group shipping, especially during the critical maneuvering in restricted areas such as channel passing and harbour approaches. Foundations for and experimental results of this study, including an analysis with the simulated traffic of Tokyo Uraga Channel route, are presented.

A New Species of Heteromysis (Mysida, Mysidae) Associated with Sponges, from the Uraga Channel, Central Japan, with Notes on Distribution and Habitats within the Genus Heteromysis

A new species, Heteromysis komaii , is described from specimens obtained from the gastral cavity of sponges, Callyspongia confoederata , from the Uraga Channel, located at the entrance of Tokyo Bay, central Japan. Heteromysis komaii is distinguished from all known species of the genus by several features: the distal segment of the antennular peduncle has a flagellate spine at the inner distal angle, the antennal scale is longer than the antennal peduncle, the endopod of the third thoracopod has two flagellate spines at the inner distal angle of the carpus, the fourth to eighth thoracopodal endopods have the carpopropodus divided into two or three subsegments, the male pleopod is unmodified, the uropodal endopod is without spines, the telson has spines on the distal half of the lateral margin, and the apical cleft of the telson is with spinules throughout. The distribution and habitats of the species of Heteromysis are reviewed.

海難発生地点のランダム性に基づく海難距離の計算推定法

The author published "Casualty Distance" has two characteristics, the exponential distribution and Poisson's one in the previous paper. The average of casualty distances is one of the most important elements that determine these distribution functions. The present report deals with the calculating method for estimating the mean casualty distance that have remained unsolved sufficiently when each casualty distance is unknown to be classified in the previous paper. This method is confirmed by comparing the calculated distances with the actual measured ones and distribution curve in the Uraga Channel, Shikoku-Shionomisaki coastal regions and the marine accidents requiring rescue in Japan for twety-one years.

海難事故のランダム性による「海難距離」の統計的特性と海難事故評価への応用

This report deals with the definition and consideration of "casualty distance" and its applications to marine disasters. Casualty distance is the interval from the base line drawn by a coast or center buoys to a casualty point obstructing marine traffic. The distance is the similar to the time headway of cars or ships in traffic engineering, which has two characteristics : the exponential distribution and Poisson's one. They were confirmed by comparing the calculated results with the actual conditions in the Uraga Channel and Shikoku-Shionomisaki coastal regions. These characteristics can be also applied to the survey and analysis on marine casualty by showing some numerical illustrations of the marine accidents requiring rescue in Japan and the passage widths at Urage Channel.

船舶航行密度に伴う遭遇状態とその変化について

This paper is concerned with the research on the relationship between ship's encounter situations and traffic density, especially pay particular attention to the relationship between multiple encounter and traffic density. The encounter situations are divided into simple encounter and multiple encounter, in this paper the multiple encounter is defined when two or more than two targets are involved in the situation simultaneously and divided into same multiple encounter and different multiple encounter. Simulation was performed in random traffic condition that could be easily adjusted with traffic density. First, the encounter situation from the viewpoint of each ship was analyzed. Then the encounter combinations between the ships that involved in one encounter situation were classified according to their respective encounter situations, and the ratios of the combinations in various densities were obtained. Also through the simulation method, this paper certified the result that the ratio of the multiple encounters to the total encounters is proportional to density, whereas the number of encounters is proportional to the third power of density. Finally, using actual traffic data of Uraga channel and its vicinity in Tokyo Bay investigated in 1994, the encounter situations in Uraga channel where traffic flow are restricted by regulation rules were compared with those in random condition.

Beach Erosion of Futtsu-Misaki Cuspate Spit Separating Tokyo Bay and Uraga Channel

Beach changes around Futtsu-misaki cuspate spit located at the mouth of Tokyo Bay and protruding west are investigated through the comparison of aerial photographs. It is found that shoreline has been eroded in recent years mainly due to lack of sand supply from the southern coast caused by the obstruction of continuous littoral transport by Shitazu fishery harbor. At the tip of the spit the seawall was destroyed and a concave shoreline was formed due to erosion as the shoreline became stable under the condition of two fixed control points at Dai-ichikaiho island and the tip of the seawall. Sand eroded from the tip of the spit was found to be carried to the north coast of the spit by wave action.

１９００年代における東京湾の赤潮と植物プランクトン群集の変遷

Historical plankton records on red tide events and phytoplankton community in Tokyo Bay published between 1907 and 1997 were reviewed to elucidate long-term changes. Before 1940s, naked flagellates unpreservable in formalin-seawater predominated over the phytoplankton, and were major causative organisms of red tides. Community composition of diatoms and armored dinoflagellates in the bay and the adjoining water, Uraga Channel, showed little change in this period. In 1950s, a red tide by a diatom Thalassiosira mala was recorded for the first time. Eutrophication process developed rapidly between late 1950s and early 1970s, and now the bay is one of the most polluted inlet waters in the world. In the meantime, that by Skeletonema costatum came to occur very frequently. The basic community composition of phytoplankton in recent days was already molded in late 1960s with rapid eutrophication process. Species diversity reduced owing to desappearance of neritic/oceanic species from the bay and the occupation by several dominant species. Clear dissimilarity of phytoplankton community composition between Tokyo Bay and Uraga Channel was also made up in this period, suggesting large environmental differences between the two areas. The biomass of diatoms has been increasing since 1950s, mainly due to S. costatum. Since 1970, Heterosigma akashiwo came to make red tides frequently and occasionally built up exceptionally high biomass(>1000 mg-chl. a m-3). Since early 1980s, nano-and micro-fragellates came to be a major component of phytoplankton. The cell densities of brackish water species have been increasing since 1980s with increase of freshwater inflow caused by a human population growth around the bay. Averaged annual occurrence of red tide events varied as follows ; twice for 1900s-1940s, five times for 1950s, ten times for 1960s, 14 times for 1970s, 19 times for 1980s and 15 times for 1990s. These results suggest that the artificial impacts on the aquatic ecosystem of Tokyo Bay altered the community composition of phytoplankton between 1955 and 1970.

THE DAWN OF ENGLISH STUDY IN IWAKUNI

M. C. Perry's black ships appeared in the Uraga Channel in 1853. This insertion not only disturbed the Bakufu, but also effected the Mori clan and the Kikkawa clan.The leaders of both clans positively adapted to the world's diversification. They realized that the traditional studies of Confucianism did not enable ships to sail the outer seas. The black ships were an example of high-tech that the population in the West had integrated since the Industrial Revolution. They had manpower, capital, and the knowledge of current technology in order to build powerful ships.By introducing Western Civilization, both leaders of the head clan and the branch clan had to hasten the modernization of their clans in order to increase their military strength. They invited foreign teachers to educate the clan members in the subjects of science and mathematics. This also gave the youths of the clan the opportunity to learn foreign languages.Tsunetake Kikkawa (1855-1940), the 29th head of Kikkawa clan, founded Iwakuni English Language School in 1872. He invited H. A. Stevens, a venturous young man from Jersey Island in the English Channel, as an instructor at the school.Stevens was a herald of Westernized Civilization. Although his teaching at IELS lasted only two years, he imprinted the minds and hearts of the 17 youths. These youths grew up to be pillars in society and contributed greatly to the progress of modernization in Japan. Thus Tsunetake Kikkawa's goal was achieved.This paper traces the foundation of Iwakuni English Language School and H. A. Stevens, the English teacher.

珪藻の環境指標種群の設定と古環境復原への応用

Diatom species were classified as environmental indicators based on the species groups of benthic diatoms presented by KOSUGI (1987) and on planktonic diatoms from Tokyo Bay and Uraga Channel. All data on diatom ecology were obtained from living cells discriminated by the staining method (KOSUGI, 1985).The species groups identified by KOSUGI (1987) were classified on the basis of similarities in adaptation to both salinity and substratum factors, so it can be said that they were classified from the biological viewpoint. In order to obtain indicators applicable to reconstruct paleoenvironments, it is necessary to clarify the relationship between the species groups and real environments. From this point of view, the environments specified by the salinity and substratum of each species group was examined.The diatom environmental indicators were classified as follows;A: Indicators of an outerbayB: Indicators of an innerbayC1: Indicators of an aquatic plant vegetation in saline waterC2: Indicators of an aquatic plant vegetation in brackish waterD1: Indicators of a sand flat in saline waterD2: Indicators of a sand flat in brackish waterE1: Indicators of a mud flat in saline waterE2: Indicators of a mud flat in brackish waterF: Benthic diatoms in fresh waterG: Planktonic diatoms in fresh waterH: Indicators of a river mouthAs an example of application to paleoenvironmental reconstruction, the Holocene fossil datom assemblages from the lower reach of the Murata River, Chiba prefecture, were analyzed using diatom environmental indicators. As a result, most fossil diatoms could be classified on the basis of each environmental indicator. And their vertical changes in fossil assemblages could be related to successive changes of paleoenvironments in the Murata River region.It is an important part of this application that the paleoecological analysis using those indicators has the ability to reconstruct environments and their changes clearly. The main reason is that the indicators have been classified based on the data from living diatoms only, and that the relationships between them and both salinity and substratum as environmental factors have been clarified by the gradient analyses.

多層構造モデルのもとで多点の&lt;i&gt;S&lt;/i&gt;-&lt;i&gt;P&lt;/i&gt;時間をもちいた古い地震の震源再計算

For the purpose of precise relocation of earthquakes which had occurred in Japan around the first quarter of this century, a computer program was written which calculates hypocenter parameters by the method of least squares using S-P times at more than three stations and employing an arbitrary multi-layered crustal structure.As examples of relocation, about five semi-destructive earthquakes in the Kanto district: the Ryugasaki earthquake of 1921, the Yatabe earthquake of 1922, the Mitsukaido earthquake of 1923, the Uraga Channel earthquake of 1922 and the Haneda earthquake of 1926, all near-field S-P time data were carefully examined and hypocenters were redetermined. The epicenters and the focal depths obtained are expected to be uncertain by less than ±10km except the Uraga Channel earthquake. The former three, which has been suspected to be precursory activities of the Great Kanto earthquake of 1923, were ascertained to have their origins in the upper mantle beneath the SW part of the Ibaraki Prefecture where is even now a remarkable swarm area.

The Effect of the Vertical Deflection on the Sea-crossing Levelling on Uraga Channel

The Effect of the Vertical Deflection on the Sea-crossing Levelling on Uraga Channel

浦賀水道における交差回数について(日本航海学会第43回講演会)

浦賀水道における交差回数について(日本航海学会第43回講演会)

東京湾及びその附近のカタクチイワシ漁況について

This article gives an analysis on catches of the Japanese anchovy, Englaulis japonica (Houttuyn) in the Tokyo Bay and its adjacent waters. The results may be summarized as follows:- (1) Good catches usually appear during the period from November to February. (2) A seasonal migration occurs as the fish are entering to the Tokyo Bay on spring and exiting from the bay on late autumn. (3) It appears to be that two groups of the fish are existing in the waters of the southern part of the Uraga Channel and Tateyama Bay. One of them is migratory, and the other not migratory. (4) The water temperature, in which the fishing was made, ranges from 11°C to 27°C (Fig. 4).