Yoshinori Koshikawa

Evaluation of Granulated Coal Ash as Artificial Seabed for Eelgrass

ABSTRACT Nakashita, S.; Nakamoto, K.; Koshikawa, Y.; Kim, K.-H., and Hibino, T., 2017. Evaluation of granulated coal ash as artificial seabed for eelgrass. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 40–44. Coconut Creek (Florida), ISSN 0749-0208. Granulated coal ash (GCA) is a by-product of coal-fired thermoelectric power stations. In this study, GCA was used to create a functional artificial seabed for eelgrass. Moreover, the capability of GCA for the growth of eelgrass in an indoor experiment was examined to elucidate the ability of eelgrass to establish itself and grow in a GCA artificial seabed created in an actual marine environment. The eelgrass in the GCA artificial seabed branched and adapted similar to that on sandy ground. A stable eelgrass community was established in one year in an actual marine environment. Furthermore, five years after transplantation, the eelgrass community was maintained. For the GCA artificial seabed, the oxidation–reduction potential of the bottom sediments was approximately 100 mV higher than that of the surrounding ground, and the amount of sulfide decreased to approximately one third of that of the surrounding ground. Even five years after construction, a stable environment was preserved. Therefore, it is concluded that GCA is an effective material for an eelgrass seabed.

A NEW TECHNOLOGY OF SEEDLING PRODUCTION FOR SPEEDY RESTORATION OF EELGRASS (Zostera marina) BED

A new procedure for collecting seeds of eelgrass (Zostera marina) was developed to minimize the damage to an original eelgrass bed. An appropriate treatment by fresh water to control the sprouting time was introduced in the seedling production, which not only improves the germination rate but also reduces the total time for seedling production. These procedures were tested in a field. Sixty shoots of Z. marina raised in tank were transplanted to sea area and increased to 1700 shoots in 18 months. This newly developed technique will be of enormous help in the speedy restoration of eelgrass bed while preserving the genetic diversity of Z. marina.

IMPROVES CREATURES LIVING ENVIRONMENT BY USING A NEW TYPE OF CONCRETE PANEL

We considered that decreasing of the coastal area resources was due to concrete coastal structures that are unable to provide a sustainable habitat for living creatures. To overcome this problem, we have invented a new type of concrete which could suck and maintain plenty of water in it, and keeps the concrete surface under moisture condition. The current paper describes process of the invention as well as trial of the concrete applied to bank panel which may provides living spaces for crabs and eel.

CHARCTERISTICS OF MUDSKIPPER (Periophthalmus modestus) TIDAL AREAS HABITAT OF EDOGAWA RIVER, TOKYO BAY

明治43年 の大洪水を契機に江戸川全川での工事が 開始され,そ のなかのひとつとして、行徳下流では行徳 より東にほぼ直線に約3kmの 放水路の開削工事を大正 5年 に着手,大 正8年 に竣工し,ほぼ現在の形が造られ た.平 水は旧江戸川に流下させるとともに,塩 水の遡上 を防止し,さらに放水路の河床洗掘を防止するため,放 水路入口に床止め(固定堰)を設置した. そして,放 水路の堰地点の流下能力不足を解消する ために固定堰を可動堰形式にし,昭和25年 に着工,昭 和32年3月 に竣工し,現在に至っている.この行徳可 動堰は,通 常時はゲートを下げることにより江戸川放水 路からの塩分の遡上を防止し,上流の取水の安定化を 図る一方,洪 水時はゲートを引き上げて洪水を安全に 流下させる役割をしている(図-1,写 真-1). しかし,設 置後40年 を越える歳月が経過し,海水の影 響によりゲートが腐食するなど堰の老朽化が進み,ま た, 堰部分の川幅が狭くなっているため江戸川の洪水を安 全に流す能力が不足していることなどから,早急に堰を 改築する必要が生じている. このため,行 徳可動堰を改築する前提として,地 域住