The surface ultrastructure and epithallium shedding were observed on the following seven species of articulated coralline algae from Hakodate: Amphiroa zonata, Alatocladia modesta, Bossiella cretacea, Calliarthron yessoense, Corallina officinalis, C. pilulifera and Corallina X. The morphology and arrangement of epithallial cells were different between the two subfamilies Amphiroideae (A. zonata) and Corallinoideae (the remaining species), but epithallium shedding occurred in all species examined, removing fouling microalgae and bacteria. When the zoospores of Laminaria japonica were cultured on living and dead C. yessoense as well as microscope slides, germlings didn't grow on the living plant, but florished on the other substrata. The surface observation under scanning electron microscope revealed that the peeling off of epithallium works as cleaning effect for C. yessoense. From these results, it was concluded that the shedding of epithallium in articulated corallines plays a role on antifouling.

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Colonial growth of the ascidian, Botrylloides simodensis, has been investigated in laboratory conditions. Two strains, S81 and S85, were used. Animals attached on glass slides were held vertically in the culture tank that contained five liters of natural sea water (20°C, pH 8.2-8.4). The sea water was filtered every one or two days and recycled for about a month. The aeration was not performed. The diatom, Nitzschia closterium, was added to the culture tank twice a day at the final concentration of 0.2-4×10⁴cells/ml. The S81 strain showed a zooid proliferation value of 2.3 on an average. The life span of individual zooids was 16-17 days. The gonads became mature periodically and oozooids (F1) could be obtained by means of autogamy. On the other hand, the S85 strain did not grow well when it was fed on only Nitzschia. The artificial diet, Liquifry marine (40-80μl/tank/day), was very effective for keeping high proliferation ratio (maximal value; 2.9). However, the sea water needed to be exchanged with new one every two or three weeks. The permissive number of colonies in a single tank was examined in the last series of this work. When two or three colonies coexisted, they proliferated well (maximal value; 2.4). But, in case of four to five colonies, the value did not exceed 2.0. The results showed that when natural sea water is available periodically the colonies of Botrylloides simodensis can be maintained easily in any laboratory.
MATERIALS and METHODS
Animals Botrylloides simodensis has been recently separated from B. violaceus taxonomically (SAITOH et al., 1981). The original stocks of B. simodensis were collected in Uranouchi Inlet, Usa, Kochi Prefecture, in 1981 (strain No. S81) and in 1985 (strain No. S85). Ever since their asexual progenies have been reared on glass slides in culture boxes floating in the field as described previously (SUGIMOTO and NAKAUCHI, 1974).
The S81 was brought to our laboratory and reared from March to August in 1983 and from October, 1984 to February, 1985. It was very tough and proliferated well in laboratory conditions. Unfortunately, the S81 was extinguished in summer of 1985 because of red tide. The S85 was kept in the laboratory from November of 1985 onward.
Only a single colony was attached to a single glass plate which was held vertically in a culture tank. Respective series of experiments were always performed using clonal colonies derived from a large parental colony. The parental colony was separated into many small pieces and they were put on new glass slides in a moist chamber for about one hour in order for them to adhere firmly to the substratum.
Sea water About 10 liters of natural sea water were prepared for a single culture tank. It was halved and each (five liters) was used alternately every one or two days. It was renewed immediately after use by passing through cotton filter. The sea water that contained animals was kept at 20°C and adjusted to pH 8.2-8.4 with 0.2M Tris, if necessary. The aeration was not performed. The sea water could be recycled for about a month. But, it needed to be exchanged with a new one every two or three weeks when the artificial diet was administered.
Foods Animals were fed on the diatom, Nitzschia closterium. The diatom was permitted to proliferate in the artificial sea water, Jamarin (Jamarin Lab. Japan), containing 9μg/ml KH₂PO₄, 72μg/ml KNO₃, and 0.5μg/ml Fe·EDTA. Under continuous light condition, it became saturated in about a week. Twenty mililiters of this diatom-containing Jamarin were added to the tank (the final conc. 0.2-4×10⁴cells/ml) twice a day. The cell number of the diatom was consistent roughly with that applied previously to Symplegma reptans (NAKAUCHI et al., 1979).

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SCUBA diving application and the analysis of diver's observation or sampling data were reexamined at the artificial breakwater of the fossil fuel power plant station in Fukushima Prefecture.
In the shallow coastal region at about 10m depth, the distribution of sessile organisms except the algae could be recognized, if an experienced biologists surveyed from the surface to the bottom by way of a single belt-transect.
As for the quantitative sampling area, 900-2500cm² is recommended from the species-area relations.
And the similarity of such shallow-water fauna has clearly shown no zonational pattern.
It is important when assessing the faunal distribution not only to use the numerical index but also to use pictorial representation, therefore the computer program CDM-KITE was introduced as a new tool.

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The oxygen consumption and the survival time of the blue mussel, Mytilus edulis, was determined in the sea water of low oxygen tension to study of tolerance of anoxia. Effect of low oxygen tension was observed at a value less than 0.5ml to large mussel (5.9cm shell length) and 0.1ml/l to small mussel (1.7cm shell length). After decrease of oxygen consumption, the mussel closed their shell valves and have little consumption. The survival time of the mussel in a dissolved oxygen of less than 0.07ml/l was longer in 10°C than 20°C, and the smaller mussel have the longer survival time. The longest survival time was recorded in 2.0cm shell length which survived more than 45 days at a temperature of 10°C.

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The effect of warm water effluent from the Takahama Nuclear Power Plant on the survival rate of the common mussel, Mytilus edulis galloprovincialis, which is one of the representative fouling organisms along the coast of Uchiura Bay was studied.
About 50 adult common mussels 60 to 80mm in shell length collected at the depth of 10 to 15 meters in the eastern part of the bay were confined in two steel cages (50×50×20cm) suspended 1 or 10 meters depth at the three fixed stations.
From April 1980 to March 1981 their mortality was checked monthly on, along with the water temperature measurement made at the surface to 10 meters depth at each station. In the August 1980, the maximam water temperature at 1 meter depth attained more than 29°C at stations 1 and 2, which were located 500 and 1000 meters from the outlet of the nuclear power plant, respectively. Only the groups suspended at 1 meter depth showed a high mortality of more than 80 percent in late September at stations 1 and 2.
It was suggested from the results obtained that the adult common mussel can not survive several days of high temperature over 29° to 30°C.

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