Iron is essential for phytosynthetic and respiratory electron transport, and is directly involved in nitrite and nitrate reduction, N₂ fixation, chlorophyll synthesis, and a number of other biosynthetic or degradation reactions. Humic substances such as fulvic and humic acids that form complexes with many metals, retain metals such as iron in soluble form. The percentage of oogonium formation of Laminaria religiosa with fulvic acid-Fe (FA-Fe) was 3 times higher than that with amorphous iron (am-Fe) and the growth rate of young sporophytes of L. religiosa with FA-Fe was also 3 times higher than that with am-Fe. On the other hand, mangrove forests are effective areas for trapping inorganic nitrogen from anthropogenic nitrogen inputs. In the case of the mangrove crab food web, Sesarma mederi feeds on mangrove leaves and detritus, and Scylla serrata feeds on crabs and worms. In conclusion, the forests on land and in coastal seas are essential for increasing organisms in the sea.

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The effects of hypoxia on the physiological functions of marbled sole, Pleuronectes yokohamae, were examined. Fish were exposed to 3 hypoxic conditions, that is, 6, 4 and 2 mg/L water dissolved oxygen (DO) for 168 hours (7days). With regard to the 4 mg/L DO exposure group, a DO recovery test was also used. When fish were exposed to 4 mg/L DO, the number of red blood cells (RBC) and the plasma cotisol level increased significantly at hours 2 and 12. The renal erythropoietin (EPO) level increased 24 hours after exposure. At hour 168, increased RBC and liver AMP, and decreased liver ATP and adenylate energy charge {AEC value= (ATP+1/2ADP)/(ATP+ADP+AMP)} I were found. As the normal oxygen level was restored, liver ATP and AMP levels recovered within 24 hours after stress. Renal EPO decreased to the control level within 72 hours after stress. Increased plasma cortisol was also found at hour 2. In the 2 mg/L DO exposure group, RBC and plasma cortisol showed significant higher values on hours 2, 12 and 168, compared with those of the control. At hour 12, renal EPO increased. Liver ATP decreased 24 hours after the exposure. Seventy-two hours after the exposure, increased liver AMP and decreased AEC were observed. When fish were exposed to 2 mg/L DO, higher values for plasma cortisol and renal EPO were found in comparison with those in the 4 mg/L DO group. In the 6 mg/L DO exposure group, no significant changes in these parameters were observed.
The renal EPO level, as an effective anoxic biomarker, was determined for wild populations of marbled sole. From July to August (summer) and in December (Winter), fish were collected from 3 sites: in the interior of Tokyo Bay and Kesen-numa Bay, which are affected by oxygen deficient water in summer, and in the eastern coastal region of Sendai Bay (as a reference site). In winter, no significant difference was found in renal EPO levels among marbled sole captured at the above 3 sites. In summer, on the other hand, fish collected from the interior of Tokyo Bay and Kesen-numa Bay sowed a significant higher value for renal EPO, compared to that from the eastern coastal region of Sendai Bay.
These results suggest that (i) hypoxia induces not only stress but also increased erythropoietic activity in fish kidneys and a change in the liver energy supply,(ii) renal EPO is available as a biomarker of environmental oxygen deficiency, and (iii) in summer, marbled sole inhabiting Tokyo Bay and Kesen-numa Bay, in particular the interior, have been exposed to anoxic conditions (under 4 mg/L DO).

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The mineral content and response pattern on a taste sensor of seawater sampled at 5 locations around Oga Peninsula and at 1 location on the Tsurumisaki Peninsula in Oita prefecture were analyzed.
As a result, differences in major mineral concentrations from one sampling point to another and owing to sampling seasons were acknowledged, with exceptions at some sampling locations.
A relationship between the major ion concentration and the response pattern on the taste sensor of seawater was found, and it is suggested that the taste sensor is a useful tool for evaluating the taste of seawater.

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Recently, global warming caused by increases in atmospheric CO₂ concentration has been noticed. It is necessary to measure pCO₂ (CO₂ partial pressure) in the ocean as a driving force of CO₂ transfer in spatiotemporal high density in order to verify this CO₂ cycle. Measurement by buoys and small ships is useful, thus a convenient pCO₂ measuring method with small equipment is desired. This sensor consisted of optical fibers, a fluorescence pH indicator (HPTS) solution and a hollow fiber of gas permeable membrane. This sensor measured pCO₂ with respect to fluorescence intensity changes by pH changes in an indicator solution.
In this paper, performance such as response rate and sensitivity of a flow cell type sensor were examined and compared to the previous results of a probe type sensor. The response characteristics of the flow cell type sensor were affected by the residence time of the indicator solution in a hollow fiber. When the flow rate of the indicator solution was 0.26ml/min for the silicone hollow fiber membrane, SIR A with I.D. of 0.5mm, a length of membrane over 6m was necessary in order to measure pCO₂ 200 - 600 ppmv in water. When the length of the membrane was 8m, fluorescence intensity was saturated under 8.5min. There was no difference in the response in the sea water and the distilled water. The fluorescence intensity decreased with a decrease in temperature. The pCO₂ change in the environment was measured continuously for a few days using the flow cell type sensor of a hollow fiber, and correlated to the pCO₂ detected by NDIR in consideration of the temperature correction.ater.

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This paper introduces characteristics of waves and tides as physical phenomena, and coastal observation system of waves and tides in Japan. Although waves and tides are both periodical sea-surface motion, as their periods are different, different methods are applied for their observation.
NOWPHAS (Nationwide Ocean Wave information network for Ports and HArbourS), Japanese coastal wave observation system, are mainly consist of the sea-bed installed type wave gauges. Due to the development of the Doppler-type Wave Directional Meter (DWDM) and continuous tsunami and infra-gravity wave observation and analysis system, and due to the establishment of the Coastal Wave Center (Coastal Wave Information Department of the Coastal Development Institute of Technology), NOWPAHS made remarkable changes during the last decade.
Tidal observation has been conducted mainly by using the Float-type Tide Gauges all over the Japanese coasts with installation of tide wells. Recently new simple tide observation methods without necessity of tide well construction are studied and developed such as the On-air-type acoustic tide gauge.

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