Hydrographic conditions of Fukuyama Habor

A series of hydrographic observations were carried out from September, 1958 through July, 1960 in order to clarify the physical and chemical properties of sea water and bottom muds of Fukuyama Harbor, Hiroshima Pref. (Text-figs. 1,2, Table 4). The results are presented in Tables 6, A-F and Text-figs. 4-12 and discussed in comparison with previously published data on the hydrography, ecology and fishery of this water area. Fukuyama Harbor is the former estuary of Ashida River. It occupies the western part of Kasaoka Bay and measures 6.1km2 in area. Being trapezoidal in shape, it is bordered by a reclaimed land in the west, by hilly peninsula in the south and north, and opens wide in the east. The fiat muddy bottom slopes down gently toward the east. Water depth does not exceed 7m below the mean sea level at any part of the harbor. Tidal flats are exposed along the shore at low waters. Water temperature differs very little from air temperature all the year, the monthly mean varying between 7o (January and February) and 28oC (August) at the surface (Text-fig. 3). Water is turbid with the Secchi disc depth seldom exceeding 4 m. These two features can be ascribed partly to such local conditions as the small water depth and the muddy bottom, but are principally due to the fact that the water can not freely pass from the high sea (i. e., the Pacific Ocean off Bungo Strait) to this locality owing to the channels and shallow seas lying on the course. Monthly mean of chlorinity varies within the range of 16.6-17.9‰ at the surface (Text-fig. 3). Seasonal variation of chlorinity is not very great and reaches minima in summer when local precipitation and the drainage of Ashida River reach maxima (Tables 1, 2). Tidal range is comparatively great owing to the interference of the two tidal waves traversing the Seto Inland Sea in opposite directions, one wave from Bungo strait toward the east and the other from Kii Strait toward the west. In an average tide, tidal range measures 2.2m (Table 3) and 50% of the water that is present in the harbor at the high water is drained off during the ebb. Since water is mixed and replaced by the tide, vertical stratification seldom develops and the water is rich in dissolved oxygen from surface to bottom throughout the seasons. Tidal current, however, is not very fast. At low tides C.O.D. increases and dissolved oxygen decreases in the water in the northwestern part of the harbor, where polluted water is discharged from Fukuyama Inlet. In rainy months fresh water is discharged from flood-gates at low tides, temporarily lowering the chlorinity of the surface layer nearby. In the area where the effect of the polluted water or fresh water is not appreciable, various measurements on water are generally within the following range: water color in Forel's scale, 5 or more; pH, 8.2-8.3; C.O.D. by Saeki's alkaline permanganate method, 0.9-1.9ppm; acid-soluble total iron by aa' –dipyridyl method, less than 0.05ppm. The water near the sea bottom often gives greater values of C.O.D. and acid-soluble total iron than those mentioned above. The bottom mud is principally composed of the silt of particle diameters between 2 and 20f-b. The bottom is harder on the inshore side of the 2m depth contour than on the offshore side: the penetration value obtained with the Furukawa's penetrometer averages 30 and 50cm respectively. Other measurements on the bottom mud are within the following range: ignition loss, 3.2-13.9%; organic carbon by Tiurin's rapid titration method, 4.3-18.2mg/g (chlorine error not corrected); total nitrogen by Kjeldahl method, 0.34-1.64mg/g (Table 6). Carbon-nitrogen ratio (chlorine error corrected) is usually close to I 0. Ignition loss, Kjeldahl nitrogen and the oxygen consumption of mud (measured at room temperatures) respectively hold linear relation with organic carbon content (Text-fig. 13). Bottom mud is rich in organic matter and gives small carbon-nitrogen ratio in the area affected by the drainage from Fukuyama Inlet, flood-gates or Ashida River. Major fisheries in Fukuyama Harbor are the "masu-ami" fishery and the culture of the ark shell (Anadara subcrenata) and the laver (Porphyra tenera). The "masuami" is a pound net consisting of a pound 25m wide and 13m long and a leader net about 40m long. It is usually set between the 0 and 2m depth contours, being held in place by bamboo poles driven into the bottom (Text-fig. 14). Fishes, crustaceans and cephalopods are trapped in it as they move with the tide. In 1959 about 70 nets were operated in Fukuyama Harbor with the total catch of 79 metric tons. In the same year, 333 tons of ark shell and 1.8 tons of dried laver were produced by culture and 390 tons of littleneck clam (Venerupis semidecussata) were harvested from the natural beds on tidal flats (Table 7). All the species represented in the commercial catch are typical inhabitants of such inshore waters where water is relatively turbid and seasonal variation of water temperature is great.主として昭和33 ，34年度農林省農林漁業試験研究費によっ

富栄養沿岸海域における懸濁態リンの変動要因

前報で瀬戸内海備後灘におけるリンの存在様式とその季節変動を，海水中のリンを懸濁態リン(particulate phosphorus，PP)，溶存態無機リン(DIP)，溶存態有機リン(DOP)の3態に分別定量する方法により明らかにし，PPとchlorophyll αの相関について考察を加えた。本研究は前報に報告したPPについて，その内容と変動要因を，同時に測定した懸濁態炭素(particulate carbon，PC)，懸濁態窒素(particulate nitrogen，PN)，全懸濁物乾重量(seston weight，SW)，chlorophyll α(chl.α) および透明度の値を用いて解析したものである。 1. SWは，暖季には値が大きく変動も大きいが，低温期には値が小さい場合が多かった。地点別では，沖合のSt.BG-1に比べ，沿岸の浅所の観測点St.2で値が大きく特に海底に接近した5m層では大きい値が観測された(Fig.1，Table 3)。 2. 透明度(Tr，m)と0m層におけるSW(mg/l)との関係は，極めて特殊な3例を除き，ほぼ双曲線的で分布範囲は(Tr)・(SW)=9～20であった(Fig 2)。 3. PCがPNと非常に高い相関を示したこと，回帰式から得られたPC/PN 比が約7.0であったことから(Fig.3)，今回測定したPC，PNはともに主として有機懸濁物成分であったと考えられた。 4. PC/SW比は，懸濁物の有機性の強弱(懸濁物中に有機物が占める割合の大小)の指標として考えることができる。この比の平均値から判断すると，懸濁物の有機性は暖季の沖合点St.BG-1で最も強く，低温期(鉛直循環期)のSt.2で最も弱かった(Table 3)。この比の変動は植物プランクトンによるPCの生成と，河川水の流入や底質の再懸濁に伴う無機懸濁粒子の増加とによって，ほぼ説明できた。 5. 懸濁物のリン含有率は，無機的性質の強い懸濁物では一般に低く，一方，有機性の強い懸濁物ではリン含有率の高い例が相当数あった(Fig.5)。最も有機性の強い懸濁物は赤潮時やSt.BG-1の0m層で観測され，その際，リン含有率は0.32～0.45%に達した。最小値はSt.BG-1の底層で観測され0.06%であった。 6. PCのchl.αに対する回帰およびPC/chl.α比の値から，St.2の懸濁有機物は主として植物プランクトンであり，一方St.BG-1にはデトリタス状の懸濁有機物が多かったと考えられた。 7. 有機懸濁物量(Org)を2・PCと見積り，従って無機懸濁物量(Inorg) をSW-2・PCと計算して，PPのOrg，Inorgに対する重回帰を調べると，一般にPPの増減はOrgのそれに強く依存していた(Table 5)。PPがInorgと有意の回帰を示したのはSt.BG-1の20m層においてのみであった。 8. 前項の関係をさらに理解するため，懸濁態炭素(PC)を計算によって植物プランクトン態炭素(chl.α量の30または60倍)と非植物プランクトン態炭素に二分し，両者に対するPPの重回帰を季節・深度別に解析したところ，St.2においては暖季の底層を除いて，またSt.BG-1では暖季の0，10m層において，PPの変動は植物プランクトン態炭素に強く依存しており，非植物プランクトン態炭素とは明瞭な関係になかった(Table 6)。 9. PPと他の懸濁物成分との共存状態を把握するため，この研究で取扱った懸濁物をその分析測定値にもとづいて，赤潮型，植物プランクトン型，デトリタス型，無機懸濁物型の4種類に分類し，各類型毎に出現状況およびPPの関係する成分比を整理した(Table 7，8; Fig.6)。On the particulate materials collected at two stations in the central part of the Seto Inland Sea, Japan, at roughly monthly intervals from April 1972 to February 1974, particulate phosphorus (PP), particulate carbon (PC), particulate nitrogen (PN), sestonic chlorophyll α(chl. α) and dry weight of total particulate matter ("seston weight", SW) were determined. PC was regarded as particulate organic carbon from the regression of PC to PN. The ratio PC/SW, i.e., the carbon content of the particulate material, was regarded as an index of organic feature of the particulate matter. The mean of this ratio was greater at the offshore station than at the inshore station, and was generally great during the high temperature season especially at 0 m layer. The phosphorus content of the particulate material increased generally with the carbon content. The highest carbon contents were observed on the occasions of the red tide and also at 0 m layer of the offshore station, with phosphorus contents amounting to 0.32-0.45% of SW. Low phosphorus contents were observed mainly in the bottom layer or in the low temperature season. The regression analysis of PC to chl.α indicates that living phytoplankton accounted for major portions of PC at the inshore station; in contrast, large proportions of PC were represented by detrital carbon at the offshore station. SW was divided into the organic and the inorganic matter by calculation, and their contributions to PP was evaluated by multiple regression analysis. The multiple correlation of PP to these two variables was always significant, and this significant correlation derived chiefly from the positive contribution made by particulate organic matter. Therefore, it is concluded that the abundance of PP depended mostly on that of particulate organic matter in all layers of both stations. PC was subdivided into the phytoplankton carbon and the non-phytoplankton carbon by calculation, and their contributions to PP was evaluated also by multiple regression analysis. The result shows that the abundance of PP depended on the abundance of phytoplankton carbon especially in the upper layers of both stations during the high temperature season. In the shallow inshore waters the dependence of PP upon phytoplankton carbon prevailed also in the low temperature season. Recovered particulate materials were classified into four types on the basis of C, N and chlorophyll α contents. The occurrence of each type was discussed with regard to the season, station and depth. A hexagonal diagram was devised to illustrate the chemical characteristics of individual particulate material.This study was supported partly by the Grant in Aid for Fundamental Scientific Research of the Ministry of Education and partly by the Research Fund on the Ecosystem under contract with the Fishery Agency, Ministry of Agriculture and Forestry

富栄養沿岸海域におけるリンの存在様式とその季節変動

瀬戸内海の備後灘北部の2定点において,1972年4月から約2年間,リンの基本的変動様式を知るために,約1カ月間隔で,海水中のリンを懸濁態リン(particulate phosphorus, PP),溶存態無機リン(dissolved inorganic phosphorus, DIP),溶存態有機リン(dissolved organic phosphorus, DOP)の3態に分別して定量した。結果を要約すると次のとおりである。 1. 本海域における海水中のリンの季節変動の一つの特長として,海水中のchlorophyllα濃度が高い暖季(5～10月,水温15℃以上)にPPの濃度が寒季におけるよりも,顕著に高かった。chlorophyllαとPPの間の高い相関などから,懸濁態リンの主部分は植物プランクトンに含まれていたと推定された。富栄養化の進んだ測点で,chlorophyllαが20㎎/m3以上の赤潮状態を呈した場合PPは1.0μg-at/l前後の高い値を示した。 2. DIPの変動にはいくつかの要因が考えられるが,全リン(total phosphorus, TP)中に占めるDIPとPPの割合が逆の変動を示したことは,DIPの減少が,PPの主体をなす植物プランクトンの生産に強く支配されていたことを示唆する。事実,植物プランクトン現存量が大きく,3態中でPPの割合が卓越している場合にはDIPの濃度はしばしば著しく低下した。 また,DIPの濃度は9月から12月にかけて高かったが,これは夏季に流入陸水および底泥から補給されたリンの影響が残存する時期に,植物プランクトンの生産が低下したためと考えられた。 3. DOPが海水中のリンに占める割合は周年かなり高かった。DOPの濃度は比較的季節変化に乏しかったが,その増減はPP濃度の変化と同時に,あるいは多少の遅れを伴って生じた。この結果は,DOPの主体が植物プランクトンおよびその他生物の代謝・分解産物から成る,との考えと矛盾しない。 4. 海水中の各態リン濃度の季節変化は,各態相互間の変換によっているだけではなく,3態の和である全リン(TP)も季節変化を示した。そのさい,リンの補給経路としては,夏季底泥からの溶出,および陸水の流入が指摘された。海水の成層期には光合成層ではTPの増加分にほぼ比例してPPが増加した。 5. これらの結果から,本海域におけるリンのサイクルには植物プランクトンの生産とその分解過程が極めて重要な位置を占めていると考えられる。Field observations were made during two years on the seasonal variation and the balance of three forms of phosphorus (particulate phosphorus, PP; dissolved inorganic phosphorus, DIP; and dissolved organic phosphorus, DOP) in the water column at two stations situated in the eutrophicated coastal region of the Seto Inland Sea, Japan. In the high temperature season concentration of PP was definitely higher than in the low temperature season. High correlation between the concentrations of PP and chlorophyll a suggested that PP was mostly composed of the phosphorus contained in the phytoplankton, especially at high PP levels. Maximal PP values were observed in dense phytoplankton blooms, and were as high as 0.91－1.06µg-at/l. Proportion of DOP in the total phosphorus of seawater was considerably high throughout the year, averaging 38.7 and 41.7% at each station. An increase of DOP in the water column coincided with, or followed with a short delay, an increase of PP. DIP was consumed in the course of the growth of phytoplankton in upper layers during stratification period. There was indication that DIP was supplied to the water column from the outside during September through October. The influx of land water and the liberation of dissolved phosphorus from the bottom sediments were suggested as two main routes of phosphorus supply to the water column. In conclusion, then, it appears that in this sea region the production and decomposition of phytoplankton played an important role in the annual cycle of phosphorus

Probing thermal dissipation dimensionality to laser ablation in the pulse duration range from 300 fs to 1 μs.pdf

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