瀬戸内海沿岸海域における細菌叢 : Ⅱ.福山湾における従属栄養細菌の特質と物理-化学的要因

瀬戸内海沿岸海域における従属栄養細菌の菌叢を調べ、これらが光合成を営むプランクトンの量とどのような関係にあるかを検討した。その結果を以下にまとめる。1. プランクトンの量を示すクロロフィールa量は水温が20℃～26℃の時に多く、しかもCODや全リン濃度と比例関係にあった。2. 細菌学的には、これら物理-化学的要因とは関係なく、一般菌数は全体を通じて10⁴～10⁶MPNレベルを維持し、そのほぼ100%が硝酸塩還元能およびゼラチン液化能を有していた。3. このような状況にある海域での細菌叢を調べると、比較的清澄な海域、汚濁の進んでいると思われる海域のどちらにも優勢的に存在するVibrioを除いて検討してみると、全体を通じてPseudomonasとFlavobacteriumが、属レベルまで分類することができたグラム陰性桿菌のうちのほぼ50%以上を占めていた。一方、汚濁の進んだ海域で多く検出されているAlcaligenes、Moraxella-Acinetobacter、 それにEnterobacteriaceaeに属するものは少く、合わせて50%を越えたのはStation 1で2回、 Staion 2で2回 Station 3で6回であった。4. 以上の結果から、 光合成を営むことのできるプランクトンの量はCODや全リン濃度、pH、水温といった環境要因に大体比例していたが、同じ海域に分布する細菌叢は、その数、種類ともに、これらとは比例せず、またプランクトン量の増減とも関連した変化は示さなかった。

For the evaluation of the sea water in the Seto Inland Sea, the total of heterotrophic bacteria in the coastal sea water of the Fukuyama bay were investigated and discussed from the standpoint of the relation of these bacterial flora with the amount of chlorophyll a. Results were summarized : 1. A big amount of chlorophyll a were detected at the time of water temperatures of 20℃ to 26℃. They were in correlation with the concentration of COD and of total phosphate. 2. Bacteriological investigations of that sea water were made. The viable counts remained in 10⁴ to 10⁶ MPN levels, and these bacteria showed to be reduced nitrate and liquefied gelatin in about 100%. There was little correlation between the number of bacteria and the amount of chlorophyll a. 3. In the case of without-vibrio, which occured frequently in clean sea water as well as in contaminated sea water, Pseudomonas and Flavobacterium which had been frequently observed in clean sea water were round in the gram negative rods of all the sea water samples in a rate of more than 50%. On the other hand, Alcaligenes and Moraxella-Acinetobacter and the bacteria belonging to the family Enterobacteriaceae which were observed frequently in contaminated sea water were few at the time when the concentration of COD and the amount of chlorophyll a were high. 4. From these results, it was concluded that the phytoplankton biomass was in proportion to the physico-chemical properties of concentration of COD, total phosphate and water temperature, buttthat the number and the flora of heterotrophic acteria were few in proportion to these physico-chemical properties and in proportion of the phytoplankton biomass in the coastal sea water of the Fukuyama bay in the Seto Inland Sea.