Development of stable-isotope studies in production ecology of bivalvia.

双壳类是封闭海湾的主要渔业资源，但其生产生态学却有许多模糊之处。利用C、N稳定同位素天然丰度比分析了滨海湾长牡蛎的生产机制，探讨了该技术的应用前景和存在的问题，滨海湾口区颗粒有机质（POM）主要由碎屑组成，l3δC值低于-21。在内区，赤潮发生时，牡蛎消化器官（GD）的13δC和15δN与POM的变化同步，而在非赤潮发生时，POM和13δC的变化与口区相同。通过藻类多氧化合物（POM）的微生态系统和中生态系统培养实验，揭示了POM稳定同位素比值受藻类营养类型、光合作用活性和生长阶段的影响，以及POM稳定同位素比值受藻类营养类型、光合作用活性和生长阶段的影响，表明POM稳定同位素比值受藻类营养类型、光合作用活性和生长阶段的影响。除了藻类物种。另一项关于牡蛎代谢状态影响的培养实验表明，无论是成熟，温度升高还是生长都会使同位素的周转变慢。总之，牡蛎的初级生产力是牡蛎的主要食物来源，因此，对牡蛎碎屑的定量研究比初级生产力的定量研究更为重要。而天然13δC和15δN的稳定同位素比值在藻类POM或牡蛎养殖实验中指出波动因素后将成为“有效工具”。

Bivalves have many obscurity In their production ecology, though they are majour fishiery resorces of a closed bay. We analysed production mechanism of the oyster Crassostrea gigas in Hamana-ko bay using natural abundance ratios of C and N stable isotopes, in addition to the discussion on the prospects and problems of the technic.In a mouth area of Hamana-ko bay, particulated organic matter (POM) was mainly composed of detritus, and l3δC was lower than -21. In inner areas, both 13δC and 15δN of a ganadal-digestional part (GD) of the oyster changed synchronously with those of POM when algal bloom was observed, but the satates of both POM and 13δC were the same as in a mouth area when any particular blooming didn't occur. We made clear that oyster production in the lake depends on detrirus fundamentally and additional growth are supported by primary production.From culturing experiments on algal POM both in microcosms and mesocosms, stable isotope ratios of POM were revealed to be affected either with nutritiona1 type, photo-synthesis activity or growth phase of algae, in addition to algal species.Another culturing experiments on the effects of metabolic states of the oyster showed that either maturation, increasing temperature or growth makes the turnover of isotopes dull.In conclusion, quantitative investigations on detritus would be more inportant than on primary production which was thought to be main food source of the oyster. And, stable isotope ratios of natural 13δC and 15δN will be "effective tools" after fluctuation factors pointed out in culturing experiments on algal POM or the oyster.