Quantitative relationship on the behavior between organic matters and radionuclides in seawater

2002年11月20日至12月10日，在骏河湾400米深处的中层海水中进行了围隔实验。在培养的前7天，自养生物量从0.2μg C1^增加<-1>到1.3mg C1^<-1>。在孵育第7 - 12天，硝酸盐和磷酸盐迅速耗尽。研究认为，营养盐丰富的环境和捕食者浓度较低导致的低放牧压力是导致自养组分水华的主要原因。细菌、异养鞭毛虫和纤毛虫的生物量峰值出现在自养生物量峰值之后的第9 - 13天。这些结果表明，有机物质从自养组分转移到细菌和随后的HNF和纤毛虫后，硝酸盐耗尽，然后有机物质流经微生物环路。将颗粒有机物（POM）分为不同粒径（&gt;500μm、500 μ m ~ 105、105 μ m ~ 25、25 μ m ~ 0.4），并分别测定了各粒径中TH-234、Pb-210、Po-210的含量。Th-234未以溶解形式检测到，而80%的Th-234以颗粒形式存在于0.6至500μm的粒度级中。Th-234、Pb-210和Po-210的行为是由于0.4 ~ 25μm的POM的行为。P-32的粒径分布与浮游植物的粒径分布相对应，其周转时间约为一周。

Mesocosm experiment using the mesopelagic water from 400m depth of Suruga Bay was carried out from 20 November to 10 December 2002. Autotrophic biomass increased from 0.2μg C1^<-1> to 1.3mg C1^<-1> during the first 7 days of incubation. Nitrate and phosphate were depleted rapidly during Days 7 to 12 of incubation. It was thought that both nutrients-rich condition and low grazing pressure due to the low concentration of predator in the mesopelagic water at initial time caused bloom of autotrophic components. Biomass peak of bacteria, heterotrophic nanoflagellates (HNF) and ciliates occurred between Days 9 and 13 following the peak of autotrophic biomass. These results suggest that organic materials were transferred from autotrophic components to bacteria and subsequently to HNF and ciliates after nitrate was depleted, and then organic materials flowed through the microbial loop. POM (particulate organic matter) was divided in to the different size (>500μm,500〜105,105〜25,and 25〜0.4), and TH-234,Pb-210,Po-210 were measured in each fraction. Th-234 was not detected in dissolved form, while 80% of Th-234 in particulate form was found in size fraction from 0.6 to 500μm. The behavior of Th-234,Pb-210 and Po-210 was due to the behavior of POM with size of 0.4 to 25μm. The size distribution of P-32 is corresponding to the size distribution of phytoplankton, and its turnover time is about one week.