Study on the function of carbon transport by heterotrophic dinoflagellates

硅藻在深海固碳中起着重要作用，即，生物泵硅藻水华的命运在很大程度上受细胞下沉、硅藻食草动物粪便沉淀或上层浮游化的影响。为了了解硅藻的命运，人们对大型浮游动物摄食硅藻进行了许多研究。另一方面，生物学和生态学的其他硅藻饲料，异养甲藻，是有限的，甲藻的作用，对碳封存是未知的。本研究对甲藻摄食硅藻及其固碳作用进行了研究，在亚北极太平洋海域发现了四种以浮游生物为食的异养甲藻，其中包括Gyrodinium sp.和Gymatrium sp.。它们在微型浮游动物组合中的贡献一般较低。，经常缺席。硅藻水华站生物量较高。异养菌的贡献 ...更多信息 在Oyashio地区，卵鞭毛虫的数量达到总微型浮游动物的20%，碳生物量达到60%。在西部亚北极环流的中心区域，在非水华状态下，它们的贡献为10%，在水华期间增加到50%（20.1 mgC m^<-3>）。这表明，异养甲藻的动态在很大程度上取决于硅藻密度。最大摄食速率为532 mgC·m^<-3>d^<-1>.数学模拟表明，异养甲藻有可能在亚北极环流西部硅藻水华期间摄食所有硅藻生产物.放牧对碳转运的重要性主要受甲藻初始细胞密度和捕食者密度的影响。在甲藻初始密度较低或捕食性天敌密度较高的情况下，甲藻的生物量一般在1-4周内不会达到足以影响硅藻水华的程度。这表明，当桡足类生长期开始的时间早于硅藻水华发生时，桡足类对甲藻的选择性摄食会降低甲藻的种群规模。这些结果表明，春季硅藻、碳和营养盐的动态受食物网组成的影响很大，本研究揭示了异养甲藻的生态学特征及其对碳和生源元素循环的影响，这是以前所知甚少的。然而，目前还不清楚的食物网动力学和生态地球化学循环的作用，由于其大的水平和时间变化的丰度。为了建立包括甲藻在内的生态系统模型，了解其在生态系统和生态地球化学循环中的作用，需要进一步研究异养甲藻的生理和生物学特性。少

Diatoms play an important role jn the carbon sequestration to the deep sea, i.e., biological pump. The fate of diatom bloom is largely influenced by the cell sinking, sinking as faecal pellet of diatom grazer, or remineralization in the epipelagic layer. In order to understand the fate, many studies on the macrozooplankton feeding on diatoms has been carried out. On the other hand, biology and ecology of the other diatom feeder, heterotrophic dinoflagellates, are limited, and the role of the dinoflagellates on carbon sequestration is unknown. In this study, we investigated on the diatom grazing by dinoflagellates and the role on carbon sequestration.We found 4 diatom-feeding heterotrophic dinoflagellates, such as Gyrodinium sp. , in the genus of Gyrodinium and Gymnodinium in the subarctic Pacific. Their contribution in microzooplankton assemblage is generally low. , and often absent. The high biomass was observed in the diatom blooming station. The contribution of the heterotrophic din … More oflagellates reached 20% of total microzooplankton in number in the Oyashio region and 60% in the carbon biomass. In the central region of the western subarctic gyre, their contribution was 10% in weight at the non-bloom status, and it increased to 50%(20.1 mgC m^<-3>) during the bloom. These indicate that the dynamics of the heterotrophic dinoflagellates is largely dependent on the diatom density. The maximum ingestion rate observed was 532 mgC m^<-3> d^<-1>.The mathematical simulation showed that the heterotrophic dinoflagellates had potential to graze down all the diatom production during diatom bloom in the western subarctic Gyre. The importance of the grazing on the carbon transport is largely influenced by the initial cell density of the dinoflagellate and the predator density. In the case of the low initial density of the dinoflagellates or high predator density, the biomass of the dinoflagellates does not reach to high enough to impact the diatom bloom within the general duration of the event of 1-4 weeks It is suggested that the selective feeding of copepods on the dinoflagellates decrease the population size when the timing of copepod growth period initiate earlier than the diatom bloom. These results indicate that the diatom, carbon and nutrient dynamics in spring are crucially influenced by the food-web components.This study demonstrate the ecological characteristics of the heterotrophic dinoflagellates and their influence of carbon and biogenic elemental cycling which are little know previously. It is, however, still unclear the roles on the food-web dynamics and biogeochemical cycling due to their large horizontal and temporal variations in their abundance. We need further studies on physiological and biological characteristics of the heterotrophic dinoflagellates in order to develop the ecosystem model including the dinoflagellate and to understand their role in the ecosystem and biogeochemical cycling. Less