Modeling Analysis Of The Main Factures And Annual Cycling Of New Production And The Contribution Of Microbial Loop In Yellow Sea Cold Water Mass

The Yellow Sea Cold Water Mass (YSCWM), as an important oceanic phenomenon in the marginal sea of China, is one of the research focus of oceanographers for long time. Though great achievements have been achieved in physical and biochemical oceanography in the YSCWM, the numerical studies of ecosystem dynamics remain scarce. The main purpose of this paper is to explore the seasonal variation of the vertical structure of each variable and the flow characteristics of matter and energy in the ecosystem of the YSCWM based on one-dimensional coupled pelagic-benthic box model. The issues of primary productivity, new production, planktonic ecological efficiency and the impact of microbial loop will be analyzed in detail, to better the understanding of the eco-dynamics in the Yellow Sea.The basic ecosystem characters in the YSCWM are outlined according to former studies and observation in the Yellow Sea and the East China Sea in the first part of this paper. Then the feasibility of using Dobson and Smith model to calculate daily sea-surface solar radiation in the Yellow Sea is tested, which provide assurance for the ecosystem numerical study with lacking of solar radiation observation on the ocean surface. The simulated results of primary productivity and new production in the YSCWM are analyzed in the following part. The last part illustrates that the microbial food loop plays an important role in the course of zooplankton production in the region of low primary productivity. The last two parts is the emphasis of this paper.The model is divided into three boxes according to the depths of thermocline and euphotic layer. All the three boxes contain pelagic submodel which includes seven state variables such as phytoplankton (P), zooplankton (Z), particle organic carbon (POC), dissolved organic carbon (DOC), dissolved oxygen (DO), total inorganic nitrogen (TIN) and total inorganic phosphate (TIP). Besides, the lower box containsthe benthic submodel which includes six variables such as macrobenthos (MacroB), meiobenthos (MeioB), benthic bacteria (Bbac), detritus (Det), total benthic inorganic nitrogen (Btin) and total benthic inorganic phosphate (Btip). The pelagic-benthic coupling is realized by the deposition of phytoplankton and POC into detritus and the transportation of nutrient elements from the bottom to the pelagic. In this model, the effect of microbial loop is considered in a parameterization way. The vertical flux between compartments of the model system is also taken into account.The seasonal variation of each variable in the YSCWM ecosystem is simulated by the coupled pelagic-benthic model, and the results matches well with the observational data and the related literatures, which indicated that the model could depicts the main characters of seasonal variation in the YSCWM ecosystem. The relationship between each variable and the ecologic difference between different layers are simulated reasonably. Generally, the model is competent for the simulation of matter and energy flow characteristics of the ecosystem in the YSCMW.Through the simulation and analysis to the primary productivity and new production in the YSCWM, the annual mean primary productivity estimated as 239mgCm-2d-1, and f-ratio is calculated about 33% according to analyze the origin ofinorganic nitrogen. So the new production is about 28.8 mgCm-2 d-1. The result also reveals that, in the period of time when the Cold Water Mass exists, the nutrient is deficient so that the production of the phytoplankton is restricted, just an insignificant bloom appears in the late fall. However, in this period, the biomass of zooplankton is in the same order as the phytoplankton and the values are relatively close, In the area of YSCWM, the simulated planktonic ecological efficiency is as high as 0.47. Therefore, the microbial loop plays a crucial role in the cycle flow of the matter and energy. Besides, the simulation results also show that 60% of the organic carbon of zooplankton growing requires is supplied by the microbial loop. The contribution of POC to the zooplankton production is less than the phytoplankton. These three energy flows have obvious seasonal variability. Compared with the observation and the literatures, it is found that the simulation results of the model are reasonable andauthentic.