Cite this paper:
WANG Yucheng, GUO Xinyu, ZHAO Liang. Simulating the responses of a low-trophic ecosystem in the East China Sea to decadal changes in nutrient load from the Changjiang (Yangtze) River[J]. HaiyangYuHuZhao, 2018, 36(1): 48-61

Simulating the responses of a low-trophic ecosystem in the East China Sea to decadal changes in nutrient load from the Changjiang (Yangtze) River

WANG Yucheng1, GUO Xinyu1,2,3, ZHAO Liang4
1 Center for Marine Environmental Studies, Ehime University, Matsuyama 7908577, Japan;
2 Key Laboratory of Marine Environment and Ecology, Ministry of Education, Ocean University of China, Qingdao 266100, China;
3 College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China;
4 College of Marine and Environmental Sciences, Tianjin University of Science and Technology, Tianjin 300457, China
Using a three-dimensional coupled biophysical model, we simulated the responses of a lowtrophic ecosystem in the East China Sea (ECS) to long-term changes in nutrient load from the Changjiang (Yangtze) River over the period of 1960-2005. Two major factors affected changes in nutrient load:changes in river discharge and the concentration of nutrients in the river water. Increasing or decreasing Changjiang discharge induced different responses in the concentrations of nutrients, phytoplankton, and detritus in the ECS. Changes in dissolved inorganic nitrogen (DIN), silicate (SIL), phytoplankton, and detritus could be identified over a large area of the ECS shelf, but changes in dissolved inorganic phosphate (DIP) were limited to a small area close to the river mouth. The high DIN:DIP and SIL:DIP ratios in the river water were likely associated with the different responses in DIN, DIP, and SIL. As DIP is a candidate limiting nutrient, perturbations in DIP resulting from changes in the Changjiang discharge are quickly consumed through primary production. It is interesting that an increase in the Changjiang discharge did not always lead to an increase in phytoplankton levels in the ECS. Phytoplankton decreases could be found in some areas close to the river mouth. A likely cause of the reduction in phytoplankton was a change in the hydrodynamic field associated with the river plume, although the present model is not suitable for examining the possibility in detail. Increases in DIN and DIP concentrations in the river water primarily led to increases in DIN, DIP, phytoplankton, and detritus levels in the ECS, whereas decreases in the SIL concentration in river water led to lower SIL concentrations in the ECS, indicating that SIL is not a limiting nutrient for photosynthesis, based on our model results from 1960 to 2005. In both of the above-mentioned cases, the sediment accumulation rate of detritus exhibited a large spatial variation near the river mouth, suggesting that core sample data should be carefully interpreted.
Key words:    East China Sea|Changjiang (Yangtze) River|low-trophic ecosystem   
Received: 2016-08-30   Revised: 2016-10-15
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Bai Y, He X Q, Pan D L, Chen C T A, Kang Y, Chen X Y, Cai W J. 2014. Summertime Changjiang River plume variation during 1998-2010. J. Geophys. Res., 119(9):6 238-6 257.
Beardsley R C, Limeburner R, Yu H, Cannon G A. 1985. Discharge of the Changjiang (Yangtze River) into the East China Sea. Cont. Shelf Res., 4(1-2):57-76.
Chen C T A, Wang S L. 1999. Carbon, alkalinity and nutrient budgets on the East China Sea continental shelf. J. Geophys. Res., 104(C9):20 675-20 686.
Chen C T A. 1996. The Kuroshio intermediate water is the major source of nutrients on the East China Sea continental shelf. Oceanol. Acta, 19(5):523-527.
Chen C T A. 2009. Chemical and physical fronts in the Bohai, Yellow and East China seas. J. Mar. Syst., 78(3):394-410.
Chung S W, Jan S, Liu K K. 2001. Nutrient fluxes through the Taiwan Strait in spring and summer 1999. J. Oceanogr., 57(1):47-53.
Deng B, Zhang J, Wu Y. 2006. Recent sediment accumulation and carbon burial in the East China Sea. Global Biogeochem. Cycles, 20(3):GB3014.
Duan S W, Zhang S. 2001. Material fluxes and their variations from the Changjiang River into the sea. In:Zhang S, Shen H T eds. Land-Sea Interaction in Estuaries of the Changjiang River, Zhujiang River and their Adjacent Sea Areas. China Ocean Press, Beijing, China. p.10-26. (in Chinese)
Gong G Q, Wen Y H, Wang B W, Liu G J. 2003. Seasonal variation of chlorophyll a concentration, primary production and environmental conditions in the subtropical East China Sea. Deep Sea Res. Ⅱ Top. Stud. Oceanogr., 50(6-7):1 219-1 236.
Guo X Y, Hukuda H, Miyazawa Y, Yamagata T. 2003. A triply nested ocean model for simulating the Kuroshio-roles of horizontal resolution on JEBAR. J. Phys. Oceanogr., 33(1):146-169.
Kim T W, Lee K, Najjar R G, Jeong H D, Jeong H J. 2011. Increasing N abundance in the northwestern Pacific Ocean due to atmospheric nitrogen deposition. Science, 334(6055):505-509.
Li M T, Xu K Q, Watanabe M, Chen Z Y. 2007. Long-term variations in dissolved silicate, nitrogen, and phosphorus flux from the Yangtze River into the East China Sea and impacts on estuarine ecosystem. Estuar. Coast. Shelf Sci., 71(1-2):3-12.
Liu S M, Hong G H, Zhang J, Ye X W, Jiang X L. 2009. Nutrient budgets for large Chinese estuaries. Biogeosciences, 6(10):2 245-2 263.
Morimoto A, Watanabe A, Onitsuka G, Takikawa T, Moku M, Yanagi T. 2012. Interannual variations in material transport through the eastern channel of the Tsushima/Korea Straits. Prog. Oceanogr., 105:38-46.
Skogen M D, Søiland H. 1998. A user's guide to NORWECOM v2.0. A coupled 3 dimensional physical chemical biological ocean-model. The NORWegian Ecological Model system. Bergen, Institute of Marine Research, 42, Technical Report Fisken og Havet 18/98.
Skogen M D, Svendsen E, Berntsen J, Aksnes D, Ulvestad K B. 1995. Modelling the primary production in the North Sea using a coupled three-dimensional physical-chemicalbiological ocean model. Estuar. Coast. Shelf Sci., 41(5):545-565.
Wang B D. 2006. Cultural eutrophication in the Changjiang(Yangtze River) plume:history and perspective. Estuar. Coast. Shelf Sci., 69(3-4):471-477.
Wang Q, Guo X Y, Takeoka H. 2008. Seasonal variations of the Yellow River plume in the Bohai Sea:a model study. J. Geophys. Res., 113(C8):C08046.
Yamaguchi H, Ishizaka J, Siswanto E, Baek Son Y, Yoo S, Kiyomoto Y. 2013. Seasonal and spring interannual variations in satellite-observed chlorophyll-a in the Yellow and East China Seas:new datasets with reduced interference from high concentration of resuspended sediment. Cont. Shelf Res., 59:1-9.
Zhang J. 1996. Nutrient elements in large Chinese estuaries. Cont. Shelf Res., 16(8):1 023-1 045.
Zhang X L, Fan D J, Wang H J, Yang Z S. 2014. Water discharge variability of Changjiang (Yangtze) and Huanghe (Yellow) Rivers and its response to climatic changes. Chin. J. Oceanogr. Limnol., 32(6):1 392-1 405.
Zhao L, Guo X Y. 2011. Influence of cross-shelf water transport on nutrients and phytoplankton in the East China Sea:a model study. Ocean Sci., 7(1):27-43.