title: Responses of summer phytoplankton community to drastic environmental changes in the Changjiang (Yangtze River) estuary during the past 50 years.
abstract: The phytoplankton community in the Changjiang Estuary is subject to intensive physical and chemical stresses because of human- and climate-driven changes. We obtained historical data on summer phytoplankton communities from 1959 to 2009 to explore responses to long-term environmental changes. The nitrogen (N) and phosphorus (P) concentrations and ratios (N/P and N/Si) increased because of persistent riverine loading, but silicon (Si) levels remained constant. Climatic changes and extensive water diversions and withdrawals (sediment retention) resulted in a series of physical alterations, including increased temperature, turbidity reduction, and river plume shrinkage. These changes induced a dramatic increase in microalgal biomass (cell density and chlorophyll a) with a decreasing diatom-dinoflagellate ratio, and exacerbated harmful algal blooms. In the past dominant net-collected species were usually chain-forming diatoms; however, more recently, large dinoflagellates and filamentous cyanobacteria dominate. This was not consistent with information from water samples (co-dominated by small dinoflagellates), because of the loss of solitary species collected using a 76-μm net. The dominant species shifted from temperate-subtropical/eurythermal to subtropical-tropical/eurythermal taxa in the warmer water caused by global warming and hydrographic changes. There was also an increased dominance of euryhaline/high-salinity species due to increase in Kuroshio transport and the northward Taiwan Warm Current and reduction in Changjiang Diluted Water. All these changes in phytoplankton communities appear to be closely related to an increase in anthropogenic activities and climatic changes.
authors: State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China; Key Laboratory of Marine Ecosystem and Biogeochemistry, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China; Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Marine College of Ningbo University, Ningbo 315211, PR China.
authors: Zhibing
authors: Z
authors: Jiang
authors: Key Laboratory of Marine Ecosystem and Biogeochemistry, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China.
authors: Jingjing
authors: J
authors: Liu
authors: State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China; Key Laboratory of Marine Ecosystem and Biogeochemistry, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China.
authors: Jianfang
authors: J
authors: Chen
authors: Key Laboratory of Marine Ecosystem and Biogeochemistry, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China.
authors: Quanzhen
authors: Q
authors: Chen
authors: Key Laboratory of Applied Marine Biotechnology, Ministry of Education, Marine College of Ningbo University, Ningbo 315211, PR China.
authors: Xiaojun
authors: X
authors: Yan
authors: State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China.
authors: Jiliang
authors: J
authors: Xuan
authors: State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China; Key Laboratory of Marine Ecosystem and Biogeochemistry, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, PR China. Electronic address: jiangningz@126.com.
authors: Jiangning
authors: J
authors: Zeng
mesh_terms: D044822:Biodiversity; D018533:Biomass; D002681:China; D057231:Climate Change; D063366:Estuaries; D005618:Fresh Water / Q000737:chemistry; D005843:Geography; D019015:Geologic Sediments / Q000737:chemistry; D057097:Harmful Algal Bloom; D006801:Humans; D009584:Nitrogen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D010839:Phytoplankton / Q000254:growth & development*; D054712:Salinity; D012621:Seasons; D013045:Species Specificity; D013696:Temperature; D013997:Time Factors
chemical_list: D010758:Phosphorus; D009584:Nitrogen
keywords: Dam construction; Eutrophication; Global warming; Harmful algal bloom (HAB); Large estuary; Phytoplankton