Zooplanktons are important food organisms of fishes,and their spatial and temporal distribution pattern has an important influence on the growth and reproduction of fishes in local habitats.The Yangtze River Estuary o...Zooplanktons are important food organisms of fishes,and their spatial and temporal distribution pattern has an important influence on the growth and reproduction of fishes in local habitats.The Yangtze River Estuary of China is rich in fishery resources,but the knowledge on the distribution pattern of zooplankton in this area is still very limited.The diel vertical migration(DVM)patterns and seasonal variations of the crustacean community,and their relationship with environmental factors were investigated in the south branch of the Yangtze Estuary,from June 2017 to May 2018.The results showed that the dispersion patterns of dominant crustacean taxa in the Yangtze Estuary were mostly aggregated.Migration amplitudes of crustacean were greater in spring and summer than in autumn and winter,and different migratory patterns occurred in different seasons.Sinocalanus dorrii,Schmackeria inopinus,Mesmackeria leuckarti,Bosmina longirostris,and B.fatalis,unlike S.forbesi,showed a significant DVM.The DVM patterns of crustaceans was possibly influenced by light dentisy,temperature,and total dissolved solids in the water column,and the fish predation effect;whereas,the nutrient concentration and pH were not supposed to be key factors.展开更多
Channel evolution and depo-center migrations in braided reaches are significantly influenced by variations in runoff.This study examines the effect of runoff variations on the erosion-deposition patterns and depocente...Channel evolution and depo-center migrations in braided reaches are significantly influenced by variations in runoff.This study examines the effect of runoff variations on the erosion-deposition patterns and depocenter movements within branching channels of the near-estuary reach of the Yangtze River.We assume that variations in annual mean duration days of runoff discharges,ebb partition ratios in branching channels,and the erosional/depositional rates of entire channels and sub-reaches are representative of variations in runoff intensity,flow dynamics in branching channels,and morphological features in the channels.Our results show that the north region of Fujiangsha Waterway,the Liuhaisha branch of Rugaosha Waterway,the west branch of Tongzhousha Waterway,and the west branch of Langshansha Waterway experience deposition or reduced erosion under low runoff intensity,and erosion or reduced deposition under high runoff intensity,with the depocenters moving upstream and downstream,respectively.Other waterway branches undergo opposite trends in erosion-deposition patterns and depo-center movements as the runoff changes.These morphological changes may be associated with trends in ebb partition ratio as the runoff discharge rises and falls.By flattening the intra-annual distribution of runoff discharge,dam construction in the Yangtze Basin has altered the ebb partition ratios in waterway branches,affecting their erosion-deposition patterns and depo-center movements.Present trends are likely to continue into the future due to the succession of large cascade dams under construction along the upper Yangtze and ongoing climate change.展开更多
基金funded by the Science and Technology Commission of Shanghai Municipality(19050501900).
文摘Zooplanktons are important food organisms of fishes,and their spatial and temporal distribution pattern has an important influence on the growth and reproduction of fishes in local habitats.The Yangtze River Estuary of China is rich in fishery resources,but the knowledge on the distribution pattern of zooplankton in this area is still very limited.The diel vertical migration(DVM)patterns and seasonal variations of the crustacean community,and their relationship with environmental factors were investigated in the south branch of the Yangtze Estuary,from June 2017 to May 2018.The results showed that the dispersion patterns of dominant crustacean taxa in the Yangtze Estuary were mostly aggregated.Migration amplitudes of crustacean were greater in spring and summer than in autumn and winter,and different migratory patterns occurred in different seasons.Sinocalanus dorrii,Schmackeria inopinus,Mesmackeria leuckarti,Bosmina longirostris,and B.fatalis,unlike S.forbesi,showed a significant DVM.The DVM patterns of crustaceans was possibly influenced by light dentisy,temperature,and total dissolved solids in the water column,and the fish predation effect;whereas,the nutrient concentration and pH were not supposed to be key factors.
基金This research was supported by open funding of the Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province(No.2019SS06)the National Key Research and Development Program of China(Nos.2018YFC0407201 and 2016YFC0402306)Scientific Research Project of Hunan Provincial Department of Education(No.16C0055).
文摘Channel evolution and depo-center migrations in braided reaches are significantly influenced by variations in runoff.This study examines the effect of runoff variations on the erosion-deposition patterns and depocenter movements within branching channels of the near-estuary reach of the Yangtze River.We assume that variations in annual mean duration days of runoff discharges,ebb partition ratios in branching channels,and the erosional/depositional rates of entire channels and sub-reaches are representative of variations in runoff intensity,flow dynamics in branching channels,and morphological features in the channels.Our results show that the north region of Fujiangsha Waterway,the Liuhaisha branch of Rugaosha Waterway,the west branch of Tongzhousha Waterway,and the west branch of Langshansha Waterway experience deposition or reduced erosion under low runoff intensity,and erosion or reduced deposition under high runoff intensity,with the depocenters moving upstream and downstream,respectively.Other waterway branches undergo opposite trends in erosion-deposition patterns and depo-center movements as the runoff changes.These morphological changes may be associated with trends in ebb partition ratio as the runoff discharge rises and falls.By flattening the intra-annual distribution of runoff discharge,dam construction in the Yangtze Basin has altered the ebb partition ratios in waterway branches,affecting their erosion-deposition patterns and depo-center movements.Present trends are likely to continue into the future due to the succession of large cascade dams under construction along the upper Yangtze and ongoing climate change.