Interdecadal variability in ecosystem health of Changjiang (Yangtze) River estuary using estuarine biotic integrity index

Ichthyoplankton samples were collected from Changjiang(Yangtze)River estuary in May 2016.Species composition was studied by DNA barcoding and morphological identification.To make better use of the estuarine biotic integrity index(EBI)to assess the ecosystem health of the Changjiang River estuary over the past 30 years,we collected the data of a spring ichthyoplankton survey in the estuary from 1986 to 2016.The EBI was calculated using 12 evaluation metrics,namely,the number of total ichthyoplankton species,estuarine spawning species,estuarine nursery species,estuarine resident species,benthic species,pelagic species,and intolerant species,and the percentages of tolerant species,omnivores,insectivores,carnivores,and natural hybrid species.EBI was calculated in spring in four periods(1986,1999,2007,and 2016)by assigning points of 1,3 or 5,giving values of 50,38,36,and 32,respectively,corresponding to“Good”,“Fair-Poor”,“Fair-Poor”,and“Poor”EBI levels,respectively.Changes in species composition were the primary reason for the significant decreases in EBI between 1986 and 1999,and for the large differences between 1986 and 2007 and between 2007 and 2016.The changes in species composition were influenced by declines in ichthyoplankton species,pollution sensitive species,estuarine nursery species and estuarine sedentary species,and an increase in pollution resistant species.An analysis of EBI interdecadal variability showed that the health status of the Changjiang River estuary ecosystem over the last 30 years first declined and then stabilized at a lower level.This result further settled the argument for urgent protection and restoration of the Changjiang River estuary.

Study on Jellyfish Outbreaks and Their Monitoring and Control Technology in the Yellow Sea and the Northern East China Sea

Jellyfish outbreaks have become a new type of marine ecological disasters,and have great influence on the structure and function balance of marine ecosystems,fishery resources,production safety of coastal power plants,marine landscape and tourism.In recent years,the Yellow Sea and the northern East China Sea are the high risk areas of jellyfish outbreaks.In this paper,the research results of jellyfish outbreaks in the Yellow Sea and the northern East China Sea are summarized,and the species composition,distribution,life-history characteristics and hazards of jellyfish outbreaks are described.Meanwhile,the possible causes of jellyfish outbreaks are analyzed,and the monitoring and control technology of jellyfish disasters are discussed.It will provide a scientific basis for the monitoring,management,and emergency disposal of jellyfish disasters.

Analysis of a Synechococcus sp. Bloom in the East China Sea and Its Causes

In the spring of 2007,a Synechococcus sp. bloom was monitored in station A1( 30° N,123° E) in the East China Sea. The abundance of Synechococcus sp. was nearly 2×10~6 cells/ml,and the contribution of Synechococcus sp. to chlorophyll a was nearly 90%. According to the abundance of Synechococcus sp. in the East China Sea and adjacent Changjiang River estuary in the past tow decades,the main reasons why Synechococcus sp. could form a bloom are listed below: the rising level of nutrients and the further eutrophication of the water body provided sufficient nutrients for Synechococcus sp.;with the global warming,the sea water temperature in the East China Sea rose continuously;the number of major predator heterotrophic flagellates was at a low level,reducing predation pressure.