ABSTRACT
In order to understand species composition and diversity of fish communities in the ecotone between the Yellow Sea and Bohai Sea, we examined species composition and temporal and spatial variations of fish species diversity using the relative importance index (IRI), species diversity index and k dominance curve based on bottom trawl survey data of fish resources in the adjacent waters of the Changshan Islands in October 2016, January, May and August 2017. The results showed that 77 fish species were captured, mainly temperate water fishes, demersal fishes and migratory fishes. The dominant species exhibited obvious seasonal variation. The dominant species in spring and winter were Lophius litulon, and those in summer were pelagic species such as Scomber japonicus and Engraulis japonicus. A total of 46 migratory fish species were found throughout the year. The seasonal species migration indices were all higher than 100, while the species migration index was the largest in autumn. The species diversity index showed high spatial and temporal dynamics, with the highest species richness in spring and the highest Shannon diversity and evenness in autumn. There was a significant negative correlation between species richness and sea surface temperature in summer, significant positive correlations between species richness and depth and bottom temperature in winter, and a significant positive correlation between Shannon diversity index and sea bottom temperature. In short, fish community showed high species diversity, rich migratory species and obvious temporal and spatial heterogeneity in the adjacent waters of the Changshan Islands, which is an ecotone between the Yellow Sea and the Bohai Sea.
Subject(s)
Fishes , Perciformes , Animals , China , Ecosystem , Population Dynamics , SeasonsABSTRACT
We describe a new strategy for aminoarylation of alkenes by copper-catalyzed smiles rearrangement using O-benzoylhydroxylamines as the amine reagent. This method affords various ß-amino amide derivatives possessing a quaternary carbon center with wide functional group tolerance and high regioselectivity. The mechanistic studies indicate that the transformation can involve aminyl radical intermediates under acid-free condition.
ABSTRACT
A mild and facile approach to construct various perfluoroketones via photo-catalyzed difluoroalkylation of difluoroenoxysilanes is developed. The reaction includes a strategy of combination of two fluorine-containing functional groups, which confers the reaction with characteristics like high efficiency, mild conditions, and broad scope. A variety of fluoroalkyl halides including perfluoroalkyl iodides, bromo difluoro esters and amides can be employed as radical precursors. Control experiments indicate that a single-electron transfer pathway may be involved in the reaction.
