下降状态 meaning in English

retrogradation

Although the natural growth rate is low these years , at the next birth flood tide , it will show higher
在近几年人口自然增长率呈下降状态，但在下一个生育高峰期时又会表现出较高的自然增长率。
6 . the biodiversity of phytoplankton had risen slightly since 1990 ' s , but the biodiversity of zooplankton , as a key link in the food chain , had been falling in the same time
胶州湾的浮游植物多样性指数虽然自90年代以来处于上升趋势，但作为食物链中重要环节的浮游动物的多样性指数却处于持续下降状态。
Which provides accesses to the data files by " select " , " query " , " draw " , and " organize " as well powerful analytical tools including statistics and time series analysis . using the above data base , the author looked into the long - term changes in nutrients , phytoplankton , and examined the impact of socio - economical factors in the surrounding area on the bay . the following are the major outputs of this study
研究还发现胶州湾海域亚硝酸氮、硝酸氮和氨氮自20世纪60年代以来都有了大幅度的上升，磷的含量则在80年代达到最高， 90年代以来略有下降；而胶州湾海域硅酸盐的含量自80年代以来呈现持续下降状态， 90年代比80年代降低了63 . 6 。