A Study On The Phytoplankton Diversity In The Lower Reaches Of The Yangtze River

The Yangtze River is the largest river in China.The main stream of the Yangtze River traverses the central part of China from west to east.After accepting Poyang Lake system at the Hukou of Jiangxi Province,the Yangtze River reaches the lower reaches.The lower reaches of the Yangtze River are 938 kilometers long,flowing through Jiangxi,Anhui,Jiangsu,Shanghai,and finally into the East China Sea,with the main tributaries along the south bank of the Qingyi River,the Shuiyang River and the Taihu Lake system which formed by the waters of Dongtiaoxi,Xitiaoxi,Wusong River and Huangpu River.On the north shore,there are Anhui River,Chuhe River and Chaohu River system.The basin area is 120000 square kilometers,which belongs to the subtropical monsoon climate and has four distinct seasons.Phytoplankton is an ecological unit that refers to the tiny plants that live in water in planktons.Usually phytoplankton refers to planktonic algae.Phytoplankton in the lower reaches of the Yangtze River was studied systematically for the first time in order to establish the basic database of plankton resources in the lower reaches of the Yangtze River.At the same time,it enriches the diversity of phytoplankton in the Yangtze River,the diversity of phytoplankton in China and the world.It also provides the basic data of ecological distribution.In October,February,May and August of 2016,406 algae specimens were collected in the lower reaches of the Yangtze River.Microscopic observation and optical microscopic photographs of planktonic algae(except Diatom)in the lower reaches of the Yangtze River were carried out using LMs.The results are as follows:In this study,a total of 270 species of phytoplankton(except Diatom),belonging to 6phyla and 94 genera,were identified.Cyanophyta 21 species and 1 variety in 13 genera,9 species in 6 genera of Chrysophyta,2 species in 2 genera of Xanthophyta,5species in 2 genera of Pyrrophyta,64 species in 6 genera of Euglenophyta,168 species in 65 genera of Chlorophyta.The taxonomic characteristics of each alga were described in detail,with a clear optical microscope photo showing 286 algae pictures in 47 plates.In this study,2 new recorded species and 19 new recorded species were found.Among them,1 of the naked algae gates were found.There are 1 new recorded specie in China,1 new recorded specie in China,2 new recorded genera in China and 17 new recorded species in China.There are 91 species of phytoplankton species reported for the first time in the lower reaches of the Yangtze River.In this study,phytoplankton in different habitats of the lower reaches of the Yangtze River was studied.1)the diversity of phytoplankton in the lower reaches of the Yangtze River is low,and most of the species are concentrated in the lower reaches of the Yangtze River into the estuary and the peripheral rivers.The Anqing-Chizhou reach has the largest number of species,and the Nantong section is the least.2)in different sampling seasons,The species of phytoplankton are also slightly different,the most in spring and the least in autumn.The seasonal distribution of phytoplankton in the estuary is not obvious.The species of Chlorophyta or Phaeophyta are the dominant groups,indicating that the water body of the branch into the estuary is rich in nutrition.3)The species of phytoplankton in the lower reaches of the Yangtze River are abundant,including freshwater species,sea water species and brackish water species.