In　order　to　discover　the　plankton　distribution　patterns　and　its　relationship　with　environment　gradients　and　hydrological　connectivity　in　wetlands,　samples　from　Yellow　River　Delta　that　span　gradients　in　salinity　and　hydrological　connectivity　were　analyzed　in　this　study.　Plankton　community　composition,　abundance　and　biomass　were　determined　and　correlated　with　water　variables　and　hydrological　connectivity　indexes　to　gain　information　about　the　forces　that　structure　the　plankton　community　in　this　dynamic　environment.　Phytoplankton　with　a　total　of　88　species　and　zooplankton　with　a　total　of　49　species　were　observed　at　an　average　abundance　of　4.11　x　10(7)　cells/L　and　951.27　ind./L,　respectively.　Predominant　species　were　Merismopedia　minima　G.Beck/Merismopedia　elegans　A.　Braun　ex　Razing　(Cyanobacteria)　and　Trichocerca　pusilla　(Jennings)　(Rotifera),　accounting　for　over　10%　of　the　total　abundance　of　phytoplankton　and　zooplankton,　respectively.　The　dominant　species　of　phytoplankton　communities　were　shifted　from　freshwater　Chlorophyta　(e.g.,　Oocystis　sp.)　to　brackish　Cyanobacteria　(e.g.,　Merismopedia　minima　and　Merismopedia　eleguns)　and　then　to　marine　cyanobacterium　(e.g.,　Oscillatoria　sp.　and　Pseudoanabaena　sp.);　That　shift　in　zooplankton　community　was　from　freshwater　rotifers　Trichocerca　pusilla　and　Polyarthra　trigla　(Ehrenberg)　to　brackish　rotifer　Brachionus　urceus　(Linnaeus)　and　copepod　Thermocyclops　spp.　and　then　to　marine　copepods　Sinocalanus　spp.　and　Microsetella　spp.　toward　the　river　mouth.　However,　abundance,　biomass　and　community　similarity　of　plankton　decreased　with　increasing　water　salinity　and　decreasing　hydrological　connectivity　from　upper　reaches　to　river　mouth.　Salinity　gradient　could　be　major　force　for　the　shift　of　plankton　community　while　the　increasing　hydrological　connectivity　between　freshwater　and　saline　habitats　promoted　the　similarity　of　plankton　distribution　patterns　within　the　wetland　network.　(C)　2020　European　Regional　Centre　for　Ecohydrology　of　the　Polish　Academy　of　Sciences.　Published　by　Elsevier　B.V.　All　rights　reserved.