Dynamics and environmental drivers of the phytoplankton community in the source region of the Yellow River
The source region of the Yellow River is located in the eastern region of the Qinghai-Tibet Plateau and the ecological environment in the basin is fragile. The climate in this area is classified as plateau sub-cold zone,semi-humid and plateau temperate zone,semi-humid. The annual rainfall is approximately 300 mm,and the average annual water temperature is 3.4-7.2 ℃. As the global climate is changing and human activities are increasing,the ecological environment of the basin is confronting great pressure. The protection and restoration of the environment around the Yellow River has become the focus of human society. To explore the characteristics of the phytoplankton community structure and its relationship with environmental factors,two comprehensive investigations were undertaken in the main stem and tributaries of the Yellow River in the spring and summer of 2023,respectively. The total length of the survey site of the river was 1200 km. Phytoplankton samples were collected from 33 survey stations along the source region of the Yellow River. The environmental parameters including water temperature,dissolved oxygen level,conductivity,turbidity,pH,chlorophyll a level,suspended solid levels,flow velocity,river width,transparency,altitude,latitude,and longitude were collected in the field. One liter of water was collected in a polytetrafluoride bottle and returned to the laboratory for analyses of water quality indices,including total nitrogen and total phosphorus levels and the potassium permanganate index. In total,235 species of phytoplankton belonging to seven genera were identified,with an average density and biomass of 182.75×104 cells/L and 55.35×10-3 mg/L,respectively. Diatoms were the dominant species,accounting for 72.31％ of all species. Seasonal changes in species composition and abundance existed,but were not significant. From the perspective of spatial dynamics,the phytoplankton species and their abundance in the main stem proceeded to the tributaries. The number of phytoplankton species was highest in the downstream area,and the average density and biomass of phytoplankton were highest in the middle reaches. The Shannon-Wiener diversity index,Margalef's richness index,and Pielou's evenness index values were 2.87±0.66,6.65±0.94,and 0.77±0.17,respectively. Biodiversity analysis showed that the diversity index values of the phytoplankton community were higher in spring than in summer,and these seasonal differences were highly significant. There were nine dominant species of phytoplankton,mainly belonging to Bacillariophyta. The dominant species in both spring and summer were Fragilaria intermedia,Fragilaria biceps,Synedra ulna,Diatoma moniliforme,and Cymbella turgidula. Correlation analyses between the phytoplankton community structure and environmental factors showed that the influencing factors of the phytoplankton community structure were different in spring and summer in the source region of the Yellow River. The main factors affecting phytoplankton density and biomass in spring were altitude,river width,and flow velocity,while in summer the main factors were the potassium permanganate index value,chlorophyll a level,suspended solid level,and transparency. The results of this study provide an important foundation for scientific decision-making regarding basin ecological environment protection and management in the Yellow River.
the source region of the Yellow Riverphytoplanktoncommunity structurebiodiversity
万方数据
维普
