TEMPORAL AND SPATIAL DIFFERENTIATION CHARACTERISTICS OF CHLOROPHYLL A CONCENTRATION IN CHINESE LAKES IN RECENT 40 YEARS
With the rapid development of economy and society,Chinese lakes show different degrees of eutrophication,and the lake ecology is facing severe challenges.Chlorophyll a is an important indicator for evaluating the nutritional status of water bodies,and it reflects the amount of phytoplankton in lakes.Based on the Landsat dataset,the distribution of chlorophyll a concentration in lakes with an area of over 10 km2 in China from 1986 to 2022 was investigated,and the trend of chlorophyll a concentration evolution in various regions was analyzed.Results show that first,there are regional spatial distribution differences in the concentration of chlorophyll a in Chinese lakes.The overall distribution of chlorophyll a concentration is high in the southeast and low in the northwest.About 69％of the lakes are in the light eutrophication state,and about 17％are in the middle eutrophication state.Using 35°N and 100°E as the dividing line,the concentration of chlorophyll a in each region showed a certain variation with latitude and longitude.Secondly,in.the past 40 years,the annual average chlorophyll a concentration of Chinese lakes has been in a slowly fluctuating upward trend,and the time series showed a variation pattern of first decreasing,then increasing,and then decreasing.Among all the lakes,30％of the lakes showed a significant increase in chlorophyll a concentration,24.8％showed a significant decrease,and 45.2％showed no significant change.The overall change is relatively stable,and the coefficient of variation is below the medium fluctuation level.The areas with large fluctuations are located in the Qinghai-Xizang Plateau,the Northeast China,and some lakes in the middle and lower reaches of the Changjiang(Yangtze)River.Thirdly,the spatio-temporal variation of chlorophyll a concentration in each watershed is as follows:in terms of spatial distribution,the inland basin and southwest basin are generally low,while the Zhujiang(Pearl)River basin and those in Southeast China are high.In terms of temporal variation,except for the lakes in Southwest China and inland river basins in which the chlorophyll a concentration is showing a decreasing trend,all other river basins are showing an increasing trend.The chlorophyll a concentration in Chinese lakes shows significant regional differences and temporal trends,which can mainly due to the factors such as regional climate,hydrological conditions,human activities,and land use particularities.Affected by warm and humid climate and strong human activities,the chlorophyll a concentration in lakes in the eastern China is relatively high,while those in the western China has lower temperatures and less precipitation,the chlorophyll a concentration is generally low.Over the past 40 years,due to the combined effects of urbanization,rapid industrialization,and global climate change,the overall concentration of chlorophyll a in Chinese lakes has shown a slow upward trend.
Chinese lakesremote sensingchlorophyll atemporal and spatial differentiation
NETL
NSTL
万方数据
