Spatial and temporal variations of chlorophyll-a concentration from 2009 to 2012 in Poyang Lake, China

Abstract

Water eutrophication in Poyang Lake, the largest freshwater lake in China, has been considered to be an obstacle to aquatic environment protection and regional sustainable development. Chlorophyll-a concentration is one of the most important indices of water eutrophication. This paper builds seasonal chlorophyll-a concentration retrieval models using a semi-analytical model. Quarterly distributions of chlorophyll-a concentration from 2009 to 2012 are explored using multi-spectra data from a moderate-resolution imaging spectroradiometer (MODIS). The correlation coefficient of the retrieval models primarily ranged from 0.6 to 0.9. The results show that the chlorophyll-a concentration in Poyang Lake has significant seasonality characteristics that present low values in the winter and spring, and present relatively high values in the summer and autumn; this report also presents an obvious, increasing trend of inter-annual variability from 2009 to 2012. The spatial distribution of the chlorophyll-a concentration has regional differences that give relatively high values adjacent to the shore in the north area of Poyang Lake, in the flow in river entries, and in the main channel area in the central and south areas of Poyang Lake. The natural hydrology features have a close relationship with the variation in the chlorophyll-a concentration. Intensive human activities are the main driving forces for the increasing chlorophyll-a concentration.

Characteristics of phytoplankton community and water net primary productivity response to the nutrient status of the Poyang Lake and Gan River, China

“…A comparative analysis of phytoplankton and associative nutrients from which to ascertain the critical influencing factors of phytoplankton growth and development to establish a healthy, stable aquatic ecosystem could provide a scientific basis for long‐term research. Anthropogenic nutrient loading to aquatic ecosystems can influence the structure and function of phytoplankton communities (Browning et al, ); nevertheless, phytoplankton dynamics are not only affected by nutrients but are also affected by other factors, such as strong hydrodynamic conditions (Cao, Gao, Chu, & Wang, ; Cao, Liu, Chu, & Wang, ;Cao, Wang, et al, ; Wu, Lai, et al, ), high suspended solid (SS) concentrations (Cao, Wang, et al, ; Wu, Lai, et al, ), depth (Wu et al, ), transparency (Cao, Chu, et al, ; Wu et al, ), sunlight (Wu, Lai, et al, ), water temperature (Liang et al, ), and the radiant energy (Lewis, ; Wang et al, ). Although the environmental factors mentioned above have positive or negative effects on the structure, productivity, dynamics, and succession of phytoplankton community, nutrients play a key role in the growth of phytoplankton.…”

“…Primary productivity is dependent upon phytoplankton biomass, regulated by import, export, mortality, nutrient supply, and growth rate (Cloern, Foster, & Kleckner, ), and the phytoplankton growth rate is affected by sunlight (Wu, Lai, et al, ), temperature (Liang et al, ), water level (Cao, Wang, et al, ; Pęczuła & Szczurowska, ), flow velocity (Cao, Chu, et al, ), and nutrient concentration (Wang et al, ). In this study, we discussed the effects of nutrient and phytoplankton abundance on phytoplankton primary productivity.…”

“…Primary production, which represents phytoplankton biomass and growth rates (Wang et al, ), is sensitive to environmental change (Wu, He, et al, ). It is mainly regulated by various factors that include incident irradiance (Lewis, ; Wang et al, ), ice cover (Lewis, ), nonalgal light attenuation (Deng et al, ; Wu, Lai, Zhang, Cai, & Chen, ), mixing depth (Wu et al, ), temperature (Liang et al, ), and the nutrient supply (Browning et al, ; Dou, Tang, Yang, & Wang, ; Hagstrom & Levin, ; Ke, Tan, Ma, Huang, & Wang, ; Li, Ge, Wang, Zhou, & Hu, ; Liu et al, ; Wang et al, ; Wilkerson, Dugdale, Parker, Blaser, & Pimenta, ; Yin, Liu, & Harrison, ), especially for nutrient inputs that have a significant effect on phytoplankton growth and development as well as the biogeochemical cycles of watersheds (Browning et al, ; Li et al, ; Moore et al, ; Wen et al, ). In addition, nutrient inputs, particularly nitrogen (N) and phosphorus (P), to freshwater ecosystems have continued to increase due to progressively increasing anthropogenic activities resulting from rising populations, broadening economic development, and the greater demand for food and energy production in recent years (Cao, Wang, Liao, Sun, & Huang, ; Wilkerson et al, ).…”

“…The environmental quality of water has been deteriorating in recent years under pressure of economic development in Poyang Lake Basin including Poyang Lake Area and the Gan River, which are under serious threat of eutrophication. The Gan River is the largest tributary of Poyang Lake, whose streamflow accounts for approximately 46.6% of its water, making the river a major source of the lake's pollution (Wang et al, ). Sand sediment deposition occurs in the Gan River throughout the year.…”

A MODIS-Based Retrieval Model of Suspended Particulate Matter Concentration for the Two Largest Freshwater Lakes in China

“…The MOD09GQ product contains two 250 m bands at 645 and 858 nm, and the MOD09GA stores seven 500 m or 1 km bands centred at 645, 858, 470, 555, 1240, 1640, and 2130 nm [45]. Considering the uncertainty of current atmospheric algorithms for case-II waters, the MOD09GQ and MOD09GA images-which have been frequently used by Wang et al [46], Ayana et al [47], Chen et al [15], Doxaran et al [26], and Alcântara et al [48]-were employed in this study directly.…”