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A large number of lacustrine sedimentary records indicate that global warming is the main factor leading to significant changes in diatom communities in lakes of the northern hemisphere. However, due to the intensification of human activities since 1850, some scholars have emphasized that the increasing lake trophic level may be the main reason for the changes in diatom communities. The debate is ongoing. In order to avoid falling into the complex relationship between diatom changes and the seasonal cycle that characterizes lakes in mid and high latitudes, we chose a lake located at a low latitude, where the relationship between diatoms and temperature is not indirect but direct. The diatom record spans the past ca. 100 years and reveals that the abundance of Aulacoseira granulata increased from 1900 until 1985, replacing the previously dominant Aulacoseira ambigua. These changes are in agreement with the increasing trend in global temperature. Since 1985, the percentages of the small-celled Discostella stelligera and the benthic diatom Navicula heimansioides have increased, while Aulacoseira granulata has decreased. This latest shift is caused by further global warming. We conclude that warming is the main factor leading to changing diatom communities in Douhu Lake.

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Nonpoint sources of pollution, primarily from agricultural sources, are a major cause of water quality impairment in China. Yet approaches for addressing this issue remain underexplored. This article first introduces the current status of China’s agricultural nonpoint sources pollution.The article then discusses some practical approaches for agricultural nonpoint sources pollution control in terms of China’s current economic development levels and conditions.The article concludes that voluntary programs, command and control programs and economic incentive instruments are feasiable for addressing agricultural nonpoint sources pollution, if such approaches are designed and implemented well.