Lakes provide critical resources for humankind, such as drinking water, food, biodiversity, and transportation. The dual effects of climate change (e.g., shifts in temperature and precipitation regimes) and human activities significantly alter lake environments. A lot of studies monitored individual water quality indicators, yet a comprehensive assessment of the prevalence of shifts in lake conditions and relevant drivers needs further investigation. 
　　From the perspective of lake optics, the interaction of optically active constituents in the water with solar radiation makes lakes on the Earth colorful. In general, lake color is related to productivity, water quality, and ecological state; hence, the influences of climate and human activities on lake environments can be reflected in the water color, to some extent. Compared with a single water quality parameter, lake water color can reflect the comprehensive state change of the lake environment. However, a systematic study on the spatial and temporal trends of shifts in lake color across the China is missing, and, more in general, the relevant factors regulating the long-term changes in lake color, are unknown. 
　　In recent, Dr. CAO Zhigang from Prof. MA Ronghua’s group at the Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, along with their collaborators, conducted a comprehensive examination of color in 2550 Chinese lakes from 1984 to 2021 using Landsat missions and revealed the spatial and temporal patterns of shifts in lake color as well as the relations to the climate and human activities. 
　　Their findings were published in Geophysical Research Letters on April 26, 2023. 
　　“In the past 40 years, the blue lakes in western China became bluer, and the green-yellow lakes in eastern China shifted to greener colors,” said Dr. CAO. 
　　Whether blue lakes in the western area or non-blue (green and yellow) lakes in the eastern area, the results find that declines in visual wavelength have been widespread. The decrease in visual wavelength of color is found in 1723 lakes (68%) (mean changing rate: -8 nm/decade). Lakes in the Tibetan Plateau had larger declines in wavelength than lakes in other areas. 
　　“The climate and the human activities varied in different areas of China; as such, the controls of climate and humans on changing patterns of lake colors are heterogeneous across China, ” said Prof. MA. 
　　Most of lakes in western China (e.g., Tibetan Plateau) are blue. The bluer color is mainly related to the higher temperature and rainfall, which also resulted in lake expansion and elevated water clarity there. 
　　The lakes in eastern China (e.g., Yangtze River plain) are often “yellow-green”. With the decrease in wind speed over the past decades, the resuspension of sediments, which usually relates to the lake turbidity, was weakened. Likewise, more forest and grassland around the lake reduced the substances flowing into the lakes. These processes reduced the reduced sediments in the surface water and made the lake color shift to a green direction. In Lake Taihu and Chaohu, where the cyanobacterial blooms frequently break out, the trends of “greener” colors are more significant. 
　　Link: https://doi.org/10.1029/2023GL103225
　　Contact 
　　TAN Lei 
　　Nanjing Institute of Geography and Limnology 
　　E-mail: ltan@niglas.ac.cn

　　Methane (CH4) is a potent greenhouse gas with a global warming potential 28-34 times that of carbon dioxide on a centennial time scale. Microbial CH4 oxidation acts as a biofilter and prevents over 90% of CH4 reaching the atmosphere. 
　　Traditionally, aerobic CH4-oxidizing bacteria (MOB) is O2-dependent to grow on CH4 as their sole source of carbon and energy. Increasing studies have shown that MOB are present and even active in anoxic environments, without O2 utilized as an electron acceptor by them, but their survival strategy and ecological contribution are still enigmatic. 
　　Recently, researchers led by Dr. LI Biao from Prof. WU Qinglong’s team at Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences (NIGLAS), along with their collaborators, have investigated the survival strategies of MOB under anoxic conditions. 
　　Their findings were published in Water Research on 3 March 2023. 
　　After two-year enrichment, the researchers obtained an enriched consortium dominated by γ-MOB, Methylomonas and several other several heterotrophic bacteria, but without anaerobic methanotrophs. 
　　They found the MOB consortium can couple CH4 oxidation and Fe(III) reduction under anoxia with the help of electron shuttles such as riboflavin. Within the MOB consortium, MOB transformed CH4 to low molecular weight organic matter such as acetate for consortium bacteria as a carbon source, while the latter secrete riboflavin to facilitate extracellular electron transfer. 
　　“A metabolic flexibility was observed in this conventional considered O2-depentend microbe, MOB. Given that iron is the fourth most abundant element on Earth and generally abundant in lacustrine sediment, using ferric oxides as electron acceptor maybe a critical lifestyle for MOB and an important CH4 sink on early Earth, where anoxic conditions are ubiquitously present.” said Dr. LI. 
　　In the in situ anoxic sediments, multiple kinds of microbes associated to the consortium including Methylomonas were transcriptionally active. Moreover, Fe(III) reduction coupled to CH4 oxidation mediated by the MOB consortium reduced 40.3% of the CH4 emission in the iron-rich sediments. 
　　“There are many iron-rich areas in Southern China, MOB in these iron-rich area may play critical roles in mitigating CH4 emission even under anoxia there. Our study unveils how MOBs survive under anoxia and expands the knowledge of this previously overlooked CH4 sink in iron-rich sediments,” said Dr. LI. 
　　Schematic diagram of CH4 metabolism mediated by MOB under oxic and anoxic conditions. (Image by LI Biao)
　　Link: https://www.sciencedirect.com/science/article/pii/S0043135423002683 (online on Mar. 3 2023) 
　　Contact 
　　TAN Lei 
　　Nanjing Institute of Geography and Limnology 
　　E-mail: ltan@niglas.ac.cn

　　Invasion by introduced species has been listed as one of the main threats to freshwater biodiversity worldwide. Invasive species have resulted in reduced abundance and diversity of native species in invaded natural habitats and caused harm to human society. However, the mechanisms of plant invasion in natural habitats remain controversial. 
　　In the late 1980s, Carolina fanwort (Cabomba caroliniana) was introduced to China as an aquarium plant because of its beautiful fan-shaped dissected leaves, and soon escaped as a serious invasive threat to freshwater ecosystems. It was listed as an invasive species in the 4th patch of ‘the List of Alien Invasive Species in China's Natural Ecosystem’ by the Ministry of Ecology and Environment of China in 2016. 
　　Researchers, led by Dr. HUANG Xiaolong, from Prof. LI Kuanyi's team from the Nanjing Institute of Geography and Limnology of the Chinese Academy of Sciences, along with their international collaborators, have investigated why C. caroliniana is so successful in invading China through field investigations and a mesocosm experiment. 
　　Their findings were published in the Diversity and Distributions on Mar. 15, 2023. 
　　In the field investigations, seventy-two aquatic plant quadrats dominated by one of three plant species (native Hydrilla verticillata, Myriophyllum spicatum and invasive C. caroliniana) were collected in East China. The field investigations showed that water turbidity and underwater photosynthetically active radiation (PAR) were the main factors affecting the relative coverage and abundance of the three submerged plants. 
　　Subsequently, a mesocosm experiment was conducted to explore the responses of the functional traits of the three species to different levels of underwater PAR. The results showed that the performance of C. caroliniana was superior to that of the two native species at low underwater PAR, indicating a better ability of this species to attenuate light. 
　　“If underwater darkening continues, submerged plants that are not suitable for or sufficiently tolerant of growth under these conditions may vanish, and plants that are suitable for these conditions, typically invasive plants, may prosper,” said Dr. HUANG. 
　　The results also indicate that if water bodies maintain low turbidity and a high underwater PAR after ecological restoration, the dominance of native aquatic plant vegetation will be achieved, thus constraining the growth and spread of invasive plants. 
　　“The ecological restoration of aquatic habitats that relies on the reconstruction of aquatic vegetation is a feasible strategy, but it must be based on habitat transformation. After the ecological restoration is completed, water bodies can maintain low turbidity and a high underwater PAR, and natural restoration of aquatic vegetation can be achieved,” said Dr. HUANG.
　　Cabomba caroliniana in its introduced natural habitats
　　Link: https://doi.org/10.1111/ddi.13678
　　(online on Jan. 31 2023)
　　Contact
　　TAN Lei 
　　Nanjing Institute of Geography and Limnology 
　　E-mail: ltan@niglas.ac.cn