China Helps Tanzania Improve Water Conservation Capacity in Great Lakes

  China on Wednesday started running a two-day training seminar aimed at assisting Tanzania to increase its capacity in water conservation and management in the country's Great Lakes. 
  The training seminar on Eco-environment and Water Security in Lake Basin System was jointly organized by the Nanjing Institute of Geography and Limnology (NIGLAS), the Sino-Africa Joint Research Center, and the Tanzania Fisheries Research Institute (TAFIRI). 
  Opening the seminar in Dar es Salaam, Riziki Shemdoe, permanent secretary of the Livestock and Fisheries, said Tanzania's Great Lakes of Tanganyika, Victoria, and Nyasa are important reservoirs of freshwater in the world, which require work together to protect them. 
  Shemdoe said the collaboration between the NIGLAS and the TAFIRI that has been in place for the last 15 years will not only benefit China and Tanzania but also have a meaningful impact on the global society of lake science.
  "Let me assure you that the entire management of the Ministry of Livestock and Fisheries supports you and your future ambitions. We will accord you all the necessary help to get this collaboration going as long as we can," he said. 
  Suo Peng, charge d'Affaires and minister counselor of the Chinese Embassy in Tanzania, said China and Tanzania have carried out several phases of cooperation research projects on water environment monitoring and resources protection of the Great Lakes region of East Africa since 2008. 
  Suo said the outcomes of the research have been recognized by local government and international organizations. 
   "I believe the efforts of NIGLAS experts will help Tanzania better protect its unique lake resources and stimulate its potential blue economy," said Suo. 
  The seminar focused on lake environment and ecology, water security and catchment management, and lake fishery and resources management. 
  The training seminar has brought together experts from Tanzania, Malawi, Zambia, Uganda, Burundi, Kenya, and the Democratic Republic of the Congo, countries that share the Great Lakes of Tanganyika, Victoria, and Nyasa.(Xinhua)
  The training seminar on Eco-environment and Water Security in Lake Basin System on April 12, 2023.(Photo by NIGLAS)

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Satellite Reveals Widespread Declines in Visual Wavelength of Color in China’s 2500 Lakes over the Past 40 Years

  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. 
  TAN Lei 
  Nanjing Institute of Geography and Limnology 
Conventional Aerobic Methanotrophs Have a Metabolic Versatility under Anoxia

  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: (online on Mar. 3 2023) 
  TAN Lei 
  Nanjing Institute of Geography and Limnology 
High Tolerance of the Invasive Submersed Plant Cabomba Caroliniana to Underwater Light Attenuation May Facilitate Its Invasiveness

  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
  (online on Jan. 31 2023)
  TAN Lei 
  Nanjing Institute of Geography and Limnology 

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Sediment organic matter properties facilitate understanding nitrogen transformation potentials in East African lakes

  East African lakes include the most productive and alkaline lake group in the world. Yet, they generally receive fewer nutrient inputs than the densely populated subtropical and temperate lakes in the northern hemisphere. In these lakes with insufficient supplies of inorganic nitrogen, the mineralization of benthic organic matter can play an important role in driving the nutrient cycle and nitrogen loss. Using a suite of stable 15N isotope dilution and tracer techniques, we examined five main processes of the sediment nitrogen cycle in 16 lakes and reservoirs of Tanzania and Kenya, East Africa: gross nitrogen mineralization, ammonium immobilization, dissimilatory nitrate reduction to ammonium (DNRA), and the dinitrogen (N2) production via denitrification and anaerobic ammonium oxidation (anammox). Gross nitrogen mineralization and ammonium immobilization showed the maximum values of 9.84 and 12.39 μmol N kg-1 h-1 , respectively. Potential DNRA rates ranged from 0.22 to 8.15 μmol N kg-1 h-1 and accounted for 10 %–74 % (average 25 %) of the total dissimilatory nitrate reduction. Potential nitrate reduction rates in most lakes were dominated by denitrification with a contribution of 26 %–85 % and a mean of 65 %. We further found that the sediment nitrogen transformations were driven mainly by benthic organic matter properties and water column phosphate concentrations, reflecting microbial metabolic responses to the changing carbon and nutrients availability. For instance, autochthonous production of protein-like organic matter attributed to active sediment nitrogen mineralization, DNRA, and denitrification. In contrast, the high degree of humification caused by the inputs of terrestrial humic-like substances slowed down the sediment nitrogen transformations. The contribution of DNRA to total dissimilatory nitrate reduction was significantly positively correlated to sediment C: N ratios. These results indicate that predictions of sediment N supply and loss in East African lakes can be improved by incorporating sediment organic matter properties.
  Xiaolong Yao, Zhonghua Zhao, Jianjun Wang, Qiqi Ding, Minglei Ren, Ismael Aaron Kimirei, Lu Zhang, Sediment organic matter properties facilitate understanding nitrogen transformation potentials in East African lakes, Science of The Total Environment, 841, 2022, 156607,
A comprehensive evaluation of organic micropollutants (OMPs) pollution and prioritization in equatorial lakes from mainland Tanzania, East Africa

  A lack of understanding the fate of highly toxic organic micropollutants (OMPs) in the equatorial lakes of Tanzania hinders public awareness for protecting these unique aquatic ecosystems, which are precious water resources and stunning wildlife habitats. To address this knowledge gap, the occurrence of 70 anthropogenically-sourced OMPs, including phthalates (PAEs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), was investigated in the water and sediment of 18 lakes in Tanzania. Similar residue concentrations were found in both compartments, showing higher pollution of PAEs ranging from 835.0 to 13,153.1 ng/L in water and 244.6–8691.8 ng/g dw in sediment, followed by PAHs, while OCPs and PCBs were comparatively lower. According to the multi-criteria scoring method for prioritization, the final OMP priority list for the lake environment in Tanzania comprised 25 chemicals, specifically 5 PAEs (DEHP, DIBP, DBP, DCHP and DMPP), 6 PCBs (PCB153, PCB105, PCB28, PCB156, PCB157 and PCB167), 6 PAHs (BaP, BaA, BbF, Pyr, DahA and InP) and 8 OCPs (cis-chlordane, trans-chlordane, p,p’-DDD, p,p’-DDE, p,p’-DDT, endrin, methoxychlor and heptachlor epoxide), suggesting the key substances for conventional monitoring and pollution control in these equatorial lakes, with an emphasis on PAEs, especially DEHP, due to the top priority and endocrine disruptor properties.
  Zhonghua Zhao, Xiaolong Yao, Qiqi Ding, Xionghu Gong, Jianjun Wang, Saadu Tahir, Ishmael Aaron Kimirei, Lu Zhang, A comprehensive evaluation of organic micropollutants (OMPs) pollution and prioritization in equatorial lakes from mainland Tanzania, East Africa, Water Research, Volume 217, 2022, 118400, ISSN 0043-1354,
Re-evaluation of Wetland Carbon Sink Mitigation

  A new review of coastal and inland wetland carbon sink services reveals current mitigation concepts for greenhouse gas emissions and measurements are not what they seem. Accumulation of buried organic carbon is not a measure of carbon sequestration; stable organic carbon inputs require subtraction and are undervalued; and carbon mitigation from wetland restoration is less than their preservation. 
  The study was published in the journal Wetlands as a flagship Mark Brison Review, from Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences (NIGLAS) in collaboration with Borneo Marine Research Institute (BMRI) Universiti Malaysia Sabah (UMS), and lead by the Institute for Marine and Antarctic Studies (IMAS) University of Tasmania (UTAS).  
  Associate Reseacher Dr John Barry Gallagher (IMAS) said that the sediment organic carbon accumulation down inland and coastal wetlands has always been regarded as a convenient means of measuring trends and average rates of sequestration over climatic scales. Wetlands, however, are open to organic inputs from catchments and adjacent water bodies. These can be labile and easily consumed or decomposed, and recalcitrant outside the carbon loop that is not consumed or decomposed. 
  Consequently, what is required from the sediment record is not the total organic burial, but the burial rate of what remains of the wetlands plant production from the amount of the labile organics inputs consumed, and the remains of those recalcitrants inputs, largely black or pyrogenic carbon. To estimate this we modified a general decomposition model to hindcast the original input rate and to project what remains for all organic sources after 100 years of burial. 
  For a mangrove and a seagrass ecosystem, we found that carbon accumulation was on average 33.5 and 7.2 times greater than their respective sequestration rates. We also noted that sequestration relative to its non-canopy replacement or alternative stable state is not included for voluntary or compliance carbon markets, instead, only the rate of loss and gain of organic stocks for wetlands likely be disturbed or restored. This limitation would otherwise undervalue the wetlands systems mitigation potential with one caveat: the rate of gain in sediment stocks for a restored system is similarly constrained as a mitigation service by consumption and decomposition of those external organic inputs. 
  Dr Gallagher says that the review is important from two standpoints. Firstly, natural carbon sequestration solutions require re-evaluation. This is required to avoid GHG emissions above their capacity or indeed reduce the ability to fulfil Nations’emission targets, as set by COP26. Secondly, the model provides a new Paleoecological tool. It has the potential to measure and predict how wetlands' ability to function as a carbon sink can change with both climate and catchment agricultural and industrial development from changes to government policy.
  Paper link: 
Estimating seasonal water budgets in global lakes by using multi-source remote sensing measurements

  The seasonal change in lake water storage (LWSsc) reflect periodic fluctuations of the basin-scale water balance. However, the role of LWSsc in regulating the water budget at the global scale has not yet been investigated based on straight-forward observations. Quantifying LWSsc is necessary, especially under the context of global change. Available in-situ measurements of lake water levels and volumes are still scarce. Therefore, the Global Surface Water datasets of Joint Research Centre and multi-source satellite altimetry datasets through mathematical statistics methods are used in this study to address this issue. We estimate the LWSsc of 463 lakes and reservoirs worldwide with areas greater than 10 km2, which represent nearly 64% of the total global lake area and 93% of the total lake volume capacity. Results show that the global seasonal water storage variation of these examined water bodies is 1390.91 ± 78.91 km3, comprising 869.44 ± 67.35 km3 from lakes and 521.46 ± 41.11 km3 from reservoirs. The relatively large estimates of LWSsc are concentrated in North American and African basins. Among the watersheds, the seasonal fluctuations of lakes in the North American Lawrence basin make up the most substantial magnitude of 10.76% of the global LWSsc. The latitudinal direction zonality of LWSsc is relatively significant. The LWSsc is concentrated between 30° N and 60° N in the northern hemisphere and between the equator and 30° S in the southern hemisphere. Considering the geographic similarity and climatological zonality, the global LWSsc estimates are also extrapolated to other lakes without direct satellite altimetry observations on the basis of the average rate of the examined lakes distributed in the same Koppen-Geiger Climate Classification zones. The LWSsc is calculated with a consequence of 488.23 ± 14.72 km3 for these extrapolated lakes, indicating an estimate of 1357.67 ± 68.94 km3 for the LWSsc of the global natural lakes (>10 km2). This initial estimation of LWSsc at a global scale will greatly help the improvement of our understanding of the seasonal behavior of lakes and reservoirs in regulating global and regional water cycles and the contribution of terrestrial water storage to sea level rise.
  CHEN Tan, SONG Chunqiao, KE Linghong et al. Journal of