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The best estimated average position of SN 1181 is given by a blue cross surrounded by a blue error circle of radius 5 degrees.

An explosive Cosmic Chinese Conundrum - a hot detective story from a very cold case: HKU astrophysicists solve a 900-year-old mystery giving an ancient Chinese guest star of AD 1181 a place to stay and rest

The Chinese have a long, ancient history of recording “guest stars” – suddenly bright stars that appear in the sky for a while but then dim and disappear. Today we know these are rare, incredibly energetic supernova explosions from either massive stars or special, interacting binary systems that seed the Galaxy with heavy elements like iron and leaving behind neutron stars, pulsars, black holes and a gaseous remnant like the Crab nebula.   Now, a 900-year-old mystery on the true origins of the Chinese guest star of AD 1181 has finally been solved by an international team of astronomers. The Laboratory for Space Research (LSR) and Department of Physics of The University of Hong Kong(HKU) joined hands with collaborators from the UK, Spain, Hungary and France, pursued an investigation to unravel this mystery via newly uncovered clues of their own discovery. Remarkably, the guest star of AD 1181, reported at the time to be as bright as the planet Saturn, was the only historical supernova(SN) of the last thousand years that has been without identification with a real object.   Published recently in the prestigious Astrophysical Journal letters, this team reports the identification of SN of AD 1181 with their previous co-discovery in 2017 of “Parker’s star”,  the hottest known Wolf-Rayet star (itself a truly unique object) with a temperature of more than 200,000 degrees Celsius. This star also has a surrounding nebula Pa30, discovered by their amateur colleague Dana PATCHICK in 2013.   Corresponding author Professor Quentin PARKER, also the Director of LSR said, “Our data showed the expanding gas cloud from this star has extreme velocities of around 1,100km/s from an explosion about 1,000 years ago.  This matches the AD 1181 event. Not only that but Pa30/Parker’s stars position in the sky fits the historical Chinese and Japanese reports on the guest star to within 3.5 degrees – well within the errors,” this after an association first made by co-author Professor Albert ZIJLSTRA, Professor in Astrophysics at The University of Manchester, also a key member of the LSR and a Hung Hing Ying Distinguished Visiting Professor in Science and Technology at HKU.   Pa30 and Parker's star have previously been proposed as the result of a merger of two White Dwarfs – dense dead stars, leading to a rare Type Iax supernova. The reported historical brightness and modern distance determined for their system suggests the event was dimmer than typical supernovae. This also agrees with the rare Type Iax designation, only the second of its kind known in the entire Galaxy.   Dr Andreas RITTER, the paper’s first author and HKU Postdoctoral Fellow within the LSR said, “Taken together, the age, location, reported “Guest star” brightness and recorded visibility for 6 months, shows that Parker’s star and its surrounding gas shroud Pa30 are indeed the counterparts of supernova SN of AD 1181.” The SN of AD 1181 event is also the only Type Iax supernova where detailed studies of the remnant star and surrounding nebula are possible. Combined with the extreme and remarkable nature of Parker's star itself and their linking of it to the AD 1181 supernova, this source becomes of considerable scientific and historical interest.  Finally, Parker's star is the only Wolf Rayet star known that is neither from a massive progenitor star nor the central star of a planetary nebula. Instead, it is the result of two white dwarf stars merging together and accompanied by a Type Iax supernova explosion that now has a firm historical basis. The Journal paper can be access from here.  The region of SN 1181 with the Chinese asterisms indicated by red lines. The position of Pa30 is shown by a black cross. The green line indicates the modern constellation Cassiopeia. The supernova was stated to lie in the Chinese “lunar lodge” Kui (between the two purple dotted lines) between Huagai and Chuanshe, near Wangliang. The best estimated average position of SN 1181 is given by a blue cross surrounded by a blue error circle of radius 5 degrees.  False colour images of “Parker’s star” and its surrounding nebula Pa30 that make-up the remnants from the SN 1181 AD event. The colours represent the infrared, optical, and UV light. The contours in the central image show X-ray emission. At the distance of 7,500 light years, 45 arc seconds on the sky translate to 100,000 astronomical units. One astronomical unit is the average distance between Earth and the Sun, which is about 93 million miles or 150 million kilometers.      

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HKU Physicist Professor YAO Wang being awarded of the 2021 Xplorer Prize

Congratulations to Professor YAO Wang, Chair Professor in Department of Physics, for his being awarded of the 2021 Xplorer Prize. Supported by Tencent, Xplorer Prize is presented to young scientists under the age of 45 who demonstrate exceptional quality and innovation in their field of research. Professor Yao is highly acclaimed scholars with international recognition, and ranked by Clarivate Analytics in the top 1% worldwide.   As a global research leader on condensed matter physics, quantum physics and optics, Professor Yao is currently focusing on two-dimensional materials and their heterostructures. He has played a decisive role in creating an important new research direction – valley optoelectronics in 2D materials, which aims to exploit valley, a quantum degree of freedom of electron, in future optoelectronic devices.   HKU is on the frontlines of ground-breaking research across academic disciplines – and the academic excellence our faculties exert great impacts in the research community. We hope Professor Yao can continue to pioneer in quantum physics of atomically thin semiconductors.   For details of the award, please visit: https://bit.ly/3nAkNNc

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The novel chemical synthetic carbohydrate conjugate vaccine successfully defeats the infection of drug resistant Acinetobacter baumannii.

HKU and CityU made a breakthrough in vaccination development against lethal bacteria, providing new opportunity for treating resistant A. baumannii infection

Recently, the teams led by Professor Xuechen LI from Department of Chemistry, Faculty of Science, The University of Hong Kong (HKU) and Professor Sheng CHEN from the Department of Infectious Diseases and Public Health of City University of Hong Kong (CityU), joined hands and made a breakthrough in vaccination development against lethal bacteria Acinetobacter baumannii. Their studies have been published in ACS Central Science. Acinetobacter baumannii (A. baumannii) is a Gram-negative pathogenic bacterium and it causes a wide range of serious infections such as bacteremia, pneumonia, meningitis, urinary tract infections, skin and soft tissue infections. Furthermore, A. baumannii tends to acquire resistance to numerous classes of antibiotics via multiple resistance mechanisms and has been identified as an ESKAPE pathogen, a group of pathogens with a high rate of antibiotic resistance. Because of the multi-drug resistant and severe threat to public health, A. baumannii is on the top of the list as the top priority for immediate attentions among the 12 “priority pathogens” requiring urgent antibacterial research and development (R&D) published by the World Health Organization (WHO) in 2017. Researchers worldwide are actively pursuing the development of new antibacterial drugs against multi-drug resistant A.baumannii. Apart from a search for novel antibiotics, vaccination or immunotherapy provides an alternative treatment to protect people from bacterial infections and combat multidrug resistance. Take Glycoconjugate vaccines as an example, it consists of bacteria surface glycans linking to a carrier protein of immunogenicity, have been successfully developed and clinically applied in treatment against bacteria, such as Prevnar 13® as the Pneumococcal vaccine. When people were invaded by the bacteria after vaccination, immune system will recognise the surface glycan and trigger immune response to kill it. Considering the structural variety and complexity of bacteria surface glycan, difficulty in culturing pathogenic bacteria and possibility of contamination in isolation process, chemical synthesis could be an alternative in obtaining bacteria surface glycan compared with isolation from bacteria. For the past seven years Professor Li’s lab was focusing on the chemical synthesis of pseudaminic acid, a nine-carbon monosaccharide unique to bacteria and commonly present in Gram-negative pathogen surfaces including A. baumannii. His team has developed the highly efficient and stereoselective methods to construct pseudaminic acid-containing glycans. In the current study, Li and Chen’s group chemically synthesized pseudaminic acid-carrier protein conjugate and tested its potential as the anti-bacterial vaccine. They found that anti-pseudaminic acid antibody from vaccinated mice sera reached a high level after vaccination and the vaccinated mice were completely protected from infection of A. baumannii , whereas all control mice received negative control died within 36 hours. Professor Li and Professor Chen believe that this exciting finding will provide new opportunity for treating resistant A. baumannii infection. They have applied the patent and will further evaluate its potential in preclinical studies. The journal paper can be accessed from here.    From the left: Ms Xuemei YANG (CityU), Professor Sheng CHEN (CityU), Professor Xuechen LI (HKU), Dr  Han Liu (HKU) and Mr Tongyao WEI(HKU). From the left: Professor Sheng CHEN(City U), Ms Xuemei YANG(CityU), Dr. Han LIU(HKU) and Professor Xuechen LI(HKU).  

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The best estimated average position of SN 1181 is given by a blue cross surrounded by a blue error circle of radius 5 degrees.

An explosive Cosmic Chinese Conundrum - a hot detective story from a very cold case: HKU astrophysicists solve a 900-year-old mystery giving an ancient Chinese guest star of AD 1181 a place to stay and rest

The Chinese have a long, ancient history of recording “guest stars” – suddenly bright stars that appear in the sky for a while but then dim and disappear. Today we know these are rare, incredibly energetic supernova explosions from either massive stars or special, interacting binary systems that seed the Galaxy with heavy elements like iron and leaving behind neutron stars, pulsars, black holes and a gaseous remnant like the Crab nebula.   Now, a 900-year-old mystery on the true origins of the Chinese guest star of AD 1181 has finally been solved by an international team of astronomers. The Laboratory for Space Research (LSR) and Department of Physics of The University of Hong Kong(HKU) joined hands with collaborators from the UK, Spain, Hungary and France, pursued an investigation to unravel this mystery via newly uncovered clues of their own discovery. Remarkably, the guest star of AD 1181, reported at the time to be as bright as the planet Saturn, was the only historical supernova(SN) of the last thousand years that has been without identification with a real object.   Published recently in the prestigious Astrophysical Journal letters, this team reports the identification of SN of AD 1181 with their previous co-discovery in 2017 of “Parker’s star”,  the hottest known Wolf-Rayet star (itself a truly unique object) with a temperature of more than 200,000 degrees Celsius. This star also has a surrounding nebula Pa30, discovered by their amateur colleague Dana PATCHICK in 2013.   Corresponding author Professor Quentin PARKER, also the Director of LSR said, “Our data showed the expanding gas cloud from this star has extreme velocities of around 1,100km/s from an explosion about 1,000 years ago.  This matches the AD 1181 event. Not only that but Pa30/Parker’s stars position in the sky fits the historical Chinese and Japanese reports on the guest star to within 3.5 degrees – well within the errors,” this after an association first made by co-author Professor Albert ZIJLSTRA, Professor in Astrophysics at The University of Manchester, also a key member of the LSR and a Hung Hing Ying Distinguished Visiting Professor in Science and Technology at HKU.   Pa30 and Parker's star have previously been proposed as the result of a merger of two White Dwarfs – dense dead stars, leading to a rare Type Iax supernova. The reported historical brightness and modern distance determined for their system suggests the event was dimmer than typical supernovae. This also agrees with the rare Type Iax designation, only the second of its kind known in the entire Galaxy.   Dr Andreas RITTER, the paper’s first author and HKU Postdoctoral Fellow within the LSR said, “Taken together, the age, location, reported “Guest star” brightness and recorded visibility for 6 months, shows that Parker’s star and its surrounding gas shroud Pa30 are indeed the counterparts of supernova SN of AD 1181.” The SN of AD 1181 event is also the only Type Iax supernova where detailed studies of the remnant star and surrounding nebula are possible. Combined with the extreme and remarkable nature of Parker's star itself and their linking of it to the AD 1181 supernova, this source becomes of considerable scientific and historical interest.  Finally, Parker's star is the only Wolf Rayet star known that is neither from a massive progenitor star nor the central star of a planetary nebula. Instead, it is the result of two white dwarf stars merging together and accompanied by a Type Iax supernova explosion that now has a firm historical basis. The Journal paper can be access from here.  The region of SN 1181 with the Chinese asterisms indicated by red lines. The position of Pa30 is shown by a black cross. The green line indicates the modern constellation Cassiopeia. The supernova was stated to lie in the Chinese “lunar lodge” Kui (between the two purple dotted lines) between Huagai and Chuanshe, near Wangliang. The best estimated average position of SN 1181 is given by a blue cross surrounded by a blue error circle of radius 5 degrees.  False colour images of “Parker’s star” and its surrounding nebula Pa30 that make-up the remnants from the SN 1181 AD event. The colours represent the infrared, optical, and UV light. The contours in the central image show X-ray emission. At the distance of 7,500 light years, 45 arc seconds on the sky translate to 100,000 astronomical units. One astronomical unit is the average distance between Earth and the Sun, which is about 93 million miles or 150 million kilometers.      

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HKU Physicist Professor YAO Wang being awarded of the 2021 Xplorer Prize

Congratulations to Professor YAO Wang, Chair Professor in Department of Physics, for his being awarded of the 2021 Xplorer Prize. Supported by Tencent, Xplorer Prize is presented to young scientists under the age of 45 who demonstrate exceptional quality and innovation in their field of research. Professor Yao is highly acclaimed scholars with international recognition, and ranked by Clarivate Analytics in the top 1% worldwide.   As a global research leader on condensed matter physics, quantum physics and optics, Professor Yao is currently focusing on two-dimensional materials and their heterostructures. He has played a decisive role in creating an important new research direction – valley optoelectronics in 2D materials, which aims to exploit valley, a quantum degree of freedom of electron, in future optoelectronic devices.   HKU is on the frontlines of ground-breaking research across academic disciplines – and the academic excellence our faculties exert great impacts in the research community. We hope Professor Yao can continue to pioneer in quantum physics of atomically thin semiconductors.   For details of the award, please visit: https://bit.ly/3nAkNNc

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The novel chemical synthetic carbohydrate conjugate vaccine successfully defeats the infection of drug resistant Acinetobacter baumannii.

HKU and CityU made a breakthrough in vaccination development against lethal bacteria, providing new opportunity for treating resistant A. baumannii infection

Recently, the teams led by Professor Xuechen LI from Department of Chemistry, Faculty of Science, The University of Hong Kong (HKU) and Professor Sheng CHEN from the Department of Infectious Diseases and Public Health of City University of Hong Kong (CityU), joined hands and made a breakthrough in vaccination development against lethal bacteria Acinetobacter baumannii. Their studies have been published in ACS Central Science. Acinetobacter baumannii (A. baumannii) is a Gram-negative pathogenic bacterium and it causes a wide range of serious infections such as bacteremia, pneumonia, meningitis, urinary tract infections, skin and soft tissue infections. Furthermore, A. baumannii tends to acquire resistance to numerous classes of antibiotics via multiple resistance mechanisms and has been identified as an ESKAPE pathogen, a group of pathogens with a high rate of antibiotic resistance. Because of the multi-drug resistant and severe threat to public health, A. baumannii is on the top of the list as the top priority for immediate attentions among the 12 “priority pathogens” requiring urgent antibacterial research and development (R&D) published by the World Health Organization (WHO) in 2017. Researchers worldwide are actively pursuing the development of new antibacterial drugs against multi-drug resistant A.baumannii. Apart from a search for novel antibiotics, vaccination or immunotherapy provides an alternative treatment to protect people from bacterial infections and combat multidrug resistance. Take Glycoconjugate vaccines as an example, it consists of bacteria surface glycans linking to a carrier protein of immunogenicity, have been successfully developed and clinically applied in treatment against bacteria, such as Prevnar 13® as the Pneumococcal vaccine. When people were invaded by the bacteria after vaccination, immune system will recognise the surface glycan and trigger immune response to kill it. Considering the structural variety and complexity of bacteria surface glycan, difficulty in culturing pathogenic bacteria and possibility of contamination in isolation process, chemical synthesis could be an alternative in obtaining bacteria surface glycan compared with isolation from bacteria. For the past seven years Professor Li’s lab was focusing on the chemical synthesis of pseudaminic acid, a nine-carbon monosaccharide unique to bacteria and commonly present in Gram-negative pathogen surfaces including A. baumannii. His team has developed the highly efficient and stereoselective methods to construct pseudaminic acid-containing glycans. In the current study, Li and Chen’s group chemically synthesized pseudaminic acid-carrier protein conjugate and tested its potential as the anti-bacterial vaccine. They found that anti-pseudaminic acid antibody from vaccinated mice sera reached a high level after vaccination and the vaccinated mice were completely protected from infection of A. baumannii , whereas all control mice received negative control died within 36 hours. Professor Li and Professor Chen believe that this exciting finding will provide new opportunity for treating resistant A. baumannii infection. They have applied the patent and will further evaluate its potential in preclinical studies. The journal paper can be accessed from here.    From the left: Ms Xuemei YANG (CityU), Professor Sheng CHEN (CityU), Professor Xuechen LI (HKU), Dr  Han Liu (HKU) and Mr Tongyao WEI(HKU). From the left: Professor Sheng CHEN(City U), Ms Xuemei YANG(CityU), Dr. Han LIU(HKU) and Professor Xuechen LI(HKU).  

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Bacterial curli promotes the aggregation of α-synuclein through cross-seeding, which leads to mitochondrial stress and neurodegeneration.

HKU biologists identified bacterial proteins that promote neurodegeneration, shedding light on new ways to prevent or slow down neurodegenerative diseases

Growing evidence indicates that gut microbiota plays a critical role in regulating the progression of neurodegenerative diseases such as Parkinson’s disease (PD) and Alzheimer’s disease (AD), but the molecular mechanism underlying such microbe-host interaction is still unclear. A research team led by Dr Chaogu ZHENG from the School of Biological Sciences at The University of Hong Kong (HKU) recently discovered that bacteria-derived curli amyloid fibril promotes neurodegeneration in the host. This new study provides direct evidence to suggest that bacteria can secrete proteins that form an amyloid fibril, which enters the host neurons and promotes protein aggregation and neurodegeneration. Inhibiting the ability of the bacteria to secrete such proteins may be a preventative treatment for neurodegenerative diseases. These research findings were recently published in a leading multidisciplinary journal -  Proceedings of the National Academy of Sciences of the United States of America (PNAS). The secret weapon of gut microbiota Neurodegenerative diseases are caused by protein aggregation in the neurons. Studies in the last few years have suggested that gut bacteria may play an important role in the pathogenesis of neurodegenerative diseases. For example, antibiotic treatment that kill most of the bacteria in the gut can help ameliorate the pathophysiology of PD in mice. Despite the emerging idea of “microbiota-gut-brain” link, little is known about the bacterial molecules that modulate the progression of neurodegeneration. To address this problem, the research team screened for bacterial E. coli genes whose deletion alleviates the PD symptoms in an animal model of PD. This animal is a microscopic nematode (worm) called Caenorhabditis elegans, used by scientists across the world as an important model organism for biological research. Because this animal fed on bacteria, the research team developed it into a powerful tool to analyse bacteria-host interaction. From a genome-wide screen, Dr Zheng’s team identified 38 bacterial genes that can promote neurodegeneration in the animal host. Two of these genes code for proteins that form curli, one type of bacterial amyloid fibers. The researchers then showed that bacterial curli enters the neurons to cross-seed the human amyloid α-synuclein and promote its aggregation, which leads to proteotoxicity, mitochondrial dysfunction, and neuronal death. Genetically deleting curli genes or pharmacologically inhibiting curli formation significantly suppressed the PD symptoms and improved neuronal functions. A potential therapeutic approach Furthermore, the research team found that curli also promoted neurodegeneration in animal models of Alzheimer’s disease, Amyotrophic lateral sclerosis, and Huntington’s disease, suggesting that the bacteria-secreted curli may have detrimental effects in a range of neurodegenerative disorders. Targeting curli production in the gut may represent a general therapeutic approach to prevent or slow down the progression of protein aggregation diseases. “One of the interesting findings in this study is that a polyphenol called EGCG from green tea extracts can almost completely inhibit curli secretion in bacteria and has amazing effects in suppressing neurodegeneration. This is consistent with the observation that drinking green tea has beneficial effects in preventing neurodegenerative diseases,” said Dr Chenyin WANG, the first author of the paper. This research opens a new direction to develop preventative measures for neurodegenerative diseases by targeting bacterial curli production in the human gut. Importantly, Dr Zheng, the supervisor of the research project, pointed out that, “this study established a new paradigm for understanding how bacterial components from the gut microbiome can influence neuronal health in animals.” In the future, Dr Zheng wants to move on to study other bacterial molecules identified from the screen and investigate how they affect host neurodegeneration. Dr Zheng envisions that a complete understanding of the bacteria-host interaction in the context of neurodegeneration can help identify novel therapeutic targets for neurodegenerative disorders. (From the left) Dr Chaogu Zheng is the supervisor of the research project, while Postdoctoral fellow Dr Chenyin Wang is the first author. About the research paper “Wang, C., Lau, C.Y., Ma, F., and Zheng, C. Genome-wide screen identifies curli amyloid fibril as a bacterial component promoting host neurodegeneration. Proc Natl Acad Sci USA. 2021 Aug 24;118(34):e2106504118.” The journal paper can be accessed from here . This work is supported by funding from the Food and Health Bureau of Hong Kong, the Research Grant Council of Hong Kong, and The University of Hong Kong.    

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CubeSats serve as a bridge between proximate remote sensing measurements of phenocam and drone surveys, and MODIS satellite measurements. Figure credit: Dr Shengbiao WU and Miss Yingyi ZHAO

HKU environmental scientists solve key observational issues in new generation of satellites, transforming the way to track fine-scale changes of our planet from space

Our Earth has experienced rapid environmental changes tightly tied to anthropogenic activities. Satellite remote sensing offers a quantitative means to monitoring such changes but is often limited to coarse spatial or temporal resolutions. Only very recently, the arrival of Planet’s Dove satellites, a constellation of CubeSats that are made of 190+ satellite sensors to produce daily and global coverage at a 3-meter resolution, offers an unprecedented opportunity for fine-scale Earth’s surface monitoring. However, several issues remain with CubeSat observations that further hinder its broader applications: 1) Frequent clouds and cloud shadows often contaminate the satellite signal, 2) CubeSat observations source from 190+ satellite sensors with varying sun angles, causing the data inconsistency issue across different sensors, and 3) accurate biophysical interpretation of satellite signal remains lacking. Dr Jin WU and Dr Jing WANG from Global Ecology and Remote Sensing (GEARS) Lab at the School of Biological Sciences, The University of Hong Kong (HKU), conducted a few research address to the above issues by developing novel observational methods that provide better accuracy on tracking fine-scale changes from space. For example, the team has recently developed an automatic cloud and cloud shadow screening method for CubeSats, which leverages the spatial and temporal information of satellite reflectance bands, and has been demonstrated to enable cloud and shadow screening with the highest accuracy and least sensitivity to land cover type. The research outcome thus advances the monitoring of atmospheric cloud covers, while improving the data quality assessments for land-surface monitoring and biophysical extraction; the research has recently been published in scientific journal Remote Sensing of Environment (RSE). Besides, the team has put much effort in recent years into improving the processing and interpretation of CubeSats. For example, to improve its data consistency over space and time, the team developed a rigorous method to cross-calibrate CubeSats to the same level as a more stable single-sensor satellite - Moderate Resolution Imaging Spectroradiometer (MODIS), that has been rigorously calibrated with sun-sensor geometry issues and demonstrated with consistently high data quality. In order to perform a direct and accurate biophysical interpretation from space, the team proposed a spectral unmixing approach that effectively classified the forest canopy into leafy vs leafless phenophases, from which it would enable fine-scale accurate phenology monitoring of tropical forests. Similarly, by integrating proximate drone surveys with CubeSats, the team demonstrated the feasibility to monitor plant phenology at the tree-crown scale. “Our research has made significant observational advances to make full use of these new-generation satellite data, and ultimately facilitate the monitoring of Earth’s environmental changes, especially for those rapid and fine-scale changes,” said Dr Jing Wang, the leading author of the two journal papers published in RSE. “There have been a series of papers in RSE on similar topics. Our work is not another one, but a new attempt to explore the possibility to enable satellite techniques for crown-scale phenology monitoring, which thus represents the cutting-edge research frontier and also opens a world of possibilities for individual-based ecology studies using satellite techniques,” added Dr Jin Wu, Principal Investigator of Global Ecology and Remote Sensing (GEARS) Lab at HKU. With these advances, in the next step, the GEARS lab is aiming to leverage CubeSats and other geospatial technologies to facilitate the relevant research fields, which include but are not limited to ecological scaling principles, biodiversity research, forest growth, health, and management practices, climate change impact assessments and mitigation strategies, and ultimately the nature-based solutions to reaching carbon neutral goals.   The latest findings can be accessed from the following links: Automatic cloud and cloud shadow detection in tropical areas for PlanetScope satellite images Other related journal papers can be accessed from the following links: Multi-scale integration of satellite remote sensing improves characterization of dry-season green-up in an Amazon tropical evergreen forest Monitoring tree-crown scale autumn leaf phenology in a temperate forest with an integration of PlanetScope and drone remote sensing observations    

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Small fossil shells preserved in sediment on the seafloor can reconstruct the history of marine ecosystem.  Photo credits: Dr Yuanyuan Hong.

Has Hong Kong lost its luster? HKU Ecologists reconstructed Hong Kong's marine ecosystem over the last 100 years Worried that climate and metal pollution may have a negative impact on the biodiversity

Dr Hong and her team used tens of thousands of small fossil shells preserved in sediment on the seafloor to reconstruct Hong Kong's marine ecosystem over the last ~50 - 100 years. Has Hong Kong, the Pearl of the Orient, lost its luster? The answer may be different on land versus in the sea. The skyscrapers and urban development that have made Hong Kong the "Pearl" have also generated pollutants that affect the marine species that live in Hong Kong's coastal waters. On-going climate change and dams along the Pearl River have also altered these coastal ecosystems. However, it is largely unknown in what ways they are altered, because we lack information about baseline conditions back then. "What were marine environments and organisms like in Hong Kong, say, 50 - 100 years ago, when human activity was much more limited? How were they different from what we see today?" Dr Yuanyuan HONG, a postdoctoral fellow from the School of Biological Sciences, the Research Division for Ecology & Biodiversity, and The Swire Institute of Marine Science at The University of Hong Kong (HKU) raised the question.    Fortunately, young fossils can help to provide the answers. Dr Hong and her team used tens of thousands of small fossil shells preserved in sediment on the seafloor to reconstruct Hong Kong's marine ecosystem over the last ~50 - 100 years. Using sophisticated biodiversity measures recently developed by co-lead author Professor Anne CHAO from National Tsing Hua University, Taiwan, Dr Hong discovered that climate and metal pollution have played major roles in shaping present-day marine communities in Hong Kong. The finding has recently been published in Anthropocene. "Climate change, specifically weakening of the East Asian Summer Monsoon, has resulted in less rain and less discharge of freshwater from the Pearl River, and this has substantially impacted marine life in Hong Kong's eastern waters, such as in Mirs Bay and Sai Kung. In addition, metal pollution from wastewater and the antifouling paints used on ships have greatly altered marine communities in the central part of Hong Kong, such as Victoria Harbour," said the lead author Dr Hong. Significant impact on rare species "Hong Kong's eastern waters are much less polluted than the central and western waters. However, these ecosystems are also much more sensitive to climate change. Future anthropogenic warming may reduce global ocean circulation and this may enhance the East Asian Summer Monsoon. So, organisms in Hong Kong's eastern waters may be confronted by enhanced discharge from the Pearl River and resulting lower salinity, higher turbidity, and muddier environments in the near future. Our research indicates that these environmental changes will especially affect rare species. Most species in tropical and subtropical places like Hong Kong are rare, so the anticipated changes may have a profound impact," co-lead author Dr Moriaki YASUHARA from the School of Biological Sciences, the Research Division for Ecology & Biodiversity, and The Swire Institute of Marine Science at HKU explained. Hong Kong is one of the largest coastal cities in the world and has one of the world's busiest ports. Metal pollution, most likely generated from wastewater and the antifouling paints used on ships, has affected marine life in Victoria Harbour, which is surrounded by Tsim Sha Tsui and Causeway Bay (two of the biggest downtowns) . "Hong Kong's western waters of the Pearl River estuary is resistant and resilient from climatic and anthropogenic changes rather surprisingly. It is also surprising that eutrophication and deoxygenation did not show any substantial effect on Hong Kong's marine ecosystem in our study. This may be because the Pearl River estuary and South China Sea in general are naturally rich in organic matter and nutrients from mega rivers and high precipitation, and also deoxygenation in Hong Kong is not too serious compared to other urbanised sea areas such as Chesapeake bay next to Washington DC, Tokyo Bay next to Tokyo, and Baltic Sea surrounded by many European cities." Dr Hong further elaborated. "Hong Kong remains 'The Pearl' even in the sea, as these regions continue to harbour tremendously diverse marine life, but our research has shown that climate and human activities have changed our local marine ecosystem substantially in just 50 -100 years. Underwater change is more difficult to see, compared with deforestation or other modifications of the land," Dr Hong concluded. Yet, small fossils can reveal the history of underwater change over past decades, centuries, or longer. "Empty shells on the seafloor allow us to 'time travel' to past marine ecosystems and determine the ways in which natural and anthropogenic environmental change have shaped marine communities." co-lead author Dr Paul HARNIK from Colgate University pointed out.   One of the small shells: Ostracod, Neocytheretta faceta. Photo credit: Dr Yuanyuan Hong About the journal paper Citation: Yuanyuan Hong, Moriaki Yasuhara, Hokuto Iwatani, Anne Chao, Paul G. Harnik, and Chih-Lin Wei (2021) Ecosystem turnover in an urbanized subtropical seascape driven by climate and pollution. Anthropocene. Journal paper can be accessed from here.  For more information about HKU paleoecological research, please visit here.   

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