Long-term (2003-2021) evolution trend of water quality in the Three Gorges Reservoir: An evaluation based on an enhanced water quality index.

The degradation of water quality induced by the construction of large-scale hydraulic projects is one of the primary public concerns; however, it is rarely addressed with long-term field observation data. Here, we reported the long-term (2003-2021) trends, seasonal patterns, and overall condition of water quality of the Three Gorges Reservoir (TGR) with an enhanced water quality index (WQI). Specifically, to emphasize the importance of the biological role in water quality assessment, chlorophyll-a (Chla) was incorporated into WQI, and then a novel workflow using machine learning approach based on Random Forest (RF) model was constructed to develop a minimal water quality index (WQImin). The enhanced WQI indicated an overall "good" water quality condition, exhibiting a gradually improving trend subsequent to the reservoir impoundment in 2003. Meanwhile, the assessment revealed that the water quality has discernible seasonal patterns, characterized by poorer conditions in the spring and summer seasons. Furthermore, the RF model identified Chla, dissolved oxygen (DO), ammonium nitrogen (NH4-N), water temperature (WT), pH, and total nitrogen (TN) as key parameters for the WQImin, with Chla emerging as the most important factor in determining WQImin in our study. Moreover, weighted WQImin models exhibited improved performance in estimating WQI. Our study emphasizes the importance of biological parameters in water quality assessment, and introduces a systematic workflow to facilitate the development of WQImin for accurate and cost-efficient water quality assessment. Furthermore, our study makes a substantial contribution to the advancement of knowledge regarding long-term trends and seasonal patterns in water quality of large reservoirs, which provides a foundational basis for guiding water quality management practices for reservoirs worldwide.

Effects of water impoundment and water-level manipulation on the bioaccumulation pattern, trophic transfer and health risk of heavy metals in the food web of Three Gorges Reservoir (China).

The Three Gorges Reservoir (TGR) of China, the largest hydropower project over the world, has attracted much attention to the water impoundment and water-level manipulation. In this study, we evaluated potential effects of water impoundment and seasonal water-level manipulation on the bioaccumulation, trophic transfer and health risk of HMs (Cu, Fe, Zn, Hg, Cd and Pb) in food web components (seston, aquatic invertebrate and fish) in TGR. Our results show that, after the impoundment for eight years (2003-2010), all of the six metal concentrations in aquatic biota fell within the criteria of safety quality guidelines. The concentrations of Cu, Fe, Zn and Hg in fish and aquatic invertebrates were higher than those before impoundment, whereas Cd and Pb were lower than those before impoundment. Nonetheless, Hg, Cd and Pb in aquatic consumers underwent an increasing trend during the entire impoundment, implying potential reservoir effect in the future. Only the concentrations of Hg, Cd and Pb in aquatic consumers exhibited a declining trend towards the dam, showing consistent with the background level at the three reaches. Seasonal variations in HM concentrations of fish and aquatic invertebrates were ascribed to the water-level manipulation associated with reservoir management. Our findings show that Hg or Cd biomagnified through aquatic food web during different hydrological periods, whereas Pb, Cu, Fe and Zn exhibited weak biomagnification power. Overall, Hg, Cd and Pb showed a higher risk than that of Cu, Fe and Zn.

Multiplex PCR Based Epidemiological Study for the Causes of Acute Diarrheal Disease in Adults Living in Jeju Island / 대한임상미생물학회지

BACKGROUND: We attempted to determine the characteristics of diarrheal pathogens according to species, seasonal variations, and patient age using multiplex PCR for the epidemiologic study of diarrheal disease in Jeju Island. METHODS: From March 2015 to Feb 2017, stool specimens were collected from 537 diarrheal patients older than 16 years. Multiplex PCR was used to identify pathogens and found Group A Rotavirus, enteric Adenovirus, Norovirus GI/GII, Astrovirus, Salmonella spp., Shigella spp., Vibrio spp., Campylobacter spp., Clostridium difficile toxin B (CDB), Clostridium perfringens, Yersinia enterocolitica, Aeromonas spp., Escherichia coli O157:H7, and verocytotoxin-producing E. coli (VTEC). RESULTS: Pathogens were isolated from 221 of 537 samples (41.2%); 9.3% were positive only for viral pathogens; 30.2%, only for bacterial pathogens; and 1.7%, for both viral and bacterial pathogens. Bacteria were more prevalent in spring, summer, and autumn, but viral pathogens were more prevalent in winter. Overall prevalence were Campylobacter spp. (26.7%), Clostridium perfringens (23.9%); Norovirus GII (11.4%), CDB (8.2%), Aeromonas spp. (6.3%), Group A Rotavirus (5.1%), Salmonella spp. (3.9%), Astrovirus (3.9%), Norovirus GI (3.1%), Vibrio spp (2.7%), enteric Adenovirus (1.6%), Shigella spp. (1.2%), VTEC (1.2%), and Yersinia enterocolitica (0.4%). Group A Rotavirus and Norovirus GII were more prevalent in winter and early spring. Campylobacter spp., CDB, and C. perfringens were detected frequently, without seasonal variation. CONCLUSION: Bacterial pathogens are more prevalent than viruses in acute diarrhea in adults living in Jeju Island, especially in spring, summer, and autumn. Viral pathogens are prevalent in winter. Campylobacter spp., CDB, and Clostridium perfringens are the major pathogens occurring without seasonal variations. These data will be helpful in identifying diarrheal pathogens and for treatments and prevention strategies.

Clinical Characteristics of Streptococcus agalactiae Bacteremia in Adults Living in Jeju Island / 대한임상미생물학회지

BACKGROUND: Streptococcus agalactiae (Group B streptococcus, GBS) is known to be the leading cause of neonatal sepsis and meningitis in the United States and Europe. In addition, GBS infection has been increasingly noted in adults, particularly in those with underlying diseases, such as diabetes mellitus, malignancy and liver disease. A few studies reported that resistances to antibiotics, such as erythromycin, clindamycin, tetracycline are increasing. We report clinical and microbiological characteristics of GBS bacteremic patients in Jeju Island. METHODS: We retrospectively analyzed medical records, such as age, sex, underlying disease, mortality, skin defects, laboratory results and antibiotic resistances of GBS in hospitalized adult patients who were diagnosed with GBS bacteremia from 2008 to 2013 in Jeju Island. RESULTS: Twenty two adult patients were diagnosed as GBS bacteremia from 2008 to 2013. The mean age of GBS bacteremic patients was 66.2 years old. Of 22 bacteremic patients, fifteen patients (68%) were older than 60. Twenty patients (91%) of bacteremic patients had underlying diseases such as diabetes mellitus, malignancy and liver disease. Ten (45%) patients had skin defects which were on the lower extremities and buttock, fifteen (68%) patients had fever at the time of admission, twenty one (95%) patients were admitted via the emergency department. Two (9%) patients died. The mean white blood cell (WBC) count, percentile of neutrophil count, and C-reactive protein (CRP) levels were 11,488/microL, 84.3 %, 13.5 mg/dL respectively. All GBS isolates from bacteremia showed sensitivities to penicillin, ampicillin, and vancomycin, and showed resistances to erythromycin (25%), clindamycin (30%), and tetracycline (55%). CONCLUSION: Bacteremia caused by GBS was prevalent in adult patients with underlying diseases. Most of the GBS bacteremic patients were emergency cases, with a high body temperature, WBC, CRP level, and neutrophil count. Half of them had skin defects, which are considered a source of GBS bacteremia.

Seroprevalences of Mycoplasma pneumoniae IgM Antibodies among Children Living in Jeju Island, Korea

BACKGROUND: Mycoplasma pneumoniae (MP) is a major cause of community-acquired pneumonia in children. The particle agglutination (PA) assay is a clinical test routinely used to detect MP infection and to determine total MP antibody titers. Using this assay, however, it is difficult to differentiate between IgM and IgG antibodies. The aim of this study was to investigate the seroprevalence of MP IgM antibodies in children living in Jeju Island. METHODS: We investigated the seroprevalence of mycoplasma IgM antibodies in 1,693 patients in the age of 0-10 yr who were ordered for mycoplasma IgM antibody testing in Cheju Halla Hospital between April 2011 and March 2013. Results were classified according to age, sex and the month and year during which the samples were obtained. RESULTS: The overall positive rate for mycoplasma IgM antibody was 24.7% and was higher in females than in males (P=0.012). The positive rate was lowest in infants under 6 months of age, and gradually rose with increasing age until the age of 4 yr. A major increase in positive rates was observed between January-April of 2012 and minor cyclical increases were also observed at 2-4 month intervals during the study period. CONCLUSIONS: The seroprevalence of mycoplasma IgM antibodies rises gradually with age until the age of 4 yr. A major peak in MP IgM antibody-positive cases was observed in early 2012, with minor cyclical increases at every 2-4 months. These results will be helpful in the interpretation and diagnosis of MP in children living in Jeju Island.

Frequency of Mycoplasma pneumoniae Antibodies in Children Living on Jeju Island / 대한임상미생물학회지

BACKGROUND: Mycoplasma pneumoniae (MP) is a major cause of community-acquired pneumonia in children. Currently, no study exists regarding the frequency of the mycoplasmal antibody on Jeju Island. The aim of the present study was to investigate the frequency of mycoplasmal antibody among children living on Jeju Island. METHODS: From March 2009 to February 2011, the frequency of mycoplasmal antibody among 1580 pediatric (1:40, 20.8% in an antibody titer >1:320, and 10.7% in an antibody titer >1:640. The positive rates of each antibody titer were lowest in children under the age of 6 months, and the positive rates increased gradually with age until 4 years, where the frequency showed a "plateau." There were minor cyclic increases of positive rate (>1:320, >1:640) every three months from August 2009 to June 2010, and there was a major increase of positive rate (>1:320, >1:640) from July 2010 to January 2011. However, there was no positive rate cyclic pattern of mycoplasmal antibody in the lower titer (>1:40) patients. CONCLUSION: The frequency of mycoplasmal antibody titer is lowest under the age of 6 months. The positive rates rise gradually with age until the age of 4 years. The present study showed minor peaks of mycoplasmal antibody titer every three months and a major peak of mycoplasmal antibody titer. The results can be helpful for the interpretation and diagnosis of MP among pediatric patients on Jeju Island.