Papel de la bahía de Jiaozhou como una fuente/depósito de CO2 durante un ciclo estacional

The seasonal evolution of dissolved inorganic carbon (DIC) and CO2 air-sea fluxes in the Jiaozhou Bay was investigated by means of a data set from four cruises covering a seasonal cycle during 2003 and 2004. The results revealed that DIC had no obvious seasonal variation, with an average concentration of 2035 µmol kg-1 C in surface water. However, the sea surface partial pressure of CO2 changed with the season. pCO2 was 695 µatm in July and 317 µatm in February. Using the gas exchange coefficient calculated with Wanninkhof’s model, it was concluded that the Jiaozhou Bay was a source of atmospheric CO2 in spring, summer, and autumn, whereas it was a sink in winter. The Jiaozhou Bay released 2.60 x 1011 mmol C to the atmosphere in spring, 6.18 x 1011 mmol C in summer, and 3.01 x 1011 mmol C in autumn, whereas it absorbed 5.32 x 1010 mmol C from the atmosphere in winter. A total of 1.13 x 1012 mmol C was released to the atmosphere over one year. The behaviour as a carbon source/sink obviously varied in the different regions of the Jiaozhou Bay. In February, the inner bay was a carbon sink, while the bay mouth and the outer bay were carbon sources. In June and July, the inner and outer bay were carbon sources, but the strength was different, increasing from the inner to the outer bay. In November, the inner bay was a carbon source, but the bay mouth was a carbon sink. The outer bay was a weaker CO2 source. These changes are controlled by many factors, the most important being temperature and phytoplankton. Water temperature in particular was the main factor controlling the carbon dioxide system and the behaviour of the Jiaozhou Bay as a carbon source/sink. The Jiaozhou Bay is a carbon dioxide source when the water temperature is higher than 6.6°C. Otherwise, it is a carbon sink. Phytoplankton is another controlling factor that may play an important role in behaviour as a carbon source or sink in regions where the source or sink nature is weaker.La evolución estacional del carbono inorgánico disuelto (DIC) y el intercambio de flujos de CO2 aire-mar en la bahía de Jiaozhou han sido investigados a partir de datos obtenidos en 4 campañas oceanográficas que cubren un ciclo estacional entre 2003 y 2004. Los resultados muestran que el DIC no presenta una clara variación estacional con una concentración promedio de 2035 μmol kg-1 C en el agua de superficie. No obstante la presión parcial de CO2 en el agua superficial cambiaba con la estación. La PCO2 era de 695 μatm en Julio y 317 μatm en febrero. Utilizando el coeficiente de intercambio de gases calculado con el modelo de Wanninkhof concluíamos que la bahía de Jiaozhou era una fuente de CO2 a la atmósfera en primavera, verano y otoño, mientras que era un depósito de CO2 en invierno. La bahía proporcionaba 2.60 × 1011 mmol C a la atmósfera en primavera, 6.18 × 1011 mmol C en verano, y 3.01 × 1011 mmol C in otoño, mientras absorbia 5.32 × 1010 mmol C desde la atmósfera en invierno. Un total de 1.13 × 1012 mmol C eran liberados a la atmósfera durante un año. El comportamiento como fuente/depósito de carbono, obviamente era diferente en las distintas regiones de la bahía de Jiaozhou. En Febrero, la parte interior de la bahía era un depósito para el carbono, mientras que la desembocadura y la parte exterior actuaba como fuente de carbono. En Junio y Julio, las partes interna y externa de la bahía eran fuentes de carbono, pero la intensidad era diferente, incrementando desde la parte interior a la exterior de la bahía. En Noviembre, la parte interior de la bahía era fuente de carbono, pero la desembocadura de la bahía se comportaba como depósito de carbono. El exterior de la bahía era una fuente poco importante de CO2. Estos cambios están controlados por muchos factores, siendo los mas importantes la temperatura y el fitoplancton. Especialmente, la temperatura del agua era el factor principal en el control del dióxido de carbono en el sistema y del comportamiento de la bahía de Jiaozhou como fuente/depósito de carbono. La bahía de Jiaozhou es una fuente de dióxido de carbono cuando la temperatura del agua es mas alta que 6.6ºC. Si no es así es un depósito de carbono. El fitoplancton es el otro factor de control que puede jugar un papel importante en el comportamiento como fuente o depósito de carbono en regiones donde el carácter de fuente o depósito es debil.

Nonconservative behavior of dissolved molybdenum and its potential role in nitrogen cycling in the Bohai and Yellow Seas

Molybdenum plays an important role in marine biological activity, especially in nitrogen cycling as a cofactor for N2 fixation and nitrate reductase. However, the dissolved Mo (dMo) behavior and its interaction with N cycling in the coastal waters is still unclear. In this study, the dMo concentrations and parameters related to Mo distribution and N cycling in surface and bottom seawaters of the Bohai (BS) and Yellow Seas (YS) were examined. The results showed that dMo concentrations ranged from 36.4 nmol L-1 to 125.0 nmol L-1, most of which deviated significantly from the conservative line, indicating nonconservative behavior of Mo relative to salinity. The highest dMo concentrations occurring in 36°N section of north of the South YS (SYS), were close to conservative value (105 nmol L-1). Significant depletion up to 40-50 nmol L-1 of dMo mainly appeared in the BS, NYS and south of the SYS, suggesting the possible removal of dMo by biological utilization and particle adsorption. Particularly, the increasing dMo concentrations away the Yellow River estuary indicated that freshwater dilution was one of reasons for dMo distributions in the BS. The similar spatial distribution of dMo and dissolved Mn concentrations suggested the possible scavenging by MnOx phases for Mo removal. The negative correlation between dMo and chlorophyll-a (Chl-a) concentrations in surface seawaters suggested that biological uptake was involved in dMo removal. The depleted dMo in most of sites corresponded with the higher nitrite concentrations, implying the possible involvement of nitrate reduction process. Although the highest N2 fixation rates and relative abundances of cyanobacteria appeared in 36°N section, corresponding with the conservative dMo, suggesting that Mo may play a minor role in N2 fixation process there. The ten-folds of relative abundance of bacteria with nitrate reduction function than that with N2 fixation function suggested that dMo seems to play more important role in nitration reduction than nitrogen fixation in the BS and YS

Geochemistry of Middle Holocene sediments from south Yellow Sea: Implications to provenance and climate change

From a large number of case studies on terrestrial deposits we know that Late Holocene climate fluctuations have an important impact on the terrestrial environments. However, it is hitherto not clear how the marine sediments can be used to shed light on the environment and climate change of the catchment. To provide such insight, we used the major element, trace element and rare earth element (REE) compositions in the southern Yellow Sea (SYS) sediments to reconstruct the changes in weathering and erosion of their source regions. The sediments originate predominantly from the upper crust of East China and are transported into the basin especially by the Yellow River (Huanghe) and to a lesser extent by the Yangtze River (Changjiang). The chemical index of alteration (CIA; 53.7–59.7) suggests low chemical weathering of the source rocks since the Middle Holocene. This is consistent with the relatively cool and arid climate in North China after the Holocene Megathermal. Comparison of element ratios, including Al/Ca, K/Ca, Al/Na, K/Na, Rb/Sr, Li/Ba and the CIA shows that we can use the latter as a robust proxy for climate change. The CIA-based mean annual precipitation and mean annual temperature show a series of climate fluctuations in the catchment. A relatively warm and humid Period I (5.3–2.9 cal. ka BP), a relatively cool and dry Period II (2.9–0.9 cal. ka BP) and an increasingly cool and dry Period III (0.9–0.3 cal. ka BP). These periods can be linked to climate intervals recognized elsewhere

A global monthly field of seawater pH over 3 decades: a machine learning approach

The continuous uptake of anthropogenic CO2 by the ocean leads to ocean acidification, which is an ongoing threat to the marine ecosystem. The ocean acidification rate was globally documented in the surface ocean but limited below the surface. Here, we present a monthly four-dimensional 1°×1° gridded product of global seawater pH, derived from a machine learning algorithm trained on pH observations at total scale and in-situ temperature from the Global Ocean Data Analysis Project (GLODAP). The constructed pH product covers the years 1992–2020 and depths from the surface to 2 km on 41 levels. Three types of machine learning algorithms were used in the pH product construction, including self-organizing map neural networks for region dividing, a stepwise algorithm for predictor selection, and feed-forward neural networks (FFNN) for non-linear relationship regression. The performance of the machine learning algorithm was validated using real observations by a cross validation method, where four repeating iterations were carried out with 25 % varied observations for each evaluation and 75 % for training. The constructed pH product is evaluated through comparisons to time series observations and the GLODAP pH climatology. The overall root mean square error between the FFNN constructed pH and the GLODAP measurements is 0.028, ranging from 0.044 in the surface to 0.013 at 2000 m. The pH product is distributed through the data repository of the Marine Science Data Center of the Chinese Academy of Sciences at http://dx.doi.org/10.12157/IOCAS.20230720.001 (Zhong et al., 2023)

Characterization of Shiga toxin-producing Escherichia coli isolated from healthy pigs in China

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) is recognized as an important human diarrheal pathogen. Swine plays an important role as a carrier of this pathogen. In this study we determined the prevalence and characteristics of STEC from healthy swine collected between May 2011 and August 2012 from 3 cities/provinces in China. RESULTS: A total of 1003 samples, including 326 fecal, 351 small intestinal contents and 326 colon contents samples, was analyzed. Two hundred and fifty five samples were stx-positive by PCR and 93 STEC isolates were recovered from 62 stx-positive samples. Twelve O serogroups and 19 O:H serotypes including 6 serotypes (O100:H20/[H20], O143:H38/[H38], O87:H10, O172:H30/[H30], O159:H16, O9:H30/[H30]) rarely found in swine and ruminants were identified. All 93 STEC isolates harbored stx(2) only, all of which were stx(2e) subtype including 1 isolate being a new variant of stx(2e). 53.76%, 15.05% and 2.15% STEC isolates carried astA, hlyA and ehxA respectively. Four STEC isolates harbored the high-pathogenicity island. Of the 15 adherence-associated genes tested, 13 (eae, efa1, iha, lpfA(O113), lpfA(O157/OI-154), lpfA(O157/OI-141), toxB, saa, F4, F5, F6, F17 or F41) were all absent while 2 (paa and F18) were present in 7 and 4 STEC isolates respectively. The majority of the isolates were resistant to tetracycline (79.57%), nalidixic acid (78.49%), trimethoprim-sulfamethoxazole (73.12%) and kanamycin (55.91%). The STEC isolates were divided into 63 pulsed-field gel electrophoresis patterns and 21 sequence types (STs). Isolates of the same STs generally showed the same or similar drug resistance patterns. A higher proportion of STEC isolates from Chongqing showed multidrug resistance with one ST (ST3628) resistant to 14 antimicrobials. CONCLUSIONS: Our results indicate that swine is a significant reservoir of STEC strains in China. Based on comparison by serotypes and sequence types with human strains and presence of virulence genes, the swine STEC may have a low potential to cause human disease

Streptococcus suis Sequence Type 7 Outbreak, Sichuan, China

An outbreak of Streptococcus suis serotype 2 emerged in the summer of 2005 in Sichuan Province, and sporadic infections occurred in 4 additional provinces of China. In total, 99 S. suis strains were isolated and analyzed in this study: 88 isolates from human patients and 11 from diseased pigs. We defined 98 of 99 isolates as pulse type I by using pulsed-field gel electrophoresis analysis of SmaI-digested chromosomal DNA. Furthermore, multilocus sequence typing classified 97 of 98 members of the pulse type I in the same sequence type (ST), ST-7. Isolates of ST-7 were more toxic to peripheral blood mononuclear cells than ST-1 strains. S. suis ST-7, the causative agent, was a single-locus variant of ST-1 with increased virulence. These findings strongly suggest that ST-7 is an emerging, highly virulent S. suis clone that caused the largest S. suis outbreak ever described

Evolution of Marine Environmental Health in Jiaozhou Bay in Recent 40 Years Based on the 'Dual Core'Assessment Framework

Based on the "dual core" framework for assessing the health status of the offshore ecological environment, the marine environmental health status of Jiaozhou Bay in the past 40 years was comprehensively evaluated, and the evolution process of the ecological environment of Jiaozhou Bay along with the economic and social development of Qingdao was combed. Taking every 10 years as an interval, the "double core" assessment results of the marine ecological environment health of Jiaozhou Bay in the past 40 years are as follows: "good +0.22" from 1981 to 1990, "excellent +0.53" from 1991 to 2000, "good +0.87" from 2001 to 2010 and "excellent +0.90" from 2011 to 2020. With the economic and social development of Qingdao, human beings have made greater efforts to develop and utilize the marine resources and environment of Jiaozhou Bay, and various ecological problems have also occurred in Jiaozhou Bay: the water quality deteriorated in the 1980s, the health status of biological communities declined in the 1990s, and the problem of eutrophication was serious in the 2000s. Since 2010, Qingdao has strengthened ecological protection and environmental governance, and the marine ecological environment of Jiaozhou Bay has been significantly improved. With the acceleration of the transformation of old and new kinetic energy and the continuous optimization and upgrading of industrial structure, the disturbance of economic development activities to the marine ecological environment of Jiaozhou Bay has been continuously reduced. Qingdao has finally realized a benign and healthy green development model between marine economy and ecological environment for Jiaozhou Bay

pCO(2) and carbon fluxes across sea-air interface in the Changjiang Estuary and Hangzhou Bay

Partial pressure of CO(2) (pCO(2)) was investigated in the Changjiang (Yangtze River) Estuary, Hangzhou Bay and their adjacent areas during a cruise in August 2004, China. The data show that pCO(2) in surface waters of the studied area was higher than that in the atmosphere with only exception of a patch east of Zhoushan Archipelago. The pCO(2) varied from 168 to 2 264 mu atm, which fell in the low range compared with those of other estuaries in the world. The calculated sea-air CO(2) fluxes decreased offshore and varied from -10.0 to 88.1 mmol m(-2) d(-1) in average of 24.4 +/- 16.5 mmol m(-2) d(-1). Although the area studied was estimated only 2 x 10(4) km(2), it emitted (5.9 +/- 4.0) x 10(3) tons of carbon to the atmosphere every day. The estuaries and their plumes must be further studied for better understanding the role of coastal seas playing in the global oceanic carbon cycle

Carbon Chemistry in the Mainstream of Kuroshio Current in Eastern Taiwan and Its Transport of Carbon into the East China Sea Shelf

Comprehensive carbon chemistry data were measured from the mainstream of Kuroshio, off eastern Taiwan, in May 2014. Results indicated that variations of pH@25 °C, POC, ΩCa, DIC, pCO2 and RF were closely related to the characteristics of various water types. Phytoplankton photosynthesis played important roles in DIC variation in Kuroshio Surface Water (KSW), whereas the DIC variation in Kuroshio Subsurface Water (KSSW) was probably influenced by the external transport of DIC-enriched water from the South China Sea. Vertical profiles of hydrological parameters and carbonate species indicated that the Kuroshio Current off eastern Taiwan could intrude into the ECS shelf as far as 27.9° E, 125.5° N in spring. What is more, the KSW, KSSW and Kuroshio Intermediate Water (KIW) could convey DIC into the East China Sea (ECS) with flux of 285, 305 and 112 Tg C/half year (1 Tg = 1012 g), respectively. The relevant flux of POC was 0.16, 2.93 and 0.04 Tg C/half year, respectively. Consequently, the intrusion of Kuroshio could probably exert a counteracting influence on the potential of CO2 uptake in the ECS, which needs further study

Characterization, Source and Risk of Pharmaceutically Active Compounds (PhACs) in the Snow Deposition Near Jiaozhou Bay, North China

The occurrence and distribution of 110 pharmaceutically active compounds (PhACs) were investigated in snow near Jiaozhou Bay (JZB), North China. All target substances were analyzed using solid phase extraction followed by liquid chromatography coupled to tandem mass spectrometry.A total of 38 compounds were detected for the first time in snow, including 23 antibiotics, eight hormones, three nonsteroidal anti-inflammatory drugs, two antipsychotics, one beta-adrenergic receptor and one hypoglycemic drug. The total concentration of PhACs in snow ranged from 52.80 ng/L to 1616.02 ng/L. The compounds found at the highest mean concentrations included tetracycline (125.81 ng/L), desacetylcefotaxime (17.73 ng/L), ronidazole (8.79 ng/L) and triamcinolone diacetate (2.84 ng/L). The contribution of PhACs in the vicinity of JZB to the PhACs in the snow is far greater than the contribution of those transmitted over a long distance. PhACs are mainly derived from drugs applied to local humans and animals. Based on the individual risk quotient (RQ) values, tetracycline poses high risks to the relevant aquatic organisms (algae and invertebrates). The rational application and scientific management of PhACs is an effective approach to reduce the ecological risks in JZB