Modelling the upwelling offthe east Hainan Island coast in summer 2010

A synoptic-scale upwelling event that developed off the east coast of the Hainan Island(EHIU) in the summer of 2010 is defi ned well via processing the Moderate Resolution Imaging Spectroradiometer(MODIS) sea surface temperature(SST) data. The Regional Ocean Modeling System(ROMS) with high spatial resolution has been used to investigate this upwelling event. By comparing the ROMS results against tide station data, Argo fl oat profi les and MODIS SST, it is confi rmed that the ROMS reproduces the EHIU well. The cooler-water core(CWC) distinguished by waters(27) 27.5°C in the EHIU, which occurred in the east Qiongzhou Strait mouth area and was bounded by a high temperature gradient, was the focus of this paper. Vertical structure of the CWC suggests that interaction between the westward fl ow and the bathymetry slope played a signifi cant role in the formation of CWC. Numerical experiments indicated that the westward fl ow in the Qiongzhou Strait was the result of tidal rectifi cation over variable topography(Shi et al., 2002), thus tides played a critical role on the development of the CWC. The negative wind stress curl that dominated the east Qiongzhou Strait mouth area suppressed the intensity of the CWC by 0.2–0.4°C. Further, nonlinear interaction between tidal currents and wind stress enhanced vertical mixing greatly, which would benefi t the development of the CWC.     

Sources of sediment in tidal fl ats off Zhejiang coast,southeast China

The growth of tidal fl ats off Zhejiang coasts in southwestern China has provided substantial areas for local agriculture and construction activities. To evaluate modern and future development of tidal fl ats in the region, a good understanding of sediment sources is necessary. Previous research has concluded that the Changjiang(Yangtze) River is the dominant supplier of sediments to this part of the southeast Chinese coast, despite the fact that sediment delivery from this source has been decreased markedly in the past two decades. In this study, we investigated the sources of tidal fl at sediments, and the magnetic and geochemical properties of recent tidal fl at sediments along the Zhejiang coast were compared with those discharged from rivers. Magnetic and geochemical properties of the tidal fl at samples reveal statistically distinct sediment provenance groups. The magnetic and geochemical scatter plots show that the suspended sediment samples are naturally divided into two diff erent groups, one including the Changjiang River and Qiantang River material, and the other including the Jiaojiang, Oujiang, and Feiyun Rivers that located in the central and southern parts of the study areas. At last, a binary source of tidal fl at sediments along the Zhejiang coast was determined, with the substantial majority originating from local rivers, while a much smaller proportion emanates from the Changjiang River to the north. We conclude that the sediment contribution of the Changjiang River to tidal fl at development in the region has been markedly overestimated, with important implications for management.     

Numerical simulation of the structure and variation of upwelling off the east coast of Hainan Island using QuikSCAT winds

The spatial structure and variation of the upwelling in the waters east and northeast of Hainan Island, China during 2000-2007 were investigated using a nested high-resolution Princeton Ocean Model (POM) forced by QuikSCAT winds. The model produced good simulations of the summer upwelling and the seasonal and annual variability. Strong upwelling occurs from mid-July to mid-August with a peak east of Hainan Island associated with the southwesterly monsoon in the South China Sea. Sensitivity experiments indicated that when the local wind stress controls the variability of the upwelling, the large-scale circulation significantly enhances the upwelling northeast of Hainan Island by inducing a local upwelling and transporting cold water northeast-ward along the island’s east coast. The joint effects of the local wind stress and large-scale circulation result in stronger upwelling northeast of Hainan Island. This implies that the annual variation of the upwelling northeast of Hainan Island is controlled not only by the local alongshore wind stress but also by the large-scale circulation. This result will help us investigate the decadal variation of the upwelling in this region in the future.     

Nutrient structure of the Taiwan Warm Current and estimation of vertical nutrient fluxes in upwelling areas in the East China Sea in summer

Based on field data for nutrients collected on the continental shelf of the East China Sea (ECS) during summer 2006, the structure and variations of nutrients in every water mass related to the Taiwan Warm Current (TWC) were analyzed. The supplementary effect of nutrient of upwelling on harmful algal blooms (HABs) in the ECS was also estimated, based on upwelling data. Then the maintenance contribution of nutrient of upwelling to HABs was assessed. The results showed that N/P ratio is fairly low in both surface and deep layers of the TWC, which possibly controls nutrient structure of the HABs-frequently-occuring areas. In upwelling areas, the rate of phosphate (PO₄-P) uptake exceeds that of nitrate (NO₃-N) of the TWC. The TWC may relieve PO₄-P limitation during the process of HABs. Furthermore, upwelling plays an important role in providing nutrients to HABs. After estimating nutrient fluxes (NO₃-N, PO₄-P, SiO₃-Si) in the upwelling areas along a typical section (S07), the results showed that the nutrient uptake rate is the greatest at 10–20 m below euphotic zone, sustaining the ongoing presence of HABs. The uptake rate of PO₄-P is the highest among dissolved inorganic nutrients. Therefore, upwelling is most likely the main source of PO₄-P supply to HABs.     

COMBINED EFFECTS OF TEMPERATURE, IRRADIANCE AND SALINITY ON GROWTH OF DIATOM SKELETONEMA COSTATUM

3-factor experiment was used to study the combined effects of temperature, irradiance and salinity on the growth of an HAB species diatomSkeletonema costatum (Grev.) Cleve. The results showed that temperature (12, 19, 25, 32 °C), irradiance (0.02, 0.08, 0.3, 1.6)×10¹⁶ quanta/(s·cm²)) and salinity (10, 18, 25, 30, 35) significantly influenced the growth of this species. There were interactive effects between any two of and among all three physical factors on the growth. In the experiment, the most optimal growth condition forS. costatum was temperature of 25°C, salinity of 18–35 and irradiance of 1.6×10¹⁶ quanta/(s·cm²). The results indicatedS. costatum could divide at higher rate and were more likely to bloom under high temperature and high illumination from spring to fall. It was able to distribute widely in ocean and estuary due to its adaptation to a wide range of salinities. This study was supported by the PREPP and National Key Basic Research Project (2001CB4097) NNSFC No. 39950001, 20177023, 49576301, 49906007 and KZCX2-206.     

Phytoplankton community dynamics during Alexandrium blooms in 2019 off the Qinhuangdao coast,Bohai Sea,China

Journal of Oceanology and Limnology - Alexandrium blooms in the northwest area of the Bohai Sea (Qinhuangdao coastal area), China, produce large amounts of toxins that could be enriched in...     

Exercise in downscaling on sea surface temperature along Chinese coast

ＩＮＴＲＯＤＵＣＴＩＯＮＡｎｔａｒｃｔｉｃｋｒｉｌｌ(ＥｕｐｈａｕｓｉａｓｕｐｅｒｂａＤａｎａ)ｉｓａｋｅｙｏｒｇａｎｉｓｍｏｆｔｈｅＡｎｔａｒｃｔｉｃｍａｒｉｎｅｅｃｏｓｙｓｔｅｍａｎｄａｐｏｔｅｎｔｉａｌｆｉｓｈｅｒｙｒｅｓｏｕｒｃｅ.Ｉｔｈａｓｂｅｅｎｔｈｅｓｕｂｊｅｃｔｏｆｍｕｃｈｒｅｓｅａｒｃｈ.Ｄｅｓｐｉｔｅｔｈｅｌｏｎｇｈｉｓｔｏｒｙｏｆｒｅｓｅａｒｃｈｄａｔｉｎｇｂａｃｋｔｏｔｈｅ1930’ｓ,ｔｈｅｒｅａｒｅｓｔｉｌｌｑｕｅｓｔｉｏｎｓａｂｏｕｔｉｔｓｐｏｐｕｌａｔｉｏｎｓｔｒｕｃｔｕ…     

Role of Ekman transport versus Ekman pumping in driving summer upwelling in the South China Sea

Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea (SCS) are examined using QuikSCAT scatterometer wind data. The major upwelling regions in the SCS are the coastal regions east and southeast of Vietnam (UESEV), east and southeast of Hainan Island (UESEH), and southeast of Guangdong province (USEG). It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems. In UESEV, Ekman pumping and Ekman transport are equally important in generating upwelling. The Ekman transport increases linearly from 0.49 Sv in May to 1.23 Sv in August, while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period. In UESEH, the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv, respectively, indicating that 33% of the total wind-driven upwelling is due to Ekman pumping. In USEG, the mean Ekman transport is 0.041 Sv with the peak occurring in July, while Ekman pumping is much smaller (0.003 on average), indicating that the upwelling in this area is primarily driven by Ekman transport. In the summers of 2003 and 2007 following El Niño-Southern Oscillation (ENSO) events, both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon. During the same events, however, Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG.     

Effects of temperature, salinity, light intensity, and pH on the eicosapentaenoic acid production of Pinguiococcus pyrenoidosus

The effects of temperature, light intensity, salinity, and initial pH on the growth and fatty acid composition of Pinguiococcus pyrenoidosus 2078 were studied for eicosapentaenoic acid (EPA) production potential. The fatty acid composition was assayed by gas chromatography-mass spectrometry, which indicated that the main fatty acids were C14:0, C16:0 and EPA. The highest EPA percentage 20.83% of total fatty acids was obtained at 20℃ with the temperature being set at 20, 24, and 28℃. Under different salinities and light intensities, the highest percentages of total polyunsaturated fatty acids (PUFAs) and EPA were 17.82% and 31.37% of total fatty acids, respectively, which were achieved at salinity 30 and 100μmol photon m-2s-1 illumination. The highest percentages of total PUFAs and EPA were 38.75% and 23.13% of total fatty acids, respectively, which were reached at an initial pH of 6 with the test range being from 5.0 to 9.0.     

Evidence for a counter-wind current in winter off the southeast coast of China

Regarding the current pattern in winter in the near-sea region of Zhejiang, Fujian and Guangdong (including the western and central parts of the Taiwan Strait), oceanographers both at home and abroad had considered unanimously that under the intense influence of the northerly monsoon, the current (not only at the surface but also in the deep and near-bottom layers) flows southwestward with the wind. It was not until the end of the fifties that scientists began to question such a traditional concept. In this paper, based on the results of more than 20 years’ studies on the current patterns of the East China and South China Seas, all kinds of current data available are reanalysed comprehensively. These data include: 1) current measurements at day-night anchored stations, and with mooring buoys, collected mostly from 1959 to 1982 by many Chinese oceanographic and fisheries organizations; 2) current vectors derived from the ship-drift of Japanese naval vessels in the period from 1910 to 1921; and 3) geostrophic current velocities deduced from hydrographic observations in the periods of the CSK and 1975–1976 conducted by the Fisheries Research Station, Hong Kong, and the SOA. A combination of all the evidences revealed in the above data suggests and confirms that, besides the China Coastal Current flowing southwestward at a shallow layer of a zone closely adjacent to the coast, there also exists a northeastward counter-wind current in winter off the southeast coast of China (though its surface current may be weakened or even covered up by the drift current when the northerly monsoon strengthens). Furthermore, the two parts of the winter counter-wind current in the South China Sea and the East China Sea are connected through the Taiwan Strait. This suggestion now has been confirmed by the recent observations in the Taiwan Strait, i.e., 1) with sea-bed drifters released in 1984 (Zhang, 1985) and 2) with current meter moorings deployed in 1983 (Chuang, 1985). It is suggested that detailed field investigation in winter for filling the gap of observations should be needed to give further confirmation of this important new finding. At the same time, dynamical, numerical and experimental studies should also be carried out for a better understanding of the mechanism of this counter-wind current, and its variations and correlation with the adjacent currents, such as the southward flowing coastal current and the northward flowing Kuroshio Branch. The paper was presented at the symposium sponsored by the Chinese Society of Oceanology and Limnology in November, 1978, Qingdao. Some recent contents were supplemented before publication. Contribution No. 1364 from the Institute of Oceanology, Academia Sinica.     

Impacts of salinity parameterizations on temperature simulation over and in a hypersaline lake

In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model(WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model,which is the land component of the WRF-CLM model. The Great Salt Lake(GSL) in the USA was selected as the study area. The simulation was performed from September 3,2001 to September 30,2002. Our results show that the modif ied WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects,particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However,the salinity effect on thermal conductivity was found insignificant in our simulations.     

Effects of temperature and salinity on the asexual reproduction of Aurelia coerulea polyps

Aurelia coerulea polyp is an important stage in the outbreaks of this species. To test the combined ef fects of salinity and temperature on the survival and asexual reproduction of polyps, we maintained 864 polyps at various salinities(15, 25, 33, and 40) and temperatures(9, 12, 15, 18, 21, and 24℃). Polyps could mostly survive in all treatment combinations except in salinity 15 treatments with low temperatures(9–15℃). Budding occurred at all temperatures(9–24℃), while strobilation only occurred at the low temperatures(9–15℃). The range of 12–15℃ was suitable for strobilation and ephyrae release. The optimal range of salinity for asexual reproduction was 25–33. Low(15) or high(40) salinity could signi?cantly reduce the numbers of new buds or ephyrae, and low salinity of 15 retarded and even prevented strobilation at low temperatures. The optimal treatment for budding and strobilation was 21℃-salinity 25 and 12℃-salinity 33, respectively. Salinity had less of an impact than temperature on asexual reproduction, except for the polyps in high or low osmotic pressure conditions.     

Effects of salinity, light and temperature on growth rates of two species of Gracilaria (Rhodophyta)

Effects of temperature, salinity and light intensity on growth rates of Gracilaria lichenoides and G tenuistipitata var. liui Zhang et Xia were tested. Eight to ten levels of each factor were first tested separately. The best growth rate was obtained under the conditions of 32～C, 30 and 240 μmol/(m2·s) for G. lichenoides, and 24℃, 20 and 200 μmol/(m2.s) for G. tenuistipitata, respectively. Then a uniform design was used to evaluate the optimal combinations of the three factors. The best conditions for the highest daily specific growth rates (% increase in wet weight) are determined to be 31.30℃, 32.10, and 287.23 μmol/(m2·s) for G. lichenoides (16.26%/d), and 25.38℃, 21.10, and 229.07 μmol/(m2·s) for G. tenuistipitata (14.83%/d), respectively.     

Effects of salinity, light and temperature on growth rates of two species of Gracilaria （Rhodophyta）

Effects of temperature, salinity and light intensity on growth rates of Gracilaria lichenoides and G. tenuistipitata var. liui Zhang et Xia were tested. Eight to ten levels of each factor were first tested separately. The best growth rate was obtained under the conditions of 32°C, 30 and 240 μmol/(m²·s) for G. lichenoides, and 24°C, 20 and 200 μmol/(m²·s) for G. tenuistipitata, respectively. Then a uniform design was used to evaluate the optimal combinations of the three factors. The best conditions for the highest daily specific growth rates (% increase in wet weight) are determined to be 31.30°C, 32.10, and 287.23 μmol/(m²·s) for G. lichenoides (16.26%/d), and 25.38°C, 21.10, and 229.07 μmol/(m²·s) for G. tenuistipitata (14.83%/d), respectively. Supported by the 908 Special Program (908-02-04-07), the National Basic Research Program of China (973 Program, No. 2006CB400608), and K. C. Wong Magna Fund in Ningbo University     

Regional summer temperature decrease against global warming in China, landform effect?

The data of 160 national meteorological observatory (NMO) stations with long-term monthly temperature data for China were analyzed in this study to show the basin-centered summer temperature decrease against global warming in the past half century. The summer and winter isotherm structures of 1950s and 1990s worked out by interpolation show the isotherm structure variations: the isotherm structure generally moves northward in winter, but in summer it is characterized with separate high-temperature and low-temperature centers and the isotherm structure moves inward the centers with global warming, indicating that the temperature in the highland areas increases but that in the lowland areas decreases in the summer of the duration. The possible mechanism of the basin-centered temperature decrease in summer is discussed in this paper.     

Effects of temperature and salinity on survival,growth and DNA methylation of juvenile Pacific abalone,Haliotis discus hannai Ino

Temperature and salinity are two of the most potent abiotic factors infl uencing marine mollusks.In this study,we investigated the individual and combined ef fects of temperature and salinity on the survival and growth of juvenile Pacifi c abalone,Haliotis discus hannai Ino,and also examined the DNA methylation alteration that may underpin the phenotypic variation of abalone exposed to dif ferent rearing conditions.The single-factor data showed that the suitable ranges of temperature and salinity were 16–28°C at a constant salinity of 32,and 24–40 at a constant temperature of 20°C,respectively.The two-factor data indicated that both survival and growth were signifi cantly af fected by temperature,salinity and their interaction.The optimal temperature-salinity combination for juveniles was 23–25°C and 30–36.To explore environment-induced DNA methylation alteration,the methylation-sensitive amplifi ed polymorphism(MSAP)technique was used to analyze the genomic methylation profi les of abalone reared in optimal and adverse conditions.Neither temperature nor salinity induced evident changes in the global methylation level,but 67 and 63 dif ferentially methylated loci were identifi ed in temperature and salinity treatments,respectively.The between-group eigen analysis also showed that both temperature and salinity could induce epigenetic dif ferentiation in H.discus hannai Ino.The results of our study provide optimal rearing conditions for juvenile H.discus hannai Ino,and represent the fi rst step toward revealing the epigenetic regulatory mechanism of abalone in response to thermal and salt stresses.     

Metabolism of polychaete Neanthes japonica Izuka: relations to temperature, salinity and body weight

Polychaete Neanthesjaponica is a species geographically specific in China and Japan with important scientific implication and commercial value. In this study, the relations of body weight, salinity and temperature to oxygen consumption and ammonia excretion of N. japonica were determined. Threedifferent groups in body weight (large: 2.34±0.36 g, middle: 1.50±0.21 g and small: 0.62±0.12 g) were set for all experiments. Results show that the body weight is negatively related to the rates of oxygen consumption and ammonia excretion; and the relationship is significant. The oxygen consumption and ammonia excretion at 24℃ decreased at salinity from 5 to 30 and increased above 30, indicating that both lower and higher salinity are adverse and certain degree of salinity stress is necessary for enhancing the energy demand. At salinity 30, rising temperature from 18℃ to 30℃, the oxygen consumption increased before 27℃ and then decreased. However, the relation of ammonia excretion and temperature seems more complex. Two-way ANOVA shows that salinity, temperature and body weight all have a significant effect on the oxygen consumption and ammonia excretion of the worm. Moreover, interaction between salinity/temperature and body weight is also significant. O:N (oxygen/nitrogen) ratio varies greatly in this case from 5.97 to 463.22, indicating that N. japonica can regulate the type of metabolic substrate against environment changes.     

LATE QUATERNARY SEISMIC SEQUENCES AND SEDIMENTATION ALONG THE COAST OFF TAISHAN, GUANGDONG, AS REVEALED BY HIGH RESOLUTION SEISMIC DATA

Seismic stratigraphic analysis of 150 km of high-resolution seismic profiles (GEO-PULSE and 3.5 kHz) obtained along the muddy coast off Taishan, Guangdong provided valuable information on the offshore Quaternary stratigraphy, tectonics, sedimentary evolution, and environmental and engineering geology of this area. The following late Quaternary stratigraphic sequences were mapped. (1) Pleistocene alluvial silty sand and shallow marine clay; (2) coarse fluvial channel sand; (3) nearshore and bay clayey sediments. The incision of fluvial channels occurred in two stages: dttring the Late Pleistocene and at the beginning of the Holocene. The Pleistocene fluvial channels have been filled by coarses and overlain by more than 10 m of late Pleistocene clay and 20 - 30 m of Holocene clay. The coastal area is dissected by two major fault systems: the first group strikes ENE-WSW and controls the evolution of the adjacent Quaternary basin, while the second one trends NNE-SSW. These fault systems must be taken into account in any coastal engineering considerations. In addition, both granitic and metamorphic basements were recognized.     

Study on the transport of COD in the sea area around Maidao off Qingdao coast using data assimilation

A two-layer pollutant advection-diffusion model is built to investigate the pollutant transport in the sea area around Maidao off Qingdao coast. An adjoint data assimilation technique is applied to estimate the optimal values of the model parameters. The experimental results on the initial field of pollutant indicate that the distribution of Chemical Oxygen Demand (COD) concentra- tion is sensitive to the horizontal eddy diffusivity. An appropriate value of horizontal eddy diffusivity is necessary in order to depict the influence of the initial field precisely, and it is also essential to the simulation of the advection-diffusion process of the pollutant. By inversion of the model parameters and optimization of the initial COD concentrations, the simulation results are improved sig- nificantly. The cost function is reduced to 40% of its first step value. The average misfit between the model outputs and the observa- tions in the upper layer decreases from 0.46 to 0.25 mg L-1, and that in the lower layer decreases from 0.22 to 0.14 mg L-1.