Size-fractionated phytoplankton standing stock and primary production in the Bohai Sea during late spring

During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-fractionated chlorophyll a (Chl a) and primary production, photosynthet-ically available radiation (PAR), as well as the related physico-oceanographic and zooplanktonic parameters were measured at five time-series observation stations representing sub-areas of the sea. Results obtained show that there were the marked features of spatial zonation of Chl a and primary production in the Bohai Sea. The values in the Laizhou Bay, the Liaodong Gulf and the Bohai Gulf were high and showed close relation with tidal fluctuations, i.e. high Chl a concentration occurred during high tide in the Laizhou Bay, and during low tide in the Liaodong Gulf and the Bohai Gulf. In the strait and the central region of the Bohai Sea, the values were relatively low and no relationship with tidal fluctuation could be foun     

Sea-ice-thickness variability in the Chukchi Sea,spring and summer 2002–2004

Measurements of sea-ice thickness were obtained from drill holes, an ice-based electromagnetic induction instrument (IEM), and a ship-borne electromagnetic induction instrument (SEM) during the early-melt season in the southern Chukchi Sea in 2002 and 2004, and in late summer 2003 at the time of minimum ice extent in the northern Chukchi Sea. An ice roughness criterion was applied to distinguish between level and rough or ridged ice. Ice-thickness modes in the probability density functions (PDFs) derived from drill-hole and IEM measurements agreed well, with modes at 1.5–1.6 and 1.8–1.9 m for all data from level ice. The PDFs derived from SEM measurements show that the primary modes are at 0.1 and 1.1 m in 2003 and 0.7 m in 2004. In 2002 and 2004, significant fractions (between one-third and one-half) of level ice were found to consist of rafted ice segments. Snow depth varied significantly between years, with 2004 data showing more than half the snow cover on level ice to be at or below 0.05 m depth in late spring. Ice growth simulations and examination of ice drift and deformation history indicate that impacts of atmospheric and oceanic warming on level-ice thickness in the region over the past few decades are masked to a large extent by variability in snow depth and the contribution of deformation processes. In comparison with submarine sonar ice-thickness data from previous decades, a reduction in ice thickness by about 0.5–1 m is in part explained by the replacement of multi-year with first-year ice over the Chukchi and Beaufort shelves.     

Nutrients concentration and changes in decade-scale in the central Bohai Sea

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Numerical Simulation of Transportation of SPM from the Yellow River to the Bohai Sea

1 .IntroductionThe records at the Lijin Station showthat almost 1 .34 bt of sediment of the Yellow River waspouredintothe Bohai Sea annuallyfrom1855 to 1988 (Qianet al.,1993 ; Wang and Zhang,1998) .The Yellow River has shifted its trunk streamto the Qings…     

Distribution pattern of marine flagellate and its controlling factors in the central and north part of the Huanghai Sea in early summer

Abstract-A survey was carried out in the central and north part of the Huanghai Sea (34.5°～37.0°N, 120.5°～124.0°E) during June 12～27, 2000. It was found that the abundance of marineflagellate ranged from 45 to 1278 cell/ml, 479 cell/ml in average. Flagellate was more abundant in thecentral part than in the north part of Huanghai Sea, and the abundance decreased with the increasingdistance from the coast, showing a similar distribution pattern with isotherm. Vertically, high densityof flagellate was always presented in the bottom of thermocline, and formed a dense accumulation in thecentral area of the Huanghai Sea Cold Water Mass. The effects of physical and biological factors on thedistribution of marine flagellate in early summer were discussed. Water temperature (especially the ex-istence of thermocline) rather than salinity showed significant effect on the distribution pattern of marineflagellate in the Huanghai Sea in early summer. When comparing the abundance of marine flagellatewith that o     

Phytoplankton-pigment signatures and their relationship to spring–summer stratification in the Gulf of Gabes

We investigated the phytoplankton dynamics (determined by CHEMTAX analysis of HPLC pigment data) and its relationships with nutrients and water column structure, during two oceanographic cruises in May–June and September 2006 in the Gulf of Gabes (south-eastern Mediterranean). The May–June cruise coincided with the beginning of the summer stratification, while a strong stratification occurred in September with a more than 30 m deepening of the thermocline, and a reduction of the euphotic depth. This strong stratification resulted in a shift in nitrogen sources from nitrates to ammonium as well as phosphate depletion (0.2 μM) and a decrease in silicate concentrations (<2 μM). With the exception of chlorophyll a, pigment concentrations were higher in September than in May–June samplings. The pico- and nanophytoplankton were the major contributors to phytoplankton total biomass, accounting for 90% and 87% of total chlorophyll a in May–June and September, respectively. Picoplankton persisted throughout the entire survey, occupying different depth layers. Chlorophytes were present at substantial amounts (average 23% of total chlorophyll a) during May–June; however, they declined in September (average 5%). Diatoms were overall poorly represented in this study (2% of total chlorophyll a), due probably to silicate shortage. Apparently, the nutrient availability, but also the water column stability seemed to be among the major factors determining phytoplankton dynamics. Indeed, cyanobacteria were prominent in surface samples during the period of strong stratification, whereas the relative contribution of chlorophytes decreased, probably due to low phosphate availability.     

Modelling of the barotropic processes in the Bohai Sea

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Preliminary study on seasonal succession and development pathway of phytoplankton community in the Bohai Sea

IThe Phytoplankton spoteS succession is a major characteristic Of PhytOPlankton behavior inthe an, and is Of major swificance tO PhytOPlankton d~cs and in coupling the PhytOPlankton cornxnunity to hasher trophic levels (Smayda, 1980). But another conception species ence that be defined by BraarUd often confUSeS with speCies sucCeSSion. Spotes su~ is thechange of speCies compeition within a given water mass resulting from changing physical,chemical and biological factors within the wa…     

Relation of ice conditions to climate change in the Bohai Sea of China

1NTRODUcrIONThe bohai As is a seasonally ice-covered sea and is located in the lowest latitudes (37' -4l'N), where sea ice occurs. The bohai ffea is nearly enclosed by land in the south, the northand the west, and only connects to the Huanghai ffea through the bohai Strait in the east.The width of the strait is abeut l06 km. The boai ffea is very shallow basin with the meandepth of l8 m and the maximum depth of 78 m. The topography of the sea bottom and thecoastal regions has an importan…     

Simulation of the seasonal thermal structure in the Bohai Sea

The seasonal thermal structure in the Bohai Sea are examined with a three-dimensional boroclinic primitive equation model for shelf sea.The evolution of the seasonal thermal stratification is well simulated.The stratification appears early in April,first in the area off Qinhuangdao and it is well developed in the middle of May.It intensifies with synoptic and neap-spring fluctuations throughout the summer and reaches its maximum in the middle of July.Eventually,it is destroyed at the end of September.There are cold water belts between well-mixed and stratified regions.They are loGated on the mixed side of tidal fronts,and coincide with the isolines for a temperature difference of 1-2℃ between surface and bottom.The sea surface temperature (SST) distribution shows local maxima at the head of three bays and to the south of Qinhuangdao during the summer.The Bohai Sea responds to the variability in the atmospheric forcing and in tides with the synoptic and neap-spring variations of SST,as well as in the stratification and in variable positions of tidal fronts.     

Biomass of meiobenthic in the Bohai Sea, China

IorasMeiOfauna is a vmp imprtant pep in benthic small bo web energetica1ly duo to theirarell aize and high turnovr rates. A nde Of meMauna op be the recireulaton of nutrient8*Marine nemathe mey keep the bacterial chnies on sand grains in active phase Of gorth byfeding on bacteria, thus enhancing the recirculation Of nutrients (McIntyre, l969; Feller andWrmick, l988; MOntagna et al., l995). But energetics studie8, no matter tfor conductedon the energybudgt level for individua sPeCies or a…     

A model study on carbon cycle and phytoplankton dynamical processes in the Bohai Sea

The carbon cycle of lower trophic level in the Bohai Sea is studied with a three-dimensional biological and physical coupled model. The influences of the processes (including horizontal advection, river nutrient load, active transport etc. ) on the phytoplankton biomass and its evolution are estimated. The Bohai Sea is a weak sink of the CO2 in the atmosphere. During the cycle, 13.7% of the gross production of the phytoplankton enter the higher trophic level and 76.8 % of it are consumed by the respiration itself. The nutrient reproduction comes mainly from the internal biogeochemical loop and the rem-ineralization is an important mechanism of the nutrient transfer from organic form to inorganic. Horizontal advection decreases the total biomass and the eutrophication in some sea areas. Change in the nutrient load of a river can only adjust the local system near its estuary. Controlling the input of the nutrient, which limits the alga growth, can be very useful in lessening the phytoplankton biomass.     

Application of the four models of directional spectra in the Bohai Sea

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Investigation on the fishing ground and fishing period of the drift fishery of Spanish Mackerel in the Huanghai Sea and Bohai Sea during the spring season

The Spanish Mackerel Scomberomorus niphonius (C. et V.), a fish of the upper layer lukewarm water quick in movement, migrates over long distances in shoals. With the development of the nylon drift net the annual catch of such fish has increased rapidly. Since     

Retrieval of remotely sensed air–sea carbon flux in the Chinese Bohai Sea

ABSTRACT

Having a reliable ocean carbon flux (f(CO₂)) retrieval model is essential to monitoring the global carbon cycle and to evaluating the climate change. Remote sensing techniques provide alternatives for f(CO₂) retrieval with its advantages of wide area surveys and real-time monitoring. In the present study, a semianalytical f(CO₂) estimation model was developed based on remote sensing data and in situ measurements in the Chinese Bohai Sea. The used model performed well (R²?=?0.84) in deriving f(CO₂) based on the collected remotely sensed dataset, including sea surface temperature, estimated sea surface salinity, wind speed, Chl-a concentration. The results showed that the distribution of partial pressure of carbon dioxide (p(CO₂)) and f(CO₂) varied spatially and temporally during the 12 months in 2009. The spatial fluctuations of p(CO₂) and f(CO₂) in Bohai Sea in summer and autumn were more obvious than that in Spring and Winter. The highest values of p(CO₂) and f(CO₂) generally appeared in coastal regions. Moreover, the average f(CO₂) value of the 12 months showed that the Bohai Sea performed as a weak carbon source in 2009. The results provided technical and data support for carbon management and climate negotiation in the Bohai Sea.     

Some numerical experiments of the dynamics of the wintertime circulation in the Northern Huanghai Sea and the Bohai Sea

Some numerical experiments have been developed to explain dynamically the mechanism of the formation of the wintertime circulation in the Northern Huanghai Sea and the Bohai Sea. From the results of the numerical experiments with Coriolis parameter having positive and negative values respectively, it is found that the current pattern characterized by flowing into the Bohai Sea in the northern part of the Bohai Straits and flowing out of the Bohai Sea in the southern part of the Bohai Straits is controlled basically by the bottom topography with "the deepness on the northern side and shallowness on the southern side'in the Bohai Straits, and is not related to Coriolis parameter having positive and negative values. It also shows that the Huanghai Warm Current regarded as the inllow condition passing through the in-ports at the water boundary of the numerical experiments only influences the region near the water boundary and the eastern region of the Northern Huanghai Sea. In addition, the mechanism of the     

Changes in the population structure of Calanus sinicus during summer–autumn in the southern Yellow Sea

Calanus sinicus is a calanoid copepod widely distributed in coastal waters of China and Japan, and oversummering strategies may have major impacts on their population dynamics which in turn affect local marine food web structure. The abundance, stage composition, and sex composition of the planktonic copepod C. sinicus were studied from August to October 2002 in the southern Yellow Sea to understand how its population recovers from the over-summering state. Results showed that C. sinicus had low reproduction in August due to high temperature, except in waters near the Cheju Island with rich food and moderate bottom temperature, but the reproduction rates here decreased in September–October as food availability declined. When temperature dropped in September–October, C. sinicus actively propagated in coastal shallow waters. However, reproduction rates of C. sinicus individuals inhabiting the Yellow Sea Cold Water Mass(YSCWM) remained low during the three months of the study. The percentage of C. sinicus females was high during the reproductive period, which suggests that the sex composition of adult C. sinicus may reflect whether or not the population is in the reproductive mode.Numerous fifth copepodite stage(CV) C. sinicus aggregated in the YSCWM in a suspended developmental stage during the three months of this study, and they potentially served as the parental individuals for population development when conditions became optimal for reproduction later in the year.     

Retrieval of total suspended matter from MODIS 250?m imagery in the Bohai Sea of China

Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua and Terra satellites have unique advantages for monitoring coastal waters, owing to their high spatial resolution (250?m), short revisit period (1–2?days), and freedom from cost. An empirical retrieval model for concentration of total suspended matter (TSM) has been developed based on a statistical analysis of field surveys of TSM and remote sensing reflectance (R _rs) in the Bohai Sea of China. A robust linear relationship was established between the equivalent remote sensing reflectance (converting ASD-measured R _rs by spectral response function) in the 620–670?nm band (band 1) of MODIS and the concentration of TSM (R ²?=?0.95; n?=?27; RMS?=?0.512) acquired in August and September 2008. The model was validated via in situ measurements in September 2009, resulting in a mean relative error of 12.9?%. Then, the corresponding MODIS products of monthly average concentration of TSM were produced from January to December 2009. The distribution characteristics of TSM in the Bohai Sea of China are closely related with the spatial pattern and seasonal variability. This study demonstrates that the moderately high resolution of MODIS 250?m data is available for monitoring the transport and fate of materials in relatively smaller bodies of water.     

Several significant hydrographic characteristics and their formation mechanism in the South China Sea during the spring and summer of 1998

INTRODUCTIONTheSCSisthelargestmarginseainthewestoftheNorthPacificOcean .Theprevailingwindinwinterisnortheast,whileinsummeritissouthwest .Itisstilluncertainthathowthecirculationandtemperature -salinityfieldassociatewiththemonsoonforcingandaccompanywithseveralkindsofvariationsbeforeorafterthesummermonsoonburst .DuringSECMEXin 1 998,twointensiveobservationperiods (IOP)havebeencarriedoutntheSCS (Fig 1 ) :IOP1 ,from 1 0Aprilto 5May ;IOP2 ,from 1 2JunetoJuly 6 ,inordertounderstandthe…     

Dissolution of silica accompanied by oxygen consumption in the bottom layer of Japan’s central Seto Inland Sea in summer

Distribution of silicic acid (Si(OH)₄) in bottom water was investigated in the central Seto Inland Sea under stratified conditions in summer. Water samples were collected at 10 stations on April 24 and 25 and July 7 and 8, 2012. In July, stratification progressed, and a cold water mass (dome) of <20 °C appeared. In response to the cold dome, low oxygen content was observed in the bottom layer of the eastern part of Hiuchi-Nada. In this water mass site, apparent oxygen utilization values calculated from dissolved oxygen (DO) concentrations increased, coinciding with increase of Si(OH)₄ concentrations from April to July. This suggests that increase of Si(OH)₄ [dissolution of biogenic silica (diatom frustules)] was accompanied by DO consumption due to degradation of organic matter such as plankton soft tissue. These findings suggest that a bacterial degradation of the organic matrix that covers diatom frustules could accelerate the dissolution of biogenic silica in bottom water under stratified conditions.