A bio-optical inversion model to retrieve absorption contributions and phytoplankton size structure from total minus water spectral absorption using genetic algorithm

We propose a bio-optical inversion model that retrieves the absorption contributions of phytoplankton and colored detrital matter(CDM),as well as the phytoplankton size classes(PSCs),from total minus water absorption spectra.The model is based on three-component separation of phytoplankton size structure and a genetic algorithm.The model performance was tested on two independent datasets(the NASA bio-Optical Marine Algorithm Dataset(NOMAD) and the northern South China Sea(NSCS) dataset).The relationships between the estimated and measured values were strongly linear,especially for aCDM(412),and the Root Mean Square Error(RMSE) of the CDM exponential slope(SCDM) was relatively low.Next,the inversion model was directly applied to in-situ total minus water absorption spectra determined by an underwater meter during a cruise in September 2008,to retrieve the phytoplankton size structure in the seawater.By comparing the measured and retrieved chlorophyll a concentrations,we demonstrated that total and size-specific chlorophyll a concentrations could be retrieved by the model with relatively high accuracy.Finally,we applied the bio-optical inversion model to investigate changes in phytoplankton size structure induced by an anti-cyclonic eddy in the NSCS.     

Impacts of internal waves on chlorophyll a distribution in the northern portion of the South China Sea

Internal waves can bring nutrients to the upper level of water bodies and facilitate phytoplankton photosynthesis. Internal waves occur frequently in the northern portion of the South China Sea and inflict an important effect on chlorophyll a distribution. In this study, in-situ observation and satellite remote sensing data were used to study the effects of internal waves on chlorophyll a distribution. Based on the in-situ observations, lower chlorophyll a concentrations were present in the middle and bottom level in areas in which internal waves occur frequently, while the surface chlorophyll a distribution increased irregularly, and a small area with relatively higher chlorophyll a concentrations was observed in the area around the Dongsha Island. Satellite remote sensing showed that the chlorophyll a concentration increased in the area near Dongsha Island, where internal waves frequently occurred. The results of the increased chlorophyll a concentration in the surface water near Dongsha Island in the northern portion of the South China Sea indicated that internal waves could uplift phytoplankton and facilitate phytoplankton growth.     

Size-fractionated Chlorophyll <Emphasis Type="Italic">a</Emphasis> biomass in the northern South China Sea in summer 2014

Spatial distribution of phaeopigment and size-fractionated chlorophyll a (Chl a) concentrations were examined in relation to hydrographic conditions in the northern South China Sea (NSCS) during a survey from 20 August to 12 September, 2014. The total Chl a concentration varied from 0.006 to 1.488 µg/L with a mean value of 0.259±0.247 (mean±standard deviation) µg/L. Chl a concentration was generally higher in shallow water (<200 m) than in deep water (>200 m), with mean values of 0.364±0.311 µg/L and 0.206±0.192 µg/L respectively. Vertically, the maximum total Chl a concentration appeared at depths of 30–50 m and gradually decreased below 100 m. The size-fractionated Chl a concentrations of grid stations and time-series stations (SEATS and J4) were determined, with values of pico- (0.7–2 µm), nano- (2–20 µm) and micro-plankton (20–200 µm) ranging from 0.001–0.287 (0.093±0.071 µg/L), 0.004–1.149 (0.148±0.192 µg/L) and 0.001–0.208 (0.023±0.036 µg/L), respectively. Phaeopigment concentrations were determined at specific depths at ten stations, except for at station A9, and varied from 0.007 to 0.572 (0.127±0.164) µg/L. Nano-and pico-plankton were the major contributors to total phytoplankton biomass, accounting for 50.99%±15.01% and 39.30%±15.41%, respectively, whereas microplankton only accounted for 9.39%±8.66%. The results indicate that the contributions of microplankton to total Chl a biomass were less important than picoplankton or nanoplankton in the surveyed NSCS. Different sized-Chl a had similar spatial patterns, with peak values all observed in subsurface waters (30–50 m). The summer monsoon, Kuroshio waters, Zhujiang (Pearl) River plume, and hydrological conditions are speculated to be the factors controlling the abundance and spatial heterogeneity of Chl a biomass in the NSCS.     

Response of phytoplankton community structure and size-fractionated Chlorophyll <Emphasis Type="Italic">a</Emphasis> in an upwelling simulation experiment in the western South China Sea

The South China Sea (SCS), which is the largest marginal sea in the western tropical Pacific, plays an important role in regional climate change. However, the research on the phytoplankton community structure (PCS) response to the upwelling remains inadequate. In January 2014, the upwelling simulation experiment was performed in the western SCS. Results indicate that the nutrient-rich bottom water not only increased the total Chlorophyll a (Chl a) concentrations, but would potentially altered the PCS. Due to new nutrients added, microphytoplankton had more sensitivity response to nutrient uptake than other phytoplankton groups. The variation of nutrients induced by formation, weakening and disappearance of upwelling resulted in phytoplankton species succession from cyanophyta to bacillariophyta. It may be the leading factor of the changes in PCS and size-fractionated Chl a. The initial concentration of DIP less than 0.1 μmolL^?1 could not sustain the phytoplankton growth. This indicates that phosphorus may be the limiting factor in the western SCS.     

Simulation of phytoplankton biomass in Quanzhou Bay using a back propagation network model and sensitivity analysis for environmental variables

Prediction and sensitivity models,to elucidate the response of phytoplankton biomass to environmental factors in Quanzhou Bay,Fujian,China,were developed using a back propagation(BP) network.The environmental indicators of coastal phytoplankton biomass were determined and monitoring data for the bay from 2008 was used to train,test and build a three-layer BP artificial neural network with multi-input and single-output.Ten water quality parameters were used to forecast phytoplankton biomass(measured as chlorophyll-a concentration).Correlation coefficient between biomass values predicted by the model and those observed was 0.964,whilst the average relative error of the network was-3.46% and average absolute error was 10.53%.The model thus has high level of accuracy and is suitable for analysis of the influence of aquatic environmental factors on phytoplankton biomass.A global sensitivity analysis was performed to determine the influence of different environmental indicators on phytoplankton biomass.Indicators were classified according to the sensitivity of response and its risk degree.The results indicate that the parameters most relevant to phytoplankton biomass are estuary-related and include pH,sea surface temperature,sea surface salinity,chemical oxygen demand and ammonium.     

Distribution patterns of chlorophyll <Emphasis Type="Italic">a</Emphasis> in spring and autumn in association with hydrological features in the southern Yellow Sea and northern East China Sea

Two field studies were conducted to measure pigments in the Southern Yellow Sea (SYS) and the northern East China Sea (NECS) in April (spring) and September (autumn) to evaluate the distribution pattern of phytoplankton stock (Chl a concentration) and the impact of hydrological features such as water mass, mixing and tidal front on these patterns. The results indicated that the Chl a concentration was 2.43±2.64 (Mean ± SD) mg m^?3 in April (range, 0.35 to 17.02 mg m^?3) and 1.75±3.10 mg m^?3 in September (from 0.07 to 36.54 mg m^?3) in 2003. Additionally, four areas with higher Chl a concentrations were observed in the surface water in April, while two were observed in September, and these areas were located within or near the point at which different water masses converged (temperature front area). The distribution pattern of Chl a was generally consistent between onshore and offshore stations at different depths in April and September. Specifically, higher Chl a concentrations were observed along the coastal line in September, which consisted of a mixing area and a tidal front area, although the distributional pattern of Chl a concentrations varied along transects in April. The maximum Chl a concentration at each station was observed in the surface and subsurface layer (0–10 m) for onshore stations and the thermocline layer (10–30 m) for offshore stations in September, while the greatest concentrations were generally observed in surface and subsurface water (0–10 m) in April. The formation of the Chl a distributional pattern in the SYS and NECS and its relationship with possible influencing factors is also discussed. Although physical forces had a close relationship with Chl a distribution, more data are required to clearly and comprehensively elucidate the spatial pattern dynamics of Chl a in the SYS and NECS.     

Spike in phytoplankton biomass in Greenland Sea during 2009 and the correlations among chlorophyll-a,aerosol optical depth and ice cover

The distributions and correlations of chlorophyll-a(Chl-a),aerosol optical depth(AOD)and ice cover in the southeast Arctic Ocean-Greenland Sea(10°W–10°E,70°–80°N)between 2003 and 2009 were studied using satellite data and statistical analyses.Regression analysis showed correlations between Chl-a and AOD,Chl-a and ice cover,and AOD and ice cover with different time lags.The time lag of Chl-a and AOD indicated their long-term equilibrium relationship.Peaks in AOD and Chl-a and generally occurred in May and July,respectively.Despite the time lag,the correlation between Chl-a and AOD in the study region was as high as 0.7.The peak gap between Chl-a and AOD shifted for about 6 weeks during 2003–2009.In the summer and autumn of 2009,Chl-a and AOD levels were much higher than during the other years,especially in the northern band of the study region(75°–80°N).The driving forces for this localized increase in phytoplankton biomass could be mainly attributed to the very high rate of ice melting in spring and early summer and the high wind speed in autumn,together with the increased deposition of aerosol throughout the year.The unusually high AOD in the spring of 2003 was mainly due to a massive fi re in Russia,which occurred in the fi rst half of the year.Over the 7 years of the study,the sea surface temperature generally decreased.This may have been due to the release of dimethylsulfi de into the air,excreted in large amounts from abundant phytoplankton biomass,and its subsequent reaction,form large amounts of aerosol,and resulting in regional cooling.     

Retrieval of inherent optical properties of the Yellow Sea and East China Sea using a quasi-analytical algorithm

We tested and modified the quasi-analytical algorithm (QAA) using 57 groups of field data collected in the spring of 2003 in the Yellow Sea and East China Sea. The QAA performs well in deriving total absorption coefficients of typical coastal waters. The average percentage difference (APD) is in a range of 13.9%–38.5% for the total absorption coefficient (13.9% at 440 nm), and differences in particle backscattering coefficient bbp(λ) are less than 50% (in the case of the updated QAA). To obtain improved res...     

Variation in downwelling diffuse attenuation coefficient in the northern South China Sea

The diffuse attenuation coefficient for downwelling irradiance （Kd（λ）） is an important parameter for ocean studies. Based on the optical profile data measured during three cruises in the northern South China Sea in autumn from 2003 to 2005, variations in the Kd（λ） spectra were analyzed. The variability of Kd（λ） shows much distinct features in both magnitude and spectra pattern, it is much higher in coastal waters than that of open oceanic waters; and the blue-to-green （443/555） ratio of Kd（λ） tends to increase with chlorophyll a concentration （[Chl-a]） from open ocean to coastal waters. These characteristics can be explained most by the increase of aw＋p（443）/aw＋p（555） with [Chl-a]. In short waveband, the relation between Kd（λ）-Kw（λ） and [Chl-a] can be well described by a power law function, indicating the large contribution of phytoplankton to the variations in Kd（λ）. As for the spectral model of the diffuse attenuation coefficient, there are good linear relationships between Kd（490） and Kd（λ） in other wavelengths with own slope and intercept of a linear functions in the spectral range 412-555 nm. Kd（490） is well correlated with the spectral ratio of remote sensing reflectance; and should enough measurement data are given, this empirical algorithm would be used in the Kd（λ） retrieval from ocean color satellite data. The variation in Kd（λ） provides much useful information for us to study the bio-optical property in the northern South China Sea.     

Estimation of potential distribution of gas hydrate in the northern South China Sea

Gas hydrate research has significant importance for securing world energy resources, and has the potential to produce considerable economic benefits. Previous studies have shown that the South China Sea is an area that harbors gas hydrates. However, there is a lack of systematic investigations and understanding on the distribution of gas hydrate throughout the region. In this paper, we applied mineral resource quantitative assessment techniques to forecast and estimate the potential distribution of gas hydrate resources in the northern South China Sea. However, current hydrate samples from the South China Sea are too few to produce models of occurrences. Thus, according to similarity and contrast principles of mineral outputs, we can use a similar hydrate-mining environment with sufficient gas hydrate data as a testing ground for modeling northern South China Sea gas hydrate conditions. We selected the Gulf of Mexico, which has extensively studied gas hydrates, to develop predictive models of gas hydrate distributions, and to test errors in the model. Then, we compared the existing northern South China Sea hydrate-mining data with the Gulf of Mexico characteristics, and collated the relevant data into the model. Subsequently, we applied the model to the northern South China Sea to obtain the potential gas hydrate distribution of the area, and to identify significant exploration targets. Finally, we evaluated the reliability of the predicted results. The south seabed area of Taiwan Bank is recommended as a priority exploration target. The Zhujiang Mouth, Southeast Hainan, and Southwest Taiwan Basins, including the South Bijia Basin, also are recommended as exploration target areas. In addition, the method in this paper can provide a useful predictive approach for gas hydrate resource assessment, which gives a scientific basis for construction and implementation of long-term planning for gas hydrate exploration and general exploitation of the seabed of China.     

The impact of atmospheric deposition of cadmium on dominant algal species in the East China Sea

Cadmium(Cd) mainly derived from anthropogenic emissions can be transported through atmospheric pathway to marine ecosystem,affecting the phytoplankton community and primary productivity.In this study,we identified the toxicity threshold of Cd for phytoplankton under seawater conditions of the coastal East China Sea(ECS) through both laboratory and in situ mesocosm incubation experiments.The mesocosm experiment showed that Cd in low concentration(0.003 μg per μg chl a) was conducive to the growth of natural community and increased chl a productivity.In high concentration(0.03 μg per μg chl a) Cd acted as an inhibiting factor which decreased the total chl a productivity.The diatom community was found to be more sensitive to Cd toxicity than dinoflagellate,as the low concentration Cd showed toxicity to diatom but enhanced dinoflagellate growth.We noticed that the soluble Cd estimated from atmosphere deposition to the coastal ECS was below the toxicity threshold and the Cd deposition might promote phytoplankton growth in this region.In our laboratory experiments,adding Cd,similar to aerosol deposition,stimulated the growth of both dominant algal species Prorocentrum donghaiense Lu(dinoflagellate) and Skeletonema costatum(diatom).Adding Cd on a higher level inhibited the growth of both the species,but Skeletonema costatum seemed obviously more sensitive to toxicity.This indicates the potential impact of atmospheric deposition Cd on phytoplankton community succession in the ECS.     

南海北部花斑蛇鲻生长死亡参数估计及开捕规格

将南海北部花斑蛇鲻分成南海北部大陆架和北部湾两个不同海域群体 ,计算花斑蛇鲻的生长与死亡参数。得到的VonBertalanffy生长方程的相关参数为 :南海北部大陆架L∞ =4 5.5cm ,K =0 .2 8,t0 =- 0 .4 6 0 ;北部湾L∞ =4 0 .0cm ,K =0 .30 ,t0 =- 0 .4 43。计算自然死亡系数得南海北部大陆架为 0 .6 3;北部湾为 0 .6 7;捕捞死亡系数南海北部大陆架为 0 .79,北部湾为 1.11。据等渔获量曲线建议南海北部大陆架花斑蛇鲻开捕体长由 13.3cm增加至 2 0 .0cm ,同时 ,捕捞死亡系数可由当前的 0 .79放宽至 1.0 ;北部湾花斑蛇鲻开捕体长由 13.5cm增加至 19.0cm的同时 ,捕捞死亡系数可由当前的 1.11放宽至 1.5。     

Modeling seasonal variations of subsurface chlorophyll maximum in South China Sea

In the South China Sea(SCS), the subsurface chlorophyll maximum(SCM) is frequently observed while the mechanisms of SCM occurrence have not been well understood. In this study, a 1-D physical-biochemical coupled model was used to study the seasonal variations of vertical profiles of chlorophyll-a(Chl-a) in the SCS. Three parameters(i.e., SCM layer(SCML) depth, thickness, and intensity) were defined to characterize the vertical distribution of Chl-a in SCML and were obtained by fitting the vertical profile of Chl-a in the subsurface layer using a Gaussian function. The seasonal variations of SCMs are reproduced reasonably well compared to the observations. The annual averages of SCML depth, thickness, and intensity are 75 ± 10 m, 31 ± 6.7 m, and 0.37 ± 0.11 mg m-3, respectively. A thick, close to surface SCML together with a higher intensity occurs during the northeastern monsoon. Both the SCML thickness and intensity are sensitive to the changes of surface wind speed in winter and summer, but the surface wind speed exerts a minor influence on the SCML depth; for example, double strengthening of the southwestern monsoon in summer can lead to the thickening of SCML by 46%, the intensity decreasing by 30%, and the shoaling by 6%. This is because part of nutrients are pumped from the upper nutricline to the surface mixed layer by strong vertical mixing. Increasing initial nutrient concentrations by two times will increase the intensity of SCML by over 80% in winter and spring. The sensitivity analysis indicates that light attenuation is critical to the three parameters of SCM. Decreasing background light attenuation by 20% extends the euphotic zone, makes SCML deeper(~20%) and thicker(12% – 41%), and increases the intensity by over 16%. Overall, the depth of SCML is mainly controlled by light attenuation, and the SCML thickness and intensity are closely associated with wind and initial nitrate concentration in the SCS.     

Sediment compaction and pore pressure prediction in deepwater basin of the South China Sea: Estimation from ODP and IODP drilling well data

Overpressure in deepwater basins not only causes serious soft sediment deformation, but also significantly affects the safety of drilling operations. Therefore, prediction of overpressure in sediments has become an important task in deepwater oil exploration and development. In this study, we analyze the drilling data from ODP Leg 184 Sites 1144, 1146, and 1148, and IODP Leg 349 Sites U1431, U1432, U1433, and U1435 to study the sediment compaction and controls in the northern South China Sea. Sedimentation rate, sediment content, distribution area, and buried depth are the factors that influence sediment compaction in the deepwater basin of the South China Sea. Among these factors, the sediment content is the most important. The fitted normal compacted coefficients and mudline porosity for an interval of 50 m shows disciplinary variation versus depth. The pore pressure predicted from different fitted results shows varying overpressure situations. The normal compaction trend from Site 1144 reflects the porosity variation trend in stable deposition basins in the northern South China Sea. The predicted pore pressure shows overpressure at Site 1144, which is attributed to compaction disequilibrium. Nevertheless, the mixed lithology column may influence the predicted over-pressure at Site 1148, which is responsible for the confusing result. Above all, we find that sediment compaction should serve as a proxy for pore pressure in the deepwater basin of the South China Sea.     

Phytoplankton pigment patterns and community composition in the northern South China Sea during winter

Phytoplankton pigment patterns and community composition were investigated in the northern South China Sea using high-performance liquid chromatography and the CHEMTAX software from February 11 to 23, 2009. We recognized four different vertical distribution patterns of pigments: chlorophyll a (Chl a)-like type, divinyl chlorophyll a (DV Chl a) type, even distribution type, and surface type. The average value of ratios of accessory photo-protective pigments (APP) to accessory photo-synthetic pigments was 0.89±0.63 in the upper 50 m and 0.16±0.06 below 50 m depth. With increasing depth, APP decreased and photo-synthetically active radiation was attenuated. There was an obvious succession in the phytoplankton community from inshore to the open sea. Diatoms were dominant in the inshore region, while pelagophytes, Prochlorococcus, cyanobacteria and prymnesiophytes were dominant in the open sea. The vertical distribution of phytoplankton also differed greatly from inshore to the open sea. In the coastal and shelf region, diatoms were important components in the whole water column. Cyanobacteria also had a high abundance at the Subsurface Chlorophyll a Maxima (SCM) in the shelf region. In the slope and open sea, Prochlorococcus and cyanobacteria were important groups above the SCM, while pelagophytes dominated below the SCM.     

On the winter circulation of the northern South China Sea and its relation to the large scale oceanic current

The nonwind-driven mechanism of the winter circulation in the northern South China Sea is discussed. Linked by the Bashi Strait to the Pacific Ocean, the northern South Cnina Sea is treated as a part of the Pacific western boundary where the circulation variation (except the very thin surface layer) is closely related to that of the ocean interior and the effect of local wind might be neglected (at least for some seasons). Based on the assumption that the thick and strong westward current which flows in through the Bashi Strait can effectively prevent water exchange between the northern and southern South China Seas, the model sea only includes the northern part. Barotropic numerical experiments show that part of this westward current is deflected by the continental slope and forms the slope area NE current—the South China Sea Warm Current. Besides, the topographical flow fed by the extension of the western boundary current and the anticyclonic eddy born near the eastern boundary are also fundamental components of the South China Sea Warm Current. The reflection of the incident Rossby waves by the continental slope is found to be of significance in the intensification of the South China Sea Warm Current. Contribution No. 1362 from Institute of Oceanology, Academia     

Short- and long-term response of phytoplankton to ENSO in Prydz Bay,Antarctica: Evidences from field measurements,remote sensing data and stratigraphic biomarker records

The study provides one of the first lines of evidence showing linkages between Antarctic phytoplankton abundance and composition in response to ENSO, based on historical reconstruction of sediment biomarkers. In addition to sediment biomarkers, field measured and remote sensing data of phytoplankton abundance were also recorded from Prydz Bay, Eastern Antarctica. Com-munity structure of field measured phytoplankton showed significant El Ni？o/La Ni？a-related succession during 1990 to 2002. In general, the number of algae species decreased during El Ni？o and La Ni？a years compared to normal years. Austral summer monthly variation of remotely sensed chlorophyll-a （Chl-a）, particulate organic carbon （POC）, and sea surface temperature （SST） indicated that ENSO impacted the timing of phytoplankton blooms during 2007 to 2011. Phytoplankton blooms （indicated by Chl-a and POC） preceded the increases in SST during El Ni？o years, and lagged behind the SST increases during La Ni？a years. Stratigraphic record of marine sedimentary lipid （brassicasterol, dinosterol and alkenones） biomarkers inferred that the proportions of different algae （diatoms, dinoflagellates and haptophytes） changed significantly between El Ni？o and La Ni？a events. The relative proportion of diatoms increased, with that of dinoflagellates being decreased during El Ni？o years, while it was reversed during La Ni？a years.     

Distribution and migration of the common squidTodarodes pacificus in the Yellow Sea

Study of the distribution and migration of the common squid,Todarodes pacificus Steenstrup,basedon the index of important fishing ground(P) and fisheries statistics on the Yellow Sea and northern EastChina Sea during 1980—1991 showed that:1.Its catch in the fishing period(June to November) is 91.77% of the annual yield.The fishingground distributes over the northem and middle Yel1ow Sea and adjacent area of the Changjiang Estuary.2. It over-winters in the northem East China Sea and waters adjacent to Goto Island from De-cember to February and spawns in waters near Haijiao Is1and and west of Kyushu. The main stock mi-grates along 123°30′E to the ChangJiang Estuary, Haizhou Bay. offsea from Shidao to Qingdao,mideastern Yellow Sea, and offsea Weihai and Haiyang Island succesively for feeding after April. The sur-plus stock migrates again to the wintering ground in December.3.The favorable feeding temperature is 6-23℃(optimum of l3-20℃ in the Changjiang Estua-ry and 7-13℃ in the northern and middle Yel     

南海北部近海柱状沉积物多环芳烃组成及来源分析

【目的】研究南海北部近海区域柱状沉积物多环芳烃组成及分布特征,讨论全新世早期火历史及气候变化。【方法】利用AMS ¹⁴C定年技术结合有机地球化学分析手段对全新世早期南海北部近海沉积物柱状样品中多环芳烃(PAHs)分布特征进行研究。【结果】南海北部近海沉积物中16种PAHs总浓度范围为8.58~17.48 ng/g,在约10000 a B.P.的全新世早期呈现先增大后减小波动变化,与TOC变化基本同步。【结论】沉积物中多环芳烃主要来源于南海北部近海陆源区域自然火灾产生的焦炭残渣。PAHs的沉积浓度变化间接指示了全新世早期东亚季风的强度变化。     

A model study on dynamical processes of phytoplankton in Laizhou Bay

A three-dimensional ecosystem model, using a PIC (Particle-In-Cell) method, is developed to reproduce the annual cycle and seasonal variation of nutrients and phytoplankton biomass in Laizhou Bay. Eight state variables, i.e., DIN (dissolved inorganic nitrogen), phosphate, DON (dissolved organic nitrogen), DOP (dissolved organic phosphorus), COD (chemical oxygen demand), chlorophyll-a (Chl-a), detritus and the zooplankton biomass, are included in the model. The model successfully reproduces the observed temporal and spatial variations of nutrients and Chl-a biomass distributions in the bay. The nutrient concentrations are at high level in winter and at low level in summer. Double-peak structure of the phytoplankton (PPT) biomass exists in Laizhou Bay, corresponding to a spring and an autumn bloom respectively. Several numerical experiments are carried out to examine the nutrient limitation, and the importance of the discharges of the Yellow River and Xiaoqinghe River. Both DIN limitation and phosphate limitation exist in some areas of the bay, with the former being more significant than the latter. The Yellow River and Xiaoqinghe River are the main pollution sources of nutrients in Laizhou Bay. During the flood season, the algal growth is inhibited in the bay with the Yellow River discharges being excluded in the experiment, while in spring, the algal growth is enhanced with the Xiaoqinghe River excluded.