A Kinetic Spectrophotometric Method for the Determination of Iron （Ⅲ） in Water Samples

A new kinetic spectrophotometric method has been developed for the determination of iron (Ⅲ). The method is based on the catalytic effect of iron (Ⅲ) on the oxidation of weak acid brilliant blue dye (RAWL) by KIO4 in acid medium. The advantages of the proposed method are that it is sensitive, accurate, rapid, inexpensive, can be operated under room temperature and has a large determination concentration range compared to other techniques. The obtained optimum conditions are pH 3.15, RAWL (200 mgL-1) 5.00mL, Potassium periodate solution (0.01 molL-1) 0.30mL, phenanthroline (0.02molL-1) 1.00mL, reaction temperature 25℃ and reaction time 7 miu. With this method iron could quantitively be determined in the range 0.00-0.02 mgL-1, the detection limit being 4.10×10-10mL-1. The relative standard deviations (RSD) in five replicate determinations for 3 μgL-1 and 5μgL-1 iron (Ⅲ) are 3.1% and 1.9%, respectively. The method has been applied to the determination of iron (Ⅲ) in tap water samples and seawater samples (from the South China Sea), the recovery rates being 98.0% and 100.5%, respectively.     

Measurement of Trace Manganese(Ⅱ) by the Catalytic Kinetic Spectrophotometric Method

A new kinetic spectrophotometric method is developed for the measurement of manganese (Ⅱ) in water. The method is based on the catalytic effect of manganese (Ⅱ) with the oxidation of weak acid brilliant blue dye (RAWL) by KIO4 using the Nitrilo triacetic acid (NTA) as an activation reagent. The optimum conditions obtained are 40mgL-1 RAWL, 1×10-4molL-1 KIO4, 2×10-4molL-1 Nitrilo triacetic acid (NTA), pH = 5.8, the reaction time of 3.00 min and the temperature of 20.0 ℃. Under the optimum con-ditions, the proposed method allows the measurement of manganese (Ⅱ) in a range of 0-50.0ngmL-1 and with a detection limit of down to 0.158 ng mL-1. The recovery efficiency in measuring the standard manganese (Ⅱ) solution is in a range of 98.5%-102%, and the RSD is in a range of 0.76%-1.25%. The new method has been successfully applied to the measurement of manganese (Ⅱ) in both fresh water and seawater samples with satisfying results. Moreover, few cations and anions interfere with the measurement of man-ganese (Ⅱ). Compared with other kinetic catalytic methods and instrumental methods, the proposed method shows fairly good selec-tivity and sensitivity, low cost, cheapness, low detection limit and rapidity. It can be applied on boats easily.     

Study on the Determination of Trace Ni（Ⅱ） by the Catalytic Kinetic Spectrophotometric Method

A new kinetic spectrophotometric method has been developed for the determination of trace Ni (II) in natural water.The method is based on the catalytic effect of Ni (II) on the oxidation of weak acid brilliant blue dye (RAWL) by KIO4 in acid medium.The concentration of nickel (II) can be determined spectrophotometrically by measuring the decrease of absorbance of RAWL at λ= 626 nm using the fix-time method.The influencing factors are investigated by the orthogonal experimental design.The obtained optimum analytical conditions are:pH=2.00,c RAWL=5.00×10-5 mol L-1,cKIO 4= 2.00×10-5 mol L-1,the reaction time t=10 min and the temperature T=25℃..Under the optimum conditions,the developed method allows the measurement of Ni (II) in a range of 0-40.0 ng mL-1.The standard deviation of eleven independent measurements of blank reaction is S=3.08×10-3 and the limit of detection is 2.20 ng mL-1.The relative standard deviations (RSDs) in six replicate determinations of 5 ng mL-1 and 8 ng mL-1 Ni (II) are 2.87% and 1.11%,respectively.Moreover,the experiments show few cations and anions can interfere with the measurement of Ni (II).The recovery efficiencies of this method are in a range of 97.0%-102.5% in freshwater samples.But there is a decreasing effect,which is about 0.2 times the added Ni (II) in seawater medium.After reasonable calibration this processing method is used for the determination of Ni (II) in seawater samples successfully.The results show this developed method has high accuracy and precision,high sensitivity,large range of linearity and high speed.The method can,therefore,be employed at room temperature.     

Determination of trace vanadium (V) in seawater and fresh water by the catalytic kinetic spectrophotometric method

A new kinetic spectrophotometric method has been developed for the determination of vanadium (V). The method is based on the catalytic effect of vanadium (V) on the oxidation of weak acid brilliant blue dye (RAWL) by KBrO₃ using the citric acid as activation reagent. The obtained optimum conditions are: c (RAWL) = 1×10⁻⁴ molL⁻¹, c (KBrO₃) = 3×10⁻² molL⁻¹, c (citric acid) = 9×10⁻³ molL⁻¹, pH = 2.50, the reaction time being 7.0 min and the temperature being 25.0°C. Under the optimum conditions, the proposed method allows the determination of vanadium (V) in the range of 0–70.0 ng mL⁻¹ and the detection limit is down to 0.407 ng mL⁻¹. For standard vanadium (V) solution determination, the recovery efficiency is in the range of 98.5%–102% and the RSD ranges from 0.76%–1.25%. Moreover, it is demonstrated that most cations and anions do not interfere with the determination of vanadium (V) under the analytical condition. The new method was successfully applied in the determination of vanadium (V) in fresh water and seawater samples with satisfactory results. Vanadium (V) in the seawater samples from Qingdao offshore was determined using the method and the distribution of vanadium (V) was mapped. Compared with other instrumental analytical methods, the proposed method shows good selectivity, sensitivity, simplicity, lower cost and rapidity. It can be employed on shipboard easily.     

Determination of Trace Copper （Ⅱ） in Water Samples by Kinetic-spectrophotometry

A new kinetic-spectrophotometric method is proposed for the determination of copper （ Ⅱ ）. The method is based on the catalytic effect of copper （ Ⅱ ） on the oxidation of weak acid brilliant blue dye （RAWL） by hydrogen peroxide. The copper （ Ⅱ ） can be determined spectrophotometrically by measuring the decrease of absorbance of RAWL at λ = 626 nm using the fix-time method. The optimum reaction conditions are as follows： pH 7.20, buffer solution NaOH-KH2PO4, RAWL （200 mgL-1） 5.00 mL, H2O2 （30%） 0.50 mL, reaction temperature 80 ？？ and reaction time 20 min. The linear range of this method is between 0 μg L^-1 and 12 μg L^-1 and the limit of detection is 0.011 μg L-1, the relative standard deviation （RSD） in five replicate determinations for 2 and 8 μg L-1 copper （ Ⅱ ） are 3.2% and 2.3%, respectively. Twenty ions do not interfere in the determination of copper （ Ⅱ ）. The method has been applied satisfactorily to the determination of copper （ Ⅱ ） in freshwater samples （tap water and Yellow River water from Lijin, Shandong, China） and seawater samples （from the South China Sea）, the recovery rates are 98.0%, 102.5% and 96.0%, respectively.     

The inhibitory degree between Skeletonema costatum and dinoflagllate Prorocentrum donghaiense at different concentrations of phosphate and nitrate/phosphate ratios

Interactions between Skeletonema costatum (S. costatum) and Prorocentrum donghaiense (P. donghaiiense) were inves-tigated using bi-algal cultures at different concentrations of phosphate (PO4-P) and nitrate/phosphate (N/P) ratios. Experiments were conducted under P-limited conditions and the Lotka-Volterra mathematical model was used to simulate the growth of S. costatum and P. donghaiense in the bi-algal cultures. Both of these two species were inhibited significantly in bi-algal culture. The results of the simulation showed that the inhibitory degree of S. costaum by P. donghaiense was high when the concentration of PO4-P was low (0.1μmolL-1/2 d), but that of P. donghaiense by S. costaum was high with increased PO4-P supply (0.6μmolL-1/2 d). At low concen-tration of PO4-P (0.1μmolL-1/2 d), or high concentration of PO4-P (0.6μmolL-1/2 d) with high N/P ratio (160), the interactions be-tween S. costatum and P. donghaiense were dependent on the initial cell densities of both species. At high concentration of PO4-P (0.6μmolL-1/2 d) with low N/P ratio (25 or 80), S. costatum exhibited a survival strategy superior to that of P. donghaiense. The de-gree of inhibition of P. donghaiense by S. costaum increased with elevated N/P ratio when the medium was supplemented with con-centration 0.1μmolL-1/2 d of PO4-P. The degree of inhibition to P. donghaiense by S. costaum increased with elevated N/P ratio at low concentration of PO4-P (0.1 μmolL-1/2 d). This trend was conversed at high concentration of PO4-P (0.6μmolL-1/2 d). However, the degree of inhibition of S. costaum by P. donghaiense increased with the increased N/P ratio at different PO4-P concentrations (0.1μmolL-1/2 d and 0.6μmolL-1/2 d). These results suggested that both phosphate concentration and N/P ratio affected the competition between S. costaum and P. donghaiense: P. donghaiense is more competitive in environments with low phosphate or high N/P ratio and the influence of N/P ratio on the competition was more significant with lower phosphate concentration.     

Study on the Tripolyphosphatase （TPPase） Property of Bighead Carp （Aristichthys nobilis） Myosin Subfragment-1

Myosin subfragment-1 was prepared from the myofibrils of bighead carp (Aristichthys nobilis). The myosin subfrag- ment-1 was proved to have the activity of tripolyphosphatase (TPPase) responding to the hydrolysis of sodium tripolyphosphate (STPP). The optimum temperature and pH for the TPPase of myosin subfragment-1 were 30℃ and pH 5.0, and at pH 8.0 the TPPase also showed a high activity. Mg2 was necessary to TPPase. The TPPase activity of myosin subfragment-1 was activated by Mg2 under low concentrations, but was inhibited when the concentration was over 17 mmolL-1. The TPPase activity was also affected by KCl. The optimum concentration of KCl for TPPase was 0.3 molL-1 under the condition of 17 mmolL-1 Mg2 . The TPPase activity was significantly inhibited by EDTA-Na2. Reagents such as KBr, KI and KIO3 could inhibit the TPPase effectively. K2Cr2O7 as well as KMnO7 and KNO3 exhibited weak inhibiting effects. The TPPase converted STPP to pyrophosphate (PP) and orthophosphate (Pi) stoichiometrically with a KM of 3.2 mmolL-1.     

Dietary manganese requirement ofP. Vannamei

Graded levels of manganese were supplemented to a semi-purified diet containing 45% crude protein, to provide six levels of manganese (i. e. containing 5, 25, 50, 70, 140 and 210×10⁻⁶, respectively) for two experiments with these experimental diets. The initial weight of shrimp used in the 35–day experiment I was 0.30±0.04 g, and that in the 70–day Experiment II was more than one gram. The results showed that optimum content in the semi-purified diet for the more than 1 gram shrimp ranged from 70 ×10⁻⁶, to 140×10⁻⁶, but supplementation of Mn was not necessary for the small shrimp. Contribution No. 2673 from the Institute of Oceanology, Chinese Academy of Sciences.     

Cryopreservation of Gametophytes of Laminaria japonica （Phaeophyta） Using Encapsulation-Dehydration with Two-Step Cooling Method

Gametophytes of Laminaria japonica were cryopreserved in liquid nitrogen using encapsulation-dehydration with two-step cooling method. Gametophytes cultured at 10℃ and under continuous irradiance of 30 μmol m-2 s-1 for 3 weeks were encapsulated in calcium alginate beads. The beads were dehydrated in 0.4 molL-1 sucrose prepared with seawater for 6 h, desiccated in an incubator set at 10℃ and 70% relative humidity for 4 h, pre-frozen at either -40℃ or -60℃ for 30 min, and stored in liquid nitrogen for ＞24 h. As high as 43% of survival rate was observed when gametophytes were thawed by placing the beads in 40℃seawater and re-hydrated in 0.05 molL-1 citrate sodium prepared using 30‰ NaC1 7 d later. More cells of male gametophytes survived the whole procedure in comparison with female gametophytes. The cells of gametophytes surviving the preservation were able to grow asexually and produce morphologically normal sporophytes.     

Determination of Selenium in Marine Aquatic Products by Hydride Generation-atomic Fluorescence Spectrometry （HG-AFS）

A method for the analysis of selenium in marine aquatic products by HG-AFS has been investigated. The method is based on the reduction of inorganic selenium to volatile SeH2 which is bubbled out by carrier gas of pure argon, and then swept to Ar-H2 flame quarts atomizer to measure its fluorescence intensity. The hydride generation, transportation, atomization and some instrumental parameters were studied by a kind of orthogonal design. The optimum conditions selected are as follows： reactive acidity, 20% HC1; the amount of NaBH4, 4.9mL; gas flow of argon, 600mLmin^-1; atomizing temperature, 200 ℃ ; negative high voltage, - 300V; light current, 100 mA; integral time, 7s. The detection limit of the presented method is 0.072μgL^-1 for selenium. The calibration curve shows a satisfactory line inthe concentration range from 0.000 to 1.000μgL^-1 Se. The recovery is 95.8%-102.2%.     

Preliminary Study on the Responses of Three Marine Algae,Ulva pertusa （ Chlorophyta ） , Gelidium amansii （ Rhodophyta ）and Sargassum enerve （ Phaeophyta）, to Nitrogen Source and Its Availability

1　Introduction　Inrecentyears ,eutrophicationhasbecomeaworld wideenvironmentalprobleminthecoastalarea.Aqua culturebecomesaseriouspollutionsourcelikesewagedischarge .Wasteproductsfromfishfarmsconsistma inlyofnitrogen ,phosphorusandcarbondioxide .Inpen bas…     

DISCOVERY OF ORGANIC MOLECULES IN DEEP-SEA IRON COSMIC DUST

A great quartity of cosmic dust(spherules) was found in deep-sea sediments during May to July,1983manganese nodule investigations by the R/V“XIANGYANGHONG 16”in the area 7°-11°N,167°-178°Win the Pacific.Comprehensive study of the cosmic dust and determination with Laser Raman MolecularMicroprobe(LRMM) of the molecules in it showed that besides Fe-Fe,Fe~(3+)-O,Fe-Ni,Al-O,Fe-Obr-Si and Si-Onb,it also contained the organic molecules C-H-O and C-H-S-O,various no fixed form molecules of C,CH_2,CH_3 and volatile molecules CO_2,H_2O,OH~- and H_2S,etc…The study result has very important applications for exploring the origin of interplanetary dust parti-cles and life material.     

Impact of microzooplankton and Calanus sinicus (Brodsky, 1962) on phytoplankton in the Yellow Sea during early summer

Dilution incubations and Calanus sinicus addition incubations were simultaneously conducted at five stations in the Yellow Sea in June of 2004 to evaluate the impact of microzooplankton and Calanus sinicus on phytoplankton based on the Chlorophyll a (Chl-a) levels. The Chl-a growth rates (k) ranged from 0.60–1.67 d⁻¹, while microzooplankton grazed the Chl-a at rates (g) of 0.29–0.62 d^t-1. The addition of C. sinicus enhanced the Chl-a growth rate (Z) by 0.004–0.037 d⁻¹ ind.⁻¹ L. C. sinicus abundance ranged from 84.1–160.9 ind. m⁻³, which occupied 90.7%–99.1% of the copepod (>500 μm) population. The in-situ increase in phytoplankton by C. sinicus community was estimated to be 0.000 4–0.005 9 d⁻¹. These results showed that microzooplankton were the main grazers of phytoplankton, while C. sinicus induced a slight increase in the levels of phytoplankton.     

Cryopreservation of Veliger Larvae of Trumpet Shell, Charonia sauliae： an Essential Preparation to Artificial Propagation

Trumpet shell, Charonia sauliae, is an endangered and valuable species, but its artificial propagation protocol has not been successfully established. To estimate the possibility of cryopreservation for larvae of C. sauliae, which is a potential preparation for its artificial reproduction and further research, in this study a protocol for the cryopreservation of veliger larvae of trumpet shell was optimized. Through a two-step cryopreservation procedure, four kinds of cryoprotectants (ethylene glycol, 1, 2-propanediol, dimethyl sulfoxide and glycerol) were employed at three concentrations (1.0, 1.5 and 2.0 molL⁻¹) respectively and survival rates of larvae were determined after a storage of 1h. The larvae frozen with these four cryoprotectants after 1 h storage were cultured, and then survival rates were determined at 24, 72 and 120 h after thawing. Dimethyl sulfoxide at a concentration of 1.5 molL⁻¹ showed the best protective effect in all experiments (p<0.05). And survival rates of larvae frozen with dimethyl sulfoxide were determined after 1, 7 and 15 d of storage. The survival rates of larvae frozen with 1.5 molL⁻¹ dimethyl sulfoxide after 1 h, 1 d, 7 d and 15 d of storage were 80.77% ±7.51%, 80.34% ±11.28%, 83.10% ±9.14% and 77.23% ±6.22% respectively. No significant differences in survival rates of larvae frozen with dimethyl sulfoxide were observed after various storage periods (p>0.05).     

Studies on culture conditions of benthic diatoms for feeding abalone

Effects of salinity, pH, nitrogenous and phosphate nutrients on the growth rate of four species of benthic diatoms were studied by using the method of in situ optical density measurement. The optimal culture conditions for the four species of diatoms are as follows: forAmphora coffeaeformis, s 35; pH 8.5; NO₃ ⁻−N 1.54, NH₄ ⁺−N, 7.0; CO (NH₂)₂−N, 2.5 (mg/L); PO₄ ³⁻−P 1.13 (mg/L); forCocconeis scutellum varparva, s 30; pH 8.5; NO ₃ ⁻ −N 3.08, NH ₄ ⁺ −N 3.5, CO(NH₂)₂−N 5.0 (mg/L); pO ₄ ³⁻ −P 0.283 (mg/L); forNavicula corymbosa s 25; pH 8.0; NO ₃ ⁻ −N 1.54, NH ₄ ⁺ −N 3.5 CO(NH₂)₂−N 5.0 (mg/L); PO ₄ ³⁻ −P 0.565 (mg/L); forNavicula mollis. s 25; pH 8.0; NO ₃ ⁻ −N 1.54, NH ₄ ⁺ −N 1.75, CO(NH₂)₂−N 1.25 (mg/L); PO ₄ ³⁻ −P 0.141 (mg/L). Part of the results of this paper were exchanged in the Fourth Asian Aquaculture Forum. Oct. 16–20. 1995. Beijing, P. R. China.     

Total lipid and fatty acid composition of eight strains of marine diatoms

Fatty acid composition and total lipid content of 8 strains of marine diatoms (Nitzschia frustrula, Nitzschia closterium, Nitzschia incerta, Navicula pelliculosa, Phaeodactylum tricornutum, Synedra fragilaroides) were examined. The microalgae were grown under defined conditions and harvested at the late exponential phase. The major fatty acids in most strains were 14∶0 (1.0%–6.3%), 16∶0 (13.5–26.4%), 16∶1n−7 (21.1%–46.3%) and 20∶5n−3 (6.5%–19.5%). The polyunsaturated fatty acids 16∶2n−4, 16∶3n−4, 16∶4n−1 and 20∶4n−6 also comprised a significant proportion of the total fatty acids in some strains. The characteristic fatty acid composition of diatoms is readily distinguishable from those of other microalgal groups. Significant concentration of the polyunsaturated fatty acid 20∶5n−3 (eicosapentaenoic acid) was present in each strain, with the highest proportion in B222 (19.5%). Project supported by the Hi-Tech “863” Programs of the China Ministry of Science and Technology (863-819-02-01).     

DETERMINATION OF TRACE BENZENE HYDROCARBONS IN JIAOZHOU BAY BY ENRICHMENT AND CAPILLARY COLUMN GAS CHROMATOGRAPHY

Trare amounts of benzene hydrocarbons obtained in Jiaozhou Bay (Qindao) were enriched bysorption on a GDX-102 column and eluted by carbon disulfide. The eluted was concenttaled and then de-temened by capillary column gas cbornatognphy.The contents of virious kinds of benzene hydrocarbons in Jiaozhou Bay coastal water were benzene(22.3-141.6)× 10～(-9)g/L, toluate (15.2-94.0) × 10~(-9) g/L, ethyl benzene(11.8-85.1)×10~(-9) g/L, p -xylene(15.2-78.5) ×10(-9) g/L, m-xylene (10.9-79.4) ×10(-9) g/L, o -xylene (12.4-80.1) x ×10(-9)g/L; iso-propyl(8.4- 73.1) x ×10(-9)g/L, n -propyl (6.9-76.4) ×10(-9) g/L, 1, 3, 5-trimethylbenzene (10.9- 35.9)×10(-9) g/L, 1,2, 4-trimethybenzene (10.0- 38.0)×10(-9) g/L, n - butydriare (8. 1 - 34.6) ×10(-9)g/L. The recovery of benzenehydrocarbons was (85.1 -95.6)%.     

Methodology for studies of carbon dynamics between phytoplankton primary production and heterotrophic bacterial secondary production

The SCENTO-System was used to study the carbon dynamics between phytoplankton primary production and heterotrophic bacterial secondary production. Most of the methods used nowadays in situ for limnological synecology studies were applied. Primary production measurement showed an increasing tendency with increasing content of chlorophylla. It provided a true photosynthetic rate lying within the range of eutrophic lakes. Net EOC released from the algae ranged from 8.5 to 27.5 μg C l⁻¹(6h)⁻¹. Accompanying the algal products the number of bacteria increased from 1.475 ×10⁹ to 8.074×10⁹ cells l⁻¹. The bacterial mean cell volume was small, between 0.0315 and 0.0548μm³. Bacterial carbon production from direct growth estimates was compared with independent calculations of bacterial growth from EOC uptake and³H-thymidine incorporation. Direct estimates were 2.97–10.0 μg Cl⁻¹ (24h)⁻¹ with the exception of a zero-growth on the third day. EOC uptake was 123.5–191.0 μg Cl⁻¹ (6h)⁻¹. That calculated from³H-thymidine incorporation was 0.2–0.5 μg Cl⁻¹ (6h)⁻¹.¹⁴C-glucose dark uptake ran parallel to the increasing bacterial biomass. The respiration of glucose was 6.5% (avg.) of the gross uptake. Since the system operated without grazing pressure, a real carbon flow from primary production to bacterial secondary production could be observed.     

DYNAMIC CHANGES OF INORGANIC NITROGEN AND ASTAXANTI—IIN ACCUMULATION IN HAEMATOCOCCUS PLUVIALIS

This study on dynamic changes of culture color,astaxanthin and chlorophylls,inorganic N including N-NO3^-,N-NO2^- and N-NH4^ in batch culture of Haematococcus pluvialis exposed to different additive nitrate concentration showed(1)ast/chl ratio was over 0.8 for brown and red algae,but was usually less than 0.5 for green and yellow algae;(2)N-NO3^-,in general,was unstable and decreased,except for a small unexpected increase in nitrate enriched treatment groups;(3)measurable amounts of N-NO2^- and N-NH4^ were observed respectively with three change modes although no extemal nitrite and ammonia were added into the culture;(4)a non-linear correlation between ast/chl ratio(or color)changes and the levels of N-NO3^-,N-NO2^-,N-NH4^ in H.pluvialis culture;(5)up and down variation of the ast/chl ratio occurred simultaneously with a perceptible color change from yellow to brown(or red)when N-NO3^-,N-NO2^- and N-NH4^ fluctuated around 30,5,5μmol/L respectively;(6)existence of three dynamic modes of N-NO3^-,N-NO2^- and N-NH4^ changes,obviously associated with initial extemal nitrate;(7)the key level of total inorganic N concentration regulating the above physiological changes during indoor cultivation was about 50 μmol/L;and(8)0.5-10mmol/L of nitrate was theoretically conducive to cell growth in batch culture.     

Long-term ecological interactions between nutrient and phytoplankton community in the Changjiang estuary

Both nitrate (NO₃⁻) and soluble reactive phosphate (PO₄³⁻) concentration in the freshwater end-member at the mouth of the Changjiang River have increased dramatically since the 1960s. Within the same period in the sea area, with surface salinity>30, NO₃⁻ concentration has shown an obvious increase, PO₄³⁻ has not changed greatly and dissolved reactive silica (SiO₃²⁻) has deceased dramatically. An examination of the elemental ratio of NO₃⁻ to PO₄³⁻ at the mouth of the Changjiang River did not show a systematic trend from the 1960s to 2000s largely because both nutrients increased simultaneously. In comparison, the elemental ratio of dissolved inorganic nitrogen (DIN) to PO₄³⁻ in surface seawater, with salinity>22, has shown a clearly increasing trend. Furthermore, an overall historical change of the SiO₃²⁻:PO₄³⁻ ratio has undergone a reverse trend in this area. Based on the changes of SiO₃²⁻:PO₄³⁻ and DIN:PO₄³⁻ ratios, we can conclude that an overall historical change of SiO₃²⁻:DIN ratio has decreased in this area from the 1950–1960s to 2000s. The argument that phytoplankton productivity in the Changjiang estuary has been enhanced by increasing nutrient input from the riverine transport was supported by these results. A comparative study analyzing the shift of phytoplankton composition from the mid-1980s to 2000s was also made. The results indicated that the average yearly percentage of diatom species in the Changjiang estuary has decreased from 84.6% during 1985–1986 to 69.8% during 2004–2005. Furthermore, the average yearly percentage of diatom abundance in the Changjiang estuary decreased from 99.5% during to 75.5% over the same time period, while the abundance of dinoflagellates has increased dramatically, from 0.7% to 25.4%.