BIOGEOCHEMICAL CONSTRAINTS IN THE OCEAN:

CONTROLS, MODELLING AND PREDICTION

Location: Arts Building 1390

Tuesday 20 July AM

Presiding Chairs: W I Jenkins (University of Southampton, Southampton Oceanography Centre, UK) and D Smythe-Wright (George Deacon Division, NERC, Southampton, UK)

P08/E/02-A2 0930

ROLES OF BIOGEOCHEMICAL PRODUCTIVITY IN THE CARBON CYCLE USING A SIMPLE GLOBAL OCEAN MODEL

Masahiko FUJII, Motoyoshi Ikeda and Yasuhiro Yamanaka (Graduate School of Enrironmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan, email: fujii@ees.hokudai.ac.jp, mikeda@ees.hokudai.ac.jp and galapen@ees.hokudai.ac.jp)

A simple physical and biogeochemical ocean model is constructed. Horizontally, the global ocean is divided into four regions; i.e., the Pacific/Indian Ocean (PI), the Atlantic Ocean (AT), the Southern Ocean (SO) and the Greenland/Iceland/Norwegian Sea (GIN). The PI and AT are vertically continuous, while the SO and GIN are divided into two, the surface layers (50m thick) and the lower layers. This model is used to estimate the oceanic carbon cycle contributed by physical and biogeochemical processes. The physical parameters are chosen to represent the air-sea CO2 flux, the thermohaline circulation, and vertical and horizontal diffusions. The biological productivity is controlled only by phosphate in the surface layers. The geochemical process is parametrized by a calcite productivity in the surface layers. The products are remineralized in the lower layers. The observed distributions of radiocarbon, phosphate and alkalinity are used as tracers to optimize the parameters. The total carbonate concentration is then calculated, and the vertical carbon flux is quantitatively estimated. A major feature is a clear contrast between the PI and AT; i.e., the total carbonate is richer in the PI than the AT, along with the other biogeochemical components. As the anthropogenic sources increase the CO2 concentration in the atmosphere, the effects appear significantly in the AT, while a signal is extremely weak in the PI.

P08/W/06-A2 0950

BIOGEOCHEMICAL VARIABILITY AND THE NORTH ATLANTIC OSCILLATION.

Michael J. FOLLOWS, Stephanie Dutkiewicz, John C. Marshall (Program in Oceans, Atmospheres and Climate, Massachusetts Institute of Technology, Cambridge, MA 02139, USA); Watson W. Gregg (NASA/Goddard Space Flight Center, Maryland, USA )

Through better understanding of interannual and decadal climatic and biogeochemical variability in the observed record we seek to identify patterns and mechanisms which may be important in global climate change. Time-series observations of biogeochemical indicators in the North Atlantic ocean exhibit significant interannual and decadal variability which, in some cases, correlate with indices of regional climate such as the North Atlantic Oscillation (NAO) index. Remote observations of ocean colour indicate that interannual changes are manifested with coherent patterns on the gyre and basin scale.

We examine the hypothesis that biogeochemical variability in the surface ocean may, in part, be a response to variability in ocean circulation and mixing and thus reflect the large-scale patterns associated with the dominant atmosphere-ocean climate regimes of the region. We use a North Atlantic biogeochemical model driven by twelve-hourly, observed, surface wind-stress and heat fluxes, examining the variability of export and primary production and surface gas exchanges on interannual timescales. We find basin wide patterns in the biogeochemical variations of the model. These patterns resemble those in the physical forcing associated with the North Atlantic Oscillation.

In a model with highly idealised biological cycle, variability in surface heat fluxes and associated convective mixing result in significant variability of nutrient supply and export production on year to year time-scales even in the subtropical gyre where the longer term balances are dominated by advective processes. Introducing an explicit ecosystem model in order to address remote ocean colour observations, biophysical interactions result in a more complex relationship between chlorophyll, primary production and physical forcing.

P08/W/04-A2 1010

NUTRIENT SUPPLY TO THE UPPER NORTH ATLANTIC OCEAN: A MODEL STUDY

A. OSCHLIES, W. Koeve (Institut fuer Meereskunde,D-24105 Kiel, email aoschlies@ifm.uni-kiel.de)V. Garcon (UMR5566/LEGOS, F-31401 Toulouse, emailgarcon@pontos.cst.cnes.fr)

A high-resolution coupled biological-physical model of the North Atlantic is used to investigate regional patterns of nitrogen supply and primary production. For the subtropical gyre, episodic nutrient pulses by eddy-induced upwelling have been suggested to explain why geochemical estimates of nitrate supply to the euphotic zone are an order of magnitude higher than biological and physical ones. This is investigated by varying the level of activity in the model by assimilating altimeter data and by changing the parametrization of horizontal friction. It is found that eddies contribute about one third of the nutrient input into the subtropical Atlantic. The associated mechanisms of the eddy-induced supply are discussed in relation to that of mean advection and different representations of subgrid-scale diapycnal mixing. At higher latitudes, the main pathway of nutrient supply is via deep winter mixing which, after rapid shallowing of the mixed layer, leads to a spring bloom. When forced with daily atmospheric fluxes from the ECMWF reanalysis, the model shows both typical spring blooms characterized by a rapid development of a shallow phytoplankton bloom which is terminated by depletion of nutrients, as well as transient blooms characterized by intermittent chlorophyll maxima separated by phases of a deepening mixed layer. Both simulated scenarios agree well with observations taken at the JGOFS NABE (47N, 20W) site in 1989 and 1992, respectively. The interannual differences in spring bloom development, corresponding nitrate supply, and primary and export production are shown to be closely related to surface heat flux patterns.

P08/E/07-A2 1050

THE VARIABILITY OF EXPORT PRODUCTION OVER THE NORTH ATLANTIC

ALISON J. McLAREN, Richard G. Williams (Oceanography Labs., University of Liverpool, Liverpool. L69 3BX. U.K.); Michael J. Follows (Program in Oceans, Atmospheres and Climate, MIT, Cambridge, MA 02139, USA.)

The dominant physical processes that supply nutrients to the pelagic ecosystems are advection by the circulation and convective mixing. The variability of these physical processes is predicted to cause changes in export production. Follows and Marshall (1999) show that changes in convection linked to the North Atlantic Oscillation (NAO) affect the interannual variability of export production. However, it is unclear which physical process will cause the longer term variability in export production.

An idealised ocean basin model is used to investigate the variability of export production during a five year period with the same NAO phase. The model results suggest that the initial change in the export production in a subtropical gyre is controlled by the anomalous convective supply of nutrients. However, after several years, the anomalous export production is caused by the advective supply of nutrients. During NAO conditions, the changes in advection and convection reinforce each other to enhance or reduce export production over the subpolar gyre. In contrast, the advective and convective changes oppose each other in the subtropical gyre. A method is developed to quantify the variability of the horizontal Ekman advection of nutrients using available data for the North Atlantic; this Ekman supply is particularly important along the flanks of the subtropical gyre (Williams and Follows, 1998). The Ekman nitrate supply into the subtropical gyre is found to follow the NAO cycle and vary annually by up to 40% from the annual mean during 1945-93. This variable Ekman supply is expected to cause changes in the export production when the NAO remains in the same phase for several years.

P08/W/09-A2 1110

REDFIELD RATIOS IN THE DEEP EASTERN NORTH ATLANTIC.

Uli FLEISCHMANN, Alfred Putzka and Alexander Sy

The Redfield ratios for the deep eastern North Atlantic are a difficult subject because of the complex mixture of water masses. This mixture is analysed with a quantitative water mass analysis for a collection of hydrographic data from the deep eastern North Atlantic between 10° N and 60° N. A multiparameter approach was used for this based on the parameters potential temperature, salinity, oxygen and nitrate. A consumption quantity which accounts for oxygen consumption (deltaO) and nitrate (deltaN) remineralisation is included in the analysis. The ratio of deltaO:deltaN in the consumption quantity is varied in the range from 8:14. A deltaO:deltaN ratio of 9 is found to be the best estimate from considerations of the phosphate values, their remineralisation and the quality of the representation of the mixture. The resulting range of the Redfield ratios for the deep eastern North Atlantic is 1:(14.9-15.8):(132-150) for deltaP:deltaN:deltaO with an optimum at 1:15.3:137.

P08/W/02-A2 1130

AN EVALUATION OF GAS-EXCHANGE PARAMETERIZATIONS USING A GLOBAL MODEL OF THE OCEANIC N2O FLUX AND DISTRIBUTION

P. SUNTHARALINGAM (Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA, email:pns@europa.harvard.edu); J. L. Sarmiento (Atmospheric and Oceanic Sciences Program, Princeton University, Princeton, NJ 08544, USA, email:jls@splash.princeton.edu)

A significant source of uncertainty in deriving large-scale oceanic flux estimates directly from surface partial pressure anomalies arises from the parameterization of the gas-exchange coefficient relating the two quantities. In this study, global ocean general circulation model simulations of the marine nitrous-oxide distribution and sea-air flux are used in conjunction with observations of surface N2O partial pressures to evaluate the performance of two commonly used wind-speed dependent parameterizations, namely, Wanninkhof (1992), and Liss and Merlivat (1986).

The net global marine N2O flux of the ocean model is determined by an embedded biological source function and constrained independently by observations of excess N2O and Apparent Oxygen Utilization (AOU) at depth. The model transfer of this predetermined N2O source across the sea-air interface under different gas-exchange parameterizations gives rise to different surface distributions of the air-sea partial pressure anomaly. These are then compared to observational values to evaluate the success of each gas-exchange formulation. Results indicate that the larger averaged transfer coefficients provided by the Wanninkhof (1992) parameterization produce modeled N2O partial pressure anomalies closer to the observed levels. The sensitivity of our conclusions to the assumptions of the underlying biological and circulation models will also be discussed.

P08/W/03-A2 1150

AIR-SEA EXCHANGE COEFFICIENTS OF GASES

David WOOLF (School of Ocean and Earth Science, University of Southampton, Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, UK, email dkw@mail.soc.soton.ac.uk)

Some recent laboratory experiments give new insights into the kinetics of air-sea gas exchange. Processes and rates of gas exchange are investigated in two sets of experiments. In the first set, gas transfer is measured at moderate wind stress, with and without artificial bubble plumes. The gas supply to the bubbles is manipulated, allowing the contribution of sub-surface bubbles (bubble-mediated transfer) and surface exchange (including that resulting from surfacing bubble plumes) to be separated. In the other experiments, gas transfer is measured at high wind stresses, but low rates of bubble entrainment (relative to the ocean).

Tuesday 20 July PM

P08/W/07-A2 1400

COUPLED PHYSICAL/BIOLOGICAL MODELLING IN THE ANTARCTIC POLAR FRONT

CH. DIETERICH; I. Hense; R. Redler (Alfred Wegener Institute, 27568 Bremerhaven, Germany); C. B"oning (Institute f"ur Meereskunde, 24105 Kiel, Germany)

During JGOFS cruises in the Atlantic sector of the Southern Ocean relatively high chlorophyll concentrations were observed along the Antarctic Polar Front. It has been hypothesized that small-scale variability plays a major role in setting up the prerequisites for phytoplankton growth. Enhanced vertical transports of nutrients and trace elements along the front, mesoscale upwelling and shallow mixed layers promote phytoplankton blooms.

To investigate the influence of mesoscale dynamics on the regional ecosystem we use a coupled physical/biological model. The physical model is a primitive equation model encompassing the South Atlantic Frontal System from about 60S to 40S, run in both eddy-resolving and non eddy-resolving resolution. It has been developed in the framework of FLAME (Family of Linked Atlantic Model Experiments). The physical model is coupled with an ecosystem model, with special emphasis on the regional phytoplankton community. In sensitivity studies with the physical model we examine the impact of mesoscale variability on phytoplankton dynamics.

P08/W/08-A2 1420

A COUPLED PHYSICAL-CHEMICAL-BIOLOGICAL MODEL OF THE INDIAN OCEAN

P.S.SWATHI and M.K.Sharada (CSIR Centre for Mathematical Modelling and Computer Simulation NAL Belur Campus, Bangalore 560 037, India, e-mail swathi@cmmacs.ernet.in, sharada@cmmacs.ernet.in); K.S.Yajnik ( Regal Manor, 2/1 Bride St., Langford Town, Bangalore 560 025, India, e-mail ksy@letterbox.com)

A coupled physical-biological-chemical model for studying the time-variation of primary productivity and air-sea carbon-di-oxide exchange in the Indian Ocean is being developed at C-MMACS. The physical model is based on the Modular Ocean Model, Version 2 (MOM_2) and the biological model describes the non-linear dynamics of a 7-component system. The chemical model includes dynamical equation for the evolution of dissolved inorganic carbon (DIC) and total alkalinity. The interaction between the biological and chemical model is through the Redfield ratio. The CO2 content of the surface layer is obtained from the chemical equilibrium equations of Peng et. al, 1987. Transfer coefficients for air-sea exchange of CO2 are computed dynamically based on the wind speeds. The coupled model reproduces the strong upwelling blooms seen during the SW Monsoon and the weak blooms in the Northerna Arabian Sea in winter caused by convective overturning. The Bay of Bengal is strongly affected due to the low salinity in the area leading to a much smaller pCO2 concentration that the Arabian Sea. On an annual scale the entire Indian Ocean is an out-gassing region for air-sea CO2 transfer.

P08/W/01-A2 1440

TESTING THE IRON HYPOTHESIS IN SITU IN THE PACIFIC AND ANTARCTIC OCEANS

Cliff LAW and Phil Nightingale (CCMS, Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth, Devon PL1 3DH, UK, Email: csl@ccms.ac.uk., pdn@ccms.ac.uk. A. Watson (School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK, E:mail: a.watson@uea.ac.uk. P. Boyd (Centre of Excellence for Chemical and Physical Oceanography, University of Otago, Dunedin, NZ, Email: P.Boyd@alkali.otago.ac.nz).

Iron (Fe) limitation of phytoplankton productivity in the High-Nutrient Low-Chlorophyll regions of the oceans has long been suspected. However, it is only with the in situ releases into the surface waters of the equatorial Pacific within IronEx1 and IronEx2 that this has been proved conclusively. The strong response of the phytoplankton to iron addition, with chlorophyll increasing 30-fold and a decrease in surface fCO2 of 70 atm during IronEx2, supports previous observations that iron flux may influence atmospheric CO2. However increased iron fertilisation of the Equatorial Pacific may be relatively insignificant in terms of the global ocean sink. Instead consideration of ocean circulation suggests that it is the Southern Ocean where Fe-induced increases in productivity may impact the ocean carbon sink. The first in situ release of iron into the surface waters of the Antarctic took place during the SOIREE cruise to the south of the Polar Front at 61-62S in February 1999. The response of the biota and the biogeochemistry will be reviewed, with re-assessment of the role of Fe in limiting productivity and the ocean carbon sink.

P08/E/04-A2 1500

SPATIO-TEMPORAL VARIABILITY OF PCO2 IN THE MEDITERRANEAN SEA

Miléna BEGOVIC and Claire Copin-Montégut (Laboratoire de Physique et Chimie Marines, Université Pierre et Marie Curie, Observatoire Océanologique de Villefranche-sur-Mer, 06238 Villefranche-sur-Mer Cedex, France, email: milena@obs-vlfr.fr)

Time series observations provide valuable insights into the natural seasonal variability of the oceanic carbon cycle. Monthly measurements of hydrography and biogeochemical properties have been made in the central part of the northwestern Mediterranean Sea (Ligurian Sea), in the course of the DYFAMED (France-JGOFS) operation. The annual cycle of the Ligurian Sea is defined from well-mixed conditions in winter to a progressive stratification in spring and early summer and a strong thermohaline stratification in summer and fall. So hydrological and trophic conditions encountered along the year are representative of conditions existing in large areas of the world ocean (from mesotrophy to oligotrophy). Continuous underway measurements of the partial pressure of CO2 in surface water have been made monthly since February 1998, from the Riviera coast to the DYFAMED site (56 km off Nice, 43°25' N, 7°52' E) and twice a year to Calvi (Corsica, 42°34' N, 8°45' E).

Characteristic seasonal patterns were observed along these transects. The changes in pCO2 ranged in 1998 from ~315 µatm in winter, to ~450 µatm in summer. Winter mixing induced high variations of pCO2 in surface waters. In February and March, the coldest waters were supersaturated with respect to the atmosphere. These cold waters result from the mixing of surface water with deep water up-welled at sea surface. On the other hand, waters of any tenth degrees warmer were largely under-saturated with CO2. This under-saturation results from the biological production, which has been emphasised by up-welling of nutrient-rich waters. Surface sea waters were under-saturated until the end of May, and become supersaturated as a consequence of the summer warming. But if pCO2 values calculated at the same temperature are compared, a general trend toward a decrease in pCO2 with temperature since winter months is observed. This decrease can be explained by the biological production in surface water, which should stop when surface water becomes depleted in nutrients. When surface waters are super-satured, gas exchange of CO2 with the atmosphere is not sufficient to explain this decrease. So in fact, the biological uptake of CO2 should continue in absence of nutrients, which has been also observed during previous studies in the same region.

P08/E/03-A2 1520

MODELLING THE VERTICAL BIOCHEMICAL STRUCTURE OF THE BLACK SEA: DYNAMICAL COUPLING OF THE OXIC, SUBOXIC AND ANOXIC LAYERS

Temel OGUZ (Middle East Technical University, Institute of Marine Sciences, Erdemli, Icel, Turkey, e-mail:oguz@ims.metu.edu.tr); Hugh W. Ducklow (Virginia Institute of Marine Sciences, The College of William and Mary, Gloucester Point, VA, USA, e-mail:duck@vims.edu); Paola Malanotte-Rizzoli (Massachusettes Institute of Technology, Department of Earth, Atmospheric and Planetary Sciences, Cambridge, MA, USA, e-mail:rizzoli@mit.edu); James W. Murray (University of Washington, School of Oceanography, 104 Ocean Teaching Building, Seattle, WA 98195-7940, USA, e-mail:jmurray@ocean.washington.edu)

The upper layer biogeochemical structure of the Black Sea is simulated using a one dimensional vertically-resolved coupled physical-biochemical model. The physical model involves the mixed layer dynamics endowed with Mellor-Yamada turbulence parameterization, and is coupled with the biochemical model by the specification of water column eddy diffusivity and temperature structures. Its biological component considers two phytoplankton species groups (flagellates and diatoms), three zooplankton size groups (micro-, meso- and macrozooplankton), bacterioplankton, particulate and dissolved organic materials. They are complemented by the equations for the ammonium, nitrite, nitrate as well as for the dissolved oxygen, hydrogen sulphide and additional ones for major redox reactions taking place across the suboxic-anoxic interface. The model is thus able to represent different biochemical processes interacting with each other in different parts of the water column, and allows a dynamical coupling between the euphotic zone, the oxycline/upper nitracline layer, the suboxic and the anoxic layers.

P08/E/01-A2 1600

THE POSSIBLE RELATIONSHIP BETWEEN EUTROPHICATION AND SUB-OXIC ZONE OF THE BLACK SEA

Sergey K. KONOVALOV (Marine Hydrophysical Institute, Kapitanskaya 2a, Sevastopol 335000, Crimea, Ukraine, email: sergey@alpha.mhi.iuf.net); James W. Murray (School of Oceanography, University of Washington, Box 357940, Seattle, WA 98195-7040, USA, email: jmurray@ocean.washington.edu)

Sub-oxic zone of the Black Sea appears to be related to the nature of oxygen/sulfide interactions rather than eutrophication of this marine basin. The existing hypotheses on the nature of the sub-oxic zone cannot solve the main question about the redox imbalance of this zone. It is known that the downward diffusive flux of oxygen at the upper boundary of sub-oxic layer is 10-times larger than the upward diffusive flux of sulfide at the lower boundary. To solve the redox balance we have proposed the presence of other sinks of oxygen, beside oxidation of sulfide. We have analyzed existing data on the distributions of oxygen, sulfide, nutrients, temperature and salinity in the Black Sea from 1960 to 1995. We highlight a number of observations regarding temporal variations in the structure of sub-oxic zone and adjacent layers of water: different dynamics of the upper and lower boundary of sub-oxic zone, a correlation between the intensity of eutrophication and distribution of oxygen in the layer of the oxycline, significant correlation between apparent oxygen utilization and nitrate concentration in the middle oxycline, and a highly significant correlation between changes in distribution of nutrients. These observations suggest that about 90% of that oxygen should be consumed during oxidation of sinking particulate organic matter rather than oxidation of the upward flux of sulfide from the anoxic zone. This hypothesis highlights new links in the oxic/anoxic ecosystem of the Black Sea. It demonstrates that the entire biogeochemical structure of the Black Sea depends on the intensity of eutrophication.

P08/E/05-A2 1620

COMPARATIVE RELIABILITY ASSESSMENT OF VARIOUS METHODS OF PRIMARY PRODUCTION MEASUREMENTS.

GORIOUNOVA V.B, Sapozhnikov V.V, (All Russian Federal Research Institute of Fisheries and Oceanography, V.Krasnoselskaya 17, Moscow, 107140, Russia, e-mail: vera@pisarev.msk.ru)

The comparative measurements of primary production (PP) with different methods: oxygen, radionucleic and with the help of sounding device PrimProd, were made during ecosystem cruise in the Norway Sea. Preliminary analysis of data showed, that the absolute values, received with the help of oxygen methods exceed those of PrimProd by 3-4 times. However, the sounding device PrimProd was calibrated using radionucleic method, and even more significant difference was obtained while comparing the results of oxygen and radionucleic methods. Radionucleic estimation of PP value was made in small volume bottles (100 ml), that provided hypertrophied growth of microheterotrophic organisms onto the walls of the bottles and so the results become lower. The sounding device PrimProd have certain advantages: it gives the opportunity of PP measuring "in situ" not only at the day time, but at night as well; it also allows more correct computation of integral PP value in photic layer.

Received results were compared with the distribution of nutrients, dissolved oxygen and main hydrophysical parameters. Hydrophysical parameters' influence on the formation of mesoscale ecosystems with different values of PP is shown.

P08/W/05-A2 1640

EARLY DIAGENETIC CHANGES IN THE SHELF SEDIMENTS OF THE NORTH JAPAN SEA

K. ABDULLA BAVA and Ken Ikehara (Marine Geology Department, Geological Survey of Japan, 1-1-3 Higashi, Tsukuba, 305-8567 JAPAN. Phone: +81-298-543627 Fax: +81-298-543589 Email: bava@gsj.go.jp)

The exchange of dissolved substances across the sediment-water interface is an important process affecting the chemical composition of water bodies. This is particularly important for coastal marine environments, where nutrient regeneration in benthic sediments can supply a significant fraction of the nutrient requirements of primary producers in overlying water. In this investigation, sediment cores and its associated pore waters were collected from shelf region of North Japan Sea to understand the characteristics in the vertical profile of this highly productive marginal sea. Seven cores were collected using Multiple Corers and sectioned with an interval of 0.5 cm up to 10 cm and with 1 cm afterwards. Physico-chemical parameters such as Eh, pH, total C and N in the sediments and Fe, Mn, Ca, Mg, Si, Sr, Zn, NO2, NO3, PO4, and NH4 in the pore waters were measured.

A general downward decrease of Eh, NO2, NO3 and increase of pH, NH4, PO4 in their vertical pore water profile, and C and N depletion downward in the sediment column, indicate the microbial degradation of the organic matter and remineralization. In our results, significant enrichment of NO3 in interstitial waters is recorded in a thin layer of 0 to 2 and 0 to 7. 5 cm in the shallower sediments and a layer of 0 to 13 cm layer in the case of deeper sediments. The sharp decline of of NO3 values and the uniformly very low NH4 profiles at surficial levels are also noted. The consistent NH4 minimum in the upper sedimentary layer is mainly caused by the chemical removal of NH4 by oxidation to NO2 and NO3. The increase in PO4 concentration in interstitial waters with depth can be explained due to the release of PO4 during mineralization of organic matter and dissolution of phosphorus bearing solid phases in the existing reducing condition. Fe and Mn distribution in the pore waters are controlled by the redox condition of the sediment. The distribution of the other elements are influenced by mobility of the Fe and Mn and their relation to other parameters are also discussed in the paper.

P08/P/01-A2 1700

THE STUDY OF RED TIDE FORECAST MODEL IN THE YANGTZE ESTUARY

Wang Zhengfang (Second Institute Oceanography, SAO 310012 Hangzhou PRC)

I v haiYan Zhang qing lu yong (Second Institute Oceanography, SAO 310012

Hangzhou P.R.CHINA)

The study about red tide short time forecast model was carried on the Yangtze river estuary on May to August 1995 to May to September 1997. In the seasons of easy discoverable red tide, some of chemical and physical times, such as: water depth, water temperature, transparent degree, water colour, specific gravity, dissolved oxygen, chemical oxygen consumption, nutrients (N,P) were determined in the studied sea area.

The result was indicated that suit to short time forecast about red tide in the Yangtze river estuary. The model is Z = SAL-3. 96DO-26. 97pH-5.42PO4-P.