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  • 10/12/2007

    Modeling of the primary production in the Bizerte Lagoon Modeling of the primary production in the Bizerte Lagoon –– Description of climatic change effects by an hydroDescription of climatic change effects by an hydro--ecological ecological

    threethree--dimensional modeldimensional model

    by : by :

    Béchir BEJAOUI, Ali HARZALLAH & Mahmoud MOUSSA

    Email: [email protected]

  • 10/12/2007

    Several methods have been used to resolve this problematic. The coupled dynamic-ecology modeling is actually a very interesting tool for studying the marine ecosystems under the effect of anthropogenic interventions. This technique is also used to predict the future evolution of the ecosystems under climate change.

    The model developed at our institute is used to study the impact of climate change on the Bizerte Lagoon ecosystem.

    How can we predict the effects of external forcing on marine ecosystems ?

    What is the problematic ?What is the problematic ?

  • 10/12/2007

    Presentation of Bizerte LagoonPresentation of Bizerte Lagoon

    Situation: Latitude : 37°8' - 37°14' N Longitude: 9°46' - 9°56' E

    Characteristics: An area of about 128 km2 (11 km and a maximum length of 13 km) with a mean depth of 7 m.

    Connection: The lagoon is connected to the Mediterranean sea by 6 km inlet (12 m depth and 0.8 km width). and to the Ichkeul Lake through the Tinja channel of approximately 5 km length.

    Continental Hydrology: The catchment's area is about 380 km2 with total amount of fresh water discharge of 125 Mm3/year (ANPE, 1990) .

  • 10/12/2007

    - The Bizerte lagoon model is 3D sigma coordinate system (σ) (Based on Princeton Ocean Model).

    - The lagoon is discretized into 61x52 grid- points.

    The dynamic grid model

    Hydrodynamic modelHydrodynamic model

  • 10/12/2007

    EcosystemEcosystem ModelModel Conceptual diagram of the Bizerte Lagoon ecosystem modelConceptual diagram of the Bizerte Lagoon ecosystem model

    ZOO

    NH4E

    NDET O2E

    NDETSNH4S NO3S Mineralization

    NO3E

    Diff

    Diff

    D iff

    PHYT

    Se di

    m e n

    ta tio

    n

    Uptake

    Up tak

    e

    Nitrification

    Gra zin

    g

    Mineralization

    Death

    Denitrification

    Death

    Faeces

    Ex cr

    et i o

    n TE

    O2E O2E

    Ph ot

    os yn

    th es

    is

    Respiration

    Re sp

    ira tio

    n

    R ea

    er at

    io n

    Light WindRiver

    O2E

    TE

    TS O2S O2STS O2STS

    O2ETE

    So la

    r r a d

    ia ti o

    n D

    iff

  • 10/12/2007

    Ammonia and OxygenAmmonia and Oxygen EvolutionEvolution

    Season variation: Ammonia - Oxygen

    0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 0

    1 0

    2 0

    3 0

    4 0

    5 0

    6 0 E v o lu tio n d e la c o n c e n tra tio n d e N H 4

    jo u r

    C (m

    gN /m

    3)

    N H 4 m N H 4 s

    0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 3

    4

    5

    6

    7

    8

    9 E vo l u t io n d e la co n c e n t ra ti o n d e O 2

    jo u r

    C (g

    /m 3)

    O 2 m O 2 s

  • 10/12/2007

    Interrelation between Current Temperature Interrelation between Current Temperature and Chlorophylland Chlorophyll--aa

    2

    3

    4

    5

    6

    7

    8

    9.78 9.8 9.82 9.84 9.86 9.88 9.9 9.92

    37.14

    37.16

    37.18

    37.2

    37.22

    37.24

    37.26

    P hyt. s imulé à la s urface en é té 2003 : mg/m3

    Phytoplankton

    30

    30.5

    31

    31.5

    32

    32.5

    33

    33.5

    34

    34.5

    35

    9.78 9.8 9.82 9.84 9.86 9.88 9.9 9.92

    37.14

    37.16

    37.18

    37.2

    37.22

    37.24

    37.26

    Temp. s imulée à la s urface en été 2003 : °C

    Temperature

    9.78 9.8 9.82 9.84 9.86 9.88 9.9 9.92

    37.14

    37.16

    37.18

    37.2

    37.22

    37.24

    37.26

    Vitesse s imulée à la surface en été 2003 : m/s

    Surface Current

  • 10/12/2007

    Study of climate scenariosStudy of climate scenarios

    Case study I: Extreme Case study I: Extreme heatwaveheatwave, ,

    Case study II: Global warming,Case study II: Global warming,

  • 10/12/2007

    Case study ICase study I:: Extreme heatwaveExtreme heatwave MarchMarch--AprilApril--MayMay

    Wind*0.2, LH (-5W/m2), SW (+50W/m2), SH (+7 W/m2), Prec*0.2, Rivers*0.2

    3 6 5 7 3 0 7 8 9 8 8 0 1 0 9 5 0

    1

    2

    3

    4

    5

    6

    7

    8

    9

    1 0

    1 1 P h y t . C O N TR O LE (B ), V A G U E C H A LE U R m a rs -m a i (R )

    jo u rs

    m g/

    m 3

    2 0 0 2 2 0 0 3 2 0 0 4

    Chla: Controle (B). Heatwave (R)

  • 10/12/2007

    Case study ICase study I:: Extreme heatwaveExtreme heatwave MarchMarch--AprilApril--MayMay

    Wind*0.2, LH (-5W/m2), SW (+50W/m2), SH (+7 W/m2), Prec*0.2, Rivers*0.2

    3 6 5 7 3 0 7 8 9 8 8 0 1 0 9 5 0

    1

    2

    3

    4

    5

    6

    7

    8

    9

    1 0

    1 1 Z o o . C O N T R O L E (B ), V A G U E C H A L E U R m a rs -m a i (R )

    jo u rs

    m m

    ol N

    /m 3

    2 0 0 2 2 0 0 3 2 0 0 4

    Zoo: Controle (B). Heatwave (R)

  • 10/12/2007

    Case study IICase study II:: Global Global warmingwarming

    Heat (+7W/m2), Prec *0.7, Rivers *0.7, + evap*1.

    3 6 5 7 3 0 1 0 9 5 1 4 6 1 1 8 2 6 2 1 9 1 -0 . 8

    -0 . 6

    -0 . 4

    -0 . 2

    0

    0 . 2

    0 . 4

    0 . 6

    0 . 8 O 2 : F U T U R -A C T U E L ~ -3 %

    jo u rs

    g/ m

    3

    2 0 0 1 2 0 0 2 2 0 0 3 2 0 0 4 2 0 0 5 2 0 0 6

    O2: Future-Actual ~ -3%

  • 10/12/2007

    Case study IICase study II:: Global Global warmingwarming

    Heat (+7W/m2), Prec *0.7, Rivers *0.7, + evap*1.

    -8

    -7

    -6

    -5

    -4

    -3

    -2

    -1

    9.78 9.8 9.82 9.84 9.86 9.88 9.9 9.92

    37.14

    37.16

    37.18

    37.2

    37.22

    37.24

    37.26

    Phyt. FUTUR - PRESENT (été 2003) : mg/m3Chla: Future-Actual Summer 2003 (mg/m3)

  • 10/12/2007

    Case study IICase study II:: Global Global warmingwarming

    Heat (+7W/m2), Prec *0.7, Rivers *0.7, + evap*1.

    3 6 5 7 3 0 1 0 9 5 1 4 6 1 1 8 2 6 2 1 9 1 -4

    -2

    0

    2

    4

    6

    8

    1 0 F LU X E N TR A N T C A N A L : F U TU R -A C TU E L ~ 5 1 0 %

    jo u rs

    m m

    /jo ur

    2 0 0 1 2 0 0 2 2 0 0 3 2 0 0 4 2 0 0 5 2 0 0 6

    Water input from inlet: Future-Actual ~ 5-10 %

  • 10/12/2007

    The possible evolution of the Lagoon under future global heat

    The lagoon will behave The lagoon will behave like (as) a concentration basinlike (as) a concentration basin.

    LagoonInlet

    A thermoA thermo--halinehaline ventilation ventilation in the inlet could save itin the inlet could save it

    Harzallah A.

  • 10/12/2007

    Conclusions & PerspectivesConclusions & Perspectives

    ConclusionsConclusions

    The model allowed to reproduce the Bizerte Lagoon ecosystem The model allowed to reproduce the Bizerte Lagoon ecosystem variables,variables, The model could be used as a tool to simulate the effect of climThe model could be used as a tool to simulate the effect of climate ate changes on ecosystems evolutionchanges on ecosystems evolution..

    PerspectivesPerspectives

    Distinguish micro and Distinguish micro and mesomeso--plankton in phytoplankton and plankton in phytoplankton and zooplankton, zooplankton, Develop an operational version of the model.Develop an operational version of the model.

  • 10/12/2007

    Thank you for your attentionThank you for your attention

    Grazie per il vostro ascolto.Grazie per il vostro ascolto.