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Seasonal Variations of Copepod Diversity in the Bay of Villefranche.

Seasonal Variations of Copepod Diversity in the Bay of Villefranche. Stéphane Gasparini & Elvire Antajan 2005 L.O.V. - UMR 7093 CNRS - UPMC BP 28, 06234 Villefranche-Sur-Mer Cedex. In situ community monitoring. Objectives and general context.

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Seasonal Variations of Copepod Diversity in the Bay of Villefranche.

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  1. Seasonal Variations of Copepod Diversity in the Bay of Villefranche. Stéphane Gasparini & Elvire Antajan 2005 L.O.V. - UMR 7093 CNRS - UPMC BP 28, 06234 Villefranche-Sur-Mer Cedex

  2. In situ community monitoring Objectives and general context To better understand the mechanisms controlling planktonic diversity Phytoplankton Microzooplankton (Copepods) Mesozooplankton Macrozooplankton Laboratory experiments • Seasonal scale • Predator prey relationships • Multiannual scale • Interspecific competition

  3. Study site • High planktonic richness: • 141 copepod species (Djordjevic, 1962 ; Seguin, 1972 ; this study) • Observing Service: • Weekly monitoring of hydrology since 1957 • Weekly sampling of zooplankton Pt B

  4. ? Diversity (Shannon H’) Working hypotheses Planktonic diversity depends on the level of stratification. 1 Stratification  More niches  Diversity increase Homogenisation  Less niches  Diversity decrease Planktonic diversity depends on the level ofdisturbance. 2 Stratification Hydrologic stability  Specialized species  Diversity increase Hydrologic instability  Opportunistic species  Diversity decrease Evaluated by the difference in density between surface and bottom Planktonic diversity depends on the level offood resources. 3 Scarce resources  Specialized species  Diversity increase Abundant resources  Opportunistic species  Diversity decrease

  5. ? Diversity (Shannon H’) Working hypotheses Planktonic diversity depends on the level of stratification. 1 Stratification  More niches  Diversity increase Homogenisation  Less niches  Diversity decrease Planktonic diversity depends on the level ofdisturbance. 2 Stratification Hydrologic stability  Specialized species  Diversity increase Hydrologic instability  Opportunistic species  Diversity decrease Evaluée par la différence de densité entre surface et fond Planktonic diversity depends on the level offood resources. Intensity of disturbance 3 Scarce resources  Specialized species  Diversity increase Abundant resources  Opportunistic species  Diversity decrease Evaluated by the distance between successive observations in a factorial space (PCA)

  6. ? Diversity (Shannon H’) Working hypotheses Planktonic diversity depends on the level of stratification. 1 Stratification  More niches  Diversity increase Homogenisation  Less niches  Diversity decrease Planktonic diversity depends on the level ofdisturbance. 2 Hydrologic stability  Specialized species  Diversity increase Hydrologic instability  Opportunistic species  Diversity decrease Planktonic diversity depends on the level offood resources. Intensity of disturbance 3 Resource availability Scarce resources  Specialized species  Diversity increase Abundant resources  Opportunistic species  Diversity decrease Evaluée par la distance entre observations successives dans un espace factoriel (ACP) Evaluated by the concentration in Chlorophyll a

  7. J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 The situation in 1997 and 2002

  8. J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 The situation in 1997 and 2002

  9. J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 The situation in 1997 and 2002

  10. J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 The situation in 1997 and 2002

  11. J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 The situation in 1997 and 2002

  12. J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 J F M A M J J A S O N D J F M A M J J A S O N D 2002 1997 Hypothesis 1 : The stratification

  13. r = 0.583 J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 Hypothesis 2 : The intensity of disturbance

  14. r = 0.745 r = 0.583 J F M A M J J A S O N D J F M A M J J A S O N D 1997 2002 J F M A M J J A S O N D J F M A M J J A S O N D 2002 1997 Hypothesis 3 : The food resources

  15. J F M A M J J A S O N D 2003 A particular case : 2003

  16. J F M A M J J A S O N D 2003 J F M A M J J A S O N D 2003 A particular case : 2003 r = 0.583  r = 0.481 r = 0.745  r = 0.616

  17. Conclusion : scenarii to be confirmed • Prevailing role of the level of food resources in the control of diversity • An environmental enrichment could quickly lead to an enduring loss of diversity. • Potential role of the climatic changes • A multiplication of the extreme events could have a sizeable impact (more important than a gradual increase of the temperature). • Need for confirmation • Analyses in process of additional samples • Comparison with the phytoplanktonic (R. Lemée), microzooplanktonic (J. Dolan) and macroplanktonic (L. Mousseau) diversity. • Experimental studies of trophic relationships.

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