Cristin-prosjekt-ID: 278700
Sist endret: 17. september 2008, 19:50

Cristin-prosjekt-ID: 278700
Sist endret: 17. september 2008, 19:50
Prosjekt

Regime shifts in the Black Sea, a population dynamics ade wavelet approach

prosjektleder

Nils Christian Stenseth
ved Centre for Ecological and Evolutionary Synthesis ved Universitetet i Oslo

prosjekteier / koordinerende forskningsansvarlig enhet

  • Centre for Ecological and Evolutionary Synthesis ved Universitetet i Oslo

Tidsramme

Avsluttet
Start: 1. februar 2008 Slutt: 31. desember 2009

Beskrivelse Beskrivelse

Tittel

Regime shifts in the Black Sea, a population dynamics ade wavelet approach

Vitenskapelig sammendrag

Any marine system may suddenly jump to a new state dominated by different species than used to dominate the system earlier. These large-scale transitions between alternative states are known as regime shifts and have been reported for several systems of the world ocean.Apart from the ecological implications that such abrupt changes may have for the ecosystems, they often have profound negative socio-economic consequences for the societies dependent upon such marine systems since the new dominant species may not be as economically important as the previous ones. An improved understanding of the mechanisms driving these types of changes is therefore a central issue to improve ecosystem management. Key elements in such an improved understanding will be a better appreciation of non-linear internal processes and external drivers.Due to the overriding importance of sea currents in the oceans, changes in the oceanic circulation or weather pattern may be expected to be key drivers of change. Moreover, the condition of open systems makes the description of the biotic feedbacks that might stabilize the community more difficult than for lakes for example. However, the shifts of equilibrium states are sometimes reflected more consistently by the biological data than by the physical indices, suggesting the interplay of the biotic feedbacks. The Black Sea is a highly enclosed marine system for which the underlying mechanisms having lead to the different stable states are fairly well understood – most likely because of the fairly closed nature of this marine system. Therefore, the Black Sea marine system constitutes an ideally one for which to study the dynamic nature of such regime shifts. Using modern statistical techniques and the rich time-series data available for the Black Sea, the study of such regime changes is the overall focus of this proposal.In a food web, top-down and bottom-up regulations compete for dominance at each trophic link. These effects have been investigated in the Black Sea in terms of degree of variance and delay between consecutive trophic levels, the automatic sequential method and using a dynamic mass-balance model ‘Ecopath with Ecosim’. However, the exact form of the trophic interaction (linear/nonlinear, constant/varying, etc.) has not been described and the effect of the environmental forcing has not been integrated yet. In this project we suggest to revisit the system by using complementary statistical methods of analysis. Specifically, we suggest carry out statistical modelling of the data by using a population dynamics model as the model-base, a model which is explicitly developed to account for non-linearities and regime-dependent trophic interactions (see below for a detailed description) together with environmental variables as covariates. The group of scientists have profound experience in such analysis. We also propose to use wavelet analysis, a time-frequency decomposition of the variance that is especially useful to study non-stationary and transients signals. This powerful method can be extended to bivariate cases to study local associations between biological and environmental fluctuations. We suggest using this approach to investigate the relationship between environmental variables and the components of the trophic web, in order to identify and characterize, in terms of date, duration and frequencies, the effect of different environmental variables on the system. The group of scientist has profound experience in such analysis as well. We are convinced that such new and complimentary approaches will contribute to the better description and understanding of the feedback mechanism and alternative stable states regulating this system in particular, and the marine system in general.

prosjektdeltakere

prosjektleder
Aktiv cristin-person

Nils Christian Stenseth

  • Tilknyttet:
    Prosjektleder
    ved Centre for Ecological and Evolutionary Synthesis ved Universitetet i Oslo
Aktiv cristin-person

Marcos Llope Peri

  • Tilknyttet:
    Prosjektdeltaker
    ved Centre for Ecological and Evolutionary Synthesis ved Universitetet i Oslo
Inaktiv cristin-person

Tristan Alexander Rouyer

  • Tilknyttet:
    Prosjektdeltaker
    ved Centre for Ecological and Evolutionary Synthesis ved Universitetet i Oslo
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