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Connectivity of mangroves in the indonesian archipelago through dispersal pathways of propagules using an ocean circulation model

Proisy C., Sidik F., Prospéri M.J., Suhardjono, Tranchant B.. 2016. In : EcoSummit 2016 - Ecological Sustainability: Engineering Change. Montpellier : INRA, 1 p.. International EcoSummit Congress 2016. 5, 2016-08-29/2016-09-01, Montpellier (France).

Despite a consensus on the leading role of ecological connectivity in ecosystem functioning , w e s till know little about the oceanic pathways followed by buoyant mangroves propagules and the number of these reproductive plant organs drifting from site to site . This work is a numerical study aiming to explore the connectivity pathways induced by ocean currents between mangroves regions in the Indonesian archipelago, the centre of mangrove diversity. For drift simulations, we use the surface ocean currents produced by the INDO12 regional ocean model developed in the frame work of the INDESO project. It operationally provides realistic simulations of the ocean circulation at an horizontal resolution of 1/12° within the Indonesian waters. The numerical study consists in simulating the dispersal of propagules from mangrove regions as pathways of drifting particles released from upstream areas and entrained by ocean surface currents during a given time window . Six upstream sites have been identified among the largest Indonesian mangrove regions by assuming plausible offshore exportation of propagules. Downstream sites corresponded to any mangrove region of particular interest for rehabilitation, protection or conservation. The ratio between the number s of particles released from a given upstream site and the number of particles made available offshore of a given downstream site yields a simple estimate of the connectivity strength between the two regions. The study is repeated for various time frame s ranging from one week to one year, but only year 2008 has been considered so far. First results suggest that, within a few months, the Bird's Head Papua mangroves can deliver propagules to a large part of Southeast Indonesia. In addition, ongoing laboratory experiments on propagules buoyancy and survival times will be presented in the perspective of a better evaluation of both long-distance dispersal and shifts in connectivity pathways due to seasonal and annual oceanic variability.

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