Modelagem do transporte de propágulos de mangue na plataforma continental do Ceará

Abstract

The propagule is the mangrove dispersal unit. Understanding their transport by estuarine and platform circulation rewards better management of mangrove areas through examples of connectivity between mangrove species in the state of Ceará. The present study aims to investigate the marine transport of propagules originating from the Pacoti River to mangrove areas to the west. In this sense, the FLOW module of the Delft3D numerical model was used to simulate the circulation on the shelf and estuary. The trajectories of the propagules of the species Rhizophora mangle, Avicennia germinans and Laguncularia racemosa were simulated by the particle module (PART). When comparing the tidal data obtained by the model and collected for validation for the platform and the tolerated estuary, it was found that: for the platform, there was a mean squared error (RMSE) of 0.03 cm and a skill of 0.99% for the tidal amplitude data. Among the parallel-to-shore velocity component data, an RMSE was obtained with a value of 0.03 m/s and an ability of 85%. For the estuary of the Pacoti River, in the comparison between the observed and modeled current intensity data, an RMSE of 0.29 m/s and an ability of 81% were obtained. The trajectories of the propagules released into the Pacoti River estuary showed that they remained about 15 days previously to start leaving the study area and gradually decay to about 0% in one month of transport. The transport had a great influence of the wind, being verified from east to west, so that the orientation of the coast and the wind were decisive for the propagules to be closer together or farther from the coast. Considering the obligatory dispersion and fluctuation time for each of the observed species, Laguncularia is a species that would have a trajectory range restricted to the state of Ceará, and Avicennia and Rhizophora could be dispersed outside of the state. Within the Fortaleza region, the propagules followed trajectories conditioned by the pattern of vortices generated by the shear of the current generated by the spikes that trapped them for longer than in free sites, these works being, therefore, areas of possible deposit of propagules. In general, the possibility of connection between the estuaries through eastern propagules of the Pacoti River is conditioned by the currents, winds and physiography of the coast, and the species Rhizophora mangle has a greater possibility of exchanges to external estuaries due to the characteristics of survival and establishment of this species.