Seaweed dispersion under different environmental scenarios based on branches settling velocity and hydrodynamic lagrangian model

Abstract

Abstract We examined the spatial pattern of seaweed branches dispersion based on lagrangian numerical simulation of an experimental cultivation of the seaweed Kappaphycus alvarezii. Sambaqui Beach seaweed cultivation located in the Bay of Santa Catarina Island southern Brazil was used as case study. This work is the first step towards understanding the dispersion and the range of detached branches in the estuarine region. For that, the use of hydrodynamic modeling as tool to support the evaluation of the water dynamics and particles fate was considered. Several environmental datasets are needed as input for hydrodynamic mathematical models, like bathymetry, tide time series, and branches settling velocity. The experiments on branches vertical velocities, in this study, varied from 3.2 until 5.7\xa0cm.s−1, which presented a high correlation with branches volume. These velocities associated with the hydrodynamic model resulted that 90% of the branches will disperse to an area varying from 2 to 6 ha depending on the simulated scenario. Besides, model results shows that particles traveled distances up to 2.5 km, but most of them did not reach the coastline. Although the need for a large amount of data and numerical modeling effort, the results show that this type of approach can reduce the monitoring area around 75% and consequently reduce the need for human resources, time, and inputs in monitoring the dispersion of branches of exotic seaweed in the environment.