Abordagem transfronteiriça do lixo marinho : a exportação de resíduos flutuantes ao longo de um gradiente estuarino e seus impactos socioeconômicos

This study adopted a multidisciplinary approach to investigate marine debris along the Paranagu Estuarine Complex (PEC) and adjacent areas.The rationale of this study was structured in three chapters with complimentary approaches: investigating dispersal and the trajectories of marine debris using hydrodynamical modelling associated to in situ sampling efforts (Chapter I); analyzing the influence of discrete oceanographic and climatic events [High Riverine Discharges (HRD), Frontal Systems (FS) and Regular Weather Conditions (RWC)] on marine debris quantity and quality (Chapter II); and comprehending the perception and reactions of beach users to actual and eventual marine debris abundance, respectively, thus estimating its potential negative economic effects (Chapter III).In the Paranagu Estuarine Complex gradient, three sectors [Internal (I, tide-dominated), Median (M, wave-dominated/outlet) and external (E; wave-dominated)] were considered for analysis of spatial variances.Results of modeling indicate a residence time shorter than 5 days for floating marine debris before being exported through the estuary mouth.In the open-ocean, floating debris tend to drift firstly southward, followed by a northerly dispersion.Along this trajectory marine debris can be stranded due to meteorological and oceanographical conditions.These findings reveal that floating marine debris is a transboundary concern for the PEC.The influence of these conditions was demonstrated to play an important role in marine debris spatial and temporal distribution.Higher Riverine Discharges (HRD) were determinant in increasing overall abundance, richness of types and quantities of most of the sources.The lowest records for overall abundance varied among internal (RWC) and external (FS) sectors.By identifying the influences of each factor in the internal sector, it was possible to postulate the process of influence of each condition over the tide-dominated sector.However, influences in the external sector might be more complex.Considering that the HRD conditions are more frequent during summer periods, greatest amounts of debris may be seen during periods with more beach users.The perceptions and reactions of second-home owners and users (SHOU) and non-recurrent tourists (T) in two beaches (Pontal do Sul, PS, estuarineoutlet beach; Ipanema, I, open-ocean beach) indicate that these groups were different due to daily expenses (T>SHOU), period of permanence per trip (SHOU>T) and frequency of trips (SHOU>T).The open-ocean beach (I) was worse rated regarding overall beach quality and marine debris generation was mainly attributed to local beach users (>75%).In the estuarine beach (PS), users cited the "marine" source four times more frequently (>35%).More than 85% of beachgoers would avoid a polluted beach with more than 15items/m 2 and alternative destinations would be out of the state (>50%) and out of the municipality (>80%), thus generating transboundary negative economic effects.A potential reduction for local tourism income of 39% was estimated, leading to a decrease in tourism revenue of up to US$8.5 and US$5.7 million per year for the municipality and the state, respectively.In conclusion, the marine debris is a transboundary concern for the PEC due to the exportation of floating debris and the potential losses of income for the municipality and the state.The dispersion is highly influenced by oceanographic and meteorological events.The application of innovative management methods based on the knowledge derived from the transboundary approach is recommended, especially in land-sea transition zones, like PEC.