Análise espaço-temporal de encalhes de aves marinhas no litoral sul e sudeste brasileiro

Abstract

The group of seabirds is composed of different species with unique physiological adaptations that allow them to forage and migrate long distances in the ocean. These characteristics make them a crucial link between marine and terrestrial environments, providing essential services for ecosystem balance. However, they are exposed to a wide range of natural and anthropogenic threats that impact their populations, potentially resulting in the stranding of moribund or dead specimens on beaches worldwide. The processes behind these events are poorly understood, so this study aimed to analyze the strandings of seabirds on the south and southeast coasts of Brazil. The goal was to understand possible spatial and temporal patterns of strandings, as well as the influences of environmental and anthropogenic variables, during the years 2016 and 2019. The results revealed a well-defined spatial pattern, with higher abundance, richness, and diversity of strandings in the southern mesoregions and a decrease in the northern mesoregions along the Brazilian coast. Temporal patterns varied mainly by migratory status. Ecological indices of resident species showed higher strandings during the spring months and were positively related to wind intensity, reflecting primarily the reproductive period and fledgling departure of these species. Migratory species from the northern hemisphere also experienced peak strandings during the spring months, related to increased wave height and wind intensity. Six major mass stranding events were observed in the spring of 2016, mainly involving Manx shearwaters Puffinus puffinus. For these species, the southern hemisphere spring reflects the trans-equatorial migration period they undertake to reach the Patagonian Shelf during the northern hemisphere winter. Strandings of birds from the southern hemisphere mainly occurred in the winter months when these species migrate to the Brazilian coast during the non-breeding period. Abundance, richness, and diversity were higher with increased wind intensity and decreased sea surface temperature. Among southern species, the Magellanic penguin Spheniscus magellanicus exhibited the highest abundance, also occurring in winter months, with females and young individuals being predominant in the stranding population structure. The stranding of this species decreased with increasing temperature and increased with higher wind intensity. However, when removing the five extreme stranding events, particularly in 2018, which seem to be related to ENSO stages, wind intensity loses significance. This exemplifies the importance of this variable in the drift of bodies at sea reaching the beaches. This thesis provides valuable information about the dynamics of the seabird community on the Brazilian coast, being the first to evaluate such an extensive stretch of beaches in Brazil and the strandings in the mesoregions that compose it. Additionally, it demonstrates that the southern coast, particularly in the state of Santa Catarina, deserves attention for the implementation of conservation actions directed towards different species of seabirds.