Variabilidade espacial e temporal do manguezal em um estuário subtropical, baía da Babitonga, sul do Brasil

Abstract

Mangroves are indicator ecosystems that respond to global changes in tropical and subtropical regions around the world. Climate changes and variations in sea level significantly influenced mangroves during the Holocene along the Brazilian coast. Here we study mangroves established near the southernmost limit of South America (28°S). Our study is based on a core obtained in the region of the Palmital channel – Baía da Babitonga, State of Santa Catarina (SC), Brazil. Sedimentary, pollen, geomorphological and vegetation analyzes allowed the paleoenvironmental reconstitution during the Late Holocene. The three facies associations found indicated a progradational succession where a tidal plain was developed on the estuary margin. During the first phase, from at least 1440 to ±1286 cal years BP, there was a sandy infratidal plain in the study area. Initially, there were no records of mangroves, but Laguncularia pollen grains were identified from ±1390 cal years BP, indicating that in the region surrounding the collection point, conditions became favorable for the development of the mangroves. After ±1286 cal years BP, the tidal flat developed reaching the present coastline, favored by the stabilization of the relative sea level. Avicennia trees were established on the tidal flat from ±1273 cal years BP. Finally, Rhizophora trees have been established during the last few decades. Probably, the mangrove succession found was favored by climatic conditions related to the increase in temperature during the late Holocene that has caused a migration from the southern limit of the mangrove to the south of the subtropical zone. Modern space-time analysis revealed a recent decrease in mangrove area of ±107 ha between 1986 (4115 Ha) and 2021 (4008 ha). The greatest loss is located in the coastal zone close to the city of Joinville (SC), mainly related to urban expansion. A slight expansion of the mangrove upstream of the channels was observed, which may be related to changes in the relative level of the modern sea and the gradual increase in minimum temperatures in southern Brazil.