O crescimento vertical de Sargassum na área afetada pelo efluente térmico da Central Nuclear Almirante Álvaro Alberto

Abstract

The vertical growth of canopy-forming macroalgae is a fundamental component in coastal ecosystems, where these organisms play a dominant role. In algae with pseudo-perennial life cycle, such as Sargassum, where the loss of lateral branches occurs after reproductive events or environmental disturbances, the vertical growth rate becomes crucial for canopy restoration, playing a significant role in maintaining various ecosystem services. It is well understood that both natural and anthropogenic disturbances can affect the growth rate of macroalgae. In this study, we investigated the vertical growth rate of Sargassum in areas influenced by the thermal effluent from the Central Nuclear Almirante Álvaro Alberto (CNAAA), located in Saco Piraquara de Fora, Baía da Ilha Grande. We monitored the vertical thin Saco Piraquara de Fora and two outside this area, one in Saco Piraquara de Dentro and another in Saco do Sítio. We employed Generalized Additive Models to adjust the models, allowing us to assess if there are significant differences in the mean and variance of Sargassum's vertical growth between periods and sites. This comparison aimed to determine if there are differences in vertical growth between sites affected by thermal effluent compared to unaffected sites and if this trend varies with the studied period. We detected statistically significant differences in the mean vertical growth rate between the three sites located within the thermal effluent influence area and the two sites located outside this area. This pattern persisted in both evaluated periods, indicating a reduction in vertical growth at sites subjected to thermal effluent. Our findings relate the reduction in Sargassum's mean vertical growth rate to disturbances caused by the release of CNAAA's thermal effluent, suggesting the use of this descriptor for detecting impacts from increased seawater temperature.