Uso de traços funcionais para acessar funcionamento ecológico em sedimento marinhos

Abstract

Studies on ecosystem functioning have gained prominence in the last decade. However, functional ecology faces significant challenges, such as the lack of studies that quantify the functions performed by organisms, clarification of the relationship between functional traits and the understanding of functioning at ecosystem scales. Despite advances in the terrestrial environment, many challenges persist in aquatic ecology, especially in tropical systems. This thesis is divided into three chapters that aim, respectively: (i) to systematize the problems associated with the functional approach in marine and coastal environments; (ii) to experimentally evaluate the relationships between functional traits of species and specific ecological functions in marine sediments, and (iii) to estimate the ecological functions performed by polychaetes throughout an estuarine ecosystem. In the first chapter, a literature review was conducted, evaluating 150 publications from the last five years. In the second chapter, laboratory experiments were conducted to quantify the bioturbation and nutrient cycling functions of seven polychaete species. In the third chapter, the results of the second chapter were coupled with distribution and abundance models of these species along the Jaguaripe River estuary to quantify and map the functions performed by these organisms at the ecosystem level. Among the main challenges identified in the literature review were the lack of complete information in databases of functional traits, the absence of a direct connection between traits and functions, and the use of subjective measures to characterize species traits. The results of the second chapter indicated that the functional traits of the species (mobility and weight) were the best predictors of the bioturbation and nutrient cycling functions, respectively. On average, an increase in the weight of polychaetes (loge g) resulted in an increase in the consumption of 0.02 of organic matter (loge g). Burrowing polychaetes bioturbated an average volume of sediment five times greater than surficial modifiers polychaetes and three times greater than tubedwelling species. Meanwhile, tube-dwelling species reached the greatest depths, penetrating up to 20 cm into the sediment. In the third chapter, we estimated that, over 96 hours, polychaetes consumed, on average, 231.4 tons of organic matter and bioturbated 1,605.8 m3 of sediment in the estuarine system. The highest estimates of functions were observed in regions of high salinity, while upstream areas showed greater functional vulnerability. The results of this thesis demonstrate that, despite the challenges in estimating ecological functions at different scales, it is possible to overcome them. However, this requires efforts directed towards experimental studies combined with long-term databases. Although this thesis also presents limitations, such as the limited number of species analyzed, we showed how investment in experiments and new methodologies can contribute to the understanding and measurement of ecosystem functioning.