Distribuição de espécies de angiospermas marinhas no Oceano Atlântico Ocidental

Abstract

Seagrass meadows provide valuable ecosystem services in coastal regions, being critically threatened by anthropogenic impacts and climate change. Despite their recognized importance and imminent threat, information about these ecosystems is still insufficient for several regions of the planet, making protection and conservation efforts impractical. Considering this issue, this thesis proposed to map the occurrence and distribution of marine angiosperms, seeking to understand their relationship with environmental factors at different geographic scales. This approach is explored in two chapters: the first (I) about the mapping of newly discovered seagrass meadows on the Brazilian semiarid coast, with the interpretation of their environmental and interspecific relationships, bringing contributions on the factors that act on plant biomass variations. The second (II) provides the indication of suitable areas for the occurrence of Halodule wrightii and Halophila decipiens – species registered in Chapter I – on the western Tropical Atlantic coast, through distribution models, identifying which variables influence the occurrence of these species. The results of chapter I indicated that geomorphological characteristics correspond to determining factors for variations in biomass of seagrasses, as well as interspecific interactions between cohabiting marine angiosperm species, on a regional scale. In chapter II, was verified there is still a great potential for expansion of the distribution of H. wrightii and H. decipiens on the Tropical Atlantic coast, also indicating areas where their occurrences are still potentially unknown. Although some variables strongly influence the occurrence of both species, species-specific differences – such as the difference in light requirement – can restrict or expand their occurrence as a function of depth, as in the cases of H. wrightii and H. decipiens, respectively. In a cohesive interpretation, it is possible to conclude that the occurrence and development of seagrass beds is a result not only of the set of conditions suitable for their establishment, but of the interaction with other species and that these factors at a regional scale, as well as species-specific characteristics, are determinant in the process of structuring seagrasses distribution patterns.