Padrões espaciais, estrutura e dinâmica da comunidade meiofaunal de diferentes substratos na região litorânea do Golfão Maranhense

Abstract

The coastal zone is a constantly changing environment under the direct influence of natural processes and human actions. It consists of diverse ecosystems, such as coastal lagoons, beaches, and sandbanks, which are essential for biodiversity and provide various resources for human populations. However, rapid urban growth and disorderly human activities threaten the region, making it one of the most environmentally vulnerable areas in the world. Benthic meiofauna, composed of microscopic organisms that inhabit sediments, play a crucial role in coastal ecosystems. It plays an important role in the flow of energy in benthic systems, serving as food for other organisms, as well as being used as an indicator of environmental quality. Despite this, meiofaunal communities are poorly studied in Brazil, especially in the Northeast and along the Amazon coast. Considering the ecological importance of this component of the benthos, this study aimed to describe the spatial patterns, structure, and dynamics of meiofaunal communities in the coastal region of Maranhão (Brazil). To this end, substrates were collected from Ilha do Medo, Laguna da Jansen, Praia do Araçagy, Praia do Calhau, and Praia de São Marcos in areas of restingas, sandbanks, and tide pools. A scientometric analysis was also carried out to verify the scientific interest in studies on the influence of spatial heterogeneity on the colonization of different species (Chapter 1). The analysis revealed that macroalgae are the most frequently studied substrate, especially the invasive Sargassum muticum (Yendo) Fensholt (1955). The United States and Brazil are the most productive countries in this area of research. Multivariate analyses, especially non metric multidimensional scaling (nMDS), are commonly used. In recent years, there has been a decline in the number of studies, possibly due to the emergence of more attractive lines of research for meiobentologists. We also analyzed the role of the habitat architecture of Spartina alterniflora Loisel (1807) and Ulva lactuca Linnaeus (1753) in structuring the meiofaunal communities of the Golfão Maranhense (Chapter 2). The results indicated that structural complexity affected the richness but not the density of meiofauna. S. alterniflora, the most complex substrate, harbored a greater abundance and richness of meiofaunal taxa than U. lactuca. Finally, the spatial distribution patterns of meiofauna in three areas with different levels of disturbance were assessed (Chapter 3). Significant differences were identified in the spatial distribution of meiofauna as a function of anthropogenic disturbance. The most visually polluted area (Laguna da Jansen) showed higher density and richness than expected. The study suggests that Calhau Beach (an area classified as moderately impacted) is suffering significant environmental impacts. Among the environmental variables considered in this study, salinity, organic matter, sediment grain size, and nitrate concentration influenced meiofaunal community structure. There is still little knowledge about the dynamics of meiofaunal communities in the coastal region of Maranhão, so future studies are needed to understand the relationships between meiofauna and the substrate, as well as the structuring processes of this biological community.