Modificações na orla e impactos da influência humana na macrofauna bentônica de praias arenosas na Baía da Ilha Grande (Rio de Janeiro)

Abstract

Sandy beaches are ecologically and socially complex systems of continent-ocean interaction. Invertebrates from different taxonomic groups inhabit the beaches, however, as they are environments of high socioeconomic value, the frequency of people results a series of anthropic impacts. Brazil has large extensions of coastal areas still preserved, with considerable biodiversity, which may be prone to urban plans and real estate speculation in the coming decades. Understanding how these areas are being affected by the increase in human activities and urban sprawl is critical to understanding the future impacts on diversity. Ilha Grande Bay presents a variety of sandy beaches exposed and protected from wave action, ranging from unmodified to heavily defaced beaches. The objective of this study was to understand the influence of urbanization on the coastal ecosystems of the Bay from the study of interactions between biological variables, environmental conditions, and human interventions. In chapter 1, the temporal expansion of the urban paving in the immediate surroundings of the beaches was determined and its relationship with loss or gain of beach area between 2001 and 2019 was verified. In chapter 2, the types and degrees of impact were characterized in each beach and its influences on benthic macrofauna were verified. The beaches protected from the action of waves showed a higher rate of urbanization in their surroundings and no temporal pattern was found for the increase or decrease in the beaches area. Exposed beaches showed a greater variation in the beach area range, due to the greater dynamism of the erosion-accretion processes. The greatest loss of beach area found (Dois Rios, 39%) was not related to the urbanization in the surroundings, demonstrating the importance of geographic location and oceanographic factors for the sediment budget. The highest density of organisms was verified on the most impacted beach (Anil), demonstrating that the general density isolated is not a good indicator to assess beach health. However, for beaches exposed to wave action, the density of the isopod Excironala braziliensis followed a gradient of environmental quality, which points to this species as a good indicator of environmental health of the exposed beaches evaluated. From the densities of E. braziliensis and its relationship with the descriptors of human activities, it was possible to indicate priority beaches for conservation, which can help guide future urban plans.