Name: Natacha de Oliveira
Type: PhD thesis
Publication date: 25/06/2021
Advisor:

Namesort descending Role
Alex Cardoso Bastos Advisor *

Examining board:

Namesort descending Role
Alex Cardoso Bastos Advisor *
Fabian Sá Internal Alternate *
Helenice Vital External Examiner *
Jacqueline Albino Internal Alternate *
Leila de Lourdes Longo External Examiner *
RENATA CARDIA REBOUCAS External Examiner *
TEREZA CRISTINA MEDEIROS DE ARAUJO External Examiner *

Summary: Pressure on the marine environment, increasing over the years, has led to studies to better understand and thus to manage it taking into account ecological, environmental and human factors. Thus, the analysis and monitoring of coastal and oceanic marine systems, as well as spatial planning for use and conservation purposes, have become important issues for assessing impacts and providing sustainable use of the environment. Habitat mapping is based on an interdisciplinary seafloor analysis to understand which are dominant and determinant variables that control the distribution of benthic habitats and thus assist in management policies of these systems. In this sense, this work brings a multi-scalar analysis of the Espírito Santo Continental Shelf (ESCS), with the goal of identifying the habitats present in the shelf and verifying their variation for later analysis in smaller scales, as in the Marine Protection Area (MPA) Costa das Algas and later more specifically in the incised valleys presents in the MPA. At ESCS, mesophotic habitats stand out here, characterized by associated communities dependent on light ranging from 30 to 40 m depth and being able to extend to more than 150 m in tropical and subtropical regions, responsible for increasing biodiversity. This thesis combined indirect methods such as geomorphometry (Benthic Terrain Modeler) and geoacoustic sampling (multibeam echo-sounder), and direct sampling methods, these being video-imaging (Dropcams system), physical-chemical data of the water column and sedimentary cover (through the results of past works). Throughout the chapters and with the combination of the aforementioned methods it was possible to observe a wide variety of habitat classes, both in the ESCS and concentrated in the MPA Costa das Algas region and over the area of the incised valleys. For the three mode of study (macro, meso and micro scale), it was evident that morphology of the shelf derived from sea level fluctuations along with the sediment apport and carbonate production rates define the heterogeneity and the distribution pattern of the habitat. As more heterogeneous the sedimentary cover showed to be and as more varied the morphological slope, greater the potential of the areas for the development of benthic habitats and benthic diversity. The main prominent morphological features, mainly the incised valleys with their steep walls often associated with reef banks originated by carbonate bioconstructions and the rugged bottoms, are considered a legacy of marine regression and transgression. These drowned valleys represent three-dimensional structures that can preserve greater richness of mesophotic biodiversity compared to a flat bottom, being able to form more than one specific habitat on the continental shelf. Beyond the valleys, the rhodolith beds are considered important mesophotic habitats, and both play fundamental ecological functions for the maintenance of biodiversity, deserving attention and requiring management policies aimed at their protection and better management. In an area such as the MPA Costa das Algas, WHERE diverse habitats are found and which is susceptible to fishing activity (exploration and exploitation of marine organisms and algae), extraction of limestone nodules, mining activity (dredging) and oil (pipeline installation), the mapping performed here may open ways to subsequent marine spatial planning that encompasses and/ or enhances deep-sea habitats in order to protect their living resources.

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