Comprehensive bathymetry and intertidal topography of the Amazon estuary

The characterization of estuarine hydrodynamics primarily depends on knowledge of the bathymetry and topography. Here, we present the first comprehensive, high-resolution dataset of the topography and bathymetry of the Amazon River estuary, the world's largest estuary. Our product is based on an innovative approach combining spaceborne remote sensing data, an extensive and processed river depth dataset, and auxiliary data. Our goal with this mapping is to promote the database usage in studies that require this information, such as hydrodynamic modeling or geomorphological assessments. Our twofold approach considered 500 000 sounding points digitized from 19 nautical charts for bathymetry estimation, in conjunction with a state-of-the-art topographic dataset based on remote sensing, encompassing intertidal flats, riverbanks, and adjacent floodplains. Finally, our estimate can be accessed in a unified 30 m resolution regular grid referenced to the Earth Gravitational Model 2008 (EGM08), complemented both landward and seaward by land (Multi-Error-Removed Improved-Terrain digital elevation model, MERIT DEM) and ocean (General Bathymetric Chart of the Oceans version 2020, GEBCO_2020) topographic data. Extensive validation against independent and spatially distributed data, from an airborne lidar survey, from ICESat-2 altimetric satellite data, and from various in situ surveys, shows a typical vertical accuracy of 7.2 m (riverbed) and 1.2 m (non-vegetated intertidal floodplains). The dataset is available at https://doi.org/10.17632/3g6b5ynrdb.2 (Fassoni-Andrade et al., 2021).

Comprehensive bathymetry and intertidal topography of the Amazon estuary

The characterization of estuarine hydrodynamics primarily depends on the knowledge of bathymetry and topography. Here we present the first comprehensive, high-resolution dataset of the topography and bathymetry of the Amazon River estuary, the world's largest estuary. Our product is based on an innovative approach combining space-borne remote sensing data, an extensive and processed river depth dataset, and auxiliary data. Our goal with this characterization is to promote the database usage in studies that require this information, such as hydrodynamic modeling or geomorphological assessments. Our twofold approach considered 500'000 sounding points digitized from 19 nautical charts for bathymetry estimation, in conjunction with a state-of-the-art topography dataset based on remote sensing, encompassing intertidal flats, riverbanks, and adjacent floodplains. Finally, our estimate can be accessed in a unified 30 m resolution regular grid referenced to EGM08, complemented both landward and seaward with land (MERIT DEM) and ocean (GEBCO2020) topography data. Extensive validation against independent and spatially-distributed data, from an airborne LIDAR survey, from ICESat-2 altimetric satellite data, and from various in situ surveys, shows a typical accuracy of 8.4 m (river bed) and 1.2 m (non-vegetated inter-tidal floodplains). The dataset is available at http://dx.doi.org/10.17632/3g6b5ynrdb.1 (Fassoni-Andrade et al., 2021).

Forest restoration in the floodplains of the Amazon estuary subjected to intensive açaí management

The expansion and intensification of açaí management in floodplain forests of the Amazonian estuary have resulted in changes in floristic composition and in biodiversity losses, causing problems to ecosystems and endangering livelihoods of riverine communities. These transformations have prompted the need for forest restoration. The objective of this study was to identify and analyze forest recovery initiatives carried out in floodplain forests previously subjected to intensive açaí management in the Amazonian estuary. Methods included structured interviews and questionnaires. Results reveled the following restoration types: 1) area enrichment: subtype 1 - high floodplain forest (7.89%) and subtype 2 - low floodplain forest (44.75%); 2) directing natural regeneration of native species (34.21%); 3) cultivation of native species (13.15%). Results suggest that forest restoration efforts can promote sustainable production of açaí, productive diversity, ecosystem conservation and generate income for riverine families.

Scyphozoan jellyfish (Cnidaria, Medusozoa) from Amazon coast: distribution, temporal variation and length–weight relationship

Despite the importance of jellyfish in marine ecosystems, many basic biological and ecological aspects remain understudied, especially in tropical regions. Here, we report on scyphozoan jellyfish distribution and ecology to the Amazon coast for the first time, adding the records of Chrysaora lactea, Lychnorhiza lucerna and Stomolophus fritillarius. We also review the records for the three species for the whole Brazilian coastline, describe temporal variability within an Amazon estuary and length–weight relationships. The three species displayed a widespread distribution on the Brazilian coast. In the studied estuary, the species are unevenly distributed throughout the year and their presence was not clearly correlated with environmental factors examined, although L. lucerna is more common during the dry season, as indicated by multivariate and correlation analysis. The length–weight relationships were significant for both L. lucerna (R2 = 0.86, P < 0.0001) and S. fritillarius (R2 = 0.75, P < 0.0001). Jellyfish variability is still unexplained within the estuary despite our 3-year sampling. These jellyfish may be more abundant during the dry season due to the retraction of the amazon plume, but additional sampling designs and methods are needed to test this hypothesis.