Mesophotic Hardground Revealed by Multidisciplinary Cruise on the Brazilian Equatorial Margin

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Jovane, Luigi ; Azevedo, Allana Q. ; Marcon, Eduardo H. ; Castro, Fernando Collo Correa e ; de Barros Neto, Halesio Milton C. ; Cavalcanti, Guarani de Hollanda ; Lima, Fabiola A. ; Waters, Linda G. ; Silva, Camila F. da ; Souza, Andre C. ; Sant'Anna, Lucy Gomes ; Fonseca, Thayse Sant'Ana ; Silva, Luis ; Merschmann, Marco A. de C. ; Dias, Gilberto P. ; Das, Prabodha ; Jonck, Celio Roberto ; Lizarraga, Rebeca G. M. ; de Freitas, Diana C. ; dos Santos, Maria R. ; Jardim, Kerly A. ; Laurentino, Izabela C. ; Sousa, Kyssia K. C. ; Pereira, Marilia C. ; Alencar, Yasmim da S. ; Costa, Nathalia M. L. ; Coelho, Tobias Rafael M. ; do Carmo, Kevin L. C. Ferrer ; Melo, Rebeca C. ; Santos, Iara Gadioli ; Martins, Lucas G. ; Ramos, Sabrina P. ; dos Santos, Marcio R. S. ; de Almeida, Matheus M. ; Pellizari, Vivian Helena ; Sumida, Paulo Y. G.

• Document type: Journal article
• Source: MINERALS; v. 14, n. 7, p. 26-pg., 2024-07-01.

Abstract

The Amapa margin, part of the Brazilian Equatorial Margin (BEM), is a key region that plays a strategic role in the global climate balance between the North and South Atlantic Ocean as it is strictly tied to equatorial heat conveyance and the fresh/salt water equilibrium with the Amazon River. We performed a new scientific expedition on the Amapa continental shelf (ACS, northern part of the Amazon continental platform) collecting sediment and using instrumental observation at an unstudied site. We show here the preliminary outcomes following the applied methodologies for investigation. Geophysical, geological, and biological surveys were carried out within the ACS to (1) perform bathymetric and sonographic mapping, high-resolution sub-surface geophysical characterization of the deep environment of the margin of the continental platform, (2) characterize the habitats and benthic communities through underwater images and biological sampling, (3) collect benthic organisms for ecological and taxonomic studies, (4) define the mineralogical and (5) elemental components of sediments from the study region, and (6) identify their provenance. The geophysical data collection included the use of bathymetry, a sub-bottom profiler, side scan sonar, bathythermograph acquisition, moving vessel profiler, and a thermosalinograph. The geological data were obtained through mineralogical, elemental, and grain size analysis. The biological investigation involved epifauna/infauna characterization, microbial analysis, and eDNA analysis. The preliminary results of the geophysical mapping, shallow seismic, and ultrasonographic surveys endorsed the identification of a hard substrate in a mesophotic environment. The preliminary geological data allowed the identification of amphibole, feldspar, biotite, as well as other minerals (e.g., calcite, quartz, goethite, ilmenite) present in the substrata of the Amapa continental shelf. Silicon, iron, calcium, and aluminum composes similar to 85% of sediments from the ACS. Sand and clay are the main fraction from these sediments. Within the sediments, Polychaeta (Annelida) dominated, followed by Crustacea (Arthropoda), and Ophiuroidea (Echinodermata). Through TowCam videos, 35 taxons with diverse epifauna were recorded, including polychaetes, hydroids, algae, gastropods, anemones, cephalopods, crustaceans, fishes, and sea stars. (AU)

• FAPESP's process: 16/24946-9 - Sea-level changes and Global Monsoon System: clues from marine cores in Brazil
• Grantee: Luigi Jovane
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants