Spatial sedimentary distribution, seasonality and the characteristics of organic matter on Fernando de Noronha insular shelf

Author(s)

Barcellos, Roberto Lima ; Eurico de Oliveira, Liza Ellen ; Flores-Montes, Manuel de Jesus

• Document type: Journal article
• Source: Brazilian Journal of Oceanography; v. 66, n. 1, p. 26-pg., 2018-01-01.

Abstract

The present study was conducted in the Fernando de Noronha archipelago (4 degrees S/32 degrees W). The objective is the evaluation of the spatial distribution and seasonal variations in the sediments and sedimentary organic matter in the northern insular shelf of Fernando de Noronha ("Mar de Dentro"). Nineteen surface sediment samples were collected between December 2013, July 2014 and November 2014. The studied methods included analysis of the grain size, coarse fraction, morphoscopy, total organic matter content, calcium carbonate, organic carbon, total nitrogen, sedimentary phosphorus (organic, inorganic and total), elemental ratios (C/N, C/P) and stable isotopic ratios (delta 13C-delta 15N). The results allowed to infer that there is no seasonal variation in sediment distribution. Whereas, the shelf sediments present a calcareous sandy sedimentary cover (CaC03 approximate to 88.3%), predominantly of well-sorted fine sands, with low organic matter content (TOM<2.87%, TOC<4.29%, TP<0.44 mu mol/g) and are mainly of marine origin (delta C-13 approximate to -22.17%PDB). As conclusions was observed a spatial variation, where the southwestern part is dominated by gravelly and northeast part is composed for fine sand, conditioned by the bottom morphology, sediments sources and, wave action. The geochemistry showed some stations with relative enrichment in organic matter content (TOC>3.0%; TN>0.4%) of mixed origin (delta C-13= -24.5 to -23.0%PDB), which were related to anthropogenic impacts and the biotic and abiotic local processes. (AU)

• FAPESP's process: 11/50582-0 - Balance study of the carbon cycle in the coastal region and its potential ocean transportation: with emphasis on the coast of Pernambuco (Carecos)
• Grantee: Elisabete de Santis Braga da Graça Saraiva
• Support Opportunities: Research Projects - Thematic Grants