Abstract The organic matter (OM) of surface sediments (0–2 cm) from the Santos Basin was characterized by employing elemental (C, N, P), isotopic (δ 13C and δ 15N), biochemical (total carbohydrates, proteins, and lipids), and pigment (chlorophyll-a and phaeopigments) proxies, as part of the Santos Project – The Santos Basin Regional Environmental Characterization (PCR-BS) – coordinated by PETROBRAS. Samples were collected in a regional scale throughout the entire basin, including 11 isobaths from eight cross-margin transects ranging from 25 to 2,400 m water depths, and 12 additional samples obtained from the São Paulo Plateau. The aims of this study were two-fold, namely, to identify the major oceanographic and depositional processes driving OM transport and accumulation and to provide information on OM origin and availability to benthic secondary producers. The multiple employed proxies and the use of machine learning allowed to categorize distinct OM accumulation provinces displaying two major regional features: shallow sediments (< 50-m isobaths) are OM-poor (TOC < 2.0 mg g -1) but the available amount is readily hydrolysable, and mid-shelf deposits (75-m and 100-m isobaths) throughout the entire basin present muddy and OM-rich sediments (TOC ranging from 7.0 to 14.0 mg g-1) seemingly available to heterotrophs. Similarly, relatively OM-rich deposits are found at depths ranging from 700 to 1,300-m isobaths throughout the basin, but their composition and nutritional value (as suggested by biochemical indicators) are not related to mid-shelf deposits. The general overview of OM accumulation and composition provided herein validated the selected organic geochemical proxies for benthic ecology studies at the shelf and deep ocean sectors of the studied region.

Abstract A scientific cruise between November 15 and December 18, 2019 aboard R/V Vital de Oliveira collected offshore seawater samples at 59 stations between the states of Ceará and Bahia. The objective was to identify hydrocarbon levels potentially associated with the mysterious oil spill that reached the northeastern coast of Brazil. Median concentrations of aliphatic hydrocarbons (AHs, 0.79 µg L-1) and polycyclic aromatic hydrocarbons (PAHs, 5.39 ng L-1) do not indicate contamination by crude oil and are comparable to baseline levels previously found in other areas of the Brazilian continental margin. The detailed composition of both groups of hydrocarbons revealed that some samples were contaminated during sampling and/or handling on-board. The data set presented herein highlights the difficulty in tracking small oil patches spread over a huge ocean area and, more importantly, the need for improving protocols of national research vessels used to collect seawater samples for trace organic analyses.

Abstract Oil spills, intrinsically related to the petroleum production chain, represent a risk to the marine environment and a potential threat to humans through seafood consumption. We revised the NE Brazil oil spill and other accidents along the Brazilian coast, with a focus on seafood contamination, covering topics such as bioaccumulation, bioaccessibility, and risk analysis. Comprehensive knowledge of the impacts of spills helps in the interpretation of the dynamics of hydrocarbons released into the sea, contributing to actions to control their negative impacts. Currently, no legal limits have been established permanently in Brazil for PAHs in seafood edible tissues.

The aim of this research was the replacement of conventional sample extraction techniques for polycyclic aromatic hydrocarbons (PAH) in tissue samples for a reliable, fast and eco-friendly procedure. The method was developed using a pressurized solvent extraction method and assessing two different standard reference materials (fish and mussel) and freeze-dried and fortified sardine samples (Sardinella sp.). Five different extraction procedures were evaluated and the best performance comprised 1 g of lyophilized tissue, 5 g of deactivated (5%) silica, a dichloromethane:methanol (4:1 v/v) mixture, a temperature of 80 °C, three cycles, 10 min of static time and 90 s of purge time. The method selected following these tests was further validated through the analysis of nine replicates of the National Institute of Standard and Technology (NIST) reference material No. 2976, resulting in an effective recovery of 83 ± 14%. The means and uncertainties attained for each PAH were equivalent to those of the reference material, corroborating the reliability of the developed method. A shorter processing time, less use of solvents and reagents and lower extract manipulation produced an effective method aligned with green-chemistry guidelines.