Using NdSr isotopes in suspended sediments in the Abrolhos coral-reef (SW Atlantic, Brazil) to assess potential contamination from the 2015 Fundão dam collapse.

The Abrolhos bank is home of the richest coral reef system of the Southwestern Atlantic, where endemic coral species are found. It has been reported that Abrolhos' corals are under intense stress due to increasing of Marine Heat Waves during the last decades. Additionally, anthropic interventions along the adjacent coastal regions are a factor of concern since they contribute to the increase in the sediment load and to organic debris input in the reef domain. In November 2015, the collapse of the Fundão mining tailings dam resulted in the release of approximately 50 million m3 of iron oxide and quartz-rich slurry into the Doce River. Aiming at using a fingerprint of the tailings and to assess the presence of traces of the Fundão dam material from this event on the Abrolhos bank, this work presents new 87Sr/86Sr and 143Nd/144Nd isotope ratios of marine suspended sediment samples collected between 2016 and 2020 from a network of sediment traps throughout the reef and complementary suspended material at sea. In parallel, we monitored meteo-oceanographic parameters and modeled surface marine currents as an attempt to identify the sediment transport between the Doce River mouth and Abrolhos bank. The r isotopes were used as provenance proxies based on the fact that minerals and rocks tend to have specific isotopic signatures reflecting their own geological derivation. In this context, the isotopic ratios of various potential regional sources for the sedimentation in Abrolhos bank were evaluated. Our monitoring and isotopic measurements indicate that Doce River signatures are detected at Abrolhos bank, following the seasonal Doce River discharge at sea. Isotopic signature of Doce River at Abrolhos bank was also observed during the austral winter (July-August) when cold fronts migrate at the Brazilian coast with higher frequency and energy.

Chitosan-alginate beads as encapsulating agents for Yarrowia lipolytica lipase: Morphological, physico-chemical and kinetic characteristics.

Extracellular lipase from Yarrowia lipolytica was immobilized by ionotropic gelation with alginate and chitosan as encapsulating agents. Photomicrographs revealed a collapsed and heterogeneous surface of these microcapsules due to freeze-drying process. The optimum reaction temperature for the microencapsulated lipase (40 °C) was higher than for free lipase (35 °C) as well as the optimum pH (8.0 and 7.5, respectively). The study of the reaction kinetics showed that a higher maximum reaction rate (Vmax) (221.1 U/mg) for the free lipase in comparison to the immobilized form (175.3 U/mg). A protective effect of the microcapsule was detected in the storage of the enzyme at room temperature, as after 75 days 35% of activity was maintained for the microcapsules, while no activity remained after 15 days with the free enzyme. Lower values for inactivation constant (kd) and increase in half-life for immobilized lipase showed that lipase microencapsulation favored the thermostability of this enzyme.