Estuaries are major areas of organic matter (OM) deposition, playing an important role in the global carbon cycle. The Itapicuru's river estuary (IRE) is in the North Coast of Bahia (Brazil), in na Environmental Protected Area. Although it presents preserved conditions, some environmental changes caused by human activities can be observed. This study evaluated the anthropogenic impacts importance in concentrations/sources of OM deposited in IRE. n-Alkanes and stable isotopes (δ13C and δ15N) were analyzed in a sediment core collected in the studied region. Total n-alkanes (n-C15 to n-C35), TOC and TN concentrations varied from 1,333 to 7,384 ng g-1, 0.65% to 2.51% and 0.07% to 0.13%, respectively. Values of δ13C and δ15N ranged from -28.8‰ to -24.3‰, -6.23‰ to 1.87‰, respectively. By the means of the isotopic composition and the selected n-alkanes diagnostic ratios values (Productivity aquatic index; Carbon Preference Index; Average Chain Length and Alkane index), the main OM sources for IRE were determined as C3 terrestrial plants. This area is covered by mangrove/riparian vegetation, which mainly species have this photosynthetic pathway. Temporal changes in deposited OM occurred due natural and anthropogenic processes, such urban growth in the IRE upstream region.

ABSTRACT Polynoid scale-worms have been found living as commensals with deep-water antipatharians (commonly known as black corals) in the Potiguar Basin, off Rio Grande do Norte State, Northeastern Brazil. In this paper two polychaete species and four black corals species are redescribed. Benhamipolynoe cf. antipathicola and Parahololepidella cf. greeffi, and the black coral Stylopathes adinocrada Opresko, 2006 are recorded for the Southwestern Atlantic. Benhamipolynoe cf. antipathicola was first described from off New Zealand and the Malay Archipelago, as symbiont with the black coral Stylopathes tenuispina (Silberfeld, 1909). It was later reported for the North Atlantic, off Florida, associated with Stylopathes columnaris (Duchassaing, 1870). In our study, B. cf. antipathicola was found in association with the black coral S. adinocrada. Parahololepidella cf. greeffi was first described as a free-living from shallow waters off São Tomé and Cabo Verde Islands, West Africa, and later reported as symbiont with the black coral Tanacetipathes cf. spinescens in the same location. Our data expand both the geographical distribution and the host range of this species which is reported for the first time as symbiont with Tanacetipathes barbadensis (Brook, 1889), T. tanacetum (Pourtalès, 1880) and T. thamnea (Warner, 1981) in Brazil. The aim of this study is to discuss commensal associations between two species of scale-worm polynoids and black corals found in the Southwestern Atlantic, and also reporting their global distribution. Finally, we provided an updated list of the commensal polynoids and their black coral hosts.