2016. Ecological status evaluation of Itaipu Lagoon (Niterói) based on biochemical composition of organic matter. Journal of Sedimentary Environments, 1(3): 297-315. AbstractThe variety of approaches for assessing the trophic environmental state indicates that there is a strong need for the identification of new and possibly integrated ecological descriptors in coastal marine areas. These approaches would be able to capture relevant variables associated with the eutrophication process, and would be reliable, applicable and valid worldwide. The main objective of this study was to provide evidence that the quantity of total organic carbon (TOC), total sulfur (TS) and biopolymeric carbon (BPC) is useful proxies to evaluate the benthic trophic status in transitional marine environments. Sediment samples collected in Itaipu Lagoon, a Brazilian coastal system of the State of Rio de Janeiro, were analyzed in this study. Geochemical data, such as TOC, TS and BPC concentrations, including proteins (PTN), carbohydrates (CHO) and lipids (LIP), are combined with additional environmental parameters of the bottom water measured in in Itaipu Lagoon. The analysis of quantity and quality of organic matter (OM) allowed the identification of three distinct regions in Itaipu Lagoon: an inner and impacted zone characterized by sediment particularly enriched in TOC, with lower quality of OM most probably provided by the contaminated effluents and rivers runoff; an outer-less impacted lagoonal area with relatively low TOC content where the highest values of BPC/TOC and PTN/TOC are indicative of the presence of OM with high nutritional quality; and an intermediate area characterized by transitional features between the two previously described. The organic matter accumulation depends on the hydrodynamic conditions mostly governed by tidal currents. The quality of organic matter seems to be mainly influenced by municipal effluents, rivers inputs and mangroves contributions as well as by the autochthonous lagoonal biological productivity. Results of this work indicate that the inner zone of Itaipu Lagoon is being affected by eutrophication.

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Metabarcoding has become the workhorse of community ecology. Sequencing a taxonomically informative DNA fragment from environmental samples gives fast access to community composition across taxonomic groups, but it relies on the assumption that the number of sequences for each taxon correlates with its abundance in the sampled community. However, gene copy number varies among and within taxa, and the extent of this variability must therefore be considered when interpreting community composition data derived from environmental sequencing. Here we measured with single-cell qPCR the SSU rDNA gene copy number of 139 specimens of five species of planktonic foraminifera. We found that the average gene copy number varied between of ~4000 to ~50,000 gene copies between species, and individuals of the same species can carry between ~300 to more than 350,000 gene copies. This variability cannot be explained by differences in cell size and considering all plausible sources of bias, we conclude that this variability likely reflects dynamic genomic processes acting during the life cycle. We used the observed variability to model its impact on metabarcoding and found that the application of a correcting factor at species level may correct the derived relative abundances, provided sufficiently large populations have been sampled.

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Itaipu Lagoon is located near the mouth of Guanabara Bay and has great importance for recreation to the city of Niterói, Rio de Janeiro state, Brazil. Several studies have documented foraminiferan diversity at Guanabara Bay, but none in Itaipu Lagoon. Therefore, this study lists and provides images of foraminiferal species collected from Itaipu Lagoon. A total of 35 species belonging to 23 genera were collected, grouped in 17 families and four orders. Ammonia tepida was the species with the highest occurrence. This study represents a baseline work for future investigations.