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.
Vermelha Lagoon is a hypersaline shallow transitional ecosystem in the state of Rio de Janeiro (Brazil). This lagoon is located in the protected area of Massambaba, between the cities of Araruama and Saquarema (Brazil), and displays two quite uncommon particularities: it exhibits carbonate sedimentation and displays the development of Holocene stromatolites. Due to both particularities, the salt industry and property speculation have been, increasingly, generating anthropic pressures on this ecosystem. This study aims to apply a multiproxy approach to evaluate the trophic state of Vermelha Lagoon based on physicochemical parameters and geochemical data for the quantification and qualification of organic matter (OM), namely total organic carbon (TOC), total sulfur (TS), total phosphorus (TP) and biopolymeric carbon (BPC), including carbohydrates (CHO), lipids (LIP) and proteins (PTN). The CHO/TOC ratio values suggest that OM supplied to the sediment is of autochthonous origin and results, essentially, from microbial activity. The cluster analyses allowed the identification of four regions in Vermelha Lagoon. The Region I included stations located in shallow areas of the eastern sector of Vermelha lagoon affected by the impact of the artificial channel of connection with Araruama Lagoon. The Region II, under the influence of salt pans, is characterized by the highest values of BPC, namely CHO promoted by microbiological activity. The Region III include stations spread through the lagoon with high values of dissolved oxygen and lower values of TP. Stromatolites and microbial mattes growth was observed in some stations of this sector. Region IV, where the highest values of TOC and TS were found, represents depocenters of organic matter, located in general in depressed areas. Results of this work evidences that the Vermelha Lagoon is an eutrophic but alkaline and well oxygenated environment (at both water column and surface sediment) where the autotrophic activity is greater than heterotrophic one. These particular conditions make this a special and rare ecosystem.
Multiproxies (benthic foraminifera, ostracods and biopolymers) approach applied to identify the environmental partitioning of the Guadiana River Estuary (Iberian Peninsula).
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