Abstract
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.
Highlights
Hypersaline environments are distributed throughout several regions of the world associated with tropical and arid climates [1]
This study aims to use a multiproxy approach to evaluate the trophic state and environmental quality of a hypersaline and carbonate coastal system, Vermelha Lagoon, in Rio de Janeiro State (Brazil)
Highest dissolved oxygen contents were mainly found in the southern marginal areas of the eastern and western sectors and next to the salt pans
Summary
Hypersaline environments are distributed throughout several regions of the world associated with tropical and arid climates [1]. Hypersaline coastal lagoons are commonly shallow environments strongly influenced by wind action that promotes water column homogenization [2]. The shallowness and the reduced water column further enhance the role of the bottom sediments in these ecosystems [3]. The east coast of the state of Rio de Janeiro is characterized by the presence of a large number of lagoons [4]. The occurrence of Northeast trade winds at Cabo Frio promotes the development of upwelling zone in Rio de Janeiro Coast (between Saquarema and Buzios). A climatic setting with semi-arid characteristics within a tropical environment is established in this region [5]. The hydrographic basin of Araruama lagoon is surrounded by several hypersaline lagoons, such as Pitanguinha, Pernambuco, Azul and Vermelha [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
