Aquatic Ecology

 
Limnology
 
The limnological studies of PELD-5 (2000-2017) have allowed important scientific advances about researching the water, saline and nutrient balance of Phosphorus (P), Nitrogen (N) and mainly Carbon (C) nutrients in continental lentic aquatic ecosystems located in a coastal region of restinga ecosystem. These studies have been developed under different aspects, from assessments of inputs and outputs of nutrients, their origins, to the consequences of their natural or man-made changes to aquatic ecosystems models in current and future climate scenarios. The environments used as models are several coastal lagoons located in the Restinga de Jurubatiba National Park (PARNA Jurubatiba) and in the Imboassica lagoon, a coastal lagoon located in the urban perimeter of the city of Macaé, all located in the north of the State of Rio de Janeiro.
 
Among the main objectives and results obtained until 2017 under the theme of the effect of salinity and nutrient concentrations on the structures of aquatic communities (fish, zoobenthos, zooplankton and aquatic macrophytes), the following can be highlighted:
 
i) The observation of the replacement of sweet species by brackish and saline water species at different spatiotemporal scales, being the salt coming from natural marine intrusions (strong point contributions caused by sea hangovers and gradual contributions due to the percolation of the marine water through the sandy sediment of the sandbars) and / or man-made intrusions through the artificial openings of the sandbars.
These studies originated the works: Rocha et al., 2004; Felix et al., in development.
ii) In relation to nutrients, specifically in the Imboassica lagoon, the artificial opening of the sandbar attributed to the need to dispose of the domestic and untreated effluents from the city of Macaé and for fish replacement was pointed out as an ineffective strategy for the mitigation of pollution according to the phosphorus concentration data obtained during the study. It was concluded that due to the concentrator-diluent effect and the resuspension of nutrients deposited in the sediment when a significant reduction of water volume occurs after a bar opening event, phosphorus concentrations become larger, (about 20 years of monitoring data). In addition, they have negative consequences for biologic communities, with significant changes in species composition and diversity.
These studies allowed the development of the works: Bozelli et al., 2009; Faria et al., in development.
 
Under the thematic carbon balance in different molecular forms in the model ecosystems, it can be highlighted:
 
 
i) Studies on the dissolved organic fraction of carbon (DOC) in water through the identification of the origin, quantification, spatiotemporal variation, and DOC effect on the ecosystems used as models. The studies showed that the origin of DOC, found in the color mosaic presented by the coastal lagoons of PARNA Jurubatiba, originates from the washing of the organic matter of restinga accumulated in the terrestrial sandy soil adjacent to the lagoons and that during the rainy season, the concentrations of DOC increases significantly. It was also observed that some ecosystems have the highest values of DOC recorded in the literature so far (180mg/L). In addition, it was concluded that some lagoons can be supported by the energy coming from DOC, the trophic web being supported by the heterotrophic pathway.
These studies allowed the publication of the works: Suhett et al., 2007; Amado et al., 2008; Marotta et al., 2008; Farjalla et al., 2009a and b; Suhett et al., 2013.
(ii) Regarding other forms of carbon, a number of studies have been carried out on concentrations of methane (CH4) and carbon dioxide (CO2) gases by quantifying their temporal variability (rainy and dry periods in different flooding) and their space variability (in the aquatic compartments: open water, sediment and areas colonized by aquatic macrophytes on the banks of the lagoons) with the use of compartment sectoring techniques through remote sensing.
 
 
These studies also evaluated the contribution of the different exit and entry routes of CH4 and CO2 in the studied ecosystems, mainly through the diffusion of gases through the water column, via aquatic macrophytes and through the release of accumulated bubbles in the bed due to the high gas production in the benthic compartment. During the development of this research, it was concluded that CH4 fluxes occur mainly by bubble detachment and that CO2 fluxes occur mainly by diffusion by the water column, however, for both gases, the flux through aquatic macrophytes also presents significant results driving the carbon output through the CH4 efflux and the carbon input through the CO2 influx. It was also observed that the precipitation regime (considering the oscillation of its magnitude and interannual periodicity), acts as the main regulator of the atmospheric pressures, the areas colonized by macrophytes and their senescence, and, consequently, it can regulate the annual carbon balance. Therefore, it is believed that in distinct climatic scenarios, lagoons can change their ecological roles from source to sinks or vice versa of carbon to the atmosphere.
 
The carbon thematic also allowed the publication of a series of studies in national and international journals on the effect of community structure of aquatic macrophytes, salinity, competition for substrates and processes of bioturbation, eutrophication and herbivory on the concentrations of CH4, CO2 and on the processes of production and consumption of CH4. In addition to these publications, these data are also present in chapters of limnology books and recently in an ecosystem management book, in post-production, where it is emphasized that coastal lagoons can function as a natural laboratory for the study of carbon as a management tool in those historically impacted ecosystems because its geographical location in areas intensely explored by men.
 
 
These studies allowed the development of the works: Faria and Esteves, 2001; Furtado et al., 2002; Fonseca et al., 2004; Minello, 2004; Zink et al., 2004; Fonseca et al., 2005; Marinho et al., 2010; Laque, 2011; Suhett et al., 2011; Furlanetto et al., 2012; Belarmino et al., 2013; Gripp et al., 2013; Esteves, 2013; Fonseca et al., 2013; Petruzella et al., 2013; Marinho, et al, 2015; Marinho et al., In progress; Felix et al., In progress.
As future perspectives, studies on the effects of eutrophication and salinization on communities can be highlighted, where it is expected to generate data on the structure of the consortium of periphytic microorganisms and benthic macroinvertebrates, widely found in those lagoons and still little studied in this region, which also present an important ecosystem role in the balance of nutrients and energy and can generate more information about the spatial and temporal variability of nutrients and salts due to the structure of these communities allow diagnoses of habitat conditions. In relation to the sediment nutrients, mainly in the Imboassica lagoon, during the years of strong urbanization in Macaé due to the oil and gas economy, it is sought to estimate the nutrient concentrations in the sediment in broader vertical profiles with the sedimentation rates, which together allow us to interpret stages of nutrient accumulation over the last decades of strong transformations in the landscape. For the conclusion of the carbon balance, the aim is to introduce carbon input data from the rivers, in the lagoons that present water supply unrestricted to rainfall and outcropping of groundwater. In addition, it is sought to evaluate the intensity of the efflux and carbon influx in the aquatic macrophytes according to the nictemeral variation in their metabolism, and finally, it is sought to add more carbon input and output data to make the final model even more consistent, aiming to contemplate the long-term temporal variability.

 

Aquatic Ecology Team

 

Limnology:

 

André Megali Amado (amado@ufrnet.br)

Lattes: http://lattes.cnpq.br/4312158184208542

 

Francisco de Assis Esteves (festeves@globo.com)

Lattes: http://lattes.cnpq.br/6635523086396765

 

Marcos Paulo Figueiredo de Barros (mpaulo.bio@gmail.com)

Lattes: http://lattes.cnpq.br/6641181873729199

 

Reinaldo Luiz Bozelli (bozelli@biologia.ufrj.br)

Lattes: http://lattes.cnpq.br/4521181963290823