Rodrigo De Freitas Lagoon Research Articles

Ciliate diversity in rodrigo de freitas lagoon (Rio de Janeiro, Brazil) from an integrative standpoint.

The Rodrigo de Freitas Lagoon is a highly eutrophic lacustrine system and has one of the longest histories of exploration and anthropic alteration in Brazil. Despite its relevance, limited studies explored the diversity of micro-eukaryotes in the lagoon. Ciliates (Alveolata, Ciliophora) are overlooked in environmental microbiology, especially in tropical and subtropical ecosystems, resulting in limited knowledge about their diversity and functional relevance in South American habitats, particularly in coastal lagoons. To fill this gap, here we investigated the diversity of ciliates in a brackish coastal lagoon in an urban area of Rio de Janeiro, Brazil, applying and comparing the performance of morphological and metabarcoding approaches. The metabarcoding analysis, based on high-throughput sequencing of the hipervariable region V4 of the 18S rRNA genes detected 37 molecular operational taxonomic units (MOTUs) assigned to Ciliophora, representing only about a half (56.9%) of the diversity detected by microscopy, which counted 65 ciliate morphotypes. The most representative classes in both approaches were Spirotrichea and Oligohymenophorea. The metabarcoding analysis revealed that 35.3% of the ciliate MOTUs had less than 97% similarity to available sequences in the NCBI database, indicating that more than one-third of these MOTUs potentially represents still not represented or undescribed ciliate species in current databases. Our findings indicate that metabarcoding techniques can significantly enhance the comprehension of ciliate diversity in tropical environments, but the scarcity of reference sequences of brackish ciliates in molecular databases represents a challenge to the taxonomic assignment of the MOTUs. This study provides new insights into the diversity of ciliates in a threatened coastal lagoon, revealing a vast array of still unknown and rare ciliate taxonomic units in tropical environments.

Do feeding responses of a non-native bivalve outperform the native one in a coastal lagoon? A possible explanation for the invasion success of the dark false mussel Mytilopsis leucophaeata.

The present study aimed to evaluate and compare feeding responses of the non-native and native bivalves, the dark false mussel Mytilopsis leucophaeata and the scorched mussel Brachidontes darwinianus, respectively, by offering different concentrations of seston from the coastal lagoon where these species coexist after dark false mussel introduction (Rodrigo de Freitas Lagoon, Rio de Janeiro-Brazil). For this purpose, independent laboratory experiments were carried out under five concentrations of seston to test the differences in clearance and ingestion rates of bivalves as a function of increasing concentrations of suspended particulate matter (SPM) on seston. In addition, from the integrated analysis of data obtained in experiments, it can be inferred about the efficiency levels of these species to remove SPM from seston and their effects on water turbidity and nutrient concentrations (total carbon, nitrogen, and phosphorus). Our hypothesis was that the non-native bivalve is more efficient to clear and ingest SPM from seston compared to the native one, which may lead to competitive advantages to the successful invasion of M. leucophaeata in coastal lagoons. Native species did not show a significant difference in clearance and ingestion rates with increasing concentrations of seston. Whereas the non-native bivalve showed a slight tendency to increase its clearance and ingestion rates with the increase in seston concentrations, evidencing its plasticity to adjust its feeding responses. The native bivalve was significantly more efficient to clear and ingest SPM at the lower seston concentration (i.e., close to natural concentrations found in the lagoon) compared to the non-native bivalve, which, on the other hand, showed a significant increase in its ingestion rates at the higher concentration tested (140 mg SPM L-1). Thus, the present results did not suggest food competition between the non-native M. leucophaeata and the native B. darwinianus in the introduced system. However, M. leucophaeata increased its feeding response with experimental increment in seston concentration, which suggests species ability to benefit from conditions of increased inputs of organic matter and higher primary production that could mediate its establishment in introduced systems.

Mais um lugar para chamar de casa: o bivalve invasor Mytilopsis leucophaeata alcança o sistema lagunar Maricá-Guarapina (Rio de Janeiro, Brasil)

Abstract Mytilopsis leucophaeata is an estuarine bivalve native from the Gulf of Mexico and Southeast USA, and it was introduced in Europe, Asia, Caribbean, South America and Northeast USA, showing massive colonization skills. In Brazil, the single invasion records of M. leucophaeata occur in the city of Rio de Janeiro, i.e., in the Rodrigo de Freitas Lagoon and in the Marapendi Lagoon. We conducted a new series of fieldworks in estuaries from the Rio de Janeiro state in order to evaluate the propagation of this invasive bivalve, aiming sites with proper salinities for the establishment of M. leucophaeata. A new record is given for the Maricá-Guarapina lagoon system, where M. leucophaeata mainly colonizes hard substrata (such as piers and rocks), reaching a mean density up to 43,375 specimens/m2; however, aggregates of M. leucophaeata were also observed in the soft substratum. Based on mitochondrial sequences, the taxonomic identification of the invasive bivalve was confirmed. The associated fauna to the agglomerates of M. leucophaeata in the lagoon system comprises amphipods, barnacles, tanaidaceans, isopods, crabs, polychaetes and snails. The expansion of M. leucophaeata requires a continuous investigation due to the great circulation of boats in the littoral of the Rio de Janeiro state and the increased chance of new introductions.

GENETIC CONNECTIVITY OF MULLETS (Mugil liza) BETWEEN RODRIGO DE FREITAS LAGOON AND A CONSERVATION UNIT IN STATE OF RIO DE JANEIRO, SOUTHEASTERN BRAZIL

We analyzed the genetic connectivity between mullets (Mugil liza) captured around the protected Natural Monument of Cagarras Islands (MoNa Cagarras) and inside Rodrigo de Freitas Lagoon, using microsatellite markers polymorphisms. Our data revealed the occurrence of 31 shared alleles (from 41 sampled), a high similarity in both allelic frequencies and genetic diversity and lack of differentiation between collection points (FST = 0.000, p > 0.05, STRUCTURE best estimative K = 1), results which, analyzed together, are strongly indicative of panmixia. We conclude that individuals collected inside the Rodrigo de Freitas Lagoon are genetically similar to those individuals collected around MoNa Cagarras. Given the importance of estuaries for the reproduction and development of individuals of M. liza, it is recommended that the Rodrigo de Freitas Lagoon to be managed in order to maintain genetic connectivity and diversity between the two ecosystems.

Benthic macrofauna associated to the invasive bivalve Mytilopsis leucophaeata (Dreissenidae) in a coastal lagoon in Rio de Janeiro, Brazil.

The invasion record for the estuarine bivalve Mytilopsis leucophaeata in Brazil is in Rio de Janeiro city, including the Rodrigo de Freitas Lagoon, where high densities of this invader were registered. This work aimed to (1) assess the composition and structure of the benthic macrofauna associated with this invader in Rodrigo de Freitas Lagoon, (2) analyze the spatiotemporal variation of richness, density and diversity of the associated benthic community, and (3) correlate changes on the density of the associated benthic species with some water quality variables and the density of M. leucophaeata. Clusters of M. leucophaeata were collected monthly (two years) in four sites. Nine taxa associated with M. leucophaeata were found; Heleobia sp. (Gastropoda) and Melita mangrovi (Amphipoda) showed the highest densities. The structure of the benthic macrofauna slightly differed among sampling sites, but not between dry and wet seasons. The water quality parameters, specific patterns of each taxon and high densities of M. leucophaeata contribute to variations in density of the associated species. Oscillations in the densities of M. leucophaeata and the native bivalve Brachidontes darwinianus suggest some agonistic relationship between them, such as a competition for space.

Perfluoroalkyl substances associations with morphometric health indices in three fish species from differentially contaminated water bodies in Southeastern Brazil

Environmental perfluoroalkyl substance (PFAS) concentrations have increased in the last decades, although their behaviour in the environment and potential deleterious effects are still unclear. In this context, the present study aimed to assess potential associations among these compounds in three fish species from differentially contaminated areas in southeastern Brazil, and morphometric indices used to assess environmental exposure effects, Fulton’s condition factor (FCF), the Hepatossomatic index (HSI) and the weight to length scaling coefficient (SC). Fish samples were collected from three differentially contaminated study areas in the state of Rio de Janeiro, Brazil, Guanabara Bay (GB), the Paraíba do Sul River (PS) and the Rodrigo de Freitas Lagoon (RFL). Silver scabbardfish ( Lepidopus caudatus ) and whitemouth croaker ( Micropogonias furnieri ) were sampled from both the PS (N=5 scabbardfish and N=9 croaker) and GB (N=10 for both species), while mullet ( Mugil liza ) were sampled from GB (N=15) and RFL (N=10). Results indicate that some of the morphometric indices seem to be directly affected by PFAS contaminant trends. Significant differences (p<0.05) among FCF were observed for mullet and croaker, while significant HSI differences (p<0.05) were observed only for croaker. The SC for each fish population varied among sampling site and fish population and did not seem to follow a fixed trend, corroborating previous assessments. A discriminant canonical analysis demonstrated higher discriminating contributions for the FCF and two PFAS, namely PFDA and PFOA. This variation is probably due to differential PFAS accumulation reflecting differences in trophic levels, although no direct associations between individual PFAS and the assessed morphometric indices were noted. PFAS, however, comprise several compounds, and each may be a different contributor to deleterious physiological effects. Further assessments are required, to better understand the potential deleterious effects of these compounds on populational fish health status. • PFAS and morphometric fish health indices (FCF, HSI, SC) associations were assessed. • FCF and HSI are directly affected by PFAS contaminant levels at the different sites. • SC was not useful in determining differential contamination levels. • Higher DCA discriminating contributions were noted for FCF and for PFDA and PFOA. • No associations between individual PFAS and FCF, HSI and SC were observed.

Using stable isotopes to discriminate anthropogenic impacts of the sedimentary organic matter pollution in the Rodrigo de Freitas Lagoon (RJ, Brazil).

Over the last decades, the Rodrigo de Freitas Lagoon (RFL), Rio de Janeiro, Brazil, has been impacted by the release of untreated domestic sewage, causing eutrophication processes with negative effects on its biota. Recently, the RFL underwent urban interventions to fulfill the demands of the 2016 Olympic Games, which included building the waist gallery and monitoring clandestine waste discharges into the underground drainage network. Organic-source tracing methods can be successfully used to characterize the organic matter transported from the urbanized areas to the RLF. The application of the elemental (C, N) and stable isotope (δ15N and δ13C) fingerprint methods in sediments from the RLF indicated a reduction in the domestic sewage inputs from 32 ± 16 to 12 ± 13% between 2015 and 2017. However, the sewage inputs continue being worrying. Our results also suggest that the main source of organic matter pollution in the lagoon comes from indiscriminate domestic sewage release from river channels. Secondary pollution sources are associated with the underground drainage network that still shows punctual and irregular releases of domestic sewage. Petroleum products, mainly from sewers, also show as possible organic pollution sources. Finally, the findings indicate that the interventions carried out in the RFL are promising. However, they were insufficient to cease the pollutant inputs and mitigate the negative impacts of eutrophication.

Technogenic deposits formed from dredged sediments deposition: toxic effects on earthworms

Dredged sediments are often disposed on land areas and can cause adverse effects on soil biota, since these materials generally may contain toxic agents. This work examines the ecotoxicological effects on earthworms exposed to technogenic deposits formed from the deposition of dredged sediments from an urban tropical lagoon. Such evaluation supports the understanding of the ecological effects derived from dredged sediments in the tropics, as well as the influence of soil properties in the toxicity. To simulate dredged sediment disposal under tropical conditions, a dredged sediment sample from the Rodrigo de Freitas Lagoon (Rio de Janeiro, RJ, Brazil) was mixed with a Gleysol (a typical organic tropical soil) to obtain the following doses: 0, 6, 12, 18, and 24%, where 0% = pure Gleysol. Acute and avoidance bioassays with Eisenia andrei were applied to these mixtures following standard protocols (ISO). Physical, chemical, and mineralogical characterization of the materials and metal determination in the test mixtures were performed to support the interpretations of ecotoxicological data. Metal concentrations in the test mixtures were generally in accordance with the limits defined by Brazilian law. Earthworm mortality was significant in doses ≥ 8% (LC50 = 7.1%), while doses ≥ 2% caused avoidance responses (EC50 = 1.7%, p < 0.05). The salinity in 8% treatment is similar to the salinity levels described by the literature that cause adverse effects on earthworms, suggesting that salinity played a key role in the toxicity. Earthworm biomass increased (p < 0.05) when the organisms were exposed to non-lethal doses, and this is probably due to water bioaccumulation related to high contents of salts. When comparing the toxicity found in this work with data obtained with other tropical soils, one could suppose that Gleysol mineralogy seems to control the bioavailability of salts and metals. The possible formation of technogenic soils (constructed soils) due to land deposition of dredged sediments may potentially compromise natural soil fauna. In this particular case, soil mineralogy, salinity, and metals played a relevant role in the toxicity to earthworms. The development of approaches that can integrate ecotoxicological, ecological, and pedological data is urgent for better understanding the damages associated with the disposal of dredged sediments in tropical lowlands areas.

Are invasive species always negative to aquatic ecosystem services? The role of dark false mussel for water quality improvement in a multi-impacted urban coastal lagoon

The dark false mussel Mytilopsis leucophaeata occurs as non-native species in Asia, Europe and South America. Despite the low population density usually found in its native range, M. leucophaeata forms dense clusters in newly invaded areas which lead to impacts on local organisms and environment. Some of the impacts of non-native species on newly colonized areas may be positive. However, despite the empirical evidences of increase in water transparency by freshwater dresseinids, the hypothesis that dark false mussel enhances the quality of brackish water has never been tested so far. Thus, the present study aimed to determine M. leucophaeata impacts on the water quality of a nutrient-enriched coastal lagoon by (1) analyzing a historical water dataset for pre- and post-invasion at Rodrigo de Freitas Lagoon (Brazil) and (2) experimentally testing dark false mussel direct effects on water quality. Historical field data evidenced significant lower phytoplankton abundance and chlorophyll a, and higher water transparency for the post-invasion period. These pattens were also supported by time-series analyses, which detected a decreasing trend for total coliforms density and an increased trend for dissolved oxygen over time. Moreover, time series indicated a gradual increase in lagoon water level with time, but none or minor changes were evidenced for floodgates operation routine, meteorological variables, and the frequency of sewage input. In microcosms, M. leucophaeata was effective to increase water transparency and decrease E. coli densities. The combination of field and laboratory data partially supported the hypothesis that M. leucophaeata invasion promoted an improvement in lagoon water quality, but increased phosphorus availability through excretion in microcosm assays. Management of dark false mussel populations seems to be a potential strategy for water quality improvement within already invaded systems where high sewage-enriched effluents are released. However, as non-native species often unbalance ecological relationships and functioning of the invaded ecosystems, new introductions of M. leucophaeata must be avoided.

Bacterial production prevails over photo- and chemosynthesis in a eutrophic tropical lagoon

Dark carbon fixation is a combination of processes performed by microorganisms to fix inorganic carbon driven the energy generated by chemical reactions. Our study quantified microbial primary and secondary production rates to evaluate the relative importance of dark carbon fixation in relation to photosynthetic rates and heterotrophic bacterial production and their contribution to the carbon cycle in a tropical eutrophic and human-impacted lagoon (Rodrigo de Freitas Lagoon, Brazil). Samples were collected daily at a fixed point to assess short-term temporal variations and at six different stations to assess spatial variability. Water samples were incubated using 14C-bicarbonate at 100% of light and in the dark to quantify photosynthesis and dark carbon fixation, respectively; and 3H-leucine incubations were performed to measure bacterial production. Environmental parameters (temperature, salinity, dissolved oxygen, dissolved organic carbon and inorganic nutrients) were measured to characterize the hydrology of the studied area, and to evaluate their influence on the microbial production rates. There were no significant changes in production rates over time or within different depths. Bacterial production rates varied significantly over space, and were correlated with nitrogen compounds, temperature, salinity and pH. However, a short rainfall event, although not strong or extreme, promoted rapid changes in the shallow water column, such as a decrease in temperature and nitrogen compounds, inducing responses to microbial production rates, such as higher rates of dark carbon fixation and bacterial production at the bottom and lower rates of photosynthesis. Heterotrophic bacterial production was significantly higher than dark and light carbon fixation, being the most important carbon-cycling process in Rodrigo de Freitas Lagoon, possibly favored by the high allochthonous organic matter and nutrient inputs. This study showed that, on average, dark carbon fixation accounted for 30% at the surface and 43% near the bottom of the total primary production and up to 10% of heterotrophic production in the water column, which may be related to the availability of ammonia and methane. We concluded that, even for this short-term temporal and spatial assessment, dark carbon fixation is relevant, although usually disregarded, and this process should be taken into account when evaluating carbon budgets, metabolic balance and ecosystem functioning in tropical coastal lagoons.

The spreading of the invasive bivalve Mytilopsis leucophaeata (Dreissenidae) into estuaries of Rio de Janeiro, Brazil.

An extensive field survey was conducted to evaluate the spreading of the invasive estuarine bivalve Mytilopsis leucophaeata into the metropolitan region of Rio de Janeiro (Brazil), in which the single invaded site so far recorded is Rodrigo de Freitas Lagoon. A novel record is made to the Marapendi coastal lagoon, where M. leucophaeata mainly colonizes mangrove roots. A reef composed of druses above the unconsolidated substratum is recorded for the first time for this species. The fauna associated to agglomerates of M. leucophaeata was composed of eight taxa: polychaetes Alitta succinea and Polydora sp., amphipods Melita mangrovi and Elasmopus sp., barnacles Amphibalanus eburneus and A. improvisus, the crab Eurypanopeus cf. dissimilis and the gastropod Heleobia spp. Based on COI sequences, the haplotype diversity of M. leucophaeata invasion in Marapendi Lagoon is high, like that previously recorded in Rodrigo de Freitas Lagoon. The expansion of M. leucophaeata demands a continuous investigation, including the knowledge of its impacts on the biota.

Influência da Salinidade na Toxicidade de Sedimentos Dragados da Lagoa Rodrigo de Freitas e Baía de Guanabara (RJ): Efeitos Tóxicos em Minhocas

The role of salinity levels in the toxicity of dredged sediments from estuarine systems, in scenario of land disposal, was investigated by using Eisenia andrei as bioindicator. Samples of ferralsol and chernosol were collected and salinized with seawater (2 and 12 g/kg of salt) and submitted to acute and avoidance bioassays with E. andrei. Data of salinity and sediment LC 50 were extracted from the literature. These data consists of results from acute bioassays with E. andrei applied to dredged sediments from Rodrigo de Freitas Lagoon and Guanabara Bay. The concentration of salt (g/kg) in soil:sediment mixture that corresponded to the LC 50 was estimated by determining salt contents in pure soils and sediments. When such concentration is close to the LC 50 obtained in laboratory using seawater, the influence of the salt in the toxicity was considered preponderant. The results revealed that concentrations of salt ≥ 3g/kg are significantly lethal to the organisms in both soil types, but toxicity levels are higher in ferralsol (LC 50 = 3,51 g/kg) than those observed in chernosol (LC 50 = 4,03 g/kg). Concentrations of salt ≥ 2g/kg were able to cause significant avoidance responses, but again the value of EC 50 in ferralsol (2,77 g/kg) were lower than that obtained in chernosol (2,99 g/kg). These observations are due to the abundance of expansive clay minerals in chernosol, with high cationic exchange capacity and that are able to reduce toxicity levels. The sediments whose salt concentrations in the sediment LC 50 (soil:sediment mixture) are close to the salt LC 50 values determined in laboratory are the APA of Guapimirim (winter), Porto of Rio (winter), Port of Niteroi (summer), Rodrigo de Freitas Lagoon (in chernosol) and the mouth of Meriti River (winter), suggesting that the concentrations of salts are sufficiently high to play a crucial role in the toxicity. Regarding the other study areas, other factors, such as the properties of the sediments, heavy metals and organic substances, may play an important role in the toxicity.

Greenhouse gas emission from a eutrophic coastal lagoon in Rio de Janeiro, Brazil

Greenhouse gases increased in concentrations over pre-industrial values by 257% for methane and 145% for carbon dioxide in 2016. Such increased levels are the main climate change drivers and may affect aquatic systems that accumulate and carry carbon to the ocean and the atmosphere. Additionally, these systems are sensitive to environmental changes since their physical, chemical and biological properties respond rapidly to changes. Therefore, this study focus on the greenhouse gases dynamic over an urban eutrophic tropical lagoon. Samplings were performed in the Rodrigo de Freitas Lagoon by covering four periods in 2016 (April, June, October and December). Mean diffusive flux was -1,466.8 mg m -2 d -1 of carbon dioxide and 113.7 mg m -2 d -1 of methane. Regarding the bubbling, fluxes were 58.28 mg m -2 d -1 for methane and negligible for carbon dioxide (mean value of 5.01 mg m -2 d -1 ). Environmental parameters such as depth, water temperature and sediment particle size were strongly related to the fluxes. In conclusion, the region is a sink of carbon dioxide and a source of methane to the atmosphere. Additionally, the rivers discharge impacts the lagoon by generating a methane hotspot emission region.

Metal pollution in surface sediments from Rodrigo de Freitas Lagoon (Rio de Janeiro, Brazil): Toxic effects on marine organisms

The Rodrigo de Freitas Lagoon (RFL - Rio de Janeiro, RJ, Brazil) is a highly polluted and eutrophic lacustrine system, which has been often used for the practice of aquatic sports, including during the 2016 Summer Olympic Games. This study proposes the evaluation of metal concentrations in surface sediments from the RFL before and after urban interventions performed for the 2016 Olympics, as well as their toxicity to the benthic amphipod Tiburonella viscana and embryos of the sea-urchin Echinometra lucunter. Metal concentrations determined in 2017 were significantly higher than those obtained in 2015 (especially Cu, Cd and Ni), suggesting that the interventions performed to fulfill the requirements of the Olympics increased metal contents in sediments. The sediments from the northern sector of the RFL were muddier, more organically enriched, exhibited higher metal concentrations and were more toxic to T. viscana when compared to the sediments collected in the southern sector. This fact is particularly important since the practice of sports, including during the 2016 Olympics, has been preferably performed in the northern sector. Metal distribution was strongly correlated with organic matter and mud contents. The toxicity to E. lucunter embryos was high for both northern and southern sediments; most of the samples led to 100% lack or abnormal embryonic development. The integration of physical, chemical and ecotoxicological data indicates that the mortality to T. viscana was correlated with metal contents, whereas the toxicity to E. lucunter was apparently related to the release of ammonia from the sediment to water column. Finally, high metal concentrations and the toxicity to aquatic organisms evidence the ecological risks to the biota from RFL.

Virulence determinants in genetically heterogeneous populations of Aeromonads recovered from an urban lagoon.

The diversity and distribution of Aeromonas spp. associated with virulence profiles from the Rodrigo de Freitas Lagoon were investigated using phylogenetic analysis of gyrB/rpoB gene sequences for speciation. The concatenated gyrB/rpoB gene sequences clustered into five species: Aeromonas punctata/caviae (n = 37), A. hydrophila (n = 10), A. dhakensis (n = 16), A. jandaei (n = 1) and A. enteropelogenes/trota (n = 3). The virulence genes (atc/aerA/hlyA/asp/amp) resulted in 19 virulence profiles, distributed heterogeneously among the five Aeromonas species. Out of the 67 isolates, 16% presented five distinct profiles carrying four virulence genes and 7% showed all genes investigated. The hemolytic genes were detected as follows: act 54% (37/67), aerA 36% (24/67), hlyA 26% (18/67) and proteolytic genes such as asp 36% (24/57) and amp in 85% (57/67) were widely distributed in lagoon sampling stations. Meanwhile, 88% (59/67) and 92% (62/67) of the isolates showed hemolytic and proteolytic activity, respectively. Our results demonstrated that concatenated sequences of the gyrB and rpoB genes showed to be an adequate approach for the Aeromonas speciation and prevalence. The high heterogeneity of virulence genes among the species resulted in several virulence profiles, as well as high percentages of hemolytic and proteolytic activity, demonstrating the necessity of further epidemiological surveys of Aeromonas species pathogenicity in an aquatic recreational lagoon.

ORGANIC MATTER COMPOSITION RELATED TO METHANE EBULLITIVE FLUX OF AN URBAN COASTAL LAGOON, SOUTHEASTERN BRAZIL

In 2016, Brazil emitted 18.25 Tg of methane. Some of these emissions occur through continental aquatic ecosystems, locations of fate and accumulation of organic and inorganic matter. Thus, the aim of this study is to evaluate the origin of organic matter in Rodrigo de Freitas Lagoon, an eutrophic, coastal and chocked lagoon in Rio de Janeiro, Brazil, through the determination of n-alkanes and sterols compounds in the upper two centimeters of sediment and compare these data with methane ebullitive flux. The concentrations of n-alkanes varied between 2.43 and 25.82 µg g-1. C29 was predominant compound in most sites, but also with important petrogenic source evidenced by the occurrence of Unresolved Complex Misture. The total concentration of sterols ranged from 2.76 to 56.01 µg g-1. β-sitostanol was the most abundant compound and coprostanol was the most relevant at the sites under influence of domestic effluents. CH4 ebullitive flux averaged 199 mg m-2 d-1 in the dry period and 9.3 mg m-2 d-1 during the wet season. We conclude that the organic matter reaching Rodrigo de Freitas Lagoon through the rivers discharge added or enriched with irregular sewage input and petroleum derivates are the main source of eutrophication and generate higher methane emissions to the atmosphere.

Ecotoxicological evaluation of dredged sediments from Rodrigo de Freitas Lagoon (Rio de Janeiro State, Brazil) using bioassays with earthworms and collembolans

The toxicity and metal bioavailability were studied in dredged sediments from Rodrigo de Freitas Lagoon (Rio de Janeiro, RJ, Brazil) using acute and avoidance tests with Eisenia andrei, and reproduction tests with Folsomia candida. The sediment was mixed with an artificial soil, and two natural soils (ferralsol and chernosol—representative Brazilian tropical soils) to obtain the following doses: 1, 3, 6, 12, 18, 24 and 30%. Total metal concentrations were determined in the sediment to support the interpretation of ecotoxicological data. Metal concentrations in the mixtures were in agreement with the threshold limits established by Brazilian law. However, significant avoidance responses were found on doses ≥ 3% and were the most sensitive endpoint. Earthworm mortality found in artificial soil mixtures (LC50 = 3.9) suggests higher toxicity levels than those obtained in ferralsol (LC50 = 7.6%) and chernosol (11.0%) treatments. Earthworm mortality, avoidance responses and collembolan reproduction levels found in ferralsol mixtures (LC50 = 9.2; avoidance EC50 = 2.3%; reproduction EC50 = 2.8%) were higher compared to chernosol treatments (LC50 = 11.0%; avoidance EC50 = 4.3%; reproduction EC50 = 4.9%). The reduction of toxicity levels in chernosol mixtures is probably due to the abundance of expansive clay minerals in chernosols with capacity of adsorbing metals and other xenobiotic substances from soil pore water, decreasing metal bioavailability. Finally, threshold limits defined by Brazilian legislation for soil quality and land disposal of dredged sediments are not sufficient to prevent noxious effects on soil fauna and should be complemented with a preliminary ecotoxicological evaluation.

Biliary and hepatic metallothionein, metals and trace elements in environmentally exposed neotropical cichlids Geophagus brasiliensis

One of the metal detoxifying mechanisms that occurs in fish is metallothionein (MT) induction and metal binding. Hepatic MT induction has been well described, but biliary MT metal detoxification has only recently been described in fish. In this scenario, metal-metal interactions have been increasingly evaluated to further understand the behavior of these contaminants regarding homeostasis and biological functions, as well as their toxic effects. Studies, however, have been mainly conducted concerning the elemental pair Se-Hg, and scarce reports are available concerning other metal pairs. Therefore, this study aimed to evaluate biliary and hepatic MT metal detoxification mechanisms in a territorial neotropical cichlid, Geophagus brasiliensis. Fish were sampled from the anthropogenically impacted estuarine Rodrigo de Freitas Lagoon, located in Southern Rio de Janeiro, and trace elements and MT were determined by inductively coupled plasma mass spectrometry (ICP-MS) and UV-Vis spectrophotometry, respectively, in fish liver and bile. MT in bile were significantly lower than in liver. Significant differences between bile and liver were observed for many trace elements, and, although most were higher in liver, Cd and Ni were significantly higher in bile, indicating efficient excretion from the body via the biliary route. A significant correlation was observed between MT and Fe in bile, and between MT in liver and Cu and Zn in bile. Molar ratio calculations demonstrated protective elements effects against Al, As, Cd, Hg, Pb and V in both bile and liver, as well as some novel interrelationships, indicating the importance of these investigations regarding the elucidation of element detoxifying mechanisms. Furthermore, investigation of other elemental associations may aid in decision-making processes regarding environmental contamination scenarios linked to public health.

Decadal shifts in macroalgae assemblages in impacted urban lagoons in Brazil

Unplanned coastal urbanization affects marine environments through losses of biodiversity and potential reductions in trophic interactions. Neotropical coastal lagoons are anthropogenically dominated ecosystems and some of the world's most threatened environments. The unplanned urbanization and long-term shifts in macroalgae assemblages were examined in Brazilian urban lagoons, evaluating their salinity and structural-functional metrics. Over 25 years, 46% of the species were lost from the Tijuca Lagoon (TL) and 26% from the Araruama Lagoon (AL), the latter a hypersaline lagoon; within only seven years, 14% of the algae taxa disappeared from the Rodrigo de Freitas Lagoon (RFL). Overall, the biomass in TL was halved, and RFL showed a reduction of 72%. These lagoons are currently dominated by opportunistic species, being classified as Ecological Status Groups (ESG) IIA and IIB. The saline lagoons (AL, TL) are now dominated by green-genera (Ulva, Cladophora and Rhizoclonium spp.), while the low-salinity lagoon (RFL) is red-algae dominated (mainly Polysiphonia subtilissima). Multivariate analyses confirmed decreases in total biomass at both TL and RFL, and identified changes in their community physiognomies over time. The Ecological Evaluation Index demonstrated that the macroalgae assemblages from these lagoons were moderately to impacted, largely due to increasing and poorly planned urban development.

Does environmental heterogeneity explain temporal β diversity of small eukaryotic phytoplankton? Example from a tropical eutrophic coastal lagoon

The temporal β diversity of small eukaryotic phytoplankton in a tropical urban coastal lagoon (Rodrigo de Freitas Lagoon, Brazil) was characterized throughout two annual cycles (2012–2103) with twice-weekly sampling. Small eukaryotic phytoplankton (<20 μm) were very abundant (above 1 × 103 and up to 6.2 × 105 cells mL−1). Small eukaryotes were also the most diverse phytoplankton group, showing high temporal variability at the species level that was represented by seven taxonomic divisions. Temporal β diversity was positively related to environmental heterogeneity on a short-time scale. Although abundance peaks of the main species were positively related to NH4 inputs, selection of species ultimately depended on the simultaneous interaction among several physical-chemical variables acting hierarchically on different temporal scales (first seasonally and then on a short-time scale). Considering the numerical importance of small size fraction phytoplankton, information relevant to the management and conservation of coastal lagoons could be incomplete if the floristic composition and temporal species turnover of pico- and nanophytoplankton species are not properly determined.