Patos Estuary Research Articles

Pattern of mercury distribution in sediments from an irregular hydrological regime estuary

The Patos Estuary, in southern Brazil, is subject to an irregular hydrological regime and receives mercury (Hg)-contaminated effluents from the city of Rio Grande since the colonial period of southern Brazil. Aiming to investigate sulfate reduction effects over Hg geochemistry in a shallow area (SA) and a salt marsh (SM) from the Patos Estuary, four sediment cores were collected during two distinct hydrological regimes (i.e., freshwater dominated and brackish water dominated). An assessment of free dissolved sulfide (ΣS−II) concentration and pH in pore water and metals (Fe and Hg), fine grained (<63μm) and organic carbon (OC) contents in sediment allowed us to conclude that mercury distribution in SA is chiefly controlled by <63μm sediments and metal sulfide formation. Furthermore, redox conditions were relatively stable during both sampling periods. Nevertheless, bioturbation promotes oxygen penetration and subsequent acidification of pore water associated with upper sediment layers in SM, especially during the brackish water period. Most likely, such oxidizing conditions hamper sulfate reduction and, thereafter, Hg immobilization via the formation of metal sulfides. No evidence of anthropogenic contamination was found in the studied sediments.

Selenium Enrichment in Pore Water of Estuarine Sediments Subject to Salt Marsh Vegetation Bioirrigation (Patos Estuary, Southern Brazil).

Selenium (Se), iron (Fe), and free sulfides contents in pore waters were measured to study the liberation of soluble Se in suboxic conditions. The sediment core was collected in a salt marsh in Patos Lagoon estuary (southern Brazil), and it was obtained during a brackish water period, in a low intertidal stand vegetated by Spartina alterniflora. The redox potential (Eh), pH, andacid volatile sulfides (AVS) content were also investigated. Pore water results sustained the idea that S. alterniflora roots promote oxygen penetration to depths of ca. 10cm below the salt marsh surface, increasing Eh and lowering the pH in this interval. High Se concentrations (e.g., 16.9µg L-1), that are above US. EPA environmental criteria, were observed in the pore water to depths between 10 and 20cm and are associated to low AVS contents and high concentrations of free sulfides. In the first 10cm the lowering of Se contents probably happens due the low pH and biological volatilization of the metalloid.

Genetic connectivity of black drum (Pogonias courbina) stocks in the southwestern Atlantic Ocean

The delimitation of fishery stocks is an important aspect for the development and implementation of fishery stock management and sustainable use programs. Genetic analyses can provide useful information for the definition of population units, migration rates and changes in effective population sizes over long time frames. The black drum Pogonias courbina (Lacepede, 1803) is a marine fish that inhabits estuaries, bays and coastal waters of both hemispheres of the Western Atlantic, including Brazil, Uruguay and Northern Argentina. Intensely exploited at the Lagoa dos Patos Estuary in South Brazil, it is considered locally collapsed and since 2014 it is included in the National List of Endangered Fauna. Here we studied the population genetics of Pogonias courbina from South Brazil and the Argentinean and Uruguayan margins of the Rio de la Plata Estuary, using the mitochondrial DNA control region. We showed that along the study area Pogonias courbina groups present high genetic diversity, no genetic structure, and are undergoing slight expansion. These characteristics favor resilience of the population, decreasing the extinction risk of local stocks. However, the slow recovery after the black drum fisheries collapse at Lagoa dos Patos indicates that the recolonization process is slow; this is corroborated by migration estimates, in which we observe a low number of migrants between Argentina/Uruguay and South Brazil. Therefore, we suggest that the South Brazil reproductive stock, impacted by regional fisheries, can be considered a unique stock in terms of management, independent of Uruguayan and Argentinean management strategies. However, an integrated management plan should ideally be considered for these groups, since impacts and conservation efforts are likely shared between areas.

Mercury distributions in sediments of an estuary subject to anthropogenic hydrodynamic alterations (Patos Estuary, Southern Brazil).

The city of Rio Grande, located on the right bank of the Patos Estuary, has been severely contaminated by mercury (Hg) due to anthropogenic activities that chiefly began in the eighteenth century. To investigate the natural mercury distribution along the salinity gradient in the estuary, three sediment cores were collected from a region of the estuary that has experienced less anthropogenic impacts, namely its left bank. Our study demonstrates that accumulation of Hg and formation of metal sulfide minerals take place in fine grain sediment horizons within the sampled sediment cores. Mercury immobilization in these sediments occurs via binding to organic matter coatings on fine grain sediment particles, as well as by incorporation into and/or co-precipitation with iron sulfide minerals. The grain size controls over Hg accumulation and sulfide mineral formation were statistically demonstrated using principal component analysis. Different fine particulate sediment deposition patterns occurred at each sampling location, which is attributed to the consequence of hydrological changes in the estuary resulting from navigation infrastructure reforms performed over the past 200years in the local port (e.g., dredging) and its surroundings. We suggest that the port building and maintenance activities have influenced Hg distributions in the estuarine sediments.

Ability of Vibrio vulnificus isolated from fish of the Lagoa dos Patos estuary in south Brazil to form biofilms after sublethal stress and bacterial resistance to antibiotics and sanitizers

The present study aimed to investigate the presence of Vibrio vulnificus in fish captured at the Lagoa dos Patos estuary (RS, Brazil), to establish a correlation between bacterial biofilm formation and sublethal stress, and to assess the resistance of the isolates to antimicrobials and sanitizers. A total of 217 isolates characteristic of Vibrio sp. were analyzed. Isolates were identified and subsequently their ability to form biofilm, the impact of exposure to sublethal stress on their biofilm formation ability, and their resistance to antimicrobial and to sodium hypochlorite and chlorine dioxide sanitizers were evaluated. V. vulnificus was isolated from the fish Paralichthys orbignyanus and Micropogonias furnieri. The bacterial isolates examined were able to form biofilms. Biofilm formation ability of these strains was decreased or inhibited after being exposed to sublethal stress. The isolates were resistant to most antimicrobials. The sanitizer concentrations necessary to eliminate V. vulnificus were higher than those usually used in the fishing industry.

Record of Hg pollution around outset of colonization in Southern Brazil.

This study presents results of a sediment core located in Coroa de Boi Bay, a not dredged cove within Patos Estuary, Southern Brazil. The distribution of metals (Hg, Cu, Pb) and U in the sediment profile records several contamination events since pre-colonial times to present days. A joint assessment of the distribution of these parameters and the consultation to historical documents allowed us to establish causal links between concentrations anomalies in the sediments and ancient anthropogenic contamination in the area. During the industrial period, sedimentation rates in the bay ranged from 3.4 to 5.5mmyear-1. Applying a sedimentation rate previously calculated for undisturbed sediments in the Patos Estuary, we trace the beginning of Hg contamination as having started in the colonial period in Southern Brazil, soon after a Hispanic-Lusitanian conflict situation in South America. The most probable source of Hg contamination during this period was carroting technology used in fur processing.

Trophic niches and feeding relationships of shorebirds in southern Brazil

Niche theory predicts that sympatric species should differ in some ecological characteristic, to allow co-existence and reduce competition for key resources. Food is critical on wintering grounds and stopover areas for migratory species that need to accumulate reserves in order to complete their migration. Wetlands of the Rio Grande do Sul coastal plain, in southern Brazil, host several species of shorebirds with similar morphology, foraging methods and diet. When these species are in sympatry, some trophic niche overlap is expected. Diets and trophic niches of migratory and resident shorebirds were investigated during the austral summer on Torotama Island, Lagoa dos Patos Estuary, Brazil. Complementary methods were used to determine the trophic ecology of three shorebird species; diet was determined through analysis of feces and food samples, using stable isotopes of carbon and nitrogen. The local invertebrate community was sampled to determine potential prey and ascertain feeding preferences of birds. Coleoptera was the most abundant taxon in the feces of all shorebirds. Trophic niche overlap in the diets was high, with the widest trophic niche found for the buff-breasted sandpiper Calidris subruficollis. Isotopic mixing models indicated differences in the main food sources of shorebirds. The isotopic niche breadth was widest for the American golden-plover Pluvialis dominica. These species, as well as the resident southern lapwing Vanellus chilensis, consumed some prey in higher proportions over others, although they had generalist diets. Migratory species with generalist habits benefit from heterogeneous environments such as floodplains during the non-breeding season.

Selection of biochemical and physiological parameters in the croaker Micropogonias furnieri as biomarkers of chemical contamination in estuaries using a generalized additive model (GAM)

Biochemical and physiological parameters in the croaker Micropogonias furnieri were evaluated as biomarkers of chemical contaminants in estuaries. Juvenile croakers (10–20 cm total body length) were collected in summer and winter (2011 and 2012), in two sites at the Lagoa dos Patos estuary (southern Brazil). Fish were also collected in summer (2011 and 2012) in one site at the Barra do Chui estuary (southern Brazil). Tissue (gills, muscle or liver) samples were dissected and analyzed for contaminants [metals, polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs)] and selected biochemical and physiological parameters [metallothionein-like proteins (MTLP), acetylcholinesterase (AChE) activity, ethoxyresorufin-O-deethylase (EROD) activity, and lipid peroxidation (LPO)]. Additionally, water samples were collected for water chemical analyses (salinity, pH, temperature, dissolved oxygen, total alkalinity, and sulfate concentration). Data obtained were integrated and analyzed, using Principal Component Analysis (PCA) and Generalized Additive Model (GAM) approaches. Results showed that changes in concentrations of chemical contaminants and responses of biochemical and physiological parameters did not show any pattern according to the site, season and year of fish collection. However, they were influenced by fish body length and water temperature and salinity. Liver LPO and EROD activity were not responsive to PAHs. However, liver LPO was responsive to HCB, p,p-DDD, p,p-DDT and endosulfan sulfate. In turn, gill MTLP concentration, muscle AChE activity and liver EROD activity were responsive to non-essential metals (Pb, Cd and Ag). Considering that the ecotoxicological modeling approach adopted (GAM) accounted for biological, spatial and temporal variability of data associated with fish body size and site, season and year of fish collection, gill MTLP concentration, muscle AChE activity, as well as liver LPO and EROD activity can be considered as reliable biomarkers of fish exposure to chemical contaminants in estuaries.

A New and Microendemic Species ofOphiodesWagler, 1828 (Sauria: Diploglossinae) from the Lagoa dos Patos Estuary, Southern Brazil

Abstract Ophiodes Wagler, 1828, is a poorly known legless lizard genus, widely distributed across South America east of the Andes, and composed of five described species and other additional taxa that have not been formally described but are widely referred to in recent publications. After reviewing major herpetological collections in Rio Grande do Sul and conducting fieldwork for more than 2 decades in the Lagoa dos Patos Estuary, we came across a new species of Ophiodes, herein described. The new species is diagnosed from its congeners based on the combination of a dorsum with three wide, dark brown longitudinal stripes and two pairs of conspicuous light yellow stripes, one pair paravertebral and another dorsolateral; dark vertebral line absent; background coloration of sides light gray with four to five pale and narrow longitudinal stripes; ventral region uniformly light gray; hind limb extending to the posterior vent scale margin; small eyes, smaller than half of snout–ocular distance; supralabials wi...

Nickel, vanadium, and lead as indicators of sediment contamination of marina, refinery, and shipyard areas.

Metallic elements found in the aquatic environment may originate in areas where petroleum is refined and vessels are maintained and repaired. This study aims to assess contamination caused by nickel (Ni), lead (Pb), and vanadium (V) in sediment of the Lagoa dos Patos estuary (RS, Brazil) and to evaluate them as indicators of areas under the influence of petroleum products and antifouling paints. Surface sediments were collected in summer and in winter in areas of marinas, shipyards, refinery, and a control station. High Pb and V concentrations in shipyards and at the Yacht Club showed that some organisms may be affected by toxicity. High Pb results of the index of geoaccumulation (Igeo) were found at the Yacht Club and shipyards. Al, Ni, and V had similar distribution in the sediment in both seasons. Ni and V had high relation in winter at the Yacht Club and at the Santos Shipyard, thus suggesting that these elements come mainly from petroleum products. The same happened to the relations between Pb and V, as well as Pb and Ni at the Santos Shipyard. These elements are employed as useful tools as indicators to identify places with moderate to high localized anthropogenic inputs of petroleum derivatives and antifouling paints.

Growth Characteristics of an Estuarine Heterocystous Cyanobacterium

A new estuarine filamentous heterocystous cyanobacterium was isolated from intertidal sediment of the Lagoa dos Patos estuary (Brazil). The isolate may represent a new genus related to Cylindrospermopsis. While the latter is planktonic, contains gas vesicles, and is toxic, the newly isolated strain is benthic and does not contain gas vesicles. It is not known whether the new strain is toxic. It grows equally well in freshwater, brackish and full salinity growth media, in the absence of inorganic or organic combined nitrogen, with a growth rate 0.6 d-1. Nitrogenase, the enzyme complex responsible for fixing dinitrogen, was most active during the initial growth phase and its activity was not different between the different salinities tested (freshwater, brackish, and full salinity seawater). Salinity shock also did not affect nitrogenase activity. The frequency of heterocysts was high, coinciding with high nitrogenase activity during the initial growth phase, but decreased subsequently. However, the frequency of heterocysts decreased considerably more at higher salinity, while no change in nitrogenase activity occurred, indicating a higher efficiency of dinitrogen fixation. Akinete frequency was low in the initial growth phase and higher in the late growth phase. Akinete frequency was much lower at high salinity, which might indicate better growth conditions or that akinete differentiation was under the same control as heterocyst differentiation. These trends have hitherto not been reported for heterocystous cyanobacteria but they seem to be well fitted for an estuarine life style.

Microcystin Biodegradation Study Using a Lagoa Dos Patos Estuary Sediment in Southern of Brasil and a Comparative Analysis of Biodegradation with Isolated Bacteria

In the Lagoa dos Patos Estuary, southern Brazil, toxic blooms of cyanobacteria have been recorded for many years. Among the species of cyanobacteria that occur in the estuary Microcystis aeruginosa produces the toxin [D-Leu1] microcystin-LR, one of the most toxic known variants. The strain Microcystis aeruginosa RST9501 was cultivated in Cyanobacteria and Phycotoxins Lab of the Oceanography Institute of the Federal University of Rio Grande - FURG and it was used for toxin extraction and purification. Sediment samples were collected from the estuary and used in the toxin degradation experiments. The decrease of toxin concentration was checked by HPLC and the results were compared with other available data. This study revealed the decreased of toxin [D-Leu1] microcystin-LR concentration of 5µg.mL-1 after six days, and also describes a comparative analysis of the biodegradation by the sediment and with a bacterium isolated from the collected sediment samples. It was suggested that the reduction in toxin concentration is mainly due the biodegradation by the bacterial community of Lagoa dos Patos Estuary present in the sediment. This confirms the potential of this technique as a complementary tool for biotechnological processes to remove toxins in water. It was also carried out a comparative analysis of the biodegradation of the toxin with sediment and biodegradation with an isolated bacteria from this sediment.

Selenium deficiency in subtropical littoral pampas: environmental and dietary aspects.

Se deficiency has a critical effect on human health. The littoral near Patos Lagoon in the south of Brazil is composed of Quaternary sandy deposits and nutrient-deficient soils, which contribute to Se deficiency in the surrounding environment. The average concentration of Se in littoral soils is six times lower than the metalloid deficiency threshold of 0.5mgkg-1 and is close to that in countries where Keshan disease is registered. The sediments in the Patos Estuary are also notably lower in Se than near-shore marine sediments. Foodstuffs produced in the littoral pampas are characterised by extremely low Se concentrations compared with the same alimentary products reported worldwide. The total daily dietary intake of Se in the region is 24μgday-1, which is half the Estimated Average Requirement for adults. Black beans in the local diet provide over 40% of daily Se intake. Prescriptive addition of Se to prevalent products seems the most effective solution to the problem of metalloid dietary deficiency in the region. Similar environmental conditions and significant concentration of the population in the littoral zone suggest that the problem of Se deficiency probably affects a large proportion of the population along the Atlantic coast of Brazil.

Formação de biofilme por Vibrio parahaemolyticus isolados de pescados

RESUMO: O pescado é um alimento altamente perecível, possui pH próximo a neutralidade, elevada atividade de água e alto teor de nutrientes facilmente utilizáveis por micro-organismos. Vibrio parahaemolyticus pode ser encontrado em ambientes com salinidade entre 3% e 8% e tem pH ideal para multiplicação entre 7,8 e 8,6. É um patógeno que pode causar gastrenterite aguda pelo consumo de frutos do mar contaminados, crus ou mal cozidos. Mesmo os processos de tratamento de água como cloração, adição de antibióticos e filtros apresentam dificuldade em reduzir a contaminação por Vibrio, sendo suposto que este gênero bacteriano pode formar biofilmes em diferentes superfícies. O objetivo do trabalho foi verificar a capacidade de V. parahaemolyticus isolados de pescados formarem biofilme após estresse subletal. No decorrer de um ano, foram realizadas 12 coletas mensais de amostras de peixes capturados no estuário da Lagoa dos Patos, as quais foram analisadas quanto à presença de V. parahaemolyticus. Concomitantemente, foram coletadas assepticamente amostras de água do estuário para análise de sanilidade e pH. Os isolados de Vibrio foram analisados pela reação em cadeia da polimerase (PCR) para identificação da espécie pela presença dos genes toxR. Além dos isolados obtidos no presente trabalho, também foram estudadas 15 outras cepas de V. parahaemolyticus previamente isoladas em outros trabalhos. As cepas foram avaliadas quanto à capacidade de produção de biofilme em placas de microtitulação. A capacidade de produção de biofilme após as cepas serem submetidas a diferentes tipos de estresse subletal (42ºC, 20ºC, 4ºC e pH ácido) também foi testada. Dentre os 120 peixes analisados, foram isolados V. parahaemolyticus de quatro (3,33%) pescados, sendo Mugil platanus a única espécie de peixe na qual o micro-organismo foi encontrado. Das 19 cepas analisadas, 89,5% foram capazes de formar biofilme, o que parece indicar que essa capacidade tem um papel importante na sobrevivência do micro-organismo nos pescados. Dessas, 25% das cepas aumentaram a capacidade de formar biofilme. Com base nos resultados, conclui-se que peixes da espécie M. platanus do estuário da Lagoa dos Patos são hospedeiros de V. parahaemolyticus e que a quase totalidade das cepas são formadoras de biofilme. A exposição a condições subletais de estresse tem efeito distinto sobre as diferentes cepas, induzindo aumento na capacidade de formar biofilme em algumas. Este foi o primeiro estudo realizado com V. parahaemolyticus, para avaliar o efeito de fatores de estresse sobre a formação de biofilme.

The ichthyofauna of limnic systems in Quaternary deposits of extreme southern Brazil.

The Quaternary in the state of Rio Grande do Sul (RS), southern Brazil, is geologically represented by the coastal plain and was originated by successive events of Pleistocene-Holocene marine transgressions and the occurrence of alluvial deposits. This paper aimed to characterize the fish assemblage occurring in a swampy Quaternary area adjacent to Lagoa Pequena, a lacustrine system connected to the west margin of the Laguna dos Patos estuary. A checklist is also provided of the ichthyofauna so far recorded in limnic systems of Quaternary deposits in the state of Rio Grande do Sul. A total of 42 species was recorded, distributed in nine orders, 18 families and 31 genera. Characidae and Cichlidae were the most representative families, comprising 15 and 4 species respectively. A bibliographic revision associated to our sample data revealed the occurrence of 156 species in limnic systems inserted in RS Quaternary deposits (114 limnic, 15 marine/estuarine/limnic, ten marine/estuarine, nine estuarine/limnic and eight marine). Characiformes and Siluriformes are the most diverse orders, corroborating the Neotropical pattern. Seven species can be considered endemic to RS Quaternary deposits.

Vibrio parahaemolyticus e Salmonella enterica isolados de pescados capturados no estuário da Lagoa dos Patos

Microorganisms that cause human diseases can contaminate fishes in aquatic environments as well as during their capture, handling, and transport. The purpose of this study was to isolate Vibrio parahaemolyticus and Salmonella enterica from fishes captured in the Lagoa dos Patos estuary that were eviscerated and cleaned for trade. Thirteen fish landing were analyzed and 65 entire fishes and 65 cleaned fishes were studied to determine the presence of V. parahaemolyticus and S. enterica. Bacterial isolates were compared using rep-PCR. V. parahaemolyticus was isolated from one entire Micropogonias furnieri and two entire Mugil platanus, as well as from three eviscerated M. platanus. S. enterica was isolated from two eviscerated Paralichthys orbignyanus. Identical rep-PCR bands from V. parahaemolyticus were observed in entire and eviscerated fishes from the same discharge, suggesting processing failures that neither eliminated the microorganism from the raw material nor prevented cross-contamination. S. enterica was not isolated from entire fishes, presumably because contamination occurred due to hygiene and sanitary failures. Our results showed that M. furnieri and M. platanus captured in the Lagoa dos Patos estuary may host V. parahaemolyticus and that this microorganism, as with S. enterica, may also persist even after the fish is cleaned. This is the first record of the isolation of V. parahaemolyticus from M. furnieri.

Modelagem de ocorrência e densidade de juvenis de Callinectes sapidus (Decapoda, Portunidae) em dois estuários do Rio Grande do Sul, com dados zero-inflacionados

Dados de contagem de juvenis de siri-azul (Callinectes sapidus Rathbun, 1896) coletados em dois estuários do Rio Grande do Sul são objeto do presente estudo. Por se encontrarem zero-inflacionados, esses dados motivaram a formulação de modelos hierárquicos, que quantificam o efeito das covariáveis categóricas mês e local sobre a probabilidade de ocorrência e densidade dessas populações, levando em conta a detecção imperfeita. Foram também desenvolvidos modelos não-hierárquicos para comparação. Uma abordagem Bayesiana foi adotada para a estimação dos parâmetros dos modelos por simulação Monte Carlo com Cadeias de Markov (MCMC). A comparação entre modelos foi feita com o Critério de Informação da Deviância (DIC). Os modelos hierárquicos apresentaram ajustes melhores que os modelos convencionais, mitigaram o problema do excesso de zeros e permitiram analisar simultaneamente as probabilidades de ocorrência e a densidade de juvenis de siri-azul. No estuário da Lagoa dos Patos, a probabilidade de ocorrência de juvenis na Classe 2 aumenta com a distância da desembocadura, enquanto em Tramandaí os pontos intermediários apresentam as maiores probabilidades. Em ambos os estuários a ocorrência é mais provável nos meses de verão e de inverno. A densidade de juvenis da Classe 2 apresenta marcada variação em relação aos meses do ano sendo, em geral, maior no estuário de Tramandaí.

Natural occurrence of White spot syndrome virus and Infectious hypodermal and hematopoietic necrosis virus in Neohelice granulata crab

White spot syndrome virus (WSSV) and Infectious hypodermal and hematopoietic necrosis virus (IHHNV) are two infectious agents associated to economic losses in shrimp aquaculture. As virus spread occurs through vectors and hosts, this study sought to verify the presence of WSSV and IHHNV in Neohelice granulata crab from Lagoa dos Patos estuary in Brazil and nearby shrimp farms. DNA extractions were performed with phenol/chloroform protocol. Molecular diagnosis was carried out by nested PCR for WSSV and one-step PCR for IHHNV. Results showed the presence of WSSV on crabs of both Lagoa dos Patos and farms, while IHHNV was found only on crabs collected in estuary. This is the first study to report IHHNV presence in N. granulata. Moreover, as analyzed crabs had no clinical symptoms or showed in situ mortality, we suggest its use as a bioindicator for virus occurrence in aquatic environments.

Especiação química de arsênio inorgânico no estuário da Laguna dos Patos (RS, Brasil)

This study optimized and validated a method to perform chemical speciation of inorganic arsenic in water samples collected under the Monitoring Program of the Port of Rio Grande-RS in July and October 2010 from the Laguna dos Patos Estuary (RS, Brazil). The flow injection hydride generation atomic absorption spectrometry technique was employed, allowing quantification of As3+ and As5+ present in estuarine water samples. Data interpretation for results generated using the improved method for analyzing water samples collected from Laguna dos Patos Estuary was done by main components analysis.

First report of White spot syndrome virus in farmed and wild penaeid shrimp from Lagoa dos Patos estuary, southern Brazil

First report of White spot syndrome virus in farmed and wild penaeid shrimp from Lagoa dos Patos estuary, southern Brazil