Patos Lagoon Research Articles

MID TERM SIMULATION OF SUSPENDED SEDIMENT TRANSPORT AND BED EVOLUTION FOR THE PATOS LAGOON ESTUARY

Worldwide harbors are settled inside estuarine areas due the protection function of these environments against oceanic waves and therefore are subjected to the hydrodynamic processes that provide morphodynamic changes in sediment distribution and bed evolution. Understanding the dynamic of sediments and the bed evolution at estuaries is of crucial importance on maintenance of fairways and harbor docks. We modeled using the finite element technique 1005 days of hydro and morphodynamic of the Patos Lagoon estuary, in order to identify the critical deposition areas inside the Rio grande harbor fairway. Therefore, a hydrodynamic model, TELEMAC 3D, and a morphodynamic, Sisyphe, were applied in order to acquire the bed evolution and sediment distribution of the area using different data sources for the oceanic, atmospherical and continental boundary conditions. The results, present that clay is being deposited at deeper parts of the channel. Bed evolution results indicate siltation/erosion process where silt/clay is being deposited. Sedimentation rates were calculated based on the bed evolution results as well. The validation procedure showed good representation by the models of the physical aspects of the environment.

Two new species of Tryblionella W. SMITH (Bacillariaceae, Bacillariophyta) from a southern Brazil salt marsh

Two new species of Tryblionella are described occurring both in epiphytic and microphytobenthic communities from Patos Lagoon salt marshes, Rio Grande do Sul, southern Brazil. Tryblionella confusa can be misidentified as T. debilis, since the examination under light microscopy provides few characters, besides that, the later species shows a wide amplitude of characters in the literature interfering in the identification. On the other hand, Tryblionella ornata exhibits more distinguishable features in light microscopy observation, which are reinforced by its singular pattern of ornamentation visible under scanning electron microscopy. The species were observed in all sites and periods studied, undergoing a wide range of salinity and pH. No preference of substrate was observed.

Biochemical and molecular biomarkers in integument biopsies of free-ranging coastal bottlenose dolphins from southern Brazil

Adverse effects of exposure to persistent organic pollutants (POPs) threaten the maintenance of odontocete populations. In southern Brazil, coastal bottlenose dolphins from the Laguna Estuarine System (LES) and Patos Lagoon Estuary (PLE) were sampled using remote biopsies during the winter and summer months. Levels of bioaccumulated POPs were measured in the blubber. The activities of glutathione S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx), and superoxide dismutase (SOD) were also quantified, as were the mRNA transcript levels of aryl hydrocarbon receptor (AhR), AhR nuclear translocator (ARNT), cytochrome P450 1A1-like (CYP1A1), metallothionein 2A (MT2A), GST-π, GPx-4, GR, interleukin 1 alpha (IL-1α), and major histocompatibility complex II (MHCII) in the skin. In general, levels of POPs were similar among sites, sexes, ages and seasons. For most animals, total polychlorinated biphenyl (ΣPCBs) levels were above the threshold level have physiological effects and pose risks to cetaceans. The best-fitting generalized linear models (GLMs) found significant associations between GR, IL-1α and GPx-4 transcript levels, SOD and GST activities, and total polybrominated diphenyl ether (ΣPBDEs) and pesticide levels. GLMs and Kruskal-Wallis analyses also indicated that there were higher transcript levels for most genes and lower GST activity in the winter. These results reinforce the need to consider the influence of environmental traits on biomarker values in wildlife assessments.

Holocene Evolution of Patos Lagoon, Brazil: The Role of Antecedent Topography

Bortolin, E.; Weschenfelder, J., and Cooper, A., 2019. Holocene evolution of Patos Lagoon, Brazil: The role of antecedent topography. Journal of Coastal Research, 35(2), 357–368. Coconut Creek (Florida), ISSN 0749-0208.The Patos Lagoon in Rio Grande do Sul, Brazil, is part of the largest barrier lagoon system in the world. It is enclosed by a 400-km-long composite late Pleistocene/Holocene sandy barrier and has a single tidal inlet. The modern lagoon is shallow (average < 5 m) and is dominated by silt deposition. More than 1000 km of shallow seismic data (3.5 kHz) indicate that the lagoon is underlain by several shore-normal incised valleys separated by interfluves. Each incised valley existed as an individual estuary since its first flooding during the mid-Holocene. The infill of these valleys contains a basal fluvial unit, a central estuarine mud unit, and locally developed tidal sand bodies associated with former tidal inlets. The contemporary lagoonal sediments form a blanketing upper unit. Ultimately, the interfluves were drowned and the contemporary lagoon was formed by the coalescence of the incised valley estuarine systems in the late Holocene. This expansion of accommodation space coincided with a dramatic reduction in vertical sedimentation rates. Seismic profiling reveals the contemporary sandy spits, and their subaqueous extensions coincide with the location of former interfluves, indicating that inherited topography exerts major control over the location and development of lagoon-marginal spits.

Residence time patterns of Mirim Lagoon (Brazil) derived from two-dimensional hydrodynamic simulations

Mirim Lagoon (ML) is a large choked lagoon connected to the Patos Lagoon estuary and eventually to Mangueira Lake. Together, these water bodies form the most extensive lagoon system in South America. ML is a transboundary basin shared by Brazil and Uruguay that serves as a water reservoir, providing freshwater for public supply and agricultural activities. This work evaluated the transport patterns and residence time of ML using numerical simulations forced by time series of the tributaries’ discharge and by reanalysis of atmospheric data. The results indicate a mean residence time of 180 days, and spatial and temporal variations of up to 100 days were presented. The discharge conditions and the wind regime are the causes of such high variability on the distribution of the residence time at Mirim Lagoon. This high variability indicates that specific periods are more susceptible to be impacted by exogenous contaminants.

How Far Upstream: A Review of Estuary-Fresh Water Fish Movements in a Large Neotropical Basin

The present study comprises the first systematic record of upstream migratory limits for estuarine migratory fish species of the Patos Lagoon basin (Southern Brazil). The Sinos River sampling program included 85 sites sampled from 2004 to 2015, covering lowland stretches and headwaters. The Guaiba sampling program was performed from February 2011 to March 2013, comprising 59 independent samples. Six estuarine migratory fish species are present in upper Patos basin, covering distances in the range of 250-450 km from the Patos Lagoon inlet with the Atlantic Ocean. Parapimelodus nigribarbis comprised animals in the range of 11.3 to 18.9 cm (Median=13.3 cm), corresponding to adult individuals (Sinos: n=459; Guaiba, n=149). The species was captured almost 500 km from the Patos inlet, reaching 180 km upstream in the Sinos main channel. In the Guaiba lake, the species was captured mainly in autumn, although more abundant in Sinos River in winter and spring. Most of Micropogonias furnieri individuals (n=63) were juveniles (10.7-33.4 cm, median=14.2 cm). The species was not captured in Sinos basin. In the Guaiba Lake the species occurred predominantly in the southernmost part (downstream) and was more abundant (>10x) during the winter. Lycengraulis grossidens was captured in Sinos basin restricted to low stretches in summer/spring months (n=7). In the Guaiba Lake (n=134) the species presented widespread distribution all over the lake surface and year around, although ten times more abundant in spring. The majority of the specimens were adults (8.2-26.9cm, median=20.0 cm). Genidens genidens (n=27) was captured only in summer in the southern (downstream) part of the Guaiba Lake. Most individuals were adults (24.5-34.0 cm, median=27.8 cm). Genidens barbus (n=7) was restricted to spring-summer months and was captured only on southern (downstream) segments of the Guaiba Lake, comprising mainly large juveniles and adults (31.5 – 68.0 cm, median=37.9). Mugil liza appeared in spring in relative low abundances (n=13) but was widespread in the entire Guaiba Lake during the summer. The species was not captured in Sinos sampling program. Size profile comprise specimens in the borderline of maturity (34.3-45.5 cm, median=38.9 cm). General descriptive models for fish displacement in the basin are presented.

Numerical study of oil spill in the Franceses Bridge region, Patos Lagoon estuary

The consumption pattern of the world population is based on derivatives petroleum, which despite contributing to the improvement of the quality of life, has negative aspects, mainly in the environmental scope. The number of oil spills in water slide has increased significantly in recent years. Considering the complexity of the marine environment, the present work aims to apply a identification system of the dynamics and dispersion of oil, using the numerical modeling in the region of Franceses Bridge, near to Patos Lagoon-RS, Brazil. The study of hypothetical events of oil leakage in the region is of fundamental importance, since the Riograndense Petroleum Refinery is located inside of the Patos Lagoon estuary. A data structure of atmospheric and oceanic circulation was organized and inserted in the coupling between the hydrodynamic module Telemac-3D and the ECOS oil model, during the period between 2010 and 2013. The coupling of these models gave a good approximation to the solution of the problem, besides demanding a level of computational effort propitious to obtaining results capable of giving technical and scientific support to studies such as those of environmental impacts and contingency plans.

The influence of river discharge and wind on Patos Lagoon, Brazil, Suspended Particulate Matter

ABSTRACTEight years (2008–2015) of reflectance data from the Moderate Resolution Imaging Spectroradiometer (MODIS) – Aqua sensor are used to quantify Suspended Particulate Matter (SPM) distribution and variability in Brazil’s Patos Lagoon. After application of an atmospheric correction suitable for extremely turbid coastal water and calculation of SPM concentrations from the reflectance values using an established algorithm, the daily remote sensing data were averaged into eight-day and monthly composites. The climatological patterns show a gradient from higher concentrations in the north to lower concentration in the south, with highest concentrations in austral spring and summer and lowest in autumn and winter. Strong interannual variability shows 2009 and 2012 to have the highest SPM concentrations and 2010 and 2014 to have the lowest. Time series of SPM were then compared with the main forces to the lagoon circulation (wind and river discharge). Peaks in SPM are associated with peaks in river discharge. Maximum SPM occurred following peaks in river discharge combined with strong northeast (NE) winds, suggesting that freshwater input and direction-specific winds are the major mechanisms of sediment transport in Patos Lagoon.

Estudo numérico de vazamento de óleo utilizando dados de hidrodinâmica média do estuário da Lagoa dos Patos

A impossibilidade de eliminar riscos de acidentes envolvendo o derramamento de óleo, principalmente em zonas portuárias, ressalta a importância de estabelecer protocolos para uma rápida ação contra estes eventuais desastres. Neste estudo foram simulados sessenta cenários de eventos de derrame de óleo com diferentes condições ambientais na região portuária da cidade de Rio Grande – RS, modelados pelo sistema numérico Telemac-3D + ECOS. O período da simulação hidrodinâmica foi de 365 dias, sendo este equivalente às médias diárias calculadas entre os anos de 2003 a 2015. Os resultados para a validação da hidrodinâmica, realizada no mês de janeiro de 2011, mostraram-se satisfatórios. As simulações dos vazamentos escolhidas, ao longo dos 365 dias, foram utilizadas para a identificação das principais forçantes que controlam o movimento das partículas de óleo, assim como, o seu destino final. A tendência do deslocamento das partículas de óleo é devido a combinação dos efeitos dos ventos, correntes e descarga dos afluentes da Lagoa dos Patos. Os diferentes regimes de enchentes, vazantes e condições de ventos podem criar distintas interações nos efeitos sobre as trajetórias das partículas de óleo, podendo intensificar ou retardar a velocidade de deslocamento das partículas de óleo. Sendo assim, os resultados do estudo também podem ser utilizados para subsidiar ações em caso de acidentes que envolvam vazamentos de óleo no Super Porto.

Estudo Numérico de Derrames de Óleo com Condições de Enchente na Região do Super Porto de Rio Grande - RS

O crescente uso das áreas costeiras para fins econômicos é responsável pelo aumento da poluição por hidrocarbonetos no meio marinho. Como consequência, ocorrem os acidentes na extração, transporte e armazenamento dos combustíveis, fato que ocasiona uma intensa degradação ambiental. Devido às dificuldades de tratamento de áreas contaminadas, os impactos ambientais decorrentes destes acidentes afetam direta e indiretamente a qualidade de vida das populações inseridas nestas áreas. Neste sentido, foram simulados três cenários de eventos de derrame de óleo com diferentes condições ambientais na região portuária da cidade de Rio Grande — RS, modelados pelo modelo de vazamento de óleo ECOS, acoplado ao modelo hidrodinâmico Telemac-3D. As simulações foram utilizadas para a identificação das principais forçantes que controlam o movimento das manchas de óleo, como também, o seu destino final. Para as simulações dos derrames de óleo em eventos de enchente, pôde ser observado que o deslocamento das manchas de óleo nos primeiros instantes tem como principal forçante as correntes e, após algum tempo, a ação dos ventos, que causa o deslocamento das manchas para as margens do canal. Sendo assim, o modelo ECOS se mostrou eficaz, fornecendo os locais suscetíveis à contaminação na região costeira e nos segmentos onde ocorrem elevados Índices de Sensibilidade do Litoral. Portanto, os resultados do estudo podem servir como embasamento para ações em caso de acidentes que envolvam vazamentos de óleo na Lagoa dos Patos.

Numerical Study of Oil Spill in the Patos Lagoon Under Flood and Ebb Conditions

Facing great obstacles to eradicate environmental hazards generated by oil spills, it is crucial to establish actions against such accidents. In this context, the focus of this study is to analyze oil spills at the harbor region of Rio Grande, Rio Grande do Sul. The Easy Coupling Oil System (ECOS) model was used to model the oil spills under different environmental conditions simulated by the hydrodynamic model Telemac-3D, with the intention to identify the main forces controlling the movement of the oil slicks over a year of averaged hydrodynamic conditions from 2003 to 2015. The computational domain comprises the Patos Lagoon, the harbor area of Rio Grande and the Southern Brazilian Shelf. For the oil spill simulations, eight distinct events were defined considering both flood and ebb conditions in the estuarine region of the Patos Lagoon. The oil spill simulations showed that, in ebb conditions, the oil slick movement is mainly ruled by the currents, moving towards the outflow. After a few hours, the wind action makes the slick move towards the margins of the waterway. In flood conditions, on the other hand, the oil slick drifts to the interior of the estuary, following the dominant currents and the local winds.

Molecular markers indicate the phylogenetic identity of southern Brazilian sea asparagus: first record of Salicornia neei in Brazil

Abstract Molecular phylogenetic analyses based on ETS, ITS and atpB - rbcL spacer sequences assessed the phylogenetic status of the southern Brazil sea asparagus species of the genus Salicornia (Salicornioideae, Amaranthaceae). Accessions of Patos Lagoon estuary (32° S) were obtained from wild plants and two pure line lineages, selected from contrasting prostrate (BTH1) and decumbent (BTH2) ecomorphotypes found locally. Patos Lagoon wild plants, BTH1 and BTH2 f4 progenies showed 100% identical sequences for the atpB - rbcL and ITS spacers, only two mutations for ETS. Comparison of the sequences of these three markers with GenBank records confirmed the identity of Brazilian accessions as Salicornia neei . Maximum-likelihood phylogenetic analysis of ETS sequences indicated that the southern Brazilian accessions of Salicornia certainly are not close to any of the Salicornia ambigua accessions in GenBank, which are restricted to the northern hemisphere, nor are they related to any Salicornia fruticosa/Salicornia perennis clade accessions, which are also restricted to Eurasia. All above cited species have been wrongly applied to the southern Brazil sea asparagus.

Crane flies (Diptera, Tipuloidea) from southern Neotropical salt marshes: survey with DNA barcoding

ABSTRACT Crane flies are the most diverse group within Diptera, but they are rarely studied in coastal ecosystems. Considering the scarcity of information on the biology and ecology of this group in the Neotropics, and the sparse literature available for taxonomic identification, we developed a descriptive checklist that incorporates morphology and DNA barcoding. We also created a generic identification key for crane flies of southern Brazilian salt marshes. We sampled crane flies continuously at three areas along the Patos Lagoon salt marshes over one year. A total of 14 genera/subgenera, 6 species, and 12 morphotypes belonging to Limoniidae and Tipulidae were identified. Distribution ranges of Symplecta cana (Walker, 1848) and two Ormosia Rondani, 1856 species were expanded. mtDNA COI sequences were compared to the BOLD and NCBI databases, but were matched only at the family level. Therefore, we provided sequences to both platforms, updated to the genus level. We found low (0.00-0.03) intraspecific and high (0.11-0.25) interspecific molecular differences indicating that the mtDNA COI region is adequate for distinguishing species within the Tipuloidea. The Dicranomyia Stephens, 1829 species complex showed low genetic difference, indicating that they could be one species with high morphological plasticity. This study will serve as a basis for future research on insects of Neotropical salt marshes.

Shallow gas features and distribution in the Patos Lagoon: a coastal trap for gas-generator sediments

Aspectos e distribuição de gás raso na Lagoa dos Patos: um trape costeiro para sedimentos geradores de gás. Sedimentos gasosos são muito comuns nos ambientes costeiros em todo o mundo e suas ocorrências são claramente reveladas como anomalias acústicas por diversas ferramentas sísmicas, em diferentes escalas e resoluções. Este artigo apresenta exemplos de anomalias acústicas relacionadas ao gás, em perfis sísmicos (SBP) de alta resolução da Lagoa dos Patos, Sul do Brasil. Os ecogramas mostram anomalias acústicas devidas ao gás, as quais podem apresentar uma morfologia distinta para gás aprisionado no sedimento, percolação ou gás livre na coluna de água. As depressões topográficas pretéritas preenchidas com sedimentos gasosos são relacionadas aos antigos sistemas de drenagem, desenvolvidos na região costeira devido às oscilações do nível do mar durante o Quaternário. Assim, essas ocorrências de gás raso parecem ser controladas pela configuração paleoambiental, arranjo de preenchimento da bacia de sedimentação e condições hidrodinâmicas. Desde o estabelecimento da configuração atual, após o período de nível do mar alto do Holoceno, o interior da lagoa de Patos comporta-se como uma armadilha costeira para sedimentos finos, ricos em matéria orgânica e propícios a formação de gás, margeado por sedimentos mais grossos e sem gás.

The importance of shallow areas as nursery grounds for the recruitment of blue crab (Callinectes sapidus) juveniles in subtropical estuaries of Southern Brazil

Estuaries are extremely rich areas that act as nurseries for many species of fishes and crustaceans. This study is the first to address the juvenile distribution of ecologically significant size classes of blue crabs in estuaries from their southern region of distribution. We investigated the spatial and temporal distribution of the populations of juvenile blue crabs in Tramandaí-Armazém estuary (TAE) and Patos Lagoon estuary (PLE), southern Brazil, to determine possible areas of protection. The hypothesis that physical factors can direct the distribution of crabs was tested through correlations of the abundance of different size classes with some environmental parameters, in order to determine the concentration areas of blue crab juveniles. Four sites in each estuary were sampled with a bottom trawl for 18 months. Temporal patterns were more evident than spatial ones in the distribution of blue crabs. There were two recruitment peaks: one during the warmer months of spring and summer and another during the winter. Increased rainfall apparently delayed the first recruitment peak during summer–autumn of the second sampled year. The timing of winter recruitment may be associated with a reproductive cycle delay evidencing the existence of a delicate year-by-year balance in the recruitment. The spatial distribution of the blue crab was discrete in PLE, whereas it was more homogeneous in TAE. Salinity played an important role in the distribution of blue crabs in PLE, where recruits preferred the upper estuary embayments that offered shelter in spite of the lowest salinities. A clear salinity gradient is absent in TAE and was not correlated with the spatial distribution of blue crabs. The upper shallow areas of PLE are critical for the recruitment of the blue crabs, and therefore efforts should be made to preserve this nursery area.

Description of Two New Species of the Genus Vorticella (Ciliophora: Peritrichia) Epibionts on Pomacea canaliculata (Mollusca: Ampullariidae: Gastropoda)in Southern Brazil.

The peritrich ciliates Vorticella veloxiiforme n.sp. and Vorticella ampullaria n.sp. were found as epibionts on the ampullarid mollusk Pomacea canaliculata collected from Patos Lagoon, Rio Grande do Sul state, Brazil. The detailed morphology of both species was investigated using live and stained specimens, as well as scanning electron microscopy. Zooids of Vorticella veloxiiforme are cup shaped measuring 57 X 41 μm on average. A J-shaped macronucleus lies in the upper half of the cell. One contractile vacuole was observed in the upper part of the cell. V. ampullaria presents an elongate zooid measuring 70 X 25 µm on average. A C-shaped macronucleus lies in the middle of the cell. Two contractile vacuoles are present: one close to the peristome and the other in the lower half of the cell. The pattern of oral polykinetids was typical of the genus, with all infundibular polykinetids composed by three rows of kinetosomes each. SEM revealed a regular pattern of pores present on the zooid membrane of both species. Analyses of the 18s rDNA placed the two new species in the order Vorticellida close to described species of Vorticella.

Biology, distribution and geographic variation of loliginid squids (Mollusca: Cephalopoda) off southwestern Atlantic

The biology and ecology of southwestern Atlantic loliginid squids have been intensively researched in the last few decades, mostly off the Brazilian southern coast. However, information gathered by scientific research cruisers, either past or recent, is limited. Three species of loliginid squids – the warm-tempered Doryteuthissanpaulensis (Brakoniecki, 1984), plus the tropical D.pleii (Blainville, 1823) and Lolligunculabrevis (Blainville, 1823) – were sampled along 16 degrees of latitude on the southwestern Atlantic (22–38°S). The samples were obtained mostly from oceanographic surveys, but also included squids caught by commercial fisheries, and a few specimens from museum collections. Squid response to abiotic variables, morphological variation and circadian behaviour were surveyed in detail. Doryteuthissanpaulensis can be divided into at least six distinguishable geographical groups, which do not form a cline. In contrast, D.pleii can be divided into only two morphological groups that are very similar. Doryteuthis spp. were heterogeneously distributed on the shelf, whereas L.brevis was confined nearshore. Our data extended the southernmost distribution range of D.pleii by at least nine degrees of latitude, owing to specimens obtained at ~38°S (Mar del Plata, Argentina). Small, immature D.sanpaulensis were sampled inside the Patos Lagoon estuary (~32°S). The morphologically similar Doryteuthis spp. apparently avoid direct competition by concentrating at different depths, displaying different thermal preferences, and inverse circadian levels of activity. The information reported herein may be regarded as a “snapshot” of the ecology of sympatric squids in a marine environment that has not been deeply affected by climate change.

High bacterial activity in nutrient rich saltwater: Evidence from the uncoupling between salinity and nutrients in the Patos Lagoon estuary

In estuaries, a common pattern found is of higher bacterial activity in freshwater than in saltwater, an indication of the existence of an activity gradient. It is not clear, however, whether this arises from a natural property of saltwater bacterial communities or from metabolic constraints imposed from the natural co-variation between salinity and nutrients in estuarine systems. In this study, we managed to detect in situ higher activity levels of free-living bacteria in nutrient-rich saltwater entering the Patos Lagoon estuary. The bacterial community composition (BCC - Temporal Temperature Gradient Gel Electrophoresis) and activity (community-level physiological profiles, CLPP- Ecoplate™ - Biolog) were evaluated during two days in a transect along the estuary until the adjacent coastal region. The unexpected higher nutrient content and bacterial activity in saltwater found suggest that the bacterial activity is a primary response to nutrient availability, whereas salinity is the main factor structuring BCC in this estuary. Our results reject the idea of a natural low activity of saltwater bacteria by showing that their activity can increase in situ given that the proper conditions are met, especially in estuaries that display circulation patterns that promote the occurrence of nutrient-rich saltwater.

A first integrated modelling of a river-lagoon large-scale hydrological system for forecasting purposes

Hydrological-hydrodynamic modelling of basins, rivers and large bodies of water, such as lakes and lagoons, is usually performed by external coupling of hydrological-hydraulic models and 2D or 3D hydrodynamic models. Therefore, the river discharges into the lake are calculated by using the hydrologic model. The data is used then as an input to the hydrodynamic model. This approach allows for a detailed simulation of lake or lagoon hydrodynamics and circulation. However, when the objective is solely to simulate water levels and flooded areas, this approach may become too costly, making it difficult to establish operational systems such as those for flood forecasting. Therefore, in the present study, we propose a first integrated approach using one single hydrologic-hydraulic model, the MGB-IPH model, to simulate complex systems such as wind shear influence. This model was applied to simulate the Patos Lagoon (PL) basin located in Brazil and Uruguay countries. Results showed that it was possible to use the single model to simulate hydrographs, flooded areas and water levels in the PL basin. Results of performance indicators in the lakes and lagoons were within the range of results available in the literature. Improvements of model performance metrics were verified with the inclusion of wind effect in the flow routing algorithm, thus encouraging the use of the proposed model for the establishment of flood forecasting systems or for the simulation of other similar hydrological systems.

Salt-affected soils of the coastal plains in Rio Grande do Sul, Brazil

In Rio Grande do Sul (RS) State, Brazil, the soils are not prone to salinization due to the large amounts of rainfall, which are sufficient to leach the soluble salts. However, flooded rice crops grown in the coastal plains of RS may be affected by soil salinity, once the soils in this region are formed by marine, fluvial-lacustrine sediments. The use of water for irrigation of crops from sources connected with the Atlantic Ocean, especially Patos Lagoon, can lead to deposition of excessive amounts of sodium in the soil, especially in southern portion, by the proximity to channel linking the lagoon to the sea. This study aimed to map the occurrence of salt-affected soils in the coastal plains of RS State, Brazil. The study was performed in three regions: Internal Coastal Plain (ICP), External Coastal Plain (ECP) to Patos Lagoon and North Shore. 766 georreferenced soil samples were collected and levels of exchangeable sodium, exchangeable sodium percentage (ESP) and electrical conductivity (EC) of saturated extract (ECse) were analyzed. The resulting analytical data of the sampling points were submitted to a descriptive statistic and used to generate maps aiming to depict the continuous spatial variation of each measured variable. Most of soil samples showed indicators of low soil salinity, especially in most of the ICP and North Shore. The soils most affected are concentrated in regions overlapping the paleochannels sub-surface previously identified in the sub-surface of the ECP and in areas closer to links between sources of freshwater and sea. In the ICP, the salinity problem was restricted to only some areas due to the use of saline water from Patos Lagoon.