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Abstract Patos Lagoon is the largest choked coastal lagoon in the world (250 km long, 40 km wide and mean depth of 5 m), with banks formed by sand and predominantly muddy bottom. The circulation is mainly driven by wind and river flow, with a minor contribution of the local microtidal regime. This lagoon is one of the most studied coastal water bodies in Brazil. The Patos Lagoon suspended particulate matter (SPM) data compendium consists of over four decades (1978–2019) of SPM data gathered from multiple research and monitoring projects. Data consist of SPM in situ samplings, remote sensing derived SPM estimates, rating curve approach for SPM estimates and SPM derived from turbidity measurements. Only measurements with a detailed description of the sampling and analysis protocols were used. The present data set offers valuable contributions as it allows the assessment of trends on the data and the short‐ and long‐term spatial and temporal variability of SPM concentrations in an area where permanent monitoring stations are not available. From these records, the SPM concentrations ranged from 0.4 g/m3 up to 1,000 g/m3. The Patos Lagoon SPM Compendium has been made publicly available at Tavora, Fernandes and Möller (2020).

Turbid coastal plumes carry sediments, nutrients, and pollutants. Satellite remote sensing is an effective tool for studying water quality parameters in these turbid plumes while covering a wide range of hydrological and meteorological conditions. However, determining boundaries of turbid coastal plumes poses a challenge. Traditionally, thresholds are the approach of choice for plume detection as they are simple to implement and offer fast processing (especially important for large datasets). However, thresholds are site-specific and need to be re-adjusted for different datasets or when meteorological and hydrodynamical conditions differ. This study compares state-of-the-art threshold approaches with a novel algorithm (PLUMES) for detecting turbid coastal plumes from satellite remote sensing, tested for Patos Lagoon, Brazil. PLUMES is a semi-supervised, and spatially explicit algorithm, and does not assume a unique plume boundary. Results show that the thresholds and PLUMES approach each provide advantages and limitations. Compared with thresholds, the PLUMES algorithm can differentiate both low or high turbidity plumes from the ambient background waters and limits detection of coastal resuspension while automatically retrieving metrics of detected plumes (e.g., area, mean intensity, core location). The study highlights the potential of the PLUMES algorithm for detecting turbid coastal plumes from satellite remote sensing products, which can have significantly positive implications for coastal management. However, PLUMES, despite its demonstrated effectiveness in this study, has not yet been applied to other study sites.

Patos Lagoon is the largest choked coastal lagoon in the world (250 km long, 40 km wide and mean depth of 5 m), with banks formed by sand and predominantly muddy bottom. The circulation is mainly driven by wind and river flow, with a minor contribution of the local microtidal regime. This lagoon is one of the most studied coastal water bodies in Brazil. The Patos Lagoon suspended particulate matter (SPM) data compendium consists of over four decades (1978–2019) of SPM data gathered from multiple research and monitoring projects. Data consist of SPM in situ samplings, remote sensing derived SPM estimates, rating curve approach for SPM estimates and SPM derived from turbidity measurements. Only measurements with a detailed description of the sampling and analysis protocols were used. The present data set offers valuable contributions as it allows the assessment of trends on the data and the short‐ and long‐term spatial and temporal variability of SPM concentrations in an area where permanent monitoring stations are not available. From these records, the SPM concentrations ranged from 0.4 g/m3 up to 1,000 g/m3. The Patos Lagoon SPM Compendium has been made publicly available at Tavora, Fernandes and Möller (2020). [ABSTRACT FROM AUTHOR]

The Patos Lagoon is located in southern Brazil and is the largest freshwater lagoon in the world; it is connected to the Atlantic Ocean by a narrow strait. Through this strait, saline water flows from the sea into the lagoon and fresh water from the lagoon into the sea. Based on long-term in situ data from sea mooring and river gauge stations, as well as wind reanalysis data, the influence of local meteorological and hydrological conditions on water exchange through this strait has been studied. It was revealed that the distinct seasonal variability of water exchange is governed mostly by the variability of seasonal river discharge, but not at all by the variability of local atmospheric circulation. Similarly, the synoptic variability of water exchange between the Patos Lagoon and Atlantic Ocean on an annual scale depends mostly on the variability of river runoff and shows little relation to the variability of synoptic wind forcing. The water exchange responds to the variability of synoptic wind forcing in 24–48 h depending on the intensity of water exchange preceding the change in atmospheric circulation. Outflow of lagoon water to the sea is typical during the high river discharge period, while inflow of seawater to the lagoon is rare, occurring under specific wind conditions. Under strong wind, blowing along the Patos Lagoon from the strait to the continent, a negative surge of lagoon water near the strait and a positive surge on the opposite side of the lagoon are formed. As a result, seawater flows into the lagoon. During low river discharge periods, seawater inflow into the lagoon is typical, while short-term outflow is induced by the increase in river discharge. [ABSTRACT FROM AUTHOR]

Continental freshwater contributions are the main long-term control on the variability of suspended particulate matter (SPM) concentrations in choked lagoons. The current work aims to assess the seasonal to interdecadal variability in SPM concentrations from Patos Lagoon tributaries, as a case study towards the understanding of tributaries contributions to coastal lagoons. Thus, an interdecadal dataset (1984–2020) was collected in the region of the tributaries of Patos Lagoon (southern Brazil), integrating Landsat series (653 scenes) and in situ measurements. SPM concentrations were estimated from the scenes using a semi-analytical multiwavelength algorithm, applied in the regions of the lower course of the tributaries. Results identified SPM concentrations variability in seasonal scales, enhanced by El Niño Southern Oscillation (ENSO) in interannual time scales, also influencing in interdecadal trends. The seasonal SPM concentration variability reached 50 g.m–3 to each tributary. Higher SPM concentration values occurred from winter to spring, enhanced during El Niño periods and frequently reaching annual means higher than 100 g.m–3. Periods from summer to autumn, however, presented lower SPM concentrations, especially during La Niña periods, when the mean annual SPM concentration remained mostly below 50 g.m–3. Seasonal and interannual (ENSO) forcings combined developed configurations of high input periods (HIP) and low input periods (LIP). During the LIP, the river plumes are limited to their tributary zone of influence and the whole lagoon has reduced SPM concentrations. During the HIP, the river plumes spread over the lagoon sub-environments, and the SPM concentrations of all tributaries reach the estuarine zone and the ocean. Thus, the mentioned natural phenomena influence the river plumes spreading, the SPM concentrations in the lagoon, and the export to the Atlantic Ocean in time scales varying from seasonal to interdecadal.

This study introduces and discusses inorganic geochemical data from Patos Lagoon, the world's largest choked coastal lagoon located in southern Brazil. Here, we characterise the sedimentary geochemical environment using different elemental ratios to assess the influence of both anthropogenic activities and the natural hydrological regime on the contemporary geochemical record. Three sediment cores collected in the freshwater domain of Patos Lagoon were analysed. Elements Al, Ca, Cr, Fe, K, Sr, Ti and V were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Strong correlations between Sr and Ca, together with the lack of correlation with detrital elements suggested that carbonate precipitation is particularly important in this system. Lithogenic elements Al, K, Fe and Ti reflected the influence of the Guaíba River on the sedimentary sequences of Patos Lagoon. The K/Al ratio was used to investigate changes in weathering patterns and Ti/Al to evaluate grain size changes. Ti/Ca provided an excellent proxy for inferring historical changes in wetter and drier conditions, and also appears to be sensitive to the influence of ENSO events. Finally, the V/Cr ratio reflected the prevailing reducing conditions of the bottom sediments. Overall, our findings show that processes of sediment weathering, transport and deposition are mostly related to natural process, and given the large size of the system, the dilution processes could play an important role in attenuating geochemical changes related to human impacts. [ABSTRACT FROM AUTHOR]

The presence of plastic microparticles (microplastics) is gradually more common in water bodies. These particles are present in products consumed daily by society for at least 50 years, as well as the wear and natural degradation of plastic residues inadequately discarded. Most of these particles find their way to the oceans and are ingested by marine animals, which may cause premature death and even accumulation in the food chain. It is extremely important to detect contamination before damages to the local ecosystem are irreversible, being this crucial information to assist implementation of policies and regulations against plastic litter and to raise awareness of the population. This work aims to verify, for the first time in the literature, the presence of microplastics in Patos Lagoon (Laranjal beach), a very important lagoon in the south of Brazil and the largest in South America, through low-cost procedures to filter water from the place to retain particles and, later, to know the composition of some particles by using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR). The results show that, in 400 L of filtered water, approximately 0.0846 g of microplastics were found, showing the pollution of the place by, at least, microparticles of low-density polyethylene (LDPE), high-density polyethylene (HDPE), which resembles the vast majority, and polytetrafluoroethylene (PFTE).

A significant portion of the threatened ichthyofauna is composed by annual fish, whose gene flow is commonly affected by large water bodies. Austrolebias minuano is an endangered species that lives in temporary wetlands of the Patos-Mirim Lagoon System, in Brazil, inhabiting both margins of the Patos Lagoon. This species has previously been target of taxonomic split, leading to the description of A. pongondo, and there are doubts about its distinction in relation to A. charrua. The objective of this study is to understand the evolutionary patterns and processes associated with the geographic distribution of A. minuano, A. charrua and A. pongondo, while assessing their taxonomic status. For this, specimens were collected along the distribution range of the three species, and sequences of the mitochondrial cyt b and CO1 and of the nuclear ENC1 gene were characterized. Phylogenetic and phylogeographic approaches showed subdivision of the dataset in four lineages: one clustering the type population of A. minuano with A. charrua, two presenting populations previously assigned to A. minuano that inhabit the Eastern margin of the Patos Lagoon and one corresponding to A. pongondo. Patterns of migration and genetic divergences support the assignment of each of these lineages as independent evolutionary units. In the chronophylogenetic reconstructions, the two lineages inhabiting the Western margin of the Patos Lagoon constituted the first to branch out whereas the eastern lineages diverged more recently. These divergences seem to have occurred before the Pleistocene Lagoon-Barrier Depositional System related to the paleogeographic evolution of the South American Coastal Plain. [ABSTRACT FROM AUTHOR]

Tryblionella is a large epipelic genus, widespread from fresh to marine waters. Most of the studies including the genus are based only in light microscopy. Few recent studies are exclusively dedicated to Tryblionella and the ultrastructure of some species is still little known. In this paper we present eleven species of Tryblionella found in epiphyton and microphytobenthos in Patos Lagoon salt marshes. All the species are described, illustrated in light and scanning electron microscopy and comments about their taxonomy, distribution and ecology are provided. Two taxa are reported for the first time in the State of Rio Grande do Sul and one in Southern Brazil. The number of species registered in this study comprises nearly a half of the number of species registered in the country. The high richness observed may be related to the dynamics of the salt marshes, which provides both the mixing of fresh and marine waters communities and the diversity of microhabitats. The great variability among the species analyzed allowed to extend the general concept of Tryblionella, adding features which were not considered in the previous characterizations of the genus. [ABSTRACT FROM AUTHOR]

In this study, we examine how the Guri catfish Genidens genidens uses estuarine and freshwater habitats along the largest South American coastal lagoon, through the chemical analysis of otoliths and microscopic analysis of gonads. Chemical composition (Sr:Ca) of otolith edges allowed distinguishing between individuals who used the estuarine or freshwater compartments of the lagoon. The analysis of core-to-edge chemical profiles of each individual otolith revealed that the population may present two different patterns of habitat use along the lagoon. The 'type 1' pattern (89.5%) includes fish who appear to have been born in estuarine waters, whereas 'type 2' (9.5%) includes those fish born in fresh water. Nevertheless, juveniles from both patterns appear to migrate to estuarine waters. The gonad analysis shows G. genidens may reproduce in fresh water, as nearly 57% of all sampled fish were found to spawn in the freshwater portion of the lagoon. Also, the otolith core of many adult fish presented freshwater signatures, thus suggesting consistent fresh water use during early life. Our findings based on otolith and gonadal analyses challenge the previous classification of G. genidens as an estuarine resident. Rather, our results allow the suggestion that this species should be placed in the 'estuarine and fresh water' guild, which includes both fish completing their life cycles within the estuary and fish who consistently use freshwater habitats. [ABSTRACT FROM AUTHOR]

In this paper we present the occupational history of the Pontal da Barra site, located within the estuary of the Patos lagoon in southern Brazil. The Pontal da Barra was occupied by a community of fishermen and earthen mound builders (Cerritos de Indios). From 2500 to 1800 BP the site was a temporary camp, became a permanent settlement between 1800 and 1200 BP, and was ultimately abandoned around 1000 BP. The occupational history is archaeologically visible in the increased architectural complexity of the mound structures and its surrounding areas, the management of soil within the mounds, and the multifunctional aspects of the monumental mounds. As part of a regional territory, the wetland of the Pontal da Barra became a meaningful place within the spatial domain of the mound builders. The site was systemically occupied for 1,500 years by agents of a long-term indigenous history. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms in marine and freshwater environments may be favored by shifts in physical water column parameters due to warming under climate change. The Patos Lagoon (PL), a subtropical coastal environment in southern Brazil, is known for recurrent blooms of Microcystis aeruginosa complex (MAC). Here, we analyze the variability of these blooms and their relation to changes in wind direction and speed, rainfall and freshwater run-off from 2000 to 2017. Also, we discuss both longer time-series of air temperature and rainfall and a review of local studies with microcystins produced by these noxious species. Since the 1980s, MAC blooms were associated to negative anomalies in annual precipitation that occur during La Niña periods and, in the last years (2001–2014), accompanied by a trend in low river discharge. MAC blooms were conspicuous from December to March, i.e., austral summer, with massive patches seen in satellite images as for 2017. We suggest that low rainfall and run-off years under NE wind-driven hydrodynamics might accumulate MAC biomass in the west margin of the PL system. In contrast, a positive, long-term trend in precipitation (from 1950 to 2016; slope = 3.9868 mm/yr, p < 0.05) should imply in high river discharge and, consequently, advection of this biomass to the adjacent coastal region. Due to the proximity to urban areas, the blooms can represent recreational and economic hazards to the region.

ABSTRACT We evaluated the incidental catch of the blue crab in artisanal fisheries through the analysis of sex ratio, catch per unit effort, net positioning, and size in which the capture probability was 50% (P50). The specimens were collected from 2011 to 2013 in the estuary of Patos Lagoon, southern Brazil. The analysis showed a higher occurrence of males. Variations in the catch per unit effort showed greatest abundance values close to the mouth of the estuary. Catch per unit effort was similar when comparing fishing seasons and net positions. P50 indicated a low selectivity of the nets since it varied between studied areas but stayed below the size at first maturity. Catches indicated a greater effort on males, since females migrated to spawn in the ocean area adjacent to the estuary during the fishing period studied. The spatial variation of the catch per unit effort showed heterogeneity in fishing catches. Thus, optimal management of the resource should consider the particularities of each area.

This study was conducted in two estuarine inlets (Saco da Mangueira and Saco do Arraial) at the Patos Lagoon estuary, southern Brazil. The changes in relative abundance and size of post-larvae and juvenile shrimp Farfantepenaeus paulensis and juvenile blue crab Callinectes sapidus were compared, considering the influence of salinity and the presence of submerged seagrass meadows. The analyses were performed using generalized linear models (GLM) for abundance variations and ANOVA for variations on the size of individuals. The pink shrimp was more abundant at Saco da Mangueira, in seagrass meadows and areas of higher salinity. The blue crab was more abundant at Saco do Arraial and in lower levels of salinity. The importance of submerged vegetation for the blue crab lies in a preference of smaller crabs of the species for the seagrass meadows. It has been shown that these species choose different habitats in the estuary, and both the salinity and the presence of submerged seagrass meadows influence the selection of habitat.

Drowning of the coast was initiated by a marine inundation after the Last Glacial Maximum (marine isotope stage (MIS) 2) and has continued during the mid-Holocene and highstand (MIS 1). Detailed analyses of two previously examined core stratigraphy and seismic profiles combined with new grain-size and detailed diatom analyses are used to study the history of the Barra Falsa paleochannel over the last 11,000 years BP and to document the peculiar deposition within the channel fill. A rapid sea-level rise was responsible for flooding the coast in 11,180-10,780, 8420-7930, 8150-7870, and 7640-7430 cal years BP, infilling a low topographic back-barrier region. High deposition rates suggest a rapid filling of the channel, which coincides with an accelerated period of sea-level rise, closely linked to the global 8.2-ka event. The morphology of the channel is recognized by facies units in the underlying strata related to one episode of cut and fill during a single cycle of base-level fall and rise. An overall transgressive sequence above the regional surface is related to marine and marine-brackish sediments, which corresponds to a seaward/central basil fill of a wave-dominated estuary. [ABSTRACT FROM AUTHOR]

Bottom trawling is one of the most harmful and widespread activities affecting benthic habitats and fauna. In this study, we analyzed the impact of shrimp trawling fisheries on the densities, assemblage structure and vertical stratification of the benthic macrofauna in shallow mudflats of the Patos Lagoon Estuary (Brazil). Experimental trawls of different intensities were performed during three shrimp fishing seasons (2015–2017), comparing macrofauna among before and after trawling, and a control zone. The changes in macrofaunal assemblages were more consistently related to natural variability than to trawling impact, being mostly influenced by sediment structure and salinity variation. The trawling impact was mainly detected in the area with higher percentages of fine sediments, with different macrofaunal responses in each month and stratum. Some non-significant decreases on total densities after trawling were observed, mainly on the superficial stratum, and signs of burial activities. The response to trawling disturbance of each species was different and it highly depended on their natural variability. Only five species showed significant variation to the trawling treatment ( Erodona mactroides , Heleobia australis, H. charruana, Heteromastus similis and Laeonereis acuta ), with temporally different responses. Decreasing densities were more related to the high impact treatment. In some seasons, decreases on the abundance of Monokalliapseudes schubarti after high impact trawls were up to 60% of the seasonal mean densities. Trawling fisheries may reduce macrobenthic densities but not their vertical stratification. The impact of trawling on key species may compromise the ecosystem function, as benthic macrofauna provide food sources for many aquatic resources. This study highlights trawling impacts in an estuarine nursery area, which should be fully considered since they may be reflected in the trophic webs. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms in marine and freshwater environments may be favored by shifts in physical water column parameters due to warming under climate change. The Patos Lagoon (PL), a subtropical coastal environment in southern Brazil, is known for recurrent blooms of Microcystis aeruginosa complex (MAC). Here, we analyze the variability of these blooms and their relation to changes in wind direction and speed, rainfall and freshwater run-off from 2000 to 2017. Also, we discuss both longer time-series of air temperature and rainfall and a review of local studies with microcystins produced by these noxious species. Since the 1980s, MAC blooms were associated to negative anomalies in annual precipitation that occur during La Niña periods and, in the last years (2001–2014), accompanied by a trend in low river discharge. MAC blooms were conspicuous from December to March, i.e., austral summer, with massive patches seen in satellite images as for 2017. We suggest that low rainfall and run-off years under NE wind-driven hydrodynamics might accumulate MAC biomass in the west margin of the PL system. In contrast, a positive, long-term trend in precipitation (from 1950 to 2016; slope = 3.9868 mm/yr, p < 0.05) should imply in high river discharge and, consequently, advection of this biomass to the adjacent coastal region. Due to the proximity to urban areas, the blooms can represent recreational and economic hazards to the region. [ABSTRACT FROM AUTHOR]

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The Patos-Mirim is the largest coastal limnological system of the world, located in southern Brazil and eastern Uruguay, which encompass over 500 km of coastline. The economical demand for the development of an international waterway brings the need for understanding the Mirim lagoon dynamics and ulterior discharge into Patos lagoon in view of establishing navigation conditions and sustainable development. In this sense, circulation and freshwater discharge dynamics were assessed by running the numerical model TELEMAC-3D for a one-year-long simulation. The model identified the wind direction and intensity as the main combined forcing modulating water circulation and transport between the northern and southern portions and conditioning the recirculation cell orientation. Predominant winds from the S-SW directions could generate adverse conditions for navigation because they would yield low water levels under northwards water transport, thus creating shallow regions for navigation. Under such conditions, the high freshwater discharge coming from the Mirim lagoon would be restricted, and the communication to the Patos lagoon would be sufficiently weakened to prevent navigation activities. Therefore, we recommend that the viability of planning and implementing an international waterway, involving the two countries (Brazil and Uruguay), must take into account wind conditions prior to setting navigation traffic and avoid economic losses.

ABSTRACT Although ariid catfishe species are known to use coastal systems during some stages of their life cycles, the energetic contribution of estuarine resources and habitat use by many species in this family are still unclear. We used stable isotope analyses to estimate the assimilation of primary carbon sources and to infer the use of estuarine and freshwater habitats by two ariid catfishes Genidens barbus (Lacepède, 1803) and Genidens genidens (Cuvier, 1829). An isotopic mixing model revealed that juveniles of both catfish species consume considerable amounts of estuarine-produced carbon sources (G. barbus: 54-87% and G. genidens: 36-84%). However, G. genidens adults rely more on freshwater-derived carbon sources (31-77%) than on estuarine sources (23-69%). These results support the hypothesis that both species occupy the estuary and assimilate organic carbon produced in this region during their early stages, but G. genidens adults consume carbon sources associated with the freshwater portion of the lagoon.

Anthropogenic impacts as environmental degradation and fisheries have been historically associated with changes in structure and dynamics of fish assemblages. A fundamental requisite to evaluate such man-induced changes on fish assemblages is the analysis of long-term time series that allow factoring out inter-annual and decadal natural variations in physical and biotic factors. Based on a standardized monthly long-term database (1997-2012) of experimental fish collections at shallow waters of estuarine and adjacent surf-zone areas of sub-tropical coastal lagoon in southern Brazil (32ºS-52ºW), we evaluated long-term trends in fish abundance and diversity and their correlates with fisheries and environmental factors. Overall species composition and species richness (S) at both estuarine (95) and surf-zone (54) were quite similar across years (similarity=52.1 ± 5.8 SD), but there was high inter-annual variability correlated with local (temperature, salinity), regional (precipitation) and global (ENSO) factors. In the estuary, species richness decreased substantially between 2002 (S=45) and 2012 (S=22), and there were marked variability in abundance across years (CPUE mean =92.3; Min=34.5; Max=163.4). A contrasting pattern was observed at the surf-zone, with lower inter-annual variation in species richness, a marked decrease in fish abundance (CPUE mean=101.9; Min=31.3; Max=221.5). Bayesian generalized additive models (GAMs) corroborate with those results and revealed a decrease in both species richness and abundance of both estuarine and adjacent surf-zone areas. Environmental conditions explained only partially the observed inter-annual and decadal variability in both estuarine and marine fish assemblages. Man-made changes associated with habitat loss and increasing fishing pressure could be responsible by some of long-term variations observed in these fish assemblages.

A better understanding of population dynamics including the identification of reproductive areas and their contribution to the maintenance of fish stocks is essential for population conservation. Dusky grouper, Epinephelus marginatus, is a broadly distributed fish species, usually found in marine rocky bottoms. It is currently listed as “endangered” by the IUCN Red List. The available information on its population in southern Brazil suggests that the neritic habitat of Carpinteiro Bank - CB is the main growth and spawning ground in the region. We investigated if the dusky groupers caught in the rocky-jetties of Rio Grande city (a littoral artificial habitat with no spawning activity) originated from the CB. We sampled 28 individuals from the littoral rocky-jetties aged between 2 and 12 years, and 44 individuals from the neritic CB aged between 2 and 40 years. Individuals from both areas had their otolith sections analyzed with LA-ICPMS (core-to-edge profiles) for 86Sr:43Ca, 138Ba:43Ca ratios. The otolith core (natal origin) and edge (time shortly before capture) from individuals of the same age class showed no difference between the two sites. Individual profiles of 138Ba:43Ca ratios of fish from the littoral zone indicated, for the first time, that some juveniles of dusky grouper enter the Patos lagoon and remain within the estuarine environment between the first and second years of life. This interpretation of otolith chemical data is supported by the marked differences in salinity between the littoral and estuarine sites in these studies areas, and by the marked differences in otolith 138Ba:43Ca of other fish species analyzed along the salinity gradient in the Patos Lagoon estuary. The identification of differential juvenile habitat use patterns is crucial for the establishment and implementation of management and conservation strategies to safeguard this endangered species.

In Rio Grande do Sul State, there are four marine shrimp (Litopenaeus vannamei) farms in the municipal districts of São José do Norte and Rio Grande, and other four with previous license for operation. Thus, the present study aimed to identify and characterize areas for marine shrimp farming located in the Southern portion of the Patos Lagoon estuary (32º00'S 52º00'W) by employing the analysis of satellite remote sensing (Landsat TM and ETM+/Google Earth), airborne remote sensing (35mm system ADAR 1000), terrestrial remote sensing (RICOH 500SE), and field expeditions, integrating data in a Geographical Information System (IDRISI Andes). As a result, the enterprises were built on coastal fields or in obliterated dune areas, which are favorable for cultivation. The proximity of possible consuming markets and local labor, relatively good access roads and local technical support also favor the projects. However, there must be caution in terms of changes in the original projects, which could cause environmental impacts and noncompliance of environmental norms, such as the occupation of salt marsh areas. Based on the obtained information, instruments can be created to help inherent legal decision-making to manage the activity for futures enterprises.No estado do Rio Grande do Sul existem quatro fazendas produtoras de camarões (Litopenaeus vannamei) marinhos nos municípios de São José do Norte e Rio Grande, e outras quatro fazendas já possuem licença prévia. Assim, o presente estudo propôs identificar e caracterizar as áreas destinadas a cultivos de camarões marinhos localizadas na porção sul do estuário da lagoa dos Patos (32º00'S 52º00'W), empregando análises de sensoriamento remoto orbital (ETM+/Landsat, Google Earth), aéreo (35mm/sistema ADAR 1000), terrestre (RICOH 500SE) e de saídas de campo, integrando os dados num Sistema de Informação Geográfica (IDRISI Andes). Resultados apontaram que os empreendimentos foram construídos sobre campos litorâneos ou em regiões de dunas obliteradas, regiões estas propícias para o cultivo. A proximidade dos possíveis mercados consumidores e mão de obra local, estradas de acesso relativamente boas e suporte técnico local também favorecem os projetos. No entanto, deve haver cautela em termos de mudanças nos projetos originais, o que poderia causar impactos ambientais e descumprimento das normas ambientais, tais como a ocupação de áreas de marismas. A partir das informações obtidas, podem ser criados instrumentos que auxiliarão na tomada de decisões legais para gerenciar a atividade em futuros empreendimentos.

The dusky grouper (Mycteroperca marginata) is a marine species usually associated with rocky bottoms and reefs. The present work investigated the diet and feeding strategy of a dusky grouper population inhabiting a 4.5 km long pair of rocky jetties located in the mouth of Patos Lagoon estuary. No prior research has been conducted in such man-made habitat and the current study provides a basis for comparative studies on the diet of the dusky grouper populations inhabiting natural vs. man-made rocky habitats. Similarly with previous studies on natural substrates, crabs and fishes were the main food categories consumed (%IRI = 85.1 and %IRI = 12.6, respectively), whereas shrimps and mollusks had lower importance in the diet (%IRI = 1.9 and 0.4, respectively). As previously reported for dusky grouper populations inhabiting reefs and rocky bottoms, the present work revealed conspicuous size related dietary shifts. Blue crabs and fishes become increasingly important food items in the diet of larger individuals (> 500 mm, TL). Finally, it was found that the studied dusky population has a generalist feeding strategy with a high between-individual variation in prey consumption. Such strategy remained similar across the size increment of the species. Our findings suggest that man-made rocky substrates provide suitable feeding grounds for the dusky grouper in southern Brazil and could be used as an additional tool in the conservation efforts of this endangered species.A garoupa-verdadeira (Mycteroperca marginata) é uma espécie marinha geralmente associada a fundos rochosos e recifes. O presente trabalho investiga a dieta e estratégia alimentar de uma população da garoupa-verdadeira que habita um longo (4,5 km) par de molhes de pedra na desembocadura do estuário da laguna dos Patos, sul do Brasil. Não há trabalhos anteriores realizados nesse tipo de habitat construído pelo homem e este trabalho fornece uma base de comparação com estudos de dieta de outras populações da garoupa-verdadeira ocorrendo em habitats naturais. De modo similar ao encontrado em estudos prévios realizados em substratos naturais, caranguejos e peixes foram as principais categorias de alimento consumidas (%IRI = 85,1 e %IRI = 12,6, respectivamente), enquanto camarões e moluscos tiveram menor importância na dieta (%IRI = 1,9 e %IRI = 0,4, respectivamente). Como reportado anteriormente para populações de garoupa-verdadeira que habitam recifes e fundos rochosos, o presente trabalho revelou marcadas mudanças na dieta em função do tamanho da espécie. Siri-azul e peixes tornam-se gradativamente mais importantes na dieta de indivíduos maiores (> 500 mm de comprimento total, CT). Finalmente, foi observado que a população de garoupa-verdadeira teve uma estratégia alimentar generalista com uma elevada variação entre indivíduos no consumo de presas. Essa estratégia permaneceu similar ao longo do aumento em tamanho da espécie. Os resultados do presente trabalho sugerem que substratos rochosos estabelecidos pelo homem propiciam locais de alimentação adequados para a garoupa-verdadeira no sul do Brasil e que poderiam ser usados como ferramentas adicionais nos esforços de conservação dessa espécie ameaçada.

The dusky grouper, Mycteroperca marginata, is an important commercial marine fish that is currently considered an endangered species worldwide and listed as overexploited in Brazil. Although its reproductive biology has been studied elsewhere, no information is available for populations in its southernmost distribution limit on the Brazilian coast. The present work investigates age structure, growth and reproduction of individuals inhabiting a pair of rocky jetties, about 4.5 km long each, located in the mouth of Patos Lagoon in the municipality of Rio Grande, in the southwestern Atlantic Ocean. A total of 130 individuals obtained between February 2007 and May 2009 were analyzed, with total length ranging from 260 to 800 mm. The growth coefficient found in the present study (K: 0.069) was lower than values reported for dusky grouper populations from the Mediterranean Sea (0.087) and southeast Africa (0.09). This difference could be related to higher average water temperatures in these regions compared to the current study site or due to poorer habitat quality in terms of the shelters available for dusky grouper individuals to establish their territories. Microscopic ovarian analyses of individuals during three years of sampling revealed only the occurrence of immature and resting females. The absence of ripe or post-spawning individuals, associated with low GSI values (A garoupa-verdadeira, Mycteroperca marginata, é uma espécie de importância comercial que atualmente é considerada como ameaçada mundialmente e sobre-explotada no Brasil. Embora sua biologia reprodutiva tenha sido estudada em outras regiões, nenhuma informação está disponível sobre populações que habitam o extremo sul da sua distribuição na costa brasileira. O presente trabalho investiga a estrutura de idade, crescimento e reprodução de indivíduos que habitam dois molhes de pedra, com cerca de 4,5 km de extensão cada, localizados na desembocadura da laguna dos Patos no município de Rio Grande, no Atlântico Sudoeste. Foram analisados 130 indivíduos obtidos entre fevereiro de 2007 e maio de 2009, com comprimento total entre 260 e 800 mm. O coeficiente de crescimento no presente estudo (K: 0,069) foi inferior aos valores reportados para oMediterrâneo (0,087) e sudeste da África (0,09). Essa diferença pode estar relacionada a temperaturas médias maiores nessas regiões comparadas ao presente local de estudo ou devido a menor qualidade de habitat em termo de abrigos para os indivíduos de garoupa-verdadeira estabelecerem seus territórios. Análises microscópicas dos ovários dos indivíduos durante esses três anos de amostragens revelaram somente a ocorrência de indivíduos imaturos e fêmeas em repouso. A ausência de indivíduos ovados ou em pós-desova, associada com baixos valores do IGS (

AIM: The aim of this work was to study the relationships between temporal variability of Erodona mactroides and abiotic parameters of the water column and the substrate in a shallow embayment of the Patos Lagoon estuarine region in southern Brazil; METHODS: Samples were taken with a PVC corer (10 cm diameter) buried 10 cm into the sediment between October 2002 and December 2004. Each month 18 biologic samples were taken, six substrate samples were analyzed for sediment grain size and organic matter content and sediment deposition rates were determined by 12 sediment traps every two weeks. Salinity, water temperature, water level and estuarine freshwater discharge were measured daily. Abiotic parameters and bivalve densities were tested among months with registered mortality events by ANOVA (One-way, p = 0.05), being the E. mactroides seasonal variability tested by Kruskal-Wallis (p = 0.05). Regression analyses among abiotic parameters and Spearman's "R" correlation analyses between biological and environmental data were both performed; RESULTS: Two periods were identified with distinct features: one at the beginning of the study when observed limnetic conditions in the estuarine region were caused by the ENSO - El Niño 2002/2003 phenomenon when an absence of E. mactroides was registered as well as a higher percentages of fine sediments and lower percentages of organic matter. The second period was characterized by a decreasing influence of the El Niño and predominance of mixohaline conditions, recruitments and increasing densities of E. mactroides with a successive decrease of mean densities due to three mortality events, lower percentages of fine sediments and higher percentages of organic matter; CONCLUSIONS: The present study provides evidences that the occurrence of E. mactroides in the southern estuarine region depends on the water flow regime from the drainage basin, which characterizes species recruitment as temporally unpredictable and affects its persistence through time due to adverse conditions that influence species development like events of fine sediment deposition.OBJETIVO: O objetivo do presente trabalho foi avaliar as relações entre a variabilidade temporal de Erodona mactroides e os parâmetros abióticos da coluna d'água e do substrato em uma enseada rasa da região estuarina da Lagoa dos Patos, sul do Brasil; MÉTODOS: As amostras foram coletadas com um extrator de PVC (10 cm de diâmetro), enterrado a 10 cm no interior do sedimento, entre Outubro/02 e Dezembro/04. Em cada mês foram coletadas 18 amostras biológicas, seis réplicas de sedimento para análises granulométricas e teor de matéria orgânica, além de 12 réplicas quinzenais de experimentos de deposição de sedimentos. A salinidade, temperatura da coluna d'água, profundidade e vazão do estuário foram medidas diariamente. Os parâmetros abióticos e densidades do bivalve entre os meses em que foram observados eventos de mortalidade foram testados através de ANOVA (Uma via, p = 0,05), e a variabilidade sazonal de E. mactroides foi testada através da análise de Kruskal-Wallis (p = 0,05). Foi aplicada análise de Regressão entre os dados abióticos e Correlação de Spearman "R" entre os dados biológicos de densidade e parâmetros ambientais; RESULTADOS: Foram identificados dois períodos com características distintas: no início do estudo foram registradas condições limnéticas na região estuarina devido ao fenômeno ENSO - El Niño 2002/2003, quando foi registrada a ausência de E. mactroides, maiores percentuais de sedimento finos e menores percentuais de matéria orgânica. O segundo período foi caracterizado pela diminuição da influência do El Niño e predominância de condições mixohalinas, recrutamentos e pelo aumento das densidades médias de E. mactroides com sucessivos decréscimos no número de organismos devido a três eventos de mortalidade, menores percentuais de sedimentos finos e maiores percentuais de matéria orgânica; CONCLUSÕES: O presente estudo evidencia que a ocorrência de E. mactroides na porção sul da região estuarina, que depende do regime de vazão da laguna, caracteriza os recrutamentos como temporalmente imprevisíveis, e sua persistência é afetada por condições desfavoráveis a seu desenvolvimento como eventos de deposição de sedimentos finos.

The objective of this study was to identify the patterns of seasonal and diel variation and the most important abiotic factors that influence variation in the fish assemblage of the Delta of the Jacuí River in southern Brazil. Seventy-two samples were collected over a one year period. Water temperature was the abiotic factor with the greatest influence on the distribution of the assemblage. The structure of the assemblage exhibited significant changes in terms of species abundance and biomass during the year, with the greatest abundance and biomass being observed during the autumn. There was no significant difference between day and night in terms of abundance, but biomass was significantly greater during the night than during the day.O objetivo deste estudo foi identificar o padrão de variação sazonal e circadiana e os principais fatores abióticos que influenciam a estrutura da assembleia de peixes do delta do rio Jacuí, região sul do Brasil. Foram realizadas 72 amostragens durante o período de um ano. A distribuição da assembleia foi influenciada principalmente pela temperatura da água. A estrutura da assembleia apresentou diferenças significativas na abundância e biomassa das espécies entre as estações do ano e as maiores abundância e biomassa foram apresentadas no outono. Quando os resultados do dia e da noite foram comparados, a abundância não apresentou diferença significativa, entretanto a biomassa da noite foi significativamente maior que a do dia.

The geological evolution of the continental shelf and in the coastal zone of southern Brazil during the Quaternary period is addressed in this study. High-resolution seismic records obtained at the Patos Lagoon revealed the presence of channels that deeply dissected the coastal zone before the formation of the modern, low-relief, coastal plain. Two periods of channel incision are inferred, based mainly on seismic records. The paleodrainage paths mapped from the seismic records can be connected with those recognized by previous studies on the adjacent continental shelf and slope. Upstream, the drainage incised mainly into the coastal prism deposited during previous sea-level highstand events. The paleodrainage network, recognized on the coastal plain and continental shelf, represents a river-shelf system, linking the drainage basin to the depositional settings on the marginal basin, bypassing the continental shelf exposed during a forced regression event. The drainage incised into the coastal plain and continental shelf of Rio Grande do Sul played an important role in the basin-margin architecture, facies distribution and accommodation during the Quaternary sea-level fluctuations.A evolução geológica da plataforma continental e zona costeira do sul do Brasil no período Quaternário é aqui enfocada. Registros sísmicos de alta resolução da Lagoa dos Patos revelaram canais que dissecaram profundamente a região antes da formação da planície costeira atual. Dois períodos de incisão de canal são inferidos, baseados principalmente em registros sísmicos. Os cursos fluviais mapeados por sísmica podem ser conectados àqueles reconhecidos na plataforma continental adjacente por estudos anteriores. à montante, a incisão da drenagem ocorreu principalmente no prisma sedimentar costeiro depositado durante eventos pretéritos de nível do mar alto. A rede de paleodrenagem, reconhecida na planície costeira e na plataforma continental, representa um sistema de ligação da bacia de drenagem continental aos depocentros da bacia marginal, sobrepassando a plataforma continental exposta durante uma regressão forçada. A incisão da drenagem na planície costeira e plataforma continental do Rio Grande do Sul desempenhou um papel importante na arquitetura marginal, distribuição de fácies e no espaço de acomodação durante as flutuações do nível do mar no Quaternário.

Global coastal zones are constantly changing due to the actions of various physical forces. Recent studies show that the supply of suspended sediment of continental origin plays an important role in these changes. Once in the coastal region, this sediment significantly influences the sedimentation process on the inner shelf. Thus, understanding the transport and destination of these suspended sediments is crucial to interpret the morphodynamic evolution of the seabed and biogeochemical processes in the ocean. The Southwest Atlantic Shelf is the largest continental shelf in the Southern Hemisphere and one of the most important in biological production, because of the great continental contribution exercised by both Río de la Plata and Patos Lagoon. Studies in the region showed that these effluents are significantly affected by the El Niño–Southern Oscillation (ENSO) effect, which can interfere with the availability of suspended material inserted into the coastal region. Despite the great efforts of several authors to understand these changes and their interactions with the environment, some questions remain unanswered. Thus, this work aims to fill this gap by answering questions related to the contribution of suspended sediment of continental origin and its behaviour on the Southwest Atlantic Inner Shelf. The behaviour of suspended sediment was investigated in two distinct periods using the hydro-morphodynamic model TELEMAC-3D: one representing normal years, that is, without the effect of ENSO (2005–2006) and the other experiencing the effect of ENSO (2008–2009).The model was calibrated and validated using field data for both studied periods. R esults were based on statistical analysis, such as wavelet and empirical orthogonal function (EOF) analysis, in addition to time series analysis. Results showed that the Southwest Atlantic Inner Shelf is mainly influenced by the fluvial discharge of Río de la Plata and Patos Lagoon, and by the local wind. Río de la Plata is the largest exporter of suspended sediment in the region, with an approximate rate of 1.2 × 108 tons.year-1 in neutral (normal) years and 3.0 × 108 tons.year-1 in years under the influence of ENSO. The Patos Lagoon, on the other hand, exports approximately 1.25 × 107 tons.year-1 in the period without the ENSO effect and 1.35 × 107 tons.year-1 in the period influenced by ENSO. Results also showed that the fluvial discharge interacts with the suspended sediment in seasonal to interannual scales, while the wind contributes to the concentration of suspended sediment on synoptic scales. Still on the wind regime, results show that the local wind regime gains importance particularly when the suspended sediment reaches the coastal region. • The Southwest Atlantic Inner Shelf is influenced by the continental discharge and local wind. • The Río de La Plata is the major export of suspended sediment in the region. • The SSCare influenced by the ENSO cycles. • The river discharge from Patos Lagoon and íde la Plata and Río de La Plata interact with the SSC on a seasonal up to interannual time scale of variability. • The wind contribution on the SSC behaviour gains importance on the inner shelfon a synoptic time scale. [ABSTRACT FROM AUTHOR]

Background Toxic cyanobacterial blooms are recurrent in Patos Lagoon, in southern Brazil. Among cyanotoxins, [D-Leu1] microcystin-LR is the predominant variant whose natural cycle involves water and sediment compartments. This study aimed to identify and isolate from sediment a bacterial strain capable of growing on [D-Leu1] microcystin-LR. Sediment and water samples were collected at two distinct aquatic spots: close to the Oceanographic Museum (P1), in Rio Grande City, and on São Lourenço Beach (P2), in São Lourenço do Sul City, southern Brazil. Methods [D-Leu1] microcystin-LR was isolated and purified from batch cultures of Microcystis aeruginosastrain RST9501. Samples of water and sediment from Rio Grande and São Lourenço do Sul were collected. Bacteria from the samples were allowed to grow in flasks containing solely [D-Leu1] microcystin-LR. This strain named DMSX was isolated on agar MSM with 8 g L−1 glucose and further purified on a cyanotoxin basis growth. Microcystin concentration was obtained by using the ELISA immunoassay for microcystins whereas bacterial count was performed by epifluorescence microscopy. The genus Pseudomonas was identified by DNA techniques. Results Although several bacterial strains were isolated from the samples, only one, DMXS, was capable of growing on [D-Leu1] microcystin-LR. The phylogenetic analysis of the 16S rRNA gene from DMXS strain classified the organism as Pseudomonas aeruginosa. DMXS strain incubated with [D-Leu1] microcystin-LR lowered the amount of toxin from 1 μg.L−1 to

Diatom assemblages provide a strong basis for detailed interpretations of paleoceanography and diatom paleoecology of the southern Brazilian coast. Nine cores obtained in the coastal plain, shelf and continental slope and thirteen surface sediment samples of the Patos Lagoon, provide an excellent opportunity to use a paleoecological approach to study detailed Quaternary environmental changes in the southern coasts. In the interval studied, the basin sedimentation occurred in a marine-dominated environment related to humid periods prior to 43,500 year BP. Abundant diatom taxa are highlighted as excellent indicators of environmental changes, including salinity, sediment composition and transport by incised-valleys, providing additional insights into coastal evolution. Paralia sulcata is dominant in all analyzed cores, occurring continuously from Late Pleistocene to Holocene, but is rare in the modern sediments. Non-marine diatom assemblages occurred continuously, but in very low densities in periods before and after the Last Glacial Maximum. Abrupt changes in sedimentation have been recorded related to shifts from marine-dominated to shallow-estuarine deposition. During the Holocene, sea-level rose rapidly which is responsible for the progressive coastal flooding prior to 8420–7930 year BP. The Holocene barrier system became more continuous and Patos Lagoon developed. Consequently, the secondary former inlets from the Jacuí and Camaquã rivers are closed and only one single inlet (Rio Grande channel) remains active. The spatial distribution of modern assemblages is controlled by salinity gradient, wind action, and climate forcing. The bottom sediments of Patos Lagoon are dominated by freshwater diatom Aulacoseira veraluciae, Aulacoseira sp. 2 and marine-estuarine species of Cyclotella litoralis . [ABSTRACT FROM AUTHOR]

Although ariid catfishe species are known to use coastal systems during some stages of their life cycles, the energetic contribution of estuarine resources and habitat use by many species in this family are still unclear. We used stable isotope analyses to estimate the assimilation of primary carbon sources and to infer the use of estuarine and freshwater habitats by two ariid catfishes Genidens barbus (Lacepède, 1803) and Genidens genidens (Cuvier, 1829). An isotopic mixing model revealed that juveniles of both catfish species consume considerable amounts of estuarine-produced carbon sources (G. barbus: 54-87% and G. genidens: 36-84%). However, G. genidens adults rely more on freshwater-derived carbon sources (31-77%) than on estuarine sources (23-69%). These results support the hypothesis that both species occupy the estuary and assimilate organic carbon produced in this region during their early stages, but G. genidens adults consume carbon sources associated with the freshwater portion of the lagoon. [ABSTRACT FROM AUTHOR]