Mirim Lagoon Research Articles

Modelling species distributions to predict areas at risk of invasion by the exotic aquatic New Zealand mudsnail Potamopyrgus antipodarum (Gray 1843)

Abstract The use of bioclimatic models to predict areas subject to invasion by exotic species has been important in the development of preventive conservation measures. The native New Zealand mudsnail Potamopyrgus antipodarum is an invasive mollusc, now with a worldwide distribution, that causes economic and ecological problems in invaded areas and has recently been designated as one of the 100 worst invasive species in Europe. In this study we sought to determine the potential distribution of and areas susceptible to invasion by P. antipodarum in South America and worldwide, in present and future scenarios (2070), using MaxEnt models. The models were developed using georeferenced occurrence data and bioclimate and hydroclimate variables to predict scenarios of the geographical distribution of P. antipodarum. Possible routes of invasion into South America were predicted. Present‐day scenario of the worldwide distribution (all known occurrences) of P. antipodarum, based on the bioclimatic and hydroclimatic models, are highly accurate, with area under curve higher than of 0.87. The models indicated that environmentally suitable areas exist in South America and in other regions of the world where the species has not yet been recorded. The predicted susceptibility includes approximately 80 protected areas in the South American continent. Models projected in an optimistic and pessimistic future scenario, based on the worldwide distribution, show increased environmental suitability of regions outside the current species distribution, including Brazil (south‐west), Uruguay (near Mirim Lagoon), Nigeria, Ethiopia (lakes Tana and Chomen), Tanzania, Cameroon (bordering lakes Bamendjing, Bankim, and Mbakaou), Equatorial Guinea, Congo, Rwanda, Burundi (Lake Tanganyika environs), Uganda, Tanzania (Naivasha), and South Africa (surrounding Gordon's Bay). The main vector for dispersal to South America would be ballast water coming from waterways and ports located in the predicted areas. Fish farming is also a possible route, since the mudsnail is resistant to the digestive tract of rainbow trout (Oncorhynchus mykiss). Current records and predicted susceptible areas coincide with port areas and sites where this fish is farmed. Geographical distribution modelling proved to be helpful in identifying environmentally suitable areas for the invasion of P. antipodarum. The model also suggests a future expansion of the species distribution, possibly affected by climate change.

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.

VALIDATION OF THE DIGITAL ELEVATION MODEL (SRTM) WITH GNSS SURVEYING APPLIED TO THE MIRIM LAGOON HYDROGRAPHIC BASIN

Abstract Between 2013 and 2014, a kinematic positioning based on the Global Navigation Satellite System (GNSS) was carried out for this research work. This GNSS survey resulted in 275916 points with tridimensional coordinates in the cross-border basin area of 58205 km2 called Mirim Lagoon Hydrographic Basin, located in south of Rio Grande do Sul (Brazil) and west of Uruguay. This study aims at showing the methodology firstly and, furthermore, results regarding the validation of the vertical accuracy of the DEM SRTM through kinematic positioning by GNSS, in the Mirim Lagoon Hydrographic Basin region. Also, the GNSS surveying data was post-processed with the Precise Point Positioning (PPP) method, and the ellipsoidal height was converted into orthometric height through the software INTPT geoid. During this study, the geopotential model (EGM96) was used to transform altitude differences between two countries, Brazil and Uruguay. Results showed that the vertical mean absolute error of the DEM SRTM vary from 0.07 m to ± 9.9m with average of -0.28m. This vertical accuracy is better than the absolute vertical accuracy value of ±16m published in the SRTM data specification and validates the DEM SRTM.

Water level variability of the Mirim - São Gonçalo system, a large, subtropical, semi-enclosed coastal complex

Abstract Coastal lagoons, channels, and wetlands are sensitive ecosystems with high productivity and biodiversity. These systems often provide society with the valuable freshwater resources and many ecosystem services. In the subtropics, the hydrological systems inherit the typically high climatic and weather variability characteristics of these zones. Therefore, knowing the natural variability of these characteristics is crucial for the sustainable use of the water resources of these systems. In the present paper, we investigated the hydrodynamics of the Mirim-Sao Goncalo system, which comprises a large, shallow coastal lake, a 78 km-long channel and their adjacent floodplains and wetlands, with a focus on water level oscillations. We used a combination of numerical simulations, gauge station data and Synthetic Aperture RADAR imaging to evaluate the influence of the incident winds and the discharges of the main tributaries on the system’s water levels and the establishment of barotropic gradients. We analyzed the water level variability of the Mirim lagoon and the Sao Goncalo Channel and their overflows to the adjacent floodplains. The simulations are five years long and cover the period starting in January 2000 to December 2004. The analysis indicates that the discharge of the tributaries mainly governs the system’s temporal patterns. Wind action has two distinct influences on the systems. First, the wind dams the water at the southern portion of the Mirim Lagoon, which creates a persistent barotropic gradient in the surface. This gradient is often destroyed and dislocated northwards in a rotational fashion when the wind blows from the southern quadrant. Second, the wind perturbs the temporal variability patterns, resulting in high-frequency oscillations of the water level temporal signal. Flooding is frequent in the lands adjacent to the lagoon and the channel and results from the combination of the geomorphological and climatic settings of the region. The system is surrounded by ancient lagoon deposits with an extremely flat and low-lying topography, which favors the flooding of large extents. The large catchment area and the high precipitation rate over this region result in significant water level oscillations, causing the system to overflow and leading to subsequent floods.

Functional Scenarios for the Revitalization of the Port of Pelotas, State of Rio Grande do Sul, Brazil

O presente estudo teve por objetivo delinear três cenários funcionais para o Porto de Pelotas, localizado no centro do maior sistema lagunar costeiro do País, situado na Planície Costeira do Estado do Rio Grande do Sul, Brasil, com o intuito de nortear os tomadores de decisão quanto ao planejamento de ações estratégicas para sua revitalização econômica, considerando que este Porto, presentemente, vem sendo alvo de interesses político-econômicos em nível local, regional e bi-nacional. Os resultados alcançados se resumem em um levantamento da sua atual situação funcional, além do delineamento de três cenários futuros, baseados em alternativas funcionais estabelecidas para o mesmo. Para tanto, foram utilizadas as metodologias de pesquisa exploratória, além da análise SWOT, prospecção de cenários e entrevista semi-estruturada com atores chave para a pesquisa. Concluindo este artigo, constata-se que, apesar de sua atual relativa estagnação econômico-funcional, o Porto de Pelotas apresenta condições para desempenhar um novo e importante papel no processo de retomada do desenvolvimento econômico da metade sul do Rio Grande do Sul, bem como do desenvolvimento integrado da Bacia da Lagoa Mirim através da hidrovia bi-nacional Brasil-Uruguai.

Diagnóstico participativo para planejamento territorial de áreas protegidas:

A Estação Ecológica do Taim é uma Unidade de Conservação (UC), localizada na porção Sul da PlanícieCosteira do estado do Rio Grande do Sul, Brasil. Abrange parte dos municípios do Rio Grande e de SantaVitória do Palmar, entre a Lagoa Mirim e o Oceano Atlântico. Embora tenha sido estabelecida há trintaanos e seja internacionalmente reconhecida como importante área úmida e de proteção de espéciesameaçadas, essa UC ainda carece de plano de manejo e de ordenamento territorial. Imersa em umamatriz cultural e de atividades produtivas conflitantes com os interesses de conservação, a participaçãoda sociedade na elaboração do plano de gestão é um aspecto fundamental. Desta forma, foi aplicadoum diagnóstico participativo como mecanismo para apreender os modos de relacionamento dapopulação local e seus conhecimentos sobre o meio ambiente onde está inserida a UC, bem como paraidentificar a percepção da comunidade científica envolvida com pesquisas naregião. As informaçõesobtidas por meio do diagnóstico participativo, espacializadas em um Sistema de Informação Geográficae interpretadas juntamente com dados físicos, biológicos e antrópicos, permitiram caracterizar noterritório ameaças e oportunidades à conservação na área da Unidade. Tal investigação tornou possívelpropor um esquema de zoneamento de usos, e a identificação de ações de manejo de forma a subsidiaro planejamento e o ordenamento territorial para essa UC.

Seletividade da pesca da viola Loricariichthys anus (Siluriformes: Loricariidae) na Lagoa Mirim, RS, Brasil

A Lagoa Mirim é um dos principais corpos hí­­dricos do sistema lagunar meridional da América do Sul e possui regime de águas compartilhadas entre o Brasil e o Uruguai. A atividade pesqueira na região apresenta diminuição dos ní­­veis de captura, fazendo com que os pescadores aumentem o esforço de pesca. A viola (Loricariichthys anus) é uma das espécies nativas mais importante da região para a pesca artesanal, sendo assim, faz-se necessário o estudo de seus estoques e do esforço pesqueiro adequado. O objetivo do trabalho foi identificar o tamanho de malha que apresenta maior eficiência do ponto de vista econômico e sustentável para a pesca da viola. O estudo foi desenvolvido utilizando-se 10 redes de malha de 60 mm, 10 redes de malha 70 mm e 10 redes de malha 80 mm entre nós opostos. A pesca foi realizada com o conjunto das diferentes malhas, dispostas intercaladas, por um perí­­odo de 12 horas í­Â noite, de acordo com o procedimento dos pescadores locais. O número total de peixes capturados em cada malha foi distribuí­­do por classe de comprimento total e determinada a seletividade. O resultado indica que a malha 70 mm é mais eficiente, capturando peixes com tamanho mí­­nimo superior ao da primeira desova, o que a torna, portanto, a mais recomendada para a pesca da viola na Lagoa Mirim, RS.

Ichthyofauna of the hydrographic basin of the Chasqueiro Stream (Mirim Lagoon system, southern Brazil): generating subsidies for conservation and management

Studies that organize lists of species are essential and act as the starting point for future discussions on the ecology of fish in environments that are poorly studied. The present paper describes the fish assemblage of the hydrographic basin of Chasqueiro Stream, an important component of the Mirim Lagoon system. Fish were collected during one year period between August/2012 and July/2013 in six sites, comprising three biotopes: upstream, reservoir and downstream. A total of 22,853 specimens were collected, and were distributed into 83 species, 20 families, and eight orders. The two species with the largest number of individuals captured were Bryconamericus iheringii with 2,904 (12.71%) and Cheirodon ibicuiensis with 2,868 (12.55%). Characiformes and Siluriformes were the most representative orders in terms of richness and abundance. Bryconamericus iheringi and Cyanocharax alburnus were the species with the highest abundance upstream, while Hyphessobrycon luetkenii and Corydoras paleatus contributed more to the abundance downstream. Cheirodon ibicuhiensis and Heterocheirodon jacuhiensis were the most representative species in the reservoir. This study revealed a rich fauna of fish, which should be preserved for future generations and for the maintenance of local and regional biodiversity.

Erratum: Ichthyofauna of the hydrographic basin of the Chasqueiro Stream (Mirim Lagoon system, southern Brazil): generating subsidies for conservation and management

Erratum: Ichthyofauna of the hydrographic basin of the Chasqueiro Stream (Mirim Lagoon system, southern Brazil): generating subsidies for conservation and management

Establishing evidence of a non-native species Pachyurus bonariensis Steindachner, 1879 (Perciformes, Sciaenidae) in Mirim Lagoon, Rio Grande do Sul (Brazil)

The La Plata croaker (Pachyurus bonariensis) family Sciaenidae, is a small (< 23 cm) benthopelagic fish that originated in the Parana- Paraguay-Uruguay river systems in South America. Its first record in the Patos Lagoon drainage area, Rio Grande do Sul (Brazil) occurred in 2001. This research reports for the first time, the occurrence of both juvenile and adult specimens of P. bonariensis in the Sao Goncalo Channel (a 75 km long waterway between Patos and Mirim lagoon) and in the Mirim Lagoon, in 2005 and 2007 respectively. A total of 434 gonads were analyzed histologically from specimens captured by artisanal fishermen at Capilha, Mirim Lagoon between 2008 and 2010. Gonadal development was observed and described. Pachyurus bonariensis probably dispersed from northern Patos Lagoon in 2001 to the Sao Goncalo Channel by 2005. The occurrence of adults in limnic waters in the Sao Goncalo Channel and further south in the Mirim Lagoon in 2007, confirm that P. bonariensis is now an established species in Mirim Lagoon and could become a commercially important species to the artisanal fishermen of the area. Likewise at the limnetic northern parts of Patos Lagoon, P. bonariensis is now abundant at Mirin Lagoon and the ecological impacts of this range extension must be investigated.

Elites locais e changadores no mercado atlântico de couros (Rio Grande e Soriano, 1780-1810)

Taking into account data showing the relationship of subaltern groups (frequently associated with social chaos and criminal life), indigenous and slaves with members of local elites in the eastern part of the River Plate, this article emphasizes the importance of these relationships for developing and maintaining Atlantic business which meant trade of hides, tobacco, rum and slaves. Th e text examines the social strategies of the creation of these networks and their geographic extensions, between Buenos Aires, Rio de Janeiro, Lisbon and Madrid, without neglecting the Mirim Lagoon neighbors.

High plasticity in habitat use of Lycengraulis grossidens (Clupeiformes, Engraulididae)

In this study, we analyzed the Sr:Ca and Ba:Ca ratios of the otoliths of 139 Lycengraulis grossidens individuals sampled along the southwestern Atlantic Ocean, including two freshwater areas, to describe patterns of habitat use and their latitudinal organization. Otolith sections were analyzed by laser ablation inductively coupled plasma mass spectrometry along core-to-edge transects. Otolith edge analysis revealed significant differences in Sr:Ca and Ba:Ca ratios between fish from freshwater habitats and those from estuarine/marine habitats, indicating that these ratios may be used to describe habitat use patterns. Lifetime transects of Sr:Ca and Ba:Ca indicate at least four distinct habitat use patterns: freshwater residents, estuarine/marine residents, and two distinct diadromous/nomadic types. Most individuals (88.6%) sampled at northern latitudes in sheltered marine bays and the coastal ocean were estuarine/marine residents, whereas at southern latitudes, most individuals were diadromous (72.5%). We also identified landlocked populations in the Uruguay River and in Mirim Lagoon. These results suggest that L. grossidens exhibits flexible habitat use strategies and may use freshwater, estuarine and marine environments throughout their lifetime.

Monotonic trend and change points in southern Brazil precipitation

Scientific evidence on climate changes at global level has gained increasing interest in the scientific community in general. The impacts of climate change as well as anthropogenic actions may cause errors in hydro-agricultural projects existent in the watershed under study. This study aimed to identify the presence or absence of trend in total annual precipitation series of the watershed of the Mirim Lagoon, state of Rio Grande do Sul-RS / Brazil / Uruguay (Brazilian side) as well as to detect the period in which they occurred. For that, it was analyzed the precipitation data belonging to 14 weather stations. To detect the existence of monotonic trend and change points, it was used the nonparametric tests of Mann-Kendall and Mann-Whitney, the "t" test of Student for two samples of unpaired data (parametric), as well as the technique of progressive mean. The Weather Station 3152014 (Pelotas) presented changes in the trend in the series of annual precipitation in the period from 1953 to 2007. The methodologies that use subdivided series were more efficient in detecting change in trend when compared with the Mann-Kendall test, which uses the complete series (from 1921 to 2007).

Size-selective predation of the catfish Pimelodus pintado (Siluriformes: Pimelodidae) on the golden mussel Limnoperna fortunei (Bivalvia: Mytilidae)

This paper describes the size-selective predation on Limnoperna fortunei (Dunker, 1857) by Pimelodus pintado (Azpelicueta, Lundberg & Loureiro, 2008) from the time it arrived at the Mirim Lagoon basin (2005). Sampling was carried out using bottom trawl in depths of 3-6 m, from January to November 2005, and from October to November 2008. Pimelodus pintado began to prey upon L. fortunei soon after its arrival (austral spring of 2005). On the spring of 2008, L. fortunei was found to be the most important food item of P. pintado. The variation in length of the mussels (0.7-3.2 cm, with a mode of 1.3 cm) indicates that the species is now fully established in the system. Our data indicates that large individuals of P. pintado incorporate more mussels in their diets than small individuals. However, regardless of their size, P. pintado individuals predate only on small (<1.4 cm) representatives of L. fortunei. This prey size corresponds to a phase when the mussel is more mobile and readily available for fish. Larger, more aggregated prey groups that are attached to hard substrates are avoided by fish predators.

Modelagem dos impactos ecológicos do projeto hidroviário da Lagoa Mirim (Brasil-Uruguai), baseada em Raciocínio Qualitativo

This study is an application of the scientific mediation process through modeling the physical, chemical and biological impacts of a waterway construction in Mirim Lagoon. Qualitative modelling process, based on Qualitative Reasoning, was conduced to better understand the ecological impact on water environment. The qualitative reasoning simulation show clear trends towards a loss of the physiochemical natural characteristics of the lagoon (“backwater effect”) and a decline of macrofit, invertebrate, water birds and fish species. Furthermore, the simulation showed the spreading of the golden mussel (Limnoperma fortunei), which is an invasive species.

Pisces, Perciformes, Gobiidae, Evorthodus lyricus (Girard, 1858): new record from Patos-Mirim Lagoon System, state of Rio Grande do Sul, southern Brazil

The present note records for the first time the tropical gobiid fish Evorthodus lyricus (Girard, 1858) from Patos- Mirim Lagoon System, state of Rio Grande do Sul, southern Brazil. Considering the known distribution of the species, and unpublished data obtained from fish collections, the present record widens the distribution of E. lyricus in 300 km southwards, and is the first occurrence of the species for freshwater conditions in southern Brazil.

Whitemouth croaker, Micropogonias furnieri, trapped in a freshwater coastal lagoon: a natural comparison of freshwater and marine influences on otolith chemistry

Strontium and barium incorporation into otoliths was compared between whitemouth croaker, Micropogonias furnieri, collected from an entrapped freshwater population (Mirim Lagoon) and a normal marine/estuarine population in southern Brazil. Chemical analysis was performed using LA-ICPMS with the objective of validating the effects of marine and freshwater environments on Sr and Ba incorporation as a basis for further investigation of marine and freshwater connectivity of M. furnieri. The freshwater population was dominated by older fish with mean ±SD age of 34±1 y, whereas the coastal samples were dominated by younger fish of 14±7 y. Comparison of strontium and barium incorporation among otolith life-history profiles indicated significantly higher barium and lower strontium for the freshwater population compared to the marine population. Furthermore, comparison of otolith material deposited in the freshwater, estuarine and marine life-history phases demonstrated clear differences among these environments. Mean concentrations of strontium and barium in otoliths of M. furnieri were respectively 710 and 112 µg g-1 for freshwater, 2069 and 16.7 µg g-1 for estuarine, and 2990 and 2.7 µg g-1 for marine life-history phases. Barium concentrations in otoliths from the freshwater population of M. furnieri appeared high relative to other freshwater species. Strontium levels across life-history profiles of marine fish increased with age from 2000 to 2900 µg g-1, possibly indicating more time spent in marine than estuarine waters with age. In contrast, for the freshwater population, strontium levels decreased during the first year of life approximately to 700 µg g-1, and remained low and stable thereafter, consistent with the early life-history occurring in an estuarine environment prior to entrapment in Mirim Lagoon. The results confirm the strong and opposite effects of marine and freshwater environments on incorporation of barium and strontium into otoliths, and indicate that the population of M. furnieri in Mirim Lagoon represents an isolated population that does not reproduce and is therefore likely to become extinct.

Benthic community response to a passive fishing gear in a coastal lagoon (South Brazil)

The influence of a passive shrimp fishing gear on benthic communities was studied at Laguna Estuarine System (South Brazil), a shallow choked coastal lagoon. The gear is composed by a group of fyke nets (25 mm mesh size) set in contact to the bottom, fixed with stakes forming a cage-like structure (around 30 m2). Samplings were conducted in the two main fishery areas of the estuarine system, Mirim (sand bottoms) and Imarui (muddy bottoms) lagoon, in May 2005. In each area, 10 fyke net enclosures and 10 nearby sites without nets (control) were sampled. Microphytobenthos biomass (chlorophyll a and phaeopigments), number of taxa/species, density, Hill’s number N 1 and N 2, and estimated number of species (ES100) were used as community attributes. For the nematodes, values of the maturity index and abundance of Wieser’s feeding type were used as well. The effects of the small-scale passive shrimp fishing gear on the coastal lagoon bottoms were dependent on the benthic component analyzed and the type of sediment. Whereas macrofauna was not affected by the net enclosures, meiofauna and nematodes, particularly from the mud sites were. At the sand site, the fyke net enclosures caused a decrease in the microphytobenthos biomass and changed the relative abundances of non-selective deposit feeding and epigrowth-feeding nematodes. The results indicated that small-scale static nets, such as the studied fyke enclosures, produced low intensity levels of disturbance. However, the enclosed area by nets at Laguna had already reached around 25,000 m2. Given the large proportion of the coastal population involved and the area closed by nets, management policies should consider site-specific differences within the same estuarine system.

Submarine groundwater discharge of nutrients to the ocean along a coastal lagoon barrier, Southern Brazil

The Patos–Mirim Lagoon system along the southern coast of Brazil is linked to the coastal ocean by a narrow mouth and by groundwater transport through a Holocene barrier. Although other groundwater systems are apparently active in this region, the hydraulic head of the lagoon, the largest in South America, drives groundwater transport to the coast. Water levels in wells placed in the barrier respond to changing water level in the lagoon. The wells also provide a measure of the nutrient concentrations of groundwater flowing toward the ocean. Additionally, temporary well points were used to obtain nutrient samples in groundwater on the beach face of the barrier. These samples revealed a subterranean freshwater–seawater mixing zone over a ca. 240 km shoreline. Previously published results of radium isotopic analyses of groundwater and of surface water from cross-shelf transects were used to estimate a water flux of submarine groundwater discharge (SGD) to nearshore surface waters of 8.5 × 10 7 m 3/day. Using this SGD and the nutrient concentrations in different compartments, nutrient fluxes between groundwater and surface water were estimated. Fluxes were computed using both average and median reservoir (i.e. groundwater and surface water) nutrient concentrations. The SGD total dissolved inorganic nitrogen, phosphate and silicate fluxes (2.42, 0.52, 5.92 × 10 6 mol day − 1, respectively) may represent as much as 55% (total N) to 10% (Si) of the nutrient fluxes to the adjacent shelf environment. Assuming nitrogen limitation, SGD may be capable of supporting a production rate of ca. 3000 g C m 2 year − 1in the nearshore surf zone in this region.

Avaliação da Saúde Ecológica do Sistema Estuarino de Laguna (SC) Baseado nas Espécies de Foraminíferos e Tecamebas

The estuarine system of Laguna (Santa Catarina, Brazil), composed by lagoons of Santo Antonio, Imaruí and Mirim, situated to 130 km south of Florianópolis was evaluated through the association of foraminifera and thecamoebians as biological indicator organisms. The study reveals different population density patterns reflecting the environmental conditions. It is observed the formation of 4 groups. The group representing the north of the lagoon of Imaruí and the south of the Mirim lagoon (stations 14-17) is related to low density of foraminifera and thecamoebians. In the north of the lagoon of Santo Antonio and in the south part of the lagoon of Imaruí (7-13), Ammotium salsum, Ammobaculites exigus and Gaudryina exillis dominate. The group lagoon inlet (1, 2, 4-6) is composed by the stations more influenced by saline waters, presenting the highest diversities, where Elphidium poeyanum and Saccamina sphaera dominate. The group formed by stations collected in the river D'Una, Tubarão, and Mirim lagoon (3, 18-25) presents M. fusca and species of thecamoebians as indicator of large fresh water influence. Despite high fresh water input, it was observed low efficiency in water renewal especially in the north part of the estuarine system.