Plata Basin Research Articles

Unveiling mercury levels: Trophic habits influence on bioaccumulation in two Otariid species

Mercury, a toxic metal released by various human activities, exerts environmental stress through its bioaccumulation and biomagnification, particularly in marine habitats. South American fur seals (Arctocephalus australis) and sea lions (Otaria flavescens) reproduce on the Atlantic coast of Uruguay. As top predators, they can accumulate toxic levels of mercury and are often used as sentinel species for monitoring ecosystem health. Fur seals prey on pelagic species, such as fish and squid, while sea lions consume coastal-benthic prey. We analyzed the total mercury concentration (THg) in hair and the trophic habits (δ13C and δ15N) of females from both species. The average THg concentration in adult female sea lions (30.5 ± 9.3 μg/g dry weight) was significantly higher than in fur seals (6.3 ± 2.5 μg/g dry weight). Additionally, the mean δ15N and δ13C values were significantly higher in sea lion (δ15N: 19.2 ± 0.6‰, δ13C: −13.8 ± 0.2‰) compared to fur seals (δ15N: 16.5 ± 0.5‰, δ13C: −15.5 ± 0.6‰). Our results suggest that different trophic levels and feedings areas affect the THg concentration in Uruguayan Otariids. Notably, at the intraspecific level, the THg concentration in sea lions increased with δ13C values, suggesting a link to coastal feeding habits. This indicates that coastal feeding behaviors, compared to feeding in pelagic environments, enhance mercury bioaccumulation in Otariids along the Uruguayan coast, with the discharge of freshwater from the Río de la Plata (one of the largest estuaries in South America) basin identified as a potential mercury source. THg concentrations found in female sea lion hair are the highest reported in Otariids globally. Mercury levels exceeded toxic thresholds observed in other mammals and could pose significant health risks. Our findings may explain why sea lions were particularly affected by the avian influenza outbreak in Uruguay compared to fur seals. Monitoring the declining sea lion population is crucial, making our results significant for integrated conservation and management strategies.

EROD activity in the native fish Cnesterodon decemmaculatus as a biomarker for assessing aquatic pollution by AhR agonist chemicals within the Rio de la Plata Basin

The 7-ethoxyresorufin-O-deethylase (EROD) activity was first time characterized in the neotropical fish Cnesterodon decemmaculatus as a biomarker for assessing environmental health in aquatic ecosystems of the Rio de la Plata Basin impacted by organic pollutants agonist of the aryl-hydrocarbon receptor (AhR). Both laboratory and field studies were conducted. Laboratory experiments were run using β-naphthoflavone (BNF) as an AhR agonist model. A clear concentration-response relationship was found between 1 and 100 μg/L, with a NOEC and LOEC of 1 and 10 μg/L. A fast time-dependent response was observed with a significant induction after 24 h and a plateau from 24 to 48 h up to 264 h of exposure. Differences in basal activity were found between juveniles, females, and males, but induction levels were similar. Both basal activities and induction levels were distinct in the whole body, liver, gill, muscle, brain, and embryos. Fold-change inductions in the respective tissues were: 20, 114, 3, 5, 1, and 14. Maternal transfer and early cyp1a activation were unveiled by embryonic induction. Clear differences in EROD activity were found among juveniles collected in hydrocarbon-polluted streams, beside the La Plata Petrochemical hub, and a reference stream. Similar EROD activities were observed in laboratory and feral fish, usually with values below or above 1,000 pmol/min x mg protein for unexposed or exposed organisms. The study contributes with original information about EROD activity in C. decemmaculatus that encourages the use of both the response as a robust biomarker of exposure and the species as a good sentinel organism to be included in surveillant programs for assessing aquatic pollution by AhR agonist chemicals within the Rio de la Plata Basin within the One Health paradigm.

Impact of antiparasitic used in livestock: effects of ivermectin spiked sediment in Prochilodus lineatus, an inland fishery species of South America.

Ivermectin (IVM) is a widely used antiparasitic. Concerns have been raised about its environmental effects in the wetlands of Río de la Plata basin where cattle have been treated with IVM for years. This study investigated the sublethal effects of environmentally relevant IVM concentrations in sediments on the Neotropical fish Prochilodus lineatus. Juvenile P. lineatus were exposed to IVM-spiked sediments (2 and 20µg/Kg) for 14days, alongside a control sediment treatment without IVM. Biochemical and oxidative stress responses were assessed in brain, gills, and liver tissues, including lipid damage, glutathione levels, enzyme activities, and antioxidant competence. Muscle and brain acetylcholinesterase activity (AChE) and stable isotopes of 13C and 15N in muscle were also measured. The lowest IVM treatment resulted in an increase in brain lipid peroxidation, as measured by thiobarbituric acid reactive substances (TBARs), decreased levels of reduced glutathione (GSH) in gills and liver, increased catalase activity (CAT) in the liver, and decreased antioxidant capacity against peroxyl radicals (ACAP) in gills and liver. The highest IVM treatment significantly reduced GSH in the liver. Muscle (AChE) was decreased in both treatments. Multivariate analysis showed significant overall effects in the liver tissue, followed by gills and brain. These findings demonstrate the sublethal effects of IVM in P. lineatus, emphasizing the importance of considering sediment contamination and trophic habits in realistic exposure scenarios.

Updated distribution and morphological variation of the genus Pseudanos in the Río de la Plata basin (Characiformes: Anostomidae).

Pseudanos is a fish genus with cis-Andean distribution in South America. Pseudanos trimaculatus is originally known from the Amazon and Orinoco basins. Three decades ago, a few specimens collected in the Río de la Plata basin were identified as P. trimaculatus, what remained to be confirmed and understood. The aim of this contribution is to analyze these specimens. Consequently, the morphological variation of P. trimaculatus is discussed and updated. Morphometric and meristic data were taken from the specimens and compared with those of the type and non-type specimens of the species. Multivariate analyses of the size-corrected measurements were used to explore the morphological variation. Size-corrected PCA revealed that the specimens collected in the Río de la Plata basin nested with the remaining specimens, being slightly closer to those from the Guaporé, Napo and Uatumã rivers. Measurements such as caudal peduncle depth, body depth, and body width affected more heavily the first components. Cluster analysis did not show well-defined groups based on the hydrogeographic basins. The studied specimens from the Río de la Plata basin are herein confirmed as conspecific with P. trimaculatus. The species is added to the list of fish species shared between the Amazon and Río de la Plata basins.

Contribución al conocimiento limnológico de moluscos pelecipodos en la Cuenca del Plata, con particular referencia a sus relaciones tróficas

Despite the undeniable limnological importance o f the malacological fauna in the waters o f Rio de la Plata Basin, the current knowledge on this topic is very poor, fragmentary and geographically limited. Moreover existing limnological literature generally focuses on their very complex taxonomic problems.
 Thus, this paper conceived on the basis o f available literature, unpublished data and our own research, represents a first attemt to bring together the most significant limnological Information related to the mollusks o f the above mencioned basin and to begin with, the pelecipod s. Also it intends to provide as far as posible a complete and integrative panorame of the role o f different species in its participation in trophic nets, specially those dealing with the fish and físheries. The effect and possible future consequences of the invasión on this waters by species o f the genus Corbicula, are also considered.

African Legume Affinities with the Flora from the Lower la Plata Basin (Upper Cenozoic), South America

Este artículo presenta un análisis de las afinidades de las leguminosas del Cenozoico superior, halladas en la cuenca baja del Plata (América del Sur), con géneros africanos actuales, y sus implicancias paleoecológicas y paleofitogeográficas. Maderas permineralizadas, asignadas a Entrerrioxylon victoriensis de la Formación Paraná (Mioceno Superior), Gossweilerodendroxylon palmariensis y Paraoxystigma concordiensis de la Formación El Palmar (Pleistoceno Superior) y (Cylicodiscuxylon paragabunensis) de la Formación Arroyo Feliciano (Pleistoceno Superior), presentan afinidades con taxones actuales de Detarioideae y Caesalpinioideae (clado mimosoide). Actualmente, los taxones asignados a Detarioideae se distribuyen principalmente en las regiones tropicales de África, América Central y América del Sur y el género monotípico Cylicodiscus está restringido a África occidental desde Sierra Leona hasta Gabón. En la actualidad, Cylicodiscus, Gossweilerodendron y Oxystigma no están distribuidos en América del Sur, lo que implica que en el pasado tuvieron una mayor distribución y que se extinguieron en esta región en algún momento durante el Pleistoceno–Holoceno, presumiblemente relacionado con los cambios climáticos que ocurrieron durante este intervalo de tiempo. El registro fósil de la cuenca baja del Plata con taxones relacionados a Detarioideae y Cylicodiscus respalda una distribución fitogeográfica más amplia durante el Cenozoico y una vinculación antigua con los bosques tropicales de África occidental.

A retrospective overview of zooplankton research in Uruguay

With 6 main basins, and being the second smallest country in South America, Uruguay has a high freshwater ecosystem diversity. The study of zooplankton communities dates back to 1949, but remained marginal until the end of the 20th century when the number of publications increased notably. Here, we revise the history and accumulated knowledge on the zooplankton community in Uruguayan continental ecosystems, highlighting the main approaches and milestones. So far, ca. 100 academic papers with 219 authors have been published in international, regional, and local journals, accumulating more than 2150 citations. Most of the published studies come from shallow lakes, followed by reservoirs and estuaries, and were concentrated in the southern part of Uruguay. Most taxonomic records correspond to the Río de la Plata basin, followed by the Atlantic Ocean basin, and the Río Uruguay basin. The number of records in the rest of the country is comparatively low, with minima occurring in the basins of the rivers Negro and Santa Lucía. A total of 170 species belonging to 117 genera have been recorded, mainly for Copepoda, Cladocera and Rotifera. Limnological studies in Uruguay have historically followed an ecosystemic approach, thus, most of the literature referring to zooplankton has such a perspective. The most relevant ecological aspects analyzed so far include trophic interactions, species survival and dispersion, biological invasions, the relationship with eutrophication and climatic variability, and have applied traditional as well as functional and trait-based approaches. Our analysis allowed us to detect important knowledge gaps, that warrant attention for future studies which can help elucidate local and regional processes in freshwater zooplankton in Uruguay.

Sedimentation in the adjacencies of a southwestern Atlantic giant carbonate ridge

Although carbonate mounds have been investigated for 100 years, few studies focus on the giant variety. The Alpha Crucis Carbonate Ridge (ACCR), a ~17 x 12-km ring-shaped ridge formed by hundreds of mounded structures, located between the 300 and 800-m isobaths and reaching a maximum height of 340 meters above the adjacent seafloor, is the first giant carbonate mounded feature described for the SW Atlantic margin. This study provides the first multiproxy approach to investigate sediments covering the ACCR and its adjacencies. Most of the area is located under the Intermediate Western Boundary Current (IWBC) flow, which carries the nutrient-rich Antarctic Intermediate Water (AAIW). Radiocarbon aging shows pronounced differences for the shallow layers (MIS3 for the top of the mounds and late Holocene for the adjacencies). Grain size data indicate the prevalence of sandy fractions on top of the mounds and muddy sediments in the adjacent areas. Fe/Ca and Ti/Ca proxies allowed for identifying mainly biogenic sedimentation in the area. However, the input of allochthonous terrigenous sediment is necessary for mound buildup, and values of Fe and Ti collected on the top of the mounds are significant. End-Members distributions and metal concentrations also allowed for recognition of distinct sources of sediment. εNd and Ln(Fe/K) indicated two primary terrigenous sources, the Precambrian rocks of the Brazilian shield (Cabo Frio end-member) and the multiple lithologies drained by the Rio de la Plata basin. Redox condition proxies indicated that the area is submitted to oxic conditions, probably reflecting the action of the IWBC. This work provides the first insight into an integrated grain-size and geochemical characterization of the Alpha Crucis Carbonate Ridge (southwestern Atlantic margin).

Metabolic Disrupting Effects of Polychlorinated Biphenyls Revealed by Long-Term Temporal Variations of Lipids in Detritivorous Fish from the Rio de la Plata Basin.

The long-term covariation (2002-2017) of lipids, polychlorinated biphenyls (PCBs), and sewage tracers was studied in the detritivorous fish (Prochilodus lineatus) and settling detritus from the Rio de la Plata. Fatty fish from polluted Buenos Aires area (BA) exhibited a significant decrease of muscle lipids (71 ± 12 to 29 ± 8.6% dry weight; p < 0.0001), triglycerides (94 to 85%, p < 0.001), and 18 carbon fatty acids (18C-FA: 59 ± 4.8 to 48 ± 1.4%; p < 0.01), reflecting a reduction of lipid accumulation, largely triglycerides enriched in 18C-FA, with a concomitant ∼20-times decline of PCBs (∼20 to >1 μg g-1 dw). The 2017 individuals of the BA series converged with leaner and more pristine northern fish (N), which showed no significant temporal variation (20 ± 10% lipids, 67 ± 8.7% triglycerides, 41 ± 8.1% 18C-FA, and 0.22 ± 0.42 μg g-1 dw PCB). In contrast, the fecal sterol tracer coprostanol remained abnormally higher in BA fish muscle with no significant temporal trend (120 ± 102 vs 6.6 ± 10 μg g-1 dw or 4.4 ± 2.8 vs 0.63 ± 1.2% sterols at N). The same pattern was observed in BA settling detritus, i.e., a temporal decrease of PCBs with high, stable coprostanol concentrations denoting sustained sewage inputs, while northern detritus was enriched in plant sterols. This long-term covariation of lipids and PCBs in fish muscle from polluted BA converging with more pristine and homogeneous northern specimens while maintaining a sewage-derived diet provides rare field evidence of the declining effect of PCBs controlling the temporal variation of muscular lipids in fish.

Holocene settlement, stratigraphy and chronology at the site of Uruguai 1-sector 1, Foz do Chapecó archaeological area, South Brazil

Uruguai 1 is a recently discovered site in the Foz do Chapecó Archaeological Area, which contains an exceptional archaeological record, documenting the expansion of Homo sapiens in southern Brazil, within the Rio de la Plata basin. The aim of this paper is to present the results of field investigations within sector 1 of the site, providing a detailed description of the entire stratigraphic sequence that spans the Pleistocene-Holocene transition to the present day. The site comprises a variety of archaeological evidence including six archaeological levels (palaeosurfaces), evidenced by lithic tools, charcoal horizons, combustion features, small faunal remains and, for the youngest one, ceramic fragments. The overlapping of six archaeological levels in an open-air stratigraphic context is unprecedented in inland of southern Brazil and provides evidence for a long-term human presence in the area, which is of great archaeological importance in the southern part of South America..

Variación anual de larvas del mejillón dorado (Limnoperna fortunei) en sistemas de refrigeración de centrales hidroeléctricas en embalses del Río Negro, Uruguay

Limnoperna fortunei (golden mussel) is an alien mollusk in the Plata basin and is native from the Southeastern Asia. Its benthic patches generate macrofouling in hydraulic installations causing additional costs to the affected companies. The objective of this work is to determine the variation of abundance and the size of the valves larval stages of the golden mussel, establishing associations with the water quality parameters in the cooling systems in the three hydroelectric power stations (HP) of the reservoirs of the Negro River (Uruguay) that has been invaded by the species. In the three cooling systems the golden mussel larval density average showed associations with temperature of the water and the percentage of organic material of the column water. Larger larval abundances were registered during warm and minimum during cold months. For the three systems, is suggested a reproductive pause of the species at water temperatures lower than 18ºC and the start of the larval cycle at higher values. The Velíger larvae type D and preumbonate Veliger stages were the dominant stages. In terms of the golden mussel settlement the HP Constitución cooling system was the most exposed. It highlights the need to continue deepening in the knowledge of L. fortunei in order to better implement control and mitigation measures for the species.

Climate hazard indices projections based on CORDEX-CORE, CMIP5 and CMIP6 ensemble

The CORDEX-CORE initiative was developed with the aim of producing homogeneous regional climate model (RCM) projections over domains world wide. In its first phase, two RCMs were run at 0.22° resolution downscaling 3 global climate models (GCMs) from the CMIP5 program for 9 CORDEX domains and two climate scenarios, the RCP2.6 and RCP8.5. The CORDEX-CORE simulations along with the CMIP5 GCM ensemble and the most recently produced CMIP6 GCM ensemble are analyzed, with focus on several temperature, heat, wet and dry hazard indicators for present day and mid-century and far future time slices. The CORDEX-CORE ensemble shows a better performance than the driving GCMs for several hazard indices due to its higher spatial resolution. For the far future time slice the 3 ensembles project an increase in all temperature and heat indices analyzed under the RCP8.5 scenario. The largest increases are always shown by the CMIP6 ensemble, except for Tx > 35 °C, for which the CORDEX-CORE projects higher warming. Extreme wet and flood prone maxima are projected to increase by the RCM ensemble over the la Plata basin in South America, the Congo basin in Africa, east North America, north east Europe, India and Indochina, regions where a better performance is obtained, whereas the GCM ensembles show small or negligible signals. Compound hazard hotspots based on heat, drought and wet indicators are detected in each continent worldwide in region like Central America, the Amazon, the Mediterranean, South Africa and Australia, where a linear relation is shown between the heatwave and drought change signal, and region like Arabian peninsula, the central and south east Africa region (SEAF), the north west America (NWN), south east Asia, India, China and central and northern European regions (WCE, NEU) where the same linear relation is found for extreme precipitation and HW increases. Although still limited, the CORDEX-CORE initiative was able to produce high resolution climate projections with almost global coverage and can provide an important resource for impact assessment and climate service activities.

The Jesuit-Guarani towns in the Rio de la Plata basin. Putting in value water-related practices (in Spanish)

The Jesuit-Guarani towns in the Rio de la Plata basin. Putting in value water-related practices (in Spanish)

Accumulation of human pharmaceuticals and activity of biotransformation enzymes in fish from two areas of the lower Rio de la Plata Basin

The accumulation of four human pharmaceuticals active compounds (HPhAC) in the muscle of four fish species of the Rio de la Plata Basin were assessed regarding the compound logP and pKa, and fish trophic levels. For Prochilodus lineatus, accumulation was compared to hepatic biotransformation enzymes and fish from two sampling areas with different urbanization degree. Species were the detritivore Prochilodus lineatus, the omnivores Megaleporinus obtusidens and Pimelodus maculatus, and the piscivorous Salminus brasiliensis. Sampling areas were the Inner Rio de la Plata Estuary (RLP), in front of the Buenos Aires Metropolitan Area, and at the Lower Uruguay River (URU), a relatively unpopulated area. Carbamazepine, atenolol, enalapril, and sildenafil concentrations in fish muscle were analyzed by HPLC-MS. EROD, BROD, and GST activities were measured in P. lineatus liver. Average (maximum) concentrations and detection frequency were: Atenolol 24.4 (69.4) μg kg−1, 60%; carbamazepine 5.5 (45.8) μg kg−1, 19%; enalapril 7.0 (56.9) μg kg−1, 28%; sildenafil 17.1 (71.6) μg kg−1, 56%. Enalapril and sildenafil detection in fish was first-time reported. Atenolol and carbamazepine concentrations were positively correlated. No correlation was observed between HPhAC accumulation and logP or pKa. A potential biomagnification trend was observed for atenolol, showing higher accumulation in S. brasiliensis. HPhACs accumulation was higher for P. lineatus collected at URU, but GST and BROD were significantly higher for individuals sampled at RLP and were positively correlated. A significant negative correlation was observed for enalapril and BROD. The study contributes to the knowledge of the accumulation of HPhACs in fish.

Rapid freshwater discharge on the coastal ocean as a mean of long distance spreading of an unprecedented toxic cyanobacteria bloom

Cyanobacterial toxic blooms are a worldwide problem. The Río de la Plata (RdlP) basin makes up about one fourth of South America areal surface, second only to the Amazonian. Intensive agro-industrial land use and the construction of dams have led to generalized eutrophication of main tributaries and increased the intensity and duration of cyanobacteria blooms. Here we analyse the evolution of an exceptional bloom at the low RdlP basin and Atlantic coast during the summer of 2019. A large array of biological, genetic, meteorological, oceanographic and satellite data is combined to discuss the driving mechanisms. The bloom covered the whole stripe of the RdlP estuary and the Uruguayan Atlantic coasts (around 500 km) for approximately 4 months. It was caused by the Microcystis aeruginosa complex (MAC), which produces hepatotoxins (microcystin). Extreme precipitation in the upstream regions of Uruguay and Negro rivers' basins caused high water flows and discharges. The evolution of meteorological and oceanographic conditions as well as the similarity of organisms' traits in the affected area suggest that the bloom originated in eutrophic reservoirs at the lower RdlP basin, Salto Grande in the Uruguay river, and Negro river reservoirs. High temperatures and weak Eastern winds prompted the rapid dispersion of the bloom over the freshwater plume along the RdlP northern and Atlantic coasts. The long-distance rapid drift allowed active MAC organisms to inoculate freshwater bodies from the Atlantic basin, impacting environments relevant for biodiversity conservation. Climate projections for the RdlP basin suggest an increase in precipitation and river water flux, which, in conjunction with agriculture intensification and dams' construction, might turn this extraordinary event into an ordinary situation.

Estrategias indígenas de captura y manejo del ganado cimarrón en las Sierras Septentrionales bonaerenses: las construcciones de piedra Cerro Guacho I y Cerro Guacho II

This paper contributes to the analysis of capture, handling and care practices of introduced livestock carried out by the indigenous groups that inhabited the Tandilia mountain range during the post Spanish period, while they still kept their territorial autonomy. This period of the regional history begins with the arrival of the Spaniards to the Rio de la Plata basin in the 16th century and ends with the Creole’s society occupation of that area, that consolidated towards the middle of the next century. From a review of anthropological and historical production about the transformations in the indigenous economy linked to the incorporation of domestic livestock, some proposals concerning the functioning of poles of specialized activities are considered. In particular, the results of our archaeological investigations developed in the central portion of Tandilia are presented, focusing on two drystone wall constructions called Cerro Guacho I and Cerro Guacho II. It is discussed the use of both sites as places of capture and safeguard of wild horses, sheep enclosures, human rooms and monitoring points, on the basis of the information collected from several documentary sources, along with cartography and the material evidence.

Bioaccumulation of 10 trace elements in juvenile fishes of the Lower Paraná River, Argentina: implications associated with essential fish growing habitat.

This study assessed the concentration, bioconcentration, and bioaccumulation of As, Cd, Co, Cr, Cu, Mg, Mn, Ni, Pb, and Zn in juvenile fishes (Acestrorynchus pantaneiro, Brycon orbygnianus, Cyphocharax voga, Megaleporinus obtusidens, Odontesthes bonariensis, Pimelodus maculatus, Prochilodus lineatus, Salminus brasiliensis, and Schizodon borelli) in the Lower Paraná River (Argentina), the most extensive floodplain from the Plata Basin. The floodplain is crucial for the reproduction and growth of various species such as P. lineatus, M. obtusidens, and S. brasiliensis, which complete their life cycle in this environment. In total, 90 individuals were sampled for nitrogen stable isotope, and trace element analysis in muscle tissue, water, and sediment was analyzed. The results show that all the studied species bioaccumulate Cr, Mg, Ni, and Zn. In particular, B. orbygnianus and P. maculatus presented the highest bioaccumulation factor for Cr. A biodilution of Co through the food chain was observed. No positive correlation was found between element concentration and trophic level, but we observed significant differences between trophic guilds (herbivorous, omnivorous, and carnivorous). Our findings suggest that feeding habits determine trace element concentrations. To establish differential behavior between different species within the aquatic web further studies are necessary, particularly in the floodplain of the Paraná, which is a crucial nursery area for most commercially important fishes from the Plata Basin. Graphical abstract.

Asentamientos europeos en la cuenca del Río de la Plata:

Las investigaciones arqueológicas acerca de los primeros asentamientos establecidos por la Corona Española en la margen derecha de la cuenca del Plata se han enfocado, principalmente, en los emplazamientos de Sancti Spiritus (1527) y de Nuestra Señora de Santa María de Buen Ayre (1536). La tercera ocupación fue la deCorpus Christi,fundada por Juan de Ayolas en 1536,en tierras cercanas a la actual laguna Coronda (Santa Fe, Argentina). Si bien en los documentos históricos de la época son numerosas las menciones que refieren a Corpus Christi, no proveen mayoresprecisiones sobre su ubicación geográfica.En consecuencia, su localización exacta es aún desconocida. En este trabajo, se realiza un análisis críticode fuentes escritas primarias del siglo XVI, con el objetivo deformular hipótesis acerca de su funcionamiento ydel tipo de registro arqueológico generado, así como también acotar áreas de su posible localización.

Assessment of the efficiency of controls to prevent biologic invasions at the San Lorenzo Port, Argentina.

The problem created by invasive non-native species through ships' ballast water has caused the International Maritime Organization (IMO), through the Ballast Water Management (BWM) Convention and many countries to develop their own laws to prevent their introduction. One of the most important non-native species in Argentina, the golden mussel (Limnoperna fortunei), causes a significant economic impact on the Plata Basin. Argentina has a great amount of maritime and fluvial ports that receive ships from different regions of the world. Particularly, the San Lorenzo-San Martín Port Complex (here termed SLOR), placed in the terminal portion of the Paraná Basin, receives ocean ships with great loading capacity, which increases the possibility of invasions and the need of an adequate environmental management. This work proposes to estimate the potential vulnerability of SLOR port, in relation with the origin of the ballast water and its volume. For this purpose, an adaptation of the risk assessment model of the GloBallast Program was used. The results suggest that SLOR has important similarities with different fluvial ports of the world, especially in Brazil and China. However the amount of ships coming from the nearest estuary waters, where the diversity of invasive species has major effects, is also important. This article provides the necessary information to conduct the efforts through surveys and enforcement regulations, and could be the foundation for future research using global data that could provide basic information for other fluvial ports with similar features.

Comprehensive evaluation of metal pollution and ecological risk in settling material from differently impacted sites in the Río de la Plata basin

Metal speciation, geoaccumulation indices and sediment quality guidelines were used to evaluate the ecological risk of metals in settling material from the polluted metropolitan Buenos Aires coast in the Río de la Plata (RLP) compared to a more pristine northern site in the Uruguay River (UR). The content of organic carbon and trace metals (Zn, Cr, Cu, Pb and Ni) in RLP was 2-6 times higher reflecting the anthropogenic impact in the metropolitan coastal area. In contrast, Fe and Mn were 4-5 times lower, reflecting basically redox-driven evasion from polluted anoxic settling material. In addition, at RLP, trace metals were mainly found in the potentially bioavailable fractions (51-84%) compared to the prevailing, immobile residual fractionation at UR (63-86%), while Fe and Mn displayed a similar fractionation at both sites (Fe: 86-90% in the residual fraction; Mn: 71-82% in non-residual fractions). The geoaccumulation index relative to local background values (Igeo), the effects-based sediment quality guidelines (SQG) and the risk assessment code (RAC) from speciation data revealed some discrepancies in the risk evaluation. Although concentrations of Zn, Cr, Cu and Pb in RLP were enriched compared to background concentrations (1 ≤ Igeo ≤ 2) and exceed SQGs for the protection of aquatic life, according to RAC, only Zn, Mn and, to a lesser extent, Ni presented probable risks for the aquatic environment.