Rio De La Plata Basin Research Articles

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.

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.

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..

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.

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.

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.

Alterations in the sterol signature of detritivorous fish along pollution gradients in the Río de la Plata basin (Argentina): From plant to sewage-based diet

In order to assess the impact of sewage pollution on the diet of the strict detritivorous and migratory South American fish, Prochilodus lineatus, 16 sterol biomarkers were analyzed by gas chromatography-mass spectrometry from fish muscle (n: 144) collected along 1200 km in the Rio de la Plata basin. Sterol concentrations were fairly homogeneous (2.4 ± 1.3 mg g−1 dry weight), but their proportion in lipids was highly variable and inversely related to both body mass and lipid contents, reflecting the more conservative character of sterols compared to the rapid accumulation of fat as fish grows. As expected, the muscle sterol signature was widely dominated by cholesterol (92 ± 4.5% of total sterols), but it exhibited a remarkable diversity with variable proportions of fecal coprostanol (4.0 ± 4.4%) and plant sterols (3.1 ± 1.9%, e.g. sitosterol and campesterol). Muscle sterols exhibited contrasting geographical differences associated with dietary shifts from plant-derived detritus in the northern reaches of the basin (N: Paraná and Uruguay Rivers), to sewage dominated inputs at Buenos Aires (BA). Fish from BA are fattier (lipids: 35 ± 18 vs. 15 ± 9.0% at N), with higher total sterol contents (2.6 ± 1.3 vs. 1.9 ± 1.0 mg g−1), abundant coprostanol (5.3 ± 4.4 vs. 0.46 ± 1.1%) and lower plant sterols (2.6 ± 1.6 vs 4.6 ± 2.0%), reflecting a diet shifted to anthropogenic organic matter as opposed to vegetal detritus in the north. Accordingly, BA fish presented lower phyto/fecal sterol ratios (0.37 ± 0.21 vs. 0.91 ± 0.12 at N) and higher copro/epicoprostanol ratios (0.95 ± 0.082 vs 0.51 ± 0.25 at N), indicating fresh fecal inputs which provide a valuable supply of easily absorbed organic matter at this site. In addition, the sterol signature allowed to distinguish migratory fish from BA collected 900 km north (previously identified by their pollutant fingerprint and biochemical composition). In fact, coprostanol concentrations show a direct relationship with human populations along the basin, highlighting the usefulness of fecal sterol biomarkers as tracers of polluted fish stocks.

RIO DE JANEIRO AND THE SILVER MINING ECONOMY OF POTOSI: TRANS-IMPERIAL, GLOBAL, AND CONTRACTUAL APPROACHES TO SOUTH ATLANTIC MARKETS (18TH CENTURY)

Abstract This paper’s main goal is to advance some considerations on the interrelations between port cities and capital. More specifically, it sheds light on how these interdependencies took place in the eighteenth-century Portuguese and Spanish Atlantic world. This paper thus seeks to draw an urban political economy in transimperial, global, and contractual perspectives. For so doing, particular attention will be put to Rio de Janeiro’s projection far beyond the South Atlantic, and in particular, its interconnections with the Rio de la Plata basin and Potosi markets. Attention will also be paid to the impact of and repercussions that far-flung economic phenomena had for the urban domestic markets.

Creating hybrid scientific knowledge and practice: the Jesuit and Guaraní cultivation of yerba mate

ABSTRACTThe drinking of yerba mate tea has become a common symbol of southern South American culture and many studies have explored the economic and social history of yerba mate in Argentina, Paraguay, and southern Brazil. The consumption of yerba mate has its roots in Guaraní culture and practice, and, at the time of European contact, the Guaraní had developed effective practices of harvesting and processing the leaves. The tree is native to different forest types of the Rio de la Plata Basin and its exploitation by the Spanish occurred mainly through natural forest stands from the sixteenth to the twentieth century. Nevertheless, the Jesuit missionaries in colonial Paraguay successfully developed the technology to plant yerba mate in forest stands around the mission towns. This not only stabilized their production but also represented the domination of European scientific knowledge and practice on the untamed wilderness of the Rio de la Plata Basin. This article examines how Jesuit discourse surrounding the invention of this technology masks the very active participation of the Guaraní in developing and testing this scientific practice. The process of cultivation and “civilization” of the wild environment and people of the Americas by the Jesuits was not one sided, but it was rather a hybrid construction of knowledge and technology that actively involved both the Guaraní and the Jesuit Fathers, creating new knowledge and understandings of the forest environment.

State formation and identity: Historiographical trends concerning South America's War of the Triple Alliance

AbstractThe War of the Triple Alliance shaped state formation in the Rio De La Plata Basin during the second half of the 19th century. Historians have long debated how emerging countries could have endured such protracted periods of fighting. Recently, however, historiography has moved away from patriotic and military accounts and towards social and political analyses of civilian responses to the bloodbath. These responses had profound consequences for the fragile regional order postindependence. Paraguay, the loser, suffered unspeakable destruction. However, the political systems of the winners, Brazil, Argentina, and Uruguay, were also challenged as initial popular enthusiasm succumbed to the difficult requisites of war. This paper explores how historians have dealt with political, cultural, and demographic changes as war support and resistance waxed and waned over time in the belligerent countries. The war demanded the utmost sacrifices from civilians and soldiers, and their responses created new national identities throughout the Rio de la Plata Basin.

Floración excepcional de cianobacterias tóxicas en la costa de Uruguay, verano 2019

Cyanobacterial toxic blooms are a worldwide problem. In Rio de la Plata basin, anthropic eutrophication and dam construction have promoted an increase in cyanobacteria blooms, especially those of the Microcystis aeruginosa complex (CMA). Here, we describe the exceptional blooms observed in the summer of 2019 on the coast of Rio de la Plata and Atlantic coast of Uruguay. We discuss the main driving mechanisms using biological, meteorological and oceanographic sampling data, satellite images and reanalysis. The blooms covered a wide surface (Carmelo to Rocha; 500 km) and were persistent in time (ca. 4 months). Blooms were generated by CMA organisms having similar genetic structure and were associated to quantifiable and high microcystin concentrations. Given the observed oceanographic conditions and the similarity in organisms traits, we hypothesized that blooms had a common origin, probably associated with zones with high nutrient concentrations and high water residence time in the lower Rio de la Plata basin. Extreme precipitations induced high water flows that transported cyanobacteria blooms downstream. In addition, anomalous wind and temperature conditions facilitated their arrival to the Atlantic coast along Rocha, to environments with particular relevance for biodiversity and conservation (e.g. Rocha coastal lagoon).

Human pharmaceuticals in three major fish species from the Uruguay River (South America) with different feeding habits

The accumulation of 17 human pharmaceuticals (HPs) was investigated in the muscle of three fish species characteristic of the “Rio de la Plata Basin” with different feeding habits and of relevance for human consumption: Megaleporinus obtusidens, Salminus brasiliensis, and Prochilodus lineatus. Fish were sampled in fall and spring from 8 localities distributed along 500 Km of the Uruguay River. Atenolol and carbamazepine were the most frequently detected HPs (>50%), but at concentrations always below 1 μg/kg wet weight (w/w). Hydrochlorothiazide, metoprolol, venlafaxine, propranolol, codeine, and the carbamazepine metabolite, 2-hydroxycarbamazepine, were accumulated at higher levels showing maximum concentrations between 1 and 10 μg/kg (w/w), but infrequently (<50%). The other HPs were always below 1 μg/kg (w/w) and at frequencies lower than 50%. Distinctive accumulation patterns were observed among species at different trophic levels. However, biomagnification trends were not identified for any compound. The highest number and concentration of HPs were found in M. obtusidens (omnivorous), followed by P. lineatus (detritivorous), and lastly S. brasiliensis (piscivorous). The most recurrent HPs (i.e. carbamazepine and atenolol) were present in all species, but others exclusively in one. Geographical variations were only found for carbamazepine and atenolol in M. obtusidens and P. lineatus, showing higher concentrations in localities closer to the Rio de la Plata estuary. Differences in the HPs concentrations among seasons were not identified. Acceptable daily intake and predicted no effect concentrations would indicate that measured muscle concentrations in fish from the Uruguay River do not pose a serious risk for human consumption nowadays. Further studies will be necessary for assessing the potential adverse effects on studied fish species.

Early diagenetic alterations of sterol biomarkers during particle settling and burial in polluted and pristine areas of the Rio de la Plata Basin

Sources and diagenetic alterations of sterol markers were studied in settling material and sediments near the Buenos Aires main sewer (BA), and at a relatively non-polluted northern site at the Uruguay River (N). Vertical particle fluxes were 7-times higher at BA relative to N (34 ± 24 vs 4.6 ± 3.6 mg/cm2/day; mean ± standard deviation), increasing during rainy months. Total sterol contents were consistently higher at BA, both in settling material (7140 ± 7905 vs 41 ± 47 μg/g at N) and sediments (708 ± 454 vs 1.9 ± 0.18 μg/g). This difference was further amplified in the vertical flux of sterols (116 ± 168 vs 0.070 ± 0.13 mg/cm2/year). At BA, sterol composition of settling material and sediments was dominated by fecal sterols (75–77%), with extreme coprostanol concentrations (3.6 ± 4.8 vs 0.35 ± 0.28 mg/g at N) which are similar to sewage sludge. In contrast, at N the sterol profile was dominated by plant sterols (57–64%), mainly sitosterol, stigmasterol and campesterol. At BA the discharge of fresh sewage was confirmed by the high coprostanol/(coprostanol + epicoprostanol) ratio. At N, the overwhelming dominance of plant sterols over herbivore fecal sterols was reflected by the high sitosterol/(sitosterol + 24-ethylcoprostanol) ratio and the low coprostanol/(coprostanol + 24-ethylcoprostanol) ratio. The coprostanol/(coprostanol + epicoprostanol) and cholesterol/(cholesterol + cholestanol) ratios were lower in sediments than in settling material, reflecting the sterol degradation at the sediment surface. The accumulation efficiencies, calculated as the difference between trap fluxes and sediment inventories, were 2–7 times higher at BA reflecting strong vertical fluxes and enhanced preservation under anoxic conditions. During diagenetic processes, epicoprostanol (partially produced in situ), cholestanol and plant sterols were the best-preserved sterols, while cholesterol was the most labile during burial.

Dieta de Pomacea canaliculata (Gastropoda: Ampullariidae) en su hábitat natural basada en análisis de contenidos digestivos e isótopos estables

Pomacea canaliculata is native to Rio de la Plata basin, and it is invasive in most of South and Southeast Asia after accidental introduction during unsuccessful attempts to establish commercial aquaculture of this species, and being present, the number one pest of rice crops in the region. Investigations in its native habitat are still needed because fundamental issues of its trophic ecology remain unknown. The aim of this research was to study the diet of P. canaliculata in its natural habitat through gut content techniques and stable isotopes of 13C and 15N. Biological samples were taken from November 2009 to December 2010 in Carnaval stream, a characteristic Pampean stream. Samples for stable isotopes of 13C and 15N using of a mixing model were collected in November 2011. The trophic strategy diagram evinced a generalist diet with high consumption of detritus followed by the vascular plants and algae. The mixing model results indicated that the relative contribution to the diet was similar for all basal resources: fine and coarse particulate organic matter, epipelon and aquatic macrophytes (approximately 40 %). These results evidenced a strong dietary plasticity for the species.

Reflexiones sobre el rol del Mercosur en la protección ambiental de los recursos acuáticos y marinos

El presente articulo reflexiona sobre el rol que el Mercado Comun del Sur (en adelante, MERCOSUR) podria desarrollar en lo concerniente a la proteccion juridica ambiental de los recursos acuaticos y marinos. En primer lugar, se analiza el estado de situacion de la regulacion vigente a nivel general que ha dictado el MERCOSUR. En segundo lugar, se focaliza en la regulacion ambiental y especificamente en la de los recursos acuaticos y marinos que ha producido el MERCOSUR. En relacion con la regulacion de los recursos acuaticos, a continuacion se estudia la normativa correspondiente a la Cuenca del Plata, ya que ocupa un espacio geografico similar al del MERCOSUR. La hipotesis sostiene que el MERCOSUR como institucion ha avanzado algunos pasos en la regulacion de la proteccion ambiental en general, especialmente con la sancion del Acuerdo del Medio Ambiente, pero resta todo el camino por recorrer en cuanto a la proteccion especifica ambiental de los recursos tanto acuaticos como marinos.

Um breve histórico das araras do gênero Anodorhynchus Spix, 1824 (Aves, Psittaciformes)

Since the Antiquity, parrots, parakeets and their relatives (Psittacidae) aroused a great interest in Europe, both for their colours as for their notorious capacity of interacting with human beings. With the discovery of the Americas, new species would be introduced in the traffic of exotic animals a long time ago established by Europeans with Africa and the East. Effectively, even before Columbus finished his fourth and last voyage (1502-1504), neotropical parrots had already made their appearance in chronicles, in the cartography and the fine arts. Although the oldest notices about blue macaws of the genus Anodorhynchus date from the end of the 16th century, and the first image from the beginning of the 17th century, those birds would be better known by Europeans only in the second half of the 18th century. In a general way, the sources examined herein proved to be especially significant for Anodorhynchus glaucus , as all the first hand information about the biology and the behavior of this macaw are registered in testimonies prior the 20th century. It is not impossible to suppose, therefore, that further details about this species and a better understanding of its mysterious disappearance could be obtained from the perusal of the vast documentary collection about the Rio de la Plata basin left by Jesuits, as well as from a more accurate reading of the reports by travelers and naturalists which, such as Friedrich Sellow and Auguste de Saint Hilaire, journeyed through Argentina, Paraguay, Uruguay, and southern Brazil.

Effects of suspended inorganic matter on filtration and grazing rates of the invasive musselLimnoperna fortunei(Bivalvia: Mytiloidea)

The Asian mytiloid Limnoperna fortunei (Dunker, 1857) was first recorded in South America along the coast of the Rio de la Plata estuary in 1991 (Pastorino et al., 1993). Since then the mussel has expanded its range, colonizing most of the Rio de la Plata basin, as well as several minor watersheds. Because of its wide distribution, high densities and significant ecosystem engineering capabilities, L. fortunei has had sizeable impacts on the waterbodies colonized, including modification of nutrient concentrations and ratios, enhancement of water transparency, macrophyte growth and effects on cyanobacterial blooms, the abundance and diversity of benthic invertebrates, sedimentation rates and food availability for fishes (Sylvester, Boltovskoy & Cataldo, 2007; Boltovskoy et al., 2009, 2013; Cataldo et al., 2012a, b; Boltovskoy & Correa, 2015; Paolucci & Thuesen, 2015). Impacts on human activities have been especially marked: L. fortunei larvae enter raw water conduits of open cooling systems and develop large beds in pipes and other components, clogging them and causing pressure loss, overheating and corrosion (Boltovskoy, Xu & Nakano, 2015). Northward expansion of L. fortunei is expected to continue beyond South America and into Central and North America (Karatayev et al., 2015). Available data indicate that potentially colonizable areas include all continents except Antarctica (Kluza & McNyset, 2005; Karatayev et al., 2015), but the fact that water bodies lacking mussels exist in watersheds where L. fortunei has been present for decades suggests that some environmental conditions may limit the expansion of this invader (Darrigran et al., 2011). Among these, the concentration of suspended solids is of particular interest. Suspended matter can affect respiration, growth, parasite infestation and reproduction of the organisms (Robinson, Wehling & Morse, 1984; Alexander, Thorp & Fell, 1994; Rosewarne et al., 2013), thereby restricting their geographic spread, but this constraint has not been explicitly addressed in models of the potential distribution of L. fortunei (Kluza & McNyset, 2005;Oliveira, Hamilton & Jacobi, 2010). In order to estimate the tolerance of L. fortunei of inorganic suspended solids, thus providing data for analysis of its potential distribution worldwide, we assessed the species’ capability of filtering water and retaining phytoplankton at different clay concentrations. Individuals of L. fortunei were collected from Buenos Aires (348320S; 588250W) and stored in aerated aquaria filled with dechlorinated tap water at 23–25 8C. They were fed ad libitum on cultured algae (.95% Scenedesmus spp., mean biovolume 1300–1600 mm) known to be actively consumed by the mussel (Cataldo et al., 2012a). Individuals 15–20 mm (mean 17.3 mm) in shell length were isolated from the clumps and placed in flat trays in order to verify their vitality. Actively filtering individuals were transferred from the trays to acclimation vessels at 27 8C for 48 h. All individuals were starved for 24 h and then stocked in cylindrical plastic netting cages (10 cm high, 6 cm in diameter) placed at mid-depth in the experimental 2-l containers (Fig. 1). In the latter, an air hose was attached laterally to a tube located vertically on the bottom, thereby suctioning settling sediment particles and returning them to the water column (Fig. 1). Algal concentrations in the experimental containers ranged from 30 to 60 (mean 43.5+6.3 SE) mg Chl a l, mimicking usual values for eutrophic water bodies (Jones & Lee, 1982). Bentonite clay with a mean particle diameter of 9.45 mm, within the range of .90% of the inorganic suspended solids in the South American water bodies colonized by L. fortunei (Carignan, 1999; Sarubbi, Pittau & Menendez, 2004), was used at different concentrations: 0 g l (controls), 0.1, 0.5, 1, 2, 4, 6, and 8 g l. All experiments were performed at 27 8C (typical of the lower Parana River and Rio de la Plata estuary during the summer) in a controlled temperature chamber. For each sediment concentration, three replicates without (controls) and three with 60 individuals of L. fortunei were used. Upon termination of each experiment (120 min) all individuals were measured to the nearest 0.01 mm with digital calipers, and their tissues extracted and dried at 60 8C to constant weight (DTW). Immediately before start and after termination, each experimental container was sampled (40–150 ml) to estimate chlorophyll a concentrations. Samples were filtered through fibreglass filters (Whatman GF/F) and pigment extraction was performed with hot (60–70 8C) ethanol in darkness two or three times in order to avoid underestimations due to chlorophyll adsorption upon sediment particles (Koyama, Shimomura & Yanagi, 1968). The extracts were clarified by centrifugation, their volume adjusted and the absorbance at 665 and 750 nm measured with a spectrophotometer before and after acidification with HCl (1 N). Pigment concentrations were calculated according to Marker et al. (1980).