Wetlands Of South America Research Articles

Hantavirus host assemblages and human disease in the Atlantic Forest.

Several viruses from the genus Orthohantavirus are known to cause lethal disease in humans. Sigmodontinae rodents are the main hosts responsible for hantavirus transmission in the tropical forests, savannas, and wetlands of South America. These rodents can shed different hantaviruses, such as the lethal and emerging Araraquara orthohantavirus. Factors that drive variation in host populations may influence hantavirus transmission dynamics within and between populations. Landscape structure, and particularly areas with a predominance of agricultural land and forest remnants, is expected to influence the proportion of hantavirus rodent hosts in the Atlantic Forest rodent community. Here, we tested this using 283 Atlantic Forest rodent capture records and geographically weighted models that allow us to test if predictors vary spatially. We also assessed the correspondence between proportions of hantavirus hosts in rodent communities and a human vulnerability to hantavirus infection index across the entire Atlantic Forest biome. We found that hantavirus host proportions were more positively influenced by landscape diversity than by a particular habitat or agricultural matrix type. Local small mammal diversity also positively influenced known pathogenic hantavirus host proportions, indicating that a plasticity to habitat quality may be more important for these hosts than competition with native forest dwelling species. We found a consistent positive effect of sugarcane and tree plantation on the proportion of rodent hosts, whereas defaunation intensity did not correlate with the proportion of hosts of potentially pathogenic hantavirus genotypes in the community, indicating that non-defaunated areas can also be hotspots for hantavirus disease outbreaks. The spatial match between host hotspots and human disease vulnerability was 17%, while coldspots matched 20%. Overall, we discovered strong spatial and land use change influences on hantavirus hosts at the landscape level across the Atlantic Forest. Our findings suggest disease surveillance must be reinforced in the southern and southeastern regions of the biome where the highest predicted hantavirus host proportion and levels of vulnerability spatially match. Importantly, our analyses suggest there may be more complex rodent community dynamics and interactions with human disease than currently hypothesized.

Population genetics of the capybara, Hydrochoerus hydrochaeris, in the Chaco-pampean region

Hydrochoerus hydrochaeris is an herbivorous rodent that inhabits most wetlands of South America. It is a well-known species, but studies about their population genetics are scarce. The aim of this study was to analyze the genetic diversity, population genetic structure and historical population dynamics of the species in the Chaco-pampean region, using mitochondrial DNA control region sequences and a non-invasive sampling design. Our results showed the existence of four haplogroups in the study area. Haplogroup I is composed by individuals from most of the study area, while the remaining include individuals from some sites in Paraguay (haplogroups III and IV) or Argentina (haplogroup II). The genetic diversity was low in haplogroups I, III and IV. Our results suggest that the Paraná and Paraguay rivers would be acting as a migration corridor for the species. Historical population dynamics analyses and haplotype network showed past population expansions and secondary contact between haplogroups I–II and I–IV, which could be related to past climatic events such as the Iberá Wetlands formation. These results must be taken as working hypotheses for future studies about the population genetics of capybara and related species inhabiting the region.

Suitability of Totora (Schoenoplectus californicus (C.A. Mey.) Soják) for Its Use in Constructed Wetlands in Areas Polluted with Heavy Metals

Schoenoplectus californicus subsp. tatora (totora) is an endemic plant from wetlands in South America’s Altiplano region. In the endorheic Titicaca-Desaguadero-Poopó-Salar de Coipasa system (TDPS), totora can be found along rivers, lakes, and shallow ponds. Lake Uru-Uru is a minor lake placed upstream of Lake Poopó, and it gets water inflows from the Desaguadero River, the city of Oruro and several mining and metallurgic complexes. Polluted waters from these origins, together with natural high salinity and high presence of As and Pb, make Lake Uru-Uru an ideal location to search for plant species suitable to be used in constructed and restored wetlands under pollution stress, particularly in systems with high pH and salty waters. To test if totora could meet such requirements, healthy plants were collected at two sites in Lake Uru-Uru with different exposure to polluted inflows. Chemical composition of different organs (leaves, rhizomes and roots) were compared. Results indicated totora’s capacity to withstand high concentrations of a cocktail of multiple pollutants and heavy metals. Particularly, this research showed totora as a multi-hyperaccumulator (concentrations in shoots higher than 1000 mg kg−1) for As, Fe and Ni. These results, combined with totora’s intrinsic high rates of biomass production, slow decomposition rates and its value as raw material for local craftwork and industrial uses, support the recommendation to use totora in constructed or restored wetlands, particularly in sites polluted with heavy metals, and in waters with high salinity.

Evaluating year-to-year anomalies in tropical wetland methane emissions using satellite CH4 observations

Natural wetlands are the largest source of methane emissions, contributing 20–40% of global emissions and dominating the inter-annual variability. Large uncertainties remain on their variability and response to climate change.This study uses atmospheric methane observations from the GOSAT satellite to evaluate methane wetland emission estimates. We assess how well simulations reproduce the observed methane inter-annual variability by evaluating the detrended seasonal cycle. The latitudinal means agree well but maximum differences in the tropics of 28.1–34.8 ppb suggest that all simulations fail to capture the extent of the tropical wetland seasonal cycle.We focus further analysis on the major natural wetlands in South America: the seasonally flooded savannah of the Pantanal (Brazil) and Llanos de Moxos (Bolivia) regions; and the riverine wetlands formed by the Paraná River (Argentina). We see large discrepancies between simulation and observation over the Pantanal and Llanos de Moxos region in 2010, 2011 and 2014 and over the Paraná River region in 2010 and 2014. We find highly consistent behaviour between the time and location of these methane anomalies and the change in wetland extent, driven by precipitation related to El Niño Southern Oscillation activity.We conclude that the inability of land surface models to increase wetland extent through overbank inundation is the primary cause of these observed discrepancies and can lead to under-estimation of methane fluxes by as much as 50% (5.3–11.8 Tg yr−1) of the observed emissions for the combined Pantanal and Paraná regions. As the hydrology of these regions is heavily linked to ENSO variability, being able to reproduce changes in wetland behaviour is important for successfully predicting their methane emissions.

Presence of influenza viruses in backyard poultry and swine in El Yali wetland, Chile

In South America little is known regarding influenza virus circulating in backyard poultry and swine populations. Backyard productive systems (BPS) that breed swine and poultry are widely distributed throughout Chile with high density in the central zone, and several BPS are located within the “El Yali” (EY) ecosystem, which is one of the most important wetlands in South America. Here, 130 different wild bird species have been described, of them, at least 22 species migrate yearly from North America for nesting. For this reason, EY is considered as a high-risk zone for avian influenza virus. This study aims to identify if backyard poultry and swine bred in the EY ecosystem have been exposed to influenza A virus and if so, to identify influenza virus subtypes. A biosecurity and handling survey was applied and samples were collected from BPS in two seasons (spring 2013 and fall 2014) for influenza seroprevalence, and in one season (fall 2014) for virus presence. Seroprevalence at BPS level was 42% (95% CI:22–49) during spring 2013 and 60% (95% CI 43–72) in fall 2014. rRT-PCR for the influenza A matrix gene indicated a viral prevalence of 27% (95% CI:14–39) at BPS level in fall 2014. Eight farms (73% of rRT-PCR positive farms) were also positive to the Elisa test at the same time. One BPS was simultaneously positive (rRT-PCR) in multiple species (poultry, swine and geese) and a H1N2 virus was identified from swine, exemplifying the risk that these BPS may pose for generation of novel influenza viruses.

Carbon isotope ratios suggest no additional methane from boreal wetlands during the rapid Greenland Interstadial 21.2

AbstractSamples from two Greenland ice cores (NEEM and NGRIP) have been measured for methane carbon isotope ratios (δ13C‐CH4) to investigate the CH4 mixing ratio anomaly during Greenland Interstadial (GI) 21.2 (85,000 years before present). This extraordinarily rapid event occurred within 150 years, comprising a CH4 mixing ratio pulse of 150 ppb (∼25%). Our new measurements disclose a concomitant shift in δ13C‐CH4 of 1‰. Keeling plot analyses reveal the δ13C of the additional CH4 source constituting the CH4 anomaly as −56.8 ± 2.8‰, which we confirm by means of a previously published box model. We propose tropical wetlands as the most probable additional CH4 source during GI‐21.2 and present independent evidence that suggests that tropical wetlands in South America and Asia have played a key role. We find no evidence that boreal CH4 sources, such as permafrost degradation, contributed significantly to the atmospheric CH4 increase, despite the pronounced warming in the Northern Hemisphere during GI‐21.2.

Artificial container mosquitoes and first record of Aedes aegypti in the islands of the Paraná Lower Delta, Argentina

Mosquitoes in artificial containers include Aedes aegypti and the Culex pipiens complex, both recognized worldwide as vectors of diseases. The goal of this study was to characterize mosquito communities in water-filled artificial containers in the islands of one of the major temperate wetlands in South America, and to assess whether A. aegypti is present in the area. Five domestic areas located in the insular Tigre District (Buenos Aires Province, Argentina) were visited monthly between November 2011 and May 2012. A total of 1013 artificial containers (half of them with water) were inspected for mosquito immatures. 3359 specimens corresponding to seven species were collected in 88 containers. A. aegypti was recorded for the first time in this wetland, and in all land use categories examined from February to May. Among the remaining six species, only Culex dolosus and C. pipiens were highly abundant. 88% of the mosquito positive containers were buckets, dustbins and boats, whereas highly available bottles did not act as mosquito breeding habitats; the key breeding container was different for each land use. The Container Index showed differences among land uses, materials, water capacity and volume, and insolation levels. Generalized Linear Mixed Models suggested that the probability of finding mosquitoes was higher for containers located in dumps and recreational areas, made of resin/fiberglass, presenting intermediate water volumes, and not in use if partially or totally shaded but in use for sunlit containers. Recommendations for mosquito prevention and control in the islands are proposed.

Diversidad de las comunidades de escamados en la Reserva Natural del Iberá, Corrientes, Argentina

The Iberá Nature Reserve has one of the most important wetlands in South America. This system is currently facing various threats to its preservation as a result of human activities. In this work we compare the diversity and complementarity —beta diversity— of the squamates fauna in relation to plant communities representative of 2 localities: Paraje Galarza and Colonia Pellegrini on the eastern edge of the Nature Reserve of Iberá, Corrientes province, Argentina. Using the method of sampling by quadrants, we recorded 33 species of squamates between 2007 and 2008, representing 53% and 38% of known species for the reserve and Corrientes province, respectively. Species richness and species diversity were higher in Colonia Pellegrini (S=29 and 21.26 effective species) than paraje Galarza (S=22 and 15.76 effective species). The complementarity of species among sites was about 45%. The grasslands were notable for their high species richness, diversity and high number of unique species. The wetlands, marshes and forests, had the highest values of complementarity, reflecting the specificity of their species. Our results demonstrated the importance of the different native environments for conservation of squamates and provide useful information for the management and conservation of the Iberá Natural Reserve.

Database of Ephemeral Wetland Vegetation in Extra- and Oro-Tropical South America

The vegetation of seasonal wetlands in South America has always been studied on local to regional scales. A synoptic view is missing and the distribution of vegetation types is not known. We investigate the floristic patterns at spatial level on the subcontinent and the environmental factors behind these patterns. The study area included extra-tropical South America (austral-temperate and sub Antarctic climatic zones) and the orotropical biome of the Andean Highlands, because the amphibious habitats in both areas share some taxa. Tropical lowlands were excluded. To have a consistent nomenclature is a major problem, and the taxonomic treatment of a number of habitat specific taxa is insufficient. The dataset et has two shortcomings: 1) data sampling was heterogeneous concerning plot size and homogeneity of the plot, 2) data sampling concentrates in some areas, while others are unexplored. This is most obvious in the Mediterranean part of Chile. The classification resulted in a higher diversity of communities as expected. 11 clusters with precise species combinations, ecology and distribution emerged from the classification. Strong spatial pattern emerged at a continental scale, not only by vicinity effects of the matrix vegetation surrounding the small scale seasonal wetlands, but also in the habitat specific flora and vegetation. The main differentiating environmental factors on large scales are macroclimatic conditions and the trophic level of the substrate. The azonal character of seasonal wetlands becomes obvious on the supra-specific taxonomic rank by genera, which speciated within this environment and evolved geographically vicarious species with similar niches (e.g. Isoetes, Limosella, Ranunculus, Hypsela, Oritrophium, Littorella, Lilaeopsis, Muhlenbeckia and Crassula). This report describes the available content in the Database of Ephemeral Wetland Vegetation in Extraand Oro-Tropical South America (GIVD ID SA-00-001).

Structure of aquatic vegetation of a large lake, western border of the Brazilian Pantanal

Studies on Neotropical aquatic macrophytes have increased in recent decades, however species richness in wetlands of South America is far from being fully known. In addition, studies having an ecological approach are scarce in the Pantanal. Rapid assessments are essential for gaining knowledge of the biodiversity in the region. This study was performed in five sites of the Baía do Castelo, the western border of the Brazilian Pantanal, which included wild-rice patches, floating mats and floating meadows. At each site, plots of 0.5 × 0.5 m were set (n = 137), species of aquatic macrophytes were identified, their coverage was measured and the plot depth was estimated. We recorded 57 species in 26 families, of which Poaceae was the richest. The most frequent and abundant species was Commelina schomburgkiana; the second most frequent was Oryza latifolia,followed by Leersia hexandra, Enydra radicans and Pityrogramma calomelanos. The latter species was second in cover, followed by Pontederia rotundifolia, Eichhornia azurea, E. crassipes and Enydra radicans. These five species and C. schomburgkiana (the most abundant) together represent more than half of the coverage on the lake. Pontederia rotundifolia, Ludwigia helminthorrhiza, Pistia stratiotes, E. azurea, E. crassipes, Enydra radicans and Panicum elephantipes were strongly associated with deeper areas, while Oryza latifolia, Leersia hexandra and Salvinia auriculata were prevalent in shallow areas. Pityrogramma calomelanos, Ludwigia nervosa, Ipomoea alba, Cayaponia podantha, Polygonum acuminatum, Rhynchanthera novemnervia and Ludwigia leptocarpa were highly correlated with floating meadows. The structure of the habitat, natural dynamics and zonation of aquatic vegetation in the Baía do Castelo seems to be influenced by a variation in water levels, which promotes spatial segregation, most likely due to competition and/habitat preference.

Oviposition strategies of temporary pool mosquitoes in relation to weather, tidal regime and land use in a temperate wetland

Wetlands have traditionally been associated with harbouring mosquitoes, a well-known nuisance and vectors of diseases. Within mosquito life cycle, oviposition is a determinant event by shaping their individual fitness and vectorial capacity. The study was conducted in one of the main temperate wetlands in South America. We used Generalized Linear Models to study the relation between temperature, precipitation, tidal regime, land use, microenvironment, and the occurrence of floodwater (Ochlerotatus and Psorophora spp.) and raft-laying (Culex and Uranotaenia spp.) mosquitoes using temporary pools as larval habitats. Pool occurrence was negatively associated with temperature, and positively related to precipitation and high tides. As regards the land use, it was lowest in domestic areas and plantations, intermediate in secondary forests, and highest in marshes. Each oviposition strategy was best modelled as a function of different environmental factors. The occurrence of floodwater mosquitoes was positively associated with high cumulative precipitation and low tide records. Raft-laying mosquitoes were related to low temperature records, while the effect of flooding varied with the land use. In view of these results, physical (water inputs and movement), chemical, and biological (egg and larval flushing, and predatory interactions) considerations are given to provide insight in the oviposition patterns of mosquitoes occurring in this complex wetland. We finally propose the generation of a tidal flow as a control measure against floodwater mosquitoes, which are the most anthropophilic in the study area.

Pasture clearing from invasive woody plants in the Pantanal: a tool for sustainable management or environmental destruction?

With a total area of 160,000 km2, the Pantanal is one of the largest wetlands in South America and certainly the most famous. It is essential for the maintenance of biodiversity and is highly ranked in national and international protection plans. The ecology of the Pantanal is influenced by the annual inundation, frequent fires during the dry period, and multiple human activities. To maintain traditional low density cattle ranching, which is the economic basis for the Pantanal’s human population, the spread of woody vegetation into former pasture areas requires pasture clearing. Legal restrictions, however, have led to the confusion of pasture clearing with the illegal deforestation that has accompanied Brazil’s rapid economic development, thus creating serious conflicts between the Pantanal’s ranchers and the governmental environmental agency. This dichotomy of interests, i.e., the need to maintain habitat and species diversity while guaranteeing the livelihoods of the ranchers but warding off deforestation, can only be resolved through modern management plans that reconcile the requirements of environmental protection with the economic needs of the ranchers, who are the owners of most of the Pantanal. The key to any such plan’s successful implementation is to consider the Pantanal not as a pristine wetland, but as a valuable cultural landscape. Over the last two and a half centuries, the vegetation in large parts of the Pantanal has been altered due to the presence of cattle ranches. This has maintained its habitat diversity and multiple services to humans and to the environment, including the enhancement of species diversity. This management practice corresponds to modern approaches in other parts of the world, where low density animal grazing, sometimes in combination with mechanical removal of woody vegetation are considered powerful management tools for the maintenance of valuable cultural landscapes.

Habitat and Grazing Influence on Terrestrial Ants in Subtropical Grasslands and Savannas of Argentina

AbstractThe maintenance of species diversity in modified and natural habitats is a central focus of conservation biology. The Iberá Nature Reserve (INR) protects highly diverse ecosystems in northeastern Argentina, including one of the largest freshwater wetlands in South America. Livestock grazing is one of the major disturbances to these ecosystems; however, its effect on ant diversity is poorly known. The objective of this work was to study the effect of savanna versus grassland and grazing on the structure and composition of subtropical terrestrial ants focusing on the particular response of the native red imported fire ant, Solenopsis invicta Buren. Unbaited pitfall traps were used to capture worker ants in 25 grazed and 20 nongrazed sites. Fifty ant species were collected. The savanna showed more species, individuals, biomass, and functional groups of ants than the grassland. S. invicta was the most frequently captured (61.4%) and numerically dominant species; however Camponotus punctulatus punctulatus Mayr showed the highest biomass. Grazing simplified vegetation structure in both habitats, but its impact on vegetation seemed only to promote a higher total biomass especially in the grassland, and/or functional groups, favoring occurrence of hot-climate specialists in the savanna. This study revealed that habitat type strongly affected the organization of the terrestrial ant assemblages at the INR. However, as in other studies, we did not find clear evidence that habitat modification by grazing significantly affected terrestrial ant assemblages. The weak grazing influence could be the consequence of the short enclosure time as to recover the original ant communities, the differential response of ant species to habitat type, and/or the resilience of ants.

Top-down and bottom-up regulation of planktonic communities in a warm temperate wetland

This field experimental study simultaneously analysed the effects of predation (top-down) and nutrients (bottom-up) on planktonic communities (phytoplankton, zooplankton, heterotrophic nanoflagellates and ciliates) in a warm temperate wetland in South America. The top-down and bottom-up controls were investigated by assessing the impact of omnivorous-planktivorous fish (Jenynsia sp.) and the effects of nutrient input from natural lake sediments, respectively Three treatments and a control were run in triplicate in mesocosms and samples were taken at Days 0, 3, 7 and 15. The control contained all the planktonic components while treatments included all planktonic components plus the addition of either planktivorous fish (F), natural wetland sediments in dialysis bags (S) or both of them (SF). A bottom-up effect due to nutrient release from sediment (mainly total phosphorus) was noticed in treatments S and SF. Phytoplankton abundance increased in all treatments compared with the control. Thus, phytoplankton appeared to be bottom-up controlled while fish exerted a strong predation pressure on zooplankton (top-down), because treatments F and SF showed a marked decrease in mesozooplankton abundance. The results obtained in this study agree with the hypothesis that phytoplankton regulation by zooplankton might be weaker in warm temperate systems than in temperate ones.

Seasonal and interannual analysis of wetlands in South America using NOAA-AVHRR NDVI time series: the case of the Parana Delta Region

The use of NOAA-AVHRR NDVI time series from July 1981 to December 2000 was evaluated for the assessment of the functioning of a wetland macrosystem, the Parana River Delta. The spatial resolution of the dataset was 8 by 8 km. Spatial and temporal variations in NDVI pattern were analyzed and evidences for El Nino/South Oscillation events identified. We studied five wetland units (WUs) classified on the basis of landscape pattern and dominant hydrologic regime. Spearman rank correlations were performed among the NDVI time series of the different WUs. NDVI time series were correlated with water level in the Parana River and with records of local rainfall. In order to obtain a synthetic model of NDVI patterns, the autocorrelation functions (ACF) were estimated for each of the WUs. Results indicated that monthly mean NDVI values for all WUs showed a similar annual seasonal pattern, suggesting a control from the plant annual cycle on the NDVI signal. Besides, two general NDVI patterns were identified. The first pattern is represented by WUs under fluvial hydrologic regime. This is subjected to a significative interannual variability associated mainly to ENSO events. The second pattern corresponds to WUs with a very regular NDVI patterns. It includes wetlands which water input corresponds to tides or to rainfall. The ENSO had no significant influence on this pattern. This study suggests that NOAA-AVHRR NDVI long time series might provide valuable information about functioning of the large scale fluvial wetlands like those associated with South America basins.

Species of <I>Megamelus</I> (Hemiptera: Delphacidae) Associated with Pontederiaceae in South America

The genus Megamelus Fieber (Hemiptera: Delphacidae), frequently associated with aquatic plants, includes four species in South America. One of these species, Megamelus scutellaris Berg, was the only species previously recorded in Argentina. In recent explorations in wetlands of South America (northeastern Argentina, eastern Peru, and southeastern Brazil), five species on Pontederiaceae were studied: Megamelus electrae Muir, Megamelus iphigeniae Muir, M. scutellaris, Megamelus timehri Muir, and Megamelus bellicus Remes Lenicov & Sosa sp. nov. Male holotypes of M. electrae, M. iphigeniae, and M. timehri were redescribed; females of both winged forms and brachypterous males of M. electrae and M. iphigeniae, and the female allotype of M. timehri, were described for the first time. M. bellicus is new for science, and it is described based on the following pattern combination: front coloration, anal segment with asymmetrical spine-like processes, shape of pygofer and aedeagus processes in the male, length of the ovipositor, and shape of the valvifer VIII. A key to distinguish the five South American species, based on male and female genitalia and the external morphology, is presented. This work is an update of knowledge on this genus, incorporating new specific diagnostic characters such as the length of ovipositor, shape and position of valvifer VIII, shape and denticulation of the first and second valvulae, and coloration pattern. Further information on host plants, geographical distribution, and biological data are reported.

Mapping and monitoring lakes in the Brazilian Pantanal wetland using synthetic aperture radar imagery

1. The Pantanal wetland in South America is being threatened by human development, such as the construction of hydropower dams in the upper Paraguay River and the Hydrovia. The consequences of these developments are difficult to predict, but will potentially cause irreversible loss of habitat and biodiversity. 2. Radar satellite imagery can be used to establish baseline information that is crucial for monitoring changes in this region. In the case of the Pantanal, the pixel spacing of the imagery is a major concern if the goal is to count, map, and monitor lakes. To address this, Radarsat and JERS-1 data were acquired and used to produce a series of coarser-resolution images in order to understand the capabilities of the various resolutions to map Pantanal lake ecosystems. The simulations included resolutions of the existing JERS-1 mosaics (100 m resolution) and the proposed ALOS/PALSAR mosaics (50 m resolution). 3. Using the 15 m data it was found that in the Nhecolândia region of the Pantanal, only about 7% of lakes have an area larger than 0.2 km2, 47% have an area larger than 0.05 km2, and 50% are smaller than 0.05 km2. Therefore, it is important to consider the substantial number of lakes smaller than 0.05 km2. 4. The size of the errors in determining lake area depends on lake size, lake shape, and the image pixel spacing — long and small lakes have greater errors, and 100 m resolution images show unacceptable errors. The error in estimating lake area associated with the pixel spacing of the Radarsat ScanSAR image is 12.5% and 25%, and for the proposed mosaics of ALOS/PALSAR it is 30% and 47% for lakes larger and smaller than 0.05 km2 respectively. Therefore, based on simulated results, the spatial resolution of the observing SAR was an important determining factor in the capacity to discriminate small lakes in the Pantanal. Copyright © 2007 John Wiley & Sons, Ltd.

Large wetlands of South America: a model for Quaternary humid environments

Large wetlands are important landscapes in South America, where today they cover one million square kilometers. Such environments probably were as important in the Quaternary of other continents. Tensional tectonic processes in the Andean foreland and other lowlands result in the sinking of blocks several thousand square kilometers in surface. Under humid climates, such depressions become occupied by shallow waters and a dense paludal vegetation. These features are a special case of wetlands, which owing to their areal extension, complexity, internal fluxes of sediments and salts, must be considered as macrosystems (Neiff et al., Large tropical South American wetlands: a review UNESCO Ecotones Workshop, Seattle, UNESCO, Paris, 1994, 15pp.) and are a major depositional environment in South America. Such areas are plains, characterized by more or less periodic flooding and complex ecosystems adapted to large water fluctuations. Such water bodies have frequent anaerobic conditions and accumulate organic matter in various degrees of decomposition. South America contains 14 wetlands with areas larger than 10000 km 2. Other somewhat smaller wetlands appear in abandoned fluvial belts inside megafans. Examples of this type can be found in the Pilcomayo river system in Argentina, where an old belt is at present a swamp 250 km long and 7–12 km wide. Large inland wetlands in South America can be grouped in two types: Pantanales, or sandy swamps; and Mud Wetlands. Both are clearly different in geomorphology, sediments, types of salts, and ecology. From the point of view of Quaternary Science, the degree of knowledge of the large wetlands is really poor. In general, it is restricted to the survey of the present conditions, which is itself important because similar environments have generally been reclaimed for agriculture since hundreds of years in other continents. An example of a large wetland of Late Pleistocene age (the Tapebicuá Fm, Argentina) is presented in this article. It is also clear that tropical swamps did exist throughout the Quaternary, and they very probably were “hot spots” for evolution of plants and animals and refuges for particular ecosystems.

Astyanax pynandi sp. n. (Characiformes, Characidae) from the Esteros del Iberá wetland, Argentina

Astyanax pynandi is described from the Esteros del Ibera, one of the major wetlands in South America. Astyanax pynandi bears hooks on all fin rays of males, such as in A. troya and A. ojiara. Astyanax pynandi is distinguished from the remaining species of the genus by the following combination of characters: one maxillary tooth with 5 or 7 cusps; teeth of inner premaxillary row expanded distally; low dentary, bearing 8 teeth decreasing in size anteroposteriorly; 34-37 perforated scales in lateral series; 6-7 upper transverse scales; iii-v, 21-26 anal-fin rays; orbital diameter (36.7-43.5% of HL); postorbital length (37.0-44.7% of HL); and peduncle length (32.3-37.7% of HL). One humeral spot vertically elongated, bounded by a light area, and a second lateral spot faint or well developed.

An association of mangrove mutation, scarlet ibis, and mercury contamination in Trinidad, West Indies

An unusually high incidence of mutations in a local population of red mangroves on the island of Trinidad was associated with locally elevated mercury levels in the underlying sediments. This restricted mercury contamination surrounded a large roost of scarlet ibises. Molted feathers of ibises using the roost had high concentrations of mercury, which were probably acquired by the birds during their annual migration to wetlands in South America contaminated with run-off from gold mining operations. Decades of molted feathers accumulating around the roost apparently has created the local contamination problem.