Rio Doce Basin Research Articles

Two centuries of ornithological exploration of the Rio Doce Basin, southeastern Brazil. Part II—A catalogue of its birds and a gazetteer

The Rio Doce Hydrographic Basin (RDB) lies almost completely in the Brazilian Atlantic Forest, a highly threatened tropical rainforest. The RDB has suffered dramatic anthropogenic impacts during the last two centuries and is currently one of the most degraded regions in southeastern Brazil. In this paper, we gathered 140,742 bird records collected since the early 19th by more than two thousand naturalists, professional scientists, and citizen scientists. This vast database was compiled from several sources, including published literature, unpublished technical reports, natural history museums, and citizen science platforms. After checking and standardizing the database, we found high species richness in the RDB, with 689 species recorded to date, from which 675 (98%) were documented by specimens or digital vouchers. This database is presented as a detailed catalogue, including maps containing all localities in which each species has been recorded. We present text accounts for 40 noteworthy species recorded in the RDB, and a complete gazetteer for the 636 localities sampled. Preliminary analyses reveal that the RDB avifauna suffered a dramatic change in its species composition during the last two centuries, mostly due to human activity. Highly sensitive species associated to pristine forests vanished, while species associated to dry and open habitat expanded their ranges in the RDB. Finally, in addition to thoroughly characterization of the RDB avifauna, this paper provides the basis for a series of studies about the avifauna of one of the hottest hotspots of biodiversity in the entire Neotropical region.

Rare Earth Element Accumulation in Fiddler Crabs (Minuca rapax) from the Rio Doce Tropical Estuary Strongly Affected by Mine Tailings Following the Fundão Disaster.

A mining tailing dam rupture in Brazil in November 2015 released millions of tons of mining waste into the Rio Doce ecosystem, leading to long-term aquatic ecosystem impacts. Although multiple lines of evidence indicate tailings associations with potentially toxic elements in estuarine sediments and biological impact and bioaccumulation pathways in fishes, the extent of contamination in base benthic species is still largely unknown. Moreover, Rare Earth Elements (REE) have not received any attention in this regard. This study assessed REE in fiddler crabs (Minuca rapax) sampled from the Rio Doce estuary in 2017, nearly 2years after the disaster. The ΣREE in crab hepatopancreas and muscle were high (327.83mgkg-1 w.w. and 33.84mgkg-1 w.w., respectively, compared to other assessments in crabs, indicating a preference for REE bioaccumulation in the hepatopancreas compared to muscle. Neodimium, La, and Ce were detected at the highest concentrations. The REE from the Rio Doce Basin were, thus, transported and deposited in the estuary with the mine tailings slurry, leading to bioaccumulation in crabs. This may lead to trophic effects and other ecological impacts not readily measured by typical impact assessment studies, revealing an invisible and not typically acknowledged damage to the Rio Doce estuary.

Mining tailings alter insects: revealing fluctuating asymmetry in the caddisfly Smicridea coronata.

The Samarco/Vale/BHP mine tailing dam breach that took place in Minas Gerais, southeastern Brazil, in 2015, deposited high concentrations of metals and metalloids in the Rio Doce basin, severely impacting freshwater and riverine forest ecosystems. To assess developmental instability of caddisflies in response to the environmental impacts of the dam breach, we investigated the fluctuating asymmetry (FA) in the species Smicridea (Rhyacophylax) coronata (Trichoptera: Hydropsychidae). FA was assessed at individual and populational scales using geometric morphometric methods in the cephalic capsule and mandibles of larvae and also on the forewings of adults, both collected under the impacted condition, and under the least disturbed condition. The levels of FA increased in response to stressors on the forewings at the populational scale, and on the mandibles, at individual scale. These morphological variations in the larval and adult stages may lead to detrimental effects and result in high mortality rates as well as lower adult fitness. Trichoptera forewings are revealed as suitable traits for assessing FA, holding potential for applications in biomonitoring programs. Directional asymmetry levels were higher than FA levels for all traits, and this correlation could be explained by a transition from fluctuating to directional asymmetry in the presence of heightened disturbance. Our results validate the relationship between the impacts from the dam breach and increased developmental instability in this species with likely cascade effects on the insect community.

Coalitions and repertories in the strategic action field of the people affected by the Rio Doce disaster

The collapse of the Fundão dam of the Samarco, Vale, and BPH Billiton mining companies in 2015 resulted in the spillage of unprecedented tailings in the Rio Doce Basin, Brazil. It was a disaster of multiple dimensions, generating conflicts between the affected community, mining companies, the government, and the justice system in the search for solutions to recover and repair the damage. Meanwhile, a governance system was created to conduct disaster responses and conflict resolution between those actors. In this article, we investigate how skilled actors in the affected field act to influence disaster governance by producing consequences for policy decisions. The analysis highlights the role of coalitions and action repertories in cooperative and conflicting relationships in the affected people's field. Through mixed-method research, four years of the socio-environmental disaster (2015–2019) were examined through interviews with activists, documentary research, and analysis of protest events. The main argument is that the mobilization of non-state actors in the affected field has influenced disaster governance and the content of compensation policies. Mobilization combined social skills and action repertoires and formed political coalitions to influence decision-making processes. The article contributes to expanding the understanding of the dynamics of political disputes among non-state actors, proposing to broaden the understanding of the repertoires of non-state actors in coalitions to generate consequences for political decisions.

Flora and structure of the naturally regenerating riparian vegetation of the Rio Doce River: basis for environmental restoration actions

Context The failure of the Fundão dam devastated a large area of the Atlantic Forest, causing damage to and loss of riparian forests. Considering all the ecological roles of a terrestrial and freshwater community, it is necessary to understand the functioning of riparian forests and their regenerative potential, which will be decisive in selecting actions to restore these ecosystems, especially Atlantic Forest remnants. Aims We evaluated the flora and structure of the regenerating stratum in three riparian vegetation remnants along the Rio Doce basin to support the propagation and restoration of the affected environments. Methods Plots of 5 m × 5 m were made in each area, totalling 77 sampling units. In these plots, all woody individuals with a diameter at soil height (DSH) of at least ≥1 cm and diameter at breast height (1.3 m from the soil) of at least <5 cm were marked, measured (in height and DSH), sampled and identified. Key results A total of 275 species distributed in 47 families were sampled, with Fabaceae the most diverse family and Siparuna guianensis Aubl. the most abundant species. Variation in β diversity was significant, and composition analysis showed that plots of each area tended to cluster. Principal component analysis and linear models showed that the edaphic parameters were not related to the richness and abundance of species in the sampled areas. Conclusions The areas sampled here serve as a reference for the restoration of impacted areas. Implications This study represents an important step towards knowing the species in reference areas for an active and efficient restoration in impacted areas.

Functional traits patterns along an altitudinal gradient in a large tropical forest region

Understanding the link between functional traits and environmental gradients can provide important information to face global change. Here, we assessed how environmental variables act on functional trait-based ecological strategies of the acquisitive-conservative continuum and dispersal syndromes in forests of the Rio Doce Basin in Brazil's Atlantic Forest. Through literature and herbarium measurements, we gathered data on ten functional traits related to light interception, leaf economics spectrum, and reproductive ability from 1912 woody species across 79 localities. Relationships between community-weighted means of functional traits and an altitudinal gradient encompassing thermal and water availability variables were quantified using generalized linear models and principal component analysis. We found that in higher altitudes are predominant vegetative conservative functional strategies (smaller leaves and petioles) and reproductive acquisitive functional strategies (smaller fruits and seeds and abiotic dispersed species). The thermal variables mainly influenced vegetative functional traits, which showed a predominantly acquisitive strategy in warmer areas, where there are more favorable and stable conditions for rapid growth and resource uptake. The water variables had a pronounced impact on reproductive functional traits, particularly in terms of dispersal patterns. Water availability tends to impact the costs of fleshy fruits and seeds with higher energy content. The patterns found for the altitudinal gradient reflected a combination of thermal and water variables, which is congruent with the aggregative role of altitude, composed of multiple physical and climatic conditions. In conclusion, the abiotic factors are operating on a large landscape scale in the plant communities, exerting influence on functional traits along the altitudinal gradient in a tropical forest region.

A new species of Campsurus Eaton, 1868 (Ephemeroptera: Polymitarcyidae) from the Doce River Basin, Brazil.

The male imago of Campsurus mirim sp. nov., an integrant of the C. major species group, is described based on material from a lake at the Rio Doce basin, Southeastern Brazil. It can be distinguished from other species of the group by the following combination of characteristics: small to medium size (body 7.3 mm, forewings 6.1 mm); blackish pigments on dorsum of head widely and strongly marked in fresh material; abdominal color pattern with pale transverse dashes on terga IIIVII; posterior margin of sternum IX triangular at middle; pedestals flat with inner margin broadly rounded and with both posterolateral corners (inner and outer) approximately of the same length, both acute; penes relatively wide and large, ventrally curved on apical and with apex of main lobe slightly twisted.

Polycyclic aromatic hydrocarbons in estuarine sediments as a consequence of the mine tailings remobilization and transport in the Rio Doce basin.

The Fundão dam failure in 2015 severely impaired the economy, the lives of riverine communities, and the aquatic ecosystems of the Rio Doce basin in southeast Brazil. Several contaminants, including polycyclic aromatic hydrocarbons (PAHs), were transported downstream, deposited in the estuary, and released into the Atlantic Ocean. The high concentration of PAHs in estuarine sediments may pose ecological risks and deleterious effects to benthic organisms, so here we aimed at determining the source and fate of these compounds before and after the tailings' arrival. The mean concentration of the analyzed Σ16PAHs increased from 34.05 µg kg-1 in the prefailure period to 751.77 µg kg-1 one year after the arrival of the tailing. The classification of the sediment quality changed from low to moderate contamination. Our results suggest that there was PAHs remobilization by mine tailings along the Rio Doce basin. The target analytes exhibited mostly a pyrolytic profile from fossil fuel and biomass burning. In addition to other contaminants deposited in the estuary after the arrival of the tailings, this study revealed that the profile change of PAHs in the estuary region is a consequence of the mud's erosive power. Integr Environ Assess Manag 2024;20:169-178. © 2023 SETAC.

High Endemism in an Endangered Biodiversity Hotspot: Phylogeny, Taxonomy and Distribution Patterns of Catfishes of the Psammocambeva Alpha-Clade (Siluriformes: Trichomycteridae) from the Rio Doce Basin, Brazil

The Rio Doce basin is situated in a biodiversity hotspot, with some fish groups still superficially known. The intense process of habitat loss and water contamination justifies efforts to speed up the pace of describing fish species diversity. Herein, we focus on a clade of trichomycterine catfishes, subgenus Psammocambeva, genus Trichomycterus, performing a multigene phylogenetic analysis, which integrated to a comparative morphological analysis corroborates monophyly and relationships of four species complexes. Five new species are recognised and described. Species distribution patterns support the recognition of five areas of endemism for trichomycterines, most of which are well-known biodiversity centres: Serra do Espinhaço, Serra do Brigadeiro, Serra do Caparaó, Serra do Castelo, and upper-middle Rio Doce. Trichomycterine diversity in the Rio Doce basin, with 16 species, of which 15 belong to Psammocambeva, is lower than in the smaller neighbouring Rio Paraíba do Sul basin, with 21 species in five subgenera. Data suggest that species diversification in the former basin is relatively younger, following the initial diversification of Psammocambeva in the Miocene, whereas diversification in the latter basin has been estimated to have occurred during the Oligocene. This study reinforces the importance of naming new taxa and delimitating areas of endemism as primary tools for conservation strategies.

Two centuries of ornithological exploration of the Rio Doce basin, southeastern Brazil. Part I—A history of the landscape, its explorers, and their collections

The Rio Doce Hydrographic Basin (RDB) was once covered by magnificent tropical forest, which remained untouched by Europeans for three centuries after the arrival of the Portuguese colonists in the Brazilian coast in 1500. Nevertheless, a dramatic change in land use occurred throughout the entire RDB after the turn of the 19th century. Currently, the RDB is one of the most degraded regions in southeastern Brazil and, recently, it was the scenario of the worst environmental disaster in Brazilian history. In this series of papers, we aim to construct a baseline biodiversity assessment that documents the changes in bird communities within the RDB throughout the last two centuries. In this first part, we present the history of the RDB landscape, its explorers, and their collections based on an extensive literature review and museum data. Early biological surveys in the RDB only started at the beginning of the 19th century and were conducted mostly by German and French naturalists. During the first eight decades of ornithological exploration, foreign field naturalists conducted expeditions to the RDB and collected hundreds of bird specimens. Unfortunately, labelling and curatorial procedures were often poor and despite the prodigious efforts of those naturalists, results obtained were often meagre. The second phase of exploration occurred from the 1900s to the 1960s and was dominated by expeditions conducted by Brazilian natural history museums. During this phase, labelling and curatorial procedures improved considerably and the material collected significantly advanced our knowledge about the RDB avifauna The third phase occurred from the 1970s to the first decade of the 21st century, when collection of specimens decreased sharply and the research activity slowly shifted from museums to universities, with a focus on ecology and natural history. We are now in a fourth, more pluralistic phase, in which research continues to be done by universities, Brazilian natural history museums have resumed their collection activity, and birdwatching has emerged as a popular activity in Brazil, producing a tremendous amount of data in a short period of time.

Applying multivariate techniques to fingerprint water quality impact of the Fundão Dam breach within the Rio Doce basin.

The Fundão Dam breach on 5 November 2015 (the "Event") released tailings, water, soil and/or sediments, and other debris to downstream watercourses. This breach included both direct and indirect impacts from scouring of soils and sediments along and within the affected courses. Multivariate statistical techniques were used to determine the potential of fingerprinting the impact of the breach compared to pre-Event water quality conditions and unaffected watercourses. The selection of key parameters is an important first step for multivariate analyses. Analysis of too many parameters can mask important trends and relationships, while analysis of too few may miss significant water quality indicators. A two-phased selection process was used to identify key parameters that indicated impact from the Event: (a) unbiased, principal component analysis to extract chemically dominant profiles among all measured parameters and (b) comparison of metals' concentrations between unaffected soils and/or sediments and tailings samples. Radar charts of key parameters along with statistical comparisons to pre-Event and not-affected waterways were then aggregated over space and time to assess impact and potential recovery to pre-Event conditions. Nine parameters were identified that characterize tailings-related (direct) and background soil and/or sediment-related (indirect) impacts. Spatially and temporally aggregated radar charts and nonparametric Mann-Whitney U tests were used to assess the statistical significance of these impacts during each wet season since the breach. Indirect parameters, like aluminum and lead, returned to pre-Event levels in the first wet season after the Event. By the 2018/2019 wet season, most of the direct and indirect parameters had returned to pre-Event levels. Integr Environ Assess Manag 2024;20:133-147. © 2023 NewFields Companies, LLC. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Four New Caddisfly Species of Marilia Müller, 1880 (Trichoptera: Odontoceridae) from a Tailings Dam Disaster Area, Rio Doce basin, Brazil

Marilia is the most diverse genus of the caddisfly family Odontoceridae, being distributed throughout the Oriental, Australasian and Neotropical regions. Herein, we describe four new Neotropical species from the Atlantic Forest, Rio Doce basin, Brazil. This basin was partly affected by a flood of 50 million m3 of mud and mining debris in 2015. Due to this disaster, numerous monitoring activities have been carried out to assess the impact generated. Material from one of these attempts was used to describe the new species: Marilia aranan sp. nov., Marilia krenak sp. nov., M. maxakali sp. nov. and M. mukurin sp. nov. Additionally, we provide a new state record of M. guaira from Minas Gerais. Marilia aranan sp. nov. was collected in tributaries as well as in the impacted area 7 years after the disaster. Marilia guaira and M. krenak sp. nov. were collected only in the impacted area. The other species were found only in tributaries. Odontoceridae are considered highly sensitive to disturbance. The presence of Marilia species suggests that parts of the riverbed have recovered from the fine tailing sediments and also highlights the importance of tributaries in the recolonization process.

Marine and estuarine crustacean diversity and assemblage structure in eastern Brazil three years after the Fundão mining dam failure

The present study investigates the spatial and temporal patterns of species richness and assemblage structure of decapod and stomatopod crustaceans in the area impacted by the Fundão dam collapse (Rio Doce basin, Brazil) in November 2015. From October 2018 to September 2019, monthly bottom-trawl samples were collected in estuarine and marine waters of the Rio Doce (directly impacted area) and three other localities. Forty-one crustacean species were recorded, with the overall community structure dominated by six species. The seabob shrimp Xiphopenaeus kroyeri was the most common species, with the coastal marine area near to the Rio Doce mouth being an important fishery ground. Species composition changed significantly among localities, habitats, and seasons, with marine and estuarine assemblages shaped by freshwater discharge. Distribution patterns of species were significantly influenced by the environmental variables potentially altered by tailings, such as turbidity and pH. Species richness and abundance differed among localities; as expected, they were generally higher on the inner shelf than in estuaries and higher during the dry season than the rainy season. Due to the lack of information before the disaster, the low number of species found in the Rio Doce estuary cannot be solely attributed to the disaster but also its freshwater condition. This is the first broad study of the estuarine and coastal marine decapod and stomatopod crustaceans in the region, and we suggest the need for long-term monitoring considering that the effects of this disaster are not easy to detect and probably need multi-year study to be evidenced.

Has the Rio Doce "time bomb" been defused? Using a weight-of-evidence approach to determine sediment quality.

The Fundão mine tailings dam rupture of 2015, in the Rio Doce basin, Brazil, resulted in the deposition of tailings downstream of the dam. It has yet to be determined if metals associated with the tailings have contributed toxicity to organisms, burying a time bomb that could be ticking. Currently the data on toxicity to benthic and aquatic organisms have not been assessed sufficiently to allow an informed assessment using an approach based on weight-of-evidence. This study was conducted to ascertain if sediments at "hot spots" that received Fundão tailings reflected elevated concentrations of metals and if these concentrations were sufficient to result in toxicity to freshwater organisms. The lines-of-evidence considered included assessing metals concentrations in relation to sediment quality criteria, establishing biogeochemical characterizations, completing an evaluation of potential metal release upon resuspension to provide information on bioavailability, and identifying acute and chronic toxicity effects using sensitive native species for waters (water flea, Daphnia similis) and sediments (burrowing midge larvae, Chironomus sancticaroli). Only porewater concentrations of iron and manganese exceeded Brazilian surface water criteria, whereas most trace elements exhibited no enrichment or elevated environmental indexes. The concentrations of bioavailable metals were assessed to be low, and metal concentrations did not increase in the overlying water upon resuspension; rather, they decreased through time. Toxicity testing in resuspended waters and bulk sediments resulted in no acute or chronic toxicity to either benthic or aquatic species. The low metal bioavailability and absence of toxicity of the tailings-enriched sediments was attributed to the strong binding and rapid removal of potentially toxic metal ions caused by oxyhydroxides and particles in the presence of iron-rich particulates. The findings of these sediment hot-spot studies indicate the Fundão dam release of tailings more than six years ago is not causing the current release of toxic concentrations of metals into the freshwaters of the Rio Doce. Integr Environ Assess Manag 2024;20:148-158. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Structure and composition of the nematode community in a restoration area affected by iron tailings

In 2015, the Fundão Dam collapse released over 40 million m3 of iron mine tailings, causing several environmental damages. Certain affected areas were revegetated with a mix of fast-growing species that can allowed the return of some organisms of soil fauna. Nematodes are the most abundant multicellular organisms in soil and are commonly used as bioindicators. Therefore, this study aimed to use the nematode community as bioindicators of the restoration process of an area affected by iron tailings at the margins of the Gualaxo do Norte River. Soil samples were collected from affected and native forest areas to perform physical, chemical, biochemical, and biological analyses. Nematodes were identified and classified according to feeding habits and on a colonizer-persisters (cp) scale. A non-metrical multidimensional scaling and PERMANOVA were conducted to assess differences between communities. Shannon’s diversity index and the maturity index were significantly higher in the restoration area. There was a difference in the composition and the structure of nematode communities of the restoration and reference area, nematode genus occurrence and abundance were different between the areas resulting in differences in feeding habits and life strategies according to the cp scale. The cp-5 nematodes are more abundant in the restoration area and cp-1 in the forest reference area. Bacterivore nematodes were more abundant in the reference forest area. In addition, the soil attributes in the restoration area were altered following the tailings deposition. Such alterations include high pH, low organic matter content, and low microbial biomass, which consequently influenced the structure and the composition of the nematode community. This is likely the first report of soil nematode community diversity in the areas of the Rio Doce Basin impacted by the Fundão tailings, and nematodes proved to be good bioindicators to show the differences between the restoration and forest reference area.

Bioaccumulation of Heavy Metals in two Species of Fish in the Rio Doce Basin after the Rupture of the Ore Tailings Dam in Mariana city, Minas Gerais, Brazil

Heavy metals appear in the aquatic environment mainly due to anthropogenic activities, such as mining. The impacts of environmental pollution by metals can be identified and quantified in target organs of animals, which tend to accumulate such pollutants. In November 2015, the ore tailings dam in Mariana-MG ruptured, dumping toxic mud into the Doce River Basin, with great mortality of fish and other organisms, in addition to long-term effects due to water and soil contamination.

Relationship of woody species composition with edaphic characteristics in threatened riparian Atlantic Forest remnants in the upper Rio Doce basin, Brazil

Studies on the composition, richness and diversity of plant species in tropical communities are essential for understanding relevant ecological processes and for developing appropriate conservation policies. Considering that areas subject to direct impacts due to dam breach may in the long‐term present changes in species composition and in soil parameters, we evaluated the composition of the flora, described the current vegetation profile, and evaluated whether differences in species composition was influenced by soil variables of three areas along the Gualaxo River, in Minas Gerais State, Brazil. In addition, we identified important plant species through occurrence and phytosociological parameters for ecological restoration projects in the affected region, serving as reference areas. We sampled plant species with DBH ≥ 5 cm (diameter at breast height – measured 1.30 m above ground level) in 77 plots distributed in three riparian forest areas. We calculated phytosociological parameters and related them to edaphic factors. A total of 1579 individual plants belonging to 53 botanical families and 227 species were sampled in the three areas. The Fabaceae family was the most representative with 46 species. Species composition and diversity among the sampled areas was similar and was associated with edaphic factors. Furthermore, some species (e.g. Xylopia sericea, Cupania emarginata and Ocotea pulchalla) showed an important relation with soil variables. Some species of the genera (e.g. Byrsonima, Xylopia, Ocotea and Croton) and families (e.g. Fabaceae and Myrtaceae) found here, can be important species in the restauration process for the local and regional maintenance of floristic identity in the Rio Doce river.

Two new species of small minnow mayfly (Ephemeroptera: Baetidae) from a mine-tailing dam disaster area in Minas Gerais, Brazil

After the worst mine-tailing dam disaster which occurred in Minas Gerais state, Brazil, it was necessary to understand the extent of the biodiversity loss. Thus, based on legal obligations, a monitoring of the fauna and flora along the Rio Doce basin was developed. From this large study, surprisingly, two undescribed psammophilous mayfly species were collected. Given the environmental disaster, and the particular concern with species that inhabiting sandy bottom, the two new species may be already threatened. Considering the reported circumstances, our objective is to described the new species and carry out their extinction risk assessment following the IUCN protocol. Apobaetis irai sp. nov. can be distinguished by the size and shape of the setae in the distal middle area of the dorsal surface of the labrum, with 3 minutes, blunt spatulate setae and the shape of the labial palp; is likely to be threated, plausibly eligible, at least, as Vulnerable (VU) B2ab(iii)+D2. Rivudiva watu sp. nov., can be distinguished by the distal shape of glossae, absence of row of setae on ventral margin on the hind tibiae and hypopharynx without distomedial projection; given its distribution, it was not directly impacted by the disaster, however, there is not enough data to accurately estimate the extent of its occurrence (EOO) and area of occupancy (AOO), therefore, it may be eligible for Data Deficient (DD).

Influences of multiple anthropogenic disturbances coupled with a tailings dam rupture on spatiotemporal variation in fish assemblages of a tropical river

Abstract The Mariana disaster, resulting from the rupture of the Fundão tailings storage facility (TSF) in 2015, was a large‐scale environmental disaster that drastically affected the entire channel of the Rio Doce, southeastern Brazil. The disaster produced substantial channel siltation, increased turbidity, riparian damage and a massive fish kill. However, the Rio Doce basin has a long history of environmental degradation, including hydroelectric dams. The latter are major threats to the ichthyofauna because they affect flow regimes, trap sediments and large wood, select generalist species, impair fish migrations and favour non‐native invasive species. In this study, we analysed the effects of the rupture as well as impacts from the construction of a run‐of‐the‐river hydroelectric dam on native and non‐native fish abundances, and species richness and composition in the middle Rio Doce. To do this, we examined fish survey data collected before and after each disturbance upriver of the reservoir, in the reservoir area and downriver of the dam. The data were separated into three temporal intervals: free‐flowing river, post‐filling reservoir and post‐TSF disaster. To assess temporal changes in native and non‐native fish species richness, we used a rarefaction method and tested it with two‐way ANOVA, which also was used to compare fish abundances. To test temporal changes in fish assemblage composition we used a PERMANOVA test. We observed no significant differences in total native or non‐native species richness as a result of the dam or the disaster. However, we did observe increased non‐native individual abundances after the TSF rupture as well as native individual abundances, depending on the location studied. The assemblage composition also changed after dam construction and the TSF rupture, except for the upriver reach after dam construction. We conclude that both the dam and the TSF rupture affected fish assemblages, favouring increased non‐native abundances, and also changed fish assemblage composition. Our results suggest that a century of landscape and riverscape pressures had extirpated the sensitive fishes from the Rio Doce before the TSF rupture. We conclude that multiple long‐term chronic disturbances can be as harmful to aquatic biota as the acute effects of a major environmental disaster.

Diversity and systematics ofTrichomycterusValenciennes 1832 (Siluriformes: Trichomycteridae) in the Rio Doce Basin: iterating DNA, phylogeny and classical taxonomy

AbstractThe catfish genus Trichomycterus is a recognized taxonomic bottleneck in Neotropical ichthyology. The hitherto poorly-known diversity of Trichomycterus in the Rio Doce Basin, Brazil, is here investigated using an iterative approach based on morphology and cytochrome oxidase subunit I (COI) sequence data. Specimens from the entire Rio Doce Drainage and adjacent basins are analysed, including from type localities. Iteration of different sources of data, dense sampling and taxonomic representation, plus information on relevant type specimens allows a clear view of the diversity, relationships and nomenclature of Trichomycterus in the Rio Doce Basin. Results indicate the presence of at least 14 species in the basin, seven of which are new. A lectotype is designated for Trichomycterus immaculatus and the type locality is accordingly restricted to the Rio São Mateus, a satellite basin north of the Rio Doce. Geographic distributions are mapped for all recognized species. The wide distributions of some species (e.g. Trichomycterus alternatus, T. immaculatus) are explained against information on geomorphological processes and comparative information on their biology. A Bayesian phylogenetic analysis shows that a large portion of the assemblage of Trichomycterus in the Rio Doce forms a clade, a pattern relevant to understanding the evolution of the genus in eastern South America.