Negative impacts of mining on Neotropical freshwater fishes

An overview of vinasse pollution in aquatic ecosystems in Brazil

We review the negative impacts of vinasse, a byproduct of alcohol distillation, on Brazil's freshwater ecosystems. We found a total of 37 pollution events between the years 1935 and 2023, with this number almost certainly an underestimate due to underreporting and/or unassessed events. Pollution by vinasse occurred both through accidents (e.g., tank failure) and deliberately (i.e., opening of floodgates), although in many cases the causes remain undetermined. All pollution events caused fish kills, with some records reporting negative effects on other organisms as well (i.e., crustaceans and reptiles). Pollution by vinasse, and associated negative effects, was reported for 11 states, with a notable number of cases in São Paulo. Most cases of vinasse pollution and negative impacts on biodiversity were recorded in rivers, followed by streams and reservoirs. Some of the affected river systems harbour threatened freshwater fishes. Hydrological connectivity means that pollution could have propagated along watercourses. Given these consequences of vinasse pollution on biodiversity, ecosystem functioning and services, we recommend a number of remedial actions.

Impact of hydrocarbon extraction on heavy metal concentrations in lowland paca (Cuniculus paca) from the Peruvian Amazon

Oil has been extracted from the Western Amazon since the 1920s, leading to severe environmental contamination due to frequent occurrence oil spills and the dumping of produced water. Local inhabitants, along with environmental and human rights organizations, have reported the adverse effects of oil-related pollution on their livelihoods and the ecosystems they depend on. Here, we study accumulation of oil-related heavy metals in wildlife, and its subsequent incorporation into the trophic chain. We analysed the concentration of 14 heavy metals (Cd, Cr, Hg, As, Ni, V, Ba, Se, Be, Fe, Cu, Zn, Mn, Al) in liver samples from 78 lowland pacas (Cuniculus paca) hunted for subsistence in an oil-polluted area from the northern Peruvian Amazon where oil has been extracted since the 1970s (n = 38), and two control areas, the Yavari-Mirín River basin (n = 20), and the Pucacuro River basin (n = 20). Pacas in the oil-polluted area have significantly higher concentrations of Cd (P < 0.01) and Ba (P < 0.0001) compared to those in control areas, suggesting bioaccumulation of oil-related pollution. Conversely, Se levels were significantly lower in the oil-polluted area (P < 0.0001), likely due to the sequestration of Se by other heavy metals, particularly Cd. Additionally, minor variations in other heavy metals, e.g., Fe and Zn, were observed in pacas from the oil-polluted area, whereas control areas showed higher concentrations of Ni and Cu. Mn and Al levels did not significantly differ between the study areas. These results underscore the impact of oil extraction on the absorption and assimilation of heavy metals in wildlife, point at oil activities as the source of the high and unsafe blood Cd levels reported for the indigenous population of the studied oil extraction area and raise concerns about the long-term health risks from oil extraction posed to local Indigenous People who rely on subsistence hunting.

Irrigation dams threaten Brazilian biodiversity

Brazil is among the main contributors to global biodiversity, which, in turn, provides extensive ecosystem services. Agriculture is an activity that benefits greatly from these ecosystem services, but at the same time is degrading aquatic and terrestrial ecosystems and eroding Brazilian biodiversity. This conflict is growing, as emerging unsustainable legislative proposals that will benefit the agricultural sector are likely to accelerate the decline of biodiversity. One such initiative (Bill 1282/2019) would change Brazil's "Forest Code" (Law 12,651/2012) to facilitate construction of irrigation dams in Permanent Preservation Areas, a category that includes strips (with or without vegetation) along the edges of watercourses. Two other similar bills are advancing through committees in the Chamber of Deputies. Here we provide details of these three bills and discuss their consequences for Brazil's biodiversity if they are approved. Expected negative impacts with changes in the legislation include: increased deforestation; siltation; habitat fragmentation; introduction of non-native species; reduction in the availability of aquatic habitats; and changes in biogeochemical process. These proposals jeopardize biodiversity and may compromise the negotiations for an agreement between Mercosur and the European Union.

Abiotic and biotic factors influencing heavy metals pollution in fisheries of the Western Amazon

The escalating industrial and artisanal extraction of natural resources in the Amazon Basin has centered it into the spotlight of global environmental concern. This study deals with the environmental problems of heavy metals pollution and biomagnification, which stem from mining, agricultural, petrochemical, and industrial discharges. We conducted an extensive investigation, analyzing 360 fish specimens representing 58 species, to assess the concentrations of 11 metals (Al, As, Cd, Cr, Cu, He, Mn, Ni, Pb, Zn, and Hg) along the Ecuadorian sections of the Napo and Pastaza watersheds. Stable isotope analyses (δ15N and δ13C) were employed to determine their trophic positions and potential biomagnification risks. Sampling was carried out during two distinct hydrological seasons to capture seasonal variations in metal concentrations. Furthermore, we estimated species-specific daily heavy metal intake levels. The results of our study revealed that 15 fish species and 53 individual specimens exhibited heavy metal concentrations surpassing recommended standards, with elevated levels of Al, As, and Hg posing significant risks to human consumers with daily intakes of 0.46 kg/day. Notably, our investigation unveiled concerning trends, including increased metal concentrations, Hg biomagnification within fish populations from the Pastaza watershed, and an association between smaller fish size and higher metal content. This study provides a crucial baseline for monitoring future environmental changes and understanding the persistent impacts of heavy metal pollution in the Ecuadorian Amazon region and the broader Western Amazon. It underscores the urgent need for sustainable environmental management practices to mitigate the escalating threat to these vital ecosystems.

Continental fishes of Nicaragua: diversity, distribution and conservation status; with an annotated and illustrated checklist of species and an identification guide to families

Based on a combination of intensive literature review, electronic database searches, re-identification of museum specimens, and fieldwork, we provide an updated checklist of the continental fishes of Nicaragua. This checklist, systematically arranged at the ordinal and familial level, includes nomenclatural revisions, distributional information, conservation status, and when appropriate, cross-references to previous lists and revisionary works on the fish fauna of the country and region (Central America); illustrations and descriptions to the family level and color photographs of some representative species are also included. According to our results, the native Nicaraguan continental fish fauna is composed of 244 species, divided into 111 genera, 45 families, 24 orders, and two classes; increasing by 60 (i.e., 32.6%) the number of species originally reported by Villa (1982; i.e., the most comprehensive work published to date). The majority of the Nicaraguan native continental fish species, according to their supposed tolerance to salinity, are peripheral (68.9%), followed by secondary freshwater fishes (23.8%), and primary freshwater fishes (only 7.4%). Fish diversity in the 19 major river basins ranged between 21 and 90 species (mean = 58 species, median = 60); the Escondido (Es; 87 species), in the Atlantic, and the Pacfico de Nicaragua (PN; 90), in the Pacific, presented the highest species richness. Most species (188) are restricted to elevations between 0 and 100 meters above sea level (masl); only a few species (18), in contrast, were found at elevations greater than 500 masl (up to 780 masl). Fourteen species in this revision are listed as endemic to Nicaragua. Regarding their conservation status, 22 species (9.0%) are categorized, according to the International Union for Conservation of Nature (IUCN), as Data Deficient, 186 (76.2%) as Least Concern, and seven (2.9%) as Near Threatened; while 24 species (9.8%) are listed as Threatened, thirteen (5.3%) as Vulnerable, two (0.8%) as Endangered, and nine (3.7%) as Critically Endangered. Five species (2.0%) have not yet been evaluated. Six exotic species are also reported. Our results provide a framework for future taxonomic and biogeographic works on fishes from this country and region (Central America), particularly by providing up-to-date knowledge on nomenclature and distributions. In addition, the data provided in this revision will help to monitor fish distributional changes in the future due to human introductions and global change and will aid in conservation decisions concerning Nicaraguan continental fishes.

Illegal mining impacts on freshwater Potamonautid crab in a subtropical Austral highland biosphere reserve

The contamination of surface water by heavy metals, especially mercury, has become a global issue. This problem is particularly exacerbated in rivers and reservoirs situated in developing nations. Therefore, the objective of this study was to evaluate the potential contamination effects of illegal gold mining activities on freshwater Potamonautid crabs and to quantify the mercury levels in 49 river sites under three land use classes: communal areas, national parks and timber plantations. We used a combination of field sampling, multivariate analysis and geospatial tools to quantify mercury concentrations in relation to crab abundances. Illegal mining was prevalent throughout the three land use classes, with mercury (Hg) being detected in 35 sites (71.5 %). The mean range of Hg concentrations detected across the three-land uses was: communal areas 0-0.1 mg kg-1, national parks 0-0.3 mg kg-1 and timber plantations 0-0.06 mg kg-1. Mean Hg geo-accumulation index values showed strong to extreme contamination in the national park, with strong contamination observed for communal areas and timber plantations; furthermore, the enrichment factor for Hg concentrations in the communal and national park areas showed extremely high enrichment. Two crab species (i.e., Potamonautes mutareensis, Potamonautes unispinus) were found in the Chimanimani area, with P. mutareensis being the dominant taxon in the region across all the three land use areas. The national parks had higher total crab abundances than communal and timber plantation areas. We observed negative and significant K, Fe, Cu and B effects on total Potamonautid crab abundances, but surprisingly not for other metals such as Hg which might reflect their widespread pollution. Thus, illegal mining was observed to impact the river system, having a serious impact on the crab abundance and habitat quality. Overall, the findings of this study underscores the need to address the issue of illegal mining within the developing world as well as to establish concerted effort from all stakeholders (e.g., government, mining companies, local communities, and civil society groups) to help protect the less charismatic and understudied taxa. In addition, addressing illegal mining and protecting understudied taxa aligns with the SDGs (e.g. SDG 14/15-life below water/life on land) and contributes to global efforts to safeguard biodiversity and promote sustainable development.

A systematic review on metal contamination due to mining activities in the Amazon basin and associated environmental hazards

Metal contamination associated with mining activities has been considered one of the main environmental pollution problems in the Amazon region. Understanding the levels of metal contamination from mining activities requires a good understanding of background metal concentrations, which may vary notably according to the geology/lithology characteristics of the region, soil type, and predominant biogeochemical processes. This review assessed 50 papers and reports published between 1989 and 2020 describing environmental concentrations of different metals and metalloids (As, Hg, Mn, Fe, Cd, Cu, Cr, Pb, Ni, and Zn) in water and sediments of mining and non-mining areas in five geographic regions of the Amazon basin. Metal enrichment caused by mining activities was calculated and exposure concentrations were compared with sediment and water quality standards set for the protection of aquatic life. Significant enrichments of Cd, Cu, Cr, Fe, Hg, Mn, Ni and Zn were observed in mining areas in both sediment and water. Regarding background levels in the different geographic regions, the highest prevalence of metal enrichment (i.e., concentrations 10 to 100-fold higher than mean background values) in sediment samples was found for Fe (100% of samples), Ni (90%), and Mn (69%). For water, high prevalence of metal enrichment occurred for Zn, Mn, and Fe (100% of samples), and for Hg (86%). Hg, Fe, Pb, Cu, Cd, Ni and Zn exceeded water and/or sediment quality standards in a significant number of samples in the proximity of mining areas. This study indicates that mining activities significantly contribute to water and sediment contamination across the Amazon basin, posing hazards for freshwater ecosystems and potentially having human health implications.

Impacts of mining pollution on coastal ecosystems: is fish body condition a reliable indicator?

Identifying reliable biological indicators is fundamental to efficiently assess human impacts on biodiversity and to monitor the outcomes of management actions. This study investigates whether body condition is an appropriate indicator of putative effects from iron ore mining tailings on marine fishes, focusing on the world's largest mining disaster - known as the Mariana disaster, in Brazil. Eight species were used to test the hypothesis that individuals inhabiting an area severely impacted by tailings have reduced body condition in comparison to those in control areas near (<60 km) and distant (>120 km) from the impact site. Contrary to our prediction, no significant difference in condition was detected between the impacted area and both near and distant controls in seven of the eight species. The results indicate that body condition, as measured by the scaled mass index, has limited applicability as indicator of impact from mining pollution on the fishes analysed. Hypotheses that could explain our findings are proposed, including nutrient provisioning from continental drainage that could indirectly influence fish condition and compensate for the deleterious effects of mining pollution.

A global rise in alluvial mining increases sediment load in tropical rivers

Increasing gold and mineral mining activity in rivers across the global tropics has degraded ecosystems and threatened human health1,2. Such river mineral mining involves intensive excavation and sediment processing in river corridors, altering river form and releasing excess sediment downstream2. Increased suspended sediment loads can reduce water clarity and cause siltation to levels that may result in disease and mortality in fish3,4, poor water quality5 and damage to human infrastructure6. Although river mining has been investigated at local scales, no global synthesis of its physical footprint and impacts on hydrologic systems exists, leaving its full environmental consequences unknown. We assemble and analyse a 37-year satellite database showing pervasive, increasing river mineral mining worldwide. We identify 396 mining districts in 49 countries, concentrated in tropical waterways that are almost universally altered by mining-derived sediment. Of 173 mining-affected rivers, 80% have suspended sediment concentrations (SSCs) more than double pre-mining levels. In 30 countries in which mining affects large (>50 m wide) rivers, 23 ± 19% of large river length is altered by mining-derived sediment, a globe-spanning effect representing 35,000 river kilometres, 6% (±1% s.e.) of all large tropical river reaches. Our findings highlight the ubiquity and intensity of mining-associated degradation in tropical river systems.

A new genus and species of whiptail armored catfish (Siluriformes: Loricariinae) from southern Venezuela

A new genus and species of whiptail loricariid catfish belonging to the Pseudohemiodon group is described with 12 specimens captured from the upper Orinoco River and Casiquiare River, Amazonas State, Venezuela. The specimens show delicate and fragile appearance, and are small (largest specimen 74.3 mm SL). The new species has external morphological characters that support its inclusion in the Pseudohemiodon group; however, its mouth morphology is distinctive and unique with features not observed in any species of that group, nor in any other species included in tribe Loricariini or in subfamily Loricariinae. The distinctive buccal characters include: 1) barblets on upper lip border and the maxillary barbel included and interconnected by translucent membrane, leaving the tips free; 2) lower lip surface covered with elongated, cylindrical, unbranched, and fleshy barblets, which resemble filaments, some of them surpassing the border of lower lip. The comparative analyses carried out determined that the recently described species Rhadinoloricaria papillosa has the same two diagnostic buccal characters observed in the new species; therefore it is transferred to the new genus.

Checklist of the fish fauna of the Munim River Basin, Maranhão, north-eastern Brazil

Background

The Maranhão State harbours great fish diversity, but some areas are still undersampled or little known, such as the Munim River Basin in the northeast of the State. This lack of knowledge is critical when considering anthropogenic impacts on riverine systems especially in the face of major habitat destruction. These pressing threats mean that a comprehensive understanding of diversity is critical and fish checklists extremely relevant. Therefore, the present study provides a checklist of the fish species found in the Munim River Basin, Maranhão State, north-eastern Brazil, based on collected specimens.

New information

A total of 123 species were recorded for the Munim River Basin, with only two non-native species, Oreochromisniloticus and Colossomamacropomum, showing that the fish assemblage has relatively high ecological integrity. In addition, 29 species could not be identified at the species level, indicating the presence of species that are probably new to science in the Basin. A predominance of species belonging to the fish orders Characiformes and Siluriformes, with Characidae being recovered as the most species-rich family (21 species) agrees with the general pattern for river basins in the Neotropical Region. The total fish diversity was estimated by extensive fieldwork, including several sampling gears, carried out in different seasons (dry and rainy) and exploring different environments with both daily and nocturnal sampling, from the Basin's source to its mouth. A total of 84 sites were sampled between 2010 and 2022, resulting in 12 years of fieldwork. Fish assemblages were distinct in the Estuary and Upper river basin sections and more similar in the Lower and Middle sections indicating environmental filtering processes. Species were weakly nested across basin sections, but unique species were found in each section (per Simpsons Index). High variability of species richness in the Middle river basin section is likely due to microhabitat heterogeneity supporting specialist fish communities.

Building knowledge to save species: 20 years of ichthyological studies in the Tocantins-Araguaia River basin

Abstract: The Tocantins-Araguaia River basin is the largest basin located entirely in the Brazilian territory. The high degree of endemism of its ichthyofauna has been revealed in several studies, with the upper Tocantins River having the largest absolute number of endemic taxa within the Amazon basin. Here we provide an accurate review of the ichthyofauna of the Tocantins-Araguaia River basin, based on collections made between 2000-2020, including an extensive list of valid fish species occurring in the basin and a discussion of the major threats to its ichthyofauna. Ichthyofauna diversity was further refined based on web searches. Protected Areas and hydropower plants were mapped using shape files or coordinates from the responsible government agencies. 751 species of fishes are currently known from the Tocantins-Araguaia River basin. A considerable increase in fish diversity knowledge occurred in the last 20 years, in parallel with significant anthropic alterations in the basin and its surroundings. Dams constructed along the basin are ranked as the major threats to ichthyofauna. Although the drainage-basin holds several conservation units and indigenous lands, they have not been sufficient to guarantee the preservation of fish species. Our compilation emphasizes that the upper Tocantins River must be considered as a priority area to preserve fish species. Some mitigation actions that may achieve satisfactory results concerning ichthyofauna conservation are proposed.