Impact of biomass burning on a metropolitan area in the Amazon during the 2015 El Niño: The enhancement of carbon monoxide and levoglucosan concentrations

Biomass burning emissions in the Amazon caused a substantial degradation in the air quality of the Manaus Metropolitan Region (MMR) during the El Niño event of 2015. © 2020 Elsevier LtdExtreme droughts associated with changes in the climate have occurred every 5 years in the Amazon during the 21st century, with the most severe being in 2015. The increase in biomass burning (BB) events that occurred during the 2015 drought had several negative socioeconomic and environmental impacts, one of which was a decrease in the air quality. This study is an investigation into the air quality in the Manaus Metropolitan Region (MMR) (central Amazon, Brazil) during the dry (September to October) and wet (April to May) seasons of 2015 and 2016. A strong El Niño event began during the wet season of 2015 and ended during the wet season of 2016. Particulate matter samples were collected in the MMR during 2015 and 2016, and analyses of the satellite-estimated total carbon monoxide (CO) column and observed levoglucosan concentrations were carried out. Levoglucosan has been shown to be significantly correlated with regional fires and is a well-established chemical tracer for the atmospheric particulates emitted by BB, and CO can be treated as a gaseous-phase tracer for BB. The number of BB events increased significantly during the El Niño period when compared to the average number during 2003–2016. Consequently, the total CO column and levoglucosan concentration values in the MMR increased by 15% and 500%, respectively, when compared to the normal conditions. These results indicate that during the period that was analyzed, the impacts of BB were exacerbated during the strong El Niño event as compared to the non-El Niño period. In this study, we provided evidence that the air quality in the MMR will degrade in the future if droughts and BB occurrences continue to increase. © 2020 Elsevier Lt

What happens in the darkness? Seasonal variations in tropical benthic fish assemblages

Studies of fish assemblages have demonstrated that the main channels of rivers contain ichthyofauna adapted to this environment. However, information regarding the effects of temporal and spatial variations on this ichthyofauna is scarce. Using data from benthic fish assemblages in a major tributary of the Amazon basin collected during two consecutive receding and two rising water seasons, we tested the hypothesis that there are marked variations in community composition between the receding and rising water seasons. An asymmetry in predictability was detected among samples from the receding and rising seasons. Predictability in terms of species composition was higher for receding than rising seasons. The continual disassembly and reassembly cycles (due to dispersal) of local communities across a spatially heterogeneous landscape could explain this difference. Depth and dissolved oxygen affected the distribution of some benthic fish species during the rising seasons. This study highlights the important contribution of marginal wetlands to the benthic ichthyofauna inhabiting the main channel of the Purus River, as well as other major Amazonian rivers. © 2020 CSIRO

A new species in Simulium (Trichodagmia) (Diptera: Simuliidae) from Chapada Diamantina region, Brazil: cryptic diversity revealed by morphological and molecular evidence

We describe new species of black fly that had previously been identified as S. scutistriatum Lutz due to morphological similarities at the pupal stage. The description of the new species, Simulium (Trichogamia) itajara n. sp., is based on molecular and morphological evidences. The known distribution of the new species is currently restricted to the Paraguaçu River hydrographic basin in Chapada Diamantina National Park and the surrounded area in Bahia state, Brazil. The distribution record for S. scutistriatum in the northeast region of Brazil needs to be removed, since the previous records were based on occurrence of S. itajara n. sp

The Avifauna of the Rio Branco, an Amazonian evolutionary and ecological hotspot in peril

The Rio Branco is a river with unique biogeographic and ecological features, threatened by the Brazilian Government's plan to build a major hydroelectric dam and associated hydroway along its course. The river crosses one of Amazonia's largest rainfall gradients and a major geomorphological boundary along a savanna/forest ecotone, marked by the Bem Querer rapids. Above the rapids, the upper Rio Branco runs through the Boa Vista sedimentary formation and crosses the crystalline rocks of the Guiana Shield, and its margins are flanked by gallery forests. Downriver, it runs through a low-lying sedimentary basin, with Amazonian floodplain forests along its margins. Here, we present the results of ∼ 15 years of ornithological research on the Branco and its major tributaries, providing baseline data and evaluating potential threats to the riverine avifauna. Our surveys included opportunistic observations and standardized surveys along the entire length of the river in 16 systematically distributed localities. We catalogued 439 bird species, 87% of which are documented by physical evidence (specimens, recordings, photographs). Forty-six percent are restricted to single habitats, suggesting a high degree of habitat specialisation. A third of the species are widely distributed along the river, whereas 45% are restricted to either the upper or the lower Rio Branco, including 40 and 30 Indicator Species, respectively. Twenty-five species are threatened at global or national levels, including two 'Critically Endangered', nine 'Vulnerable', and 14 'Near Threatened'. We present a list of 50 bird species that are candidates for monitoring studies. Threats to the avifauna from dam construction include permanent flooding above the dam, eliminating gallery forests, river islands, and sandy beaches, and the disruption of the flood pulse along the river, affecting river island and floodplain forest specialists, many of which are globally threatened with extinction. If built, the Bem Querer dam will wipe out the ecotone region and affect dramatically the river's avifauna. © BirdLife International 2019

Small forest losses degrade stream macroinvertebrate assemblages in the eastern Brazilian Amazon

Generally, habitat loss and fragmentation negatively affect biota, often in nonlinear ways. Such nonlinear responses suggest the existence of critical limits for habitat loss beyond which taxa experience substantial changes. Therefore, we identified change points for aquatic macroinvertebrate assemblages at both local-riparian and catchment extents in response to a forest-loss gradient in agriculture-altered landscapes of 51 small (1st to 3rd Strahler order) eastern Amazon streams. We used Threshold Indicator Taxa Analysis (TITAN) to identify change points for individual taxa and segmented regression analysis for assemblage richness. Considering the patterns of the cumulative frequency distributions of sum(Z−) maxima across bootstrap replications, peak changes in macroinvertebrate assemblages were at ∼9% (5–95 percentiles = 1–15%) of forest-loss at the catchment extent, and at ∼1.4% (5–95 percentiles = 0–35%) of forest-loss at the local-riparian extent. Although the assemblage change point at the site extent was less than that detected at the catchment extent, the markedly lower percentile range indicates that biotic assemblages are more clearly responsive to forest-loss at the catchment/network-riparian extents than the site extent. For catchment and site extents, segmented regression analysis determined a change point for assemblage richness at 57% and 79% of forest-loss, respectively. This indicates the low capacity of total richness to separate early and synchronous decreases of sensitive taxa from gradual increases of tolerant taxa. Our results also show that it is not enough to focus management and conservation actions on riparian zones, but that conservation strategies should be expanded to entire catchments as well. The sharp decline of sensitive taxa in response to removal of a small portion of forest cover, even at catchment extents, indicates that the Brazilian Forest Code is insufficient for protecting stream macroinvertebrates. Consequently, we recommend strategies to reverse the potential collapse of aquatic biodiversity, particularly through avoiding deforestation and forest degradation, encouraging socio-economic incentives for restoring degraded areas, creating protected areas, and maintaining the current protected areas. We argue that reducing habitat loss should be a top priority for conservation planners in tropical forests because the sensitivity of aquatic biodiversity to removal of riparian forest-cover in Amazon rainforests is higher than previously thought. Therefore, the Forest Code regulatory framework needs complementary regulation that may be achived by more restrictive State and biome policies. © 2019 Elsevier Lt

How Habitat Filtering Can Affect Taxonomic and Functional Composition of Aquatic Insect Communities in Small Amazonian Streams

Responses in taxonomic and functional composition of communities were analysed in small Amazonian streams at the small and large scale (habitat patches, river segment scale, and catchment scale). We hypothesised that similar responses in community structure to local environmental factors were a correlation between taxonomic and functional composition. To evaluate the response of taxonomic composition to environmental variables, redundancy analysis (RDA) and RLQ analysis were performed to investigate the response of community abundance (L) as a function of the environment (R) and traits (Q). The fourth-corner analysis was applied to summarize specific interactions between environmental variables and traits. Then, community taxonomic composition was associated with models at multiple scales of habitat (i.e. riparian/channel, substrates, and water variables). Likewise, the fourth-corner tests and RLQ axes showed associations between trait composition and environmental variables related to variables, such as riparian cover and channel morphology followed by variation in substrate size and composition. Unexpectedly, these results did not show specific associations between unique environmental variables and traits. At last, results showed that local conditions of stream habitat regulated community structure and functional composition of aquatic insects. Thus, these findings indicate that the local environmental filtering appears to be strongly associated with selected species traits adapted to occur in a range of habitat conditions. Despite the low number of analysed streams, these results provide important information for understanding the simultaneous variation in functional trait composition and community composition of aquatic insect assemblages. © 2020, Sociedade Entomológica do Brasil