Showing papers by "Vera M. F. da Silva published in 2015"

Toxicity assessment of aqueous extracts of ash from forest fires

Abstract: Wildfires can cause immediate and drastic impacts on the structure and functioning of ecosystems, and there has been an increasing interest in wildfire effects on water chemistry and aquatic biota. Wildfires are increasingly recognized as a diffuse source of contamination of aquatic ecosystems, through the production of deleterious pyrolytic substances and their subsequent transport, mostly attached to ashes. To study the deleterious effects of the ash-laden runoff from burnt areas on water quality, composite ash samples of ashes were collected immediately after a forest fire and then used to prepare aqueous extracts of ash (AEA). The AEA were analyzed with respect to a large group of chemical elements and the sixteen prioritized polycyclic aromatic hydrocarbons (PAHs). Ca, S, Mg, K and Na were found to be the principal elements in the AEA, while only two low molecular weight PAHs (phenanthrene and naphthalene) were present in quantifiable amounts. In parallel, an ecotoxicological screening of the AEA was performed with four standard aquatic species from different functional groups and trophic levels. The AEA was found to induce a statistically significant decrease in the growth of two primary producers – Pseudokirchneriella subcapitata and Lemna minor – and inhibited the luminescence of the bacteria Vibrio fischeri . By contrast, AEA did not produce a significant immobilization of Daphnia magna suggesting that short-term acute toxicity may be absent at higher trophic levels. Overall, the present results emphasize the role of wildfires as a potential source of diffuse contamination for downstream water bodies, compromising both chemical and ecological conditions. At the same time, this study highlights the need for further research into the complexity of the potentially deleterious ecological effects of wildfires on aquatic communities, with a particular focus on cascading effects along the trophic web.

Living between rapids: genetic structure and hybridization in botos (Cetacea: Iniidae: Inia spp.) of the Madeira River, Brazil

Abstract: Until the recent construction of hydroelectric dams, a series of 18 rapids divided the upper and lower Madeira River, and these rapids were thought to separate two species of Amazonian freshwater dolphins (boto): Inia boliviensis (above) and I. geoffrensis (below). Some reports and articles, however, mention the occurrence of botos within the rapids region and that they occasionally cross the rapids, but without mentioning the species concerned. Based on our previous studies, it is likely that I. boliviensis occurs in the region of the rapids. To test this supposition, we sampled 18 individuals from this region, and collected mitochondrial (control region, cytochrome b and cytochrome oxidase I) and nuclear (10 microsatellite loci) DNA data, in order to test if there is connectivity between the dolphins that were found within the rapids region and dolphins collected upstream and downstream of the rapids, and investigate population structuring between these localities. All animals in our study were molecularly identified using three mitochondrial markers as belonging to the species I. boliviensis. Animals upstream of the Teotonio waterfall, the main and highest waterfall of the region, had nuclear genome of I. boliviensis, while most dolphins downstream of the waterfall had nuclear genome of I. geoffrensis. Inia boliviensis collected in the rapids region above the Teotonio waterfall belong to a management unit (MU) distinct from the I. boliviensis MU occupying Bolivian rivers. Downstream of Teotonio waterfall most dolphins are I. boliviensis/geoffrensis hybrids, with remaining individuals being migrant I. boliviensis. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 764–777.

Attitudes and behaviors toward Amazon River dolphins (Inia geoffrensis) in a sustainable use protected area

Abstract: Negative interactions between fishers and the Amazon River dolphin (Inia geoffrensis), or boto, have increased substantially in the last few decades. Herein, we investigate these interactions with focus on assessing fisher perceptions, attitudes, and behaviors toward botos. Moreover, we evaluate the effect that the Mamiraua Sustainable Development Reserve (MSDR) in the Brazilian Amazon, and related programs, has had on fisher attitudes and behaviors toward botos. The results suggest that interactions between fishers and botos, such as depredation and incidental entanglement, are frequent, and that the illegal harvest for botos, for use as bait, occurs in the majority of the study communities. However, the assessment revealed that most fishers have positive attitudes toward botos and that these attitudes have been influenced by participation in the MSDR activities such as research and ecotourism. Our results also highlight the importance of community-based enforcement in addressing the issue of boto harvesting. The MSDR programs have successfully promoted positive attitudes toward botos and have likely played a role in limiting boto mortality through behavioral controls, though the scope of influence of these programs has been restricted to a small geographical area. The current extent of these programs is insufficient to prevent the decline of the boto population; therefore, we suggest the MSDR model be used to improve and expand boto conservation efforts with communities in the region.

Amazon river dolphins (Inia geoffrensis) use a high-frequency short-range biosonar.

Abstract: Toothed whales produce echolocation clicks with source parameters related to body size; however, it may be equally important to consider the influence of habitat, as suggested by studies on echolocating bats. A few toothed whale species have fully adapted to river systems, where sonar operation is likely to result in higher clutter and reverberation levels than those experienced by most toothed whales at sea because of the shallow water and dense vegetation. To test the hypothesis that habitat shapes the evolution of toothed whale biosonar parameters by promoting simpler auditory scenes to interpret in acoustically complex habitats, echolocation clicks of wild Amazon river dolphins were recorded using a vertical seven-hydrophone array. We identified 404 on-axis biosonar clicks having a mean SL pp of 190.3±6.1 dB re. 1 µPa, mean SL EFD of 132.1±6.0 dB re. 1 µPa 2 s, mean F c of 101.2±10.5 kHz, mean BW RMS of 29.3±4.3 kHz and mean ICI of 35.1±17.9 ms. Piston fit modelling resulted in an estimated half-power beamwidth of 10.2 deg (95% CI: 9.6–10.5 deg) and directivity index of 25.2 dB (95% CI: 24.9–25.7 dB). These results support the hypothesis that river-dwelling toothed whales operate their biosonars at lower amplitude and higher sampling rates than similar-sized marine species without sacrificing high directivity, in order to provide high update rates in acoustically complex habitats and simplify auditory scenes through reduced clutter and reverberation levels. We conclude that habitat, along with body size, is an important evolutionary driver of source parameters in toothed whale biosonars.

Ba/Ca ratios in teeth reveal habitat use patterns of dolphins

Abstract: Teeth and otoliths are metabolically inert structures that preserve a chronology of chemical variations that may be related to the environmental histories experienced by each organism. Because of the natural decrease of barium (Ba) and increase of strontium (Sr) bioavail- ability in water with increasing salinity, these elements may be especially useful to track habitat use in aquatic organisms. Therefore, we tested whether the Ba/Ca and Sr/Ca ratios in the teeth of dolphins represent a salinity gradient. The main aim was to determine whether these elements can be used as a natural tag for different aquatic environments. Teeth from 2 freshwater dolphins (Inia geoffrensis and Sotalia fluviatilis) and 2 marine species (S. guianensis and Pontoporia blainvillei) from Brazil and Uruguay were analyzed using a Laser Ablation Inductively Coupled Plasma-Mass Spectrometer. Intensity ratios of 138 Ba/ 43 Ca and 86 Sr/ 43 Ca were measured along a line that covered all growth increments in the dentin from the second year of life onwards. Teeth from the freshwater species had mean Ba/Ca values tenfold higher than marine dolphins, confirm- ing the inverse relationship between salinity (and thus ambient Ba/Ca) and elemental ratios in teeth. Furthermore, Ba/Ca ratios could also differentiate dolphins from lower-salinity estuarine areas from those in areas with minimal freshwater discharge. No significant differences were found for Sr/Ca values. Results presented encouraging indications for the application of this tech- nique as a potential new tool for studying habitat use in aquatic mammals.

Acoustic characteristics of biosonar sounds of free-ranging botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the Negro River, Amazon, Brazil

Abstract: Odontoceti emit broadband high-frequency clicks on echolocation for orientation or prey detection. In the Amazon Basin, two odontoceti species, boto (Amazon River dolphin, Inia geoffrensis) and tucuxi (Sotalia fluviatilis), live sympatrically. The acoustic characteristics of the echolocation clicks of free-ranging botos and tucuxis were measured with a hydrophone array consisting of a full-band and an acoustic event recorder (A-tag). The clicks of the two species were short-duration broadband signals. The apparent source level was 201 dB 1 μPa peak-to-peak at 1 m in the botos and 181 dB 1 μPa peak-to-peak at 1 m in the tucuxis, and the centroid frequency was 82.3 kHz in the botos and 93.1 kHz in the tucuxis. The high apparent source level and low centroid frequency are possibly due to the difference in body size or sound production organs, especially the nasal structure, the sound source of clicks in odontoceti.