Spatial and temporal variability of light attenuation in large rivers of the Amazon

Costa, Maycira; Novo, Evlyn Márcia Leão de Moraes; Telmer, Kevin

doi:10.1007/s10750-012-1319-2

Cited by 47 publications

(62 citation statements)

References 43 publications

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“…On the other hand, impacted rivers, such as the Crepori (Class 4) and the Tocantins (Class 3), showed Z m /Z c of~2.0 during the high water level period, which suggests a reduction of light availability to half of the water column. Analogous restriction of light availability has been reported in the Amazon River and it is associated with the low chl-a concentration given that nutrients are not limited in these waters [24,32,50,56].…”

Section: Underwater Light Field and Phytoplanktonmentioning

confidence: 65%

“…In the Tapajós, for example Costa et al [32] observed, on average, lower acdom absorption (acdom (440) = 3.2 m −1 ) than values measured in black water rivers of the Amazon (8.6 m −1 ). As a result of the low TSS and acdom, the diffuse attenuation coefficient (Kd PAR) was reported at around 2.0 m −1 in both rising and falling periods, whereas for black and white Amazonian rivers, Kd increases to 3.7 and 5.1 m −1 , respectively [32].…”

Section: Methodsmentioning

confidence: 88%

“…Chlorophyll-a (chl-a) concentrations vary from 5.0 to 25.1 μg·L −1 [26,27], and cyanobacteria blooms related to urban-derived diffuse nutrient input at the margins of the Tapajós mouth (Santarém) have been reported [28]. In this section of the river, total suspended sediments (TSS) are composed primarily of fine matter discharged from upstream [29][30][31] reaching concentrations up to 4.1 mg·L −1 during rising and receding water levels [32]. In the Tapajós, for example Costa et al [32] observed, on average, lower acdom absorption (acdom (440) = 3.2 m −1 ) than values measured in black water rivers of the Amazon (8.6 m −1 ).…”

Section: Methodsmentioning

confidence: 99%

“…In this section of the river, total suspended sediments (TSS) are composed primarily of fine matter discharged from upstream [29][30][31] reaching concentrations up to 4.1 mg·L −1 during rising and receding water levels [32]. In the Tapajós, for example Costa et al [32] observed, on average, lower a cdom absorption (a cdom (440) = 3.2 m −1 ) than values measured in black water rivers of the Amazon (8.6 m −1 ). As a result of the low TSS and a cdom , the diffuse attenuation coefficient (K d PAR) was reported at around 2.0 m −1 in both rising and falling periods, whereas for black and white Amazonian rivers, K d increases to 3.7 and 5.1 m −1 , respectively [32].…”

Section: Study Areamentioning

confidence: 99%

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Effects of Small-Scale Gold Mining Tailings on the Underwater Light Field in the Tapajós River Basin, Brazilian Amazon

et al. 2017

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Artisanal and Small-scale Gold Mining (ASGM) within the Amazon region has created several environmental impacts, such as mercury contamination and changes in water quality due to increased siltation. This paper describes the effects of water siltation on the underwater light environment of rivers under different levels of gold mining activities in the Tapajós River Basin. Furthermore, it investigates possible impacts on the phytoplankton community. Two field campaigns were conducted in the Tapajós River Basin, during high water level and during low water level seasons, to measure Inherent and Apparent Optical Properties (IOPs, AOPs), including scattering (b) and absorption (a) coefficients and biogeochemical data (sediment content, pigments, and phytoplankton quantification). The biogeochemical data was separated into five classes according to the concentration of total suspended solids (TSS) ranging from 1.8 mg·L −1 to 113.6 mg·L −1 . The in-water light environment varied among those classes due to a wide range of concentrations of inorganic TSS originated from different levels of mining activities. For tributaries with low or no influence of mining tailings (TSS up to 6.8 mg·L −1 ), waters are relatively more absorbent with b:a ratio of 0.8 at 440 nm and b 660 magnitude of 2.1 m −1 . With increased TSS loadings from mining operations (TSS over 100 mg·L −1 ), the scattering process prevails over absorption (b:a ratio of 10.0 at 440 nm), and b 660 increases to 20.8 m −1 . Non-impacted tributaries presented a critical depth for phytoplankton productivity of up to 6.0 m with available light evenly distributed throughout the spectra. Whereas for greatly impacted waters, attenuation of light was faster, reducing the critical depth to about 1.7 m, with most of the available light comprising of red wavelengths. Overall, a dominance of diatoms was observed for the upstream rivers, whereas cyanobacteria prevailed in the low section of the Tapajós River. The results suggest that the spatial and temporal distribution of phytoplankton in the Tapajós River Basin is not only a function of light availability, but rather depends on the interplay of factors, including flood pulse, water velocity, nutrient availability, and seasonal variation of incoming irradiance. Ongoing research indicates that the effects of mining tailings on the aquatic environment, described here, are occurring in several rivers within the Amazon River Basin.

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Section: Underwater Light Field and Phytoplanktonmentioning

confidence: 65%

Section: Methodsmentioning

confidence: 88%

Section: Methodsmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

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Effects of Small-Scale Gold Mining Tailings on the Underwater Light Field in the Tapajós River Basin, Brazilian Amazon

et al. 2017

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“…Gymnotiforms inhabit the Amazon and Orinoco drainage basins where short-wavelength light is attenuated; depending on water clarity and the presence of particulates or phytoplankton, green-red or red light transmits best [Costa et al, 2013]. Despite the loss of SWS1 and SWS2 cone opsins and the lack of green cones, the retention of LWS cones assures the gymnotiform retina will be optimally sensitive to the dominant light spectrum in their habitat during the daytime.…”

Section: Gymnotiforms Retain the Optimal Cone Opsin For Their Habitatmentioning

confidence: 99%

South American Weakly Electric Fish (Gymnotiformes) Are Long-Wavelength-Sensitive Cone Monochromats

Liu

Yan

et al. 2016

Brain Behav Evol

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Losses of cone opsin genes are noted in animals that are nocturnal or rely on senses other than vision. We investigated the cone opsin repertoire of night-active South American weakly electric fish. We obtained opsin gene sequences from genomic DNA of 3 gymnotiforms (Eigenmannia virescens, Sternopygus macrurus, Apteronotus albifrons) and the assembled genome of the electric eel (Electrophorus electricus). We identified genes for long-wavelength-sensitive (LWS) and medium-wavelength-sensitive cone opsins (RH2) and rod opsins (RH1). Neither of the 2 short-wavelength-sensitive cone opsin genes were found and are presumed lost. The fact that Electrophorus has a complete repertoire of extraretinal opsin genes and conservation of synteny with the zebrafish (Danio rerio) for genes flanking the 2 short-wavelength-sensitive opsin genes supports the supposition of gene loss. With microspectrophotometry and electroretinograms we observed absorption spectra consistent with RH1 and LWS but not RH2 opsins in the retinal photoreceptors of E. virescens. This profile of opsin genes and their retinal expression is identical to the gymnotiform's sister group, the catfish, which are also nocturnally active and bear ampullary electroreceptors, suggesting that this pattern likely occurred in the common ancestor of gymnotiforms and catfish. Finally, we noted an unusual N-terminal motif lacking a conserved glycosylation consensus site in the RH2 opsin of gymnotiforms, a catfish and a characin (Astyanax mexicanus). Mutations at this site influence rhodopsin trafficking in mammalian photoreceptors and cause retinitis pigmentosa. We speculate that this unusual N terminus may be related to the absence of the RH2 opsin in the cones of gymnotiforms and catfish.

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Influence of summertime mesoscale convective systems on the heat balance and surface mixed layer dynamics of a large Amazonian hydroelectric reservoir

et al. 2014

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We evaluated the impacts of summertime mesoscale convective systems (MCS) on the heat balance and diel surface mixed layer (SML) dynamics of the Brazilian Amazon's Tucuru ı Hydroelectric Reservoir (THR). We used a synergistic approach that combines in situ data, remote sensing data, and three-dimensional (3-D) modeling to investigate the typical behavior of the components of the heat balance and the SML dynamics. During the study period (the austral summer of 2012-2013), 22 days with MCS activity were identified. These events occurred approximately every 4 days, and they were most frequent during January (50% of the observations). An analysis of local meteorological data showed that when MCS occur, the environmental conditions at THR change significantly (p-value < 0.01). The net longwave flux, which was the heat balance component most strongly impacted by MCS, increased more than 32% on days with MCS activity. The daily integrated heat balance became negative (254 W m 22) on MCS days, while the balance was positive (19 W m 22) on non-MCS days. In response to the changes in the heat balance, the SML dynamics changed when a MCS was over the THR. The SML depth was typically 28% higher on the days with MCS ($1.6 m) compared with the days without MCS ($1.3 m). The results indicate that MCS are one of the main meteorological disturbances driving the heat balance and the mixing dynamics of Amazonian hydroelectric reservoirs during the summer. These events may have implications for the water quality and greenhouse gas emissions of Amazonian reservoirs.

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Spatial and temporal variability of light attenuation in large rivers of the Amazon

Cited by 47 publications

References 43 publications

Effects of Small-Scale Gold Mining Tailings on the Underwater Light Field in the Tapajós River Basin, Brazilian Amazon

Effects of Small-Scale Gold Mining Tailings on the Underwater Light Field in the Tapajós River Basin, Brazilian Amazon

South American Weakly Electric Fish (Gymnotiformes) Are Long-Wavelength-Sensitive Cone Monochromats

Influence of summertime mesoscale convective systems on the heat balance and surface mixed layer dynamics of a large Amazonian hydroelectric reservoir

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