Temporal stability in fish assemblage isotopic niches : insights from a conservation reference river in southeastern Brazil

Globally, aquatic ecosystems are facing the highest levels of anthropogenic pressures ever. Thus, the characterization of environments with little or no impact becomes critically important for the development of sound conservation efforts. The Santo Antônio River, a tributary of the Doce River, has already been proposed as a priority area for conservation as it is an important free-flowing river with high biodiversity in the Rio Doce basin. This study aimed to characterize the trophic structure of the fish assemblage in the Santo Antônio River using stable carbon (δ13C) and nitrogen (δ15N) isotopes. We evaluated the temporal stability of isotopic metrics using data from sampling conducted in 2020 and 2022. Over the 2 years, a total of 24 fish species were collected. The fish community exhibited stability in isotopic parameters, despite temporal variation in species composition. The overall isotopic niche of the community varied minimally, showing substantial overlap (44%) between the 2-year values. The most important resources sustaining the community remained the same for most feeding guilds. Omnivores and invertivores primarily consumed aquatic invertebrates in both years, while piscivores relied on fish. Detritivores and herbivores fed mainly on periphyton in 2020 and on suspended material in 2022. Trophic diversity metrics remained stable. In general, despite some variations in collected species and assimilated items, the isotopic structure remained stable over time. Thus, these parameters can serve as a reference tool for comparison with other impacted sites in the basin and in so much-needed recovery efforts within the Doce River basin

Canopy characteristics and behavior of Nellore heifers in Brachiaria brizantha pastures under different grazing heights at a continuous stocking rate

The objective of this study was to evaluate the Brachiaria brizantha cv. Marandu canopy structure maintained at different grazing heights under a continuous stocking rate and with a dietary supplementation strategy for the animals during the rainy season. This study also intended to observe the relationships of these variables with the grazing behaviors of the heifers. The effects of three canopy heights (15, 25 and 35 cm) were evaluated in association with three types of supplements: one mineral and two protein/energy supplements, the first with a high rumen degradable protein and energy and the others with a low ratio. Both the protein/energy supplements were provided at 0.3% of body weight/day. The experimental design was completely randomized, with two replications and repeated measures, and took place during the period from January to April 2008. The supplementation strategies did not affect any variable related to the canopy structure. Total and green herbage masses and the ratio of green/dead material increased with canopy height. The leaf/stem ratio was higher in the lowest canopy height: 15 cm. Changes in the canopy structure caused variations in the grazing behavior of the animals. Animals maintained in the 15-cm-tall pasture grazed for a longer time, increasing the time for each meal, but the number of meals was lower than that of the animals grazing within the 35-cm-tall pasture. The grazing time of animals receiving the energy/protein supplement was lower only in the period of the day during which it was supplied. Canopy structure is affected by sward height, and changes animal behavior. Supplementation does not affect the canopy structure of the pastures with similar heights

Sigmoidal kinetics of anthocyanin accumulation during fruit ripening: A comparison between açai fruits (Euterpe oleracea) and other anthocyanin-rich fruits

AbstractAnthocyanins are natural colorants with increasing interest. Euterpe oleracea fruits (EOF) (açai) are an interesting phenolic compounds source. They are extremely rich in two anthocyanins: cyanidin-3-glucoside and cyanidin-3-rutinoside. In this study, the anthocyanin content was evaluated in EOF during their ripening, allowing to characterize very important parameters for the post-harvest industry: their maximum accumulation rate, per day, (Δy), their maximum concentration in fruits (CMAX) and the corresponding maturity class (S). Samples of 12 racemes from three plantations were collected twice a month during their ripening process. The maturity class of EOF was recorded at each harvesting and their anthocyanin content was determined by an HPLC method after solvent extraction. Anthocyanin accumulation was described (p<0.05) by sigmoidal equations and Δy, CMAX and S values were determined. The Δy of EOF reached 35.63mgkg−1fruitsday−1, whereas CMAX reached 1443mgkg−1 fruits. On average, in the beginning of maturation, both anthocyanins were present in similar proportions. However, in the last maturity stages, cyanidin-3-glucoside became less abundant than cyanidin-3-rutinoside. On the basis of the data available on strawberries, grapes, pomegranates and lychees, it was possible to verify that the sigmoidal mathematical model of anthocyanin accumulation is transposable