Leaching potential of S-metolachlor in a medium-textured Oxisol soil with bioindicator plants

ABSTRACT Information about the impact of herbicides in the soil based on the growth of bioindicator species is extremely useful in developing crop management strategies. Therefore, this study aims to evaluate the leaching potential of the herbicide S-metolachlor under different natural precipitations in medium-textured Oxisol using bioindicator plants. A completely randomized experimental design was adopted, with four replicates and treatments arranged in a 3 × 8 factorial scheme [three indexes of precipitation occurred in the environment before the collection of the samples (50, 91, and 131 mm) and eight depths in the soil profile (0-0.03; 0.03-0.06; 0.06-0.09; 0.09-0.12; 0.12-0.15; 0.15-0.20; 0.20-0.25; 0.25-0.30 m)]. PVC columns were used, maintaining the original soil integrity during sampling after accumulating the stipulated natural precipitation. Longitudinal sections separated the columns to sow the bioindicator species (cucumber, lettuce, Alexander grass, and sorghum). The phytotoxicity symptoms of bioindicator plants were evaluated, adopting a phytotoxicity visual scale between 0 and 100%, at 5, 7, 9, and 11 days after seeding. The responses of the bioindicator species to the residual effect of the herbicide S-metolachlor were variable and depended on the rainfall level. Generally, in a medium-textured Oxisol, the higher values of concentration of S-metolachlor occurs in depths ranging between 0 and 0.06 m. The maximum leaching depth detected was 0.12-0.15 m with 131 mm of precipitation. Cucumber was the most sensitive species to the presence of S-metolachlor in an Oxisol of medium-texture since it presents symptoms of phytotoxicity at higher depths.

Ant assemblages (Hymenoptera: Formicidae) from areas under the direct influence of two small hydropower plants in Brazil

Current energy production has been the subject of studies on environmental impacts and the need to adequately understand that the relationship to biodiversity loss is growing. One of the ways of assessing environmental changes is the use of bioindicator species, and ants represent an alternative in this regard. This study aimed to evaluate ant assemblages occurring in different environments in areas under the direct influence of two small hydropower plants (SHPP). Sampling was carried out using pitfall traps in forest and agricultural fragments, as well as pasture areas, along the Andrada River, municipality of Cascavel, state of Paraná, in July 2016 and March 2017. The sampled ant assemblages were evaluated for richness, abundance, and composition. The rarefaction analysis was used to compare the richness sampled in the two areas under direct influence. Abundance was analyzed based on the number of occurrences. The nonmetric multidimensional scaling (NMDS) was applied to test whether the abundance and composition of ant assemblages differ at the same site when sampled in both seasons. In total, 63 species belonging to 23 genera and 6 subfamilies were identified. The subfamily Myrmicinae was the most speciesrich (S = 25), followed by the subfamily Formicinae (S = 21). The most species-rich genus was Camponotus (S = 15) followed by Pheidole (S =11). A total of 41.3% richness was registered concurrently in the two assemblages. The study contributes to the expansion of knowledge of the ant fauna occurring in the state of Paraná and serves as a basis for monitoring impacts caused by the implementation of SHPP and other developments.

Checklist of bee species (Hymenoptera: Apoidea: Anthophila) in the urban areas of Cerrado in Barreiras, Bahia, Brazil

In a global context, few studies have investigated the effects of urbanization on apifauna, as well as the importance of green areas in urban centers for the conservation of local bee fauna. In Brazil, this line of research is still quite recent, with most studies carried out in regions with a predominance of the Atlantic Rainforest phytogeographic domain. For the Brazilian state of Bahia, such research is still scarce and, especially, if we consider the large territorial dimension that this state denotes. In the area that covers the Cerrado, few studies have been carried out that inventory the urban apifauna. In this paper we present a list of bee species recorded in urban areas of the city of Barreiras, Bahia, Brazil, which represent the first apifauna inventory in the Western region of Bahia. Specimens were collected fortnightly from November 2019 to April 2020, using two sampling methods: colored water traps (ARCAs/pantraps) and entomological net, in two remnants of vegetation used as sampling points. A total of 749 specimens were sampled, distributed in four families, 18 tribes, 29 genera, and 45 species. A total of 369 (49.3%) specimens were collected using the entomological net and 380 specimens (50.7%) by using the ARCAs. Our results showed that the area with the highest level of urbanization had bioindicator species of degraded environments, which benefit from urbanization, and despite the urban growth, the fragments found in the matrix can serve as a refuge for bee fauna, as long as they are well planned.

Is Your Moss Alive during Active Biomonitoring Study?

Biomonitoring was proposed to assess the condition of living organisms or entire ecosystems with the use of bioindicators—species sensitive to specific pollutants. It is important that the bioindicator species remains alive for as long as possible while retaining the ability to react to the negative effects of pollution (elimination/neutralization of hazardous contaminants). The purpose of the study was to assess the survival of Pleurozium schreberi moss during exposure (moss-bag technique) based on the measurement of the concentration of elements (Ni, Cu, Zn, Cd, and Pb), chlorophyll content, and its fluorescence. The study was carried out using a CCM-300 portable chlorophyll content meter, portable fluorometer, UV-Vis spectrophotometer, and a flame atomic absorption spectrometer. As a result of the laboratory tests, no significant differences were found in the chlorophyll content in the gametophytes of mosses tested immediately after collection from the forest, compared to those drying at room temperature in the laboratory (p = 0.175 for Student’s t-test results). Mosses exposed using the moss-bag technique of active biomonitoring were characterized by a drop in the chlorophyll content over 12 weeks (more than 50% and 60% for chlorophyll-a and chlorophyll-b, respectively). Chlorophyll content in mosses during exposure was correlated with actual photochemical efficiency (yield) of photosystem II (calculated value of Pearson’s linear correlation coefficient was 0.94—there was a significant correlation between chlorophyll a and yield p = 0.02). The highest metal increases in mosses (RAF values) were observed for zinc, lead, and copper after the second and third month of exposure. The article demonstrates that the moss exposed in an urbanized area for a period of three months maintains the properties of good bioindicator of environmental quality.

Effects of Cu, Zn and Their Mixtures on Bioaccumulation and Antioxidant Enzyme Activities in Galleria Mellonella L. (Lepidoptera: Pyralidae)

The effects of Cu, Zn and their mixture on bioaccumulation and antioxidant enzyme activities of midgut and fat body of Galleria mellonella larvae were investigated. The application of metals as a mixture showed a synergistic effect and the accumulation levels were increased in both tissues. Zn accumulation increased in midgut and fat body of G. mellonella larvae exposed to metal singly. On the other hand, Cu accumulation increased in midgut, while a decrease was observed in fat body exposed to Cu singly. Moreover, it was determined that oxidative stress was occured in midgut and fat body of G. mellonella larvae with significant decreases and increases in antioxidant and detoxification enzyme activities when fed singly and in mixture with different concentrations of Cu and Zn. Understanding the reactions of G. mellonella, which is a model organism showing immune system responses similar to vertebrates and bioindicator species, to metals by detoxification systems, which is an important parameter in insect physiology, is thought to contribute to future toxicological, genotoxic, physiological and ecotoxicological studies. G. mellonella larvae, which were used as a model organism, shows a similar reaction to mammals.