Simultaneous Biodegradation and Detoxification of the Herbicides 2,4-Dichlorophenoxyacetic Acid and 4-Chloro-2-Methylphenoxyacetic Acid in a Continuous Biofilm Reactor

The herbicides 2,4-diclorophenoxiacetic and 4-chloro-2-methylphenoxyacetic acids (2,4-D and MCPA) are widely used in agricultural practices worldwide. Not only are these practices responsible of surface waters contamination, but also agrochemical industries through the discharge of their liquid effluents. In this investigation, the ability of a 2,4-D degrading Delftia sp. strain to degrade the related compound MCPA and a mixture of both herbicides was assessed in batch reactors. The strain was also employed to remove and detoxify both herbicides from a synthetic effluent in a continuous reactor. Batch experiments were conducted in a 2-L aerobic microfermentor, at 28 °C. Continuous experiments were carried out in an aerobic downflow fixed-bed reactor. Bacterial growth was evaluated by the plate count method. Degradation of the compounds was evaluated by UV spectrophotometry, gas chromatography (GC), and chemical oxygen demand (COD). Toxicity was assessed before and after the continuous process by using Lactuca sativa seeds as test organisms. Delftia sp. was able to degrade 100 mg L^?1 of MCPA in 52 h. When the biodegradation assay was carried out with a mixture of 100 mg L^?1 of each herbicide, the process was accomplished in 56 h. In the continuous reactor, the strain showed high efficiency in the simultaneous removal of 100 mg L^?1 of each herbicide. Removals of 99.7, 99.5, and 95.0% were achieved for 2,4-D, MCPA, and COD, respectively. Samples from the influent of the continuous reactor showed high toxicity levels for Lactuca sativa seeds, while toxicity was not detected after the continuous process.     

Environmental disturbance and chironomid palaeodiversity: 15 kyr BP of history at Lake Mascardi,Patagonia, Argentina

1. Palaeoecological records may be useful in predicting the ecological outcomes for certain communities exposed to natural and human disturbance. In turn, theoretical work has emphasized the importance of baseline information on diversity to establish precise conservation and restoration policies. 2. Lake sediments provide good evidence of long-term changes in community composition, especially of insects from the family Chironomidae. Midge fauna is highly diverse and their remains are well preserved in sequential order allowing the construction of past assemblages. 3. To assess long-term community trends and stability in an environment virtually free from human impact, fossil midge assemblages were collected from a sediment core at Lake Mascardi (Río Negro, Argentina). Shannon's diversity index as well as rank-abundance relationships were estimated for core subsamples (10 cm slices), using a ‘taxonomic minimalist’ approach. 4. Diversity levels are relatively constant along the core. However, sharp reductions in diversity and equitability in midge assemblages are recorded. These reductions appear to be related to natural variability—mainly ash falls (pulse) and climatic (press) disturbing events. During pulse disturbances, both diversity and equitability fall, recovering rapidly after pressure is released. During press events (long-term disturbances) equitability falls whereas diversity remains fairly constant. Subfamily succession between pulse disturbances, follows proposed ecological species rank-abundance models. 5. These findings suggest that at long time-scales, a low level of taxonomic detail may be adequate for the analysis of community responses to environmental change. © 1998 John Wiley & Sons, Ltd.     

Changes in hydrophilic and lipophilic antioxidant activity in relation to their phenolic composition during the chamber drying of red grapes at a controlled temperature

The purpose of this work was to study the variation of phenol compounds, as measured by HPLC, during the chamber drying under controlled temperature conditions of red grapes of the Merlot and Tempranillo varieties in relation to antioxidant activity. Both lipophilic and hydrophilic antioxidant activities in these grapes increased during the drying process; the former was measured via proton transfer in the coupled oxidation reaction between linoleic acid and β-carotene, and the second via electron transfer in the DPPH assay. The hydrophilic component was invariably greater in Tempranillo grapes, and so was the lipophilic component in Merlot grapes. Only the increase in hydrophilic antioxidant activity obtained a significant correlation with the phenolic compounds during the drying process. However, based on the phenolic fraction analysis, this result was primarily due to phenolic polymers and, to a lesser extent, also to phenolic acids, flavans, and some flavonols and anthocyans.     

Chemical composition,in vitro gas production,methane production and fatty acid profile of canola silage (Brassica napus) with four levels of molasses

The objective of this study was to investigate the effect of four levels of molasses on chemical composition, in vitro digestibility, methane production and fatty acid profile of canola silages. A canola (Brassica napus var. Monty) crop was established in a small-scale agricultural farm and harvested 148 days after sowing. Four levels of molasses were tested with respect to the fresh weight (1.5 kg); these were 1% (CS-1), 2% (CS-2), 3% (CS-3) and 4% (CS-4) molasses, and 0% molasses (CS-0) was included as a control. A total of 45 microsilages were prepared using PVC pipes (4 in. of diameter × 20 cm of length), and the forage was compressed using a manual press. The effects of control and treatments were tested using the general linear model Y?=?μ?+?T_i?+?E_ij. The linolenic acid (C18:3n3), palmitic acid (C16:0) and linoleic acid methyl ester (C18:2n6c) accounted for 30%, 21% and 10.5% of total fatty acids, respectively; the fermentation parameters and in vitro methane production were not affected (P?>?0.05) by treatments; in vitro digestibility decreased significantly (P?<?0.05) as the level of molasses increased. It was concluded that CS-4 improved the DM content by 9% and showed high content of linolenic acid methyl ester. The gross energy of canola silages could favour the oleic acid methyl ester.

     

Evaluation of post-emergence herbicides for the control of wild oat (Avena fatua L.) in wheat and barley in Argentina

Wild oat (Avena fatua L.) is the most troublesome weed in cereal crops in Argentina. With the aim of studying the effects of different herbicides, doses, and wild oat growth stage at application on weed control and crop yield, field experiments were conducted in wheat and barley crops during three growing seasons in the south of Buenos Aires Province, Argentina. Treatments were post-emergence applications of new herbicide, pinoxaden + cloquintocet mexyl (5%-1.25%), at doses that ranged from 20 g to 60 g a.i. pinoxaden ha⁻¹, applied at two to three leaves and the beginning of tillering of wild oat. In addition, standard treatments were included and applied at the same wild oat growth stages. Diclofop methyl at 511 g a.i. ha⁻¹ and fenoxaprop-p-ethyl at 55 g a.i. ha⁻¹ were applied in barley. In wheat, diclofop methyl was replaced by clodinafop-propargyl + cloquintocet mexyl (24%-6%) at 36 g a.i. clodinafop-propargyl + 9 g cloquintocet mexyl ha⁻¹ and in 2008/09 wheat experiments, iodosulfuron plus metsulfuron methyl (5%-60%) at 3.75 g a.i. ha⁻¹ + 3 g a.i. ha⁻¹ also was included. In both crops, pinoxaden at 30 g a.i. ha⁻¹ and at higher rates, fenoxaprop-p-ethyl and clodinafop-propargyl gave the best control of wild oat. In 2006/07 wheat crops, treatments applied at tiller initiation provided better control than the early timing averaged across herbicides. However, wheat yield generally was greater with early application. In barley, wild oat control and crop yield were similar regarding time of application. Variations in crop yield were correlated with grain number m⁻² both in wheat and barley, but relationships between both grain number and spikes m⁻² and with grains per spike were identified only in wheat.     

Plant and animal endemism in the eastern Andean slope: challenges to conservation

Background

The Andes-Amazon basin of Peru and Bolivia is one of the most data-poor, biologically rich, and rapidly changing areas of the world. Conservation scientists agree that this area hosts extremely high endemism, perhaps the highest in the world, yet we know little about the geographic distributions of these species and ecosystems within country boundaries. To address this need, we have developed conservation data on endemic biodiversity (~800 species of birds, mammals, amphibians, and plants) and terrestrial ecological systems (~90; groups of vegetation communities resulting from the action of ecological processes, substrates, and/or environmental gradients) with which we conduct a fine scale conservation prioritization across the Amazon watershed of Peru and Bolivia. We modelled the geographic distributions of 435 endemic plants and all 347 endemic vertebrate species, from existing museum and herbaria specimens at a regional conservation practitioner's scale (1:250,000-1:1,000,000), based on the best available tools and geographic data. We mapped ecological systems, endemic species concentrations, and irreplaceable areas with respect to national level protected areas.

Results

We found that sizes of endemic species distributions ranged widely (< 20 km² to > 200,000 km²) across the study area. Bird and mammal endemic species richness was greatest within a narrow 2500-3000 m elevation band along the length of the Andes Mountains. Endemic amphibian richness was highest at 1000-1500 m elevation and concentrated in the southern half of the study area. Geographical distribution of plant endemism was highly taxon-dependent. Irreplaceable areas, defined as locations with the highest number of species with narrow ranges, overlapped slightly with areas of high endemism, yet generally exhibited unique patterns across the study area by species group. We found that many endemic species and ecological systems are lacking national-level protection; a third of endemic species have distributions completely outside of national protected areas. Protected areas cover only 20% of areas of high endemism and 20% of irreplaceable areas. Almost 40% of the 91 ecological systems are in serious need of protection (= < 2% of their ranges protected).

Conclusions

We identify for the first time, areas of high endemic species concentrations and high irreplaceability that have only been roughly indicated in the past at the continental scale. We conclude that new complementary protected areas are needed to safeguard these endemics and ecosystems. An expansion in protected areas will be challenged by geographically isolated micro-endemics, varied endemic patterns among taxa, increasing deforestation, resource extraction, and changes in climate. Relying on pre-existing collections, publically accessible datasets and tools, this working framework is exportable to other regions plagued by incomplete conservation data.     

Immune responses and gut morphology in Senegalese sole (Solea senegalensis) fed dietary probiotic supplementation and following exposure to Photobacterium damselae subsp. piscicida

The aim of this study was to determine the effect of a dietary multi‐species probiotic on growth, gut morphology and immune parameters in Senegalese sole (Solea senegalensis). Fish were fed with two experimental diets, a control diet and the same diet supplemented with the probiotic for 72 days. A sub‐lethal bath challenge with Photobacterium damselae subsp. piscicida was performed after the growth trial. Intestine and blood samples were collected to study gut structure and plasmatic immune parameters. No significant differences were found in growth performance. The analysis of gut morphology showed a significant increase in intestinal villi height of Senegalese sole fed the probiotic. Regarding circulating leucocytes, dietary probiotic supplementation increased thrombocytes levels whereas a decrease in the proportion of lymphocytes was observed. No significant differences were observed in humoural immune parameters. Bath challenge differentially affected leucocyte counts and increased peroxidase activity. This study presents the possibility of using dietary probiotic supplementation to increase Senegalese sole welfare since gut morphology was positively affected. Although the immune response after a bacterial challenge was not modulated by dietary treatment, further studies would be instrumental to unravel eventual dietary benefits on immune mechanisms.