Assessment of Nitrogen and Phosphorus Pathways at the Profile of Over-fertilised Alluvial Soils. Implications for Best Management Practices

Contrasting soil profiles (coarse-textured and fine-textured) treated with brilliant blue (BB) dye tracer, inorganic nitrogen (N) and phosphorus (P) concentrations along and between stained preferential flow pathways were examined for an irrigated and overfertilised maize monoculture system at the Mediterranean central Chile. The PO4-P concentrations were 2- to 10-fold higher in areas with BB than in areas without BB below 0.5-m soil depth in both soils. This elevated concentration was attributed to transport through cracks in fine-textured soil and finger flow in coarse-textured soil. The highest PO4-P value (13 mg kg^?1) was found in areas with BB at the fine-textured soil. There were no significant differences in inorganic N concentration between areas with and without BB for both soils, which suggest that the effects of preferential flow are less important for inorganic N forms. There was a strong significant (p?<?0.01) positive correlation between PO4-P and NH4-N concentrations in the fine-textured soil, and the amounts retained were clearly proportional to the clay content. Strategies for reducing N and P losses must be placed on good agronomic management of irrigated maize cropping system including accurate calculation of N and P fertiliser rates and establishment of suitable mitigation measures such as cover cropping.     

文化遗产保护区景观格局演变及驱动因子研究———以丽江市核心区为例

以丽江市核心范围为研究区,对其1996、2006及2016年遥感影像进行景观分类,以Google Earth 19级高分辨率影像图对结果校正并计算景观格局指数.结果表明:1996-2006年,冰川雪域向林地转换明显,旱地向建设用地转换趋势明显;2006-2016建设用正向转换明显,其中水田是建设用地增长的主要来源;林地一直是研究区的优势景观类型,比例保持64%以上.20年间,城镇景观用地的扩张蚕食了周围的优质农田景观用地,建设用地扩张有明显的区位特征.研究区的景观破碎度呈现先增后减的倒"U"形变化,景观蔓延度指数和破碎度呈联动变化,先增后减,香浓多样性指数则先减后增.旅游综合收入、政策是影响景观格局变化的主要因素,基于研究区的特殊性,提出构建复合型"生态-遗产廊道".     

A Novel Semi-bionanofibers through Introducing <Emphasis Type="Italic">Tragacanth Gum</Emphasis> into PET Attaining Rapid Wetting and Degradation

Untreated polyethylene terephthalate has limitation in some medical applications, such as wound dressing due to the hydrophobic property. Thereby, Tragacanth Gum (TG) as a natural polysaccharide utilized in polymer solution led to novel semi-bionanofibers of PET/TG blends (15:1, 15:2 and 15:3) through electrospinning method. Fourier transform infrared spectroscopy results confirmed the existence of hydrophilic groups of TG such as hydroxyl groups. Moreover, twice water uptake of PET/TG comparing with PET nanofibers indicated the hydrogel properties, also PET/TG nanofibers possessed high surface wettability through reduction of contact angle from 113 to 0°. Further, differential scanning calorimetry analysis indicated the alteration in the crystalline structure of PET/TG nanofibers that led to faster degradation in various pH values. The SEM images of PET/TG nanofibers displayed the greater average diameter with increasing TG content (283 nm) comparing with PET nanofibers (193 nm). Also introducing more TG in the nanofibers exhibited lower mechanical properties.     

Towards the identification of ecological management units: A multidisciplinary approach for the effective management of bottlenose dolphins in the southern Iberian Peninsula

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Persistence of submerged macrophytes in a drying world: Unravelling the timing and the environmental drivers to produce drought‐resistant propagules

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Gut microbiota and gut morphology of gilthead sea bream (Sparus aurata) juveniles are not affected by chromic oxide as digestibility marker

The present work aimed to evaluate whether the use of chromic oxide (Cr₂O₃) as dietary inert marker in fish digestibility studies interferes with gut microbial community modulation and gut morphology. To assess the effects of Cr₂O₃ under potential diverse microbiota populations, dietary Cr₂O₃ was tested using challenging plant feedstuffs (PF)‐based diets supplemented or not with prebiotics, as prebiotics are expected to modify gut microbiota populations. For that purpose, three diets were formulated to include circa 20:80 fish meal and PF as protein sources, without (CTR) or with prebiotic supplementation (10 g/kg XOS or GOS). These diets did not include Cr₂O₃ (?Cr₂O₃ diets). Three similar additional diets were formulated to include 5 g/kg Cr₂O₃ (+Cr₂O₃ diets). Cr₂O₃ effects on gut microbiota were assessed for the first time in the allochthonous (digesta) and autochthonous (mucosa) community by a culture‐independent molecular approach, using denaturing gradient gel electrophoresis (DGGE). No differences in gut bacterial profiles (number of operational taxonomic units, microbiota richness, diversity and similarity indices) were observed between dietary treatments. No significant alterations in submucosa layer structure, enterocytes and eosinophilic granular cells structure, goblet cells and leucocytes quantity were detected in the distal intestine among diets. In conclusion, data indicate that dietary inclusion of 5 g/kg Cr₂O₃ does not interfere with gilthead sea bream (Sparus aurata) gut microbiota and gut morphology, suggesting that a dietary incorporation level of 5 g/kg Cr₂O₃ can safely be used as inert marker in digestibility studies.     

Moderate salinities enhance growth performance of Nile tilapia (Oreochromis niloticus) fingerlings in the biofloc system

The biofloc technology (BFT) has recently gained attention as an economic and environmentally sustainable system for aquaculture. The use of BFT with salinized water could be used to minimize the negative effects of nitrogenous waste and improve the growth performance of Nile tilapia. This work evaluated the growth performance, survival, gill lesions, and fillet composition of tilapia fingerlings (Oreochromis niloticus) reared during 70 days with different salinities (0, 4, 8, 12, and 16 g/L) in a biofloc previously developed. The results indicated that the use of mature bioflocs alone was sufficient to avoid fingerling mortality due to nitrite peaks. Moreover, the salinized water, especially between 4 and 8 g/L (maximum points around 6 g/L), can be recommended in BFT to improve the growth performance of tilapia in the initial culture phase. The salinity level that was evaluated did not affect fillet composition nor the occurrence of gill lesions. The total ammonia nitrogen concentration was lower in freshwater than in salinized water (p < 0.05). Nitrite peaks in salinities of 12 and 16 g/L appeared later and were higher in comparison to other treatments. Considering minimal water exchange in BFT, the use of salinized water in this system may be environmentally viable.     

Crude protein levels in diets for two growth stages of Nile tilapia (Oreochromis niloticus) in a biofloc system

Biofloc technology (BFT) provides an additional feed source for aquatic organisms through the conversion of waste in microbial flocs. Because of this, the suitable protein level in a diet for animals in this system could be different from those in conventional systems. Our objective was to determine the suitable protein level in the diet of Nile tilapia juveniles reared with BFT. Two experiments were carried out with tilapia weighing ~10 g (first experiment) and about 50 g (second experiment) during 61 and 98 days respectively. Five crude protein (CP) levels (within 17% and 33%) were tested. The increment of CP resulted in a reduction in dissolved oxygen, pH, alkalinity and an increase in dissolved phosphorus, total suspended solids and total ammonium nitrogen. The crude protein level had a significant effect (p < 0.05) on animal performance. The linear response plateau model was the best fit for the final weight and weight gain data in the two growth phases. In conclusion, tilapia juveniles of 10–60 g and 60–230 g in biofloc can be fed on diets with 28% of CP (26% of digestible protein) and 22% CP (20% of digestible protein) respectively.     

Investment analysis of marine cage culture by applying bioeconomic reference points: A case study of the spotted rose snapper (Lutjanus guttatus) in Mexico

In Mexico, marine finfish cage culture is envisioned as an economic alternative for coastal fishermen. Because research and outreach have not yet proved that this is profitable, assessing the investment through financial risk assessment and setting reference points for expected outcomes is useful. For Lutjanus guttatus, this research reports on a 10-year investment analysis of a pilot-scale, ongrowing four-cage module tested in Mazatlán, Mexico that incorporated a) hatchery-reared fry, b) species-specific feed and c) a second-generation prototype cage, all of them results of almost a decade of research. Two production scenarios were examined: Scenario I, with a high survival rate (90%–95%) and a low feed conversion ratio (FCR) (1.4–1.7), and Scenario II, with a low survival rate (67%–75%) and a high FCR (1.8–2.0). The net present value results are positive for Scenario I (mean?=?US$134,709, and a 95% probability interval (PI) [US$91,621; US$176,436]) and negative for Scenario II (mean?=?US-$79,082, 95% PI [US-$116,140; US-$42,054]). To identify feasibility improvement, reference points (threshold values) for survival, FCR, fry and feed costs were determined.     

<Emphasis Type="Italic">Er3</Emphasis> gene,conferring resistance to powdery mildew in pea,is located in pea LGIV

Three genes for resistance to Erysiphe pisi, named er1, er2 and Er3 have been described in pea so far. er1 gene is located in pea linkage group VI, while er2 gene has been mapped in LGIII. SCAR and RAPD markers tightly linked to Er3 gene have been identified, but the position of these markers in the pea genetic map was unknown. The objective of this study was to localize Er3 gene in the pea genetic map. Towards this aim, the susceptible pea cv. Messire (er3er3) and a resistant near isogenic line of Messire (cv. Eritreo, Er3Er3) were surveyed with SSRs with known position in the pea map. Three SSRs were polymorphic between “Messire” and “Eritreo” and further surveyed in two contrasting bulks formed by homozygous Er3Er3/er3er3 individuals obtained from a F₂ population derived from the cross C2 (Er3Er3)?×?Messire (er3er3). A single marker, AA349, was polymorphic between the bulks. Subsequently, other ten markers located in the surrounding of AA349 were selected and analysed in Er3Er3 and er3er3 plants. As a results, another SSR, AD61, was found to be polymorphic between Er3Er3 and er3er3 plants. Further linkage analysis confirmed that SSRs AA349 and AD61 were linked to Er3 and to the RAPD and SCAR markers previously reported to be linked to this gene. Er3 gene was located in pea LGIV at 0.39 cM downstream of marker AD61. The location of Er3 gene in the pea map is a first step toward the identification of this gene.