Simulated nitrogen deposition affects soil fauna from a semiarid Mediterranean ecosystem in central Spain

Nitrogen (N) deposition is a major threat to the semiarid Mediterranean ecosystems. We simulated a gradient of N deposition (0, 10, 20 and 50 kg N ha^?1 year^?1?+?6.4 kg N ha^?1 year^?1 ambient deposition) in a Mediterranean shrubland from central Spain. In autumn 2011 (after 4 years of experimental duration), soil cores were taken to extract the soil fauna. Acari (45.54%) and Collembola (44.00%) were the most represented taxonomical groups, and their abundance was negatively related to soil pH. Simulated N deposition had an impact on the total number of individuals in soil as well as on Collembola and Pauropoda abundance. Collembola abundance increased with N loads up to 20 kg N ha^-1 year^-1 and then decreased. This response was attributed to soil acidification (between 0 and 20 kg N ha^-1 year^-1) and increased soil ammonium (between 20 and 50 kg N ha^-1 year^-1). Pauropoda were favoured by additions of 50 kg N ha^-1 year^-1, and it was the only taxonomical group whose abundance was exclusively related to N deposition, suggesting their potential as bioindicators. Contrary to predictions, there was a negative relationship between soil faunal abundance and plant diversity. In conclusion, soil faunal communities from semiarid Mediterranean ecosystems in central Spain seem to be primarily influenced by soil chemistry (mainly pH) but are also susceptible to increased N deposition. The main drivers of change under increased N deposition scenarios seem to be soil acidification and increased ammonium in soils where nitrate is the dominant mineral N form.     

Potential use of rare earth oxides as tracers of organic matter in grassland

Tracing organic matter (OM) in soil is challenging, because runoff and leaching processes are interrelated and have multiple sources. Therefore, multiple tracers with low background concentrations such as rare earth element oxides (REOs) are necessary to delineate the origin of sources of the organic materials in groundwater, rivers or in catchments. The main objective of this study was to examine the potential use of REOs as a tracer in various forms of OM (1) whole slurry, (2) solid, and (3) liquid phase of cattle slurry after mechanical separation. A laboratory experiment was carried out using five REOs (La, Gd, Sm, Pr, and Nd oxides) mixed directly into soil or mixed with various fractions of cattle slurry and then applied to the soil surface. In the additional grassland experiment, Gd oxide was spiked with soil and cattle slurry and then applied to the soil surface. The mineral N in the liquid phase (urine) of the slurry in the grassland experiment was labelled with ¹⁵N urea (16 atom%). In the laboratory experiment, results showed that the five REOs concentration of soil in 0–1 cm soil section after the rainfall simulation was still up to 20 times more than the background values. In 1–2 cm soil section, the concentration of only Gd (two fold higher) and La oxides (50% higher) were significantly higher than the soil background values. Therefore, we hypothesized that Gd and La oxides were associated also with relatively finer organic particles in slurry, thus 1–2 cm soil section were enriched with these oxides. The five REOs concentration below 2 cm soil depth were similar to the background values in all treatments. In line with the laboratory experiment, Gd concentrations in the deeper soil layers (2–4 and 4–8 cm) in the grassland experiment were not significantly affected by any treatment. Both in grassland and laboratory experiment, solid phase of the slurry (dung) was collected from the soil surface after rainfall simulation. Here, about 56% of REOs were measured on the solid phase of the slurry which indicates the strong binding potential of REOs on slurry OM. The present novel study, where REO tagged slurry was uniquely tested to study geochemical cycle of organic fertilizers, clearly highlighted the potential for their use as multiple‐tracers of (animal derived‐) OM in agricultural soils.     

Cytochemical reactions in cells from leukemic dogs

Leukemic cells from 17 dogs with spontaneous leukemia were stained with leukocyte alkaline phosphatase, alpha naphthyl acetate esterase with and without fluoride, peroxidase, and periodic acid-Schiff. Cytochemistry was necessary for identification or confirmation of leukemic cell type in most dogs and resulted in changing the light microscopic morphologic diagnosis in eight of 17 dogs. Leukemic cell types diagnosed were myelomonocytic leukemia in seven dogs, monocytic leukemia in five dogs, lymphocytic leukemia in four dogs, and myelocytic leukemia in one dog.     

Growth, Survival, and Feed Conversion Rates of Hatchery-Reared Mutton Snapper Lutjanus analis Cultured in Floating Net Cages

Abstract.— The aquaculture performance of mutton snapper Lutjanus analis raised in floating net cages was assessed by measuring their growth, survival, and feed conversion rates during a growout trial conducted in a 3.2‐ha saltwater lake in the Florida Keys, Florida, USA. Approximately 10,500 hatchery‐reared finger‐lings were stocked in two circular, high‐density polyethylene (HDPE) net cages of 7‐m diameter × 7‐m deep (300 m²) and 10‐m diameter × 7‐m deep (600 m³) dimensions. Cages were stocked at 25 fish/m³ (3.2 kg/m³) and 5 fish/m³ (0.72 kg/m³), respectively. Fish grew from a mean of 16.5 g to 302.8 g (25.6 cm TL) in 246 days in the former cage and from a mean of 42.3 g to 245.6 g (23.8 cm TL) in 178 d in the latter cage. Growth rates in weight were best expressed by the following exponential equations: cage 1 (high stocking density): W = 20.716 e^0.0112x (r²= 0.83); cage 2 (low stocking density): W = 38.848 e^0.0118x (r²= 0.81). Length‐weight data indicate that hatcheryraised, cage‐cultured mutton snapper are heavier per unit length than their wild counterparts. There was no significant difference (P < 0.05) between the slopes of the two lines, indicating that fish in the two cages grew at the same rate. The length‐weight relationships for mutton snapper stocked in cages 1 and 2 are expressed, respectively, by the equations W = 0.000009 L ^3.11 (r²= 0.99) and W = 0.000005 L ^3.22 (r²= 0.97). Overall feed conversion rate for both cages combined was 1.4. Approximately 10% of the fish sampled exhibited some degree of deformity, particularly scoliosis. Overall survival rate was 70%. Results suggest that L. analis has potential for aquaculture development in net cage systems.     

Identifying phenological functional types in savanna trees

Savannas are notable for the varied patterns of leaf display in the tree layer. Characterising this variation, and assessing the range of phenological strategies apparent in savanna ecosystems will be helpful for understanding savanna tree life-histories and their response to global change. We recorded leaf phenological metrics on a monthly basis for 28 woody species for one year in a semi-arid savanna at Nylsvley Nature Reserve, South Africa. Using these metrics four plant functional types were described: (1) evergreen species, which retained full canopy throughout the year; (2) semi-evergreen species, which lost a significant amount of canopy during the dry season, but not less than 60%; (3) obligate deciduous species in which the canopy was leafless for about 3 months during the dry season; and (4) rain-stimulated species, in which canopy flushing was driven by rainfall patterns. Of the 28 species, 18% were evergreen, 18% obligate deciduous, 32% semi-evergreen and 32% were rain-stimulated species. These results confirm that phenological strategies are variable in savannas, and highlight that there are numerous cues controlling the timing of leaf out and leaf drop. By defining distinct phenological strategies we can predict which plant functional types will have phenological cues that will be vulnerable to shifting climates.     

Validation of a von Willebrand factor antigen enzyme-linked immunosorbent assay and newly developed collagen-binding assay

No single test is comprehensive enough to detect all of the variants of von Willebrand Disease (VWD), making determination of both concentration and function of von Willebrand Factor (VWF) important for an accurate diagnosis. The objective of the study was to validate a newly developed VWF collagen binding assay (VWF:CB) and VWF antigen enzyme-linked immunosorbent assay (ELISA) developed at the Ontario Veterinary College (OVC VWF:Ag). Linearity, sensitivity, and coefficients of variation were determined. The Asserachrom VWF:Ag ELISA was used as the reference assay for this study. Concordance correlation and Bland-Altman plots were used to evaluate agreement between both VWF:Ag assays. The VWF:CB accuracy was assessed by degree of association with the VWF:Ag assays, and the VWF:Ag to VWF:CB ratio. All assays were assessed for their ability to distinguish between VWD negative and VWD positive patients. Linearity, intra-assay coefficients of variation, and inter-assay coefficients of variation were acceptable for both the newly developed VWF:CB (R² = 0.97, average CV = 4.4, and 15, respectively) and OVC VWF:Ag assays (R² = 0.96, average CV = 7.9, and 5.9, respectively). Agreement between the OVC VWF:Ag assay and reference assay was excellent (ρ_c = 0.89), and although differences between assay results precluded interchangeable use of the assays, both successfully distinguished VWD positive and VWD negative dogs (P < 0.0001). The VWF:CB showed a strong association with both VWF:Ag assays (R² = 0.86, 0.82) and VWF:Ag to VWF:CB ratios (≤ 1) were as expected. The excellent performance of both assays in this validation study confirm their reliability and potential for clinical application.     

Biofilm production by pathogens associated with canine otitis externa,and the antibiofilm activity of ionophores and antimicrobial adjuvants

Otitis externa (OE) is a frequently reported disorder in dogs associated with secondary infections by Staphylococcus, Pseudomonas and yeast pathogens. The presence of biofilms may play an important role in the resistance of otic pathogens to antimicrobial agents. Biofilm production of twenty Staphylococcus pseudintermedius and twenty Pseudomonas aeruginosa canine otic isolates was determined quantitatively using a microtiter plate assay, and each isolate was classified as a strong, moderate, weak or nonbiofilm producer. Minimum biofilm eradication concentration (MBEC) of two ionophores (narasin and monensin) and three adjuvants (N‐acetylcysteine (NAC), Tris‐EDTA and disodium EDTA) were investigated spectrophotometrically (OD_570nm) and quantitatively (CFU/ml) against selected Staphylococcus and Pseudomonas biofilm cultures. Concurrently, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of planktonic cultures were assessed. 16/20 of the S. pseudintermedius clinical isolates were weak biofilm producers. 19/20 P. aeruginosa clinical isolates produced biofilms and were distributed almost equally as weak, moderate and strong biofilm producers. While significant antibiofilm activity was observed, no MBEC was achieved with narasin or monensin. The MBEC for NAC ranged from 5,000–10,000 µg/ml and from 20,000–80,000 µg/ml against S. pseudintermedius and P. aeruginosa, respectively. Tris‐EDTA eradicated P. aeruginosa biofilms at concentrations ranging from 6,000/1,900 to 12,000/3,800 µg/ml. The MBEC was up to 16‐fold and eightfold higher than the MIC/MBC of NAC and Tris‐EDTA, respectively. Disodium EDTA reduced biofilm growth of both strains at concentrations of 470 µg/ml and higher. It can be concluded that biofilm production is common in pathogens associated with canine OE. NAC and Tris‐EDTA are effective antibiofilm agents in vitro that could be considered for the treatment of biofilm‐associated OE in dogs.