Seasonal denitrification in flooded and exposed sediments from the Amazon floodplain at Lago Camaleão

Denitrification processes were measured by the acetylene-blockage technique under changing flood conditions along the aquatic/terrestrial transition zone on the Amazon floodplain at Lago Camaleão, near Manaus, Brazil. In flooded sediments, denitrification was recorded after the amendment with NO ₃ ^– (100 mol liter^–1) throughout the whole study period from August 1992 to February 1993. It ranged from 192.3 to 640.7 mol N m^–2 h^–1 in the 0- to 5-cm sediment layer. Without substrate amendment, denitrification was detected only during low water in November and December 1992, when it occurred at a rate of up to 12.2 mol N m^–2 h^–1 Higher rates of denitrification at an average rate of 73.3 mol N m^–2 h^–1 were measured in sediments from the shallow lake basin that were exposed to air at low water. N₂O evolution was never detected in flooded sediments, but in exposed sediments, it was detected at an average rate of 28.3 mol N m^–2 h^–1 during the low-water period. The results indicate that under natural conditions there is denitrification and hence a loss in nitrogen from the Amazon floodplain to the atmosphere. Rates of denitrification in flooded sediments were one to two orders of magnitude smaller than in temperate regions. However, the nitrogen removal of exposed sediments exceeded that of undisturbed wetland soils of temperate regions, indicating a considerable impact of the flood pulse on the gaseous turnover of nitrogen in the Amazon floodplain.     

Final Disposition and Quality Auditing of the Rehabilitation Process in Wild Raptors Admitted to a Wildlife Rehabilitation Centre in Catalonia,Spain, during a Twelve Year Period (1995–2007)

Background

Variability in reporting and classification methods in previous published data of the final dispositions in the rehabilitation of wild raptors makes use of this data limited in trying to audit the quality of the rehabilitation process. Crude as well as stratified disposition rates are needed if quality auditing of the rehabilitation process is to be adequately performed.

Methodology

Final dispositions of 6221 hospitalized wild raptors admitted at a wildlife rehabilitation centre (WRC) of Catalonia during 1995–2007 were analyzed. These dispositions were calculated as the euthanasia (Er), unassisted mortality (Mr), release (Rr) and captivity rates (Cr)., time to death (Td) for dead and euthanized raptors, and length of stay for released (Tr) raptors was estimated. Stratified analyses by main causes of admission and clinical signs were performed.

Results

The disposition for the total population were: Er  = 30.6%, Mr = 19.1%, Rr  = 47.2%, and Cr  = 3%. By main causes of admission, Er was higher in the trauma category (34.2%), whereas Mr was found similar between trauma (37.4%) and non-trauma categories (34.8%). The highest Rr was observed for the orphaned group (77.9%). Furthermore, Cr was low in all the categories (<4%). By clinical signs, the highest Er was found in animals suffering musculoskeletal (37.9%) or skin (32.3%) lesions; Mr was high in infectious/parasitic diseases (66.7%) and in case of neurological symptoms (64.5%). The euthanized birds had a median Td  = 1 day (P₁₀ = 0-P₉₀ = 59) for both trauma and non-trauma categories, and Td  = 36 days for the orphaned young group (P₁₀ = 0; P₉₀ = 596). The median Td in the unassisted dead birds was 2 days for all the categories (P₁₀ = 0-P₉₀ = 31). Finally, the median Tr in the centre was variable among categories.

Conclusions/Significance

Reporting of final dispositions in wildlife rehabilitation should include the crude and stratified rates (Er, Mr, Rr, and Cr), by causes and clinical presentation, as well as Td and Tr, to allow meaningful auditing of the rehabilitation process quality.     

Seropositivity and risk factors associated with Toxoplasma gondii infection in wild birds from Spain

Toxoplasma gondii is a zoonotic intracellular protozoan parasite of worldwide distribution that infects many species of warm-blooded animals, including birds. To date, there is scant information about the seropositivity of T. gondii and the risk factors associated with T. gondii infection in wild bird populations. In the present study, T. gondii infection was evaluated on sera obtained from 1079 wild birds belonging to 56 species (including Falconiformes (n=610), Strigiformes (n=260), Ciconiiformes (n=156), Gruiformes (n=21), and other orders (n=32), from different areas of Spain. Antibodies to T. gondii (modified agglutination test, MAT titer ≥1:25) were found in 282 (26.1%, IC(95%:)23.5-28.7) of the 1079 birds. This study constitute the first extensive survey in wild birds species in Spain and reports for the first time T. gondii antibodies in the griffon vulture (Gyps fulvus), short-toed snake-eagle (Circaetus gallicus), Bonelli's eagle (Aquila fasciata), golden eagle (Aquila chrysaetos), bearded vulture (Gypaetus barbatus), osprey (Pandion haliaetus), Montagu's harrier (Circus pygargus), Western marsh-harrier (Circus aeruginosus), peregrine falcon (Falco peregrinus), long-eared owl (Asio otus), common scops owl (Otus scops), Eurasian spoonbill (Platalea leucorodia), white stork (Ciconia ciconia), grey heron (Ardea cinerea), common moorhen (Gallinula chloropus); in the International Union for Conservation of Nature (IUCN) "vulnerable" Spanish imperial eagle (Aquila adalberti), lesser kestrel (Falco naumanni) and great bustard (Otis tarda); and in the IUCN "near threatened" red kite (Milvus milvus). The highest seropositivity by species was observed in the Eurasian eagle owl (Bubo bubo) (68.1%, 98 of 144). The main risk factors associated with T. gondii seropositivity in wild birds were age and diet, with the highest exposure in older animals and in carnivorous wild birds. The results showed that T. gondii infection is widespread and can be at a high level in many wild birds in Spain, most likely related to their feeding behaviour.     

Nitrogen dynamics in seasonally flooded soils in the Amazon floodplain

Large areas of the Amazon are subject to seasonal flooding due to water level changes of the river. This flood pulse causes rapidly changing conditions for microorganisms living in the soils which affects the cycling of nitrogen in the ecosystem. An understanding of the nitrogen dynamics in the seasonally flooded soils is essential for the development of productive and sustainable management concepts. We measured nitrogen concentrations, denitrifier enzyme activity (DEA), cell numbers of nitrifying and denitrifying bacteria, respiration, pH and total carbon in the seasonally flooded soils over one entire annual hydrological cycle. By comparing three sites with different vegetation (forest, aquatic macrophyte stand and bare sediment with annual herbs) we assessed the effect of vegetation on soil nitrogen dynamics. Inorganic nitrogen was always dominated by ammonium indicating reduced conditions in the soil even during the terrestrial phase. Although conditions were generally poor for nitrification we observed high numbers of nitrifying bacteria between 10⁴ and 10⁷cells g^–1. Pulses of ammonium as well as high DEA were observed during the transition periods between aquatic and terrestrial phase. Thus the alternation between aquatic and terrestrial phase promotes nitrogen mineralization and denitrification in the soils. There were no plausible correlations between microbial activities and numbers with soil physical or chemical parameters except a relation between the numbers of nitrate reducing bacteria and soil moisture (R² = 0.81) and ammonium (R² = 0.92) at one site. This shows the complex regulation patterns in this habitat. Different vegetation did not alter the general patterns of nitrogen dynamics but the absolute extend of fluctuations. We conclude that both the soil physical and chemical changes directly caused by the flood pulse and the vegetation have a great impact on microbial nitrogen turnover in the soils. The effects of the flood pulse can be buffered by a fine soil texture or a litter layer which prevents desiccation of the soil during the terrestrial phase.     

Detection of apoptosis through the lipid order of the outer plasma membrane leaflet

Cell plasma membranes of living cells maintain their asymmetry, so that the outer leaflet presents a large quantity of sphingomyelin, which is critical for formation of ordered lipid domains. Here, a recently developed probe based on Nile Red (NR12S) was applied to monitor changes in the lipid order specifically at the outer leaflet of cell membranes. Important key features of NR12S are its ratiometric response exclusively to lipid order (liquid ordered vs. liquid disordered phase) and not to surface charge, the possibility of using it at very low concentrations (10-20nM) and the very simple staining protocol. Cholesterol extraction, oxidation and sphingomyelin hydrolysis were found to red shift the emission spectrum of NR12S, indicating a decrease in the lipid order at the outer plasma membrane leaflet. Remarkably, apoptosis induced by three different agents (actinomycin D, camptothecin, staurosporine) produced very similar spectroscopic effects, suggesting that apoptosis also significantly decreases the lipid order at this leaflet. The applicability of NR12S to detect apoptosis was further validated by fluorescence microscopy and flow cytometry, using the ratio between the blue and red parts of its emission band. Thus, for the first time, an environment-sensitive probe, sensitive to lipid order, is shown to detect apoptosis, suggesting a new concept in apoptosis sensing.