Effect of time on the natural regeneration of salt marsh

Abstract. The effect of time on natural regeneration of two salt marshes was studied in relation to plant and edaphic factors. The study was carried out in two naturally restoring salt marshes, differing in restoration time, in Txingudi (Bay of Biscay). After 20 yr, the younger salt marsh had the same plant species richness and high species similarity as a 35 yr old salt marsh (17 and 16, respectively, similarity index = 0.9), but both sites had lower species richness and similarity than a nearby natural salt marsh (36 plant species and similarity indices of 0.45 with the 35 yr old marsh and 0.46 with the 20 yr old marsh). Plant species present in the two recovering salt marshes followed a similar distribution pattern in relation to organic matter, conductivity and moisture content although this zonation differed from the natural salt marsh. The range of edaphic factors measured was also similar, but differed from those in the natural salt marsh. The process of plant species recolonization and spatial distribution might be delayed by a low probability of species arrival and by the time need for the restoration of hydrologic and edaphic factors. This study supports the necessity of long‐term monitoring in measuring coastal salt marsh restoration.     

Low temperature acclimation of photosynthetic capacity and leaf morphology in the context of phloem loading type

Carbon export from leaf mesophyll to sugar-transporting phloem occurs via either an apoplastic (across the cell membrane) or symplastic (through plasmodesmatal cell wall openings) pathway. Herbaceous apoplastic loaders generally exhibit an up-regulation of photosynthetic capacity in response to growth at lower temperature. However, acclimation of photosynthesis to temperature by symplastically loading species, whose geographic distribution is particularly strong in tropical and subtropical areas, has not been characterized. Photosynthetic and leaf anatomical acclimation to lower temperature was explored in two symplastic (Verbascum phoeniceum, Cucurbita pepo) and two apoplastic (Helianthus annuus, Spinacia oleracea) loaders, representing summer- and winter-active life histories for each loading type. Regardless of phloem loading type, the two summer-active species, C. pepo and H. annuus, exhibited neither foliar anatomical nor photosynthetic acclimation when grown under low temperature compared to moderate temperature. In contrast, and again irrespective of phloem loading type, the two winter-active mesophytes, V. phoeniceum and S. oleracea, exhibited both a greater number of palisade cell layers (and thus thicker leaves) and significantly higher maximal capacities of photosynthetic electron transport, as well as, in the case of V. phoeniceum, a greater foliar vein density in response to cool temperatures compared to growth at moderate temperature. It is therefore noteworthy that symplastic phloem loading per se does not prevent acclimation of intrinsic photosynthetic capacity to cooler growth temperatures. Given the vagaries of weather and climate, understanding the basis of plant acclimation to, and tolerance of, low temperature is critical to maintaining and increasing plant productivity for food, fuel, and fiber to meet the growing demands of a burgeoning human population.     

Hepatic 3 alpha-dehydrogenation and 7 alpha-hydroxylation of deoxycholic acid in the guinea-pig

The metabolic fate of exogenous deoxycholate administered either intraperitoneally or intragastrically to male Hartley guinea-pigs was investigated. Two animals received a constant infusion of [24-14C]deoxycholate through an intraperitoneal catheter for 2 hr. Bile was quantitatively collected in 30 min samples during infusion and for 2 additional hours. Each bile sample was analyzed for composition and radioactivity. Five animals received for 15 days, through an intragastric catheter, 35 mg/kg/day of deoxycholate. The biliary bile acid composition was compared with that of a sham-operated control group. The studies with both animal models indicated that guinea-pigs, as the only species so far known, extensively oxidize deoxycholate to form 3-oxo,12 alpha-hydroxy-cholanic acid, which is secreted in bile mostly conjugated with glycine. In addition a small fraction (approx. 7%) of the administered deoxycholate is 7 alpha hydroxylated to form cholic acid. The metabolites being more hydrophilic than administered deoxycholate, it is suggested that guinea-pig liver counteracts the adverse increase in bile acids detergency, which follows deoxycholate administration, by converting most of the latter into less detergent compounds.     

Environmental Factors Influencing the Prevalence of a Clostridium botulinum Type C/D Mosaic Strain in Nonpermanent Mediterranean Wetlands

Between 1978 and 2008, 13 avian botulism outbreaks were recorded in the wetlands of Mancha Húmeda (central Spain). These outbreaks caused the deaths of around 20,000 birds from over 50 species, including globally endangered white-headed ducks (Oxyura leucoceophala). Here, a significant association was found between the number of dead birds recorded in each botulism outbreak and the mean temperature in July (always >26°C). The presence of Clostridium botulinum type C/D in wetland sediments was detected by real-time PCR (quantitative PCR [qPCR]) in 5.8% of 207 samples collected between 2005 and 2008. Low concentrations of Cl⁻ and high organic matter content in sediments were significantly associated with the presence of C. botulinum. Seventy-five digestive tracts of birds found dead during botulism outbreaks were analyzed; C. botulinum was present in 38.7% of them. The prevalence of C. botulinum was 18.2% (n = 22 pools) in aquatic invertebrates (Chironomidae and Corixidae families) and 33.3% (n = 18 pools) in necrophagous invertebrates (Sarcophagidae and Calliphoridae families), including two pools of adult necrophagous flies collected around bird carcasses. The presence of the bacteria in the adult fly form opens up new perspectives in the epidemiology of avian botulism, since these flies may be transporting C. botulinum from one carcass to another.     

Eutrophication and Bacterial Pathogens as Risk Factors for Avian Botulism Outbreaks in Wetlands Receiving Effluents from Urban Wastewater Treatment Plants

Due to the scarcity of water resources in the “Mancha Húmeda” Biosphere Reserve, the use of treated wastewater has been proposed as a solution for the conservation of natural threatened floodplain wetlands. In addition, wastewater treatment plants of many villages pour their effluent into nearby natural lakes. We hypothesized that certain avian pathogens present in wastewater may cause avian mortalities which would trigger avian botulism outbreaks. With the aim of testing our hypothesis, 24 locations distributed in three wetlands, two that receive wastewater effluents and one serving as a control, were monitored during a year. Sediment, water, water bird feces, and invertebrates were collected for the detection of putative avian pathogenic Escherichia coli (APEC), Salmonella spp., Clostridium perfringens type A, and Clostridium botulinum type C/D. Also, water and sediment physicochemical properties were determined. Overall, APEC, C. perfringens, and C. botulinum were significantly more prevalent in samples belonging to the wetlands which receive wastewater. The occurrence of a botulism outbreak in one of the studied wetlands coincided with high water temperatures and sediment 5-day biochemical oxygen demand (BOD₅), a decrease in water redox potential, chlorophyll a, and sulfate levels, and an increase in water inorganic carbon levels. The presence of C. botulinum in bird feces before the onset of the outbreak indicates that carrier birds exist and highlights the risk of botulinum toxin production in their carcasses if they die by other causes such as bacterial diseases, which are more probable in wastewater wetlands.     

Mpl Traffics to the Cell Surface Through Conventional and Unconventional Routes

Myeloproliferative neoplasms (MPNs) are often characterized by JAK2 or calreticulin (CALR) mutations, indicating aberrant trafficking in pathogenesis. This study focuses on Mpl trafficking and Jak2 association using two model systems: human erythroleukemia cells (HEL; JAK2V617F) and K562 myeloid leukemia cells (JAK2WT). Consistent with a putative chaperone role for Jak2, Mpl and Jak2 associate on both intracellular and plasma membranes (shown by proximity ligation assay) and siRNA‐mediated knockdown of Jak2 led to Mpl trapping in the endoplasmic reticulum (ER). Even in Jak2 sufficient cells, Mpl accumulates in punctate structures that partially colocalize with ER‐tracker, the ER exit site marker (ERES) Sec31a, the autophagy marker LC3 and LAMP1. Mpl was fused to miniSOG, a genetically encoded tag for correlated light and electron microscopy. Results suggest that a fraction of Mpl is taken up into autophagic structures from the ER and routed to autolyososomes. Surface biotinylation shows that both immature and mature Mpl reach the cell surface; in K562 cells Mpl is also released in exosomes. Both forms rapidly internalize upon ligand addition, while recovery is primarily attributed to immature Mpl. Mpl appears to reach the plasma membrane via both conventional ER‐Golgi and autolysosome secretory pathways, as well as recycling.      

H2O2 localization in the green alga Micrasterias after salt and osmotic stress by TEM-coupled electron energy loss spectroscopy

Reactive oxygen species (ROS), including hydrogen peroxide (H₂O₂), are constantly generated as by-products of normal metabolic cellular pathways and can be overproduced in response to stress. In this study, we investigated ROS production and localization of H₂O₂ after salt (200 mM KCl) and osmotic (iso-osmotic sorbitol concentration) stress in the unicellular green alga Micrasterias. By means of the dye H₂DCFDA and confocal laser scanning microscopy, most ROS production could be detected in KCl-treated cells when compared to sorbitol-exposed cells and controls. For ultrastructural detection of H₂O₂, CeCl₃, which reacts with H₂O₂ and produces cerium perhydroxide deposits, has been used. Cerium was identified by transmission electron microscopy (TEM)-coupled electron energy loss spectroscopy (EELS) in organelles of KCl- and sorbitol-treated cells and in controls. Statistical measurements of the presence of the cerium M_4,5 edge were performed in mitochondria, chloroplasts, cell walls, and cytoplasmic sites of five individual cells after each treatment. The most pronounced increase in H₂O₂ production was found in chloroplasts of KCl- and sorbitol-treated cells. This shows that the chloroplast reveals the strongest response in H₂O₂ production after stress induction in Micrasterias. Significant elevation of H₂O₂ production also occurred in mitochondria and cytoplasm, whereas H₂O₂ levels remained unchanged or even slightly decreased in cell walls of treated cells. Additionally, TEM micrographs and EELS analyses provided indirect evidence for an increased H₂O₂ production at the plasma membrane of KCl-treated cells, indicating an involvement of the plasma membrane NADPH oxidase in H₂O₂ generation.     

Suitability of the antioxidative system as marker of magnesium deficiencyin <Emphasis Type="Italic">Capsicum annuum</Emphasis> L. plants under controlled conditions

To explore the viability of using enzyme activities and their substrates as an alternative tool for the determination of mineral (i.e., Mg) critical values, a detailed characterization of the response of the antioxidative system of Capsicum annuum L. leaves under Mg deficiency was carried out. The response of each selected enzyme activity and substrate [i.e., superoxide dismutase (SOD), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR); ascorbate and glutathione pool; protein and chlorophyll concentration] was subjected to mathematical modelling in order to calculate Mg critical values (x_c). Our x_c values ranged from 0.70 to 0.14%, on a dry weight (DW) basis, for GR activity and total glutathione concentration, respectively. Our results suggest that, under Mg deficiency, cells enhance their antioxidative defence system by initially increasing their SOD and GR activities. Subsequently, higher GSH/GSSG ratios were observed, probably due to a greater increase in GR activity (x_c = 0.70% DW) than in total glutathione concentration (x_c = 0.14% DW). In contrast, x_c values for total ascorbate concentrations (x_c = 0.29% DW) were higher than those for DHAR activities (x_c = 0.19% DW). In an attempt to study the limitations regarding the utilization of these enzymes and substrates as markers of Mg critical values in pepper, the x_c values here obtained were compared to those based on growth parameters that have been reported in the literature. Overall, the results indicate that some enzymes and substrates, such as total ascorbate concentration, 1/protein ratio, and DHAR activity, might be suitable markers for the determination of Mg critical values in pepper plants under controlled conditions.     

Buffering capacity through cation leaching of Pinus radiata D. Don canopy

The change in the composition of atmospheric deposition as it passes through the forest canopy on two 10-year-old Pinus radiata D. Don forests (Manzanal and Posadero) was studied in the Basque Country, analysing the concentration of different constituents in bulk precipitation and throughfall. The precipitation at the study sites was bimodal with two maxima in the year; one in late spring and another one in late autumn. Posadero had a mean annual precipitation of 1223.6 mm with an interception loss of 27.5% by the forest canopy and Manzanal had a mean annual precipitation of 978.6 mm with the interception loss being 22.2% of it. Constituent concentrations followed a similar seasonal variation, increasing during the summer when precipitation decreases. At both study sites the chemical species analysed in bulk precipitation and throughfall were characterised by the fact that they came from three distinct sources: acidic pollution, marine and terrestrial origin. Concentration of constituents in bulk precipitation in Manzanal was higher than in Posadero, most probably due to the smaller amount of precipitation that falls in this study site. The precipitation at Manzanal had a significantly lower pH than at Posadero. The amounts of sulphate, nitrate-nitrogen, organic nitrogen and protons that fell in the bulk precipitation at Manzanal (the polluted site) were higher than those that fell at Posadero (less polluted site). The concentration of organic nitrogen in the bulk precipitation of the polluted site was significantly related to the hydrocarbon concentration measured in the atmosphere in the nearby town of Muskiz. Throughfall in Manzanal had higher amounts of sulphate, nitrate-nitrogen, calcium, magnesium, sodium, potassium and chloride than in Posadero. This fact suggests that both dry deposition and canopy leaching were an important source of throughfall constituents in Manzanal. The amount of manganese measured in Posadero throughfall was higher than that found in Manzanal throughfall. The pH in the throughfall did not show any significant difference between sites and was significantly higher than in bulk precipitation. Thus, canopies in the study sites seem to be able to neutralise very efficiently the acidic load of bulk deposition. Despite this buffering capacity of the canopies, the soil at Manzanal appeared to be more acidic than at Posadero, probably due to the liberation of protons in the rhizosphere when the neutralising pacity of the canopy is `recharged'. This soil acidification may be leading to a greater solubilization of aluminium in the polluted site which could suffer from cation nutrient deficiencies in the future.