Lateral Hyporheic Zone Chemistry in an Artificially Constructed Gravel Bar and a Re‐Meandered Stream Channel,Southern Ontario,Canada1

Abstract: The effect of stream restoration on hyporheic functions has been neglected, although channel rehabilitation projects have a potential to alter stream‐ground‐water interactions. The present study examined the effect of an artificially constructed gravel bar and re‐meandered stream channel on lateral hyporheic exchange flow and chemistry in two lowland N‐rich streams in southern Ontario, Canada. Nitrate concentrations were relatively high, ranging from 0.5 to 1.3 mg N/l in both streams during spring through fall months. However, nitrate concentrations showed a steep decline as stream water entered the gravel bar and the meander bends. Differences between observed and predicted nitrate concentrations based on conservative ion concentration patterns indicated that 40‐100 and 68‐98% of the nitrate entering the hyporheic zone was removed in the gravel bar and meanders, respectively. Rapid depletion of dissolved oxygen concentrations along lateral hyporheic flow paths and denitrifying potentials assayed by the acetylene block technique in hyporheic sediments suggests that denitrification was an important mechanism of nitrate depletion. Despite the high rate of nitrate removal, the flux of stream water laterally entering the constructed gravel bar and meander bends was very small, and hyporheic nitrate removal was <0.015% of the daily stream load during base‐flow periods in summer and fall. The effects of restoration projects on hyporheic zone dynamics are often limited in lowland streams by low channel gradients and fine floodplain sediments with low interstitial flows that restrict the magnitude of the stream‐hyporheic connection.     

Spatial and temporal changes in Louisiana's Barataria Basin marshes, 1945–1980

A computerized geographic information system with site-specific change-detection capabilities was developed to document amounts, rates, locations, and sequences of loss of coastal marsh to open water in Barataria Basin, Louisiana, USA. Land-water interpretations based on 1945, 1956, 1969, and 1980 aerial photographs were used as input, and a modified version of the Earth Resources Laboratory Applications Software developed by the National Aeronautics and Space Administration was used as a spatial data base management system. Analysis of these data sets indicates that rates of marsh loss have increased from 0.36% per year in the 1945–56 period, to 1.03% per year in 1956–69, and to 1.96% per year in 1969–80. The patterns of marsh loss indicate that the combination of processes causing degradation of the marsh surface does not affect all areas uniformly. Marsh loss rates have been highest where freshwater marshes have been subject to saltwater intrusion. The increase in the wetland loss rates corresponds to accelerated rates of subsidence and canal dredging and to a cumulative increase in the area of canals and spoil deposits.     

Interactive effects of water and controlled release urea on nitrogen metabolism,accumulation, translocation,and yield in summer maize

To investigate the interactive effects of water and N from controlled release urea (CRU) on N metabolism, accumulation, translocation, and yield in Zhengdan958 (a summer maize cultivar planted widely in China), three water levels (adequate water W3, mild water stress W2, severe water stress W1) and four amounts of CRU (N) (N0, N1, N2, and N3 were 0, 105, 210, and 315 kg N ha^?1, respectively) were carried out under the waterproof shed and soil column conditions. The results showed that yield, N metabolism, accumulation, and translocation were significantly affected by water, CRU, and their interactions after tasseling. Yields showed an increasing trend in response to N rates from 100.2 to 128.8 g plant^?1 under severe water stress (W1), from 124.7 to 174.6 g plant^?1 under mild water stress (W2), and from 143.7 to 177.0 g plant^?1 under adequate water conditions (W3). There was an associated optimum amount of N for each water level. Under W1 and W2, N3 treatments showed significant advantages in three N metabolism enzymes’ activities and the N accumulations, and yield and its components were highest. But the nitrogen harvest index (NHI) of N3 had no significant difference with other nitrogen treatments. Under W3, the N translocation efficiency (NTE) and N translocation conversion rate (NTCR) of N2 in stem and leaf were higher than those of N3, but the N metabolism enzymes’ activities and yields of N2 and N3 had no significant difference, which indicated that N2 was superior to N3. The N3 treatment under W2 and N2 under W3 increased the N accumulation capacity in maize grain as well as the N translocation to grain that contributed to the increase of 1000-gain weight and grains per ear after tasseling. Under this experimental condition, a CRU rate of 225 kg ha^?1 was the best treatment when the soil moisture content was 75 ± 5% of field capacity, but an N rate of 300 kg ha^?1 was superior when soil moisture content was maintained at 55 ± 5% of field capacity during the entire growing season.     

Fossil proxies of near-shore sea surface temperatures and seasonality from the late Neogene Antarctic shelf

We evaluate the available palaeontological and geochemical proxy data from bivalves, bryozoans, silicoflagellates, diatoms and cetaceans for sea surface temperature (SST) regimes around the nearshore Antarctic coast during the late Neogene. These fossils can be found in a number of shallow marine sedimentary settings from three regions of the Antarctic continent, the northern Antarctic Peninsula, the Prydz Bay region and the western Ross Sea. Many of the proxies suggest maximum spring–summer SSTs that are warmer than present by up to 5 °C, which would result in reduced seasonal sea ice. The evidence suggests that the summers on the Antarctic shelf during the late Neogene experienced most of the warming, while winter SSTs were little changed from present. Feedbacks from changes in summer sea ice cover may have driven much of the late Neogene ocean warming seen in stratigraphic records. Synthesized late Neogene and earliest Quaternary Antarctic shelf proxy data are compared to the multi-model SST estimates of the Pliocene Model Intercomparison Project (PlioMIP) Experiment 2. Despite the fragmentary geographical and temporal context for the SST data, comparisons between the SST warming in each of the three regions represented in the marine palaeontological record of the Antarctic shelf and the PlioMIP climate simulations show a good concordance.     

Detrimental effects of carotenoid pigments: the dark side of bright coloration

Carotenoid pigments produce yellow, orange, and red integumentary color displays that can serve as reliable signals of health and condition. In many birds and fish, individuals gain competitive or mating advantages by ingesting and utilizing large quantities of carotenoid pigments. Carotenoid pigments serve as antioxidants, performing important functions as free-radical scavengers. The beneficial effects of carotenoid pigments are well documented, but rarely have researchers considered potential detrimental effects of high-level accumulation of carotenoids. We maintained American goldfinches (Carduelis tristis) on high- or low-carotenoid diets through molt and tested for damage to the liver and skeletal muscle. High intake of carotenoids had no measurable effect on liver enzymes but caused an increase in creatine kinase, an indicator of skeletal muscle breakdown, and a reduction in vertical flight performance, a measure of skeletal muscle integrity. The detrimental effects of high-level carotenoid accumulation were approximately equivalent to the negative effects of removing carotenoids from the diet. The adverse effects observed in this study have important implications for theories of the function and evolution of colorful plumage.     

Characterization of phenanthrene degradation by strain Polyporus sp. S133

Polyporus sp. S133, a fungus collected from contaminated soil, was used to degrade phenanthrene, a polycyclic aromatic hydrocarbon, in a mineral salt broth liquid culture. A maximal degradation rate (92%) was obtained when Polyporus sp. S133 was cultured for 30 days with agitation at 120 r/min, as compared to 44% degradation in non-agitated cultures. Furthermore, the degradation was a ected by the addition of surfactants. Tween 80 was the most suitable surfactant for the degradation of phenanthrene by Polyporus sp. S133. The degradation rate increased as the amount of Tween 80 added increased. The rate in agitated cultures was about 2 times that in non-agitated cultures. The mechanism of degradation was determined through the identification of metabolites; 9,10-phenanthrenequinone, 2,2’-diphenic acid, phthalic acid, and protocatechuic acid. Several enzymes (manganese peroxidase, lignin peroxidase, laccase, 1,2-dioxygenase and 2,3-dioxygenase) produced by Polyporus sp. S133 were detected during the incubation. The highest level of activity was shown by 1,2-dioxygenase (187.4 U/L) after 20 days of culture.