Effects of Watershed Land use on Nitrogen Concentrations and δ 15 Nitrogen in Groundwater

Eutrophication is a major agent of change affecting freshwater, estuarine, and marine systems. It is largely driven by transportation of nitrogen from natural and anthropogenic sources. Research is needed to quantify this nitrogen delivery and to link the delivery to specific land-derived sources. In this study we measured nitrogen concentrations and δ¹⁵N values in seepage water entering three freshwater ponds and six estuaries on Cape Cod, Massachusetts and assessed how they varied with different types of land use. Nitrate concentrations and δ¹⁵N values in groundwater reflected land use in developed and pristine watersheds. In particular, watersheds with larger populations delivered larger nitrate loads with higher δ¹⁵N values to receiving waters. The enriched δ¹⁵N values confirmed nitrogen loading model results identifying wastewater contributions from septic tanks as the major N source. Furthermore, it was apparent that N coastal sources had a relatively larger impact on the N loads and isotopic signatures than did inland N sources further upstream in the watersheds. This finding suggests that management priorities could focus on coastal sources as a first course of action. This would require management constraints on a much smaller population.     

Land–Ocean Coupling of Carbon and Nitrogen Fluxes on Sandy Beaches

Rivers link oceans with the land, creating global hot spots of carbon processing in coastal seas. Coastlines around the world are dominated by sandy beaches, but beaches are unusual in that they are thought to rely almost exclusively on marine imports for food. No significant connections to terrestrial production having been demonstrated. By contrast, we isotopically traced carbon and nitrogen pathways leading to clams (Donax deltoides) on beaches. Clams from areas influenced by river plumes had significantly different isotope signatures (δ¹³C: −18.5 to −20.2‰; δ¹⁵N: 8.3–10.0‰) compared with clams remote from plumes (δ¹³C: −17.5 to −19.5‰; δ¹⁵N: 7.6–8.7‰), showing that terrestrial carbon and sewage, both delivered in river plumes, penetrate beach food webs. This is a novel mechanism of trophic subsidy in marine intertidal systems, linking the world’s largest shore ecosystem to continental watersheds. The same clams also carry pollution signatures of sewage discharged into rivers, demonstrating that coastal rivers connect ecosystems in unexpected ways and transfer contaminants across the land–ocean boundary. The links we demonstrate between terrigenous matter and the largest of all marine intertidal ecosystems are significant given the immense social, cultural, and economic values of beaches to humans and the predicted consequences of altered river discharge to coastal seas caused by global climate change.     

Characteristics of Electron Drift in an Ar–Hg Mixture

The characteristics of electron drift in a mixture of argon with mercury vapor at reduced electric fields of E/N = 1–100 Td are calculated and analyzed with allowance for inelastic collisions. It is shown that even a minor additive of mercury to argon at a level of a fraction of percent substantially affects the discharge parameters, in particular, the characteristics of inelastic processes. The influence of the concentration of mercury vapor in argon on the kinetic characteristics, such as the diffusion and mobility coefficients and ionization frequency, is investigated.     

Spatial Dependency of Vegetation–Environment Linkages in an Anthropogenically Influenced Wetland Ecosystem

Management and restoration of vegetation patterns in ecosystems depends on an understanding of allogenic environmental factors that organize species assemblages and autogenic processes linked to assemblages. However, our ability to make strong inferences about vegetation–environment linkages in field studies is often limited due to correlations among environmental variables, spatial autocorrelation, and scale dependency of observations. This is particularly true in large, heterogeneous ecosystems such as the Everglades. Here, an extensive canal-and-levee system has modified historical fire regimes and hydropatterns while contributing large inputs of surface-water phosphorus (P), nitrogen (N) and cations such as sodium (Na). Some of these anthropogenic influences have been implicated as factors leading to the shift of sawgrass (Cladium jamaicense Crantz) and slough communities to an assemblage of weedy species such as cattail (Typha domingensis Pers.). To untangle the independent effect of multiple variables, we used a spatially explicit, multivariate approach to identify linkages among spatial patterns, environmental factors, and vegetation composition along a 10-km gradient of anthropogenic influence in the Everglades, an area immediately downstream from canal inflow structures. Clusters of plots were stratified among three zones (Impacted, Transition, and Reference), a design that allowed us to contrast vegetation–environment linkages and spatial patterns at multiple scales and degrees of ecosystem alteration. Along the 10-km gradient, partial Mantel tests showed that nutrients (phosphorus, nitrogen, and potassium) and hydropattern (frequency of dryness) were independently linked to patterns in fine-scale vegetation composition, but phosphorus was the only environmental variable linked to patterns of coarse-scale composition. Regardless of scale, the effect of distance from canal inflows accounted for variation in vegetation that could not be explained by other variables. A significant residual effect of spatial proximity among sampling locations also was detected and was highly suggestive of dispersal or other spatial determinants of vegetation pattern. However, this pure spatial effect was significantly stronger in the Transition and Impacted zones than in the Reference zone—fine-scale environmental variables explained all of the spatial structure in vegetation in the Reference zone. A further examination of spatial patterns in vegetation by using Mantel correlograms revealed significant heterogeneity at fine, local scales in the Reference zone, but this pattern progressively degraded toward homogeneity among closely neighboring locations in the Impacted zone. However, the fine-scale vegetation pattern in the Reference zone was hierarchically nested at a broader scale and yielded a similar coarse pattern across the landscape, whereas the coarse pattern in the Transition and Impacted zones was relatively heterogeneous and fragmented. Collectively, these results indicate that allogenic spatial and environmental factors related to the canal system have disrupted the coupling between pattern and process by altering fine-scale vegetation–environment linkages and spatial patterns characteristic of the natural Everglades ecosystem.     

Land use–related Changes in Aboveground Carbon Stocks of Austria’s Terrestrial Ecosystems

Land-use changes considerably alter the patterns and processes of terrestrial ecosystems. In an attempt to assess the impact of the human domination of ecosystems, this study quantifies the effect of human activities on aboveground carbon stocks in vegetation, based on a comparison of potential and actual vegetation in Austria. Following an accounting approach, statistical and GIS data on vegetation, elevation, land use, biomass harvest, as well as forest inventories and real estate statistics, were entered into the assessment, which was performed at the level of municipalities (n = 2,350). The results show that aboveground carbon storage in Austria has been considerably reduced by human activities. Actual vegetation contains 64% less carbon than would be expected in potential vegetation. The conversion of forests to cropland, grasslands, and urban areas has contributed 77% to this reduction in carbon stocks, the remaining 23% is due to forest management. In Austria, aboveground carbon stocks in forests have been reduced by 30% due to reductions in stand age and changes in forest species composition. Placing the data in a historical context, this analysis suggests that the current terrestrial carbon sink is a reversal of past carbon losses.     

Influence of Oil Type on Characteristics of β-Sitosterol and Stearic Acid Based Oleogel

Oleogels were prepared from extra virgin olive oil, corn oil, sunflower oil, and flaxseed oil with a mixture of β-sitosterol and stearic acid (Sit1:SA4, w/w) at concentrations of 15 and 20 g/100 g oil. The prepared oleogels were characterized by different methods to study the influence of oil type on the oleogel properties. The oil type influenced the colour and appearance of the oleogel. The flaxseed oil based oleogel showed lower oil loss and higher firmness than those of other oils based oleogels. The increase of gelator mixture from 15 to 20 g/100 g oil reduced the oil loss and improved the firmness of oleogel samples. The microscopy and small-angle x-ray scattering analyses showed different microstructures and crystallographic reflections for oleogels prepared from different oil types. Also, the oil type and concentration of gelator mixture influenced the melting and crystallization enthalpies of oleogel. Furthermore, different oils based oleogels showed varying values of viscosity, storage modulus (G’), and loss modulus (G”). Therefore, it can be concluded that the oil type and concentration of gelator influence the functional properties of oleogel and the flaxseed oil resulted in oleogel with good properties compared with other oils used in the study.     

Influence of edge on predator–prey distribution and abundance

I investigated the effect of spatial configuration on distribution and abundance of invertebrate trophic groups by counting soil arthropods under boxes (21 × 9.5 cm) arranged in six different patterns that varied in the amount of edge (137–305 cm). I predicted fewer individuals from the consumer trophic group (Collembola) in box groups with greater amount of edge. This prediction was based on the assumption that predators (mites, ants, spiders, centipedes) select edge during foraging and thereby reduce abundance of the less mobile consumer group under box patterns with greater edge. Consumer abundance (Collembola) was not correlated with amount of edge. Among the predator groups, mite, ant and centipede abundance related to the amount of edge of box groups. However, in contrast to predictions, abundance of these predators was negatively correlated with amount of edge in box patterns. All Collembola predators, with the exception of ants, were less clumped in distribution than Collembola. The results are inconsistent with the view that predators used box edges to predate the less mobile consumer trophic group. Alternative explanations for the spatial patterns other than predator–prey relations include (1) a negative relationship between edge and moisture, (2) a positive relationship between edge and detritus decomposition (i.e. mycelium as food for the consumer group), and (3) a negative relationship between edge and the interstices between adjacent boxes. Landscape patterns likely affect microclimate, food, and predator–prey relations and, therefore, future experimental designs need to control these factors individually to distinguish among alternative hypotheses.     

Influence of Process and Formulation Parameters on Dissolution and Stability Characteristics of Kollidon? VA 64 Hot-Melt Extrudates

The objective of the present study was to investigate the effects of processing variables and formulation factors on the characteristics of hot-melt extrudates containing a copolymer (Kollidon® VA 64). Nifedipine was used as a model drug in all of the extrudates. Differential scanning calorimetry (DSC) was utilized on the physical mixtures and melts of varying drug–polymer concentrations to study their miscibility. The drug–polymer binary mixtures were studied for powder flow, drug release, and physical and chemical stabilities. The effects of moisture absorption on the content uniformity of the extrudates were also studied. Processing the materials at lower barrel temperatures (115–135°C) and higher screw speeds (50–100 rpm) exhibited higher post-processing drug content (~99–100%). DSC and X-ray diffraction studies confirmed that melt extrusion of drug–polymer mixtures led to the formation of solid dispersions. Interestingly, the extrusion process also enhanced the powder flow characteristics, which occurred irrespective of the drug load (up to 40% w/w). Moreover, the content uniformity of the extrudates, unlike the physical mixtures, was not sensitive to the amount of moisture absorbed. The extrusion conditions did not influence drug release from the extrudates; however, release was greatly affected by the drug loading. Additionally, the drug release from the physical mixture of nifedipine–Kollidon® VA 64 was significantly different when compared to the corresponding extrudates (f₂ = 36.70). The extrudates exhibited both physical and chemical stabilities throughout the period of study. Overall, hot-melt extrusion technology in combination with Kollidon® VA 64 produced extrudates capable of higher drug loading, with enhanced flow characteristics, and excellent stability.KEY WORDS: extrusion, Kollidon® VA 64, moisture absorption, nifedipine, solid dispersion     

Dynamics of Inorganic Nitrogen in Nitrate and Glucose-amended Alkaline–saline Soil

Induction of assimilatory NO ₃ ⁻ reduction through the application of an easily decomposable substrate in alkaline–saline soils of the former lake Texcoco (Mexico) resulted in a fast immobilization of NO ₃ ⁻ in excess of N required for metabolic activity and the release of large concentrations of NO ₂ ⁻ and smaller amounts of NH ₄ ⁺ . We postulated that this was regulated by the amounts of NO ₃ ⁻ and glucose added, and affected by the specific characteristics of soil from the former lake Texcoco. This was investigated by spiking soils of different electrolytic conductivity (EC) 56.0 dS m⁻¹ (soil A of Texcoco) and 11.6 dS m⁻¹ (soil B of Texcoco) with different concentrations of NO ₃ ⁻ and glucose while dynamics of CO₂, NH ₄ ⁺ , NO ₂ ⁻ and NO ₃ ⁻ were monitored in an aerobic incubation for 7 days. For comparison reasons (control) an agricultural soil with low EC (0.3 dS m⁻¹) was included as well. In the agricultural soil, 67% of the added glucose mineralized within 7 days, but only 15% in soil A of Texcoco and 20% in soil B of Texcoco. The application of NO ₃ ⁻ to the agricultural soil added with glucose increased cumulative production of CO₂ 1.2 times, 1.5 times in soil A of Texcoco and 1.8 times in soil B of Texcoco. Concentration of NO ₂ ⁻ increased to > 100 mg NO ₂ ⁻ -N kg⁻¹ when 1000 mg glucose-C kg⁻¹ and 500 mg NO ₃ ⁻ -N kg⁻¹ were added to soil A and B of Texcoco, but remained < 3 mg NO ₂ ⁻ -N kg⁻¹ in the agricultural soil. The ratio between the cumulative production of CO₂ and the decrease in concentration of NO ₃ ⁻ was approximately one in soil A and B of Texcoco, but 10 in the agricultural soil after 3 days. It was found that micro-organisms in the alkaline–saline soil of the former lake Texcoco were capable of immobilizing large quantities of NO ₃ ⁻ when an easy decomposable substrate was available in excess of what might be required for metabolic activity while producing large concentrations of NO ₂ ⁻ , but these phenomena were absent in an agricultural soil. In soil of Texcoco, concentrations of NO ₂ ⁻ and NH ₄ ⁺ increased with increased salinity and availability of NO ₃ ⁻ . This ability to remove large quantities of NO ₃ ⁻ under these conditions and then utilize it at a later time might benefit micro-organisms of the N limited alkaline–saline soils of Texcoco.     

Influence of multiple action–outcome associations on the transition dynamics toward an optimal choice in rats

When faced with familiar versus novel options, animals may exploit the acquired action–outcome associations or attempt to form new associations. Little is known about which factors determine the strategy of choice behavior in partially comprehended environments. Here we examine the influence of multiple action–outcome associations on choice behavior in the context of rewarding outcomes (food) and aversive outcomes (electric foot-shock). We used a nose-poke paradigm with rats, incorporating a dilemma between a familiar option and a novel, higher-value option. In Experiment 1, two groups of rats were trained with different outcome schedules: either a single action–outcome association (“Reward-Only”) or dual action–outcome associations (“Reward-Shock”; with the added opportunity to avoid an electric foot-shock). In Experiment 2, we employed the same paradigm with two groups of rats performing the task under dual action–outcome associations, with different levels of threat (a low- or high-amplitude electric foot-shock). The choice behavior was clearly influenced by the action–outcome associations, with more efficient transition dynamics to the optimal choice with dual rather than single action–outcome associations. The level of threat did not affect the transition dynamics. Taken together, the data suggested that the strategy of choice behavior was modulated by the information complexity of the environment.     

The Vulture in the Sky and the Hominin on the Land: Three Million Years of Human–Vulture Interaction

ABSTRACT

Vultures and humans have been sympatric for millions of years and evidence from the archaeological and historical records suggests interdependence over long periods. Like other species, early hominins probably used these birds to locate carcasses in the landscape. With the evolution of large-bodied and more encephalized hominins, the quest for high-quality food would have intensified. Vultures used as beacons for meat may have been particularly important to hominins dispersing out of Africa, facilitating the occupation of new landscapes. Neanderthals and prehistoric modern humans incorporated vulture parts into their culture, and while the symbolic and ritualistic significance of the birds may have varied through time and across cultures, their link with positive life forces is apparent. More recently, the intensification of farming and modern sanitary restrictions, as well as the spread of human populations, has led to the radical decline in vulture populations throughout the world. Without commitments by governments to fund vulture conservation programs, the ability to preserve many species may be limited over the long term. In this review paper we discuss the ability of vultures to act as beacons signaling meat in the landscape and our changing relationships with these enigmatic birds through a shared history. Within this narrative, we outline why vultures are fundamental to maintaining our ecosystem and should therefore be protected.     

The Effect of Experimental Hyperthyroidism on Characteristics of Actin–Myosin Interaction in Fast and Slow Skeletal Muscles

The molecular mechanism of the failure of contractile function of skeletal muscles caused by oxidative damage to myosin in hyperthyroidism is not fully understood. Using an in vitro motility assay, we studied the effect of myosin damage caused by oxidative stress in experimental hyperthyroidism on the actin–myosin interaction and its regulation by calcium. We found that hyperthyroidism-induced oxidation of myosin is accompanied by a decrease in the sliding velocity of the regulated thin filaments in the in vitro motility assay, and this effect is increased with the duration of the pathological process.     

Influence of Nematodes on Resource Utilization by Bacteria—an in vitro Study

The positive influence of bacterial feeding nematodes on bacterial mediated processes such as organic matter mineralization and nutrient cycling is widely accepted, but the mechanisms of these interactions are not always apparent. Both transport of bacteria by nematodes, and nutritional effects caused by nematode N excretion are thought to be involved, but their relative importance is not known because of the difficulties in studying these interactions in soil. We developed a simple in vitro assay to study complex nematode/bacterial interactions and used it to conduct a series of experiments to determine the potential influence of nematode movement and nutritional effects on bacterial resource use. The system used bacterial feeding and nonfeeding insect parasitic nematodes, and luminescent bacteria marked with metabolic reporter genes. Both nutritional enhancement of bacterial activity and bacterial transport were observed and we hypothesize that in nature, the relative importance of transport is likely to be greater in bulk soil, whereas nematode excretion may have greater impact in the rhizosphere. In both cases, the ability of nematodes to enhance bacterial resource utilization has implications for soil components of biogeochemical cycling.     

Influence of Guar Gum on the In Vitro Starch Digestibility—Rheological and Microstructural Characteristics

The present study investigates the effect of guar gum on the digestibility of a waxy maize starch in vitro under simulated gastric and intestinal conditions. A detailed rheology and confocal scanning laser microscopy of the digesta were performed in order to study the possible mechanisms of interactions involved during in vitro hydrolysis of starch. No starch hydrolysis was observed under simulated gastric conditions, whereas more than 90% hydrolysis was observed at the end of digestion under simulated intestinal conditions. In the presence of guar gum, the starch hydrolysis was reduced by nearly 25% during the first 10 min and by 15% at the end of in vitro intestinal digestion. The rheological behavior of the digesta was significantly affected in the presence of the gum. The viscosity of digesta decreased during intestinal digestion; however, the extent of decrease was quite low in the presence of guar gum. The consistency index increased and flow behavior index of digesta decreased in the presence of gum after 1 min of intestinal digestion. All the samples (digested or undigested) displayed a pseudoplastic behavior as their apparent viscosity (η _a) decreased with an increase in shear rate. A negative correlation between the starch hydrolysis (%) and storage modulus for the starch sample without gum and a positive correlation for the starch sample with gum were found. Large granule remnants observed through confocal micrographs have shown that the solubilization of starch granule remnants during in vitro digestion is significantly reduced in the presence of gum.     

Influence of water-level fluctuation duration and magnitude on sediment–water nutrient exchange in coastal wetlands

This study examined the influence of water-level fluctuation (WLF) on sediment–water nutrient exchange in the Laurentian Great Lakes. Water levels in the Laurentian Great Lakes have been below the long-term mean for the past 15 years, causing the exposure of sediments that previously have been either continuously inundated or periodically exposed. The magnitude, duration, and frequency of WLF, as well as land-use history, each can influence the amount and type of sediment–water nutrient exchange. We collected sediment cores from relatively pristine coastal wetlands located on Beaver and Garden Islands in northern Lake Michigan. Sediment cores were taken from different water depths to simulate WLF magnitude; desiccation time was experimentally manipulated to simulate WLF duration. At these relatively pristine wetlands, desiccation time and water depth significantly influenced flux. However, nutrient exchange did not behave in a consistent fashion; phosphorus, nitrate, ammonium, and sulfate flux varied based on sediment exposure history and desiccation time. Sediment–water nutrient exchange rates also were compared to prior measurements taken from more impacted coastal wetlands in southern Lake Michigan and Saginaw Bay in Lake Huron. This comparison revealed a stronger influence of anthropogenic stress than desiccation time, with impacted wetland sediments releasing more soluble reactive phosphorus, sulfate, and ammonium, and retaining more nitrate, than pristine wetlands. Our results indicate that WLFs have the potential to influence sediment–water nutrient exchange, which may influence system productivity, but environmental context can override this influence.     

Influence of co-inoculation of bacteria-cyanobacteria on crop yield and C–N sequestration in soil under rice crop

The performance of three selected bacterial strains—PR3, PR7 and PR10 (Providencia sp., Brevundimonas sp., Ochrobacterium sp.) and three cyanobacterial strains CR1, CR2 and CR3 (Anabaena sp., Calothrix sp., Anabaena sp.), and their combinations was evaluated in a pot experiment with rice variety Pusa-1460, comprising 51 treatments along with recommended fertilizer controls. Highest yield enhancement of 19.02% was recorded in T12 (CR2), over control, while significant enhancement in nitrogen fixing potential was recorded in treatments involving combination of bacterial-cyanobacterial strains—T37 (PR3 + CR1 + CR3) and T21 (PR7 + CR1). Organic carbon was significantly increased in all microbe-inoculated treatments, which could be correlated with microbial biomass carbon values and activities of all the enzymes tested in our study. Also, panicle weight and plant biomass were highly correlated with soil microbial carbon. Comparative evaluation revealed the superior performance of strains CR2, CR1 (both Anabaena sp.) and PR10 (Ochrobacterium sp.) in increasing the growth and grain yield of rice and improving soil health, besides N (nitrogen) savings of 40–80 kg ha⁻¹. The study for the first time illustrated the positive effects of co-inoculation of bacterial and cyanobacterial strains for integrated nutrient management of rice crop.     

The Influence of Changes in Magnetic Variations and Light–Dark Cycle on Life-History Traits of Daphnia magna

Day–night cycle is the main zeitgeber (time giver) for biological circadian rhythms. Recently, it was suggested that natural diurnal geomagnetic variation may also be utilized by organisms for the synchronization of these rhythms. In this study, life-history traits in Daphnia magna were evaluated after short-term and multigenerational exposure to 16 h day/8 h night cycle, 32 h day/16 h night cycle, diurnal geomagnetic variation of 24 h, simulated magnetic variation of 48 h, and combinations of these conditions. With short-term exposure, the lighting mode substantially influenced the brood to brood period and the lifespan in daphnids. The brood to brood period, brood size, and body length of crustaceans similarly depended on the lighting mode during the multigenerational exposure. At the same time, an interaction of lighting mode and magnetic variations affected to a lesser extent brood to brood period, brood size, and newborn's body length. The influence of simulated diurnal variation on life-history traits in daphnids appeared distinctly as effects of synchronization between periods of lighting mode and magnetic variations during the multigenerational exposure. Newborn's body length significantly depended on the lighting regime when the periods of both studied zeitgebers were unsynchronized, or on the interaction of light regime with magnetic variations when the periods were synchronized. These results confirm the hypothesis that diurnal geomagnetic variation is an additional zeitgeber for biological circadian rhythms. Possible mechanisms for these observed effects are discussed. Bioelectromagnetics. © 2020 Bioelectromagnetics Society     

Effects of Mineral Nitrogen Partitioning on Tree–Grass Coexistence in West African Savannas

Ecosystems - Coexistence between trees and grasses in savannas is generally assumed to be due to a combination of partial niche separation for water acquisition and disturbances impacting the...     

Abundance and feeding of wintering and migrating aquatic birds in two sampling areas of Lake Balaton in 1983–1985

The investigation was carried out at two sampling areas in Lake Balaton (surface area 600 km²), of which one was hypertrophic and the other was mesotrophic. Species diversity was higher in the hypertrophic area, primarily due to a higher number of Anatid species. Contents of crops, gizzards, and intestines were analysed in 321 of the 361 birds collected. Diet was similar in certain species (Aythya fuligula, A. f. ferina, Anas querquedula) despite differences in the trophic state of their habitats. However, in other species (Anas p. platyrhyncha, Aythya nyroca, Bucephala c. clangula), percentage distribution of food items more or less reflected the food resources of the two areas in the digestive tracts. I concluded that the former species are highly selective in their feeding.