DEVELOPMENT AND APPLICATION OF A SPATIAL HYDROLOGY MODEL OF OKEFENOKEE SWAMP,GEORGIA1

ABSTRACT: :The model described herein was used to assess effects of the Suwannee River sill (a low earthen dam constructed to impound the Suwannee River within the Okefenokee National Wildlife Refuge to eliminate wildfires) on the hydrologic environment of Okefenokee Swamp, Georgia. Developed with Arc/Info Macro Language routines in the GRID environment, the model distributes water in the swamp landscape using precipitation, inflow, evapotranspiration, outflow, and standing water. Water movement direction and rate are determined by the neighborhood topographic gradient, determined using survey grade Global Positioning Systems technology. Model data include flow rates from USGS monitored gauges, precipitation volumes and water levels measured within the swamp, and estimated evapotranspiration volumes spatially modified by vegetation type. Model output in semi‐monthly time steps includes water depth, water surface elevation above mean sea level, and movement direction and volume. Model simulations indicate the sill impoundment affects 18 percent of the swamp during high water conditions when wildfires are scarce and has minimal spatial effect (increasing hydroperiods in less than 5 percent of the swamp) during low water and drought conditions when fire occurrence is high but precipitation and inflow volumes are limited.     

Null model analysis of species nestedness patterns

Nestedness is a common biogeographic pattern in which small communities form proper subsets of large communities. However, the detection of nestedness in binary presence-absence matrices will be affected by both the metric used to quantify nestedness and the reference null distribution. In this study, we assessed the statistical performance of eight nestedness metrics and six null model algorithms. The metrics and algorithms were tested against a benchmark set of 200 random matrices and 200 nested matrices that were created by passive sampling. Many algorithms that have been used in nestedness studies are vulnerable to type I errors (falsely rejecting a true null hypothesis). The best-performing algorithm maintains fixed row and fixed column totals, but it is conservative and may not always detect nestedness when it is present. Among the eight indices, the popular matrix temperature metric did not have good statistical properties. Instead, the Brualdi and Sanderson discrepancy index and Cutler's index of unexpected presences performed best. When used with the fixed-fixed algorithm, these indices provide a conservative test for nestedness. Although previous studies have revealed a high frequency of nestedness, a reanalysis of 288 empirical matrices suggests that the true frequency of nested matrices is between 10% and 40%.     

Does geopolitical risk escalate CO2 emissions? Evidence from the BRICS countries

Environmental Science and Pollution Research - High levels of CO2 emissions are extensively cited as one of the main global concerns nowadays. Therefore, researchers have been investigating the...     

Vertical response of microbial community and degrading genes to petroleum hydrocarbon contamination in saline alkaline soil

A column microcosm was conducted by amending crude oil into Dagang Oilfield soil to simulate the bioremediation process. The dynamic change of microbial communities and metabolic genes in vertical depth soil from 0 to 80 cm were characterized to evaluate the petroleum degradation potential of indigenous microorganism. The influence of environmental variables on the microbial responds to petroleum contamination were analyzed. Degradation extent of 42.45% of n-alkanes(C8–C40) and 34.61% of 16ΣPAH were reached after 22 weeks. Relative abundance of alkB, nah, and phe gene showed about 10-fold increment in different depth of soil layers. Result of HTS profiles demonstrated that Pseudomonas, Marinobacter and Lactococcus were the major petroleum-degrading bacteria in0–30 and 30–60 cm depth of soils. Fusarium and Aspergillus were the dominant oil-degrading fungi in the 0–60 cm depth of soils. In 60–80 cm deep soil, anaerobic bacteria such as Bacteroidetes, Lactococcus, and Alcanivorax played important roles in petroleum degradation.Redundancy analysis(RDA) and correlation analysis demonstrated that petroleum hydrocarbons(PHs) as well as soil salinity, clay content, and anaerobic conditions were the dominant effect factors on microbial community compositions in 0–30, 30–60, and 60–80 cm depth of soils, respectively.     

Depth distribution and temperature preferences of wahoo (Acanthocybium solandri) off Baja California Sur, Mexico

The depth distribution and temperature preferences of wahoo (Acanthocybium solandri) were quantified in the eastern North Pacific using archival tags. One hundred and eight data-loggers were deployed on wahoo (105?C165-cm fork length) from 2005 to 2008 at three locations off of the coast of Baja California Sur, Mexico (Alijos Rocks, 25°00??N/115°45??W; Magdalena Bay Ridge, 25°55??N/113°21??W; Hurricane Bank, 16°51??N/117°29??W). Twenty-five tagged individuals (23%) were recaptured within close proximity (<20?km) of their release sites. Collectively, depth and temperature data from 499?days revealed a predominant distribution within the upper mixed layer, with an average (±SD) depth of 18?±?4?m during the day and 17?±?6?m at night. Wahoo spent 99.2% of the daytime and 97.9% of night above the thermocline, and the greatest depth achieved by any fish was 253?m. Mean dive duration (3.8?±?2.9 vs. 2.3?±?0.8?min) and the vertical rate of movement (3.8?±?1.3 vs. 3.0?±?0.5?m?min^?1) were greater at night when compared to day. Ambient temperatures obtained from tag records ranged from 11.1 to 27.9°C, with an average of 25.0?±?1.1°C. These data identify the importance of the warm, upper mixed layer for the wahoo. High recapture rates proximal to the deployment sites suggest seasonal site fidelity and reveal the economic importance of this resource to both commercial and recreational fisheries of the region.