Wade Sheldon - Academia.edu (original) (raw)

Papers by Wade Sheldon

The volume of monitoring data that can be acquired and managed by Long Term Ecological Research s... more The volume of monitoring data that can be acquired and managed by Long Term Ecological Research sites and environmental observatories has increased exponentially over time, thanks to advances in sensor technology and computing power combined with steady decreases in data storage costs. New directions in environmental monitoring, such as sensor networks and instrumented platforms with real-time data telemetry, are raising the bar even higher. Quality control is often a major challenge with real-time data, though, due to poor scalability of traditional software tools, approaches and analysis methods. Software developed at the Georgia Coastal Ecosystems Long Term Ecological Research Site (GCE Data Toolbox for MATLAB) has proven very effective for quality control of both real-time and legacy data, as well as interactive analysis during post processing and synthesis. This paper describes the design and operation of the dynamic, rule-based quality control framework provided by this software, and presents quantitative performance data that demonstrate these tools can efficiently perform quality analysis on million-record data sets using commodity computer hardware.

Bioscience, 2013

Sensor networks are revolutionizing environmental monitoring by producing massive quantities of d... more Sensor networks are revolutionizing environmental monitoring by producing massive quantities of data that are being made publically available in near real time. These data streams pose a challenge for ecologists because traditional approaches to quality assurance and quality control are no longer practical when confronted with the size of these data sets and the demands of real-time processing. Automated methods for rapidly identifying and (ideally) correcting problematic data are essential. However, advances in sensor hardware have outpaced those in software, creating a need for tools to implement automated quality assurance and quality control procedures, produce graphical and statistical summaries for review, and track the provenance of the data. Use of automated tools would enhance data integrity and reliability and would reduce delays in releasing data products. Development of community-wide standards for quality assurance and quality control would instill confidence in sensor data and would improve interoperability across environmental sensor networks.

During incubation of seawater in bottles, the decrease in dissolved oxygen is often nonlinear ove... more During incubation of seawater in bottles, the decrease in dissolved oxygen is often nonlinear over time scales frequently used to measure respiration. Numbers of bacteria always increase, and rates of assimilation of dissolved leucine often increase exponentially. This suggests that sample handling disrupts the previously existing food web, leading to shifts of trophic state and unbalanced growth. Potential errors in measuring respiratory rate can be minimized by documenting these variables.

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ABSTRACT We fed juvenile channel catfish Ictalurus punctatus purified diets containing different ... more ABSTRACT We fed juvenile channel catfish Ictalurus punctatus purified diets containing different lipid sources for 90–110 d to examine the influence of dietary lipids on intracellular killing of Edwardsiella ictaluri by pronephros macrophages. The diets contained either menhaden oil, soybean oil, beef tallow, or a combination ofall three lipids. We performed the study with nonimmune and immunized fish acclimated to optimal (28°C) and suboptimal (19°C) temperatures. In both temperature trials, bactericidal activity was positively correlated with the level of n-3 fatty acids in the diet (particularly long-chain highly unsaturated fatty acids). Vaccination resulted in substantially enhanced bactericidal activity, except at suboptimal temperature in fish fed the diet containing beef tallow (primarily saturated and monoenoic fatty acids). Overall results were similar at optimal and suboptimal temperatures. This study demonstrates the potential for nutritional manipulation of disease resistance in fish and illustrates the need for standardized diets in fish health research.

Applied and environmental microbiology, 1994

Microbial Ecology, 1993

Bacterial isolates from the subtropical southeastern continental shelf were cultured in a matrix ... more Bacterial isolates from the subtropical southeastern continental shelf were cultured in a matrix of temperature and substrate concentrations encompassing a range of temperature and substrate concentrations equal to and exceeding natural ones. At the annual minimum temperature, marine heterotrophic bacterial isolates required higher concentrations of dissolved substrates for active growth than are usually found in seawater. We show this to result from a nonlinear interaction of the combined effects of temperature and substrate concentration on bacterial growth and respiratory rate. As a result, bacterial and protozoan utilization of phytoplankton production during winter and early spring is low, permitting greater energy flow to zooplankton and benthic animals, while in late spring, summer, and fall, the microbial loop dominates energy flux and organic carbon utilization. Escherichia coli shows a similar nonlinear response to temperature at minimal substrate concentrations, albeit at a higher range of concentrations than were utilized by the marine isolates. Thus, bacteria from subtropical regions are shown to have a differential growth response near the minimum temperature for growth, depending on the concentration of available substrates.

Marine Chemistry, 2004

Fluorescence-based observations provide useful, sensitive information concerning the nature and d... more Fluorescence-based observations provide useful, sensitive information concerning the nature and distribution of colored dissolved organic matter (CDOM) in coastal and freshwater environments. The excitation -emission matrix (EEM) technique has become widely used for evaluating sources and sinks of CDOM. Water scattering peaks, however, can create problems for quantitative analysis and display of the EEMs, especially for samples with low CDOM concentrations. Here we report a new method for eliminating Rayleigh and Raman scatter peaks from EEMs during post-processing of the data in MATLABR. An algorithm was developed to excise scatter peaks (i.e. peak emission F 10 -15 nm at each excitation wavelength) from the scan data and replace the excised values using three-dimensional interpolation of the remaining data (Delaunay triangulation method). The interpolated surface was constrained to pass through the non-excised values so that only data in excised portions were replaced. Tests of the algorithm in non-scatter regions indicate expected deviations of 0 -4% for interpolated regions of DOM fluorescence peaks (i.e. difference between measured and interpolated intensity after removal/interpolation), which is within machine error for the primary observations. This new scattering correction method is shown to provide much improved results in the quantitative analysis of EEMs compared to the conventional blanksubtraction procedure. The method is used to process EEMs and fluorescence quantum yields for water samples obtained along a salinity transect in a river located on the coast of the southeastern United States. Results of this analysis demonstrate observed shifts in EEM peak positions along most of the transect cannot be accounted for by a simple model that computes EEMs as a function of salinity assuming that the dominant driver of EEM spectral change is mixing between riverine and marine waters within the estuary. Other results show that fluorescence apparent quantum yields (AQYs) increased with increasing salinity and pH in the estuary and that the highest quantum yields are observed on excitation by 350 -380-nm light. Modeling results and the observed EEM spectral changes indicate that photoreactions had an important effect on the fluorescent dissolved organic matter (FDOM) optical properties in the estuary. The increase in fluorescence quantum yields with increasing salinity and pH in the estuary likely were caused by reactions involving magnesium or hydroxide ions that reduced fluorescence quenching by chelated iron and possibly other paramagnetic ions. The results of the study indicate that 0304-4203/$ -see front matter D Marine Chemistry 89 (2004) 15 -36 EEM analysis with careful scatter correction can provide a powerful tool for evaluating pathways for carbon cycling in estuaries. D

Limnology and Oceanography, 2002

Quantum yield spectra for the photochemical formation of biologically labile photoproducts from d... more Quantum yield spectra for the photochemical formation of biologically labile photoproducts from dissolved organic matter (DOM) have not been available previously, although they would greatly facilitate attempts to model photoproduct formation rates across latitudinal, seasonal, and depth-related changes in spectral irradiance. Apparent quantum yield spectra were calculated for two coastal environments from the southeastern United States using postirradiation bacterial respiration as a measure of total labile photoproduct formation and a cutoff filter method to model spectral dependence. As has been the case for previously studied classes of DOM photoproducts (i.e., dissolved inorganic carbon, CO, and H 2 O 2 ), ultraviolet (UV)-B irradiance was significantly more efficient at forming labile photoproducts (i.e., compounds readily assimilated by marine bacterioplankton) than UV-A and visible irradiance. Calculations of DOM photoproduct formation in southeastern U.S. coastal surface waters indicate a formation ratio for biologically labile photoproducts : CO of 13 : 1. The slope of a natural log plot of the apparent quantum yield spectrum obtained for biologically labile photoproducts was similar to that for CO (0.028 nm Ϫ1 vs. 0.034 nm Ϫ1 ). Modeled kinetic rates therefore indicate that the production ratio of these photoproduct classes is approximately maintained despite variations in the solar spectrum that occur with depth in a water column or distance from shore. Application of the apparent quantum yield to coastal regions worldwide predicts an annual formation rate of biologically labile photoproducts in coastal waters of 206 ϫ 10 12 g C.

Limnology and Oceanography, 2000

... biological degradation of estuarine dissolved organic matter Mary Ann Moran and Wade M. Sheld... more ... biological degradation of estuarine dissolved organic matter Mary Ann Moran and Wade M. Sheldon, Jr. Department of Marine Sciences, University of Georgia, Athens, Georgia 30602-3636 ... inside the water bath. Two additional dark control treatments were also established. ...

Journal of Aquatic Animal Health, 1991

... WADE M. SHELDON, JR.,! AND VICKI S. BLAZER2 Cooperative Fish and Wildlife Research Unit* Scho... more ... WADE M. SHELDON, JR.,! AND VICKI S. BLAZER2 Cooperative Fish and Wildlife Research Unit* School of Forest Resources, University of Georgia, Athens, Georgia 306021 USA ... Optimal temperature (28*C) MO SO BT CO 6.7 ± 2.0 z 6.9 ± 1.8 z 7.3 ± 2.0 z 6.6 ± 1.2 z ...

Estuaries, 1999

The biological turnover of riverine dissolved organic carbon (DOC) discharged into five southeast... more The biological turnover of riverine dissolved organic carbon (DOC) discharged into five southeastern United States estuaries was examined in long-term respiration bioassays. Measures of bacterial oxygen consumption indicated surprisingly large differences in the inherent biodegradability of DOC among the five estuaries, despite their close geographic proximity. Differences of up to 13-fold in biodegradatlon rates were also found temporally within a single estuary. For most of the southeastern United States estuaries, measured rates of riverine DOC biodegradation were low relative to rates reported for other freshwater and marine environments. This was particularly true for the coastal plain ("blackwater") rivers that contribute about 35% of the riverine DOC exported to coastal marine environments in this region; extrapolation of biodegradation rates to the adjacent continental shelf predict biodegradation of a maximum of 11% of exported blackwater DOC within the estuary-shelf system (with transit times of up to 140 d). DOC from Piedmont rivers was more biologically labile, with maximum losses of 30% predicted within the estuary and adjacent shelf. Short exposures to natural sunlight increased the lability of the riverine DOC and enhanced biodegradation rates by over 3-fold in some cases, although significant inter-estuary differences in susceptibility of riverine DOC to photolysis were also evident.

BioScience, 2013

Emerging environmental grand challenges demand new scientific approaches that require collaborati... more Emerging environmental grand challenges demand new scientific approaches that require collaboration and integration of long-term, multi-site data across broad spatial and temporal scales. The Long-Term Ecological Research (LTER) Network and the U.S. Forest Service (USFS) Experimental Forest Network sites collect extensive long-term ecological, climatological, and hydrological data. While many of the LTER and USFS databases are available on-line with adequate

Growth responses and biovolume changes for four facultatively psychrophilic bacterial isolates fr... more Growth responses and biovolume changes for four facultatively psychrophilic bacterial isolates from Conception Bay, Newfoundland, and the Arctic Ocean were examined at temperatures from -1.5 to 35°C, with substrate concentrations of 0.15, 1.5, and 1,500 mg of proteose peptone-yeast extract per liter. For two cultures, growth in 0.1, 1.0, and 1,000 mg of proline per liter was also examined. At 10 to 15°C and above, growth rates showed no marked effect of substrate concentration, while at -1.5 and 0°C, there was an increasing requirement for organic nutrients, with generation times in low-nutrient media that were two to three times longer than in high-nutrient media. Biovolume showed a clear dependence on substrate concentration and quality; the largest cells were in the highest-nutrient media. Biovolume was also affected by temperature; the largest cells were found at the lowest temperatures. These data have implications for both food web structure and carbon flow in cold waters and-for the effects of global climate change, since the change in growth rate is most dramatic at the lowest temperatures.

Microbial Ecology, 2009

The phylogenetic diversity and composition of the bacterial community in anaerobic sediments from... more The phylogenetic diversity and composition of the bacterial community in anaerobic sediments from Sapelo Island, GA, USA were examined using 16S rRNA gene libraries. The diversity of this community was comparable to that of soil, and 1,186 clones formed 817 OTUs at 99% sequence similarity. Chao1 estimators for the total richness were also high, at 3,290 OTUs at 99% sequence similarity. The program RDPquery was developed to assign clones to taxonomic groups based upon comparisons to the RDP database. While most clones could be assigned to describe phyla, fewer than 30% of the clones could be assigned to a described order. Similarly, nearly 25% of the clones were only distantly related (<90% sequence similarity) to other environmental clones, illustrating the unique composition of this community. One quarter of the clones were related to one or more undescribed orders within the γ-Proteobacteria. Other abundant groups included the δ-Proteobacteria, Bacteroidetes, and Cyanobacteria. While these phyla were abundant in other estuarine sediments, the specific members at Sapelo Island appeared to be different from those previously described in other locations, suggesting that great diversity exists between as well as within estuarine intertidal sediments. In spite of the large differences in pore water chemistry with season and depth, differences in the bacterial community were modest over the temporal and spatial scales examined and generally restricted to only certain taxa.

Marine Ecology Progress Series, 1996

... Our cruise track was mostly in loose pack ice exceeding 50% ice cover, with heavier ice cover... more ... Our cruise track was mostly in loose pack ice exceeding 50% ice cover, with heavier ice cover near 75 degree N. We sampled over the ... suggest that rates of both autotrophic and heterotrophic biological activity in the upper mixed layer of the deep waters of the Arctic Ocean may ...