Summary In aquatic settings, light can stimulate algal growth to affect microbial transformation of organic substrates. These effects may depend on dissolved nutrients that differentially constrain microbial autotrophy and heterotrophy to drive contrasting carbon (C) and phosphorus (P) dynamics during decomposition. We incubated sugar maple (Acer saccharum) litter under three dissolved P amendments (0, 50 or 500 μg L−1 P) and two light levels (14 or 475 μmol photons m−2 s−1) in laboratory microcosms. We measured litter chlorophyll a, microbial respiration and net metabolism, carbon:nitrogen (C:N) and C:P content, microbial P uptake and release and litter decomposition over 134 days. Elevated dissolved P increased algal biomass in the high‐light treatment and magnified net heterotrophy and autotrophy in the low‐ and high‐light treatments, respectively. Litter C:P and C:N declined as dissolved P increased, and litter C:P was further reduced by high light only in the highest P treatment. Microbial P uptake fluxes peaked under moderate P and high light, whereas P release fluxes were consistently low throughout the experiment. The percent of P uptake that was released was significantly higher under low light. High light stimulated decomposition under low P but slowed decomposition under high P, suggesting increased nutrients weakened algal priming of litter decomposition. Our study suggests factors controlling the degree of autotrophy versus heterotrophy on organic matter, such as light and nutrient availability, may interactively shift litter C and P dynamics during decomposition.

Long-chain ω-(o-alkylphenyl)alkanoic acids (APAAs) derived from the heating of unsaturated fatty acids have been widely used for the identification of aquatic products in archaeological ceramic vessels. To date, little attention has been paid to the diagnostic potential of shorter chain (< C 20 ) APAAs, despite their frequent occurrence. Here, a range of laboratory and field experiments and analyses of archaeological samples were undertaken to investigate whether APAAs could be used to further differentiate different commodities. The results provide new insights about the conditions for the formation of APAAs and enable the proposition of novel criteria to distinguish different natural products.

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Staphylococcus aureus can be carried on the skin and nasal passages of humans and animals as a commensal. A case of human methicillin-resistant S. aureus infection resulting from contact with pork has been reported. Poultry carcasses are sold at retail with the skin intact, but pork and beef typically are not. Thus, the risk of methicillin-resistant S. aureus human infection from whole raw poultry carcasses may be greater than that of exposure from pork or beef. The objective of this study was to isolate and characterize S. aureus from whole retail poultry carcasses and compare the isolates to S. aureus isolates from humans. A total of 25 S. aureus isolates were collected from 222 whole poultry carcasses. The isolates were characterized phenotypically with antibiotic resistance disc diffusion assays and genotypically using multilocus sequence typing. A total of 17 S. aureus isolates obtained from healthy humans were included and characterized in the same way as the poultry isolates. Staphylococcus spp. were recovered from all poultry carcasses. Only 25 poultry carcasses (11.2%) were contaminated with S. aureus. Of these 25 isolates, 36% were resistant to at least one of the antibiotics tested and 20% were resistant to two or more antibiotics tested. However, 100% of the human isolates were resistant to at least one of the antibiotics and 94% were resistant to two or more antibiotics. The results of the multilocus sequence typing indicate that most of the isolates grouped according to source. These results indicate a low prevalence of S. aureus present in poultry, and the isolates were not phenotypically similar to human isolates. The low number of S. aureus isolates from this study indicates that chicken carcasses would appear to not be a significant source of this bacterium.

Pathogens are a major cause of water quality impairment and public health concern world-wide.In the United States, each state is tasked with developing water quality standards (WQS) to protect the designated use(s) of waterbodies. Several streams in the Illinois River Watershed in northwest Arkansas are currently listed as impaired due to elevated levels of pathogens. Our objective was to evaluate Escherichia coli (E. coli) numbers at 29 stream sites, compare these numbers to the applicable WQS, and investigate the relationship between E. coli numbers and land cover variables.E. coli numbers in samples collected at most sites were within allowable limits, although there were several instances of violations of the WQS. Violations were variable from year to year at some sites, and elevated levels of E. coli were spatially localized during baseflow. Violations also were positively related to pasture land cover in the drainage area, and particularly within the riparian buffer area.This relationship was non-linear, or threshold based, where there was a significant increase in the mean E. coli exceedances when riparian pasture land cover was greater than approximately 50%.These results can be used to identify specific stream reaches where E. coli numbers might be elevated and the implementation of best management practices can be geographically targeted.

The Fayetteville Shale within north central Arkansas is an area of extensive unconventional natural gas (UNG) production. Recently, the Scott Henderson Gulf Mountain Wildlife Management Area (GMWMA) was leased from the state of Arkansas for NG exploration, raising concerns about potential impacts on water resources. From November 2010 through November 2014, we monitored four reaches of the South Fork Little Red River (SFLRR), within the GMWMA, establishing baseline physico-chemical characteristics prior to UNG development and assessing trends in parameters during and after UNG development. Water samples were collected monthly during baseflow conditions and analyzed for conductivity, turbidity, ions, total organic carbon (TOC), and metals. All parameters were flow-adjusted and evaluated for monotonic changes over time. The concentrations of all constituents measured in the SFLRR were generally low (e.g., nitrate ranged from <0.005 to 0.268 mg/l across all sites and sample periods), suggesting the SFLRR is of high water quality. Flow-adjusted conductivity measurements and sodium concentrations increased at site 1, while magnesium decreased across all four sites, TOC decreased at sites 1 and 3, and iron decreased at site 1 over the duration of the study. With the exception of conductivity and sodium, the physico-chemical parameters either decreased or did not change over the 4-year duration, indicating that UNG activities within the GMWMA have had minimal or no detectable impact on water quality within the SFLRR. Our study provides essential baseline information that can be used to evaluate water quality within the SFLRR in the future should UNG activity within the GMWMA expand.

All 54 km of the West Fork of the White River (WFWR) were on Arkansas's 303(d) list of impaired waterbodies for turbidity, total dissolved solids (TDS), and sulfate for many years. This study identifies which river segments fail to meet applicable water quality standards (WQS) and investigates possible anthropogenic or natural sources of pollutants. We also evaluated a larger dataset of 119 sites in the Boston Mountains and Ozark Highlands ecoregions, compiled from the Arkansas Department of Environmental Quality online database. In the WFWR, water samples were collected once or twice a month at nine sites from June 2014 through June 2018. Median values for turbidity, TDS, sulfate, and chloride ranged from 1.8 to 10.8 NTU, 40.8 to 151.3 mg/L, 3.5 to 27.9 mg/L, and 3.2 to 5.5 mg/L, respectively, and generally increased from upstream to downstream (p < 0.05). Violations of the water quality standard for the parameters of interest varied by site, but generally occurred in the downstream portion of the WFWR, where land use, riparian soils, and underlying geology change. In the larger dataset, turbidity, TDS, sulfate, and chloride concentrations were all significantly greater in the Ozark Highlands than the Boston Mountains ecoregion (p < 0.05). Anthropogenic activities influence dissolved ion concentrations across these study sites, while geology and riparian soils may be important factors for differences in sulfate and turbidity.