Integrated crop-livestock (ICL) systems have shown potential to provide a variety of environmental benefits including soil carbon (C) increases relative to conventional row cropping systems. However, studies documenting C dynamics of ICL systems in the northern Great Plains are lacking relative to other agroecosystems. Soil carbon dioxide (CO2) efflux, crop biomass, and soil organic matter (SOM) pools were monitored over 3 years in an ICL rotation (corn [Zea mays L.]/soybean [Glycine max L.]-spring wheat [Triticum aestivum L.] + cover crop-cover crop) with fall grazing, a conventional cropping system rotation (corn-spring wheat-soybean) and fall grazed and ungrazed mixed-grass pasture near Mandan, ND. Cropped treatments were under no-till management. Annual aboveground crop residue biomass C was similar in the ICL and conventional systems, while less in the grazed pasture (4.18, 3.83, and 1.21 Mg C ha(-1) year(-1) respectively; p = 0.039). Annual soil CO2 efflux was greater in the ICL, grazed, and ungrazed pasture systems than the conventional system (8.05, 8.73, 8.25, and 5.81 Mg C ha(-1) year(-1), respectively; p < 0.001). Among crop phases in the ICL and conventional cropping systems, cover crops contributed to greater CO2 efflux in the spring and fall. SOM and C mineralization were greater at 0-5 cm in the ICL system compared to the conventional cropping system (6.6% vs. 6.3%, p = 0.028 and 248 vs. 184 mg CO2-C kg(-1), p < 0.001, respectively). Interseeded cover crops in ICL systems can contribute increased root respiration and enhanced SOM pools relative to conventional cropping systems under semiarid conditions.

Pollution is one of the biggest threats to marine life and trace elements are among the most toxic pollutants in this environment. Zn is an essential trace element for biota but becomes toxic at high concentrations. Sea turtles are good bioindicators of trace element pollution, due to their longevity and cosmopolitan distribution that allow bioaccumulation for years in their tissues. Determining and comparing Zn concentrations in sea turtles from faraway places is relevant for conservation due to the lack of knowledge of geographically broader distribution patterns of Zn in vertebrates. In this study, comparative analyses of bioaccumulation in the liver, kidney, and muscles of 35 C. mydas from Brazil, Hawaii, the USA (Texas), Japan, and Australia of statistically equal sizes were performed. Zn was found in all specimens, with the highest levels in the liver and kidneys. Specimens from Australia (30.58 µg g −1 ), Hawaii (31.91 µg g −1 ), Japan (29.99 µg g −1 ), and the USA (33.79 µg g −1 ) showed statistically equal means in the liver. Kidney levels were the same in Japan (35.09 µg g −1 ) and the USA (37.29 µg g −1 ) and the same in Australia (23.06 µg g −1 ) and Hawaii (23.31 µg/g). Specimens from Brazil had the lowest means in both organs (12.17 µg g −1 in the liver and 9.39 µg g −1 in the kidney). The pattern of equal Zn values for most specimens in the liver is an important finding, demonstrating that there are pantropical patterns in the distribution of this metal even in regions so far from each other. A possible explanation is due to the essential nature of this metal linked to metabolic regulation, in addition to the bioavailability for biological absorption in marine environments, such as RS in Brazil, with a lower standard bioavailability also found in other organisms. Therefore, factors such as metabolic regulation and bioavailability indicate that there is a pantropical distribution of Zn in marine biota and green turtles can be a useful model as a sentinel species.

Recent interest in integrated crop-livestock (ICL) systems has prompted numerous investigations to quantify ecosystem service tradeoffs associated with management. However, few investigations have quantified ICL management effects on net global warming potential (GWP), particularly in semiarid regions. Therefore, we determined net GWP for grazed and ungrazed cropland in a long-term ICL study near Mandan, ND USA. Factors evaluated for their contribution to net GWP included carbon dioxide (CO 2 ) emissions associated with production inputs and field operations, methane (CH 4 ) emissions from enteric fermentation by beef cattle, change in soil carbon stocks, and soil-atmosphere CH 4 and nitrous oxide (N 2 O) fluxes. Net GWP was significantly greater for grazed cropland (946 kg CO 2equiv. ha -1 yr -1 ) compared to ungrazed cropland (200 kg CO 2equiv. ha -1 yr -1 ) (P=0.0331). The difference in net GWP between treatments was largely driven by emissions from enteric fermentation (602 kg CO 2equiv. ha -1 yr -1 ). Among other contributing factors, CO 2 emissions associated with seed production and field operations were lower under ungrazed cropland ( P = 0.0015 and 0.0135, respectively), while soil CH 4 uptake was greater under grazed cropland ( P = 0.0102). Soil-atmosphere N 2 O flux from each system negated nearly all the CO 2equiv. sink capacity accrued from soil carbon stock change. As both production systems resulted in net greenhouse gas (GHG) emissions to the atmosphere, novel practices that constrain GHG sources and boost GHG sinks under semiarid conditions are recommended.

Integrated crop-livestock (ICL) systems can improve profitability, production efficiencies, and reduce environmental degradation. Among the many environmental metrics important for assessing the sustainability of ICL systems, nitrous oxide (N2O) flux occupies a central role given its effect on net greenhouse gas balance of agricultural practices. Unfortunately, there is limited understanding of ICL system effects on N2O flux, particularly in North America. Therefore, we measured N2O flux from ICL and non-ICL practices near Mandan, ND USA using static chamber methodology over a 3-yr period (Oct 2016 - Oct 2019). Treatments included grazed and ungrazed cropland and grassland on a site with gently rolling topography and fertile Haplustoll soils. Grazing was done by yearling cattle in the fall of each year (0.41-0.76 ha steer(-1)). Maximum N2O flux from cropland generally occurred in March and April when soil moisture was abundant and air temperatures exceeded 0 degrees C (i.e., during spring snow melt). Nitrous oxide flux was over eight times greater under cropland compared to grassland (Mean = 33.7 vs. 4.1 mu g N2O-N m(-2) h(-1), respectively). However, N2O flux was not affected by grazing in either production system. Within cropland, N2O flux was greater in corn (Zea mays L.) and spring wheat (Triticum aestivum L.) phases of the rotation (Mean = 40.5 mu g N2O-N m(-2) h(-1)) compared to the soybean (Glycine max L.) and cover crop phases (Mean = 20 mu g N2O-N m(-2) h(-1)). Stepwise regression found N2O flux to be weakly related to volumetric water content when the soil was not frozen (r(2) < 0.2). Study outcomes suggest ICL systems including grasslands or grass-dominant cover crops will be most effective at mitigating N2O flux.

AbstractImpacts of integrated crop–livestock (ICL) systems on water quality have not been well studied. Water quality parameters were quantified for two 30‐min rainfall simulations in wheat (Triticum aestivum L.)–cover crop, cover crop, and rangeland grass control phases of a long‐term ICL study site in Mandan, ND, in 2017 and 2018. Both pre‐graze and post‐graze simulations were conducted. Nitrate‐N (NO3−–N), nitrite‐N (NO2−–N), ammonia‐N (NH4+–N), phosphate‐P (PO43−–P), and total suspended solid (TSS) concentrations and loads were evaluated in surface runoff water, along with concentrations of NO3−–N, NO2−–N, NH4+–N, and PO43−–P in infiltration water. Non‐parametric ranked two‐way analysis of variance was used to evaluate differences for vegetation type and grazing as fixed effects, with year as a random effect. Surface runoff concentrations of NO3−–N and NH4+–N were significantly different with cover crop and wheat phases being greater than grass. A grazing effect was also observed with pre‐graze significantly greater than post graze for NO2−–N, NH4+–N, PO43−–P, and TSS surface runoff concentrations. For infiltration water concentrations, similar significant effects of vegetation type were observed for NO3−–N and PO43−–P, while pre‐graze was also greater than post‐graze for NO2−–N and PO43−–P. Due to variable runoff volumes, no significant differences were observed for loads of any parameters. Minimal runoff volumes (0–6.7 L) and significant vegetation and grazing effects in nutrient infiltration water concentrations highlight the importance of infiltration in such studies, particularly at sites in the northern Great Plains.

AbstractIntegrated crop−livestock (ICL) system effects on soil organic carbon (SOC) and total nitrogen (TN) are highly variable due to differences in ecoregion‐specific management practices, historical land use, and inherent climatic/edaphic attributes. Few studies have evaluated ICL system effects on SOC and TN in semiarid regions, where soil attributes change slowly. This study quantified ICL system effects on SOC and TN in a long‐term experiment near Mandan, ND. Effects of three residue management treatments (Grazed, Removed, Control) on SOC and TN were determined at five depths (0−0.08, 0.08−0.15, 0.15−0.31, 0.31−0.61, and 0.61−0.91 m) in 1999 and 2014. No‐till practices were employed throughout the study following conversion of perennial grass pastures. A significance criterion of P ≤ .10 was used to assess treatment effects as the experimental design was constrained to two replications. Residue management affected SOC and TN in near‐surface depths only, with greater concentration of SOC and TN at 0−0.08 m under Grazed compared to Removed in 2014 (P = .0844 and .0576). When expressed on an equivalent mass basis, SOC stocks were greater under Grazed and Control compared to Removed. Soil organic C and TN stocks increased over time in the Control by 11.2 Mg C ha−1 and 1.2 Mg N ha−1, respectively (P = .0728 and .0868). Soil organic C stocks also increased over time under the Grazed treatment by 10 Mg C ha−1 (P = .0630). Study results highlighted the importance of residue retention and livestock grazing for increasing SOC and TN in ICL systems under semiarid conditions.

Integrated crop–livestock systems (ICLSs) can help increase food production while benefiting soils and the environment. This review summarizes recent impacts of ICLSs on crop and livestock production and rural economics and discusses lessons learned in the northern Great Plains (NGP). Research on ICLS conducted in the NGP indicates that the crop residue grazing, swath grazing, and annual forage grazing can positively influence crop production; whereas, livestock performance varies with season, forage nutritive value, and grazing management. Furthermore, ICLSs can reduce the costs and risks of agricultural production. The success of ICLSs in NGP region depends on trade‐offs, planning, economic benefits, policies, regulations, community acceptance, and management skills. The ICLSs could play a strategic role in future agricultural production. The lessons learned from adopting ICLSs in the NGP include the lack of available land for fertilizer (manure) management, that to implement ICLS practices skills and knowledge must be maintained, and ICLS provides an entry point for young farmers and ranchers however capital is needed. These experiences and lessons could be valuable references for producers to adopt ICLSs in the NGP or other regions.Core Ideas Integrated crop–livestock systems positively affect crop production by improving soil health. Common integrated crop–livestock system management techniques can enhance the northern Great Plains crop production. Integrated crop–livestock system livestock performance is impacted by season, forage selection, and management. Integrated crop–livestock systems can increase economic benefits and reduce economic risks. Experiences and lessons in the northern Great Plains could be valuable for other regions to adopt integrated crop–livestock systems.

Low-grade weirs placed within agricultural drainage ditches in the Lower Mississippi Alluvial Valley can be used as a management practice to enhance nitrogen removal. The addition of organic carbon amendments within ditches that contain weirs could further increase nitrogen removal. Through repeated trials, changes in NO 3 - -N concentration between inflow and outflow were variable in the ditch without weirs, while only decreases in concentration were observed in ditches with weirs. Significant differences in NO 3 - -N concentrations were observed between treatments, with greater removal of NO 3 - -N observed in dissolved organic carbon treatments compared to control and particulate organic carbon treatments. At medium- and high-flow rates, respectively, dissolved organic carbon treatments resulted in greater NO 3 - -N concentration decreases of 31.6% and 27.1% compared to 19% and 11.6% in particulate organic carbon treatments and 18.6% and 17.2% in control treatments. Significant effects of weirs and sampling date on nirS, nirK, nosZ, and 16S rRNA gene abundances were observed. Observed increases in NO 3 - -N removal with organic carbon amendments, provides support for continued investigation on improving the efficacy of organic carbon amendments as a best management practice for NO 3 - -N removal in agricultural drainage ditches. PRACTITIONER POINTS: Dissolved organic carbon amendments increased nitrate-nitrogen removal. Only decreases in nitrate-nitrogen concentration were observed in ditches with weirs. Increasing flow rate did not affect nitrate-nitrogen removal. Abundance of denitrification-performing microbes likely did not affect N removal. Lack of anaerobic soil conditions and short residence time reduced nitrate-N removal.

Cadmium (Cd) is a metal of toxicological interest because of its potential high toxicity to organisms and ability to biomagnify. Evaluating concentrations of Cd in organisms on a large spatial scale can provide insights to its global distribution. This study examined Cd concentrations in kidney and liver tissues of 137 specimens of green turtles (Chelonia mydas) collected in Australia, Brazil, Hawaii, Japan, and the continental United States (Gulf of Mexico). We used comparative analyses of kidney and liver of 35 individuals, of which seven turtles from each locality belong to the same size class for comparison purposes between their ocean of origin. Cd was detected in all samples, with the highest bioconcentration in kidneys. Specimens originating from the Pacific Ocean had significantly higher mean Cd levels in liver (13.24 mu g/g) and kidney (34.17 mu g/g) than the specimens collected in the Atlantic Ocean with lower mean values in liver (1.00 mu g/g) and kidney (4.04 mu g/g). Furthermore, Cd concentrations in turtle tissues were generally greater than concentrations found in other marine organisms, for example dolphins. This result was unexpected because dolphins occupy a higher trophic level than green turtles which are only herbivorous. A possible explanation is a change in feeding habits of green turtles, in which juveniles feed in near shore habitats, potentially resulting in greater Cd accumulation in juveniles compared to adults. This global distribution trend has also been observed in other marine organisms (e.g., insects, birds, and mammals) and indicates that global factors may be more important than regional factors in determining Cd concentrations of marine organisms. Capsule: Global factors are more relevant than local factors in the distribution of cadmium in biota, using green turtle as a sentinel species. (C) 2018 Elsevier B.V. All rights reserved.

Integrated crop-livestock systems hold potential to achieve environmentally sustainable production of crop and livestock products. Although previous studies suggest that integrated crop-livestock systems improve soil health, impacts of integrated crop-livestock systems on water quality and aquatic ecosystems are largely unknown. This review (i) summarizes studies examining surface water quality and soil leachate for management practices commonly used in integrated crop-livestock systems (e.g., no-till, cover crops, livestock grazing) with emphasis on the Northern Great Plains ecoregion of North America, (ii) quantifies management system effects on nutrient and total suspended solids concentrations and loads, and (iii) identifies information gaps regarding water quality associated with integrated crop-livestock systems and research needs in this area. In general, management practices used in integrated crop-livestock systems reduced losses of total suspended solids, nitrogen (N), and phosphorus (P) in surface runoff and soil leachate. However, certain management practices (e.g., no-till or reduced tillage) reduced losses of total N (relative median change = -65%), whereas soluble P losses in runoff increased (57%). Conversely, practices such as grazing increased median total suspended solids (22%), nitrate (45%), total N (85%), and total P (25%) concentrations and loads in surface runoff and aquatic ecosystems. An improved understanding of the interactive effects of integrated crop-livestock management practices on surface water quality and soil leachate under current and future climate scenarios is urgently needed. To close this knowledge gap, future studies should focus on determining concentrations and loads of total suspended solids, N, P, and organic carbon in runoff and soil leachate from integrated crop-livestock systems.

Measurement of greenhouse gas (GHG) flux using static chamber methods typically occurs immediately following sample collection. However, situations may arise requiring sample storage prior to analysis by gas chromatography. The objective of this study was to determine effects of storage time and temperature on carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) concentrations in vials containing "low" and "high" concentrations of certified standards. Samples were stored for 3, 7, 14, 28, and 84 days at four storage temperatures: room temperature, 25 degrees C, 4 degrees C, and -10 degrees C. Results indicated low and high concentration standards were not impacted by sample storage up to 28 days at any storage temperature. After 84 days, CO2 concentrations were 0.6-14.4% lower than expected while CH4 concentrations were up to 22% greater than expected. Results from future studies will allow for further refinement of scientifically supported guidance regarding appropriate storage temperature and time of GHG samples. Few studies have examined impacts of storage time and temperature on GHG samples retained in traditional septa-capped vials. Effects of storage time and temperature on GHG samples were examined. Based on this study, GHG samples can be stored for up to 28 days at temperatures ranging from -10 degrees C to 25 degrees C. (C) Published by Elsevier B.V.

Agricultural non-point sources of nutrients and sediments have caused eutrophication and other water quality issues in aquatic and marine ecosystems, such as the annual occurrence of hypoxia in the Gulf of Mexico. Management practices have been implemented adjacent to and in agricultural drainage ditches to promote their wetland characteristics and functions, including reduction of nitrogen, phosphorus, and sediment losses downstream. This review: (1) summarized studies examining changes in nutrient and total suspended solid concentrations and loads associated with management practices in drainage ditches (i.e., riser and slotted pipes, two-stage ditches, vegetated ditches, low-grade weirs, and organic carbon amendments) with emphasis on the Lower Mississippi Alluvial Valley, (2) quantified management system effects on nutrient and total suspended solid concentrations and loads and, (3) identified information gaps regarding water quality associated with these management practices and research needs in this area. In general, management practices used in drainage ditches at times reduced losses of total suspended solids, N, and P. However, management practices were often ineffective during storm events that were uncommon and intense in duration and volume, although these types of events could increase in frequency and intensity with climate change. Studies on combined effects of management practices on drainage ditch water quality, along with research towards improved nutrient and sediment reduction efficiency during intense storm events are urgently needed.

Several different materials have been used for production of domestic water pipes throughout history. In recent years, the use of cross-linked polyethylene (PEX) pipe has increased dramatically. Yet, the potential for leaching of phthalates, which are endocrine disrupting compounds associated with adverse reproductive effects in humans, has not been examined. In this study, the potential of chlorinated polyvinyl chloride (cPVC) and red, blue, and heat PEX piping to leach phthalates into static hot and cold water after 2, 8, and 48 hours was evaluated. Concentrations of six phthalates, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl-butyl phthalate (BBP), di(2-ethylhexyl) phthalate, and di(n-octyl) phthalate, were determined by gas chromatography-mass spectrometry. Pipe type (F3,71 = 15.6, P = 0.001) contributed significantly to phthalate concentrations in water, while temperature (F4,71 = 1.74, P = 0.106) and time (F4,71 = 1.02, P = 0.427) were not significant factors. Significantly higher concentrations of DEP, DBP, and BBP were observed in cPVC pipe (<method detection limits (MDL) to 466 ng L−1, 252–4,219 ng L−1, 473–18,400 ng L−1, respectively) compared to blue PEX (T2 = 12.2, P < 0.001; <MDL, <MDL − 140 ng L−1, <MDL − 459 ng L−1, respectively), red PEX (T2 = 19.3, P < 0.001; <MDL, <MDL − 188 ng L−1, <MDL − 881 ng L−1, respectively), and heat PEX (T2 = 19.9, P < 0.001; <MDL, <MDL − 162 ng L−1, <MDL − 169 ng L−1, respectively). Phthalate exposure from drinking water via cPVC or PEX is low when compared to other dietary sources. Nonetheless, a shift from cPVC to PEX pipes in households would decrease potential exposure to phthalates.

The 1972 Clean Water Act was passed to protect chemical, physical, and biological integrity of United States’ waters. The U.S. Environmental Protection Agency and U.S. Army Corps of Engineers codified a new “waters of the United States” rule on June 29, 2015, because several Supreme Court case decisions caused confusion with the existing rule. Climate change could affect this rule through connectivity between groundwater and surface waters; floodplain waters and the 100-year floodplain; changes in jurisdictional status; and sea level rise on coastal ecosystems. Four approaches are discussed for handling these implications: (1) “Wait and see”; (2) changes to the rule; (3) use guidance documents; (4) Congress statutorily defining “waters of the United States.” The approach chosen should be legally defensible and achieved in a timely fashion to provide protection to “waters of the United States” in proactive consideration of scientifically documented effects of climate change on aquatic ecosystems.

Agricultural fertilizer applications have resulted in loading of nutrients to agricultural drainage ditches in the Lower Mississippi Alluvial Valley. The purpose of this study was to determine effects of dissolved organic carbon (DOC) and particulate organic carbon (POC) amendments on nitrate-nitrogen (NO3 −-N) removal from overlying water, pore water, and sediment of an agricultural drainage ditch. Two experiments were conducted. In experiment 1, control (i.e., no amendment), DOC, and POC treatments were applied in laboratory microcosms for time intervals of 3, 7, 14, and 28 days. In experiment 2, control, DOC, and POC treatments were applied in microcosms at C/N ratios of 5:1, 10:1, 15:1, and 20:1. There were statistically significant effects of organic carbon amendments in experiment 1 (F 2,71 = 27.1, P < 0.001) and experiment 2 (F 2,53 = 39.1, P < 0.001), time (F 1,71 = 14.5, P < 0.001) in experiment 1, and C/N ratio (F 1,53 = 36.5, P < 0.001) in experiment 2. NO3 −-N removal varied from 60 to 100 % in overlying water among all treatments. The lowest NO3 −-N removals in experiment 1 were observed in the control at 14 and 28 days, which were significantly less than in DOC and POC 14- and 28-day treatments. In experiment 2, significantly less NO3 −-N was removed in overlying water of the control compared to DOC and POC treatments at all C/N ratios. Amendments of DOC and POC made to drainage ditch sediment: (1) increased NO3 −-N removal, especially over longer time intervals (14 to 28 days); (2) increased NO3 −-N removal, regardless of C/N ratio; and (3) NO3 −-N removal was best at a 5:1 C/N ratio. This study provides support for continued investigation on the use of organic carbon amendments as a best management practice for NO3 −-N removal in agricultural drainage ditches.

Inorganic elements from anthropogenic sources have entered marine environments worldwide and are detectable in marine organisms, including sea turtles. Threatened and endangered classifications of sea turtles have heretofore made assessments of contaminant concentrations difficult because of regulatory restrictions on obtaining samples using nonlethal techniques. In the present study, claw and skin biopsy samples were examined as potential indicators of internal tissue burdens in green sea turtles (Chelonia mydas). Significant relationships were observed between claw and liver, and claw and muscle concentrations of mercury, nickel, arsenic, and selenium (p < 0.05). Similarly, significant relationships were observed between skin biopsy concentrations and those in liver, kidney, and muscle tissues for mercury, arsenic, selenium, and vanadium (p < 0.05). Concentrations of arsenic, barium, chromium, nickel, strontium, vanadium, and zinc in claws and skin biopsies were substantially elevated when compared with all other tissues, indicating that these highly keratinized tissues may represent sequestration or excretion pathways. Correlations between standard carapace length and cobalt, lead, and manganese concentrations were observed (p < 0.05), indicating that tissue concentrations of these elements may be related to age and size. Results suggest that claws may indeed be useful indicators of mercury and nickel concentrations in liver and muscle tissues, whereas skin biopsy inorganic element concentrations may be better suited as indicators of mercury, selenium, and vanadium concentrations in liver, kidney, and muscle tissues of green sea turtles. Environ Toxicol Chem 2014; 33:2020–2027. © 2014 SETAC

Playa wetlands are important components of the Southern High Plains (USA) landscape as they are the major aquatic surface feature. Chemical contaminants associated with playas have been documented, particularly for grassland and agricultural watersheds, but not for playas in urban settings. The objectives of this study were to determine concentrations of inorganic and organic contaminants in sediments from an urban playa within the I-20 Wildlife Preserve and Jenna Welch Nature Study Center in Midland, TX, and evaluate toxicity of these sediments to Hyalella azteca. Concentrations of most trace elements were below sediment quality guidelines with exceptions of lead, cadmium, and arsenic. Concentrations of organic contaminants, particularly PAHs, DDT, DDE, and malathion, were above sediment quality guidelines at various locations within the playa. Decreased survival was observed among H. azteca exposed to sediment from a single location when compared those exposed to reference sediments. This location also produced maximum observed concentrations for five of seven trace elements, potentially due to its location at the lowest elevation within the playa. This study documented concentrations of contaminants in sediments of an urban playa associated with past and present land uses in its urban setting, including those from automotive emissions and historical pesticide use.

Dispersants are applied to marine crude oil spills to enhance microbial degradation and reduce impacts of crude oils on ecosystems. In summer 2010, the dispersant Corexit 9500 was applied to crude oil in the Gulf of Mexico. The co-occurrence of the Deepwater Horizon oil spill with nesting efforts of birds in the Gulf region may have resulted in exposure of adult birds, and subsequently bird eggs, to combinations of crude oil and Corexit 9500. The objective of this study was to examine the embryotoxicity of 50:1 and 10:1 mixtures of weathered crude oil collected from the Gulf of Mexico and Corexit 9500 applied to mallard duck eggs. Combinations of weathered crude oil and Corexit 9500 were applied to eggshells of mallard ducks via paintbrush in varying masses ranging from 0.1 to 59.9 mg and 0.1 to 44.9 mg for 50:1 and 10:1 mixtures, respectively. Conservatively derived median lethal applications for 50:1 and 10:1 mixtures of weathered crude oil and Corexit 9500 were 21.3 ± 4.9 mg/egg (321.8 μg/g egg) and 33.1 ± 11.8 mg/egg (517.0 μg/g egg), respectively. Spleen mass of hatchlings exposed to the 50:1 mixture was the only physiological measure significantly different from controls of both mixtures. Results indicated that decreasing ratios of dispersant relative to weathered crude oil decreased toxicity to mallard embryos. In comparison to treatments of eggs with weathered crude oil alone, toxicity increased when the oil to dispersant ratio was 50:1, but decreased with the mixture that contained more dispersant (10:1).

The synthetic growth-promoting hormones trenbolone and melengestrol acetate have been detected in the environment near beef cattle feedlots and are reportedly transported via wind-borne particulate matter. Therefore, movement of synthetic hormones from beef cattle feedlots to water bodies via particulate matter is possible. Our objective was to evaluate potential effects of 17α-trenbolone (17α-TB), melengestrol acetate (MGA), and combinations of both on growth, development, and survival of Xenopus laevis larvae. On post-hatch day 2 (stage 33/34), X. laevis larvae were exposed to three nominal concentrations of 17α-TB (10, 100, and 500 ng/L), MGA (1, 10, and 100 ng/L), a combination of both (1/10, 10/100, and 100/500 ng/L MGA/17α-TB), frog embryo teratogenesis assay-Xenopus medium, or a solvent control. Significant increases in all X. laevis growth metrics were observed among larvae in the 1 ng/L MGA + 10 ng/L 17α-TB and 10 ng/L MGA + 100 ng/L 17α-TB treatments. Stage of development was increased among larvae in the 1 ng/L MGA + 10 ng/L 17α-TB treatment group and significantly decreased among those in the 500 ng/L 17α-TB treatment. Total body mass and snout–vent length of X. laevis larvae were significantly reduced in the 100 ng/L MGA and 100 ng/L MGA + 500 ng/L 17α-TB treatment groups. Larvae exposed to 500 ng/L 17α-TB had decreased total body mass, snout–vent length, and total length. In general, growth measurements decreased with increasing concentration of MGA, 17α-TB, or a combination of both. Survival among all treatments was not significantly different from controls. Amphibians exposed to MGA and 17α-TB in the environment may experience alterations in growth and development.