Chemical amendment of pig slurry: control of runoff related risks due to episodic rainfall events up to 48 h after application

Losses of phosphorus (P) from soil and slurry during episodic rainfall events can contribute to eutrophication of surface water. However, chemical amendments have the potential to decrease P and suspended solids (SS) losses from land application of slurry. Current legislation attempts to avoid losses to a water body by prohibiting slurry spreading when heavy rainfall is forecast within 48 h. Therefore, in some climatic regions, slurry spreading opportunities may be limited. The current study examined the impact of three time intervals (TIs; 12, 24 and 48 h) between pig slurry application and simulated rainfall with an intensity of 11.0?±?0.59 mm h^?1. Intact grassed soil samples, 1 m long, 0.225 m wide and 0.05 m deep, were placed in runoff boxes and pig slurry or amended pig slurry was applied to the soil surface. The amendments examined were: (1) commercial-grade liquid alum (8 % Al₂O₃) applied at a rate of 0.88:1 [Al/ total phosphorus (TP)], (2) commercial-grade liquid ferric chloride (38 % FeCl₃) applied at a rate of 0.89:1 [Fe/TP] and (3) commercial-grade liquid poly-aluminium chloride (10 % Al₂O₃) applied at a rate of 0.72:1 [Al/TP]. Results showed that an increased TI between slurry application and rainfall led to decreased P and SS losses in runoff, confirming that the prohibition of land-spreading slurry if heavy rain is forecast in the next 48 h is justified. Averaged over the three TIs, the addition of amendment reduced all types of P losses to concentrations significantly different (p?<?0.05) to those from unamended slurry, with no significant difference between treatments. Losses from amended slurry with a TI of 12 h were less than from unamended slurry with a TI of 48 h, indicating that chemical amendment of slurry may be more effective at ameliorating P loss in runoff than current TI-based legislation. Due to the high cost of amendments, their incorporation into existing management practices can only be justified on a targeted basis where inherent soil characteristics deem their usage suitable to receive amended slurry.     

Multiresidue analysis of organophosphate and pyrethroid pesticides in duplicate-diet solid food by pressurized liquid extraction

An analytical method was developed for determining organophosphate pesticides (OPP) and pyrethroid pesticides (PYR) in duplicate-diet solid food. The method consisted of pressurized liquid extraction (PLE) with dichloromethane followed by cleanup with gel permeation and solid phase extraction columns and gas chromatography/mass spectrometry (GC/MS) analysis. Quantitative recoveries (73–117 %) of the target pesticides were obtained for spiked duplicate-diet food samples. The percent standard deviation (% RSD) of replicate food samples was within ± 20 %. Another method was developed for determining a common OPP metabolite, 3, 5, 6-trichloro-2-pyridinol (TCP) in duplicate-diet food. The method consisted of a PLE with methanol followed by liquid-liquid partitioning, derivatization, and GC/MS analysis. Recoveries of TCP ranged from 83 to 101 % for spiked duplicate-diet food samples. The % RSD of replicate food samples was within ± 15 %. The results confirmed that these methods are reliable and robust, and that they can be used in routine analysis. In addition, a storage stability study for a common OPP, chlorpyrifos (CPF), in solid food samples was performed. The fortified ¹⁵N-¹³C-labeled CPF was stable over 16 mo storage at ?20° C in the dark. The developed analytical methods were successfully applied to 278 duplicate-diet food samples from preschool children, demonstrating that these methods are robust and suitable for routine analysis in future exposure monitoring studies.     

Competition, resources, and vegetation during 10 years in native grassland

A 10-year experiment tested for variation in competition intensity over time in a natural grassland at the northern edge of the Great Plains. Growing-season precipitation varied fivefold during the study. All ecosystem-level variables varied significantly among years, and most covaried in expected ways. The covers of all common grasses possessing the C3 photosynthetic pathway varied significantly among years; in contrast, all common species with traits associated with drought tolerance (a C4 grass, a lichen, a spikemoss, and a subshrub) did not vary. Annual transplant experiments measured the competitive effects of neighbors on the growth of individuals of the native grass Bouteloua gracilis. A significant interaction between year and competition showed that competition intensity varied among years. The size of this effect, however, was small (eta2 = 0.074) relative to the size of the direct effect of competition (eta2 = 0.20) or the year in which the experiment was conducted (eta2 = 0.51). Further, competition intensity was not significantly related to any variable describing standing crop or resources, or species richness. Species richness was highest in years with high precipitation, standing crop, and individual growth, due to the recruitment of rare species that were absent from dry years. In summary, variation in competition intensity was statistically significant but had small effects relative to the direct effects of climate.     

Safety in numbers and the spatial scaling of density-dependent mortality in a coral reef fish

In coral reef fishes, density-dependent population regulation is commonly mediated via predation on juveniles that have recently settled from the plankton. All else being equal, strong density-dependent mortality should select against the formation of high-density aggregations, yet the juveniles of many reef fishes aggregate. In light of this apparent contradiction, we hypothesized that the form and intensity of density dependence vary with the spatial scale of measurement. Individual groups might enjoy safety in numbers, but predators could still produce density-dependent mortality at larger spatial scales. We investigated this possibility using recently settled juvenile bluehead wrasse, Thalassoma bifasciatum, a small, aggregating reef fish. An initial caging experiment demonstrated that juvenile bluehead wrasse settlers suffer high predation, and spatial settlement patterns indicated that bluehead wrasse juveniles preferentially settle in groups, although they are also found singly. We then monitored the mortality of recently settled juveniles at two spatial scales: microsites, occupied by individual fish or groups of fish and separated by centimeters, and sites, consisting of approximately 2400-m2 areas of reef and separated by kilometers. At the microsite scale, we measured group size and effective population density independently and found that per capita mortality decreased with group size but was not related to density. At the larger spatial scale, however, per capita mortality increased with settler density. This shift in the form of density dependence with spatial scale could reconcile the existence of small-scale aggregative behavior typical of many reef fishes with the population-scale density dependence that is essential to population stability and persistence.     

Lip-reading in remote subjects: an attempt to quantify and separate ingestion, breathing and vocalisation in free-living animals using penguins as a model

A new mandibular sensor is presented here based on the use of a Hall sensor, attached to one mandible, opposite a magnet, attached to the other mandible. Changes in sensor voltage, proportional to magnetic field strength, and thus inter-mandibular angle, are recorded in a logger. This system was tested on seven captive Adélie penguins (Pygoscelis adeliae) and three gentoo penguins (Pygoscelis papua) during: (1) feeding trials on land, where birds were given known quantities and types of food; and (2) trials in water where birds were allowed to swim and dive freely. In addition, six free-living Magellanic penguins (Spheniscus magellanicus) were equipped with the system for single foraging trips. Angular signatures were looked for in instances when both captive and free-living birds might open their beaks, and it was discovered that five major behaviours could be identified: ingestion, breathing, calling, head shaking and preening. Captive feeding trials showed that prey mass could be determined with reasonable accuracy (r²=0.92), and there was some indication that prey type could be resolved if recording frequency were high enough. Vocalisations in Adélie penguins (arc calls) took <0.7 s for mean maximum beak angles of 4.2° (SD 1.3), and were distinguished by their relatively gradual change in beak angle and by their high degree of symmetry. Beak shakings were distinguishable by their short duration (multiple peaks of <0.5 s) and minimal maximum angle (<0.5°). Preening behaviour was apparent due to multiple decreasing peaks (angles <8°). Breathing could be subdivided into that during porpoising, where a characteristic double peak in beak angle was recorded, and that during normal surface rests between dives. During porpoising, only the primary peak (mean maximum beak angle 25.1°, SD 4.7) occurred when the bird was out of the water (mean maximum for second peak 5.9°, SD 4.1). During normal surface rests in free-living birds, breaths could be distinguished as a series of beak openings and closures, showing variation in amplitude and frequency according to an apparent recovery from the previous dive and preparation for the subsequent dive to come. The mandibular measuring system presented shows considerable promise for elucidating many hitherto intractable aspects of the behaviour of free-living animals.